Asphalt Plant Certification Study Guide

Transcription

1 Asphalt Plant Certification Study Guide

2 Introduction Page intentionally left blank. Page 2 Chapter 1 VDOT and Platinum Performance Partners, LLC

3 Introduction Asphalt Plant Certification Study Guide Prepared by: The Virginia Department of Transportation Materials Division 2012 VDOT and Platinum Performance Partners, LLC Chapter 1 Page 3

4 Introduction Table of Contents Chapter 1: Introduction Acknowledgements Preface Audience Asphalt Plant Certification Information About this Guide History and Introduction to Asphalt Chapter 2: Project Communication and Safety Project Communication Project Documents Types of Communication Project Safety Chapter 3: Components and Characteristics of Asphalt Concrete Learning Objectives Ingredients in Asphalt Concrete Characteristics and Properties of Asphalt Cement Consistency Purity Durability Adhesion and Cohesion Temperature Susceptibility Aging and Hardening Safety Characteristics and Properties of Liquid Asphalt Cutback Asphalt Emulsified Asphalts Testing of PG Binders and Liquid Asphalts PG Binder Testing Liquid Asphalt Testing Aggregates Sources of Aggregates Page 4 Chapter 1 VDOT and Platinum Performance Partners, LLC

5 Introduction Evaluating Consensus Properties of Aggregates Aggregate Storages Chapter Three Knowledge Check Chapter 4: Asphalt Concrete Mixtures Learning Objectives Physical Properties Required of Asphalt Concrete Mixtures Stability Durability Impermeability Workability Flexibility Fatigue Resistance Skid Resistance Mixture Types Used in Virginia Surface Mixes Intermediate Mixes Base Mixes Chapter Four Knowledge Check Chapter 5: Asphalt Concrete Plants Learning Objectives Batch Plant Batch Plant Operation and Components Drum Plant Drum Plant Operation and Components Special Procedures The Ross Count Procedure for Establishing Batch Mixing Times Aggregate Moisture Determination for Drum Mix Operations Types of Trouble and the Plant and Probable Causes Chapter Five Knowledge Check VDOT and Platinum Performance Partners, LLC Chapter 1 Page 5

6 Introduction Chapter 6: Sampling and Analysis of Aggregate Learning Objectives Sampling Aggregates Getting a Representative Sample An Overview of Sieve Analysis How to Conduct Sieve Analysis Test Sample Size for Fine and Coarse Aggregate Consensus Property Testing Superpave Aggregate Characteristics and Test Methods Chapter Six Knowledge Check Chapter 7: Blending Aggregates Learning Objectives Mix Design The Job Mix Formula Combining Aggregates to Achieve the Target Blend Sample Problems Proportioning Aggregate at the Batch Plant Hot Bin Proportions by the Trial and Error Method Calculating Batch Weights Chapter Seven Knowledge Check Chapter 8: Duties of the Technicians Learning Objectives An Overview of Roles and Responsibilities Contractor s Responsibility The Asphalt Mix Design and Plant Technicians The Weighperson VDOT s Responsibility Chapter Eight Knowledge Check Page 6 Chapter 1 VDOT and Platinum Performance Partners, LLC

7 Introduction Chapter 9: Testing of Asphalt Concrete Mixtures Learning Objectives Overview Physical Characteristics to be Determined by Testing Asphalt Binder Content Aggregate Gradation Voids in the Total Mixture (VTM) Voids in the Mineral Aggregate (VMA) Voids Filled with Asphalt (VFA) Fines to Asphalt Ratio Tensile Strength Ratio (TSR) Testing Procedures Procedure for Determining Asphalt Content (Percent Binder) Ignition Method Procedure for Compacting Specimen Procedure for Determining Bulk Specific Gravity Procedure for Determining Maximum Specific Gravity Procedure for Determining Tensile Strength Ratio Procedure for Conducting the Boil Test Calculating Volumetric Properties Example Volumetric Calculations Volumetric Properties Worksheets and Formulas Volumetric Worksheets Volumetric Properties Formulas Chapter Nine Knowledge Check Chapter 10: Quality Acceptance & Data Processing Learning Objectives Acceptance through Quality Assurance QA Specifications Acceptance Acceptance Calculations for Gradation and Asphalt Content Calculating the Acceptance or Failure for Gradation and Asphalt Content Adjustment System Adjustment Conditions and Actions Calculating Adjustments on Material Failing Gradation and Asphalt Content Standard Deviation (Calculation of Variability) VDOT and Platinum Performance Partners, LLC Chapter 1 Page 7

8 Introduction Computing Standard Deviations Automated Data Processing for Asphalt Concrete Completing Form TL-100A The Asphalt Test Results Input Form Specification Reference Tables Chapter Ten Knowledge Check Appendices A: Glossary of Terms and Definitions... A-1 B: Materials Specifications... B-1 C: Tests and Procedures... C-1 D: Lime Safety Precautions... D-1 E: Proficiency Tests... E-1 F: Study Questions and Answers... F-1 Page 8 Chapter 1 VDOT and Platinum Performance Partners, LLC

9 Introduction 1 Introduction An overview of the Asphalt Plant Certification Guide is explained and along with key terms and icons. Sections of the Introduction Include: Acknowledgements Preface Audience Asphalt Plant Certification Information About this Guide VDOT and Platinum Performance Partners, LLC Chapter 1 Page 9

10 Introduction Acknowledgements The writers of this Guide would like to express their appreciation to the Asphalt Institute for their permission to use quotations, graphs, and illustrations from the Asphalt Technology and Construction Guide and the Virginia Asphalt Association, Inc., for technical data and slides used in the schools. The writers are also grateful for to the Barber-Green Company and the Iowa Manufacturing Company for the use of their illustrations and information. Appreciation is extended to The National Lime Association for their permission to use quotations on Lime Safety from the Lime Stabilization Construction Manual, Bulletin 326. The Certification School personnel would also like to express their gratitude to everyone in the Department who gave of their time and talents in the preparation of this manual. Other references used in the preparation of this guide are listed below. American Association of State Highway and Transportation Officials (AASHTO). Asphalt Institute. Transportation Research Board (TRB). (2000). Hot-Mix Asphalt Paving Handbook Transportation Research Board, National Research Council. Washington, D.C. Virginia Road and Bridge Specifications. Virginia Road and Bridge Standards Buttlar, W.G. and Harrell, M. (1998). Development of End-Result and Performance-Related Specifications for Asphalt Pavement Construction in Illinois. Transportation Conference Proceedings, pp Muench, S. HMA Drum Plant 15 August Muench, S. HMA Batch Plant 15 August Muench, S. (2003). Figure 1-Flexible Pavement Structure. HMA Pavement 29 December Roberts, F.L., Kandhal, P.S., Brown, E.R., Lee, D.Y., and Kennedy, T.W. (1996). Hot Mix Asphalt Materials, Mixture Design, and Construction. National Asphalt Pavement Association Research and Education Foundation. Lanham, MD. Page 10 Chapter 1 VDOT and Platinum Performance Partners, LLC

11 Introduction AWARENESS/IMPORTANT This manual is a practical guide and not to be used as a source for VDOT specifications. Highlights a step in the procedure which is either unusual or very particular to this procedure. May also indicate awareness (additional information) or a cautionary concern in the procedure. VDOT and Platinum Performance Partners, LLC Chapter 1 Page 11

12 Introduction Preface This Guide covers asphalt components and properties, mixtures, plants and production, common problems, technician duties and testing/quality assurance processes. The Guide and the course it accompanies will provide each technician with an understanding of his/her role in the overall pavement performance and a working knowledge of the techniques and processes used to safely select, mix, produce, and test asphalt to specifications. Likewise, course attendees will have an understanding of improper preparation of materials, their adverse effect, and ultimately the behavior and resulting problem in the finished product. As asphalt plant experts, we understand that equipping the technician with this information will give him/her the confidence to make proper day-to-day decisions and will ensure that good quality control is maintained throughout, to the end product. We hope this Guide will promote a common understanding of the processes involved and thereby result in improved asphalt-concrete production. Audience The Guide s audience is the plant personnel who are responsible for asphalt plant operations and processes both contractor personnel who do the work, and agency personnel who oversee and inspect the work. The program has been designed to enable the job roles in Figure 1-1 to achieve specific outcomes and certifications. A technician may be certified as any one or more of these, or possibly all of these. Some certifications require a lower level certification before advancement to the next level of certification. Job Role VDOT Personnel Asphalt Plant Technician Asphalt Laboratory Technician QA Manager Outcome Through inspection processes, ensure asphalt production facilities are capable of producing the level of quality product required for specifications of the VDOT job while being compliant with CFR 637. Ensures that quality assurance (QA) testing on the asphalt components and products meet specifications of VDOT job and supports compliance measures with CFR 637. Management and supervision of the two previous job roles to ensure their outcomes are produced Certification Level Level I Level II Level I Level I Level II Page 12 Chapter 1 VDOT and Platinum Performance Partners, LLC

13 Industry Personnel Mix Design Technician Plant Technician Plant Operator Loader Operator QC Manager consistently over time, and without error. Quality mixes that are designed and produced at plant to meet VDOT contract specifications and CFR 637 requirements. Ensures the quality of the materials produced in the plant meet mix design requirements for VDOT job and are compliant with CFR 637. Oversees and ensures that plant operations meet the mix designs to VDOT contract specifications and CRF 637 requirements. Ensures components of the job mix are introduced properly into the mix. Ensures that the outcomes of the previous four (Industry) jobs consistently meet or exceed the customer (VDOT) requirements, while being compliant with CFR 637. Level I Introduction Level II Level I No VDOT Certification Required No VDOT Certification Required No VDOT Certification Required Figure 1-1. Outcome and Certification Level by Job Role VDOT and Platinum Performance Partners, LLC Chapter 1 Page 13

14 Introduction Asphalt Plant Certification Information Listed in Figure 1-2 are the different certifications related to asphalt-concrete production (Plant Level I, Plant Level II), a brief statement of course coverage, the certification components or requirements related to each level, and the course prerequisites related to each course. Please note: A technician may be certified as any one or more of these, or possibly all of these. Some certifications require prerequisite certification before advancement to the next level. Certification & Course Plant Level I Course Coverage: Awareness of VDOT Asphalt Specifications and Test Methods Plant Level II Course Coverage: Asphalt Mixture Design and Production Control Certification Components Written Exam Before taking the exam you must show photo identification and sign the Technician Certification Application. You are allowed 3 hours to complete the exam. You must pass with a minimum score of 70% and have one opportunity for re-testing. Passing written exam score results in an Asphalt Field Level I Certification. Proficiency Exam Before taking the exam you must show photo identification. You have one opportunity for re-testing. Passing the written and proficiency exam results in an Asphalt Plant Level I Certification. Written Exam Before taking the exam you must show photo identification and sign the Technician Certification Application. You are allowed 3 hours to complete the exam. You must pass with a minimum score of 70% and have one opportunity for re-testing. Proficiency Exam Before taking the exam you must show photo identification. You have one opportunity for re-testing. Passing the written and proficiency exam results in an Asphalt Plant Level II Certification. Prerequisites for Courses No Pre-Req. Plant Level I Figure 1-2. Certifications and Pre-Requisites related to Asphalt-Concrete, Plant Production Page 14 Chapter 1 VDOT and Platinum Performance Partners, LLC

15 Introduction Upon satisfactory completion of all requirements, the technician will be issued a certificate/certification. A certificate will be issued for each type certification. Initial certification will generally be effective for five (5) years beginning from the date of passing the appropriate written exam. Failure of an exam will require the person to re-attend the regular class and pass the exam to become certified/re-certified. TEST RESULTS Your test results and card may be found at the VDOT University website listed below. VDOT employees: All other students: If you are enrolled in this class or hold any VDOT Materials certifications, do not register as a new user when you go to this site. If you do not know your logon or password, call (804) VDOT and Platinum Performance Partners, LLC Chapter 1 Page 15

16 Introduction About This Guide This Guide was designed using several techniques to improve learning and retention. Each chapter begins with a brief introduction and a listing of learning objectives related to the chapter. Please review these objectives before beginning the chapter. This will help you develop a mental context and a set of expectations for chapter content, preparing you for more effective learning. Within the chapters you will find a variety of techniques being used to improve learning, depending on the chapter content and type of information being conveyed. Some of these include: Step-by-step procedures and photos directing how to activity Decision tables for if-then situations Graphics to provide context and additional information Step-by-step examples for completing sample problems Worksheets to guide procedural calculations and a reference section of formulas used in calculations (Chapter 10). Chapters 3 through 10 each conclude with a Knowledge Check section of study questions intended to prepare you for the certification exam. Answers to these Knowledge Checks are included in Appendix F, enabling you to check your learning. This Guide also uses various visual cues to symbolize several consistent concepts throughout the chapters. These are highlighted because they contain foundational knowledge or other information that is critical for you to understand. Below and on the next page you will see the visual cues used, as well as a description of each. DEFINITION A definition will be provided. Highlights a step in the procedure which is either unusual or very particular to this procedure. May also indicate awareness (additional information) or a cautionary concern in the procedure. TOOLS AND EQUIPMENT Describes what tools, equipment and tests are required to complete the job safely and with the highest level of quality. Describes what tools, equipment and tests are required to complete the job safely and with the highest level of quality. Page 16 Chapter 1 VDOT and Platinum Performance Partners, LLC

17 Introduction BEST PRACTICE Describes a best practice to be utilized when possible. Highlights a step in the procedure which is either unusual or very particular to this procedure. May also indicate awareness (additional information) or a cautionary concern in the procedure. PROCEDURE Describes a condition where equipment and procedure integrity is at risk. This is used to alert personnel to operating procedures and practices, which if not observed, could result in severe damage to the machine, its components or the end product. Highlights a step in the procedure which is either unusual or very particular to this procedure. May also indicate awareness (additional information) or a cautionary concern in the procedure. AWARENESS/IMPORTANT Highlights a step in the procedure which is either unusual or very particular to this procedure. May also indicate awareness (additional information) or a cautionary concern in the procedure. INSPECTION AND MEASUREMENTS Highlights a step in the procedure which is either unusual or very particular to this procedure. May also indicate awareness (additional information) or a cautionary concern in the procedure. Describes inspection, Quality Assurance and/or Quality Control practices. SAFETY WARNING Highlights a step in the procedure which is either unusual or very particular to this procedure. May also indicate awareness (additional information) or a cautionary concern in the procedure. Describes a condition where personal safety may be at risk. This is used to alert personnel to operating procedures and practices which, if not observed, may result in personal injury. Highlights a step in the procedure which is either unusual or very particular to this procedure. May also indicate awareness (additional information) or a cautionary concern in the procedure. VDOT and Platinum Performance Partners, LLC Chapter 1 Page 17

18 Introduction History and Introduction to Asphalt The modern use of asphalt for road and street construction began in the late 1800s, and grew rapidly with the emerging automobile industry. Since that time, asphalt technology has made giant strides. Today, the equipment and techniques used to build asphalt pavement structures are highly sophisticated. One rule that has remained constant throughout asphalt's long history in construction is that an asphalt concrete layer is only as good as the materials and workmanship that go into it. No amount of sophisticated equipment can make up for use of poor quality materials, poor sampling and testing techniques and/or poor production practices. Asphalt concrete is composed of three basic components asphalt binder, mineral aggregate and air voids. Aggregates are generally classified into two groups (1) coarse and (2) fine; together they normally constitute 90 to 95 percent by weight of the total mixture. Asphalt binders are classified by various grading systems and normally constitute 5 to 10 percent of the total mixture. Another very important, but often overlooked component of an asphalt mix is air voids. There are many different types of asphalts and many different types of aggregates. Consequently, it is possible to make different kinds of asphalt concrete. Among the most common types of asphalt concretes are: Dense-graded hot mix asphalt (Superpave Mixtures) Gap Graded hot mix asphalt (Stone Matrix Asphalt or SMA) Open-graded asphalt or porous friction course Ultra-Thin Bonded Wearing Course Asphalt Surface Treatments Emulsified asphalt mixes (cold mixes) Permeable Asphalt Drainage Course Others, In-Place Recycled Mixes (both hot and cold) This course primarily addresses asphalt-concrete (AC) produced at conventional plant temperatures or through a warm mix technology. AC is a paving material that consists of asphalt binder and mineral aggregate with appropriate air voids. The asphalt binder, either asphalt cement or a modified asphaltcement, acts as a binding agent to glue aggregate particles into a dense mass and to waterproof the mixture. When bound together, the mineral aggregate acts as a stone framework to impart strength and toughness to the system. The performance of the mixture is affected both by the properties of the individual components and the combined reaction in the system. Page 18 Chapter 1 VDOT and Platinum Performance Partners, LLC

19 MCS: Asphalt Plant Certification 2 Project Communication and Safety Put effective project communication and safety practices in place to help ensure that your project is successful and safe. Learning Objectives: Upon completion on this chapter, you should be able to: Describe the purpose of project documentation Describe the various types of recommended project communications Describe the role of communication as a tool to improve safety at a hot mix asphalt plant List things that can be done to improve plant safety VDOT and Platinum Performance Partners, LLC Chapter 2 page 1

20 Project Communication and Safety Project Communication The most essential part of project planning and organization is communication. Effective communication is vital to all elements of project organization: The project documents are written instructions that must describe the requirements clearly and in detail. The preconstruction conference initiates verbal communication between the representatives of the agency and contractor personnel; it sets the tone for both the working relationship and direct communications during project execution. Ongoing project communications between the Department, contractors, and contractor personnel to ensure projects yield high-quality work. Project records make it possible to track events should doing so become necessary. Safety on the job cannot be maintained if communication between parties is inadequate. Project Documents Project documents illustrate and describe work to be done under the contract. Project documents include: Plans Drawings that show the location, character, dimensions, and details of the work to be done. Standard Drawings Are used by the owner for common structures encountered in projects, i.e. drop inlets, guard rail and rumble strips encountered in most paving projects. Unless otherwise specified, applicable drawings in the Department s Road and Bridge Standards and such other standard drawings as are referred to on the plans. Standard Specifications Directions, provisions, and requirements for performing the work illustrated and described in the plans. The items in the standard specifications relate to or illustrate the method and manner of performing the work or describe the qualities and quantities of materials and labor to be furnished under the contract. The Department s Road and Bridge Specifications are the standard specifications for VDOT projects. page 2 Chapter 2 VDOT and Platinum Performance Partners, LLC

21 Project Communication and Safety Special or Supplemental Specifications Approved additions and revisions to the standard specifications. Special Provisions A document that sets forth specifications or requirements for a particular project that is not covered by the standard Specification. Special Provision Copied Note A document that sets forth specific specifications or requirements usually limited in scope, for a particular project. If there is a discrepancy between the instructions and specifications in any of the contract documents, a definite hierarchy exists among the above major types of documents. The order of priority as defined by VDOT s Road and Bridge Specifications, from highest to lowest is: Special provision copied note Special provisions Plans Supplemental specifications Standard specifications Standard drawings This order of priority corresponds to the specific applicability of the document to a project or contract. AWARENESS/IMPORTANT Make sure you are aware of the VDOT Strategic Plan, Agency Values and their Safety KPI metrics per year when building your plan. Highlights a step in the procedure which is either unusual or very particular to this procedure. May also indicate awareness (additional information) or a cautionary concern in the procedure. Plans and specifications need to be accurate and complete and should leave little room for assumptions or later reinterpretation. In addition, plans and specifications need to define the responsibilities of both the Department and the contractor. VDOT and Platinum Performance Partners, LLC Chapter 2 page 3

22 Project Communication and Safety Types of Communication The quality of the work completed and the safety of those performing and inspecting the construction are directly related to the quality of the communication between the Department and the contractor. It is important that the individuals in daily charge of the project for both the Department and the contractor meet periodically, on both a formal and an informal basis, to discuss the progress and quality of the work done to date and the schedule for future work. The table that follows highlights types of communication that should be employed. Preconstruction Conference The preconstruction conference should be held before work on a project begins. The meeting should bring agreement on the proposed schedule, methods to be used to complete the project on schedule with a minimum of delays and change orders, material sources, plant production rates, etc. Additionally, the role of each person associated with the project should be discussed and clarified. One of the most important items to be addressed at the preconstruction conference is job safety. One technique is to ask each person to discuss ways they can keep their activities at the plant safe for others and work out a plan that is effective for everyone. Formal Meetings Key personnel from both the Department and the contractor should be present at these meetings. The meetings should discuss: the quantity of work completed, test results obtained, what has yet to be accomplished, the schedule for the coming weeks, and changes in personnel, equipment, construction methods used and mix design. Written minutes, including a list of those in attendance, should be completed and distributed as quickly as possible. page 4 Chapter 2 VDOT and Platinum Performance Partners, LLC

23 Project Communication and Safety Informal Meetings and Information Sharing Daily informal meetings at the asphalt plant provide a forum for the exchange of information. The purpose of informal meetings is twofold. First, occurrences the day before such as work completed, test results, and any problem areas, should be discussed and resolved. Second, the discussion should address what is expected to happen during the next several days an update on the information exchanged at the last formal meeting. In addition, other tools and techniques can be used to share information and improve safety. For example, a common CB radio in the loader and one in each of the trucks can help eliminate conflict. Another technique is to keep a daily plant log or diary to share any potential problems or conditions with each other. Written Communication Much information can be communicated in oral form, but discussion of important information should be followed up in written form, particularly when conditions on the project change substantially. If an occurrence is important enough to be remembered later on, it is important enough to be written down immediately after it happens so the information will be accurate and complete. VDOT and Platinum Performance Partners, LLC Chapter 2 page 5

24 Project Communication and Safety Project Safety Numerous dangers exist around an asphalt plant. Electrical shock injury is all too common, as are injuries from falls, accidents, and burns from hot asphalt. Communication is a key safety issue at any hot mix asphalt facility. Develop and distribute clear-cut guidelines dealing with your organization s policy on safety. Every individual involved in the project should know what is expected and how to perform the assigned tasks. Proper training in the operation of a piece of equipment is essential for its operators, for example. Retraining is necessary at frequent intervals because the longer a person continues to perform the same task, day after day, the more likely he or she is to do things by habit and ignore surrounding events. In addition, all personnel must be aware of OSHA guidelines, including the wearing of hard hats, safety glasses, and gloves. Safety talks are a good way to start the day. People need to be reminded that they are operating in a potentially dangerous environment, and daily talks are one way of meeting this need. Further, if an unsafe work practice is noticed, corrective action should be taken immediately. Don t let production issues result in a disregard for safety. Throughout the guide, we have highlighted safety practices and warnings that relate to the topic or process mentioned, using the icon symbol shown below. SAFETY WARNING Describes a condition where personal safety may be at risk. This is used to alert personnel to operating procedures and practices which, if not observed, may result in personal injury. This is used to alert personnel to operating procedures & practices which, if not observed, may result in personal injury. page 6 Chapter 2 VDOT and Platinum Performance Partners, LLC

25 MCS: Asphalt Plant Certification 3 Components and Characteristics of Asphalt Concrete Asphalt concrete is a composite material used in construction projects such as road surfaces, airports and parking lots. It consists of two components: Asphalt Composed of a Performance Graded (PG) binder or a variation, it constitutes 5 to 10% of the total asphalt concrete mixture by weight. Aggregates An inert granular material such as sand, gravel, shell, slag, or broken stone, generally classified into two groups (fine and coarse), constituting 90 to 95% of the total asphalt concrete mixture by weight. This section of the guide covers the materials used in quality hot mix asphalt (HMA) pavements what they are, how they behave and how to tell whether or not particular materials are suitable for a paving project. Learning Objectives: Upon completion of this chapter, you should be able to: List the ingredients in asphalt concrete Describe the performance properties of binders Identify tests for binders and liquid asphalts Define sources for and evaluation of aggregates VDOT and Platinum Performance Partners, LLC Chapter 3 page 1

26 Components of Asphalt Concrete Ingredients in Asphalt Concrete DEFINITIONS. The following terms will be used throughout this section: Asphalt Aggregate Asphalt concrete Asphalt cement Performance Graded Binder (PG Binder) Thermoplastic material Composed of a Performance Graded (PG) binder or a variation, it constitutes 5 to 10% of the total asphalt concrete mixture by weight. An inert granular material such as sand, gravel, shell, slag, or broken stone, which generally constitutes 90 to 95% of the total asphalt concrete mixture by weight. A composite materials consisting of two components: aggregates and asphalts. Petroleum asphalt for use in pavements is called asphalt cement or paving asphalt. At ambient temperatures, it is a black, sticky, semisolid, highly temperaturedependent visco-elastic material. The PG Binder system was developed by the AASHTO as way to evaluate asphalt cements for use in pavements based on project specific performance criteria. A plastic that softens when heated and hardens when cooled without changing its engineering properties. Practically all asphalt used in the U.S. is produced by modern oil refineries like the one shown in Figure 3-1, and is called petroleum asphalt. Petroleum asphalt that is used in pavements is usually called paving asphalt or asphalt cement to distinguish it from asphalt made for non-paving uses. Figure 3-1. Oil Refinery page 2 Chapter 3 VDOT and Platinum Performance Partners, LLC

27 Components of Asphalt Concrete Asphalt, a by-product of processing liquid petroleum, is isolated through the refining process, which is illustrated in Figure 3-2. Crude petroleum from oil wells is separated into its fractions in a refinery by a process called distillation. Figure 3-2. Petroleum Refinement Process During this process, crude petroleum is fed into a tube still, where its temperature is quickly raised for initial distillation. It then enters a fractionating tower where the lighter or more volatile fractions vaporize and are drawn off for further refining. Residue from this fractionating process is the heavy component of crude petroleum, which includes asphalt. Further refinement is necessary to produce asphalt cement, which is also known as Performance Graded (PG) binder. VDOT and Platinum Performance Partners, LLC Chapter 3 page 3

28 Components of Asphalt Concrete Characteristics and Properties of Asphalt Cement Asphalt cement is composed primarily of complex hydrocarbon molecules. Because asphalt cement is sticky, it adheres to aggregate particles (e.g., sand, gravel, crushed stone, blast-furnace slag, lightweight aggregate) and can be used to cement or bind them in asphalt concrete. Asphalt cement is unaffected by most acids, alkalis, and salts. It is a thermoplastic material because it softens as it is heated and hardens as it is cooled. This unique combination of characteristics is a fundamental reason why asphalt is an important paving material. Virginia has adopted the Performance Graded Binder system for asphalt cements used in VDOT mixes. The Performance Graded system is a method of measuring asphalt binder performance. Performance grading is based on the idea that asphalt binder properties should be related to the conditions under which it is used. Performance graded asphalt binders are selected to meet expected climatic conditions, traffic loading, as well as aging considerations, with a certain level of reliability. Asphalt binders are most commonly characterized by their physical properties. An asphalt binder s physical properties directly describe how it will perform as a constituent in asphalt concrete pavement. Asphalt binders are characterized by their properties at different temperatures and stages of life simulated by laboratory aging. Binder properties include the following: Consistency Purity Durability Adhesion and Cohesion Temperature Susceptibility Aging and Hardening Safety Each of these is described in more detail in the text that follows. page 4 Chapter 3 VDOT and Platinum Performance Partners, LLC

29 Components of Asphalt Concrete DEFINITION DEFINTIONS. The following terms will be used throughout this section: Consistency Durability Purity Adhesion Cohesion Temperature susceptibility Viscosity Thin binder film Flash point The degree of fluidity or plasticity of the binder at any particular temperature. The binder s resistance to the effects of traffic, water, air and temperature changes. The degree to which the binder is pure (i.e., free from impediments such as moisture). The binder s ability to stick to the aggregate in the paving mixture. The binder s ability to hold the aggregate particles in place in the finished pavement. The effect of temperature on a binder s viscosity and elasticity. A measure of a liquid s resistance to flow. The film coating aggregate particles. The temperature at which asphalt will instantaneously flash in the presence of an open flame. Consistency Consistency is the degree of fluidity or plasticity of binders at any particular temperature. The consistency of binders varies with temperature. Binders are graded based on standard consistency at the design temperature for the project. When the binder is exposed to air in thin films and is subjected to prolonged heating (e.g., during mixing with aggregates), the binder tends to harden. This means that the consistency or viscosity of the binder has increased for any given temperature. A limited increase is allowable. AWARENESS/IMPORTANT Careless or missing temperature control can cause more damage to the binder, through hardening, than many years of service on the finished roadway. Highlights a step in the procedure which is either unusual or very particular to this procedure. May also indicate awareness (additional information) or a cautionary concern in the procedure. VDOT and Platinum Performance Partners, LLC Chapter 3 page 5

30 Components of Asphalt Concrete Purity Purity is a determination of the degree to which the binder is pure, or free from impediments such as moisture. Asphalt cement used for paving should consist of almost pure bitumen, which by definition is soluble in carbon disulfide. Refined binders are almost pure bitumen and are usually more than 99.5% soluble in carbon disulfide. Impurities, if present, are inert. Normally, the binder is free of water or moisture as it leaves the refinery. SAFETY WARNING Tank transports loading binder may have some moisture present in their tanks. If any water is inadvertently present in the binder, it may cause the binder to foam when it is heated above 212 F (100 C). Describes a condition where personal safety may be at risk. This is used to alert personnel to operating procedures & practices which, if not observed, may result in personal injury. Durability Durability is the binder s resistance to the effects of traffic, water, air and temperature changes. It is a measure of how the asphalt binder s physical properties change with the normal weathering and aging (sometimes called age hardening) processes. Some qualities that complement a binder s durability are its resistance to swelling, stripping, oxidation and wear or abrasion. In general, as a binder ages, its viscosity increases and it becomes more stiff and brittle. The performance grading of current binders includes laboratory tests that simulate the weathering and aging processes and establishes pass/fail limits on the test results. AWARENESS/IMPORTANT Pavement performance is greatly affected by variables including: Mix design Aggregate characteristics Highlights a step in the procedure which is either unusual or very particular to this procedure. May also indicate awareness (additional information) or a cautionary concern in the procedure. page 6 Chapter 3 VDOT and Platinum Performance Partners, LLC

31 Components of Asphalt Concrete Adhesion and Cohesion Adhesion and cohesion are two important and related properties of asphalt binders that can affect asphalt mixture performance. Adhesion is the binder s ability to stick to the aggregate in the paving mixture. Cohesion is the binder s ability to hold the aggregate particles in place in the finished pavement. The adhesive and cohesive properties of asphalts determine how well roads hold up to traffic, weather and other forces working against their integrity. Temperature Susceptibility Temperature susceptibility refers to the effect of temperature on the binder. All binders are thermoplastic; that is, they become harder (i.e., more viscous) as their temperature decreases and softer (i.e., less viscous) as their temperature increases. This characteristic is known as temperature susceptibility, and is one of a binder s most valuable assets. Temperature susceptibility is an important control parameter during the mixing, placement, compaction and performance of asphalt concrete. Figure 3-3 illustrates this point, showing the variation in viscosity of a binder at different temperatures. As the temperature increases, the binder becomes less viscous (i.e., more fluid). Figure 3-3. Temperature Susceptibility It is vitally important for a binder to be temperature susceptible. It must be fluid enough at elevated temperatures to permit it to coat the aggregate particles during mixing and to allow these particles to move past each other during compaction. It must then be viscous enough at normal air temperatures to hold the aggregate particles in place in the pavement. VDOT and Platinum Performance Partners, LLC Chapter 3 page 7

32 Components of Asphalt Concrete AWARENESS/IMPORTANT Temperature susceptibility varies among binders from different petroleum sources, even if the binders are of identical grade. Knowing the temperature susceptibility of the binder being used in a paving mixture is important because it indicates the proper temperature at which to mix the binder with the aggregates and the proper temperature at which to compact the mixture on the roadbed. Highlights a step in the procedure which is either unusual or very particular to this procedure. May also indicate awareness (additional information) or a cautionary concern in the procedure. Aging and Hardening Binders harden in the paving mixture during construction and over time in the pavement itself. This hardening is caused primarily by oxidation (i.e., the binder combining with oxygen), a process that occurs most readily at higher temperatures (e.g., mixing temperature) and in thin binder films (i.e., the film coating aggregate particles). Mixing is the stage at which the most severe oxidation and hardening usually occur. During mixing, the binder is both at a high temperature and in thin films as it coats the aggregate particles. Figure 3-4 shows the increase in viscosity caused by heating a thin film of a binder. Note: The viscosity range of the original material before the Rolling Thin Film Oven (RTFO) test is significantly lower than after the test. Figure 3-4. Hardening of Binder after Exposure to High Temperatures The hardening of a binder continues in the pavement after construction. This is caused primarily by oxidation and polymerization. These processes can be retarded by keeping the number of connected voids (air spaces) in the final pavement low and the binder coating on the aggregate particles thick. page 8 Chapter 3 VDOT and Platinum Performance Partners, LLC

33 Components of Asphalt Concrete AWARENESS/IMPORTANT Not all binders harden at the same rate when heated in thin films. Each binder used should be tested to determine its aging characteristics so that construction techniques can be adjusted to minimize hardening. Such adjustments usually involve mixing the binder with the aggregate at the lowest possible temperature for the shortest practical time. Highlights a step in the procedure which is either unusual or very particular to this procedure. May also indicate awareness (additional information) or a cautionary concern in the procedure. Safety Binder (asphalt) can be a safety hazard. Binders, if heated to a high enough temperature, will flash in the presence of a spark or open flame. The temperature at which this occurs is called the flash point. Specifications usually require that asphalt not flash below 446 F (230 C). SAFETY WARNING The temperature at which binder flash occurs is well above the temperatures normally used in paving operations. However, to be sure there is an adequate margin of safety and that no contamination with flammable distillates (e.g., diesel, kerosene, naphtha), the flash point of the binder should be known and monitored. Describes a condition where personal safety may be at risk. This is used to alert personnel to operating procedures & practices which, if not observed, may result in personal injury. VDOT and Platinum Performance Partners, LLC Chapter 3 page 9

34 Components of Asphalt Concrete Characteristics and Properties of Liquid Asphalt Cutback asphalt and emulsified asphalts are called liquid asphalts to distinguish them as a group from normal binders. Liquid asphalt is asphalt cement which has been liquefied with petroleum solvents or emulsified, such that they flow readily at ambient to relatively low production temps (below 175F). The specifications for liquid asphalts (cutbacks and emulsions) are described in Section 210 of the current Road and Bridge Specifications. DEFINITION DEFINITIONS. The following terms will be used throughout this section: Cutting back Cutback asphalt Emulsified asphalt Liquid asphalt Percent residue Anionic Cationic Slurry The process of dissolving a binder in selected solvents. Asphalt cement which has been liquefied by blending it with petroleum solvent. There are three types: Rapid-Curing (asphalt and a volatile solvent or light distillate), Medium-Curing (asphalt and a solvent of intermediate volatility or medium distillate) and Slow-Curing (asphalt and an oily diluent of low volatility). A suspension of asphalt in water containing an emulsifying agent, such as soap. Asphalt cement which has been liquefied with petroleum solvents or emulsified. The amount of asphalt cement in a liquid asphalt solution. Binder globules are electro-negatively charged. Binder globules are electro-positively charged. A mixture of aggregate, asphalt emulsion, filler, and water, which are mixed together according to a laboratory's design-mix formula. A binder, which at normal atmospheric temperatures is semisolid and highly viscous, must be temporarily melted or liquefied for handling during construction operations. The binder can be temporarily liquefied for construction operations in three ways: 1. Melting it with heat. 2. Dissolving the binder in selected solvents. This process is called cutting back and the resultant diluted binder is called cutback asphalt. 3. Emulsifying the binder with water. The resulting product is called emulsified asphalt. It is important to note that, in each case, the binder is the base material that has been liquefied by cutting back or emulsifying. page 10 Chapter 3 VDOT and Platinum Performance Partners, LLC

35 Components of Asphalt Concrete Cutback Asphalt Petroleum solvents used for dissolving binders are sometimes called distillates, diluents or cutter stocks. If the solvent used in making the cutback asphalt is highly volatile, it will quickly escape by evaporation. Solvents of lower volatility evaporate more slowly. On the basis of relative speed of evaporation, cutback asphalts are divided into three types, as illustrated in Figure 3-5: 1. Rapid-Curing (RC) Asphalt and a volatile solvent or light distillate, generally in the gasoline or naphtha boiling point range 2. Medium-Curing (MC) Asphalt and a solvent of intermediate volatility or medium distillate, generally in the kerosene boiling point range 3. Slow-Curing (SC) Asphalt and an oily diluent of low volatility. Slow-curing (SC) asphalts are often called road-oils (a term that originated in earlier days). Currently, SC asphalts are not used in Virginia. Gasoline or Naphtha Rapid Curing RC-30 RC-70 RC-250 RC-800 RC-3000 Binder Kerosene Medium Curing MC-30 MC-70 MC-250 MC-800 MC-3000 Based on Kinematic Viscosity at 140 F Low Volatility Oils Slow Curing SC-30 SC-70 SC-250 SC-800 SC-3000 Figure 3-5. Cutback Asphalt Types The varying degree of fluidity obtained in each case depends on the: Grade of asphalt cement Volatility of the solvent Proportion of solvent to binder. The degree of fluidity results in several grades of cutback asphalt. Some are quite fluid at ordinary atmospheric temperatures, while others are somewhat more viscous and may require heating to melt them enough for construction operations. Cutback asphalts can be used with cold aggregates, with a minimum of heat. VDOT and Platinum Performance Partners, LLC Chapter 3 page 11

36 Components of Asphalt Concrete RC and MC cutback asphalts have a variety of uses in highway construction, including road mixing operations, stockpiling mixes, and spray applications. The specifications for cutback asphalt are in the Road and Bridge Specifications, Section 210. Emulsified Asphalts Emulsified asphalt is a suspension of asphalt in water containing an emulsifying agent. In the emulsification process, a machine called a colloid mill mechanically separates hot binder into minute globules (i.e., tiny globes or ball) and disperses them in water treated with a small quantity of an emulsifying agent. The water is called the continuous phase and the globules of binder are called the discontinuous phase. The binder globules are extremely small, mostly in the colloidal size range. By proper selection of an emulsifying agent and other manufacturing controls, emulsified asphalts are produced in several types and grades, as illustrated in Figure 3-6. By choice of emulsifying agent, the emulsified asphalt may be: 1. Anionic Binder globules with negative electrostatic charge. 2. Cationic Binder globules with positive electrostatic charge. Emulsions are also classified by how quickly they set-up or break upon application. The typical nomenclature used in the paving and asphalt industry includes: Rapid-Setting (RS) Medium-Setting (MS) Slow-Setting (SS) Figure 3-6. Emulsified Asphalt Types page 12 Chapter 3 VDOT and Platinum Performance Partners, LLC

37 Components of Asphalt Concrete Also, by variation in materials and manufacture, emulsified asphalts of both anionic and cationic types are made in several grades. Some of these grades and their uses are listed in the table below, per emulsified asphalt type. Grades Anionic Non-Virginia grades Types a. RS-2 tack and seal coat b. SS-1h slow set slurry and tack Cationic - Virginia grades a. CRS-2 tack and seal coat b. CRS-1 tack c. CRS-1h tack d. CSS-1h two types for slurry (rapid set and slow set) and tack e. CMS-2 prime, tack, seal, and cold mix (contains 7-12% solvent) Because particles having a like electrostatic charge repel each other, asphalt globules are kept apart until the emulsion is deposited on the surface of the soil or aggregate particles. When this occurs, the asphalt globules coalesce through neutralization of the electrostatic charges or water evaporation. Coalescence of asphalt globules occurs in rapid and medium setting grades, resulting in a phase separation between asphalt and water. When this coalescence occurs, it is usually referred to as the break or set. Emulsified asphalts can be used with both cold and heated aggregates, and with aggregates that are dry, damp or wet. The specifications for emulsified asphalts are in the Road and Bridge Specifications, Section 210. VDOT and Platinum Performance Partners, LLC Chapter 3 page 13

38 Components of Asphalt Concrete Testing of PG Binders and Liquid Asphalts The purpose of PG binder testing is to ensure that the binder conforms to AASHTO M 320: Standard Specification for Performance-Graded Asphalt Binder for that binder type throughout the life of the binder. A PG binder is specified as a combination of two temperatures (i.e. 70 C and -22 C). The high temperature (70 C) refers to the 7-day average high temperature for an area, whereas the low temperature (-22 C) refers to the single lowest temperature expected in that area. Consequently, the binder is graded as PG Figure 3-7 illustrates this concept. Figure 3-7. Performance Grading The life of a binder can be categorized into three stages, with each stage requiring a different test, as indicated in the table that follows. In the rest of this section, we will explore the tests that are conducted on PG binder, recovered binder and liquid asphalt. Stage Stage 1: Transport, storage, and handling Stage 2: Mix production and construction Test Description Tests performed during this stage are run on the original binder material. Tests performed during this stage are run on Rolled Thin Film Oven-aged (RTFO) binder material. These tests simulate the binder as it passes through a plant. Stage 3: After a long period in a pavement Tests performed during this stage are run on Pressure Aging Vessel (PAV) binder material. These tests simulate the binder after an extended period of time in the pavement page 14 Chapter 3 VDOT and Platinum Performance Partners, LLC

39 Components of Asphalt Concrete PG Binder Testing The purpose of PG binder testing is to ensure that the binder conforms to AASHTO M320 specifications for that binder type throughout the life of the binder. The better you understand the tests, why they are done and the key factors affecting test results, the better prepared you will be to produce consistent results. PG binder testing includes the tests indicated and described in the table below. TOOLS AND EQUIPMENT Rotational Viscometer Used to evaluate the high temperature and workability of binders Dynamic Shear Rheometer Used to measure the stiffness or resistance of the binder Test Conducted On Description 1. Rotational Viscosity Test (ASTM D4402) 2. Dynamic Shear Test (AASHTO T 315) 3. Flash Point Test (AASHTO T48 Cleveland Open Cup) 4. Mass Loss (AASHTO T 240) 5. Creep Stiffness (AASHTO T 313) Original Binder Original Binder RTFO-Aged Binder PAV-Aged Binder Original Binder RTFO-Aged Binder PAV-Aged Binder A rotational viscometer is used to evaluate the high temperature workability of a binder. This ensures that the binder is sufficiently fluid when pumping and mixing. In addition, the viscosity measured is used to establish the temperature-viscosity plot for a binder type. A dynamic shear rheometer is used to measure the stiffness or resistance of the binder to deform under loading. The flash point of a binder is measured to ensure the binder is safe to work with at production temperatures. Flash point is the temperature to which a binder may be safely heated without instantaneous flash in the presence of an open flame. The mass loss indicates the amount of impurities (i.e. water, gas, hydraulic fluid) present in the binder. The creep stiffness is a measure of how brittle the binder becomes after an extended period in the pavement. VDOT and Platinum Performance Partners, LLC Chapter 3 page 15

40 Components of Asphalt Concrete Chemical Extraction and Recovery of Binder for Testing To ensure that the binder used in asphalt mixtures meets State specifications, The Department will sample the plant-produced mixture, chemically extract the binder, and test it for conformance with the state specification (i.e. the PG Binder Grade required for the mix type being produced). The asphalt binder is first chemically extracted from the mixture using an approved chemical solvent and a high speed centrifuge. The binder is then recovered from this solvent binder solution using the Abson recovery method which slowly distills out the solvent, leaving behind only the binder from the original asphalt mixture sample. The recovered binder is then tested for conformance to PG Grade specified. VDOT performs the Abson Recovery Test (AASHTO T170), in which the completed mix has the asphalt cement extracted by a chemical procedure that does not change the asphalt cement properties. Why do it? The purpose of this test is to ensure that the asphalt binder being shipped to the project meets all of the PG Binder specifications required for the mix type being produced. Failure to meet the requirements could indicate damage or aging that may have taken place during the storage and mixing of the asphalt. When recycled asphalt pavement (RAP) is a component of the mix, the aged asphalt in the RAP can become a significant contributor to the aged properties of the mix. If a PG Binder test fails in accordance with Section 211, then the approval of the mix type being produced may be suspended until the contractor can demonstrate that the mix being produced meets all specification requirements. Liquid Asphalt Testing The tests shown in the table below are conducted on liquid asphalt, and recovered asphalt residue, respectively, and are described in the text that follows. Tested on the Liquid Asphalt: Viscosity Test Flash Point Test (Cutback asphalts only) Tested on the Recovered Asphalt Residue: Penetration Test Ductility Test Percent Residue page 16 Chapter 3 VDOT and Platinum Performance Partners, LLC

41 Components of Asphalt Concrete Viscosity Test (AASHTO T201 and T72) Viscosity is a measure of a liquid s resistance to flow. VDOT has adopted the AASTHO specifications for cutbacks and emulsions; these specifications will define the type of viscosity test and the temperature at which the test will be run. Measurement of viscosity may be made by the Saybolt Furol Viscosity Test (Figure 3-8) or the Kinematic Viscosity Test. These tests and the temperatures at which they are run have been designed based on the field application intended for the material type being used. Figure 3-8. Saybolt Furol Viscosity Test Equipment Why do it? The purpose of the viscosity test is to provide control of asphalt consistency in the range of temperatures normally associated with construction operations (i.e. that a CRS-2 will spray easily and uniformly when applied by a distributor Figure 3-9). Figure 3-9. Equipment Used During Application, Requiring Ease and Uniformity of Spray VDOT and Platinum Performance Partners, LLC Chapter 3 page 17

42 Components of Asphalt Concrete Flash Point Test (AASHTO T79) Flash point is the temperature to which the liquid binder (cutback) may be safely heated without instantaneous flash in the presence of an open flame. This test is performed on the original liquid binder. Why do it? The flash point is measured to ensure the cutback asphalt is safe to work with at production temperatures. Figure 3-10 illustrates flash point testing. Percent Residue (AASHTO T 59) Measured either by evaporation or distillation, the non-asphalt cement components are driven off, leaving only the asphalt cement or residue behind. Figure Flash Point Testing Why do it? The percent residue test ensures that the proper amount of asphalt cement is in the liquid asphalt, so that material performs as needed in the field. The recovered asphalt may also then be tested further for penetration and ductility, also to ensure proper performance in the field. Penetration Test (AASHTO T49) The penetration test is an empirical measure of asphalt consistency. The basic assumption is that the less viscous the asphalt, the deeper a needle will be able to penetrate the asphalt, as illustrated in Figure Why do it? This penetration depth is correlated with asphalt binder performance. Asphalt binders with high penetration numbers are used for cold climates, while asphalt binders with low penetration numbers are used for warm climates. In testing, a container of asphalt cement is heated to the standard test temperature 77 F (25 C) in a temperature-controlled water bath. A prescribed needle, weighted to 100 grams, is allowed to bear on the surface of the asphalt cement for 5 seconds. The distance (in units of 0.1 mm) which the needle penetrates into the asphalt cement is the penetration factor or measurement. Figure 3-12 illustrates how the penetration testing process works. Figure Penetration Test Occasionally, the penetration test is made at a different temperature than shown in Figure When this occurs, needle load, penetration time, or both may be varied. page 18 Chapter 3 VDOT and Platinum Performance Partners, LLC

43 Components of Asphalt Concrete Figure How Penetration Testing Works Ductility Test (AASHTO T 51) In many applications, ductility is considered an important characteristic of binders. The presence or absence of ductility, however, is usually considered more significant than the actual degree of ductility. Why do it? Binders possessing ductility are normally more adhesive than binders lacking this characteristic. However, some binders with an exceedingly high degree of ductility are also more temperature-susceptible. That is, the change in consistency is apt to be greater for a change in temperature. In some applications, such as paving mixes, ductility and adhesion are more important. In other situations, such as slab undersealing and crack filling, the more essential property is low temperature susceptibility. Ductility is measured by an extension type Figure Ductility Test of test, where a standard briquette of binder is molded under standard conditions and dimensions. It is then brought to standard test temperature, normally 77 F (25 C) and pulled apart at a uniform speed until the briquette ruptures, as shown in Figure The distance that the briquette is pulled until it ruptures is measured in centimeters. VDOT and Platinum Performance Partners, LLC Chapter 3 page 19

44 Components of Asphalt Concrete Aggregates An aggregate is defined as any inert mineral material used for mixing in graduated particles or fragments. It includes sand, gravel, crushed stone, slag, screenings and mineral filler, ranging in size from coarse to fine, as depicted in Figure The amount of aggregate in asphalt concrete mixtures is generally 90 to 95% by weight and 75 to 85% by volume. Aggregates are primarily responsible for the load-supporting capacity of a pavement. Figure Aggregate Sources of Aggregates Aggregates for asphalt concrete are generally classified according to their source or means of preparation. The graphic in Figure 3-15 summarizes the various sources of aggregate. Sources of Aggregate Naturally Occurring (Pit) Industrially Prepared Gravel Sand Synthetic or Artificial Aggregates Processed Aggregates Modified Materials Natural gravel or stone, crushed and screened Figure Sources of Aggregate page 20 Chapter 3 VDOT and Platinum Performance Partners, LLC

45 Components of Asphalt Concrete The table that follows summarizes aggregate type by source. Aggregate Type Pit Aggregates Processed Aggregates Synthetic or Artificial Aggregates Source or Means of Preparation Gravel and sand are natural aggregates and are typically pit material. Natural gravel or stone that has been crushed and screened are typical processed aggregates. In the crushing operation, stone dust is also produced. Aggregates resulting from the modification of materials, which may involve both physical and chemical changes. Blast furnace slag is the most commonly used artificial aggregate or lightweight aggregate. Evaluating Source Properties 1. Cleanliness Some aggregates contain foreign or deleterious substances that make them undesirable for asphalt concrete mixtures (e.g., clay lumps, shale and organic material). The Sand-Equivalent Test, described in AASHTO T 176, is a method of determining the relative proportion of detrimental fine dust or clay-like materials in the portion of aggregate passing the No. 4 (4.75 mm) sieve. 2. Toughness (Hardness) Aggregates are subjected to additional crushing and abrasive wear during manufacture, placement and compaction of asphalt concrete mixtures. Aggregates are also subjected to abrasion under traffic loads. They must exhibit an ability to resist crushing, degradation and disintegration. The Los Angeles Abrasion Test, described in AASHTO T 96, measures wear abrasion resistance of aggregates. 3. Soundness Aggregates for asphalt concrete paving should be durable. They should not deteriorate or disintegrate as a result of weather. Items for consideration under weathering action are freezing, thawing, varying moisture content and changing temperatures. The Soundness Test, described in AASHTO T104, is an indication of the resistance to weathering of fine and coarse aggregates. VDOT and Platinum Performance Partners, LLC Chapter 3 page 21

46 Components of Asphalt Concrete Evaluating Consensus Properties of Aggregates Selecting an aggregate material for use in an asphalt concrete depends upon the availability, cost and quality of the material, as well as the type of construction for which it is intended. The suitability of aggregates for use in asphalt concrete is determined by evaluating the material in terms of: 1. Size and Grading The maximum size of an aggregate designates the smallest sieve size through which 100% of the material will pass. Grading of an aggregate is determined by sieve analysis. Maximum size and grading are invariably controlled by specifications that prescribe the distribution of particle sizes to be used for a particular aggregate material for asphalt mixtures. The distribution of the particle sizes determines the stability and density of the asphalt mixture. 2. Particle Shape (Flat & Elongated or F/E) Particle shape changes not only the workability of the mix, but also the compactive effort necessary to obtain the required density. Particle shape also has an effect on the strength of the asphalt concrete mix. Irregular or angular particles tend to interlock when compacted and resist displacement. 3. Surface Texture (Coarse Aggregate Angularity or CAA, and Fine Aggregate Angularity or FAA) Like particle shape, the surface texture also influences the workability and strength of asphalt concrete mixtures. In fact, surface texture has often been considered more important than shape of the aggregate particles. A rough, sandpaper-like surface texture, as opposed to a smooth surface, tends to increase the strength of the mix. 4. Absorption The porosity of an aggregate is generally indicated by the amount of water it absorbs when soaked in water. A certain degree of porosity is desirable, as it permits aggregates to absorb binder, which then forms a mechanical linkage between the binder film and the stone particle. Aggregates with high porosity will require higher asphalt contents due to loss of binder to the stone. They also tend to be weaker and may not be suitable for use in asphalt concrete. 5. Affinity for Binder Stripping (separation) of the binder film from the aggregate through the action of water may make an aggregate material unsuitable for asphalt concrete mixtures. Such material is referred to as hydrophilic (water loving). Many of these materials may be used with the addition of a heat stable additive that reduces the stripping action. Aggregates which exhibit a high degree of resistance to stripping in the presence of water are usually the most desirable in asphalt concrete mixes. Such aggregates are referred to as hydrophobic (water hating). Why hydrophobic or hydrophilic aggregates behave as they do is not completely understood. The explanation is not as important as the ability to detect the properties and avoid the use of aggregates conducive to stripping. The strength loss resulting from damage caused by stripping under laboratory-controlled accelerated water conditioning is determined in accordance with AASHTO T 283. Note: Specification criteria for items (1) through (6) can be found in Sections 202, 203 and 211 of the Road and Bridge Specifications. Item (8) is determined through experience. page 22 Chapter 3 VDOT and Platinum Performance Partners, LLC

47 Components of Asphalt Concrete Aggregate Storage Provisions should be made for adequate storage and stockpiling facilities for all component materials. Aggregates should be handled, hauled and stored in a manner that will minimize segregation and degradation and avoid contamination. These suggestions should be followed for best results: 1. The aggregate should be stockpiled in the vicinity of the plant on ground that is hard, well drained, and has been denuded of vegetation or otherwise prepared to protect the aggregate from contamination. 2. Stockpiles should be separated to prevent intermingling, as shown in Figure This may be accomplished by positive separation of stockpiles and bins, or by using adequate bulkheads. Bulkheads should extend to the full depth of the stockpiles and should be strong enough to withstand the pressures exerted under operating conditions. 3. Stockpiles should be constructed in layers, rather than in cones. Individual truckloads should be spotted close together over the entire stockpile surface. Figure Proper Stockpiling, Fine and Coarse 4. When stockpiling with a crane, each bucket load should be deposited adjacent to another over the entire area so that the thickness of the layers is uniform. 5. When aggregate is discharged from chutes, baffles should be arranged to prevent the coarse aggregate from rolling to the far side while the fine aggregate collects beneath the chute. Perforated chimneys also may be used to prevent segregation of aggregates when stockpiling from a belt conveyor chute. 6. When cars, barges or trucks are used as stockpiles, care should be exercised in loading and unloading to prevent segregation. When constructing, maintaining or withdrawing from stockpiles, care should be taken to prevent aggregate degradation by the hauling equipment. 7. Mineral filler is subject to caking or hardening from moisture. Consequently, it is handled differently than other aggregates. Separate storage should be provided to keep it protected from dampness. BEST PRACTICE Sufficient material should be on hand prior to starting daily operations to insure continued processing for the working day. Describes a best practice. VDOT and Platinum Performance Partners, LLC Chapter 3 page 23

48 Components of Asphalt Concrete Chapter Three Knowledge Check 1. A method of classification used to determine performance properties of binder is: A. Penetration B. Variability C. Ductility D. Performance grading 2. Binder blended with a kerosene-type material is known as: A. Emulsified asphalt B. RC asphalt C. MC asphalt D. SC asphalt 3. A method of determining flow properties of a binder is: A. Penetration B. Viscosity C. Ductility D. Impermeability 4. Binder which has been liquefied with heat or petroleum solvents or emulsified with water is known as: A. Crude petroleum B. Liquid asphalt C. Asphalt residue D. Air-blown asphalt 5. Binder blended with a naphtha or gasoline-type material is called: A. MC asphalt B. Emulsified asphalt C. SC asphalt D. RC asphalt 6. An example of an artificial aggregate is blast furnace slag. A. True B. False page 24 Chapter 3 VDOT and Platinum Performance Partners, LLC

49 Components of Asphalt Concrete 7. Aggregates should be handled and stockpiled in such a manner as to minimize: A. Hauling time B. Segregation C. Waste D. Moisture 8. Hot mix asphalt concrete can be considered to be made up of two ingredients: A. Cutback asphalt and aggregates B. Binder and aggregates C. Emulsified asphalt and aggregates D. All of the above 9. A suspension of a binder in water containing an emulsifying agent, such as soap, is called: A. Cutback asphalt B. Air blown asphalt C. Crude petroleum D. Emulsified asphalt 10. Asphalt binders become harder (more viscous) as their temperature decreases and softer (less viscous) as their temperature increases A. True B. False 11. How should the site for stockpiles be prepared? 12. How should stockpiles be handled? 13. How much material should to be on hand before starting daily operations? VDOT and Platinum Performance Partners, LLC Chapter 3 page 25

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51 MCS: Asphalt Plant Certification 4 Asphalt Concrete Mixtures Mix design methods and design requirements are an essential part for all asphalt concrete mixtures. The agency or authority responsible for paving construction (the Department of Transportation) usually establishes the mix design method and design requirements. Once these are established, it becomes the responsibility of the Contractor/Producer and their Technician to develop the mix within the framework of the specification requirements. This chapter describes the physical properties required of asphalt concrete mixtures and presents mixture types used in Virginia. Learning Objectives: Upon completion of this chapter, you should be able to: Identify the physical properties of asphalt concrete mixtures Define asphalt mix properties and their effect on pavement performance List the types of asphalt mixtures used for highway construction in Virginia Identify the individual layers of a pavement structure VDOT and Platinum Performance Partners, LLC Chapter 4 page 1

52 Asphalt Concrete Mixtures Physical Properties Required of Asphalt Concrete Mixtures The following terms will be used throughout this section: Stability Impermeability Workability Flexibility Fatigue resistance Skid resistance Stripping Void content Subbase Subgrade The asphalt pavement s ability to resist shoving and rutting under loads (e.g., traffic). The resistance of an asphalt pavement to the passage of air and water into or through it. The ease with which a paving mixture can be placed and compacted. The asphalt pavement s ability to adjust to gradual settlements and movements in the subgrade without cracking. The asphalt pavement s resistance to repeated bending under wheel loads (e.g., traffic). The ability of an asphalt surface to minimize skidding or slipping of vehicle tires, particularly when wet. Separation of asphalt binder film from aggregate surfaces. Empty spaces within the aggregate particle that can become filled with water, binder, or both. The layer of aggregate material laid on the subgrade. The native material (i.e., level layer of rock or earth) upon which the foundation of a road is constructed. Asphalt concrete mixtures are composed of two components: Aggregates Fine and coarse, that make up 90-95% of the total mix (by weight) Asphalt A performance graded (PG) binder that makes up 5-10% of the total mix (by weight) Mix design methods and design requirements are essential determinants of asphalt concrete mixtures. The Department of Transportation usually establishes the mix design method and design requirements for paving construction. It is the responsibility of the Contractor/Producer and his Technician to develop the mix within the framework of the specification requirements. The pavement industry relies on the physical properties of asphalt concrete mixtures to ensure performance. The properties of an asphalt concrete mixture are a direct result of its chemical composition. page 2 Chapter 4 VDOT and Platinum Performance Partners, LLC

53 Asphalt Concrete Mixtures The following physical properties are required of asphalt concrete mixtures and will be addressed in this section of the chapter: Stability Durability Low Permeability Workability Flexibility Fatigue Resistance Skid Resistance Stability Stability of an asphalt pavement is its ability to resist distortions shoving and rutting (i.e., surface depression or channels in the wheelpath) under traffic loads. A stable pavement maintains its shape and smoothness under repeated loading. An unstable pavement: Develops ruts, as shown in Figure 4-1 Develops ripples (e.g., washboarding or corrugation) Shows other signs of shifting of the mixture. Stability specifications for a pavement depend on the traffic expected to use the pavement. Consequently, the requirements can be established only after a thorough traffic analysis. Figure 4-1. Rutting BEST PRACTICE Stability specifications should be high enough to handle traffic adequately, but not higher than traffic conditions require. Too high a stability value produces a pavement that is too stiff, and therefore, less durable than desired. Describes a best practice to be utilized when possible. VDOT and Platinum Performance Partners, LLC Chapter 4 page 3

54 Asphalt Concrete Mixtures Insufficient stability in a pavement has many causes and effects. The stability of a mixture depends on: Internal friction Friction among the aggregate particles (i.e., interparticle friction), which is related to characteristics of the aggregate, such as its shape and surface texture Cohesion Which results from the bonding ability of the binder A proper degree of both internal friction and cohesion in a mix prevents the aggregate particles from being moved past each other by the forces exerted by traffic. In general, the more angular the shape of the aggregate particles and the rougher the surface texture, the higher the stability of the mix will be. The binding force of cohesion increases: With increasing loading (traffic) rate As the viscosity of the binder increases As the pavement temperature decreases. Where aggregates with high internal friction characteristics are not available, more economical mixtures using aggregate with lower friction values can be used where light traffic is expected. AWARENESS/IMPORTANT Cohesion will increase with increasing binder content, up to a certain point. Past that point, increasing binder content will create too thick a film on the aggregate particles, resulting in a loss of interparticle friction. Highlights a step in the procedure which is either unusual or very particular to this procedure. May also indicate awareness (additional information) or a cautionary concern in the procedure. Durability The durability of an asphalt pavement is its ability to resist factors such as changes in the binder. Factors that may affect durability include polymerization and oxidation, disintegration of the aggregate and stripping (i.e., separation of asphalt binder film from aggregate surfaces), which is illustrated in Figure 4-2. These factors can be the result of weather, traffic, or a combination of the two. A lack of sufficient durability in a pavement can have several causes and effects. The durability of a mixture can be enhanced by three methods: Using an optimized binder content Using a dense gradation of stripping-resistant aggregate Designing and compacting the mixture for maximum impermeability Figure 4-2. Underlying Stripping page 4 Chapter 4 VDOT and Platinum Performance Partners, LLC

55 Asphalt Concrete Mixtures Optimized binder content increases durability because thick binder films do not age and harden as rapidly as thin ones do. Consequently, the binder retains its original characteristics longer. Also, maximum binder content effectively seals off a greater percentage of interconnected air voids in the pavement, making it difficult for water and air to penetrate. AWARENESS/IMPORTANT A certain percentage of air voids must be left open in the pavement to allow for expansion of the binder in hot weather. Highlights a step in the procedure which is either unusual or very particular to this procedure. May also indicate awareness (additional information) or a cautionary concern in the procedure. A dense gradation of sound, tough, stripping-resistant aggregate contributes to pavement durability in three ways: 1. It provides closer contact among aggregate particles, which enhances the impermeability of the mixture. 2. It resists disintegration under traffic loading. 3. It resists the action of water and traffic, which tend to strip the binder film off aggregate particles, leading to raveling of the pavement. Under some conditions, the resistance of a mixture to stripping can be increased by the use of an antistripping agent (i.e., a heat stable additive used to prevent the binder from separating from the aggregate) or mineral filler such as hydrated lime. BEST PRACTICE Impermeability Designing and compacting the mixture to give the pavement maximum impermeability minimizes the intrusion of air and water into the pavement. Impermeability is the resistance of an asphalt pavement to the passage of air and water into or through it. Impermeability is important for durability of compacted paving mixtures. Impermeability is related to the void content of the compacted mixture, as shown in Figure 4-3. Much of the discussion on voids in the mix design sections relate to impermeability. Even though void content is an indication of the potential for passage of air and water through a pavement, the character of these voids is more important than the number of voids. Describes a best practice to be utilized when possible. Figure 4-3. Air Voids in Compacted Asphalt VDOT and Platinum Performance Partners, LLC Chapter 4 page 5

56 Asphalt Concrete Mixtures The degree of impermeability is determined by: The size of voids Whether the voids are interconnected The access of the voids to the surface of the pavement. Aggregate structure (shape, size and gradation) within the mix. AWARENESS/IMPORTANT Virtually all asphalt mixtures used in highway construction are permeable to some degree. This is acceptable as long as it is within specified limits. Highlights a step in the procedure which is either unusual or very particular to this procedure. May also indicate awareness (additional information) or a cautionary concern in the procedure. Workability Workability is the ease with which a paving mixture can be placed and compacted, as Figure 4-4 illustrates. Mixtures with good workability are easy to place and compact; those with poor workability are difficult to place and compact. Workability can be improved by changing mix design parameters, aggregate source, and/or gradation. Binder grade may affect workability (for example, the percentage of binder in the mix). And although not normally a major contributor to workability problems, the asphalt binder can also have some effect on workability. Figure 4-4. Workability of Paving Material AWARENESS/IMPORTANT Care should be taken to ensure that the altered mix meets all other design criteria, such as void content and stability. Too high a filler content can also affect workability, causing the mix to become gummy and making it difficult to compact. Highlights a step in the procedure which is either unusual or very particular to this procedure. May also indicate awareness (additional information) or a cautionary concern in the procedure. The temperature of the mix affects the viscosity of the binder. Too low a temperature will make a mix harsh and unworkable. Too high a temperature may make it tender. The table on the next page provides descriptors for both harsh and tender mixtures and the typical problems they trigger. page 6 Chapter 4 VDOT and Platinum Performance Partners, LLC

57 Asphalt Concrete Mixtures Mixtures with Poor Workability Harsh Mixtures Mixtures which contain a high percentage of coarse and or angular aggregates Tender Mixtures Mixtures that can be too easily worked or shoved Typical Problems Harsh mixtures have a tendency to segregate during handling and also may be difficult to compact. Through the use of trial mixes in the laboratory, additional fine aggregate and perhaps binder, can be added to a harsh mix to make it more workable. Tender mixtures are too unstable to place and compact properly. They are often caused by: A shortage of mineral filler Too much medium-sized sand Smooth, rounded aggregate particles Too much moisture in the mix AWARENESS/IMPORTANT Workability is especially important where quite a bit of hand placement and raking (i.e., luting) around manhole covers, sharp curves, and other obstacles is required. It is important that mixtures used in such areas are highly workable. Highlights a step in the procedure which is either unusual or very particular to this procedure. May also indicate awareness (additional information) or a cautionary concern in the procedure. Flexibility Flexibility is the ability of an asphalt pavement to adjust to gradual settlements and movements in the subgrade (the level layer of rock or earth upon which the foundation of a road is constructed) without cracking. Figure 4-5 illustrates settlement, an example of a flexibility issue. Since virtually all subgrades either settle (under loading) or rise (from soil expansion), flexibility is a desirable characteristic for all asphalt pavements. An open-graded mix with high binder content is generally more flexible than a dense-graded, low binder content mix. Figure 4-5. Settlement Sometimes the need for flexibility conflicts with stability requirements. For example, an open-graded mixture, which is generally more flexible, is designed to be water permeable. A dense-graded mix is relatively impermeable, but is less flexible. Both can affect stability and may require that trade-offs be made. VDOT and Platinum Performance Partners, LLC Chapter 4 page 7

58 Asphalt Concrete Mixtures Fatigue Resistance Fatigue resistance is the pavement s resistance to repeated bending under wheel loads (i.e., traffic). Figure 4-6 shows an example of pavement that is showing fatigue. Research shows that air voids (related to binder content) and binder viscosity have a significant effect on fatigue resistance. As the percentage of air voids in the pavement increases, either by design or lack of compaction, pavement fatigue life (i.e., the length of time during which an in-service pavement is adequately fatigue-resistant) is drastically shortened. Figure 4-6. Fatigue Issue Likewise, a pavement containing binder that has aged and hardened significantly has reduced resistance to fatigue. Pavement life and the prevention of load-associated cracking are also influenced by the thickness and strength characteristics of the pavement and the supporting power of the subgrade. Thick, wellsupported pavements do not bend as much under loading as thin or poorly supported pavements do. Therefore, they have longer fatigue lives. Figure 4-6. Fatigue Issue after Six Months of Service Skid Resistance Skid resistance is the ability of an asphalt surface to minimize skidding or slipping of vehicle tires, particularly when wet. Skid resistance is typically measured in the field at 40 miles per hour with a standard tread tire under controlled wetting of the pavement surface. Skid resistance is important because inadequate skid resistance will lead to high incidences of road skid accidents. For good skid resistance, tire tread must be able to maintain contact with the aggregate particles instead of riding on a film of water on the pavement surface (hydroplaning). Three factors have an important impact on skid resistance: Pavement texture Aggregate texture Asphalt content page 8 Chapter 4 VDOT and Platinum Performance Partners, LLC

59 Asphalt Concrete Mixtures A rough pavement surface with many little peaks and valleys will have greater skid resistance than a smooth surface. Besides having a rough surface, the aggregates must resist polishing (i.e., smoothing) under traffic. Calcareous aggregates (i.e., aggregates containing calcium carbonate) polish more easily than siliceous aggregates (i.e., composed mainly of silica or silicates). Unstable mixtures that tend to rut or bleed (i.e., flush asphalt to the surface) present serious skid resistance problems. BEST PRACTICE Best skid resistance is obtained with rough-textured aggregate in a relatively open-graded mixture with a maximum aggregate size of about 3/8 in.-1/2 in. (10-13 mm). Describes a best practice to be utilized when possible. VDOT and Platinum Performance Partners, LLC Chapter 4 page 9

60 Asphalt Concrete Mixtures Mixture Types Used in Virginia DEFINITIONS. The following terms will be used throughout this section: Surface mixes (SM) Intermediate mixes (IM) Base mixes (BM) The upper most layer of the pavement structure is called the surface or wearing course. Used as a binder course between the surface course and base course when needed to add strength and thickness to the pavement structure. Placed immediately below the surface course (or binder course if a binder course is found to be necessary), this layer is called the base course and is the structural strength element of the asphalt concrete pavement system. The basic requirements in building a road for safe all-weather use by vehicles are to: 1. Prepare a suitable subgrade or foundation (with proper density) 2. Provide necessary drainage 3. Construct a pavement that will: Have sufficient total thickness and internal strength to carry expected traffic loads; Prevent the penetration or internal accumulation of moisture; and Have a top surface that is smooth, skid resistant, and resistant to wear, distortion and deterioration by weather and de-icing chemicals. The goal of a flexible pavement structure is to achieve these requirements. A flexible pavement structure consists of all the asphalt concrete courses or layers above the prepared subgrade (native material, such as rock or earth), as shown in Figure 4-7. Together, these courses support Figure 4-7. Flexible Pavement Structure (Muench, 2011) the wheel loads on the pavement surface and transfer and spread these loads to the subgrade without exceeding the support capability of the subgrade material or over-stressing the pavement components. page 10 Chapter 4 VDOT and Platinum Performance Partners, LLC

61 Asphalt Concrete Mixtures There are many types of asphalt concrete mixtures used in highway construction to meet the previously stated requirements. In Virginia however, there are three basic types, each of which has a specific purpose and location within an asphalt concrete pavement structure: Surface mixes ( SM ) Intermediate mixes ( IM ) Base mixes ( BM ). Note: Section 211 discusses each type in more detail. Surface Mixes ( SM ) The upper most layer of the pavement structure is called the surface or wearing course. It is the layer in contact with traffic loads and normally contains the highest quality materials. It is meant to take the brunt of traffic wear and can be removed and replaced as it becomes worn. It provides characteristics such as friction, smoothness, noise control, resistance to rutting and shoving, and drainage. This course or layer is usually composed of an SM mix. Figure 4-8 illustrates the application of an SM type mix. Figure 4-8. Applying an SM Type Mix Intermediate Mixes ( IM ) In special cases where added strength is needed in the pavement structure, IM type mixes are sometimes used in the surface course. It provides the bulk of the HMA structure. Its chief purpose is to distribute load. This binder or intermediate course is composed of an IM type mix. Figure 4-9 illustrates an IM type mix. Figure 4-9. IM Type Mix VDOT and Platinum Performance Partners, LLC Chapter 4 page 11

62 Asphalt Concrete Mixtures Base Mixes ( BM ) The base course is placed immediately below the surface course (or binder course if a binder course is found to be necessary). The base course is the structural strength element of the asphalt concrete pavement system. It provides additional load distribution and contributes to drainage and frost resistance. It is composed of a BM type mix. Figure 4-10 is a photo showing a BM type mix. Figure Base Type Mix page 12 Chapter 4 VDOT and Platinum Performance Partners, LLC

63 Asphalt Concrete Mixtures Chapter Four Knowledge Check 1. The frictional resistance of the surface of the pavement to insure safe driving and stopping of the vehicle is called: A. Durability B. Stability C. Flexibility D. Skid resistance 2. The ability of the asphalt pavement to withstand repeated flexing or slight bending caused by the passage of wheel loads is called: A. Ductility B. Fatigue resistance C. Flexibility D. Variability 3. The resistance of pavement to the effects of traffic, water, air and temperature changes is known as: A. Durability B. Flexibility C. Variability D. Ductility 4. The ability of a pavement to adjust itself to settlement of the base without cracking is known as: A. Impermeability B. Stability C. Workability D. Flexibility 5. The ease with which the material can be placed to the desired uniformity and compacted to the required density is known as: A. Viscosity B. Stability C. Workability D. Flexibility VDOT and Platinum Performance Partners, LLC Chapter 4 page 13

64 Asphalt Concrete Mixtures 6. Type SM-12.5A asphalt concrete is a: A. Base course mix B. Surface course mix C. Binder course mix D. Cold mix 7. Four physical properties that are required of asphalt concrete mixtures are: A. Binder content, flexibility, stability, and rolling B. Stockpile analysis, hardness, stability, and durability C. Specific gravity, stability, durability, and flexibility D. Stability, flexibility, durability, and resistance to skidding 8. Type IM-19.0A asphalt concrete is a: A. Base course mix B. Surface course mix C. Intermediate course mix D. Cold mix 9. The resistance an asphalt concrete pavement has to the passage of air and water into or through the pavement is known as: A. Penetration B. Flexibility C. Impermeability D. Skid resistance 10. Type BM-25.0 asphalt concrete is a: A. Base course mix B. Surface course mix C. Binder course mix D. Cold mix page 14 Chapter 4 VDOT and Platinum Performance Partners, LLC

65 Asphalt Concrete Mixtures 11. The upper or top layer of an asphalt concrete pavement structure is the: A. Base course B. Surface course C. Binder course 12. The subgrade ultimately carries all traffic loads. A. True B. False 13. The main structural strength element of a pavement is the: A. Subgrade B. Base course C. Surface course 14. The layer of an asphalt concrete pavement that distributes traffic loads to the subgrade is the : A. Surface course B. Intermediate course C. Base course D. Drainage layer 15. Stability may be improved by using aggregates with rough surface texture. A. True B. False VDOT and Platinum Performance Partners, LLC Chapter 4 page 15

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67 MCS: Asphalt Plant Certification 5 Asphalt Concrete Plants Asphalt concrete mixes made with asphalt cement are prepared at an asphalt mixing plant. Here, aggregates are blended, heated, dried and mixed with asphalt cement to produce a hot mix asphalt (HMA). There are two basic types of plants used to manufacture asphalt concrete: Batch plants, which make asphalt in batches as needed Drum plants, which make asphalt continuously These two types of asphalt plants derive their names from their particular mixing operation. In the batch-type mixing plant, hot aggregate and asphalt are withdrawn in desired amounts to make up one batch for mixing. After thoroughly mixing, the material is discharged in one batch. In the drum-type mixing plant, the aggregate is dried, heated and mixed with the asphaltic cement in the drum in a continuous operation. Either system can store the asphalt for several days in heated storage silos. This chapter discusses these two types of asphalt plants, their operation and main components, special procedures to ensure mixture success, and typical plant problems. Learning Objectives: Upon completion of this chapter, you should be able to: Describe the operation of both batch-type and drum-type mixing plants Recall tips for successful operation of the various components Describe minimum and maximum mixing times Use the Ross Count Procedure to determine minimum mixing times Determine the percentage of moisture content in aggregate and asphalt concrete mixtures Identify likely solutions for common plant problems VDOT and Platinum Performance Partners, LLC Chapter 5 page 1

68 Asphalt Concrete Plants Batch Plant The following terms will be used throughout this section: Batch asphalt plant Cold aggregate bins and feeders Cold elevator Dryer Emissions Control System Dust collector Screening unit (plant screens or screen deck) Hot bins Hot elevator Carry-over Pugmill Mineral filler RAP Weigh box Dry mixing time Wet mixing time A manufacturing facility for producing hot asphalt mix that makes the product in batches, rather than continuously. Containers that store aggregate and accurately feed required amounts of each size to comply with specifications and to maintain a balance of material in each of the hot bins. Conveyor belt that picks up the blended aggregate at the cold feed and feeds it to the dryer in a continuous flow. A revolving cylinder, usually from 1 to 3 meters in diameter and 6 to 12 meters long, in which aggregate is dried and heated. A fan in the unit furnishing the draft that controls the gas and air flow for the dryer combustion system and dust collection. Screens located between the dryer and hot bins which separate the heated aggregate into the proper hot bin sizes. Containers used to temporarily store heated and screened aggregate in the various size fractions required. Carries the hot, dried aggregate from the dryer and deposits it onto a screening unit (also called a screen deck or a plant screen). The depositing of finer material in a bin that should contain the next larger size aggregate. Chamber in which the batch is mixed and discharged into the truck or hauling unit. Finely divided mineral matter, such as rock dust, including limestone dust, slag dust, hydrated lime, hydraulic cement, or other suitable mineral matter. Reclaimed asphalt pavement. A weigh box or hopper in batch plants connected with scales, which weighs each aggregate fraction before dropping the aggregate into the pugmill. The time between the release of the dry batch into the pugmill and the release of the asphalt into the pugmill. The time between the release of the asphalt into the pugmill and the opening of the pugmill discharge gate. page 2 Chapter 5 VDOT and Platinum Performance Partners, LLC

69 Asphalt Concrete Plants The batch-type asphalt plant is a manufacturing facility for producing hot mix asphalt (HMA). A batch plant produces hot mix asphalt in 2 to 5 ton batches. Figure 5-1 is photo of a modern batch plant. Figure 5-1. Modern Batch Plant About 70% of all operational HMA plants in the U.S. are batch plants, while about 95% of all newly manufactured plants in the U.S. are drum plants (Roberts, et al., 1996). 1 Batch plants fall into three categories, depending on the degree of automation: Manual Operators use air or hydraulic cylinders actuated by electric switches to operate supply bin gates, feeders, asphalt valves, the weigh box discharge gate, and the pugmill discharge gate. Semi-automatic All operations are under automatic cycle control, including measuring and mixing, which frees the operator to coordinate other plant operations through remote control. Automatic All principal components of the plant are automatically controlled by electrical circuits, which operate from preset batch weight data without manual assistance or monitoring, removing the human error factor from the batching operation. Input to controls is a computer program, batch plug, or preset dials containing design weights for each batch. 1 Roberts, F.L., Kandhal, P.S., Brown, E.R., Lee, D.Y., and Kennedy, T.W. (1996). Hot Mix Asphalt Materials, Mixture Design, and Construction. National Asphalt Pavement Association Research and Education Foundation. Lanham, MD. VDOT and Platinum Performance Partners, LLC Chapter 5 page 3

70 Asphalt Concrete Plants Batch Plant Operation and Components An overview of the operation of a batch-type plant follows: 1. Coarse and fine aggregate is removed from storage, or stockpiles, in controlled amounts and passed through a dryer where it is heated and dried. 2. The aggregate then passes over a screening unit that separates the material into different size fractions and deposits them into bins for hot storage. 3. The aggregate and mineral, when used, are then withdrawn in controlled amounts, to make up one batch for mixing. 4. The entire combination of aggregate is dumped into a mixing chamber called a pugmill. Then the asphalt, which has also been weighed, is thoroughly mixed with the aggregate in the pugmill. 5. After mixing, the material is emptied from the pugmill in one batch. Figure 5-2 depicts the basic components of a batch-type plant. Each of the major components is further detailed in this section. Secondary collector Filler/ additive silo Hot elevator Batching Primary tower collector Asphalt storage tanks Pugmill Truck loading area Cold elevator Dryer/heater Truck loading area Control center Cold feed bins Aggregate Figure 5-2. Basic Components of a Batch Plant (Steve Muench, HMA Batch Plant 15 August 2007) page 4 Chapter 5 VDOT and Platinum Performance Partners, LLC

71 Asphalt Concrete Plants Aggregate Aggregate is an inert material such as sand, gravel, shell, slag, or broken stone, or combination of these materials. Aggregate is usually stored in stockpiles, but may be kept in silos or bunkers before being inserted into cold feed bins. Cold Feed Bins The cold aggregate feed is the first major operation in the batch-type asphalt concrete plant. The plant is equipped with multiple bins to handle different sizes of aggregates, as shown in Figure 5-3. Stockpiled aggregate is loaded into the cold feed bins for delivery to the aggregate dryer. The cold feeder may be charged or fed by one or a combination of the following methods: 1. Open top bins with two, three, or four compartments, usually fed by a crane with a clamshell bucket or a front-end loader, as illustrated in Figure 5-4. Figure 5-3. Cold Feed Bins 2. Tunnel under stockpiles separated by bulkheads. Materials are stockpiled over the tunnel by belt conveyor, truck, crane, or front-end loader. 3. Bunkers or large bins. These usually are fed by trucks, car unloaders, or bottom-dump freight cars. Each bin usually holds a separate aggregate size or gradation and has an adjustable gate that meters the aggregate onto the cold elevator. Some bins have extensions on the back sides to reduce the possibility of the loader operator overfilling the bins and materials overflowing from one bin to the other. Figure 5-4. Charging the Cold Feeder The cold aggregate feed is one of the critical control points in the production operation. While most of the problems in asphalt concrete production occur in the dryer, on the plant screen, in the bins, or in the pugmill, the causes can usually be traced back to the cold feed. VDOT and Platinum Performance Partners, LLC Chapter 5 page 5

72 Asphalt Concrete Plants AWARENESS/IMPORTANT When charging the cold feed, care should be exercised to minimize segregation and degradation of the aggregate. This can be prevented by taking the same precautions outlined for proper stockpiling. Highlights a step in the procedure which is either unusual or very particular to this procedure. May also indicate awareness (additional information) or a cautionary concern in the procedure. How the Feeders Work. Aggregate feeder units are located beneath the storage bins or stockpiles, or in positions that assure a uniform separation and flow of aggregate. Feeder units have controls that can be set to produce a uniform flow of aggregate to the cold elevator. An example is shown in Figure 5-5. Generally belt and vibratory feeders are best for accurate metering of the fine aggregates. Coarse aggregates usually flow satisfactorily with any type of feeder. For a uniform output from the asphalt concrete plant, input must be accurately measured. Figure 5-6 illustrates this operation. Figure 5-5. Feeder Unit Controls Figure 5-6. Aggregate Feeder Units SAFETY WARNING Stop the feeder unit during lubrication, maintenance, or adjustment. Describes a condition where personal safety may be at risk. page 6 Chapter 5 VDOT and Platinum Performance Partners, LLC

73 Asphalt Concrete Plants This is used to alert personnel to operating procedures & practices which, if not observed, may result in personal injury. Adding Lime When lime is to be used in asphalt concrete, it must be mixed by pugmill or other approved means to achieve a uniform lime coating on the aggregate prior to adding the asphalt cement to the mixture. The method of introducing and mixing the lime and aggregate is subject to approval by the Engineer prior to beginning production. Cold Elevator The cold elevator is a moving conveyor belt that transfers aggregate from the feed bins to the dryer. The degree to which the gates on the cold feed bin open, and the speed of the conveyor belt, control the amount of aggregate introduced into the plant. BEST PRACTICE The importance of feeding the exact amounts of each size aggregate into the dryer at the correct rate of flow cannot be overemphasized. Describes a best practice to be utilized when possible. Dryer/Heater One of the basic units in any asphalt concrete plant is the dryer. It is a necessary part of the hot-mix operation because it dries and heats aggregates coming from the cold feed supply, thus making them suitable for mixing with asphalt. The dryer is a large rotating metal drum mounted at an angle and equipped with a gas- or oil-heating unit at the lower end. Hot gases from the burner pass from the lower end of the rotating drum out through the upper end. Cold aggregate is fed from the cold elevator into the upper end of the dryer, as shown in Figure 5-7. Inside the dryer the aggregate is picked up by steel angles or flights mounted on the inside of the unit. As the drum rotates, the aggregate is lifted up and dumped through hot gases. Because of the inclination, the aggregate also gradually works its way toward the lower end of the dryer. The hot aggregate then discharges from the lower end onto a hot elevator that carries it to the screens and hot storage. Figure 5-7. Aggregate Entering the Dryer VDOT and Platinum Performance Partners, LLC Chapter 5 page 7

74 Asphalt Concrete Plants Drying is the most expensive operation in mix production. It is also the most frequently encountered bottleneck in the plant operation. The best dryer is the one that meets a desired performance level at the lowest investment and operating cost. Most dryers are designed for average aggregate moisture content. Very wet aggregate will reduce the dryer capacity and require corrective measures. Drying Aggregate The aggregate shall be dried to a point at which the moisture content of the completed mixture does not exceed 1 percent as determined from samples taken at the point of discharge from the mixing operation. Temperature Control and Indicating Devices. Proper aggregate temperature is essential. The temperature of the aggregate, not the binder, controls the temperature of the hot mix asphalt. The layer of binder put on each particle of aggregate during mixing assumes the temperature of that aggregate almost instantaneously. Overheating of the aggregates can damage the asphalt by hardening the binder during mixing. Underheated aggregates are difficult to coat thoroughly with binder, and the resulting mix is difficult to place on the roadway. Aggregate temperature is measured by either a thermometer or a thermocouple attached to an indicating pyrometer. Pyrometers react much faster to changes in temperatures and are usually preferred. The pyrometer monitors the aggregate temperature as the material leaves the dryer, as suggested by its placement in Figure 5-8. Figure 5-8. Pyrometer Placement TOOLS AND EQUIPMENT An aggregate temperature measuring device should be installed in the dryer discharge in full view of the burner operator. This device is one of the most important plant control accessories and should be a reliable and accurate instrument. Describes what tools, equipment and tests are required to complete the job safely and with the highest level of quality. page 8 Chapter 5 VDOT and Platinum Performance Partners, LLC

75 Asphalt Concrete Plants Emissions Control System All batch and drum mix plants have a significant amount of fine aggregate and dust created from the drying process. In order to meet federal and state air quality codes, emission control equipment is necessary to capture particulate emissions that might otherwise be released into the atmosphere. In addition, some emission control devices permit the plant operator to collect and return these fines back into the mixture. The emissions control system is also known as the dust collector. The collector eliminates or abates the dust nuisance that might result from exhaust air from the dryer. The dust collector is generally operated adjacent to and in conjunction with the dryer, and is necessary for efficient plant operation. Provisions are usually made in the dust collecting system to return the collected dust back to the hot aggregate as it emerges from the dryer and is picked up by the hot elevator. If the collected dust is unsuitable for use in the asphalt concrete mixture, it may be removed from the collector and wasted. The dust collector is comprised of the two main components listed below; each of these is described in more detail in the text that follows. The Primary (Multicone) Collector The Secondary Collector (Baghouse) The Primary (Multicone) Collector. The primary collector, also known as the multicone collector, is located between the dryer and the secondary collector. Figure 5-9 shows the primary dust collector associated with a counter-flow drum plant. The primary collector uses a cyclone effect to collect larger dust particles and fine aggregate from the exhaust gases before they enter the more effective secondary collector. It is typically available as a knockout box, cyclone, multiple cyclone, or multicone collector. In any case, the collector s fan furnishes the draft that draws the flame and hot gases through the Figure 5-9. Primary Collector dryer. Dust particles from the dryer and other parts of the plant are also carried in the current of draft air, which enters the dust collector at the upper end and goes into vertical motion. The heavier dust particles in the air stream are separated by centrifugal force into the collector shell and fall to the bottom. The finer dust may remain in suspension and be carried out the exhaust stack with the air. VDOT and Platinum Performance Partners, LLC Chapter 5 page 9

76 Asphalt Concrete Plants The Secondary Collector (Baghouse). The exhaust gases that pass through the primary collector are pulled by the exhaust fan through cylindrical fabric filter bags in the baghouse. The baghouse removes the fine particulate matter from the dryer exhaust gasses before the exhaust gasses are released to the atmosphere. With the use of a baghouse, fines can be reclaimed and returned to the mixing unit. Some plants may use a wet scrubber or wet wash system as a secondary collector to reduce the amount of fine dust being carried out the exhaust stack with the air. There are several types of wet systems, but they all usually consist of a short tower, with or without baffles. Exhaust from the dust collector enters the tower at the bottom and passes upward through a series of water sprays that remove the dust. Use of a wet wash system usually will increase fan requirements by 10 to 15% because of the pressure loss in the tower. Hot Elevator The hot elevator takes the heated, dried aggregate from the aggregate dryer and deposits it onto a screen deck (also called a screening unit) that is mounted over the plant bins inside of the batching tower. Figure 5-10 depicts a hot elevator. Figure Hot Elevator page 10 Chapter 5 VDOT and Platinum Performance Partners, LLC

77 Asphalt Concrete Plants Batching Tower/Mixing Tower Figure 5-11 is an example of a batching tower, which is sometimes referred to as the mixing tower. The hot, dry aggregate enters the batching tower from the hot elevator. Inside the batching tower are the following components, each of which will be discussed in more detail: Screening deck and screening unit Hot aggregate holding bins, also known as hot bins Asphalt weigh hopper Weigh bucket Pugmill The batching tower divides the hot aggregate into fractions, depending on their size, and prepares batches for loading onto trucks. Screen Deck and Screening Unit. The screen deck and screening unit is one of the major components of the batching tower. Aggregate is discharged from the hot elevator over a series of vibrating screens in the batching tower. The screens in the screen deck separate the aggregate into various specified sizes. When the screening is complete, each size of aggregate resides in its own bin. Figure Example of a Batching Tower Figure 5-12 illustrates how aggregate flows through a typical screen deck with four screens. VDOT and Platinum Performance Partners, LLC Chapter 5 page 11

78 Asphalt Concrete Plants Figure Flow of Material through a Typical Screen Deck The screens are critical to the plant s ability to produce mixtures that are uniform and to specification. To properly perform the screening function, the screening area must be large enough to handle the maximum feed. INSPECTION AND MEASUREMENTS Screen capacity The capacity of the screens should be checked against the capacity of the dryer to ensure the size is appropriate. The technician also should observe the screens in operation to be sure they can handle the maximum feed. Describes inspection, Quality Assurance and/or Quality Control practices. page 12 Chapter 5 VDOT and Platinum Performance Partners, LLC

79 Asphalt Concrete Plants If the effective screening area is reduced by plugged screen openings, or if more material is fed to the screens than they can handle, the usual result is carry-over. Carry-over is the depositing of finer material in a bin that should contain the next larger size aggregate. When carry-over fluctuates, lack of uniformity in the aggregate gradation will cause a corresponding lack of uniformity in the mixture. Carry-over increases the amount of fine aggregate in the total mix, and since fine aggregate has much more surface area per unit of weight requiring asphalt coating, this condition should be kept at a minimum. Excessive carry-over, or its fluctuations, will be apparent from the sieve-analysis made from the contents of the individual hot bins. INSPECTION AND MEASUREMENTS Screen inspection The condition and cleanliness of the screens will, to a large extent, control their efficiency. Excessive wear of the screen wire causes enlarged openings resulting in oversize material in the bin. Daily visual inspection of the screens for cleanliness is recommended, preferably before the start of the day s operations. Describes inspection, Quality Assurance and/or Quality Control practices. Hot Aggregate Holding Bins/Hot Bins. Hot bins are used to temporarily store heated and screened aggregate in the various size fractions required until the predetermined amount of aggregate size is accumulated for a batch. Figure 5-13 depicts a set of hot bins. Hot bin partitions should be tight, free from holes, and of sufficient height to prevent intermingling of aggregates. Each bin should be large enough to prevent depletion of the material when the mixer is operating at full capacity. Figure Hot Bins Each bin should have an overflow pipe to prevent aggregate from backing up into the other bins. The overflow pipe also prevents overfilling to the point where the vibrating screen will ride on the aggregate. If this were to happen, it would result in a heavy carry-over and probably damage the screens. INSPECTION AND MEASUREMENTS Inspecting overflow vents Inspect the overflow vents frequently to make sure that they are free flowing and thus preventing contamination by the intermingling of contents from adjacent bins. Describes inspection, Quality Assurance and/or Quality Control practices. VDOT and Platinum Performance Partners, LLC Chapter 5 page 13

80 Asphalt Concrete Plants The correctly proportioned aggregate from each hot bin is discharged into the weigh hopper. Material is withdrawn from the hot bins in predetermined proportions and at a specified rate. A balanced flow of aggregate is being achieved if the level of aggregate in hot storage has little variation during plant operation. Aggregate Weigh Hopper. Aggregates are released from the hot bins into the weigh hopper, generally beginning with the largest size aggregate and progressing down to the finest size, with the mineral filler (if used) sandwiched between the larger aggregates. The amount from each bin is determined by the batch size and the proportions or percentages required to be blended. The weigh hopper is suspended from a scale beam and the amounts of aggregate weighed cumulatively. AWARENESS/IMPORTANT Before withdrawing material to be weighed, there should always be sufficient materials in the hot bins for a complete batch. If a bin is near depletion or is running over, chances are that an adjustment in the cold feed is required. Highlights a step in the procedure which is either unusual or very particular to this procedure. May also indicate awareness (additional information) or a cautionary concern in the procedure. Weigh Hopper and Bucket. Asphalt may be weighed in a special bucket, or it may be measured by a meter for each batch. When weighed into a batch, asphalt is pumped into a bucket of known weight and weighed on a scale. When metering devices are used, a volumetric measurement is made. The volume of asphalt changes with temperature. Some asphalt meters have built in temperature-compensating devices that correct the flow of asphalt when changes in temperature occur. Note: The volume of asphalt pumped between two-meter readings may be weighed as one means of calibrating the meter. Pugmill. The aggregate and asphalt cement are blended together in the pugmill. Blending is done in batches, giving the batch plant its name. Pugmills typically have a capacity of 2 to 5 tons per batch. A twin pugmill-type mixer is commonly used in all modern asphalt concrete plants. In a batch plant this unit is mounted directly beneath the weigh box and asphalt bucket, and high enough so that it may discharge the mixture into the truck or other hauling unit. Figure 5-14 depicts mixing paddles within the pugmill. Figure Pugmill Mixing Paddles page 14 Chapter 5 VDOT and Platinum Performance Partners, LLC

81 Asphalt Concrete Plants When aggregates are drawn from the hot bins, some dry mixing takes place as the materials are deposited in the weigh hopper, as well as in the pugmill. The wet mixing time begins with the start of the flow of asphalt from the bucket or meter, as illustrated in Figure The gates of the weigh box are opened and the aggregates empty into the pugmill 3. The aggregates and the asphalt are mixed 5. The pugmill gate closes to receive the next batch. 2. The asphalt is discharged into the pugmill by a spraybar 4. The pugmill gate opens and the finished product is discharged. Figure Steps in Typical Batch Plant Mixing Cycle Asphalt film on the aggregate is hardened by exposure to air and heat. The Engineer may require a dry mixing time of up to 15 seconds. However, the wet mixing cycle shall not be less than 20 seconds. See the Ross Count Procedure, (page 5-26) for details on how to establish pugmill mixing times. Upon completion of the mixing time, the bottom of the pugmill mixer opens up and discharges the contents into a truck or other hauling equipment. AWARENESS/IMPORTANT The mixing time should be no longer than necessary to get a uniform distribution of aggregate sizes and a uniform coating of asphalt on all aggregate particles. Highlights a step in the procedure which is either unusual or very particular to this procedure. May also indicate awareness (additional information) or a cautionary concern in the procedure. VDOT and Platinum Performance Partners, LLC Chapter 5 page 15

82 Asphalt Concrete Plants Asphalt Storage Tanks Asphalt is stored in tanks such as those shown in Figure 5-16 while awaiting delivery into the pugmill, where it is mixed with the aggregate (as the second step in Figure 5-15 illustrated). Asphalt storage at the plant should be equal to one day s output, and storage tanks should be calibrated so the amount of material remaining in the tank can be determined at any time. Since asphalt must be fluid enough for movement through the delivery and return lines, it must be heated. Heating may be done by the circulation of steam or hot oil through coils in the tank, or it may be done electrically. Figure Asphalt Storage Tanks Asphalt cement in the tanks is kept heated between 150 C (300 F) to 180 C (350 F), depending on the grade and type of asphalt. INSPECTION AND MEASUREMENTS Inspecting the hot oil level If the asphalt temperature is maintained by circulating hot oil, the hot oil level in the reservoir of the heating unit should be inspected frequently. If the level falls, a check should be made for leakage of the hot oil into the stored asphalt. Describes inspection, Quality Assurance and/or Quality Control practices. Truck Loading and Plant Scales Trucks can be loaded directly from the pugmill after mixing has been completed. Weigh scales are located in the truck loading area to ensure trucks are loaded with the correct amount of mix. Scales used in the weighing of materials paid for on a tonnage basis shall be approved and sealed in accordance with the requirements of the policies of the Bureau of Weights and Measures of the Department of Agriculture and Consumer Services, or other approved agencies, at least once every six months and anytime they are moved. Hopper and truck scales shall be serviced and tested by a scale service representative at least once every six months. Hopper scales shall be checked with a minimum 500 pounds of test weights. Truck scales shall be checked with a minimum of 20,000 pounds of test weights (see Section ). page 16 Chapter 5 VDOT and Platinum Performance Partners, LLC

83 Asphalt Concrete Plants INSPECTION AND MEASUREMENTS Truck bed The bed of the haul truck should be clean and free of all deleterious materials before mix is placed in it. The bed should be reasonably smooth and free from any holes. Trucks must also be equipped with a tarpaulin to prevent contamination of material during transportation to the job site and to prevent some heat loss. Describes inspection, Quality Assurance and/or Quality Control practices. Filler/Additive Silo (Hopper) Some plants may have one or more silos for storing mineral filler, fine particles from the baghouse, or special additives that are added to the mix. Some asphalt concrete plants often have a separate feeding system for the addition of mineral filler to the mix. The mineral filler is supplied in paper sacks or in bulk. The filler is placed into a ground-mounted feeder and conveyed into a surge hopper, where it is added to the aggregate as it leaves the hot bins. Mineral filler is added as an unheated material. AWARENESS/IMPORTANT When filler is used, the hopper must be emptied at the end of the day and kept dry to prevent caking of the filler. Highlights a step in the procedure which is either unusual or very particular to this procedure. May also indicate awareness (additional information) or a cautionary concern in the procedure. RAP Bin Reclaimed asphalt pavement (RAP) is the term given to removed and/or reprocessed pavement materials containing asphalt and aggregates. When properly crushed and screened, RAP consists of highquality, well-graded aggregates coated by asphalt cement. These materials may be added into mixes. There are several methods of batch plant recycling. RAP is typically added to heated aggregates. This is most commonly done by introducing RAP from a separate bin and feeding it into the pugmill or weigh hopper via conveyor belt or chutes. Storage Silos Batch plants do not require a silo, but often have them to increase plant production. Drum mix plants must have silos since they produce asphalt continuously. VDOT and Platinum Performance Partners, LLC Chapter 5 page 17

84 Asphalt Concrete Plants Control Center (Control House) The Control Center controls plant operations from one central location. Figure 5-17 provides an example of the kinds of equipment and controls common to these operations centers. Figure Control Center page 18 Chapter 5 VDOT and Platinum Performance Partners, LLC

85 Asphalt Concrete Plants Drum Plant The following terms will be used throughout this section: Drum-type asphalt plant A manufacturing facility for producing HMA. It manufactures HMA continuously, rather than in batches. Surge silos Silos that are usually insulated, but unheated and are designed to hold hot mix for short periods of time (up to several hours) between truck arrivals. Storage silos Silos that are well insulated, heated, near air tight, and are designed to hold hot mix for long periods of time (up to one week). A drum-type mix plant is a manufacturing facility for producing hot mix asphalt (HMA). It manufactures HMA continuously, rather than in batches. A modern drum mix plant is shown in Figure Figure Modern Drum Mix Plant VDOT and Platinum Performance Partners, LLC Chapter 5 page 19

86 Asphalt Concrete Plants Drum Plant Operation and Components Drum mixing is a relatively simple process of producing asphalt mixtures. The mixing drum looks like the familiar dryer. The difference is that the aggregate is not only dried and heated within the drum, but it is also mixed with the asphalt cement in the drum. The drum mix plant also requires the use of a surge silo for mix loadout. Drum mixers can produce a true hot mix, or a low temperature mix. Drum plants share many of the components with the batch plant, including: Cold feed bins To accurately meter the different aggregates used in the mix to the drying drum Asphalt cement storage Aboveground tanks for asphalt cement storage that must meet stringent regulatory guidelines Dryer drum/mixer To dry out and heat aggregates by tumbling them through hot air Emission control systems To trap and remove fine sand and dust particles and return them to the mix RAP bins Bins containing removed and/or processed pavement materials containing asphalt and aggregates Hot mix conveyor For moving the hot mix asphalt to the storage silos Truck loading area Where trucks are loaded with asphalt for jobs Control center For controlling plant operations In addition, operation of the drum plant depends on components shown in Figure Figure Basic Components of a Drum Plant (Steve Muench, HMA Drum Plant 15 August 2007) page 20 Chapter 5 VDOT and Platinum Performance Partners, LLC

87 Asphalt Concrete Plants Cold Feed Bins As with the batch plant, production in the drum plant starts with the cold feed bins. The plant is equipped with multiple bins to handle different sizes of new aggregates. A bulkhead or divider is used between each bin to prevent overflow of one aggregate into an adjacent bin, as Figure 5-20 illustrates. Contamination of different size aggregates can significantly alter the gradation of the mix being produced. At this point of production, good quality control over the aggregates is especially critical. Figure Cold Feed Bins with Dividers AWARENESS/IMPORTANT The aggregates in each stockpile should be consistent as to gradation. Stockpiles must be separated properly to prevent contamination of one aggregate by one of another gradation. Highlights a step in the procedure which is either unusual or very particular to this procedure. May also indicate awareness (additional information) or a cautionary concern in the procedure. The drum mix process depends upon cold feed control for proportioning and gradation of aggregates. Ingredients must be added in required proportion. The proportioning is even more important to the drum-type plants than to batch-type plants. Some cold feed bins are equipped with a gate to control the size of the discharge opening. This will set the amount of the material used from that bin. Total and proportional control with variable speed belt feeders permits adjustments of individual feeder output to desired proportions, as Figure 5-21 illustrates. The speed of the belt can be used to control the amount of material to be used. The speed setting for each individual belt feeder is adjusted independently to allow the proper amount of aggregate to be pulled from each individual bin. VDOT and Platinum Performance Partners, LLC Chapter 5 page 21

88 Asphalt Concrete Plants Figure Cold Feed Bin Control Cold Feed Conveyor and Weigh Bridge From the cold feed, the aggregate moves up an incline conveyor over the weigh bridge, which continually weighs the aggregate passing over the belt and indicates the flow of material over the scale at any given instant. A computer calculates the tons of aggregate transported to the dryer by the accumulated weight over the load cell, as illustrated in Figure The weight reading is the foundation of the aggregate/asphalt blending system. The asphalt metering and delivery system must be interlocked with the aggregate weigh system to Figure Weigh Bridge and Belt Scales assure that the precise asphalt content is achieved and maintained in the mix. The tonnage rate of aggregate going into the drum mixer, as measured by the weigh bridge, is regarded as the base figure of the total mix formula. page 22 Chapter 5 VDOT and Platinum Performance Partners, LLC

89 Asphalt Concrete Plants Since the base reading reflects the mass of both the aggregate and moisture, the weight of the moisture must be subtracted to arrive at a true aggregate rate reading. Actual moisture content is determined by periodic moisture extraction test. (How to determine moisture content is detailed on p ) AWARENESS/IMPORTANT The base figure of the total mix formula reflects total mass of both aggregate and moisture. Highlights a step in the procedure which is either unusual or very particular to this procedure. May also indicate awareness (additional information) or a cautionary concern in the procedure. Drum Mixer From this point, the aggregates go into the drum mixer, an example of which is shown in Figure The hottest gases and flame exist at the charging end of the drum mixer. Thus, the asphalt is protected from the harmful effects of oxidation and direct contact with the burner flame by the evaporating moisture on the aggregate. Figure Drum Mixer VDOT and Platinum Performance Partners, LLC Chapter 5 page 23

90 Asphalt Concrete Plants While the drum mix process features a smooth continuous flow of material, inside the drum mixer certain events occur in phases within fairly well delineated zones of the drum mixer. One of the principle differences between the conventional batch method of mix production and drum mixing is how the aggregate is coated. Heating and mixing of the aggregates and asphalt cement is done in four phases, as described in the table that follows. Heating/Mixing Phase Description Primary Secondary Phase I Phase II Phase III The aggregate has entered the drum mixer. In the early heating phase, surface and free moisture begin to leave the aggregate as temperature rises. Most of the heat rise occurs in phase II as aggregate temperatures reach approximately 170 to 180 F (77 to 82 C). The majority of the moisture is driven off in this phase and the rate of increase in mixing temperature levels off. As mix temperature reaches between 180 and 200 F (82 and 93 C) asphalt is introduced to the mix. Moisture driven off now causes the asphalt to foam. This foaming action causes the surface area of the asphalt to be greatly enlarged, thus entrapping dust as well as larger particles and coating the aggregate rapidly. Thus, aggregate coating in a drum mixer is not a function of asphalt being forcibly mixed, but rather of the aggregate particles being engulfed by the foaming, rapidly spreading asphalt. Phase IV Most of the moisture has been removed. The aggregate has been coated, and mix temperatures will continue to rise until desired temperature is reached. Hot Elevator After the mix temperature has been achieved, the mix is discharged into a hot incline elevator that carries the mix to either a surge silo or storage tank, where it is held at a constant temperature. Storage Silos The main purpose of the storage silo is to hold the mix temporarily until the next transport vehicle is available. There are two types of silos: surge and storage. Surge silos are usually insulated, but unheated and are designed to hold hot mix for short periods of time (up to several hours) between truck arrivals. Figure 5-24 depicts a surge silo. Storage silos are well insulated, heated, near air tight, and are designed to hold hot mix for long periods of time (up to one week). AWARENESS/IMPORTANT Coarse graded mixtures should not be stored for long periods of time because the asphalt cement will tend to flow off the aggregate (drain down) and collect at the bottom. Highlights a step in the procedure which is either unusual or very particular to this procedure. May also indicate awareness (additional information) or a cautionary concern in the procedure. page 24 Chapter 5 VDOT and Platinum Performance Partners, LLC

91 Asphalt Concrete Plants Figure Surge Silo SAFETY WARNING Care should be taken during the transport of hot mix asphalt from the drum mixer to the silo and from the silo to trucks to ensure the safety of personnel. Describes a condition where personal safety may be at risk. This is used to alert personnel to operating procedures & practices which, if not observed, may result in personal injury. VDOT and Platinum Performance Partners, LLC Chapter 5 page 25

92 Asphalt Concrete Plants Special Procedures This section presents two important procedures used in asphalt plants: the Ross Count Procedure (particle coating) for batch plant mixing, and the procedure for determining aggregate moisture for drum mix operations. The Ross Count Procedure for Establishing Batch Mixing Times In establishing pugmill mixing times in a batch plant by the Ross Count Procedure, it is necessary first to become familiar with two definitions involved: Dry Mixing Time The time between the release of the dry batch into the pugmill and the release of the asphalt into the pugmill. Wet Mixing Time The time between the release of the asphalt into the pugmill and the opening of the discharge gate. See the table below for more detail on mixing times. The purpose of establishing a mixing time in this manner is to permit the operation of the asphalt concrete plant with the least mixing time cycle that is consistent with the production of a mix in which: The coarse particles are completely coated The gradation requirements are being met Other factors are satisfied. Mixing Times Wet Mixing Time Dry Mixing Time The wet mixing time may vary from plant to plant, from mix to mix, and with the condition of the mixing equipment. This procedure for establishing mixing times permits more economical mixing operations to the benefit of the Department of Transportation and the Contractor. The wet mixing cycle shall not be less than 20 seconds. A dry mixing time of up to 15 seconds may be required by the Engineer to accomplish the degree of aggregate distribution necessary to obtain complete and uniform coating of the aggregate with bitumen. The lowest mixing time possible, that will still produce a mix that meets all Department requirements, should be used (See VDOT Road and Bridge Specifications). page 26 Chapter 5 VDOT and Platinum Performance Partners, LLC

93 Asphalt Concrete Plants How to Conduct the Ross Count Procedure Following is an outlined procedure for determining minimum mixing time by the Ross Count Procedure (see AASHTO T 195). To start the determination of the mixing time, the plant should operate on a 30- second wet mixing cycle. If the asphalt introduction requires more than 30 seconds, use this time. STEP 1. Take a sample at the plant site from three alternate truckloads. STEP 2. Sieve the sample immediately, while it is still hot, through a 3/8 in (9.5 mm) sieve, or through No. 4 sieve (4.75 mm) for Surface Mixes (SM). STEP 3. Take a sample large enough to yield between 200 and 500 coarse particles on the 3/8 in (9.5 mm), or No. 4 (4.75 mm) sieve. AWARENESS/IMPORTANT Do not overload the sieves during the sampling step. If necessary, sieve the sample in two or three operations. The individual sieving operations should not require more than 20 seconds of manual shaking. Highlights a step in the procedure which is either unusual or very particular to this procedure. May also indicate awareness (additional information) or a cautionary concern in the procedure. STEP 4. Very carefully examine each particle. If even a tiny speck of uncoated stone is noted, classify the particle as partially coated. If completely coated, classify the particle as completely coated. STEP 5. Compute the Ross Count as below: Ross Count = Number of Completely Coated Particles X 100 Total Number of Particles STEP 6. Use the decision table that follows to determine what to do with the results: IF AND/OR THEN IF the average of the three (3) samples is greater than 95%... IF the average of the three (3) samples is less than 95%... AND no one (1) sample is less than 92%... OR any one sample (1) is less than 92%... THEN a lower mix time can be tried. Lower time by five (5) seconds. THEN increase the mix time by five (5) seconds. VDOT and Platinum Performance Partners, LLC Chapter 5 page 27

94 Asphalt Concrete Plants Aggregate Moisture Determination for Drum Mix Operation Since aggregate in a drum mix operation is weighed before drying, moisture content of the aggregate must be determined. The weighing of aggregate and the metering of asphalt cement are interlocked electronically in drum mix operations. To ensure proper metering of asphalt cement, adjustments for aggregate moisture must be made. The moisture content of the aggregate should be determined, and proper allowance made for the water content, prior to mixing. AWARENESS/IMPORTANT Perform moisture determination prior to start of mixing and thereafter as changes occur in the condition of the aggregate. Highlights a step in the procedure which is either unusual or very particular to this procedure. May also indicate awareness (additional information) or a cautionary concern in the procedure. How to Determine the Moisture Content of Aggregate To establish the moisture content of aggregate being used, it is first necessary to secure a representative sample of the aggregate. When sampling, it is easier to obtain a representative sample from the production stream (i.e., from the conveyor belt), than from storage bins or stockpiles. When taking the sample from the conveyor belt, remove it from the entire cross-section of the belt. The size of the sample taken is determined by the maximum size aggregate. The steps for this procedure are outlined as follows: STEP 1. Obtain a representative sample of the material from the production line (conveyor belt). STEP 2. Reduce the sample to a size that can be handled by the weighing device by either a sample splitter or the quartering method. STEP 3. Weigh the aggregate sample and record the weight (wet weight). STEP 4. Dry the aggregate sample thoroughly. The sample or samples should be dried to constant weight on a hot plate or in an oven at a temperature of 230 ºF (110 ºC). STEP 5. Accurately weigh the dried sample and record the weight (dry weight). In weighing and handling the sample, extreme care must be taken to avoid any loss of the material, as this will affect the accuracy of the results. STEP 6. Determine moisture content. The percent moisture is determined by the following formula: Moisture Content = Wet Weight Dry Weight X 100 Dry Weight page 28 Chapter 5 VDOT and Platinum Performance Partners, LLC

95 Asphalt Concrete Plants Example: Wet Weight of Sample = 1225 g Dry Weight of Sample = 1175 g Moisture Content = Wet Weight Dry Weight x 100 Dry Weight Moisture Content = x 100 = 4.3% 1175 How to Determine the Moisture Content of Asphalt Concrete Mixtures The moisture content of an asphalt concrete mixture can also be determined. The procedure is similar to the aggregate moisture determination procedure. The steps are outlined as follows. STEP 1. Place the mixture in the pan. STEP 2. Weigh the pan and mixture together. Then record the wet weight. STEP 3. Place the pan and mixture in the oven (set at compaction temperature) for approximately 30 minutes. STEP 4. Take a sample from the oven and weigh it, then record this weight. STEP 5. Place the sample back in oven for approximately 15 minutes. STEP 6. Take the sample from oven and weigh it, then record this dry weight. (Repeat steps 5 and 6 until the sample reaches a constant weight.) STEP 7. After a constant weight has been established, determine the percent of moisture using the following formula: Moisture Content = Wet Weight Dry Weight X 100 Dry Weight AWARENESS/IMPORTANT NOTE: This test may be performed on aggregate blends also. The moisture content of an asphalt mixture should not exceed 1%. Highlights a step in the procedure which is either unusual or very particular to this procedure. May also indicate awareness (additional information) or a cautionary concern in the procedure. VDOT and Platinum Performance Partners, LLC Chapter 5 page 29

96 Asphalt Concrete Plants Types of Trouble at the Plant and Probable Causes Type of Trouble at the Plant Extraction Fails to Check With Set-Up Variation in Batch Color Brown, Dead Appearing Mix Rich, Glistening Mix Appearance Mix Gradation Fails to Check Set- Up Lifeless, Greasy Appearing Mix Mix Temperature Too High Smoking Batches Steaming Batches Overweight or Underweight Loads Portion of Batches Unmixed Variations in Batch Gradation Faulty Extractions X X X Overrated Screen Capacity X Too Little Oil X X Too Much Oil X X Oil Temperature Too High X X Moisture Tests Not Representative X X Improper Set on Pugmill Blades X X Slope or Speed of Dryer Drum X X Faulty Mechanical Analysis X X X Physical Characteristics of Aggregate X X X Sampling Methods Not Uniform X X X X Overrated Dryer Capacity X X X Faulty Gate Mechanism X X X Drum Feed Not Uniform X X X X High Soft-Absorbent Stone Content X X X X Excessive Moisture Content X X X X Aggregate Temperature Too High X X X X Burner Pressure Not Uniform X X X X Pyrometer Not Functioning Properly X X X X X X Mixing Time Not Uniform X X X X X Platform Scales out of Adjustment X X X X X Oil Scales out of Adjustment X X X X X Improper Bin Division X X X X X X Segregation in Bins X X X X X X Segregation in Aggregate Stockpile X X X X X X page 30 Chapter 5 VDOT and Platinum Performance Partners, LLC

97 Asphalt Concrete Plants Type of Trouble at the Plant, continued Extraction Fails to Check With Set-Up Variation in Batch Color Brown, Dead Appearing Mix Rich, Glistening Mix Appearance Mix Gradation Fails to Check Set- Up Lifeless, Greasy Appearing Mix Mix Temperature Too High Smoking Batches Steaming Batches Overweight or Underweight Loads Portion of Batches Unmixed Variations in Batch Gradation Return from Dust Collector Not Constant X X X X X X More than One Aperture Per Bin X X X X X X Bin Overflow Pipes Not Functioning X X X X X X Dust Feed Not Uniform X X X X X X X Scale Gradation Not Clearly Visible X X X X X X X Bridging of Materials in Weigh Box X X X X X X X Batch Scales Out of Adjustment X X X X X X X Weather Conditions X X X X X X X X X X X VDOT and Platinum Performance Partners, LLC Chapter 5 page 31

98 Asphalt Concrete Plants Chapter Five Knowledge Check 1. The overflow chutes on a batch plant are used to: A. Transfer material from one bin to another B. Prevent contamination by intermingling from adjacent bins C. Collect aggregate samples for gradation D. Decrease production 2. The asphalt material shall be delivered into the mixer in a thin, uniform sheet or multiple streams for the full width of the mixer. A. True B. False 3. Increasing the dryer time will remove more moisture than increasing the heat. A. True B. False 4. The asphalt content for batch weight calculations is obtained from the: A. Design range B. Job mix formula C. Acceptance range D. None of the above 5. During the drying operation, wet aggregate will reduce the dryer s capacity. A. True B. False 6. In the drum mix plant, moisture content of aggregate must be determined before drying. A. True B. False 7. The maximum amount of moisture allowed in the completed mixture is: A. 10% B. 1% C. 2% D. 5% page 32 Chapter 5 VDOT and Platinum Performance Partners, LLC

99 Asphalt Concrete Plants 8. What conditions affect screening efficiency? 9. What are some of the methods of controlling carry-over? 10. What is meant by proportioning of aggregates and asphalt? 11. What conditions will best insure a uniform flow of the proper aggregate sizes from the cold feed? 12. Why is proper cold feeding essential? 13. When hydrated lime is used in asphalt concrete as an anti-stripping additive, it shall be added at what rate? 14. What problems arise from overheating aggregate? 15. What problems arise from underheating aggregate? 16. What could cause leakage of aggregate into the weigh hopper after the desired amount has been withdrawn? 17. How often and by whom should hopper and truck scales be serviced and tested? 18. How often and by whom shall the scales used in the weighing of materials paid for on a tonnage basis be approved and sealed? 19. When using a metering device instead of a weigh bucket for proportioning asphalt to the mixer, what is one important thing that should be remembered? VDOT and Platinum Performance Partners, LLC Chapter 5 page 33

100 Asphalt Concrete Plants 20. What is the maximum dry mixing time for aggregates released into the pugmill? 21. What is the minimum wet mixing time allowed? 22. Who determines the mixing time? Who approves the mixing time? 23. Asphalt storage at the plant should be equal to at least: A. One-half of one day s output B. One day s output C. Two day s output D. Three day s output page 34 Chapter 5 VDOT and Platinum Performance Partners, LLC

101 Asphalt Concrete Plants Problem No. 1: Establishing the Wet Mixing Time Given: The plant is operating on a 22-second wet mixing cycle. Two previous determinations yielded results of 94.3% and 95.1% completely coated particles. The third determination has shown that of the 230 particles there are 6 that are not completely coated. Find: 1. The Ross Count for the third determination. 2. Does this meet the VDOT requirements for the wet mixing time? 3. What steps are taken if after conducting a Ross Count, the results do not meet VDOT requirements? Problem No. 2: Establishing the Wet Mixing Time Given: The plant is operating on a 21-second wet mixing cycle. Two previous determinations yielded results of 95.3% and 92.5% completely coated particles. The third determination has shown that of the 216 particles there are 14 that are not completely coated. Find: 1. The Ross Count for the third determination. 2. Does this meet the VDOT requirements for the wet mixing time? 3. What steps are taken if after conducting a Ross Count, the results do not meet VDOT requirements? VDOT and Platinum Performance Partners, LLC Chapter 5 page 35

102 Asphalt Concrete Plants Problem No. 3: Determining Aggregate Moisture Determine the percent moisture in an aggregate sample that had a wet weight of 1335 grams and, after drying, a dry weight of 1290 grams. (Answer to nearest tenth of one percent.) Problem No. 4: Determining Aggregate Moisture Determine the percent moisture (to nearest tenth of one percent) in an aggregate sample that had a wet weight of 1275 grams and, after drying, a dry weight of 1235 grams. page 36 Chapter 5 VDOT and Platinum Performance Partners, LLC

103 MCS: Asphalt Plant Certification Problem No. 5: Determining Moisture of an Asphalt Mixture Given the following information, determine the percent moisture in the BM-25.0 asphalt concrete sample below. Does this meet the VDOT Specifications? Weight of Moist Sample Weight of Dry Sample = 2254 g = 2232 g Problem No. 6: Determining Moisture of an Asphalt Mixture Given the following information, determine the percent moisture in the BM-25.0 asphalt concrete sample below. Does this meet the VDOT Specifications? Weight of Moist Sample Weight of Dry Sample = 2376 g = 2342 g VDOT and Platinum Performance Partners, LLC Chapter 5 page 37

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105 MCS: Asphalt Plant Certification 6 Sampling and Analysis of Aggregate Most of the material in an asphalt concrete mixture is aggregate. The aggregate contributes strength and stability to the completed pavement. The particle size distribution, or gradation, of an aggregate is one of the most influential aggregate characteristics in determining how it will perform as a pavement material. In hot mix asphalt, gradation helps determine almost every important property (e.g., stability, workability). Sampling is the process of obtaining a small, unbiased portion of an aggregate that is large enough to provide meaningful results in sieve analysis or other tests. Sampling is important because it allows us to understand the grading and other characteristics of aggregates. This enables us to ensure, through analysis, that the material meets specifications for a particular job. Learning Objectives: Upon completion of this chapter, you should be able to: Discuss why aggregates must be sampled prior to sieve analysis Describe procedures for sampling at the source and from a stockpile Demonstrate the procedure for conducting sieve analysis Calculate percentage retained and passing VDOT and Platinum Performance Partners, LLC Chapter 6 page 1

106 Sampling and Analysis of Aggregate Sampling Aggregates We sample and analyze aggregates to ensure that the material will meet the specifications for a particular job. When sampling aggregates, it is important that you first obtain a representative sample with which to work. Unless it is truly representative, the sieve analysis test results apply to the sample only and not to the entire aggregate shipment or stockpile. DEFINITIONS. The following terms will be used throughout this section: Gradation Representative sample Sieve analysis Fine aggregate Coarse aggregate Washed sieve analysis Sample splitter Particle size distribution in an aggregate, which helps determine the properties of pavement materials. A relatively small portion of material having the physical and chemical properties as the group or lot from which it is taken. The process of determining the distribution of particle sizes, expressed as a percent of the total dry weight. It is used to determine the gradation or distribution of aggregate particle sizes within a given sample of aggregate material. All the material passing the No. 4 (4.75 mm) sieve, consisting of natural sand, crushed stone sand or crushed gravel stone dust. All the material retained on and above No. 4 (4.75 mm) sieve. The method used in Virginia to determine the proportions of various particle sizes in a mineral aggregate. A device used to divide samples of aggregate and other granular materials. Getting a Representative Sample A representative sample is a relatively small portion of material having the physical and chemical properties as the group from which it is taken. It is often difficult to obtain, since the sampler must use judgment in selecting the sampling point or points that will represent the average of the group or lot. In many cases, representative sampling cannot be made in a single sample. It may be necessary to take a number of samples to obtain a true picture of the properties of a stockpile or source of material. And as the maximum particle size in the aggregate increases, the size of the sample must increase to maintain accuracy in testing. Test sample sizes for Fine and Coarse aggregates are found in AASHTO T-27 (pg. 6-14). In addition, the number and types of tests determine the size of the sample needed. There are three principal aggregate sampling points that are of concern at an asphalt plant: The source of the materials The stockpile The hot storage bin The first two are discussed in this chapter of the guide. The third is discussed in Chapter 7. page 2 Chapter 6 VDOT and Platinum Performance Partners, LLC

107 Sampling and Analysis of Aggregate Sampling at the Source When sampling at the source of materials, remember one general rule - it is easier to obtain a representative sample from the production stream, such as from the conveyor belt, than from trucks, storage bins or stockpiles. If the sample is taken from the conveyor belt, it should be removed from the entire crosssection of the belt. The same would be true when sampling from the chutes of bins. Figure 6-1 illustrates the process of sampling at the source, in this case, a conveyor belt. Figure 6-1. Sampling at the Source BEST PRACTICE Obtain a representative sample from the production stream (e.g., conveyor belt). If you are taking a sample from the conveyor belt, remove the sample from the entire cross section of the belt. Describes a best practice to be utilized when possible. Sampling from the Stockpile Getting a sample from a stockpile (Figure 6-2) is not easy, and great care must be taken to obtain a truly representative sample. Segregation usually occurs when the material is stockpiled because the coarser particles will roll to the base of the pile. Take samples of coarse aggregates near the top and base of stockpiles, and at some intermediate point. And to prevent further segregation during sampling, shove a board into the pile just above the sampling area. Figure 6-2. Sampling from the Stockpile VDOT and Platinum Performance Partners, LLC Chapter 6 page 3

108 Sampling and Analysis of Aggregate BEST PRACTICE Samples of coarse aggregates from stockpiles should be taken at or near the top and base, and some intermediate point. Describes a best practice to be utilized when possible. Another method of sampling coarse materials is to expose the face of the stockpile from the top to the bottom, using a front-end loader. Then take the samples from the exposed face. Another method is to use the overhead loader to take a scoop from bottom to top and dump the material in a convenient location for sampling, as illustrated in Figure 6-3. Figure 6-3. Sampling Using a Front-End Loader Fill the sample bag or bucket randomly from around the scoop of material, as illustrated in Figure 6-4. Fine aggregate may be sampled with a sampling tube approximately 1 ¼ inch (30 mm) in diameter and 6 feet (2 meters) long. If a stockpile of sand is to be sampled, it is usually only necessary to remove the dry layer where the segregation occurs and sample the damp material below. Procedures for sampling are described in AASHTO T2. Figure 6-4. Sampling from the Scoop of Material page 4 Chapter 6 VDOT and Platinum Performance Partners, LLC

109 Sampling and Analysis of Aggregate An Overview of Sieve Analysis Sieve analysis (Figure 6-5) is the process of determining the distribution of particle sizes, expressed as a percent of the total dry weight. Gradation is determined by passing the material through a series of sieves stacked with progressively smaller openings from top to bottom. Once separated, the weight of particles retained on each sieve is measured and compared to the total sample weight. Particle size distribution is then expressed as a percent retained by weight on each sieve size. Results are usually expressed in tabular or graphical format. Figure 6-5. Sieve Analysis TOOLS AND EQUIPMENT Sieves are perforated vessels designed to separate materials by size. Describes what tools, equipment and tests are required to complete the job safely and with the highest level of quality. Sieve numbers and sizes most often used in grading aggregates for asphalt paving mixtures are displayed in the table that follows. Sample sieves and their sizes are illustrated in Figure 6-6. Nominal Dimensions of U.S. Standard Sieves AASHTO M 92 Sieve Designation Nominal Sieve Opening 1 ½ in. (37.5mm) 1.50 in. 1 in. (25.0mm) 1.00 in. 3/4 in. (19.0mm) in. 1/2 in. (12.5mm) in. 3/8 in. (9.5mm) in. No. 4 (4.75mm) in. No. 8 (2.36mm) in. No. 16 (1.18mm) in. No. 30 (600μm) in. No. 50 (300μm) No. 100 (150μm) No. 200 (75μm) in in in. mm=millimeter; μm=micrometer VDOT and Platinum Performance Partners, LLC Chapter 6 page 5

110 Sampling and Analysis of Aggregate Figure 6-6. Sieves Used in Grading Aggregates for Asphalt Paving Mixtures Sieve sizes to be used for the various type mixtures are designated in the specifications. (See Section , Table II-13.) Gradations for materials are expressed on the basis of total percent passing (i.e., the total percent of aggregate by weight that will pass a given size sieve). Some of the descriptive terms used in referring to aggregate gradations are: Coarse aggregate - All the material retained on and above No. 4 (4.75 mm) sieve. Fine aggregate - All the material passing the No. 4 (4.75 mm) sieve. Mineral dust - That portion of the fine aggregate passing the No. 200 (75 μm) sieve. Mineral filler - A finely divided mineral product, at least 70 percent of which will pass the No. 200 (75 μm) sieve. Note: Some aggregate test procedures require material to be split at the No. 4 (4.75 mm) sieve. page 6 Chapter 6 VDOT and Platinum Performance Partners, LLC

111 Sampling and Analysis of Aggregate How to Conduct Sieve Analysis There are two methods of determining proportions of various particle sizes in a mineral aggregate: Dry sieve analysis Washed sieve analysis In Virginia, the Washed Sieve Analysis is the method used for asphalt mixes, and is the one that will be discussed in this section. The purpose of this method is to separate the amount of material finer than the No. 200 sieve. Regardless of the size of the aggregate, the procedure for running a sieve analysis is basically the same. Standard procedures for running the sieve analysis are given in AASHTO T 27 and AASHTO T 11. The steps for this procedure are outlined as follows: STEP 1. Obtain the Sample 1.1 Use correct sieve sizes for the type mix to be produced as required. 1.2 Obtain a representative sample of the material from the original sample using either a sample splitter or the quartering method, each of which is described in the text that follows. Regardless of the method used, after you have obtained a representative sample, reduce the sample to a size that can be handled on the balance and sieves according to maximum stone size. (Reference AASHTO T 27.) TOOLS AND EQUIPMENT A sample splitter is used to divide samples of aggregate and other granular materials. Describes what tools, equipment and tests are required to complete the job safely and with the highest level of quality. Sample Splitter. An example of a sample splitter is shown in Figure 6-7. Sample splitters must have an even number of equal width chutes. If you are working with coarse aggregate, there must be eight chutes. If you are working with fine aggregate, there must be at least twelve chutes. The chutes discharge alternately to each side of the splitter. The splitter also must be equipped with: Two receptacles to hold the two halves of the sample following splitting A hopper or straightedge pan by which the sample may be fed at a controlled rate to the chutes. The splitter and accessory equipment shall be so designed that the sample will flow smoothly without restriction or loss of material. Figure 6-7. A Sample Splitter VDOT and Platinum Performance Partners, LLC Chapter 6 page 7

112 Sampling and Analysis of Aggregate To use the sample splitter: A. Place the field sample in the hopper or pan, uniformly distributing the sample from edge to edge as shown in Figure 6-8, so that when it is introduced into the chutes, approximately equal amounts will flow through each chute. B. Introduce the sample, allowing it to freely flow through the chutes into the receptacles as shown in Figure 6-9. Note: You may need to adjust the rate to ensure a free flow. Figure 6-8. Place the Sample in the Hopper You may reintroduce the portion of the sample in one of the receptacles into the splitter as many times as necessary to reduce the sample to the size specified for the intended test. C. Inspect the final results as shown in Figure Reserve the portion of the material collected in the other receptacle for reduction in size for other tests. Figure 6-9. Introduce the Sample Note: If you are working with fine aggregate, follow the same steps as above, but use a fine aggregate splitter. Figure Inspect the Results page 8 Chapter 6 VDOT and Platinum Performance Partners, LLC

113 Sampling and Analysis of Aggregate Quartering Method. The quartering method reduces a sample by successively mixing, dividing into quarters, and keeping two opposite quarters of the sample. This method is used when a conventional sample splitter is not available. The steps vary somewhat depending on the surface on which the sample is being quartered. A. Distribute a shovel full of the aggregate as uniformly as possible over a hard, clean, level surface. Continue to distribute shovels full of material in layers until all the sample is used to make a wide, flat pile that is reasonably uniform in thickness and distribution of aggregate sizes. Do not permit coning of the aggregate. AWARENESS/IMPORTANT Do not permit coning (e.g., forming of a cone) of the aggregate during this process because the heavier components will distribute to the bottom and interfere with the representativeness of the sample. Highlights a step in the procedure which is either unusual or very particular to this procedure. May also indicate awareness (additional information) or a cautionary concern in the procedure. B. Divide the pile cleanly into equal quarters with a squareended shovel or straight piece of sheet metal as shown in Figure C. Remove two opposite quarters as shown in Figure 6-12 and set aside. D. Repeat steps A through C with the remaining portion of the aggregate until a test sample of desired size is obtained. E. Store the portion that has been set aside for possible check testing, if desired. Figure Divide the Pile into Quarters Variation: If you are in the field and do not have easy access to a hard, clean surface, you may modify this procedure for use with a canvas. When using a canvas, make the division described in B above by inserting a thin stick (or rod) under the canvas and raising it to divide the sample equally, first into halves, then into quarters. Remove the two opposite quarters as described above, and set aside. Figure Remove Opposite Quarters VDOT and Platinum Performance Partners, LLC Chapter 6 page 9

114 Sampling and Analysis of Aggregate STEP 2. Dry and Weigh the Sample 2.1 Dry the aggregate sample thoroughly. The samples are dried to constant weight on a hot plate or in an oven at a temperature of 230 ºF (110 ºC). 2.2 Accurately weigh the dried sample. Extreme care must be taken to avoid any loss of the material, as this will affect the accuracy of the results. Also, do not adjust the weight of the sample to an even figure, such as 500g, 1000g, etc. Use the entire reduced and dried sample. 2.3 Record the total dry weight of the sample. TOOLS AND EQUIPMENT The following equipment is required for these steps: hot plate or oven, balance scale, sieves, shaker, and cleaning tools for the sieve. Describes what tools, equipment and tests are required to complete the job safely and with the highest level of quality. STEP 3. Wash, then Dry and Re-weigh the Sample 3.1 Wash the sample over a nest of two sieves, until the water is clear. Make sure the upper is a No. 16 (1.18mm) mesh sieve and the lower sieve is a No. 200 (75μm) mesh sieve. Be careful not to lose any portion of the sample. (Reference AASHTO T-11.) 3.2 Dry the sample to a constant weight on a hot plate or in an oven at a temperature of 230 ºF (110 º C). 3.3 Accurately weigh the dried sample and record its weight. 3.4 Separate the sample into individual sizes using the proper sieves as shown in Figure 6-13, with the coarse sieve at the top. Each sieve below this one is finer; with the finest sieve, a No. 200 (75μm), at the bottom. Place a pan below the No.200 sieve to retain any fine material that may pass this sieve. Note: The sieves normally used are the standard round 8-inch sieves. 3.5 Place the dried and weighed sample on the top sieve and the entire nest of sieves in a shaker as shown in Figure Activate the shaker. The motion assists gravity in dividing the material into different sizes. It will take approximately 7 to 10 minutes of shaking to separate the material. Figure Separate the Sample Using Proper Sieves Figure Place Sieves in Shaker and Activate Shaker page 10 Chapter 6 VDOT and Platinum Performance Partners, LLC

115 Sampling and Analysis of Aggregate 3.7 Weigh and record the weights retained on each sieve as shown in Figure An Example: Suppose a particular gradation required a maximum size of 1/2 inch (12.5mm). Upon examination of this sieve and the next smaller sieve (the 3/8 in. (9.5mm) sieve), no material was found retained. This would then be recorded in the "Weight Retained (Grams)" column of the sample worksheet shown as Figure 6-16 below, as "0" for these two sieves. The No. 4 (4.75mm) sieve is then checked, the material carefully removed and placed on the balance and a weight of 4 grams is recorded. The 4 grams are then removed from the balance. Then the material from the next sieve in this example, the No. 8 (2.36mm) sieve, is removed, weighed, and a weight of 37 grams is recorded. The 37 grams are then removed from the balance. The findings are illustrated below: Total dry weight of sample before washing = 501 Dry weight of sample after washing = 484 Figure Weigh and Record Weights Retained on Each Sieve Sieve Weight Retained (Grams) Percent Retained Total Percent Passing 1/2 in. (12.5 mm) 0 3/8 in. (9.5 mm) 0 #4 (4.75 mm) 4 #8 (2.36 mm) 37 #30 (600 µm) 283 Weight of material retained on each sieve #50 (300 µm) 141 #200 (75 µm) 16 Pan wt. 3 Wt. sieved = 484 mm=millimeter; µm=micrometer Dry weight of sample after washing Figure Sample Worksheet VDOT and Platinum Performance Partners, LLC Chapter 6 page 11

116 Sampling and Analysis of Aggregate STEP 4. Calculate Percentage Retained and Passing 4.1 Calculate the percent retained on each sieve. 4.2 Record the values to the nearest 0.1 percent (0.1%) of the total original dry sample mass, in accordance with AASHTO-T27. To find percent retained: Percent Retained = Wt. on the Sieve x 100 Total Dry Wt. of Sample 4.3 Repeat for each sieve size and enter the percent retained amounts in the Percent Retained column of the worksheet. To continue the previous example, Figure 6-17 illustrates this process. Note: The Total Dry Wt. of Sample is the sample weight before washing. Total dry weight of sample before washing = 501 Dry weight of sample after washing = 484 Sieve Weight Retained (Grams) Percent Retained Total Percent Grams Retained x 100 = % Retained Passing Total Wt. (Grams) 1/2 in. (12.5 mm) 3/8 in. (9.5 mm) 0 0 #4 (4.75 mm) #8 (2.36 mm) #30 (600 µm) #50 (300 µm) #200 (75 µm) Pan wt. 3 4 x 100 = 0.8% x 100 = 7.4% x 100 = 56.5% x 100 = 28.1% x 100 = 3.2% 501 Wt. sieved = 484 Figure Percentage Retained page 12 Chapter 6 VDOT and Platinum Performance Partners, LLC

117 Sampling and Analysis of Aggregate 4.4 Calculate the total percent passing each sieve. To determine this figure, subtract the percent retained on each sieve from the percent passing the next larger sieve. Repeat for each sieve. 4.5 Enter the value obtained from Step 4.4 in the Total Passing column of the worksheet, as illustrated in Figure In accordance with AASHTO-T27, record the values to the nearest 0.1 percent (0.1%) of the total original dry sample mass. AWARENESS/IMPORTANT Always place one hundred percent (100%) in the Total Percent Passing column one line above the sieve having the first entry of grams retained. Highlights a step in the procedure which is either unusual or very particular to this procedure. May also indicate awareness (additional information) or a cautionary concern in the procedure. % Passing - % Retained = % Passing Sieve 1/2 in. (12.5 mm) Weight Retained (Grams) Percent Retained 3/8 in. (9.5 mm) #4 (4.75 mm) #8 (2.36 mm) #30 (600 µm) #50 (300 µm) #200 (75 µm) Pan wt. 3 Wt. sieved = 484 Total Percent Passing 100.0% Passing 3/8 Sieve - 0.8% Retained No. 4 Sieve 99.2% Passing No. 4 Sieve 99.2% Passing No.4 Sieve - 7.4% Retained No. 8 Sieve 91.8% Passing No. 8 Sieve 91.8% Passing No. 8 Sieve % Retained No. 30 Sieve 35.3% Passing No. 30 Sieve 35.3% Passing No. 8 Sieve % Retained No. 50 Sieve 7.2% Passing No. 50 Sieve 7.2% Passing No. 50 Sieve % Retained No. 200 Sieve 4.0% Passing No. 200 Sieve Figure Percentage Passing Exception: For acceptance, percentages should be to the nearest whole number, except if the percentage passing the No. 200 sieve is less than 10 percent, in which case it must be reported to the nearest one-tenth of a percent (0.1 percent) (AASHTO T-30). VDOT and Platinum Performance Partners, LLC Chapter 6 page 13

118 Sampling and Analysis of Aggregate Test Sample Size for Fine and Coarse Aggregate The following represents test sample sizes for fine and coarse aggregate, and is illustrated in Figure 6-19: 1. Fine Aggregate The minimum size of the test sample of aggregate, after drying, shall conform to AASHTO T 27: Aggregate with at least 95 percent passing a No. 8 (2.36 mm) sieve: 100 grams Aggregate with at least 85 percent passing a No. 4 (4.75 mm) sieve: 500 grams and more than 5 percent retained on a No.8 (2.36 mm) sieve. 2. Coarse Aggregate The weight of the test sample of coarse aggregate must conform to AASHTO T 27. Nominal Maximum Size Square Openings Minimum Weight of Test Sample in (mm) lb. (kg) 3/8 (9.5) 2 (1) 1/2 (12.5) 4 (2) 3/4 (19.0) 11 (5) 1 (25.0) 22 (10) 1 1/2 (37.5) 33 (15) 2 (50) 44 (20) 2 1/2 (63) 77 (35) 3 (75) 130 (60) 3 1/2 (90) 220 (100) 4 (100) 330 (150) 5 (125) 660 (300) Figure Test Sample Sizes for Fine and Coarse Aggregate page 14 Chapter 6 VDOT and Platinum Performance Partners, LLC

119 Sampling and Analysis of Aggregate Consensus Property Testing DEFINITIONS. The following terms will be used throughout this section: Consensus Property Testing Superpave Sand Equivalent (SE) Fine Aggregate Angularity (FAA) Coarse Aggregate Angularity (CAA) Flat & Elongated (F/E) Testing that places consensus requirements on coarse and fine aggregate angularity, flat and elongated particles, and clay content. Superpave is an acronym for Superior Performing Asphalt Pavements, a comprehensive asphalt mix design, evaluation, and analysis system. The relative proportions of fine dust or clay-like materials in fine aggregate (or granular soils). The angularity of fine aggregate. The angularity of coarse aggregate. The dimensional ratio at which an aggregate particle is considered too flat or too elongated. Sampling of aggregate for consensus property testing shall come from either each individual aggregate component or the total blend. Care should be taken to obtain a representative sample. Once the sample has been obtained, sieving should be performed to obtain the appropriate size sample material for testing. Superpave Aggregate Characteristics and Test Methods Superpave is an acronym for Superior Performing Asphalt Pavements. Superpave, a product of the Strategic Highway Research Program, is a comprehensive asphalt mix design, evaluation and analysis system. It represents an improved, performance-based system for specifying asphalt binders and mineral aggregates, performing asphalt mixture design and analyzing pavement performance. Under this program, an initiative was undertaken to improve materials selection and mixture design by developing: A new mix design method that accounts for traffic loading and environmental conditions. A new method of asphalt binder evaluation. New methods of mixture analysis. The Superpave Design System includes an asphalt binder specification that uses new binder physical property tests; a series of aggregate tests and specifications; a hot mix asphalt (HMA) design and analysis system; and computer software to integrate the system components. VDOT and Platinum Performance Partners, LLC Chapter 6 page 15

120 Sampling and Analysis of Aggregate As part of the Superpave Design System, specific characteristics of fine and coarse aggregates have been defined in the table shown as Figure Fine Aggregate Fine Aggregate Angularity (FAA) AASHTO T304 Method A Sand Equivalent (SE) AASHTO T 176 Coarse Aggregate Coarse Aggregate Angularity (CAA) ASTM D 5821 Flat & Elongated (F/E) ASTM D 4791* Test Method Test Method *Note: Flat and Elongated testing shall be performed on crushed gravel except aggregate sizes larger than the No. 4 (4.75 mm) sieve. These will be measured at 5:1 maximum to minimum dimension. Figure Characteristics and Test Methods Mix Design and Analysis Requirements For the Superpave Design System, as part of the job-mix formula: The aggregate Supplier or Asphalt Producer shall perform the consensus property tests. In addition, the consensus property tests shall be tested and reported at the frequency specified in Section of the Road and Bridge Specifications. The values used for acceptance of these properties are denoted in Section and are mix-dependent. For RAP portions of a mixture, all consensus properties except Sand Equivalent will be reported. In addition to aggregate consensus property testing, as part of the job mix formula, the aggregate supplier or asphalt producer shall perform aggregate-specific gravity tests. Aggregate-specific gravities shall be tested and reported at the frequency specified in Section The Department has established a policy for testing these properties due to use of blended aggregate stockpiles with substantial portions of fine and coarse material in a single stockpile. To conduct testing on a stockpile, the stockpile has to have 10% or more material within the definition of coarse or fine material subject to the test. Note: The Asphalt Producer has the option of performing aggregate quality tests on stockpiles or on the blend of each mix. An example would be a stockpile that contains 40% material retained on or above the No. 4 (4.75 mm) sieve (i.e., 60% of the material would pass the No. 4 sieve). The portion retained on the No. 4 sieve would be tested for Flat and Elongated and Coarse Aggregate Angularity. The portion passing the No. 4 sieve would have to be tested for Sand Equivalent and if more than 10% of the total aggregate passes the No. 8 (2.36mm) sieve, then that portion would be tested for Fine Aggregate Angularity. page 16 Chapter 6 VDOT and Platinum Performance Partners, LLC

121 Sampling and Analysis of Aggregate Chapter Six Knowledge Check 1. A process in which an aggregate is separated into its various sizes by passing it through sieves with screens of various size openings for the purpose of determining the distribution and particle size is: A. Fineness modules B. Sieve analysis C. Yield D. Moisture analysis 2. Coarse aggregate used in Asphalt Concrete is defined as all the material retained on or above the: A. No. 4 (4.75 mm) sieve B. No. 8 (2.36 mm) sieve C. No. 100 (.150 mm) sieve D. No. 200 (.075 mm) sieve 3. A relatively small portion of material having the same physical properties as the group or lot from which it is taken is called a: A. Stratified random sample B. Representative sample C. Random sample D. None of the above 4. Fine aggregate used in Asphalt Concrete is defined as all material passing the: A. No. 4 (4.75 mm) sieve B. No. 8 (2.36 mm) sieve C. No. 100 (.150 mm) sieve D. No. 200 (.075 mm) sieve 5. What is the most important thing in sampling of materials? 6. What determines the size of the sample required to run a sieve analysis? VDOT and Platinum Performance Partners, LLC Chapter 6 page 17

122 Sampling and Analysis of Aggregate 7. What are two methods of reducing an aggregate sample to size for testing? 8. How would you prepare a sample for sieve analysis? 9. Washed sieve analysis is a method used in Virginia for asphalt mixes for determining proportions of various particle sizes in a mineral aggregate. A. True B. False 10. The purpose of the washed sieve analysis is to separate the amount of material finer than what size sieve? 11. Which dry weight is used to calculate the percent retained? A. Total dry weight of sample before washing B. Dry weight of sample after washing 12. As a check against sample loss when running a sieve analysis, the combined grams on each individual sieve, in the weight retained column, should equal the: A. Total dry weight of sample before washing B. Dry weight of sample after washing 13. How are the different sizes of aggregate in a sample separated? page 18 Chapter 6 VDOT and Platinum Performance Partners, LLC

123 Sampling and Analysis of Aggregate 14. When conducting a sieve analysis, after the total sample has been shaken, the weight of material retained on each sieve size is recorded. A. True B. False (Please continue to the next page to begin solving sample problems.) VDOT and Platinum Performance Partners, LLC Chapter 6 page 19

124 Sampling and Analysis of Aggregate Problem No. 1: Determining Gradation Complete the following analysis. Total dry weight of aggregate before washing: Dry weight of aggregate after washing: grams grams Sieve Wt. Retained on each sieve % Retained % Passing 3/4 in 0 1/2 in 0 3/8 in 0 No No No No No Pan 3.1 page 20 Chapter 6 VDOT and Platinum Performance Partners, LLC

125 Sampling and Analysis of Aggregate Problem No. 2: Determining Gradation Complete the following analysis. Total dry weight of aggregate before washing: Dry weight of aggregate after washing: grams grams Sieve Wt. Retained on each sieve % Retained % Passing 3/4 in 0 1/2 in 0 3/8 in 0 No No No No No Pan 22.7 VDOT and Platinum Performance Partners, LLC Chapter 6 page 21

126 Sampling and Analysis of Aggregate Problem No. 3: Determining Gradation Complete the following analysis. Total dry weight of aggregate before washing: Dry weight of aggregate after washing: Sieve Wt. Retained on each sieve % Retained % Passing 2 in 0 1 ½ in 0 1 in /4 in /2 in /8 in No No No No No No page 22 Chapter 6 VDOT and Platinum Performance Partners, LLC

127 Sampling and Analysis of Aggregate Problem No. 4: Determining Gradation Complete the following analysis. Mix Type 12.5E Total dry weight of aggregate before washing: Dry weight of aggregate after washing: grams grams Sieve Wt. Retained on each sieve % Retained % Passing 2 in 0 1 ½ in 0 1 in 0 3/4 in 0 1/2 in /8 in No No No No No No VDOT and Platinum Performance Partners, LLC Chapter 6 page 23

128 Sampling and Analysis of Aggregate Problem No. 5: Determining Gradation Complete the following analysis. Mix Type SM-12.5D Total dry weight of aggregate before washing: Dry weight of aggregate after washing: Sieve Wt. Retained on each sieve % Retained % Passing 2 in 1 ½ in 1 in 3/4 in 0 1/2 in 0 3/8 in 73.2 No No No No No No page 24 Chapter 6 VDOT and Platinum Performance Partners, LLC

129 MCS: Asphalt Plant Certification 7 Blending Aggregates All of the particles needed in the aggregate to meet specifications and do the job are rarely found in a single material. Different sizes and materials must be blended in the proper quantities to produce the desired gradation and meet gradation specifications for a particular asphalt mix. It is extremely important that this blending process be completed correctly. This requires proper sampling of the materials to be blended and accurate determination of the gradation or sieve size distribution of the materials. In addition, we must determine the properties of each aggregate component and/or the total blend of the mix. The end result of a successful mix design is a recommended mixture of aggregate and asphalt binder type. This mixture is often referred to as the job mix formula (JMF) or recipe. The ability to blend aggregates to produce the right job mix formula is critical to success. Learning Objectives: Upon completion of this chapter, you should be able to: Describe the components of the job mix formula Describe the process for conducting mix design Combine aggregates to achieve the target blend, using the Trial and Error method and appropriate blending worksheets Demonstrate the procedure for hot bin sampling Calculate batch weight VDOT and Platinum Performance Partners, LLC Chapter 7 page 1

130 Blending Aggregates Mix Design DEFINITIONS. The following terms will be used throughout this section: Aggregate blending Gradation Job mix formula (JMF) Trial and Error method Combined gradation The process of proportionately mixing several aggregate gradations to obtain one desired aggregate gradation. The particle size distribution of an aggregate, which helps determine the properties of pavement materials. The optimized mixture of aggregate and asphalt binder type; the required AC and Gradation targets that the contractor must produce for the project. The method used to determine an optimum combination of aggregates. A mathematically-determined theoretical combination of aggregates based on their relative percent volume in the mixture..45 Power Chart A graphical technique that plots the percent passing vs. sieve size. This chart is very useful in comparing aggregate gradations and specification limits. Hot mix asphalt is a complex material upon which many different, and sometimes conflicting, performance demands are placed. It must resist deformation and cracking, be durable over time, resist water damage, provide a surface with good traction, and yet be inexpensive, readily made and easily placed. In order to meet these demands, the mix designer can manipulate three variables: Aggregate Items such as type (source), gradation and size, toughness and abrasion resistance, durability and soundness, shape, texture and cleanliness all can be measured, judged and altered to some degree. Asphalt binder Items such as type, durability, rheology and purity, as well as additional modifying agents can be measured, judged and altered to some degree. The ratio of asphalt binder to aggregate Usually expressed in terms of percent asphalt binder by total weight of HMA or total weight of aggregate, this ratio has a profound effect on HMA pavement performance. Hot mix asphalt design is the process of determining what aggregate to use, what asphalt binder to use, and the optimum combination of these ingredients. Hot mix asphalt design has evolved as a laboratory procedure that uses critical tests to make characterizations of each trial hot mix asphalt blend. These characterizations can give the mix designer a good understanding of how a particular mix will perform in the field during construction and under traffic loading. VDOT utilizes the Superpave mix design system and Stone Matrix Asphalt mix designs for the majority of asphalt concrete produced for the State. page 2 Chapter 7 VDOT and Platinum Performance Partners, LLC

131 Blending Aggregates The Job Mix Formula Gradation has a profound effect on material performance. But what is the best gradation? The target values of aggregate gradation and asphalt binder content for a job are specified based on the job mix formula (JMF). In its simplest form, the job mix formula is the recommended mixture of aggregate and asphalt binder type. It consists of two parts: 1. The combined gradation of the aggregates to be used in the production of the asphalt concrete mixture. 2. The asphalt content necessary to produce a satisfactory mix, meeting all the specification requirements. In order to meet the demands placed by the desirable hot mix asphalt properties, mix design processes involve the three basic steps illustrated in Figure 7-1. Figure 7-1. Mix Design Process Refer to the VDOT Road and Bridge Specifications Section 211 Asphalt Concrete, Section Table II-13 (reproduced in this chapter as Figure 7-3 on page 7-6) for the design gradations for various types of mixes. An example of a completed job mix formula is shown on the next page. VDOT and Platinum Performance Partners, LLC Chapter 7 page 3

132 Blending Aggregates Form TL-127 (Rev. 11/05) VIRGINIA DEPARTMENT OF TRANSPORTATION MATERIALS DIVISION STATEMENT OF ASPHALT CONCRETE OR CENTRAL-MIX AGGREGATE JOB-MIX FORMULA Submit to the District Administrator, Virginia Department of Transportation. Approval must be received by the contractor from the Materials Division before work is begun. This job-mix design is approved for all projects of the Department for the type of mix and the calendar year shown below. Contractor Design Mix No. Design Lab No. R - 5 Date 11/8/2011 Job Mix ID No. Calendar Yr TSR Test No. Type Mix / Size Aggregate Bit. Conc. Type SM-12.5D Producer Name & Plant Location Stone Plant Co., White, VA Phone Materials Kind Source Approval Phase A B * C Aggregate 85 % #28 Rocky Rd. Corp., Unicoi, VA Aggregate % Rap % Sand 15 % Natural Sand Gravel King, Loafers Glory, VA Screening % Lime % Asphalt Cement PG Chevron or Citgo Asphalt Prime/Tack Additives: 0.50 Kling Beta 2700 Scan Rd, Waco, TX Job-Mix Sieves Total % Passing Lab JMF Production JMF Tolerance % + or - Acceptance Range Average of 8 Test(s) End of Year Average Design/Spec. Range Approval Phase A B * A B C 3/4" /2" /8" Max # # Asphalt (%) Lay Down Temperatures o F( o C) Muffle Furnace Correction Factor: 0.50 Field Correction Factor (G se G sb ): Lab Compaction Temperatures - o F ( o C) Producer Technician s Certification Number MATERIALS DIVISION USE ONLY SMA Mixes Pill Weight: VCA DRC : G CA : Remarks Nominal Max. Size Aggregate Application Rates: Min. lb/yd 2 (kg/m 2 ) Max. lb/yd 2 (kg/m 2 ) Mix Properties at the Job-Mix Compacted Unit Asphalt Content: Weight lb/ft 3 (kg/m 3 ) VTM: G mm: Checked By: Approved tentatively subject to the production of material meeting all other applicable requirements of the specification. * Note: Part B Production JMF and corresponding Material percentages will be filled out by the DME upon receipt of the additional requirements of the HMA producer within the first three lots under Section (b) Copies: State Materials Engineer Part A: Date: District Materials Engineer Approvals Project Inspector Part B: Date: Sub-Contractor and/or Producer Part C: Date: page 4 Chapter 7 VDOT and Platinum Performance Partners, LLC

133 Blending Aggregates In the following sections we will cover the procedures for combining aggregates to achieve the target blend. This procedure can be applied: In the lab during design To set a drum plant s cold feed rate To proportion batch weights from the hot bins in a batch plant. We will also introduce VDOT s allowable gradation bands for Superpave mixes and production tolerances and the acceptance range allowed during production. By attending to the gradation bands, production tolerances, and acceptance range, the Producer/Contractor can prevent producing material that does not conform to the JMF. Combining Aggregates to Achieve the Target Blend Mathematical procedures are available to determine an optimum combination of aggregates. However, the Trial and Error method, guided by a certain amount of reasoning, is the most practical procedure to determine a satisfactory combination. A key feature of this method is the use of continual measurements and adjustments to achieve success. How to Conduct the Trial and Error Method Use a Blending Worksheet (Figure 7-2) to capture gradations for each aggregate material and determine the percentage of each type of aggregate that will result in the target gradation needed for the final mix. Aggregate: % Used: BLENDING WORKSHEET Sieve (in) % Pass % Blend % Pass % Blend % Pass % Blend Total Blend Target Value Design Range 1 1/2 1 3/4 1/2 3/8 No. 4 No. 8 No. 30 No. 50 No. 100 No. 200 Figure 7-2. Blending Worksheet VDOT and Platinum Performance Partners, LLC Chapter 7 page 5

134 Blending Aggregates STEP 1. Enter the individual aggregate gradations to be used, and the design range limits for the mix type being produced or evaluated in the lab, in the appropriate columns of the Blending Worksheet. You will use the Blending Worksheet to mathematically calculate the blending of aggregates. VDOT Road and Bridge Specifications Section (Table II-13, shown as Figure 7-3) defines the allowable design ranges (gradation bands) for VDOT Superpave mix types. Table II-13. Asphalt Concrete Mixtures-Design Range Percentage by Weight Passing Square Mesh Sieves (In) Mix Type 2 1 ½ 1 3/4 1/2 3/8 No. 4 No. 8 No. 30 No. 50 No. 200 SM-9.0 A,D,E 100 * max SM-9.5 A,D,E 100 * max SM-12.5 A,D,E max IM-19.0 A,D,E max BM max C (Curb Mix) Legend: SM = Surface Mixture, IM = Intermediate Mixture, BM = Base Mixture *A production tolerance of 1% will be applied to this sieve, regardless of the number of tests in the lot. Figure 7-3. Table II-13 from VDOT Road and Bridge Specifications, Section STEP 2. Enter the Target Values for the mix type being produced or evaluated in the Target Value column of the Blending Worksheet. The target value for the combined gradation must be within the design limits of the specifications Note: The target value is provided by the Asphalt Mix Design Technician for lab evaluation and design, or from an approved JMF for production. page 6 Chapter 7 VDOT and Platinum Performance Partners, LLC

135 Blending Aggregates STEP 3. Estimate the proportions (i.e., the correct percentage of each aggregate needed) to get a combined gradation near the target value and enter these figures on the line marked % Used. If two aggregates are combined, the first estimate might be 50% of Aggregate 1 and 50% of Aggregate 2. Note: Remember, the sum of the proportions must always equal 100. STEP 4. Calculate the individual proportions on each sieve for each aggregate and enter in the column % Blend. Then determine the sum of the % Blend columns for each sieve and enter this total sum in the Total Blend column. The method of calculating the combined gradation will be shown in the sample problem that begins on page 7-9. STEP 5. Compare the result with the target value, using the decision table below and the.45 Power Chart (shown as Figure 7-4 on the next page) to determine success and make adjustments. Condition IF the calculated gradation is close to the target value IF the calculated gradation is not close to the target value IF the second trial is still not close to the target value IF after several trials the aggregates will not combine within the design range Action THEN no further adjustments need to be made. THEN an adjustment in the proportions must be made and the calculations repeated. THEN continue trials until the right proportions of each aggregate are found. THEN consider using or adding different materials. VDOT and Platinum Performance Partners, LLC Chapter 7 page 7

136 Blending Aggregates Power Chart Depicting Fine Aggregate, Coarse Aggregate and Target Value Percent Passing Fine Aggregate Coarse Aggregate Target Value Maximum Density Line Spec Limits for Target Sieve Size (mm) Figure 7-4. A.45 Power Chart Key Points of the.45 Power Chart: Fine gradations will plot above the Maximum Density Line (MDL). Coarse gradations will plot below the MDL. When combining aggregates, only targets that fall between two of the individual aggregate gradations are possible. Using this chart will help eliminate the frustration of the fourth step in the decision table on the previous page. General Math Conversion: To convert a percentage (%) to a decimal, divide by 100 or move the decimal place two places to the left. Example: 75% 75/100 =.75 page 8 Chapter 7 VDOT and Platinum Performance Partners, LLC

137 Blending Aggregates Sample Problems The sample problems in this section are designed to illustrate the Trial and Error method of determining aggregate mix ratios. Each sample problem will display steps that map the steps outlined in the Trial and Error method section of this chapter (pages 7-5 through 7-7). Sample Problem 1: Trial and Error Combination of Two Aggregates Mix type: SM-12.5 A STEP 1. Enter the aggregate gradations and design range into the appropriate columns of the Blending Worksheet. Aggregate: Fine Aggregate Coarse Aggregate % Used: Sieve (in) % Pass % Blend % Pass % Blend Total Blend Target Value Design Range 1 1/2 1 3/ / / max No. 4 No No. 30 No. 50 No. 100 No STEP 2. Obtain the target values and enter these values in the Target Value column of the Blending Worksheet, as shown on the worksheet that follows. The target value must be within design range. The target value is provided by Asphalt Mix Design Technician. VDOT and Platinum Performance Partners, LLC Chapter 7 page 9

138 Blending Aggregates Aggregate: Fine Aggregate Coarse Aggregate % Used: Sieve (in) % Pass % Blend % Pass % Blend Total Blend Target Value Design Range 1 ½ 1 ¾ ½ / max No. 4 No No. 30 No. 50 No. 100 No STEP 3. Estimate the proportions and enter these figures on the line marked % Used. The first estimate might be 50% of the Fine Aggregate and 50% the Coarse Aggregate. Note: Remember, the sum of the proportions must always equal 100. Data resulting from this step is presented in the blending worksheet shown below and in Figure 7-5. Aggregate: Fine Aggregate Coarse Aggregate % Used: Sieve (in) % Pass % Blend % Pass % Blend Total Blend Target Value Design Range 1 ½ 1 ¾ ½ / max No. 4 No No. 30 No. 50 No. 100 No page 10 Chapter 7 VDOT and Platinum Performance Partners, LLC

139 Blending Aggregates Power Chart Depicting Fine Aggregate, Coarse Aggregate and Target Value Percent Passing Fine Aggregate Coarse Aggregate Target Value Maximum Density Line Spec Limits for Target Sieve Size (mm) Figure 7-5. Data from Step 3 Plotted on the.45 Power Chart STEP 4. Determine individual proportions (% Blend) and Total Blend: 4.1 Calculate the individual proportions on each sieve for each of the two aggregates and enter in the column % Blend. % Blend = Percent Passing (a given sieve) x Percent Used (of that Aggregate) Note: Change Percent Used to a decimal. VDOT and Platinum Performance Partners, LLC Chapter 7 page 11

140 Blending Aggregates 4.2 Add the two columns for each sieve and enter in the column marked Total Blend. Total Blend = % Blend for Aggregate % Blend for Aggregate n Calculations: % Blend: Sieve Fine Aggregate Coarse Aggregate 3/4 100 x.50 = x.50 = 50 1/2 100 x.50 = x.50 = 47 3/8 94 x.50 = x.50 = 32.5 No x.50 = x.50 = 13.5 No x.50 = x.50 = 0.6 Total Blend: Sieve Fine Aggregate + Coarse Aggregate = Total Blend 3/ = 100 1/ = 97 3/ = 79.5 round to 80 No = 39.5 round to 40 No = 4.2 STEP 5. Compare this combined gradation and recalculate as needed. 5.1 Compare the Total Blend with the Target Value. The blending worksheet that follows and Figure 7-6 present the results. Aggregate: Fine Aggregate Coarse Aggregate % Used: Sieve (in) % Pass % Blend % Pass % Blend % Pass % Blend Total Blend Target Value Design Range 1 ½ 1 ¾ ½ / max No. 4 No No. 30 No. 50 No. 100 No page 12 Chapter 7 VDOT and Platinum Performance Partners, LLC

141 Blending Aggregates Percent Passing Power Chart Depicting Fine Aggregate, Coarse Aggregate and Target Value and 50/50 Total Blend Fine Aggregate Coarse Aggregate Target Value 50% & 50% Maximum Density Line Spec Limits for Target Sieve Size (mm) Figure 7-6. Data from Step 5.1 plotted on the.45 Power Chart Observations: The 3/8 (9.5mm) and No. 8 (2.36mm) sieves are not close to target value, therefore an adjustment needs to be made. On the.45 Power Chart shown as Figure 7-6, note that the blend is too coarse. Increase the percentage of the fine aggregate used to fine the Total Blend. 5.2 It is helpful to use one sieve to make an adjustment before recalculating all sieves. This example illustrates use of the 3/8 sieve: Aggregate: Fine Aggregate Coarse Aggregate % Used Trial Trial Trial Trial Trial Trial Trial VDOT and Platinum Performance Partners, LLC Chapter 7 page 13

142 Blending Aggregates Sieve (in) % Pass % Blend % Pass % Blend Total Blend Target Value Design Range 3/8 Trial max Trial max Trial max Trial max Trial max Trial max Trial max Conclusion from this table: Choose Trial No. 5 and recalculate rest of sieves. 5.3 Recalculate Blend (using Trial 5). The results are illustrated in the blending worksheet below and in Figure 7-7. Aggregate: Fine Aggregate Coarse Aggregate % Used: Sieve (in) % Pass % Blend % Pass % Blend Total Blend Target Value Design Range 1 1/2 1 3/ / / max No. 4 No No. 30 No. 50 No. 100 No page 14 Chapter 7 VDOT and Platinum Performance Partners, LLC

143 Blending Aggregates Percent Passing Power Chart Depicting Fine Aggregate, Coarse Aggregate and Target Value and 75/25 Total Blend Fine Aggregate Coarse Aggregate Target Value 75% and 25% Maximum Density Line Spec Limits for Target Sieve Size (mm) Figure 7-7. Data from Step 5.3 Plotted on the.45 Power Chart As shown in Figure 7-7, adjustments have moved the Total Blend to the Target Value. At this point, stockpile variability and plant precession need to be considered and accounted for in the amount of fine tuning to the percent of each aggregate used. VDOT and Platinum Performance Partners, LLC Chapter 7 page 15

144 Blending Aggregates Sample Problem 2: Trial and Error Combinations of More than Two Aggregates. Mix Type: IM-19.0 A The same basic principles and steps are followed when combining more than two aggregates. STEP 1. Enter the aggregate gradations and design limits into the appropriate columns of the Blending Worksheet. Aggregate: Mineral Filler Fine Aggregate Coarse Aggregate % Used: Sieve (in) % Pass % Blend % Pass % Blend % Pass % Blend Total Blend Target Value Design Range 1 1/ / / max 3/8 No. 4 No No. 30 No. 50 No. 100 No page 16 Chapter 7 VDOT and Platinum Performance Partners, LLC

145 Blending Aggregates STEP 2. Obtain the target values and enter these values in the Target Value column of the Blending Worksheet, as shown below. The target value must be within design range. The target value is provided by Asphalt Mix Design Technician. Aggregate: Mineral Filler Fine Aggregate Coarse Aggregate % Used: Sieve (in) % Pass % Blend % Pass % Blend % Pass % Blend Total Blend Target Value Design Range 1 1/ / / max 3/8 No. 4 No No. 30 No. 50 No. 100 No Figure 7-8 illustrates a.45 Power Chart for this sample problem. VDOT and Platinum Performance Partners, LLC Chapter 7 page 17

146 Blending Aggregates.45 Power Chart for Example 2: IM-19.0 and Aggregates Percent Passing Mineral Filler Fine Aggregate Coarse Aggregate Target Value Maximum Density Line Spec Limits for Target Sieve Size (mm) Figure 7-8. Data for Problem 2 Plotted on the.45 Power Chart STEP 3. Estimate the proportions and enter these figures on the line marked % Used: The first estimate used for this trial blend is 40% of Mineral Filler, 30% of Fine Aggregate, and 30% of Coarse Aggregate. Note: Remember, the sum of the proportions must always equal 100. Aggregate: Mineral Filler Fine Aggregate Coarse Aggregate % Used: Sieve (in) % Pass % Blend % Pass % Blend % Pass % Blend Total Blend Target Value Design Range 1 1/ / / max 3/8 No. 4 No No. 30 No. 50 No. 100 No page 18 Chapter 7 VDOT and Platinum Performance Partners, LLC

147 Blending Aggregates STEP 4. Determine % Blend and Total Blend. 4.1 Calculate the individual proportions on each sieve for each of the three aggregates and enter in the column % Blend. 4.2 Add the three columns for each sieve and enter in the column Total Blend. % Blend = % Pass x Percent Aggregate Proportion Note: Change Percent Aggregate Proportion to a decimal. Total Blend = % Blend Mineral Filler + % Blend Fine Aggregate + % Blend Coarse Aggregate. Calculations: % Blend: Sieve Mineral Filler Fine Aggregate Coarse Aggregate x.40 = x.30 = x.30 = 30 3/4 100 x.40 = x.30 = x.30 = /2 100 x.40 = x.30 = x.30 = 14.1 No x.40 = x.30 = x.30 = 2.4 No x.40 = x.30 = 0 0 x.30 = 0 Total Blend: Sieve Mineral Filler + Fine Aggregate + Coarse Aggregate = Total Blend = / = 98.8 = 99 1/ = 83.8 = 84 No = 63.1 = 63 No = 11.2 VDOT and Platinum Performance Partners, LLC Chapter 7 page 19

148 Blending Aggregates STEP 5. Compare this combined gradation and recalculate as needed. 5.1 Compare the Total Blend with the Target Value, as shown below. Figure 7-9 present the results. Aggregate: Mineral Filler Fine Aggregate Coarse Aggregate % Used: Sieve (in) % Pass % Blend % Pass % Blend % Pass % Blend Total Blend Target Value Design Range 1 1/ / / max 3/8 No. 4 No No. 30 No. 50 No. 100 No Power Chart for Example 2: IM-19.0 and Aggregates: Initial Trial Percent Passing Mineral Filler Fine Aggregate Coarse Aggregate Target Value Sieve Size (mm) 12.5 Initial Trial (40, 30, 30) Figure 7-9. Data from Step 5.1 Potted on the.45 Power Chart page 20 Chapter 7 VDOT and Platinum Performance Partners, LLC

149 Blending Aggregates Observation: The Total Blend is too fine. Investigate reducing the amount of Mineral Filler and/or Fine Aggregate and increasing the percent coarse aggregate. 5.2 It is helpful to use one sieve to make an adjustment before recalculating all sieves. This example illustrates use of the No. 8 sieve: Sieve (in) Aggregate Mineral Filler Fine Aggregate Coarse Aggregate % Used Trial Trial Trial Trial Trial % Pass % Blend % Pass % Blend % Pass % Blend Total Blend Target Value Design Range No. 8 Trial Trial Trial Trial Trial Conclusion from this table: Choose Trial No. 4 and recalculate rest of sieves. 5.3 Recalculate Blend (using Trial 4). The results are shown in the worksheet below. Aggregate: Mineral Filler Fine Aggregate Coarse Aggregate % Used: Sieve (in) % Pass % Blend % Pass % Blend % Pass % Blend Total Blend Target Value Design Range 1 1/ / / max 3/8 No. 4 No No. 30 No. 50 No. 100 No This is one possible solution. The Total Blend can be adjusted to be closer to the Target Value. VDOT and Platinum Performance Partners, LLC Chapter 7 page 21

150 Blending Aggregates 5.4 Recalculate Blend (using Trial 5). The results are illustrated below and in Figure Aggregate: Mineral Filler Fine Aggregate Coarse Aggregate % Used: Sieve (in) % Pass % Blend % Pass % Blend % Pass % Blend Total Blend Target Value Design Range 1 1/ / / max 3/8 No. 4 No No. 30 No. 50 No. 100 No Power Chart for Example 2: IM-19.0 and Aggregates Percent Passing Sieve Size (mm) 12.5 Mineral Filler Fine Aggregate Coarse Aggregate Target Value Trial 4 (20,35,45) Trial 5 (15, 40, 45) Figure Data from Step 5-4 Plotted on.45 Power Chart page 22 Chapter 7 VDOT and Platinum Performance Partners, LLC

151 Blending Aggregates AWARENESS/IMPORTANT Once the percent of each aggregate to be used has been determined and conforms to the requirements, a plant can then use these percentages to set the gates of the cold feed. The precision of the plant controls and variability of the stockpiles need to be taken into account when fine tuning aggregate percentages. Highlights a step in the procedure which is either unusual or very particular to this procedure. May also indicate awareness (additional information) or a cautionary concern in the procedure. VDOT and Platinum Performance Partners, LLC Chapter 7 page 23

152 Blending Aggregates Proportioning Aggregate at the Batch Plant DEFINITIONS. The following terms will be used throughout this section: Sampling gates Sampling device Gates or windows in the sides of the hot bins that allow the Technician to sample aggregates at the plant. A device used to obtain a representative sample of aggregates. Aggregates must also be proportioned at the batch plant to ensure that the plant is producing the desired asphalt mix. To do so, it is necessary to pull a certain amount of aggregate from each hot bin, as well as the stockpiles. It is the hot bin gradation that will be used to determine aggregate proportions. The amount that is pulled from each bin is dependent upon: What the job mix formula calls for The gradation contained in each bin. The technique used to pull the aggregate from each bin is called hot bin sampling. Hot Bin Sampling STEP 1. Start up. Start running the plant, the cold feed, the dryer and the screens. This is required to ensure that the material in the bins is representative of the proportions established at the cold gates. Only after the plant has settled down should a sample of aggregate be taken from each bin. STEP 2. Locate the sampling facilities and devices. Most hot mix asphalt concrete plants are equipped with devices for sampling hot aggregate bins. These vary from sampling gates or windows in the sides of the hot bins, to devices for diverting the flow of aggregates from the bins into sample containers. In the case of batch plants, the best place to obtain a representative sample is from the bin gates, as the material falls in the weigh hopper. Use a sampling device such as the one shown in Figure 7-11 to capture material. page 24 Chapter 7 VDOT and Platinum Performance Partners, LLC

153 Blending Aggregates Figure Sampling Device. STEP 3. Withdraw material in representative samples Properly position and pass the sampling device through the stream of material, so that all the sizes are collected and a representative sample is obtained. Correct use of the sampling device is illustrated in Figure Withdraw the sampling device before it overflows and deposit the sample in a clean container Repeat the procedure for each bin to be analyzed. Figure Correct Use of the Sampling Device VDOT and Platinum Performance Partners, LLC Chapter 7 page 25

154 Blending Aggregates The following provides background that is important for sampling success: As materials flow over the plant screens, the finer particles fall to the near side of the bins, and the coarser particles to the far side, as illustrated in Figure When material is drawn from the bins by opening a gate at the bottom, the stream consists predominately of fine material at one edge and coarse material at the other. This condition is critical in the number 1, or fine bin, since the asphalt demand is influenced by the material from this bin. The relative position of the sampling device in the stream determines whether the sample will be composed of the fine portion, the coarse portion, or will be an accurate representation of the Figure Hot Bin Sampling material in the bin. It is most important that the sampling device be properly positioned in the stream of material, so that all of the sizes are collected and a representative sample is obtained. Hot Bin Sampling Sampling improperly can ruin test results. Use proper techniques to pull samples from the hot bins: Always make sure the containers and sampling device are clean. When you hear the bin open, steadily push the sampling container down the rails and pull it back at the same speed once it reaches the end to ensure that you sample the entire stream. Do not leave the sampling container in one place to collect the sample because the stream of material coming from the bin may be segregated, with small rock on one side and large rock on the other. page 26 Chapter 7 VDOT and Platinum Performance Partners, LLC

155 Blending Aggregates Hot Bin Proportions by the Trial and Error Method DEFINITIONS. The following terms will be used throughout this section: Acceptance range Process tolerance Production tolerance The job mix formula with the tolerances applied. The amount of deviation allowed from the job mix formula. The allowable target-miss that is allowed during production before price adjustments are applied. Before the bin weights can be calculated, the proportions (percentages) required from each bin must be determined. The Trial and Error method again is the easiest method to use to determine these proportions and combined gradations for the job mix formula. Note: The steps for these calculations are the same as those covered in the previous section for cold feed and lab blending determinations. However, in this section we will be using the gradations of the batch plant s hot bins, rather than stockpile gradations. Additionally, we will cover production tolerances and acceptance ranges in this section. The production tolerance is the allowable target-miss that is allowed during production before price adjustments are applied. The acceptance range is determined by taking the job mix formula and applying the process tolerances for eight tests. These tolerances are found in the VDOT Road and Bridge Specifications, Section Table II 15. (See Figure 7-3.) VDOT and Platinum Performance Partners, LLC Chapter 7 page 27

156 Blending Aggregates Sample Problem 1: Hot Bin Proportioning STEP 1. Obtain required data from the following and enter it into the appropriate columns, as shown in the worksheet that follows: Job mix formula (TL-127) Hot bin gradations Aggregate: Bin 1 Bin 2 Bin 3 Bin 4 % Used: Sieve (in) % Pass % Blend % Pass % Blend % Pass % Blend % Pass % Blend Total Blend Job Mix Formula 1 1/ / /2 3/8 No. 4 No No. 30 No. 50 No. 100 No Accept Range STEP 2. Determine the acceptance range and enter it into the Accept Range column of the worksheet, as shown on the next page. Use Table II-15 Process Tolerance for Eight Tests (Plus and Minus Tolerance) found in Section (shown on the next page as Figure 7-14). Note: The Process tolerance is the amount above and the amount below the job mix formula that can be tolerated for a specific mix. The upper acceptance range cannot be greater than 100. To calculate the upper and lower acceptance ranges, add or subtract, respectively, the process tolerance from the job mix formula. Sieve Job Mix Formula Process Tolerance Lower Acceptance Range Upper Acceptance Range 1 ½ = = ± = = 99.8 ¾ 84 ± = = 86.8 No ± = = 38.8 No ± = = 4.7 page 28 Chapter 7 VDOT and Platinum Performance Partners, LLC

157 Blending Aggregates Aggregate: Bin 1 Bin 2 Bin 3 Bin 4 % Used: Sieve (in) % Pass % Blend % Pass % Blend % Pass % Blend % Pass % Blend Total Blend Job-Mix Formula Accept Range 1 1/ / /2 3/8 No. 4 No No. 30 No. 50 No. 100 No Table II-15. Process Tolerance for Eight Tests (Plus and Minus Tolerance), Section Process Tolerance on Each Laboratory Sieve and Asphalt Content - Percent Plus & Minus No. Tests Top Size 1.5 in 1 in 3/4 in 1/2 in 3/8 in No. 4 No. 8 No. 30 No. 50 No. 200 AC* *Asphalt content will be measured as extractable asphalt or mass after ignition Source: VDOT Road and Bridge Specifications, Section Figure Table II-15, Process Tolerance for Eight Tests VDOT and Platinum Performance Partners, LLC Chapter 7 page 29

158 Blending Aggregates STEP 3. Estimate the proportions and enter them into the appropriate columns of the worksheet, as shown below. The sum of the Bin Percentages (Total Blend) must always equal 100. Aggregate: Bin 1 Bin 2 Bin 3 Bin 4 % Used: Sieve (in) % Pass % Blend % Pass % Blend % Pass % Blend % Pass % Blend Total Blend Job Mix Formula Accept Range 1 1/ / /2 3/8 No. 4 No No. 30 No. 50 No. 100 No STEP 4. Calculate % Blend and combined gradation (Total Blend). 4.1 Calculate the individual proportions on each sieve for each of the three aggregates and enter in the column % Blend. 4.2 Add the % Blend for all bins and enter in the column Total Blend. % Blend = % Pass x Percent Aggregate Proportion Note: Change Percent Aggregate Proportion to a decimal) Total Blend = % Blend Bin 1 + % Blend Bin 2 + % Blend Bin 3 + % Blend Bin 4 Calculations: % Blend: Sieve Bin 1 Bin 2 Bin 3 Bin 4 1 1/2 100 x.25 = x.25 = x.25 = x.25 = x.25 = x.25 = x.25 = x.25 = /4 100 x.25 = x.25 = x.25 = x.25 = 8.8 No x.25 = x.25 = x.25 = 0 0 x.25 = 0 No x.25 = x.25 = 0 0 x.25 = 0 0 x.25 = 0 page 30 Chapter 7 VDOT and Platinum Performance Partners, LLC

159 Blending Aggregates Total Blend: Sieve Bin 1 + Bin 2 + Bin 3 + Bin 4 = Total Blend 1 1/ = = 98.3 or 98 3/ = 81.3 or 81 No = 25.3 or 25 No = 3.0 Worksheet results after Step 4.2: Aggregate: Bin 1 Bin 2 Bin 3 Bin 4 % Used Sieve (in) % Pass % Blend % Pass % Blend % Pass % Blend % Pass % Blend Total Blend Job Mix Formula Accept Range 1 1/2 in in /4 in /2 in 3/8 in No. 4 No No. 30 No. 50 No. 100 No VDOT and Platinum Performance Partners, LLC Chapter 7 page 31

160 Blending Aggregates STEP 5. Compare combined gradation in the Total Blend column with the Target Value in the Job Mix Formula column and acceptance range data in the Accept Range column. Aggregate: Bin 1 Bin 2 Bin 3 Bin 4 % Used Sieve (in) % Pass % Blend % Pass % Blend % Pass % Blend % Pass % Blend Total Blend Job Mix Formula Accept Range 1 1/2 in in /4 in /2 in 3/8 in No. 4 No No. 30 No. 50 No. 100 No Note that the No. 8 sieve Total Blend column value is below the Job Mix Formula column value and is outside of the acceptance range. As a result, we will need to make adjustments to the % Used values for each of the hot bins. 5.2 Use one sieve to make an adjustment before recalculating all sieves. Aggregate: Bin 1 Bin 2 Bin 3 Bin 4 % Used Trial 1 % Used Trial 2 % Used Trial 3 Sieve (in) % Pass % Blend % Pass % Blend % Pass % Blend % Pass % Blend Total Blend Job-Mix Formula Accept Range No. 8 (T1) No. 8 (T2) No. 8 (T3) Conclusion from this table: Use third trial to recalculate the rest of the sieves. page 32 Chapter 7 VDOT and Platinum Performance Partners, LLC

161 Blending Aggregates 5.3. Recalculate Blend (using Trial 3). The results are illustrated in the worksheet below. Aggregate: Bin 1 Bin 2 Bin 3 Bin 4 % Used Sieve (in) % Pass % Blend % Pass % Blend % Pass % Blend % Pass % Blend Total Blend Job-Mix Formula Accept Range 1 1/2 in in /4 in /2 in 3/8 in No. 4 No No. 30 No. 50 No. 100 No VDOT and Platinum Performance Partners, LLC Chapter 7 page 33

162 Blending Aggregates Calculating Batch Weights After determining the proportions required for each hot bin, we can calculate the weight of asphalt binder and the amount of aggregate to be pulled from each bin to produce a single batch of hot mix asphalt. The following section provides procedural information to accomplish this task. Calculating Batch Weights The following outlines the procedure for calculating batch weights: Determine batch size Determine asphalt content Obtain bin percentages Calculate the weight of the asphalt and aggregate Calculate the weight of the aggregate per bin Calculate the accumulative weight per bin STEP 1. Determine batch size, which will be mainly dependent upon the pugmill capacity of the asphalt plant. (This is usually the manufacturer s rated pugmill capacity.) For example, a 6000 lb. pugmill has 6000 lb. batch size. STEP 2. Determine asphalt content. This is obtained from TL-127 (example form is shown on page 7-4 of this chapter). Example: 4.2% STEP 3. Determine the Bin Percentages through the Trial and Error method. For this example we will use: 35, 20, 20 and 25 percent, for bins 1, 2, 3 and 4 respectively. STEP 4. Calculate the weight of the asphalt and aggregate. Weight of Asphalt = Pugmill Size x Asphalt Content Note: Remember to change Asphalt Content value to decimal format. Weight of Asphalt = 6000 lb. x.042 = 252 lb. Weight of Aggregate = Pugmill Size Weight of Asphalt. Weight of Aggregate = 6000 lb. 252 lb. = 5748 lb. page 34 Chapter 7 VDOT and Platinum Performance Partners, LLC

163 Blending Aggregates STEP 5. Calculate the weight of aggregate per bin. Weight per Bin = Weight of Aggregate x Bin Percentage Note: Remember to change the bin percentage to decimal. Weight Bin 1 = 5748 x.35 = Weight Bin 2 = 5748 x.20 = Weight Bin 3 = 5748 x.20 = Weight Bin 4 = 5748 x.25 = 1437 STEP 6. Calculate the accumulative weight per bin. Bin 1 = Bin 1 Bin 2 = Bin 1 + Bin 2 Bin 3 = Bin 1 + Bin 2 + Bin 3 Bin 4 = Bin 1 + Bin 2 + Bin 3 + Bin 4 Bin 1 = Bin 2 = = Bin 3 = = 4311 Bin 4 = = 5748 AWARENESS/IMPORTANT The final accumulative bin weight should always equal the initial weight of aggregate. Highlights a step in the procedure which is either unusual or very particular to this procedure. May also indicate awareness (additional information) or a cautionary concern in the procedure. VDOT and Platinum Performance Partners, LLC Chapter 7 page 35

164 Blending Aggregates Chapter Seven Knowledge Check 1. Where are the design range limits found for the different types of asphalt concrete mixtures? 2. If the job mix on the 1/2 inch sieve is 81% passing, what is the acceptance range for the eight tests? 3. To whom should the job mix be submitted? 4. The range from which the job mix is chosen is called: A. Standard deviation B. Design range C. Process tolerance D. Acceptance range 5. The Trial and Error method is commonly used to determine the relative proportions of different aggregates needed to produce a final gradation that meets specifications. A. True B. False 6. The target values for the combined gradation are provided by: A. The Asphalt Producer B. The District Materials Engineer C. The Asphalt Mix Design Technician D. Table II-13 in the Road and Bridge Specifications page 36 Chapter 7 VDOT and Platinum Performance Partners, LLC

165 Blending Aggregates Study Problem 1: Cold Feed Blending Determine the Job Mix Formula (Total Blend). Type Mix: SM-12.5A Aggregate: Screenings Stone % Used: Sieve (in) % Pass % Blend % Pass % Blend Total Blend Target Value 1 1/2 in 1 in 3/4 in /2 in /8 in No. 4 No No. 30 No. 50 No Design Range Study Problem 2: Cold Feed Blending Determine the Job Mix Formula (Total Blend). Type Mix: IM-19.0D Aggregate: No. 10 1/2 Cr/ Run No. 68 % Used: Sieve (in) % Pass % Blend % Pass % Blend % Pass % Blend Total Blend Target Value 1 1/2 in 1 in /4 in /2 in /8 in No. 4 No No. 30 No. 50 No Design Range VDOT and Platinum Performance Partners, LLC Chapter 7 page 37

166 Blending Aggregates Study Problem 3: Cold Feed Blending Determine the Job Mix Formula (Total Blend). Type Mix: SM-12.5D Aggregate: No. 78 No. 10 Sand % Used: Sieve (in) % Pass % Blend % Pass % Blend % Pass % Blend Total Blend Target Value 1 1/2 in 1 in 3/4 in /2 in /8 in No. 4 No No. 30 No. 50 No Design Range page 38 Chapter 7 VDOT and Platinum Performance Partners, LLC

167 Blending Aggregates Study Problem 4: Hot Bin Blending Batch plant set up: A. Determine hot bin proportions. 1. Determine the percentage to be pulled from each bin to meet the job mix formula. 2. Show blend determined under the Total Blend column. 3. Show acceptance range in the Accept. Range column. Type Mix: BM-25.0 Aggregate: Bin 1 Bin 2 Bin 3 Bin 4 % Used: Sieve (in) % Pass % Blend % Pass % Blend % Pass % Blend % Pass % Blend Total Blend Job-Mix Formula 1 1/2 in in /4 in /2 in 3/8 in No. 4 No No. 30 No. 50 No Accept Range B. Using the percentage determined to be pulled from each bin above and an asphalt content of 4.5%, calculate the weight of asphalt, weight of aggregates from each bin, and accumulative weights per bin to be pulled in an 8000 pound batch. Bin 1 Bin 2 Bin 3 Bin 4 Percent Weight of Asphalt Weight of Aggregates per Bin Accumulative Weights per Bin VDOT and Platinum Performance Partners, LLC Chapter 7 page 39

168 Blending Aggregates Study Problem 5: Hot Bin Blending Batch Plant set up: A. Determine hot bin proportions. 1. Determine the percentage to be pulled from each bin to meet the job mix formula. 2. Show blend determined under column listed total blend. 3. Show acceptance range in column listed acceptance range. Type Mix: IM-19.0 A Aggregate: Bin 1 Bin 2 Bin 3 Bin 4 % Used Sieve (in) % Pass % Blend % Pass % Blend % Pass % Blend % Pass % Blend Total Blend Job-Mix Formula 1 1/2 in 1 in /4 in /2 in /8 in No. 4 No No. 30 No. 50 No Accept Range B. Using the percentage determined to be pulled from each bin above and an asphalt content of 4.7%, calculate the weight of asphalt, weight of aggregates from each bin, and accumulative weights per bin to be pulled in a 5500 pound batch. Bin 1 Bin 2 Bin 3 Bin 4 Percent Weight of Asphalt Weight of Aggregates per Bin Accumulative Weights per Bin page 40 Chapter 7 VDOT and Platinum Performance Partners, LLC

169 MCS: Asphalt Plant Certification 8 Duties of the Technicians Contractors and VDOT must work together to ensure that the product produced and delivered meets specifications for each project or job. Our mutual goal is to ensure that we can safely and efficiently produce the critical outcomes for each job and achieve the goals of each job. VDOT employs a Quality Assurance (QA) program to ensure that quality asphalt concrete mixtures (HMA) are produced and placed throughout the Commonwealth. These include: Superpave asphalt mixtures Stone matrix asphalt (SMA) Porous Friction Course (PFC) Thin hot mix asphalt concrete overlay (THMACO) This QA program consists of a materials acceptance and Quality Assurance (QA) program quality control (QC) and acceptance testing by the contractor, as well as verification sampling and testing (VST) and independent assurance (IA) testing and observation by the VDOT. In this chapter, we examine the primary duties, certification requirements and responsibilities of the Contractor Technicians that flow from these programs, and the responsibilities of VDOT to monitor and maintain quality. Learning Objectives: Upon completion of this chapter, you should be able to: Discuss the primary duties of each party in the QA and QC Programs Demonstrate how to conduct split sampling Define stratified random sampling and list the major tasks it requires Explain how to create and use control charts Describe the primary duties, certifications and bonds required of the Weighperson Describe how the referee system works VDOT and Platinum Performance Partners, LLC Chapter 8 page 1

170 Duties of thetechnicians An Overview of Roles and Responsibilities The certified roles and responsibilities that are introduced in this chapter are summarized in the two tables that follow. Contractor Role Responsibility Asphalt Mix Design Technician (Level II) Asphalt Plant Technician (Level I) Responsible for the design and control of asphalt mixtures produced for the VDOT Perform all tests necessary to put the plant into operation, and sample all mixes and components of mixtures produced at the plant Assist the AMDT in mix design and monitoring of all components of asphalt mixtures produced at the plant Weighperson Responsible for certifying the load of each truck shipping asphalt mixtures to a VDOT project Tracks accumulated asphalt tonnages shipped to VDOT projects on a per JMF/Project/Day basis VDOT Role Responsibility District Materials Engineer Responsible for the execution of the VDOT s QA Program on all materials supplied to VDOT projects Approves asphalt Job Mix Formulas for all mixes produced for the VDOT in the district QA Monitor Responsible for the day-to-day operation of the QA Program at the asphalt plant page 2 Chapter 8 VDOT and Platinum Performance Partners, LLC

171 Duties of thetechnicians Contractor s Responsibility DEFINITIONS. The following terms will be used throughout this section: Lot Stratified random sample Control chart Statistical control Normal Distribution Quantity of material to be checked for compliance with specifications. Samplings from equal portions of a lot at locations that have been selected solely by chance. Graphical record of data taken from a repetitive process. When repeated measurements from a process are normally distributed around a target value. A pattern for the distribution of a set of data which follows a bell shaped curve. In this section of the chapter we will explore the roles for which the Contractor is responsible. The Asphalt Mix Design and Plant Technicians The Contractor shall have a VDOT-certified Asphalt Mix Design Technician (AMDT) to see that all component materials have been approved for use, are being stored and handled properly, and are combined into a mixture that meets all specification requirements. The AMDT or the Asphalt Plant Technician must be capable of conducting any tests necessary to put the plant into operation and produce a mixture that meets all specification requirements. These job roles require the Asphalt Plant Mix Design (Level II) or Asphalt Plant (Level I) certification, respectively. Duties for which the Asphalt Mix Design Technician is responsible are illustrated in Figure 8-1 and detailed in the text that follows. VDOT and Platinum Performance Partners, LLC Chapter 8 page 3

172 Duties of thetechnicians Notifies Others When Production Starts or Resumes Plots & Maintains Control Charts Assures that Materials Are Handled & Stored Properly Samples & Tests Hot Mix Asphalt to Ensure Product Acceptance Reviews & Approves Results of All Testing & Communicates Adjustments Designs & Submits Job Mix Formula & Superpave Mix Design Data Figure 8-1. Primary Responsibilities of the Asphalt Mix Design Technician Notifies Others When Production Starts or Resumes The Contractor/Technician must notify the District Materials Engineer when production is to start or resume after a delay. Assures that Materials Are Handled & Stored Properly The Contractor/Technician must assure that all materials are properly handled and stored to prevent them from becoming unsuitable for use. Aggregates for asphalt concrete should be handled and stored to minimize segregation and to prevent contamination with deleterious substances. The Contractor/Technician also must ensure that the proper kind of binder is used, as shown on the job mix formula. He/she is also responsible for seeing that the binder is handled and stored properly. AWARENESS/IMPORTANT Binder used for State work must come from suppliers listed on the VDOT s Approved List for PG Binder Suppliers. Highlights a step in the procedure which is either unusual or very particular to this procedure. May also indicate awareness (additional information) or a cautionary concern in the procedure. page 4 Chapter 8 VDOT and Platinum Performance Partners, LLC

173 Duties of thetechnicians Designs & Submits Job Mix Formula & Superpave Mix Design Data Before any asphalt concrete is produced, the AMDT shall submit, for the District Materials Engineer s approval, a job mix formula for each mixture to be supplied, along with Superpave mix design data. A sample job mix formula (Form TL-127) is provided in Chapter 7 (page 7-4). Reviews & Approves Results of Testing & Communicates Adjustments The AMDT will review and approve the results of all testing. He/she shall be available and in direct communication with the plant to enable him/her to make necessary adjustments in the asphalt concrete mixes at the mixing plant. Samples & Tests Hot Mix Asphalt to Ensure Product Acceptance The AMDT must perform the following sampling and testing tasks: Sampling hot mix asphalt (HMA), utilizing an approved random method Testing in accordance with the specifications Recording test results and furnishing copies to VDOT Maintaining current quality control charts at the plant for review by VDOT Maintaining all records and test results associated with asphalt concrete materials production. Test Specifications Test specifications that must be followed when completing these tasks include: 1. A rate of 8 samples per 4000 ton lot is to be used. An 8000 ton lot may be used when normal production exceeds 4000 tons per day, with approval by the Engineer. 2. Samples are to be obtained from the approximate center of truckloads of material. 3. A statistically acceptable method of randomization is to be used to determine the time the stratified random sample is to be taken. The AMDT and Plant Technician must be able to conduct three specific types of sampling functions: Sampling from the truck Split sampling Statistical sampling VDOT and Platinum Performance Partners, LLC Chapter 8 page 5

174 Duties of thetechnicians Sampling from the Truck. Samples used for Acceptance and Quality Assurance must be sampled from the truck. To sample from a truck: 1. Take the sample from the approximate center of the truckload. 2. Strike off the top six inches of material. 3. Take the sample horizontally, 8-12 inches below the surface of the load. Splitting Samples for Quality Assurance Testing. The Technician also must be able to conduct split sampling, at the request of VDOT. In split sampling, the Technician analyzes half of the sample and VDOT analyzes the other half as part of the VDOT Quality Assurance program. This split sample shall be quartered or processed through a sample splitter in accordance with standard procedures, the quartering method is summarized in Figure Divide the sample. 2. Quarter the sample. 3. Remove the two opposing quarters. Figure 8-2. Summary of the Quartering Method for Sampling The contractor s portion of the split sample will be used as the next production acceptance sample. Properties to be determined include, but are not limited to: Gradation Asphalt content Temperature (at time of sampling) Statistical Sampling. VDOT uses a statistical (i.e., a mathematical analysis of accumulated data) method for product acceptance. This allows the Contractor/Technician to exercise product control, while VDOT exercises product acceptance. VDOT accepts or rejects material based on the average of test results, instead of accepting or rejecting material on an individual sample results. An important phase of any acceptance or rejection plan is the process of sampling. Statistical sampling is performed because individuals cannot consistently select, by eye, a sample that truly typifies the entire quantity of material to be checked for compliance with specifications. Statistical page 6 Chapter 8 VDOT and Platinum Performance Partners, LLC

175 Duties of thetechnicians systems require that samples be taken in such a manner that every part of the quantity of material to be checked for compliance has an equal chance of being sampled. This means that samples must be taken randomly. Another important part of any acceptance or rejection plan is the quantity of material to be checked for compliance with specifications. In statistical quality control, the term lot is used to denote the quantity of material to be checked for compliance with specifications, then accepted, rejected or subjected to adjustment. In Virginia, lot sizes are typically 4000 tons; 8000 ton lots may be used when the normal daily production of the source from which the material is obtained is in excess of 4000 tons. In order for the Asphalt Plant Technician to use statistical quality control properly, he/she must know the following information: When to take a sample Where to take a sample How to take a sample How to test the sample What to do with the test results Statistical quality control of asphalt concrete utilizes random sampling within a lot. Virginia s Statistical Quality Control Program, however, goes one step further than just random sampling. VDOT uses the stratified random sampling method. Stratified random sampling is sampling from equal portions of a lot at locations that have been selected solely by chance. Any statistically acceptable method of randomization may be used to determine the time and location of the stratified random sample to be taken. However, VDOT shall be advised of the method to be used prior to beginning production. How to Conduct Stratified Random Sampling. The following is a description and discussion of the step-by-step procedures used in the stratified random sampling method. 1. Determine the lot size (4000 or 8000 ton lots), based on the normal daily production of the plant from which the material is being obtained. The ton is selected each day before beginning production. 2. Stratify the lot: 500 tons per sample for 4000 ton lots or 1000 tons per sample for 8000 ton lots, with 8 samples per lot regardless of lot size. One sample shall be on or between each group of tons, shown in the table that follows: VDOT and Platinum Performance Partners, LLC Chapter 8 page 7

176 Duties of thetechnicians 4000 ton lot 8000 ton lot Secure four sets of numbers from a Random Number Table. The first number of each set will represent which ton is to be sampled. 4. Record these numbers. The Technician should notify the Weighperson of the ton number selected so that he/she can notify the Technician as to which truck contains the ton to be tested. The Weighperson and the Technician should be the only ones who know which ton is to be sampled. Below is an example for a 4000 ton lot, using Random Numbers Table 1 (page 8-10): Note: The Random Number Tables presented here are just one of many acceptable methods available for selecting random numbers. The method the Technician uses must be approved by the Engineer prior to production. Ton Ton to be Sampled.192 1st sample 0 + (.192 x 1000) = 192 ton.432 2nd sample (.432 x 1000) = 932 ton.143 3rd sample (.143 x 1000) = 1143 ton.214 4th sample (.214 x 1000) = 1714 ton.353 5th sample (.353 x 1000) = 2353 ton.038 6th sample (.038 x 1000) = 2538 ton.021 7th sample (.021 x 1000) = 3021 ton.405 8th sample (.405 x 1000) = 3905 ton page 8 Chapter 8 VDOT and Platinum Performance Partners, LLC

177 Duties of thetechnicians Below is an example for an 8000 ton lot, using Random Numbers Table 2 (page 8-11): Ton Ton to be Sampled.822 1st sample 0 + (.822 x 1000) = 822 ton.826 2nd sample (.826 x 1000) = 1826 ton.495 3rd sample (.495 x 1000) = 2495 ton.160 4th sample (.160 x 1000) = 3160 ton.379 5th sample (.379 x 1000) = 4379 ton.558 6th sample (.558 x 1000) = 5558 ton.452 7th sample (.452 x 1000) = 6452 ton.278 8th sample (.278 x 1000) = 7278 ton VDOT and Platinum Performance Partners, LLC Chapter 8 page 9

178 Duties of thetechnicians Random Numbers Table 1 (Range ) page 10 Chapter 8 VDOT and Platinum Performance Partners, LLC

179 Duties of thetechnicians Random Numbers Table 2 (Range ) VDOT and Platinum Performance Partners, LLC Chapter 8 page 11

180 Duties of thetechnicians Plots & Maintains Control Charts The Asphalt Mix Design Technician also plots and maintains control charts. A control chart is a graphical record of data taken from a repetitive process. A process is in statistical control when repeated measurements from the process behave as random samples dispersed around a target value. The control chart used for asphalt concrete is based on the normal bell shape curve, which is illustrated in Figure 8-3. The control guides are obtained from standard deviations for the particular sieves and asphalt content. By using these guides and plotting the individual test results, the Contractor/Technician can predict when the process is getting out of control by using the warning signals that are shown on Figure 8-3 and in the Process Tolerance Warning Signals procedure box on the next page. Figure 8-3. Bell Curve, Showing Standard Deviations page 12 Chapter 8 VDOT and Platinum Performance Partners, LLC

181 Duties of thetechnicians Process Tolerance Warning Signals When one (1) test result exceeds the number one warning signal (i.e., two standard deviations from the job mix), the Contractor/Technician should investigate his/her process due to the fact that approximately 95% of the material should fall within this range. When three (3) consecutive test results exceed the number two warning signal (i.e., one standard deviation from the job mix), the Contractor/Technician should investigate his/her process, since approximately 68% of the material should fall within this range. When eleven (11) consecutive test results fall on the same side of the job mix, the Contractor/Technician should also investigate his/her process. Eleven (11) is the statistical number that could indicate the JMF is no longer the mean of the test results and the Contractor/Technician is not getting full benefit of the process tolerances. Department policy now requires the Contractor to plot his/her own control charts. If he/she desires, the Department will furnish, set-up, and help him/her to get started in the plotting. Figure 8-4 on the next page depicts samples of these charts. How to Plot Control Charts. Follow these steps to plot control charts: 1. Fill out the heading as indicated on the chart. 2. Put in the appropriate control sieves for the particular type of mix. 3. Fill in the proper job mix values for the appropriate sieves from the job mix formula. 4. Draw in control guides (listed at the bottom of sheet for all sieve sizes) on approximate control sieves in different colors. Example: Red lines for one-point controls and blue lines for three-point controls. 5. As soon as test values have been obtained on an individual sample, plot these values on their proper Control Sieve Chart. 6. After all eight samples of a lot have been run, average the test results and plot these over the fourth test number of the lot. AWARENESS/IMPORTANT Test averages must be plotted in a different color than individual test results. Highlights a step in the procedure which is either unusual or very particular to this procedure. May also indicate awareness (additional information) or a cautionary concern in the procedure. VDOT and Platinum Performance Partners, LLC Chapter 8 page 13

182 Duties of thetechnicians ASPHALT CONTENT: JM =5.6 AC RANGE = 5.3 TO LOT/ DATE SAMPLE TON 1 BLOCK = 0.05% - 19-Nov 1/ /2 20-Nov 1459 *1/3 21-Nov /4 22-Nov 422 *2/1 25-Nov 767 2/2 26-Nov /3 27-Nov /4 28-Nov 45 3/1 29-Nov Figure 8-4. Gradation Control Chart page 14 Chapter 8 VDOT and Platinum Performance Partners, LLC

183 Duties of thetechnicians The Weighperson The Asphalt Concrete Producer or Contractor will supply their own Weighperson, shown at work in Figure 8-5. This person must be bonded unto the Commonwealth of Virginia in the amount of Ten Thousand Dollars ($10,000) and shall be certified by the District Materials Engineer that he/she is competent to perform the duties of a Weighperson. An example of the Weighperson Certification is illustrated in Figure 8-6. An example of the Weighperson Surety Bond (Form TL-103) appears as Figure 8-7. Since the bonded Weighperson is an employee of the Producer or Contractor, no administrative supervision is received from the VDOT s Resident Engineer or District Materials Engineer. Figure 8-5. The Weighperson at Work The Weighperson does, however, receive technical guidance from the District Materials Engineer and his/her staff. Figure 8-6. Weighperson Certification VDOT and Platinum Performance Partners, LLC Chapter 8 page 15

184 Duties of thetechnicians Form TL 103 Bond Number June 2, 2002 WEIGHPERSONS SURETY BOND FOR CONTRACTORS AND PRODUCERS OF MATERIAL FURNISHED BY THE TON KNOWN ALL MEN BY THESE PRESENTS: THAT of the City/County of, State of doing business under the firm name of an individual, partnership, or corporation as PRINCIPAL, and the, a corporation, authorized to do business in the Commonwealth of Virginia, as SURETY, are held and firmly bound, effective the day of, 20, unto the Commonwealth of Virginia, as obligee, in the full and just sum of Ten Thousand Dollars ($10,000) for the payment whereof well and truly to be made to the Commonwealth of Virginia, we bind ourselves, our successors and assigns,jointly and severally, firmly by these presents: WHEREAS, the herein before mentioned principal desires to conduct the business of furnished materials by the ton for incorporation in Virginia Department of Highways and Transportation road and bridge construction and maintenance work. The condition of this obligation is such that, whereas, the above bound principal is or is about to conduct business as outlined above for which a surety bond is required. NOW, THEREFORE, if the above bound principal will faithfully observe and perform the duties required by Section 109, Measurement of Quantities, of the Virginia Department of Highway s and Transportation Road and Bridge Specifications, as amended, and indemnify said obligee, then the above obligation shall be void, otherwise to be and remain in full force and effect. The continuing nature of this bond is such that it is required to be renewed annually on its anniversary date except the principal or the surety may terminate their obligations under this bond by giving sixty days notice, in writing, by registered mail, to the obligee. IN WITNESS WHEREOF the said principal has hereunder set his or its hand and affixed his or its seals and the said surety has caused its corporate name to be signed hereto and its corporate seal to be affixed hereunto by its duly authorized official or agent and executed this instrument the day of, 20. Principal Corporate Seal Principal BY: President or Vice President Surety Corporate Seal Figure 8-7. Weighperson Surety Bond Surety page 16 Chapter 8 VDOT and Platinum Performance Partners, LLC

185 Duties of thetechnicians Primary Duties of a Weighperson The primary duties of a Weighperson are as follows: 1. Ensure that trucks are properly tared and in compliance with specifications and instructions. 2. Assure that all weights are true and correct. 3. Post in the scale house the: Certification, Surety Bond and current Virginia Weights and Measures Scale Inspection Report. 4. Furnish a signed weigh ticket for each load weighed. The ticket must include the date, truck number, load number, plant name, size and type of material, project, schedule or purchase order number and the weights specified herein. 5. Maintain sufficient documentation, such that the accumulative tonnage within each lot of material and the distribution of each lot of material by contract can be readily identified. 6. Submit by the end of the next working day, to each contract, a summary of the number of loads and total weights for each type of asphalt concrete material (on a TL-102A). Summaries can be mailed no later than the Monday following the calendar week of delivery in the following cases: In the case of sporadic deliveries of tonnage material for purchase orders In the case that it is impractical for load summaries to be submitted by the end of the next working day, as required. It is up to the Weighperson to determine the method used to keep account of the tonnage of material that went to a particular project or maintenance purchase order and from which lot that material originated. However, the method of accountability must be efficient enough so that the District Materials Engineer can easily determine which project or projects received material from a lot in question. One of the major duties of the Weighperson is to submit a daily summary sheet to the Project Inspector by the end of the next working day following delivery to the construction project. An example of this summary sheet is shown in Figure 8-8. As can be noted from this example, information is included about the material shipped, the project (or purchase order if that is the case), who produced the material, the number of loads of material shipped, and the lots from which this material was produced. The Weighperson should also include the number of tons of material that were shipped from each lot indicated. VDOT and Platinum Performance Partners, LLC Chapter 8 page 17

186 Duties of thetechnicians Figure 8-8. Daily Summary Sheet On the portion of the Weighperson daily summary sheet labeled Department s Verification, the Inspector confirms if the tonnage of material indicated by the bonded Weighperson was received on the project. In this example, all material shipped was received on the project. If two loads of this material page 18 Chapter 8 VDOT and Platinum Performance Partners, LLC

187 Duties of thetechnicians were rejected for some reason (e.g., failed visual inspection), then the inspector would list the total tonnage of material received on the project and place this total under Tons Received. This tonnage should agree with the total tons as shown by the Weighperson. Then the Inspector would place total tonnage of the material rejected under Tons Deducted. The tonnage from these two lines are then subtracted and placed under Total Tons. The reason for the material deduction would then be given under the heading Reason for Differences. The Inspector s copies of the daily summary sheets are turned in at the end of the project and are checked against the final estimate and weigh tickets. The specifications make it necessary to note a particular situation in which the Weighperson would need to divide or split tonnage of an individual truckload to accumulate enough tons to complete a lot. The following example is designed to explain a procedure that may be used. Note: The form used in this example is for illustrative purposes only and, therefore, should not be considered as a standard form for the Weighperson. At the end of the first day s operation, accumulative tons of asphalt concrete, of Type BM-25.0, has been produced, as shown in the example in Figure 8-9. Figure 8-9. Day 1 Accumulating Tonnage Example, Sheet 1 of 1 VDOT and Platinum Performance Partners, LLC Chapter 8 page 19

188 Duties of thetechnicians As Figure 8-10 indicates, on the second day of operation, the first truck contains tons of BM The accumulative tons for that load would be At 11:02 A.M. of the second day, accumulative tons of material has been produced. (Continue on next page.) Figure Day 2 Accumulating Tonnage Example, Sheet 1 of 2 page 20 Chapter 8 VDOT and Platinum Performance Partners, LLC

189 Duties of thetechnicians The next truck contains tons of material and is the 181st load in truck No. 74. Four (4) of the tons of BM from this truck are needed to complete the 2000 ton for Lot 1, as Figure 8-11 illustrates. Figure Day 2 Accumulating Tonnage Example, Sheet 2 of 2 VDOT and Platinum Performance Partners, LLC Chapter 8 page 21

190 Duties of thetechnicians VDOT s Responsibility DEFINITIONS. The following terms will be used throughout this section: Referee system IA sampling A system to allow for additional sampling and testing when there is doubt that the original test results are valid. Sampling that is conducted for the purpose of independent assurance. The Virginia Department of Transportation (VDOT) is responsible for: 1. Providing classroom technical instruction, examination and certification for all appropriate personnel. 2. Inspecting the plant before production begins to check for compliance with specification requirements governing plant and testing equipment. A record shall be prepared on a checklist-type form of all items covered during the plant inspections by the District Materials Engineer s representative. 3. Performing unannounced, periodic inspections of plants during production, including that of: Stockpiles Equipment Weighing operations Sampling Testing Records kept by the Contractor's technicians. Plants with a history of producing good materials and having well-trained personnel might be inspected as seldom as once a year, but plants with poor records should be inspected more often. A copy of the inspection report must be retained for district use and a copy forwarded to the State Materials Engineer. 4. Keeping a diary of plant visits, observations and comments made to the Contractor's representative. 5. Accepting the product in accordance with the specifications, based upon the Contractor's test results as illustrated in Figure 8-12, provided such results are statistically comparable to the Department's IA test results (as defined by VTM 59), shown in Figures 8-13 and page 22 Chapter 8 VDOT and Platinum Performance Partners, LLC

191 Duties of thetechnicians Figure Price Adjustment Test Report The sole purpose of the IA sample, taken by the Producer's Certified Technician in the presence of the QA Monitor, is to verify the accuracy of the Producer's testing program. If the comparisons indicate the IA test results are not in agreement with the Contractor's results, the VDOT will investigate to determine the source of the difference. The decision table that follows guides decision making when identifying and explaining any differences that exist. CONDITION IF an assignable cause can be determined for the difference IF an assignable cause cannot explain the difference IF it is determined that the contractor's test results are not representative of the product ACTION THEN the material will be accepted, adjusted or rejected in accordance with the specification. THEN the Department may call for the referee system to determine the final disposition of the material. THEN the Department will take such action as it deems appropriate to protect the interest of the Commonwealth. VDOT and Platinum Performance Partners, LLC Chapter 8 page 23

192 Duties of thetechnicians 6. Providing a referee system, which may be invoked at the request of the Contractor or Department, and which will require the sampling and testing of material taken from the roadway where the questionable material was placed. 7. Monitoring sampling during the first production week. If the production is less than 30,000 tons, sample 4-10 samples per type mix. Thereafter, the sample for production must follow the specifications depicted in the table below: PRODUCTION CONDITION Under 20,000 tons SAMPLE COUNT 2 samples per production week 20,000 to 29,999 tons 3 samples per production week 30,000 to 49,999 tons 4 samples per production week 50,000 to 79,999 tons 5 samples per production week 80,000 tons or more 6 samples per production week AWARENESS/IMPORTANT Samples shall be taken in accordance with VTM 48, and split from the Producer's sample, such that each half is not less than 10 lb. Highlights a step in the procedure which is either unusual or very particular to this procedure. May also indicate awareness (additional information) or a cautionary concern in the procedure. The rate of IA sampling is mandatory and it is the responsibility of the District Materials Engineer to see that it is accomplished. Should the monitoring effort fall behind the required frequency of sampling/testing, the District Administrator is to be advised immediately. Sufficient personnel are to be provided for the monitoring effort. The results of the Contractor s acceptance samples and the Department s IA samples will be used to create datasets that are constantly reviewed and compared throughout production. Matched Comparison Report. The average and variability of the split samples will be monitored using the paired t and F tests. These paired (Matched) statistics are designed to evaluate procedures and equipment, as both labs will be testing identical samples due to the splitting procedure. page 24 Chapter 8 VDOT and Platinum Performance Partners, LLC

193 Duties of thetechnicians A non-comparison on the Matched Comparison Report should trigger the following checks in both labs: Check the splitting procedure itself, to ensure VTM 48 is being followed exactly Check the procedures used in the labs to further reduce the sample to testing size Check all scales, sieves and ovens used to conduct the testing Non-Matched Comparison Report. The average and variability of the Department s samples will be compared to the Contractor s acceptance samples that do not have corresponding VDOT split samples using the student t and F tests. These Non-Matched statistics are designed to verify that material consistency is being maintained when the Department has not sampled the production period. The success of the Quality Assurance Program will be determined to a large extent by the effectiveness of the monitoring effort. Deficiencies revealed through this effort should be addressed promptly and decisively. The State Materials Engineer is to be consulted in the event of a possible deliberate act of omission or commission on the part of a Contractor which compromises the rights and/or interests of the Department. 8. Observing the manner in which sampling is performed by the Contractor. Not only is the "when," "where" and "how" of taking the sample important, but also the care that is taken to properly reduce the sample to testing size. Directing and Observing Proper Sampling The Department s representative will direct when the sample shall be taken. He/she will observe the Contractor/Technician taking and splitting (quartering) the sample. The Department s representative will take one-half of the sample to serve as the IA. The Contractor/Technician will perform the tests on the other half, which shall be considered as the next quality control sample for the Contractor. The sample size shall be such that, when properly halved, each sample should be not less than 10 lbs. VDOT and Platinum Performance Partners, LLC Chapter 8 page 25

194 Duties of thetechnicians Virginia Department of Transportation Materials Division Bituminous Concrete Comparison Analysis Report Figure Sample Comparison Analysis Report page 26 Chapter 8 VDOT and Platinum Performance Partners, LLC

195 Duties of thetechnicians Virginia Department of Transportation Materials Division Bituminous Concrete Matched Comparison Analysis Report Figure Sample Matched Comparison Analysis Report (Form E ) VDOT and Platinum Performance Partners, LLC Chapter 8 page 27

196 Duties of thetechnicians The Referee System In the event the test results obtained from one of the eight samples or the mean (average) of the eight samples taken to evaluate a particular lot appear to be questionable, the referee system, upon receipt of written request, will be applied as follows: 1. In the event the test results obtained from one of the eight samples taken to evaluate a particular lot appear to be questionable, the Contractor may request in writing that the results of the questionable sample be disregarded, whereupon the Contractor shall have either an AASHTO-accredited laboratory or the Department laboratory perform tests on five additional samples taken from randomly selected locations in the roadway where the lot was placed. In the event the Engineer determines that one of the eight test results appears to be questionable, the Department will perform tests on five additional samples taken from the randomly selected locations in the roadway where the lot was placed. The test results of the seven original (i.e. unquestioned), samples will be averaged with the test results of the five road samples, and the mean of the test values obtained for the twelve samples will be compared to the requirements for the mean of twelve tests as specified in Table II-15, represented as Figure 8-15 on the next page. 2. In the event the Contractor questions the mean of the eight original test results obtained for a particular lot, the Contractor may request in writing approval to have either an AASHTOaccredited laboratory or Department laboratory perform additional testing of that lot. In the event the Engineer determines that the mean of the eight original test results are questionable, the Department will perform additional testing of that lot. The test results of the eight samples will be averaged with the test results of the four additional samples taken from randomly selected locations in the roadway where the lot was placed, and the mean of the test values obtained from the twelve samples will be compared to the requirements for the mean of twelve tests as specified in Table II-15. If the Contractor requests additional tests, the Contractor shall sample the material and have either an AASHTO-accredited laboratory or Department laboratory test the material in accordance with Department-approved procedures. The Engineer may opt to observe the sampling and testing. In the event the mean of the test values obtained for the twelve samples conforms to the requirements for the mean of twelve tests, the material will be considered acceptable. In the event that the mean of the test values obtained for the twelve samples does not conform to the requirements for the mean result of twelve tests, the lot will be adjusted in accordance with the adjustment rate specified in Section of the specifications. page 28 Chapter 8 VDOT and Platinum Performance Partners, LLC

197 Duties of thetechnicians Samples of the size shown herein shall be saw cut by the Contractor for testing without the use of liquids: Application Rate Minimum Sample Size 125 lb./yd.2 8 by 8 in. 150 lb./yd.2 7 by 7 in. 200 lb./yd.2 6 by 6 in. 300 lb./yd.2 5 by 5 in. No. Tests Table II-15. Process Tolerance for Eight Tests (Plus and Minus Tolerance), Section Process Tolerance on Each Laboratory Sieve and Asphalt Content - Percent Plus & Minus Top Size 1.5 in 1 in 3/4 in 1/2 in 3/8 in No. 4 No. 8 No. 30 No. 50 No. 200 AC* *Asphalt content will be measured as extractable asphalt or mass after ignition Source: VDOT Road and Bridge Specifications, Section Figure Process Tolerances Chart VDOT and Platinum Performance Partners, LLC Chapter 8 page 29

198 Duties of thetechnicians Chapter Eight Knowledge Check 1. Who is responsible for the submission of the job mix formula? A. Plant Inspector B. Asphalt Plant Contractor/Technician C. District Materials Engineer D. District Materials Asphalt Concrete Technician 2. Who approves the job mix formula? A. Plant Inspector B. Asphalt Mix Design Contractor/Technician C. District Materials Engineer D. None of the above 3. Whose responsibility is it to assure that all materials are properly handled and stored? A. Asphalt Mix Design Contractor/Technician B. Plant Inspector C. District Materials Engineer D. District Materials Aggregate Technician 4. Asphalt cement (binder) used for state work does not need to be certified or tested. A. True B. False 5. Whose responsibility is it to sample, make proportioning determinations and make all adjustments necessary to insure proper operational control? A. Plant Inspector B. Contractor s Asphalt Mix Design Technician C. District Materials Engineer s representative D. None of the above 6. A chart that alerts the Producer when to investigate his/her process is known as the: A. Process tolerance chart B. Control chart C. Standard deviation chart D. Reference chart 7. Samples taken from equal portions of a lot at locations which have been selected solely by chance are known as: A. Random samples B. Representative samples C. Stratified random samples D. Progress samples page 30 Chapter 8 VDOT and Platinum Performance Partners, LLC

199 Duties of thetechnicians 8. A method to reevaluate asphalt concrete when there is doubt that the original test results are valid, is known as the: A. Acceptance range B. Referee system C. Bell system D. Process tolerance 9. Where should monitor samples be taken? A. On the road B. At the plant 10. Monitor samples are taken by the Producer s Certified Asphalt Plant Technician in the presence of the District Monitor. A. True B. False 11. What is the maximum time required after production starts before taking the first sample? 12. What procedure should be used when two samples are randomly selected to be taken from one truckload of material? 13. How should the sample be taken from the truck? 14. What is the normal size of a lot? 15. What is the difference between random sampling and representative sampling? 16. In stratified random sampling, what would be the number of samples required per 4000 ton lot? VDOT and Platinum Performance Partners, LLC Chapter 8 page 31

200 Duties of thetechnicians This page intentional left blank page 32 Chapter 8 VDOT and Platinum Performance Partners, LLC

201 MCS: Asphalt Plant Certification 9 Testing of Asphalt Concrete Mixtures This chapter of the guide covers the methods used to determine asphalt concrete properties by laboratory testing. In a hot mix asphalt (HMA) paving mixture, asphalt and aggregate are blended together in precise proportions. The relative proportions of these materials determine the physical properties of the mix, and ultimately, how the mix will perform as a finished pavement. The Department (VDOT) establishes the mix design requirements. Once these are established, it is the responsibility of the Contractor/Producer and his Technician to develop the mix within the framework of the specifications. Learning Objectives: Upon completion of this chapter, you should be able to: Identify the laboratory tests used to determine asphalt characteristics Define VTM, VMA, VFA, and the F/A ratio, and describe how each is calculated Describe how to perform the Bulk Specific Gravity and Maximum Specific Gravity procedures Perform volumetric calculations VDOT and Platinum Performance Partners, LLC Chapter 9 page 1

202 Testing of Asphalt Concrete Mixtures Overview DEFINITIONS. The following terms will be used throughout this section: Percent Binder (P b ) Specific Gravity Voids in the Total Mixture (VTM) Voids Filled with Asphalt (VFA) Voids in the Mineral Aggregate (VMA) Fines to Asphalt Ratio (F/A) Tensile Strength Ratio (TSR) The percent of asphalt binder in the mix by mass (as a percent of the total mix mass). A unit-less ratio of a material s density relative to water when both are at the same temperature (i.e., if we say a material has a specific gravity of 2, then it has twice the mass of water for a given volume). The part of the compacted mixture not occupied by aggregate or asphalt, expressed as a percentage of the total volume. VTM is synonymous with air voids. The percentage of voids in the compacted aggregate mass that are filled with asphalt cement; also known as the Asphalt Void Ratio. The air void spaces that exist between the aggregate particles in a compacted paving mixture, including spaces filled with asphalt. Indicates the film thickness of coated particles. Measures the strength loss resulting from damage caused by stripping under laboratory-controlled accelerated freeze-thaw conditioning. Through many years of laboratory testing and actual road application, VDOT has established design ranges based on the Superpave Mix Design system for asphalt concrete mixtures used in Virginia. When a sample of HMA is tested in the laboratory, it can be analyzed to determine its probable performance in the pavement structure, as well as its conformance to VDOT specifications. The laboratory tests used to ensure that asphalt concrete mixtures meet specifications, and what they physically determine, are indicated in the table that follows. All of the tests listed in the table will be addressed in this chapter, with the exception of Sieve Analysis (which was covered in Chapter 6). Only after the physical characteristics have been determined using these tests can we complete volumetric calculations. Note: Throughout this section, in the text and particularly in the volumetric equations, we will refer to the Asphalt Content as the Percent Binder (P b ). page 2 Chapter 9 VDOT and Platinum Performance Partners, LLC

203 Testing of Asphalt Concrete Mixtures Use This Laboratory Test Ignition Method Specific Gravity Maximum Specific Gravity (Rice, MSG, or Gmm) Bulk Specific Gravity of Mixture (Gmb) Sieve Analysis Tensile Strength Ratio (TSR) To Determine the Physical Characteristic The Percent Binder (P b ) in the mix The ratio of a material s density relative to water A mixture s specific gravity in a void-less condition, which would be the max achievable specific gravity for that mix The volume of voids in the mix of a compacted specimen. Note: G mm must be greater than G mb for a given mix. Particle size distribution of aggregates in asphalt Stripping potential Other tests that may be performed in the lab include the Boil Test, Moisture Content Test, Particle Coating Test, and Aggregate Consensus Properties Test. Of these, the Boil Test is covered in this chapter. The Moisture Content test was previously covered in Chapter 3 of this guide. Figure 9-1 illustrates design ranges and Figure 9-2 provides recommended performance grades for the asphalt concrete mixtures used in Virginia (Road and Bridge Specifications, Section 211, Table II-14 and II-14A). Table II-14. Mix Design Criteria VTM (%) Production VFA (%) VFA (%) Production Min. VMA Fines/Asph alt Ratio No. of Gyrations Mix Type (Note 1) Design (Note 2) (%) (Note 3) N Design SM-9.0 A Notes 1,2, SM-9.0 D Notes 1,2, SM-9.0 E Notes 1,2, SM-9.5 A Notes 1,2, SM-9.5 D Notes 1,2, SM-9.5 E Notes 1,2, SM-12.5 A Notes 1,2, SM-12.5 D Notes 1,2, SM-12.5 E Notes 1,2, IM-19.0 A Notes 1,2, IM-19.0 D Notes 1,2, IM-19.0 E Notes 1,2, BM-25.0 A Notes 2, 3, BM-25.0 D Notes 2, 3, SM = Surface Mix; IM = Intermediate Mixture; BM = Base Mixture Note 1: Note 2: Note 3: Note 4: Asphalt content should be selected at 4.0 % Air Voids. During production of an approved job mix, the VFA shall be controlled within these limits. Fines-Asphalt Ratio is based on effective asphalt content. Base mix shall be designed at 2.5 percent air voids. BM-25.0 A shall have a minimum asphalt content of 4.4 percent, unless otherwise approved by the Engineer. BM-25.0 D shall have a minimum asphalt content of 4.6 percent, unless otherwise approved by the Engineer. Figure 9-1. Mix Design Criteria for Mix Types for Asphalt Concrete Mixtures VDOT and Platinum Performance Partners, LLC Chapter 9 page 3

204 Testing of Asphalt Concrete Mixtures Table II-14A. Recommended Performance Grade of Asphalt Cement Percentage of Reclaimed Asphalt Pavement (RAP) in Mix Mix Type % RAP % < % RAP 30% 25.0% < %RAP 35% SM-9.0A, SM-9.5A, SM-12.5A PG PG SM-9.0D, SM-9.5D, SM-12.5D PG PG IM-19.0A PG PG IM-19.0D PG PG BM-25.0A PG PG BM-25.0D PG PG Figure 9-2. Recommended Performance Grades of Asphalt Cement page 4 Chapter 9 VDOT and Platinum Performance Partners, LLC

205 Physical Characteristics to be Determined by Testing Testing of Asphalt Concrete Mixtures This section highlights basic terms and concepts that are critical to understanding the physical characteristics that will be determined by testing and why they are important. DEFINITIONS. The following terms will be used throughout this section: Total asphalt content Effective asphalt content Absorptiveness The amount of asphalt binder that must be added to the mixture to produce the desired mix qualities. The amount of asphalt binder not absorbed by the aggregate. The ability of the aggregate used in the mix to absorb asphalt binder. Asphalt Binder Content The proportion of asphalt binder in the mixture is critical and must be accurately determined in the laboratory and precisely controlled on the job. The optimum asphalt binder content of a mix is highly dependent on aggregate characteristics such as gradation and absorptiveness. The finer the mix gradation, the larger the total surface area of the aggregate; therefore, the greater the amount of binder required, as illustrated by the table below. Asphalt Binder Content Aggregate Gradation Aggregate Absorptiveness High Fine High Low Coarse Low Effective asphalt binder content Effective asphalt binder content is the amount of binder not absorbed by the aggregate. In other words, it is the amount of asphalt that effectively forms a bonding film on the aggregate surfaces. Effective asphalt binder content is calculated by subtracting the amount of absorbed binder from the total binder content. This may be expressed as A percent by mass, the Percent Binder Effective (P be ) A percent by volume, the Volume Binder Effective (V be ). The absorptiveness of an aggregate is obviously an important consideration in determining the asphalt binder content of a mixture. This characteristic is generally known for established aggregate sources, but requires careful testing when new aggregate sources are used. VDOT and Platinum Performance Partners, LLC Chapter 9 page 5

206 Testing of Asphalt Concrete Mixtures AWARENESS/IMPORTANT Variations in binder content will cause changes in mix properties, from dry to wet. If a mix contains too little or too much mineral filler, arbitrary adjustments to correct the situation are likely to worsen it. Instead, proper sampling and testing should be done to determine the cause of the variations and, if necessary to establish a new job mix design. Highlights a step in the procedure which is either unusual or very particular to this procedure. May also indicate awareness (additional information) or a cautionary concern in the procedure. Absorptiveness The absorptiveness (ability to absorb asphalt) of the aggregate used in the mix is critical in determining optimum asphalt content. Enough asphalt must be added to the mix to allow for absorption and still coat the particles with an adequate film. When discussing absorbed and unabsorbed asphalt, technologists talk about the following two types of asphalt content: Total asphalt content the amount of asphalt binder that must be added to the mixture to produce the desired mix qualities Effective asphalt content the amount of asphalt binder not absorbed by the aggregate. Aggregate Gradation Aggregate gradation is directly related to optimum asphalt binder content. The finer the mix gradation, the larger the total surface area of the aggregate and the greater the amount of binder required to uniformly coat the particles. Conversely, because coarser mixes have less total aggregate surface area, they demand less binder. The relationship between aggregate surface area and optimum binder content is most pronounced where filler material is involved (i.e., very fine aggregate fractions which pass through the No. 200 (0.075 mm) sieve). Testing is important because small increases in the amount of filler in a gradation can absorb much of the asphalt binder, resulting in a dry, unstable mix. Small decreases have the opposite effect too little filler results in too rich (wet) a mixture. Voids in the Total Mixture (VTM) Air voids are small airspaces or pockets of air that occur between the coated aggregate particles in the final compacted mix. A certain percentage of air voids is necessary in all dense-graded highway mixes to allow for some additional pavement compaction under traffic and to provide spaces into which small amounts of binder can flow during this subsequent compaction. AWARENESS/IMPORTANT The allowable percentage of air voids (in laboratory specimens) is between 2.0% and 5.0% for most VDOT mixes. Job specifications require pavement that allows as low an air void content as is practical, approximately 8.0%. Highlights a step in the procedure which is either unusual or very particular to this procedure. May also indicate awareness (additional information) or a cautionary concern in the procedure. page 6 Chapter 9 VDOT and Platinum Performance Partners, LLC

207 Testing of Asphalt Concrete Mixtures The durability of an asphalt pavement is a function of the air void content. This is because the lower the air voids, the less permeable the mixture becomes. Too high an air void content provides passageways through the mix for the entrance of damaging air and water. A low air void content, on the other hand, can lead to flushing, a condition in which excess asphalt squeezes out of the mix to the surface. Density and void content are directly related. The higher the density, the lower the percentage of voids in the mix, and vice versa. Voids Total Mixture (VTM) is the part of the compacted mixture not occupied by aggregate or asphalt, expressed as a percentage of the total volume. It is synonymous with air voids and is the complement of the percent density when based upon the Maximum Specific Gravity (Gmm). The VTM obtained in the Superpave mix design gives an indication of whether the mix can be compacted adequately in the field. AWARENESS/IMPORTANT The VTM is probably the number one criterion for predicting field compaction and, ultimately, pavement life. Highlights a step in the procedure which is either unusual or very particular to this procedure. May also indicate awareness (additional information) or a cautionary concern in the procedure. Voids in the Mineral Aggregate (VMA) Voids in the Mineral Aggregate (VMA) are the air void spaces that exist between the aggregate particles in a compacted paving mixture, including spaces filled with asphalt. VMA represents the space that is available to accommodate the asphalt and the volume of air voids necessary in the mixture, as shown in Figure 9-3. The more VMA in the dry aggregate, the more space is available for the film of asphalt. Figure 9-3. VMA in a Compacted Mix Specimen The thicker the asphalt film on the aggregate particles, the more durable the mix. Specific minimum requirements for VMA are specified in Section of the Road and Bridge Specifications. AWARENESS/IMPORTANT Minimum VMA values must be adhered to so that a durable asphalt film thickness can be achieved. Highlights a step in the procedure which is either unusual or very particular to this procedure. May also indicate awareness (additional information) or a cautionary concern in the procedure. VDOT and Platinum Performance Partners, LLC Chapter 9 page 7

208 Testing of Asphalt Concrete Mixtures AWARENESS/IMPORTANT Increasing the density of gradation of the aggregate to a point where below-minimum VMA values are obtained leads to thin films of asphalt and a dry looking, low durability mix. Therefore, economizing in asphalt content by lowering VMA is actually counterproductive and detrimental to pavement quality. Highlights a step in the procedure which is either unusual or very particular to this procedure. May also indicate awareness (additional information) or a cautionary concern in the procedure. Voids Filled with Asphalt (VFA) VFA is the percentage of voids in the compacted aggregate mass (VMA) that are filled with asphalt cement. It is synonymous with the Asphalt Void Ratio. The VFA property is important not only as a measure of relative durability, but also because there is an excellent correlation between it and percent density. If the VFA is too low, there is not enough asphalt to provide durability and the mix will be prone to fatigue. If the VFA is too high, then the available VMA has been overfilled with asphalt and the mix will be prone to over-densification under traffic and will lose stability. Thus, the VFA is a very important design property. Fines to Asphalt Ratio (F/A) The Fines to Asphalt Ratio (F/A) is an indication of the film thickness of coated particles. The film thickness helps reduce premature aging and moisture damage. Tensile Strength Ratio (TSR) This test measures the strength loss resulting from damage caused by stripping under laboratory controlled accelerated freeze-thaw conditioning. The results may be used to predict long-term susceptibility to stripping of an asphalt concrete. To combat the effects of water damage, an antistripping additive is used in all asphalt mixes. One of these additives is hydrated lime. The Contractor may use either 1.0% hydrated lime in accordance with Section (i) of the Road and Bridge Specifications or an approved chemical anti-strip additive at the manufacturer s recommended dosage. Approved chemical anti-strip additives are listed on the Department s approved list found in the Materials Division s Manual of Instructions. A combination of both hydrated lime and chemical anti-strip may be used to meet the TSR requirements. The TSR value is determined in accordance with AASHTO T- 283 (including a freeze-thaw cycle). The TSR test is covered in detail in the Asphalt Plant Mix Design class. AWARENESS/IMPORTANT For production tests, the mixture shall produce a tensile strength ratio (TSR) value not less than 0.80 for Superpave mixes. Highlights a step in the procedure which is either unusual or very particular to this procedure. May also indicate awareness (additional information) or a cautionary concern in the procedure. page 8 Chapter 9 VDOT and Platinum Performance Partners, LLC

209 Testing of Asphalt Concrete Mixtures Testing Procedures SAFETY WARNING These standards and test methods may involve hazardous materials, operations and equipment. This standard does not purport to address all of the safety problems associated with its use. It is the responsibility of whoever uses this standard to consult and establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. Describes a condition where personal safety may be at risk. This is used to alert personnel to operating procedures & practices which, if not observed, may result in personal injury. When a plant has produced a mixture, the mixture must be tested to ensure that it meets VDOT specifications. In addition, the Contractor s payment for the mixture produced will be based on the asphalt content and aggregate gradation determined by testing. The following will provide the necessary information for laboratory testing of plant produced mixtures (as described in Chapter 10). Procedure for Determining Asphalt Content (Percent Binder) (VTM-102) The Ignition Method The Virginia Test Method (VTM) for determining the asphalt binder content in asphalt mixtures is the Ignition Method, VTM-102. This test method uses an ignition oven to burn off the asphalt binder in the mixture, leaving the aggregate behind. The binder content of the mix will be used to determine the VMA and the F/A ratio of the mixture. When preparing a sample for testing by the Ignition Method, the quartering method, as specified in AASHTO T-248, may be used. The complete VTM-102 is in Appendix C of this manual. Procedure for Compacting Specimen (AASHTO T-312) The purpose of compacting specimens is to prepare them for the Bulk Specific Gravity (G mb ) test, which will ultimately be used to determine the air voids of the mixture. TOOLS AND EQUIPMENT Primary equipment used for this test includes the gyratory compactor, specimen molds, filter paper, thermometers, pans for each specimen and a scoop. Describes what tools, equipment and tests are required to complete the job safely and with the highest level of quality. VDOT and Platinum Performance Partners, LLC Chapter 9 page 9

210 Testing of Asphalt Concrete Mixtures How to Mold Specimens To prepare and compact (i.e., mold) three test specimens for use in the Bulk Specific Gravity test, complete the steps that follow. STEP 1. Turn the gyratory compactor on and let it warm-up. a. Once the gyratory compactor has cycled through the warm-up period, make sure it has the correct settings (e.g., the number of gyrations, ram pressure). b. The gyrations used for compacting specimens are found in Section Table II-14. STEP 2. Heat the molds to the desired compaction temperature as specified in Section (d) 6. STEP 3. Place the mixture in an oven set at the desired compaction temperature. Place a thermometer into the mixture so its temperature can be monitored. STEP 4. Once the material has become workable, weigh out the desired amount of material for each of the three specimens. STEP 5. Using a flat bottom scoop, place each specimen in a small pan with a thermometer in each of the pans to monitor temperature. STEP 6. Heat each specimen to compaction temperature. STEP 7. After the mixture has reached the compaction temperature, place a heated mold on a table and insert a piece of filter paper into the bottom of the mold. STEP 8. Place the material into the mold in one lift, as shown in Figure 9-4. Place a piece of filter paper onto the top of the material. If needed, place the top plate into the mold. STEP 9. Place the mold into the gyratory compactor and press the start button. STEP 10. Once compaction is complete, check to make sure the specimen height is 115 ± 5 mm. Figure 9-4. Insert Material into the Mold page 10 Chapter 9 VDOT and Platinum Performance Partners, LLC

211 Testing of Asphalt Concrete Mixtures STEP 11. Remove the mold from the gyratory compactor, as shown in Figure 9-5. Extract the specimen and remove the filter paper from the top and bottom of the specimen. STEP 12. Place the specimen on a smooth, flat surface and allow to cool to room temperature, as shown in Figure 9-6. Repeat these steps as necessary for compacting additional specimens. Once the specimens have cooled, determine the Bulk Specific Gravity of the specimens using the procedure detailed on the next page. Figure 9-5. Remove Mold from Gyrator Figure 9-6. Place Specimen on Smooth, Flat Surface to Cool, then Number Specimen VDOT and Platinum Performance Partners, LLC Chapter 9 page 11

212 Testing of Asphalt Concrete Mixtures Procedure for Determining Bulk Specific Gravity (AASHTO T-166) TOOLS AND EQUIPMENT Primary equipment used for this procedure includes a scale for weighing the core and water. Describes what tools, equipment and tests are required to complete the job safely and with the highest level of quality. How to Determine Bulk Specific Gravity To determine the Bulk Specific Gravity of the compacted cores in accordance with AASHTO T-166 Method A, complete the steps that follow. STEP 1. Dry the specimen to a constant mass. (Note: this step is typically intended for field compacted specimens that may have been exposed to moisture). Constant mass shall be defined as the mass at which further drying at 125 ± 5 F (52 ± 3 C) does not alter the mass by more than 0.05%. Samples saturated with water shall initially be dried overnight at 125 ± 5 F (52 ± 3 C) and then weighed at two-hour drying intervals. Recently-molded laboratory samples which have not been exposed to moisture do not require drying. STEP 2. Cool the specimen to room temperature at 77 ± 9 F (25 ± 5 C). STEP 3. Weigh the core in the air, and record the mass (A). STEP 4. Immerse each specimen in water at 77 ± 3 F (25 ± 1 C) for 4 ± 1 minutes and record the immersed mass (C). STEP 5. Remove the specimen from the water and quickly damp dry the specimen by blotting with a damp towel, as shown in Figure 9-7. STEP 6. Weigh to determine the saturated - surface dry mass (SSD), and record the mass (B). Note: Any water that seeps from the specimen during the weighing operation is considered part of the saturated specimen. Figure 9-7. Blot with Damp Towel page 12 Chapter 9 VDOT and Platinum Performance Partners, LLC

213 Testing of Asphalt Concrete Mixtures STEP 7. Calculate the Bulk Specific Gravity of each specimen using the following equation: Bulk Speci ic Gravity ( ) = Where: A = Mass of Core in Air B = Saturated - Surface Dry Mass of Core in Air C = Mass of Core in Water STEP 8. Calculate the average Bulk Specific Gravity of the mix (Gmb) using the following equation: Average G mb = G mb Speciman 1 + G mb Speciman 2 + G mb Speciman 3 3 The average Gmb will be used to determine air voids (VTM) of the mixture. VDOT and Platinum Performance Partners, LLC Chapter 9 page 13

214 Testing of Asphalt Concrete Mixtures Procedure for Determining Maximum Specific Gravity (AASHTO T-209) TOOLS AND EQUIPMENT Primary equipment used for this procedure includes a Rice bucket, scale, and vacuum. Describes what tools, equipment and tests are required to complete the job safely and with the highest level of quality. The Maximum Specific Gravity (Gmm or Rice) is determined by AASHTO T-209 (Rice Method), in which vacuuming is used to extract all of the air from the mixture. This represents 100% density (no air voids) for a particular asphalt mixture. This value is used in conjunction with the Bulk Specific Gravity to determine the relative density and VTM of the compacted specimens for that mixture. How to Determine Maximum Specific Gravity (Gmm) Complete the steps that follow to determine the Maximum Specific Gravity. STEP 1. After quartering or splitting a mixture to obtain the sample mass needed for the particular mixture, spread the mix out on a table to cool, as shown in Figure 9-8. Be sure to separate the mix particles so that there are no particles larger than 1/4 inch. STEP 2. Weigh the Rice bucket in air and record the mass (A). STEP 3. Place the sample in the Rice bucket, as shown in Figure 9-9. STEP 4. Weigh the sample and the bucket together in air and record the mass (C). Figure 9-8. Spread the Mix Out to Cool STEP 5. Add water to the sample in the bucket until the sample is completely covered with water. a. The temperature of the water must be 77 F (25 C). b. If the temperature is not 77 F, the temperature correction factor must be used. Figure 9-9. Place Sample in the Bucket page 14 Chapter 9 VDOT and Platinum Performance Partners, LLC

215 Testing of Asphalt Concrete Mixtures STEP 6. Place the top on the Rice bucket and pull the vacuum to ± 2.25 mm HG, as Figure 9-10 illustrates, to remove the air voids in the mix. STEP 7. Maintain the vacuum for 15 ± 2 minutes, shaking the bucket at 2-minute intervals, or place the bucket on a slow continuous shaker. STEP 8. After 15 ± 2 minutes, release the vacuum, remove the top, and place the bucket suspended in the bath for 10 ± 1 minutes, as shown in Figure The water in this bath must also be 77 F (25 C) STEP 9. After 10 ± 1 minute, record the mass of the sample and bucket in water (D). Figure Place Bucket in Vacuum STEP 10. After recording this mass, gently pour water from bucket back into water bath and dispose of sample in bucket (you will no longer need the sample). STEP 11. Then place the empty bucket back into the water bath, leaving it immersed for 10 ± 1 minutes. STEP 12. Record the mass of the empty bucket in water (B). STEP 13. Calculate the Maximum Specific Gravity (Gmm) using the following equation: Figure Place the Bucket in a Water Bath = ( ) ( ) ( ). Where: A = Mass of Container in air B = Mass of Container in water C = Mass of Container and Sample in air D = Mass of Container and Sample in water VDOT and Platinum Performance Partners, LLC Chapter 9 page 15

216 Testing of Asphalt Concrete Mixtures Procedure for Determining Tensile Strength Ratio (AASHTO T 283) The test is performed by compacting specimens to an air void level of 6% to 8%. Three specimens are selected as a control and tested without moisture conditioning. Three more specimens are selected to be conditioned by saturating with water, undergoing a freeze cycle, and subsequently having a warmwater soaking cycle. The specimens are then tested for indirect tensile strength by loading the specimens at a constant rate and measuring the force required to break the specimen. The tensile strength of the conditioned specimens is compared to the control specimens to determine the tensile strength ratio (TSR). This test may also be performed on cores taken from the finished pavement. Procedure for Conducting the Boil Test (VTM-13) TOOLS AND EQUIPMENT Primary equipment used for this procedure includes a burner, flask and paper towel. Describes what tools, equipment and tests are required to complete the job safely and with the highest level of quality. In the Boil Test, asphalt mixtures are subjected to the action of boiling water for a specified period of time, to determine the effectiveness of an anti-stripping additive when it has been used in asphalt mixtures. The Boil Test is performed in accordance with VTM-13. The results are reported as Pass or Fail. How to Conduct the Boil Test To perform the Boil Test, complete the steps that follow. STEP 1. Allow the sample of asphalt mixture to cool to 230 ± 9 F (110 ± 5 C). STEP 2. Sieve approximately 800 grams of material over the 1/2 inch (12.5 mm) sieve, then sample 400 grams of the remaining material for the test. Note: Remove plus 1/2 inch (12.5 mm) material from mixture prior to attaining specified temperature. STEP 3. Place approximately 200 grams on a paper towel before boiling. Place the remainder (approximately 200 grams) of the mixture in boiling water and continue boiling for 10 minutes, as shown in Figure Figure Place the Mixture in Boiling Water page 16 Chapter 9 VDOT and Platinum Performance Partners, LLC

217 Testing of Asphalt Concrete Mixtures STEP 4. Drain the water from the mixture and place the sample on a paper towel, as shown in Figure Allow to cool at room temperature overnight. STEP 5. The next morning, compare the boiled and not boiled portions on the paper towels, as shown in Figure a. If the boiled portion shows more signs of stripping than the not boiled portion, the test fails. b. The producer will then take a second sample and test using the same steps as before. If the second sample fails, production shall be halted until corrective action is taken to the satisfaction of the Engineer. c. On the resumption of production, samples will be taken immediately and tested using the same steps as described above. STEP 6. Report as passing or failing. Figure Place the Mixture on a Paper Towel Figure Look for Signs of Stripping VDOT and Platinum Performance Partners, LLC Chapter 9 page 17

218 Testing of Asphalt Concrete Mixtures Calculating Volumetric Properties To determine the volumetric properties (VTM, VMA, VFA, F/A) of the mixture, the Bulk Specific Gravity of the mixture (G mb ), Maximum Specific Gravity (G mm ) of the mixture, Asphalt Binder Content, and Aggregate Gradation first must be determined. In addition, the Effective Specific Gravity of the aggregate (G se ) and the Bulk Specific Gravity of the aggregate (G sb ) must be calculated. Definitions used in the formulas and calculations: G mm G mb G se G b G sb P b P be P s CF = Maximum Specific Gravity of Mixture (Rice) = Bulk Specific Gravity of Mixture = Effective Specific Gravity of Aggregate = Binder (Asphalt) Specific Gravity = Bulk Specific Gravity of Aggregate = Percent Binder (Asphalt) Content = Effective Binder (Asphalt) Content = Percent Stone (100 Pb) = Field correction factor supplied with job mix formula Effective Specific Gravity of Aggregate (G se ): = Where: G se = Effective Specific Gravity of aggregate P b = Percent Binder (from Ignition Method) P s = Percent Stone (100 P b from Ignition Method) G mm = Maximum Specific Gravity of mixture (from Rice Method) G b = Binder Specific Gravity (1.030) Bulk Specific Gravity of Aggregate (G sb ): G sb = G se - CF Where: G sb G se CF = Bulk Specific Gravity of aggregate = Effective Specific Gravity of aggregate = Field correction factor supplied with job mix formula Once these properties have been determined, the volumetric properties (VTM, VMA, VFA, and F/A) can be calculated as follows. page 18 Chapter 9 VDOT and Platinum Performance Partners, LLC

219 VTM: Determine the voids in the total mixture (VTM) using the following formula: VTM = G mb G mm Where: G mb G mm Testing of Asphalt Concrete Mixtures = Bulk Specific Gravity of mixture = Maximum Specific Gravity of mixture (from Rice Method) This VTM value will used to determine density and VFA. Relative Density or (% ): The relative density of each test specimen can be determined by the following formula: %G mm = 100 G mb G mm VMA: Determine the voids in the mineral aggregate (VMA) using the following formula: VMA = 100 (G mb P s ) G sb Where: G mb P s G sb = Bulk Specific Gravity of mixture = Percent stone (100 Pb from Ignition Method) = Bulk Specific Gravity of aggregate VFA: Determine the voids filled with asphalt (VFA) using the following formula: VFA = VMA - VTM VMA 100 VDOT and Platinum Performance Partners, LLC Chapter 9 page 19

220 Testing of Asphalt Concrete Mixtures F/A Ratio: Determine the F/A ratio as follows: 1. Determine the percent passing the No. 200 (75 mm) sieve from sieve analysis of mixture. 2. Calculate the Effective Specific Gravity of the aggregate (G se ) and Bulk Specific Gravity of the aggregate (G sb ). 3. Calculate the Percent Binder Effective of the mixture (P be ). P be = P b - (P s G b ) G se - G sb (G se G sb ) Where: P be P b P s 4. Calculate F/A ratio. = Percent Binder Effective = Percent Binder(from Ignition Method) = Percent stone (100 Pb) G b = Binder specific gravity (1.030) G se = Effective Specific Gravity of Aggregate G sb = Bulk Specific Gravity of Aggregate F/A ratio = % passing 200 P page 20 Chapter 9 VDOT and Platinum Performance Partners, LLC

221 Testing of Asphalt Concrete Mixtures Example Volumetric Calculations The example that follows illustrates the proper use of the various volumetric calculations. In the example, the results of laboratory testing are as follows: The percent binder (P b ) of the mixture after performing the Ignition Method is 4.60%. The field correction factor submitted with the job mix formula is The percent passing the No. 200 sieve is 5.0%. Maximum Specific Gravity (G mm ) Procedure Variable Assignment Specimen Mass Mass Bucket in Air (g) =A Mass of Bucket in Water (g) =B Mass of Bucket and Sample in Air (g) =C Mass of Bucket and Sample in Water (g) =D Maximum Specific Gravity (Gmm): G mm = C A (C A) (D B) G mm = G mm = ( ) ( ) = ( ) = VDOT and Platinum Performance Partners, LLC Chapter 9 page 21

222 Testing of Asphalt Concrete Mixtures Bulk Specific Gravity (Gmb) Procedure Variable Assignment Specimen Specimen Specimen #1 Mass #2 Mass #3 Mass Mass of Core in Air (g) =A SSD Mass of Core (g) =B Mass of Core in Water(g) =C Bulk Specific Gravity of Mixture (Gmb): Bulk Specific Gravity (G mb ) of Core = A B C G mb Core = ( ) = G mb Core 2 G mb Core = ( ) = ( ) = = The Average Bulk Specific Gravity of the cores is the Bulk Specific Gravity of the mixture (G mb ): Avg. G mb = G mb Specimen 1 + G mb Specimen 2 + G mb Specimen 3 3 Avg. G mb = = 3 3 = page 22 Chapter 9 VDOT and Platinum Performance Partners, LLC

223 Testing of Asphalt Concrete Mixtures Effective Specific Gravity of Aggregate (Gse): G se = P s 100 G - P b mm G b G se = G se = G se = = Bulk Specific Gravity of Aggregate (G sb ): Gsb = Gse CF Gsb = Gsb = Voids in Total Mix: VTM = VTM = 100 X X 1.. VTM = 100 X ( ) VTM = 100 X = 6.5% VDOT and Platinum Performance Partners, LLC Chapter 9 page 23

224 Testing of Asphalt Concrete Mixtures Voids in Mineral Aggregate: VMA = VMA = VMA = VMA = = 16.2 Voids Filled with Asphalt: VFA = 100 X VMA-VTM VMA VFA = 100 X VFA = 100 X VFA = 100 X = 60 page 24 Chapter 9 VDOT and Platinum Performance Partners, LLC

225 Testing of Asphalt Concrete Mixtures F/A Ratio: F/A Ratio = % passing 200 sieve P be P be = Pb - (P s G b ) G se- G sb G se G sb P be = ( ) x. P be = ( ).. P be = (98.262) (0.003) P be = P be = 4.31 F/A Ratio = % passing 200 sieve P be F/A Ratio = F/A Ratio = 1.2 VDOT and Platinum Performance Partners, LLC Chapter 9 page 25

226 Testing of Asphalt Concrete Mixtures Volumetric Properties Worksheets and Formulas The following section contains reference materials (worksheets and formulas) to assist you in making required volumetric calculations. Note that all measurements in this section are in grams (g). Volumetric Worksheets The following worksheets are presented in this section: Worksheet for Determining the Maximum Specific Gravity of the Mixture Worksheet for Determining the Bulk Specific Gravity of the Mixture Worksheet for Determining the Percent Voids in the Total Mixture Worksheet for Determining the Effective Gravity of the Aggregate Worksheet for Determining the Bulk Specific Gravity of the Aggregate Worksheet for Determining the Voids in the Mineral Aggregate Worksheet for Determining the Voids Filled with Asphalt Worksheet for Calculating the F/A Ratio page 26 Chapter 9 VDOT and Platinum Performance Partners, LLC

227 Worksheet for Determining the Maximum Specific Gravity of the Mixture (Gmm) Testing of Asphalt Concrete Mixtures Maximum Specific Gravity of the Mixture = ( ) ( ) Variable Assignment Specimen Mass Mass of the Container in Air =A Mass of the Container in Water =B Mass of the Container & Sample in Air =C Mass of the Container & Sample in Water =D Gmm = ( ) ( ) ( ) Gmm = ( ) Gmm = Gmm = VDOT and Platinum Performance Partners, LLC Chapter 9 page 27

228 Testing of Asphalt Concrete Mixtures Worksheet for Determining the Bulk Specific Gravity of the Mixture (G mb ) Bulk Specific Gravity of the Mixture = ( ) Variable Assignment Specimen #1 Mass Specimen #2 Mass Specimen #2 Mass Mass of Core in Air =A SSD Mass of Core in Air =B Mass of Core in Water =C Specimen #1 Specimen #2 G mb = G mb = ( ) ( ) G mb = G mb = G mb = G mb = Specimen #3 G mb = ( ) G mb = G mb = page 28 Chapter 9 VDOT and Platinum Performance Partners, LLC

229 Testing of Asphalt Concrete Mixtures Calculate Average Bulk Specific Gravity (Avg. Gmb) Avg. G mb = Avg. G mb = G mb Specimen 1 + G mb Specimen 2 + G mb Specimen Avg. G mb = 3 Avg. G mb = VDOT and Platinum Performance Partners, LLC Chapter 9 page 29

230 Testing of Asphalt Concrete Mixtures Worksheet for Determining the Percent Voids in the Total Mixture (VTM) Variable Assignment Specimen Mass Avg. Gmb (Average Bulk Sp. Gr. of the Mix) =2.427 Gmm (Maximum Sp. Gr. of the Mix) =2.528 VTM = Avg. G mb G mm VTM = 100 X 1 VTM = 100 X 1 ( ) VTM = 100 X ( ) VTM = page 30 Chapter 9 VDOT and Platinum Performance Partners, LLC

231 Worksheet for Determining the Effective Specific Gravity of the Aggregate (Gse) Testing of Asphalt Concrete Mixtures G se = P s 100 G mm - P b G b Where Equals P b 5.65% G mm G b P s 100 Pb G se 100 G Se = ( ) G SE = G SE = VDOT and Platinum Performance Partners, LLC Chapter 9 page 31

232 Testing of Asphalt Concrete Mixtures Worksheet for Determining the Bulk Specific Gravity of the Aggregate (Gsb) G sb = G se - CF (field correction factor from job mix formula) Where Equals CF G se Gsb = G sb = page 32 Chapter 9 VDOT and Platinum Performance Partners, LLC

233 Worksheet for Determining the Voids in the Mineral Aggregate (VMA) Testing of Asphalt Concrete Mixtures VMA uses the Average G mb (Bulk Specific Gravity of Mixture) for the three test specimens. VMA = 100 (Avg. G mb P s ) G sb Where Equals Avg. G mb (Average Bulk Sp. Gr. of Mix) G sb (Bulk Sp. Gr. of the Agg.) P s (Percent Stone) VMA = ( ) VMA = VMA = VMA = VDOT and Platinum Performance Partners, LLC Chapter 9 page 33

234 Testing of Asphalt Concrete Mixtures Worksheet for Determining the Voids Filled with Asphalt (VFA) VFA uses the average VTM for the three specimens. VFA = VMA - VTM VMA 100 Where Equals VMA 16.5% VTM 4.0% VFA = ( ) X 100 VFA = X 100 VFA = X 100 VFA = page 34 Chapter 9 VDOT and Platinum Performance Partners, LLC

235 Testing of Asphalt Concrete Mixtures Worksheet for Calculating the F/A Ratio: 1. Determine the % passing the No. 200 sieve from sieve analysis of the mixture. F/A Ratio = % passing No. 200 sieve P be 2. Calculate the P be (Percent Binder Effective) of the mixture. P be = P b - (P s G b ) G se - G sb (G se G sb ) Where Equals P b = Percent Binder Content from Ignition Method 5.65% P s = Percent Stone (100 P b ) G b = Binder (asphalt) Specific Gravity G se = Effective Specific Gravity of Aggregate G sb = Bulk Specific Gravity of Aggregate P be = ( ) ( ) ( ) P be = ( ) ( ) ( ) P be = ( ) ( ) P be = P be = VDOT and Platinum Performance Partners, LLC Chapter 9 page 35

236 Testing of Asphalt Concrete Mixtures F/A Ratio = % passing No. 200 sieve P be Where Equals % passing the No. 200 sieve 5.9% P be 5.36% F/A Ratio = F/A Ratio = page 36 Chapter 9 VDOT and Platinum Performance Partners, LLC

237 Testing of Asphalt Concrete Mixtures Volumetric Properties Formulas Use these formulas in calculating volumetric properties for asphalt. Definitions used in formulas: G mm G mb G se G b G sb P b P be P s = Maximum Specific Gravity of Mixture (Rice) = Bulk Specific Gravity of Mixture = Effective Specific Gravity of Aggregate = Binder (Asphalt) Specific Gravity = Bulk Specific Gravity of Aggregate = Percent Binder (Asphalt) Content = Effective Binder (Asphalt) Content = Percent Stone (100 Pb) Maximum Specific Gravity (G mm ) A = Mass of Bucket in Air B = Mass of Bucket in Water C = Mass of Bucket and Sample in Air D = Mass of Bucket and Sample in Water = ( ) ( ) ( ). Bulk Specific Gravity of Core (G mb ) A = Mass of Core in Air B = SSD Mass of Core in Air C = Mass of Core in Water = ( ) Average Bulk Specific Gravity of Cores (Avg. G mb ) = Sum of G mb Cores / Number of Cores Average G mb = G mb Speciman 1 + G mb Speciman 2 + G mb Speciman 3 3 VDOT and Platinum Performance Partners, LLC Chapter 9 page 37

238 Testing of Asphalt Concrete Mixtures VTM (% Voids in Total Mix) VTM = G mb G mm Avg. VTM = Avg. G mb G mm Relative Density or (%G mm ): %G mm =100* G mb G mm Average %G mm =100* Average G mb G mm Effective Specific Gravity of Aggregate (G se ) G se = P S 100 Gmm - P b G b Bulk Specific Gravity of Aggregate (G sb ) G sb = G se - CF VMA (% Voids in the Mineral Aggregate) VMA = 100 (Avg. G mb P s ) G sb VFA (% Voids Filled with Asphalt) VFA = VMA - VTM VMA 100 page 38 Chapter 9 VDOT and Platinum Performance Partners, LLC

239 Testing of Asphalt Concrete Mixtures F/A Ratio (Fines to Effective Asphalt Ratio) P be = P b - (P s G b ) G se - G sb (G se G sb ) F/A Ratio = % passing #200 sieve P be VDOT and Platinum Performance Partners, LLC Chapter 9 page 39

240 Testing of Asphalt Concrete Mixtures Chapter Nine Knowledge Check 1. The Ignition Method test utilizes a sample of Asphalt Concrete taken from the truck. A. True B. False 2. The Ignition Oven is the method used to determine the Percent Binder or Asphalt Content in asphalt mixtures. A. True B. False 3. The Virginia test method for determining the Percent Binder or Asphalt Content in asphalt mixtures is the centrifuge method. A. True B. False 4. The actual test sample of an asphalt mixture used in the Ignition Oven shall be a minimum of 1500 grams for an SM-12.5A mix. A. True B. False 5. What is the purpose of the Ignition Method? 6. Specifications allow what percent voids in the total mix for an SM-12.5A? 7. VFA are voids in a filler aggregate in asphalt mixtures. A. True B. False 8. VMA are voids in a mineral aggregate. A. True B. False 9. Asphalt test procedures can be found in the appropriate AASHTO procedure or Virginia Test Method (VTM). A. True B. False 10. is added to asphalt as an anti-stripping agent. 11. The Test checks the effectiveness of an anti-stripping additive. page 40 Chapter 9 VDOT and Platinum Performance Partners, LLC

241 Testing of Asphalt Concrete Mixtures Practice Problem 1: Volumetric Calculations The results of laboratory testing of a SM-9.5A yielded the following results: Percent Binder= 5.05 Correction Factor =.017 Asphalt Binder Specific Gravity = Percent minus 200 = Complete the following tables. Maximum Specific Gravity of Mix (G mm ): Variable Assignment Grams Mass Container in Air =A Mass Container in Water =B Mass Container and Sample in Air =C Mass Container and Sample in Water =D Maximum Specific Gravity (G mm ) = Bulk Specific Gravity of Mix (G mb ): Variable Assignment Specimen 1 Specimen 2 Specimen3 Mass of Specimen in Air =A SSD Mass of Specimen =B Mass of Specimen in Water =C Specimen Bulk Specific Gravity Average G mb = 2A. Calculate the Effective Specific Gravity of the Aggregate (G se ) = VDOT and Platinum Performance Partners, LLC Chapter 9 page 41

242 Testing of Asphalt Concrete Mixtures 2B. Calculate the Bulk Specific Gravity of the Aggregate (G sb ) = 3. Calculate the VTM, VMA, VFA and F/A ratio for this mix. 4. Do all the volumetric properties meet the mix design criteria for this mix during production? Design Range Criteria VTM Specification Criteria Calculated Results Meet Spec.? VMA VFA F/A page 42 Chapter 9 VDOT and Platinum Performance Partners, LLC

243 Testing of Asphalt Concrete Mixtures Practice Problem 2: Volumetric Calculations The results of laboratory testing of a SM-12.5D yielded the following results: Percent Binder= 5.01 Correction Factor =.018 Asphalt Binder Specific Gravity = Percent minus 200 = Complete the following tables. Maximum Specific Gravity of Mix (G mm ): Variable Assignment Grams Mass Container in Air =A Mass Container in Water =B Mass Container and Sample in Air =C Mass Container and Sample in Water =D Maximum Specific Gravity (G mm ) = Bulk Specific Gravity of Mix (G mb ): Variable Assignment Specimen 1 Specimen 2 Specimen3 Mass of Specimen in Air =A SSD Mass of Specimen =B Mass of Specimen in Water =C Specimen Bulk Specific Gravity = Average G mb = 2A. Calculate the Effective Specific Gravity of the Aggregate (G se ) = VDOT and Platinum Performance Partners, LLC Chapter 9 page 43

244 Testing of Asphalt Concrete Mixtures 2B. Calculate the Bulk Specific Gravity of the Aggregate (G sb ) = 3. Calculate the VTM, VMA, VFA and F/A ratio for this mix. 4. Do all the volumetric properties meet the mix design criteria for this mix during production? Design Range Specification Calculated Meet Spec.? Criteria Criteria Results VTM VMA VFA F/A page 44 Chapter 9 VDOT and Platinum Performance Partners, LLC

245 Testing of Asphalt Concrete Mixtures Practice Problem 3: Volumetric Calculations The results of laboratory testing of an IM-19.0A yielded the following results: Percent Binder= 5.40 Correction Factor =.023 Asphalt Binder Specific Gravity = Percent minus 200 = Complete the following tables. Maximum Specific Gravity of Mix (G mm ): Variable Assignment Grams Mass Container in Air =A Mass Container in Water =B Mass Container and Sample in Air =C Mass Container and Sample in Water =D Maximum Specific Gravity (G mm ) = Bulk Specific Gravity of Mix (G mb ): Variable Assignment Specimen 1 Specimen 2 Specimen3 Mass of Specimen in Air =A SSD Mass of Specimen =B Mass of Specimen in Water =C Specimen Bulk Specific Gravity = Average G mb = 2A. Calculate the Effective Specific Gravity of the Aggregate (G se ) = VDOT and Platinum Performance Partners, LLC Chapter 9 page 45

246 Testing of Asphalt Concrete Mixtures 2B. Calculate the Bulk Specific Gravity of the Aggregate (G sb ) = 3. Calculate the VTM, VMA, VFA and F/A ratio for this mix. 4. Do all the volumetric properties meet the mix design criteria for this mix during production? Design Range Criteria VTM Specification Criteria Calculated Results Meet Spec.? VMA VFA F/A page 46 Chapter 9 VDOT and Platinum Performance Partners, LLC

247 MCS: Asphalt Plant Certification 10 Quality Acceptance & Data Processing Since the 1960s, the Federal Highway Administration has encouraged Departments of Transportation and Contractors to use quality control and quality assurance (QA/QC) specifications, which are statistically based. Since then, a QA specification has become an important component in an organization s commitment to overall quality management. The QA specification is a combination of end-result specifications and materials and methods specifications. The highway agency is responsible for the acceptance of the product that is produced by the Contractor who is implementing quality control in order to produce a product that meets the specifications provided by the agency. The Contractor is responsible for quality throughout hot mix asphalt production and placement. Therefore, the Contractor must ensure that the materials and work provided by subcontractors, suppliers, and producers are adequate and meet the specifications of the project. In addition to assuring the production of a quality product, all personnel must also maintain accurate records throughout the production process. This is especially important when the data is being recorded for computer input and processing. In this chapter we provide specifics on VDOT s Quality Acceptance process and information to enable the accurate entry and processing of test results. Learning Objectives: Upon completion of this chapter, you should be able to: Describe the acceptance process Compare the mean test results of samples to acceptable standards Calculate the acceptance or failure for gradation and asphalt content Calculate adjustments on material failing gradation and asphalt content Compute the standard deviation of tests Follow data entry guidelines to ensure accurate data processing VDOT and Platinum Performance Partners, LLC Chapter 10 page 1

248 Quality Acceptance & Data Processing Acceptance through Quality Assurance DEFINITIONS. The following terms will be used throughout this section: Acceptance range Adjustment Mean Quality assurance The job mix formula, with tolerances applied. A reduction in unit bid prices on failing material. The average of two or more numbers. The systematic monitoring and evaluation of various aspects of a project, to maximize the probability that minimum standards of quality are being attained by the production process. The Quality Assurance (QA) process typically consists of several activities including: process control, acceptance, and sometimes independent assurance of product (Buttlar and Harrell, 1998) 1. Figure 10-1 illustrates common components of the QA/QC process. Many of these have already been discussed in previous chapters. In this chapter we will examine the quality assurance, adjustment, and acceptance components. Figure Component of QA/QC Programs 1 Buttlar, W.G., and Harrell, M. (1998). Development of End-Result and Performance-Related Specifications for Asphalt Pavement Construction in Illinois. Transportation Conference Proceedings, pp Chapter 10 page 2 VDOT and Platinum Performance Partners, LLC

249 Quality Acceptance & Data Processing QA Specifications QA specifications typically are statistically based specifications designed to reward good quality and penalize poor quality. These specifications use methods such as random sampling, in which the properties of the desired products or constructions are described by appropriate statistical parameters and lot-by-lot testing. These methods help the contractor know whether or not the operations are producing the acceptable product. Acceptance Acceptance will be made under the Department s quality assurance program, which includes the testing of Production samples by the Contractor Monitor samples by the Department. Acceptance Activities The following critical activities must be performed by the Contractor and Department, respectively. Performed by the Contractor Sampling and testing for the determination of gradation, asphalt cement, content, and mix temperature Provide copies of such test results to the Department on forms furnished by the Department Performed by the Department Perform independent monitor checks at a laboratory of its discretion Review test results Test Results Indicate Mixture Conformance to Specifications If the Contractor s test results indicate that the mixture conforms to the gradation, asphalt cement, content and mix temperature requirements of the Specifications, the mixture will be acceptable for these properties. However, nothing herein shall be construed as waiving the requirements of Sections , and , and 315 or relieving the Contractor of the obligation to furnish and install a finished functional product which conforms to the requirements of the contract. Test Results Indicate a Statistically-Significant Difference If a statistical comparative analysis of the Contractor s test results and the Department s monitor tests indicate a statistically significant difference in the results and either of the results indicates that the material does not conform to the grading and asphalt cement content requirements of the Specifications, an investigation will be made to determine the reason for the difference. In the event it is determined from the investigation that the material does not conform to the requirements of the contract, price adjustments will be made in accordance with the requirements of Section VDOT and Platinum Performance Partners, LLC Chapter 10 page 3

250 Quality Acceptance & Data Processing Basis for Acceptance for Gradation and Asphalt Cement Content Acceptance for gradation and asphalt cement content will be based on the mean of the results of eight tests performed on samples taken in a stratified random manner from each 4000 ton lot. (Note: 8000 ton lots may be used when the normal daily production of the source from which the material is being obtained is in excess of 4000 tons.) AWARENESS/IMPORTANT Unless otherwise approved by the Engineer, samples shall be obtained from the approximate center of the truckload of material. Highlights a step in the procedure which is either unusual or very particular to this procedure. May also indicate awareness (additional information) or a cautionary concern in the procedure. Any statistically acceptable method of randomization may be used to determine when to take the stratified random sample; however, the Department shall be advised of the method to be used prior to beginning production. A lot will be considered to be acceptable for gradation and asphalt content if the mean of the test results obtained is within the tolerance allowed for the job mix formula as specified in Table II-15, shown here as Figure Table II-15 PROCESS TOLERANCE Number of Tests Top 1 Size 1 1/2 1 3/4 1/2 3/8 No. 4 No. 8 No. 30 No. 50 No. 200 A.C Defined as the sieve that has 100% passing as defined in Table II-13. Figure Tolerance on Each Laboratory Sieve and Asphalt Content Percent Plus and Minus Chapter 10 page 4 VDOT and Platinum Performance Partners, LLC

251 Quality Acceptance & Data Processing If the job mix formula is modified within a lot, the mean test results of samples taken will be compared to the applicable process tolerance shown in Figure INSPECTION AND MEASUREMENTS Visual Examination Should visual examination by the Engineer reveal that the material in any load or portion of the paved roadway is obviously contaminated or segregated, that load or portion of the paved roadway will be rejected without additional sampling or testing of the lot. Describes inspection, Quality Assurance and/or Quality Control practices. If it is necessary to determine the gradation or asphalt content of the material in any load or portion of the paved roadway, samples will be taken, tested, and the results compared to the requirements of the approved job mix formula. AWARENESS/IMPORTANT The results obtained in the testing will apply only to the material in question. Highlights a step in the procedure which is either unusual or very particular to this procedure. May also indicate awareness (additional information) or a cautionary concern in the procedure. VDOT and Platinum Performance Partners, LLC Chapter 10 page 5

252 Quality Acceptance & Data Processing Acceptance Calculations for Gradation and Asphalt Content As previously stated, acceptance for gradation and asphalt content will be based on a mean (average) of the results of tests performed on samples taken in a stratified random manner from each lot. Calculating the Acceptance or Failure for Gradation and Asphalt Content STEP 1. Obtain the job mix formula. a. The job mix formula is found on Form TL-127 (see Chapter 7) as submitted by the Contractor/Technician for the type mixture being produced. b. Each approved job mix formula shall remain in effect, provided the results of tests performed on material currently being produced consistently meet the requirements of the job mix for grading, asphalt content, temperature, Superpave compaction results, and the requirements of Section 315. STEP 2. Determine the number of tests performed on the quantity of material tested for acceptance. Usually the quantity of material tested for acceptance is a lot (4000 or 8000 tons), which requires 8 tests (one for every 500 or 1000 tons). Example: Lot = 4000 or 8000 tons = 8 Tests STEP 3. Calculate the acceptance range, as illustrated in Figure To calculate the acceptance range, the process tolerance for the number of tests performed is applied to the job mix. Acceptance Range = Job Mix Process Tolerance. Example: (8 Tests) Type Mix: IM-I9.0A Job Mix Sieves Job Mix Formula Total % Passing Process Tolerance for 8 Tests Acceptance Range 1 in ± /4 in ± /2 in ± No ± No ± Asphalt 5.4 ± Figure Calculating the Acceptance Range Chapter 10 page 6 VDOT and Platinum Performance Partners, LLC

253 Quality Acceptance & Data Processing STEP 4. Calculate the mean (average) of the test results for each job mix sieve, and asphalt content, as is illustrated in Figure Mean (average) = Sum of Test Results Number of Tests Accept. Range Sample No Aver. Lower Upper Job Mix 1 in /4 in /2 in No No Asphalt Figure Calculating the Mean of the Test Results STEP 5. Compare the mean (average) of the test results to the acceptance range. Example: The averages of the above lot are within the acceptance range. Conclusion: This lot passes. VDOT and Platinum Performance Partners, LLC Chapter 10 page 7

254 Quality Acceptance & Data Processing Adjustment System DEFINITION Adjustment A reduction in unit bid price on failing material. Describes and/or defines terminology. In the event a lot of material does not conform to the acceptance requirements, one adjustment point will be applied for each 0.1% that the material is out of the process tolerance for asphalt content, as shown in Figure This means that 10 adjustment points will be applied for each 1% that the material is out of conformance. Sieve Size Adjustment Points For Each 1% that the Gradation Is Outside The Process Tolerance Permitted In Table II-15 (Applied in 0.1 Increments) 2 in 1 1 ½ in 1 1 in 1 3/4 in 1 1/2 in 1 3/8 in 1 No. 4 1 No. 8 1 No No No Asphalt Content 10 Figure Adjustment Points Chapter 10 page 8 VDOT and Platinum Performance Partners, LLC

255 Adjustment Conditions and Actions Quality Acceptance & Data Processing The decision table that follows illustrates actions that will be taken for specific adjustment conditions. Adjustment Condition IF the total adjustment for a lot is greater than twenty-five (25) points IF the total adjustment is twenty-five (25) points or less AND the Contractor does not elect to remove and replace the material Adjustment Action THEN the failing material shall be removed from the road THEN the unit price paid for the material will be reduced 1% of the unit price bid for each adjustment point AWARENESS/IMPORTANT The adjustment will be applied to the tonnage represented by the sample or samples. In the event adjustment points are applied against two (2) successive lots, plant adjustment shall be made prior to continuing production. Highlights a step in the procedure which is either unusual or very particular to this procedure. May also indicate awareness (additional information) or a cautionary concern in the procedure. VDOT and Platinum Performance Partners, LLC Chapter 10 page 9

256 Quality Acceptance & Data Processing Calculating Adjustments on Material Failing Gradation and Asphalt Content Follow the steps in this section to determine how to calculate adjustments on material failing gradation and asphalt content. For the purpose of this example, assume: Type Mix SM -12.5A. Accept. Range Sample No Average Lower Upper Job mix P/F 3/4 in /2 in /8 in No F No F Asphalt F STEP 1. Compute the adjustment on the No. 8 (2.36mm) sieve. Refer to the adjustment point table for gradation and note that, for the No. 8 (2.36mm) sieve, a point adjustment for each 1% that the gradation is outside the acceptance range is applied Lower Acc. Range 1.0 Adjustment for Each 1% Average #8 (2.36mm) Sieve x1.3% Outside Acc. Range 1.3% Outside Acc. Range 1.3% Adjustment #8 (2.36mm) Sieve STEP 2. Compute the adjustment on the No. 200 (75 μm) sieve. Refer to the adjustment point table for gradation and note that for the No. 200 (75 μm) sieve, a 3-point adjustment for each 1% that the gradation is outside the acceptance range is applied. 4.9 Lower Acc. Range 3.0 Adjustment for Each 1% Average #200 (75 μm) Sieve x 0.9% Outside Acc. Range 0.9% Outside Acc. Range 2.7% Adjustment #200 (75 μm) Sieve STEP 3. Compute the adjustment on asphalt content. Refer to the specifications and note that one adjustment point will be applied for each 0.10% that the material is outside of the acceptance range. This statement means than 10 adjustment points will be applied for each 1% that the material is outside the acceptance range Lower Acc. Range 10 Adjustment for Each 1% Average Asphalt Content x 0.12% Outside Acc. Range 0.12% Outside Acc. Range 1.2% Adjustment Asph. Content Chapter 10 page 10 VDOT and Platinum Performance Partners, LLC

257 Quality Acceptance & Data Processing STEP 4. Compute the total adjustment. The total adjustment is the sum of the adjustments for gradation and asphalt content. 1.3 % Adjustment #8 (2.36 mm) Sieve 2.7 % Adjustment#200 (75 μm) +1.2 % Adjustment Asphalt Content 5.2 % Total Adjustment for Gradation and Asphalt Content Conclusion: An adjustment of 5.2 points should be applied to this lot. VDOT and Platinum Performance Partners, LLC Chapter 10 page 11

258 Quality Acceptance & Data Processing Standard Deviation (Calculation of Variability) Standard deviation is a measure of variability indicating the amount of variation from the mean. The Contractor shall control the variability of his product in order to furnish a uniform mix. When the quantity of any one type material furnished to a project exceeds 4000 tons, the variability of the total quantity furnished will be measured by calculating the standard deviation for each sieve size and the asphalt content. In the event the standard deviation is within the limits shown in the Standard Deviation Table II-16 (Figure 10-6), the unit bid price for the material will be reduced by 0.5% for each adjustment point applied. AWARENESS/IMPORTANT Standard deviation computations will not be made separately on more than two job mixes for the same type material, unless a change is requested by VDOT. Highlights a step in the procedure which is either unusual or very particular to this procedure. May also indicate awareness (additional information) or a cautionary concern in the procedure. Sieve Size and Asphalt Content 1 adjustment point for each sieve size and asphalt content Table II-16 STANDARD DEVIATION (Determination of Variability) 2 adjustment points for each sieve size and asphalt content 3 adjustment points for each sieve size and asphalt content 1/2 inch /8 inch No No No No No Asphalt Content Figure 10-6: Standard Deviation Chart The disposition of material having standard deviations larger than those shown in Table II-16 will be determined by the Engineer. Chapter 10 page 12 VDOT and Platinum Performance Partners, LLC

259 Quality Acceptance & Data Processing Computing Standard Deviations Standard deviation is usually designated by the Greek symbol σ. In mathematical equation form standard deviation is equal to: Where: While the formula may look complicated, the actual computing of the standard deviation is simple. The following example shows the procedure which should be used. Example Computation Given the following four test results for the No.8 (2.36mm) sieve, SM-9.5A mix: Find: Test #1-59.3%, Test #2-53.1%, Test #3-64.7%, Test #4-55.7%. STEP 1. Set up a table as shown below. In the column headed Sample Number, list 1, 2, 3, 4, since there were four tests. The last cell in this column should read SUM. Sample Number SUM X X - (X - ) 2 VDOT and Platinum Performance Partners, LLC Chapter 10 page 13

260 Quality Acceptance & Data Processing STEP 2. In the column headed X, list the individual test results in the problem. Sample X X - (X - ) 2 Number SUM STEP 3. Add the results in the X column and place the total (232.8) in the final row for that column. Sample X X - (X - ) 2 Number SUM STEP 4. Divide this total by the number of tests (n), which in this case n = 4. This gives an average percent passing the No.8 (2.36mm) sieve of Place this value in all of the test rows of the column. Note: The average should always be shown to the nearest one-hundredth of a percent (two decimal places). Sample X X (X ) 2 Number SUM Chapter 10 page 14 VDOT and Platinum Performance Partners, LLC

261 Quality Acceptance & Data Processing STEP 5. Subtract the values in the column from those in the X column and record these values in the X column Sample Number As a check, the values in this column can be added algebraically and should equal zero, except in cases where the average is not exact and has been rounded off to two decimal places. X X (X ) SUM STEP 6. Square the values in the X column and record these values in the (X ) 2 column x 1.10 = x 5.10 = x 6.50 = x 2.50 = Sample Number X X - (X - ) SUM VDOT and Platinum Performance Partners, LLC Chapter 10 page 15

262 Quality Acceptance & Data Processing STEP 7. Add the (X - )² column and record the value of as shown. Sample X X - (X - ) 2 Number SUM STEP 8. Divide this value by the number of samples (n) minus 1. In this case there are 4 samples, so (n-1) = 4-1 = / 3 = STEP 9. Finally, determine the square root of , the value calculated from Step 8. This is the standard deviation of the four test results: σ = ) 2 X- X 2 = ) 2 = = 5.02 = 5.02 = = Conclusion: The standard deviation (σ) equals 5.02 Chapter 10 page 16 VDOT and Platinum Performance Partners, LLC

263 Automated Data Processing for Asphalt Concrete Quality Acceptance & Data Processing The purpose of the data system for which these instructions were prepared is to provide descriptive information about the materials used in highway work. The data processing system is designed for coding test reports. For instance, in lieu of recording the Contractor s name and location, only a 4-digit code will be required. The printout will show the Contractor s name and location. The codes may be obtained from the District Materials Section. It is very important for the success of the computer program that all data entered on the Data Processing Forms: Is correct Is placed in the proper blanks Is legible As a rule, numeric characters are recorded from the right to left and alphabetic from the left to right. Please adhere to these standards. When the coding input forms have been completed by the Contractor/Technician, they should be submitted to the District Materials Section for review and processing. After processing, the forms will be retained by the District Materials Section for the duration of the project. Completing Form TL-100A The Asphalt Test Results Input Form The records input data are self-explanatory, based on the field names on this report. There are eight data records, which allow for the entry of the test data for eight tests, which is the normal lot size (see revised Road & Bridge Specifications , Adjustment System). Simply enter the codes and/or test data where specified. The codes for the contracts will be put on the forms by the Department, as illustrated by Figure 10-7 on the next page. VDOT and Platinum Performance Partners, LLC Chapter 10 page 17

264 Quality Acceptance & Data Processing Figure The Asphalt Concrete Test Results Input Form Chapter 10 page 18 VDOT and Platinum Performance Partners, LLC

265 Quality Acceptance & Data Processing Specification Reference Tables Specification tables for use in completing calculations are reproduced her for ease of access. Table II -13 ASPHALT CONCRETE MIXTURES-DESIGN RANGE Percentage by Mass Passing Square Mesh Sieves Mix Type 2 in. 1 ½ in. 1 in. 3/4 in. 1/2 in. 3/8 in. No. 4 No. 8 No. 30 No. 50 No. 200 SM-9.0 A,D,E max SM-9.5 A,D,E max SM-12.5 A,D,E max IM-19.0 A,D,E max BM max C (curb mix) Legend: SM = Surface Mixture; IM = Intermediate Mixture, BM = Base Mixture, C = Curb Mixture * A production tolerance of 1% will be applied to this sieve, regardless of the number of tests in the lot. Table II-15 PROCESS TOLERANCE Number of Tests Top 1 Size 1 1/2 1 3/4 1/2 3/8 No. 4 No. 8 No. 30 No. 50 No. 200 A.C Defined as the sieve that has 100% passing as defined in Table II-13. VDOT and Platinum Performance Partners, LLC Chapter 10 page 19

266 Quality Acceptance & Data Processing Sieve Size Adjustment Points For Each 1% that the Gradation Is Outside The Process Tolerance Permitted In Table II-15 (Applied in 0.1 Increments) 2 in 1 1 ½ in 1 1 in 1 3/4 in 1 1/2 in 1 3/8 in 1 No. 4 1 No. 8 1 No No No Asphalt Content 10 Sieve Size and Asphalt Content 1 adjustment point for each sieve size and asphalt content Table II-16 STANDARD DEVIATION (Determination of Variability) 2 adjustment points for each sieve size and asphalt content 3 adjustment points for each sieve size and asphalt content 1/2 inch /8 inch No No No No No Asphalt Content Chapter 10 page 20 VDOT and Platinum Performance Partners, LLC

267 Quality Acceptance & Data Processing Chapter Ten Knowledge Check 1. A mathematical analysis of accumulated data is called: A. Design range B. Statistics C. Viscosity D. Process tolerance 2. The job mix formula with the tolerance applied is the: A. Reference guide B. Acceptance range C. Control guide D. Process tolerance 3. The quantity of material to be checked for compliance with specifications is called: A. Gradation B. A lot C. The referee system D. The design range 4. The job mix formula is chosen from the: A. Standard deviation range B. Design range C. Process tolerance range D. Acceptance range 5. A reduction in the unit bid price of material is known as: A. The standard deviation B. A control guide C. A price adjustment D. The design range adjustment. VDOT and Platinum Performance Partners, LLC Chapter 10 page 21

268 Quality Acceptance & Data Processing 6. When the normal daily production of the source from which asphalt concrete is being obtained is in excess of 4000 tons, the lot size may be increased to: A tons B tons C tons D ton 7. Standard deviation computations are not normally made on more than two job mixes for the same type material on a single project. A. True B. False 8. The amount of deviation allowed from the job mix formula is known as the: A. Design range B. Process tolerance C. Weigh tolerance D. Standard deviation 9. How many adjustment points may a material have and still remain in the road? A. More than 30 B. More than 25 C. 25 or less D. None of the above 10. Variability can be computed on any number of samples except: A. One B. Two C. Three D. None of the above Chapter 10 page 22 VDOT and Platinum Performance Partners, LLC

269 Quality Acceptance & Data Processing 11. Would the process tolerance be the same for three tests as a lot with eight tests? A. Yes B. No 12. After running analysis on a sample, how is it checked for conformity with specifications? 13. On a failing lot, who is responsible for applying the adjustment points? 14. If a job mix is in the design range, can it be disapproved? 15. Where are the standard deviation limits found for asphalt concrete? 16. What number of adjustment points constitutes the removal of the material from the road? 17. Why is it important that a Producer know what the product variability is at all times? 18. Calculations for the gradation of aggregate in the mixture are shown to what percent? What percent is the asphalt content? 19. What, if any adjustment points would be applied to a mix if the standard deviation for the No.200 material is 2.3? VDOT and Platinum Performance Partners, LLC Chapter 10 page 23

270 Quality Acceptance & Data Processing Problem No.1 Using the information given below, complete the Form TL-100A on the next page. Producer: Flatt Top Paving Company - code 1048 Wet Mixing Time: 27 seconds Asphalt Cement Supplier: Alright Asphalt Products - code 23. Lot tons The material is being shipped to PM-1L-05. Job Mix Information: Type SM-12.5A mix code number - 15 Job Mix Number: Test Results #1 #2 #3 #4 Date Time 10:00 13:30 8:17 11:05 Ton Mix Temp. 310 F 310 F 305 F 308 F 3/4 in /2 in /8 in No No A.C VTM VMA VFA F/P be G mm Chapter 10 page 24 VDOT and Platinum Performance Partners, LLC

271 VDOT and Platinum Performance Partners, LLC Chapter 10 page 25 Quality Acceptance & Data Processing

272 Quality Acceptance & Data Processing Problem No. 2: Failure and Adjustment Using the information given below, calculate the failure and adjustment. The producer is Flatt Top Paving Company and the plant is a batch plant and operates on a 27 second wet mixing time. It has been assigned to Code Number 777. The material is being shipped to Schedule No , Item N. The asphalt cement is delivered from terminal No. 15. The samples represent Lot 1, which contains 2000 tons. Job Mix Information: Type SM-12.5A Mix code number - 16 Job Mix Number Job Mix 3/4 in /2 in /8 in 88.0 No No A.C Test Results: Sample #1 Sample #2 Sample #3 Sample # 4 Avg. Date Acc. Range Time 10:00 13:30 8:17 11:05 Ton Mix Temp. 310 F 310 F 305 F 308 F 3/4 in /2 in /8 in No No A.C Chapter 10 page 26 VDOT and Platinum Performance Partners, LLC

273 Quality Acceptance & Data Processing Problem No. 3: Computing Standard Deviation Using the information given below, determine the variability of the # 200 sieve. Test Results: Sample #1 Sample #2 Sample #3 Sample #4 Date Time 10:00 13:30 8:17 11:05 Ton Mix Temp. 310 F 310 F 305 F 308 F 3/4 in /2 in /8 in No No σ = ) 2 Sample # X X X X (X X ) 2 SUM = VDOT and Platinum Performance Partners, LLC Chapter 10 page 27

274 Quality Acceptance & Data Processing Problem No. 4: Computing Price Adjustment for Variability as measured by Standard Deviation A. Complete the following test report and if the material fails, indicate area(s) of failure. If the material can be accepted with adjustment, calculate the percent of adjustment. Accept. Range Sample # Aver. Lower Upper Job Mix P/F 1 1/2 in in /4 in No No A.C B. Using the test report above, determine the variability of the No. 8 (2.36mm) sieve by calculating the standard deviation. Determine if the variability meets the specification requirements. If not, how many adjustment points would be applied? σ = ) 2 Sample # X X X X (X X ) 2 SUM = Chapter 10 page 28 VDOT and Platinum Performance Partners, LLC

275 Quality Acceptance & Data Processing Problem No. 5: Computing Price Adjustment for Variability as measured by Standard Deviation A. Complete the following test report and if the material fails, indicate area(s) of failure. If the material can be accepted with adjustment, calculate the percent of adjustment. Accept. Range Sample # Aver. Lower Upper Job Mix P/F 1 1/2 in in /4 in No No A.C B. Using the test report above, determine the variability of the No. 8 (2.36mm) sieve by calculating the standard deviation. Determine if the variability meets the specification requirements. If not, how many adjustment points would be applied? σ = ) 2 Sample # X X X X (X X ) 2 SUM = VDOT and Platinum Performance Partners, LLC Chapter 10 page 29

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277 MCS: Asphalt Plant Certification A Glossary of Terms and Definitions.45 Power Chart A graphical technique that plots the percent passing vs. sieve size. This chart is very useful in comparing aggregate gradations and specification limits Absorptiveness Acceptance Range Adhesion Adjustment Aggregate Aggregate Blending Anionic Anti-Stripping Agent Artificial or Synthetic Aggregate Asphalt Cement (Performance Graded Binder) Asphalt Concrete Asphalt Concrete Base Course The ability of the aggregate used in the mix to absorb asphalt. The job mix formula with the tolerances applied. The binder s ability to stick to the aggregate in the paving mixture. A reduction in unit bid price on failing material. An inert granular material such as sand, gravel, shell, slag, or broken stone, which generally constitutes 90 to 95% of the total asphalt concrete mixture by weight. The process of proportionately mixing several aggregate gradations to obtain one desired aggregate gradation. Binder globules are electro-negatively charged. A heat stable additive used to prevent the binder separating from the aggregate. Aggregates resulting from the modification of raw materials, which may involve both physical and chemical changes, such as slag and fly ash. Petroleum asphalt for use in pavements is called asphalt cement or paving asphalt. At ambient temperatures, it is a black, sticky, semisolid, highlytemperature-dependent visco-elastic material. A composite of materials consisting of two components: aggregates and asphalts. A foundation course consisting of graded aggregate and asphalt cement mixed in a hot mix plant (Type BM mixes). VDOT and Platinum Performance Partners, LLC Appendix A page 1

278 Glossary of Terms and Definitions Asphalt Concrete Intermediate Course Asphalt Concrete Surface Course Base Mixes (BM) Batch Asphalt Plant Carry-over Cationic Coarse Aggregate Coarse Aggregate Angularity (CAA) Cohesion Cold Aggregate Bins and Feeders Cold Elevator Combined Gradation Consensus Property Testing Consistency Control Chart A course between the asphalt concrete base and the asphalt concrete surface course. It is also referred to as a binder course (Type IM mixes). A dense graded, hot mix asphalt concrete placed as the top course of a pavement structure. It is also referred to as a wearing course (Type SM mixes). Placed immediately below the surface course (or binder course if a binder course is found to be necessary), this layer is called the base course (Type BM mixes) and is the structural strength element of the asphalt concrete pavement system. A manufacturing facility for producing hot asphalt mix that makes the product in batches, rather than continuously. The depositing of finer material in a bin that should contain the next larger size aggregate. Binder globules are electro-positively charged. All the material retained on and above No. 4 (4.75 mm) sieve. The angularity of coarse aggregate. The binder s ability to hold the aggregate particles in place in the finished pavement. Containers that store aggregate and accurately feed required amounts of each size to comply with specifications and to maintain a balance of material in each of the hot bins. Conveyor belt that picks up the blended aggregate at the cold feed and feeds it to the dryer in a continuous flow. A mathematically-determined theoretical combination of aggregates based on their relative percent volume in the mixture. Testing that places consensus requirements on coarse and fine aggregate angularity, flat and elongated particles, and clay content. The degree of fluidity or plasticity of the binder at any particular temperature. A control chart is a graphical record of data taken from a repetitive process, and is used to alert the Producer as to when to investigate the process. page 2 Appendix A VDOT and Platinum Performance Partners, LLC

279 Glossary of Terms and Definitions Cutback Asphalt Cutting Back Design Range Drum-Type Asphalt Plant Asphalt cement which has been liquefied by blending it with petroleum solvent. There are three types: Rapid-Curing (asphalt and a volatile solvent or light distillate), Medium-Curing (asphalt and a solvent of intermediate volatility or medium distillate) and Slow-Curing (asphalt and an oily diluent of low volatility). The process of dissolving a binder in selected solvents. The range from which the job-mix is chosen. A manufacturing facility for producing HMA. It manufactures HMA continuously, rather than in batches. Dryer A revolving cylinder, usually from 1 to 3 meters in diameter and 6 to 12 meters long, in which aggregate is dried and heated. Dry Mixing Time Ductility Durability Dust Collector (aka Emissions Control System) Effective Asphalt Content Emissions Control System (aka Dust Collector) Emulsified Asphalt Fatigue Resistance Fine Aggregate Fine Aggregate Angularity (FAA) Fines to Asphalt Ratio (F/A) The time between the release of the dry batch into the pugmill and the release of the asphalt into the pugmill. An indication of the cohesiveness (stickiness) of an asphalt. The binder s resistance to the effects of traffic, water, air, and temperature changes. A fan in the unit furnishing the draft that controls the gas and air flow for dryer combustion system and dust collection. The volume of asphalt not absorbed by the aggregate. A fan in the unit furnishing the draft that controls the gas and air flow for the dryer combustion system and dust collection. A suspension of asphalt in water containing an emulsifying agent, such as soap. The asphalt pavement s resistance to repeated flexing or slight bending under wheel loads (e.g., traffic). All the material passing the No. 4 (4.75 mm) sieve, consisting of natural sand, crushed stone sand or crushed gravel stone dust. The angularity of fine aggregate. Indicates the film thickness of coated particles. VDOT and Platinum Performance Partners, LLC Appendix A page 3

280 Glossary of Terms and Definitions Flat & Elongated (F/E) Flash Point Flexibility Gradation Hot Aggregate Storage Bins (aka Hot Bins) Hot Elevator Hot Mix Impermeability Intermediate Mixes (IM) Job Mix Formula (JMF) Liquid Asphalt Lot Mean Medium Curing Cutback Asphalt Mineral Filler Mixer (Pugmill) The dimensional ratio at which an aggregate particle is considered too flat or too elongated. The temperature at which asphalt will instantaneously flash in the presence of an open flame. The asphalt pavement s ability to adjust to gradual settlements and movements in the subgrade without cracking. The particle size distribution of an aggregate, which helps determine the properties of pavement materials. Bins that temporarily store the heated and separated aggregates in the various size fractions required, prior to their final proportioning into the mixer. Carries the hot, dried aggregate from the dryer and deposits it onto a screening unit (also called a screen deck or a plant screen). A mixture of graded aggregates with asphalt cement, heated and mixed in a pugmill and placed hot on the road. The resistance of an asphalt pavement to the passage of air and water into or through it. Used as a binder course between the surface course and base course when needed to add strength and thickness to the pavement structure. The optimized mixture of aggregate and asphalt binder type; the required AC and Gradation targets that the contractor must produce for the project Asphalt cement which has been liquefied with petroleum solvents or emulsified. The quantity of material to be checked for compliance with specifications. The average of two or more numbers. Asphalt cement blended with a kerosene-type material. Finely divided mineral matter, such as dust rock, including limestone dust, slag dust, hydrated lime, hydraulic cement, or other suitable mineral matter. Modern hot mix asphalt plants use pugmill mixers. These consist of twin shafts equipped with paddles for mixing the aggregate and asphalt into a homogeneous mass. page 4 Appendix A VDOT and Platinum Performance Partners, LLC

281 Glossary of Terms and Definitions Natural Aggregate Normal Distribution Penetration Performance Graded Binder Percent Binder (P b ) Plans Plant Screens Prime Coat Process Tolerance Production Tolerance Pugmill Purity Quality Assurance Random Sample RAP Rapid Curing Cutback Asphalt An aggregate made of natural material such as granite, quartz, gravel, etc. (Pit or back run, or processed aggregates) A pattern for the distribution of a set of data which follows a bell shaped curve. A method of classification that is used to determine the consistency and hardness of asphalt. A dark brown to black solid or semi-solid asphalt substance that is found in natural beds or is obtained as a residue in petroleum refining. The terms performance graded binder and asphalt cement are used interchangeably. The percent of asphalt binder in the mix by mass (as a percent of the total mix mass). Drawings that show the location, character, dimensions, and details of the work to be done. Screens located between the dryer and hot bins which separate the heated aggregate into the proper hot bin sizes. An initial application of low viscosity liquid asphalt, such as RC-70, MC-70, and RC-250, to an absorbent base prior to placing an asphaltic course. Emulsified asphalts such as CRS-2, CMS-2, and CMS-2h may also be used. The amount of deviation allowed from the job mix formula. The allowable target-miss that is allowed during production before price adjustments are applied. Chamber in which the batch is mixed and discharged into the truck or hauling unit. The degree to which the binder is pure (i.e., free from impediments such as moisture). The systematic monitoring and evaluation of various aspects of a project, to maximize the probability that minimum standards of quality are being attained by the production process. Samples taken from locations which have been selected solely by chance. These samples differ from representative samples, in that there is no judgment involved in trying to select the best, the worst, or in-between spot for sampling. Reclaimed asphalt pavement. Asphalt cement blended with a naphtha or gasoline-type material. VDOT and Platinum Performance Partners, LLC Appendix A page 5

282 Glossary of Terms and Definitions Referee System Representative Sample Sample Splitter Sampling Device Sampling Gates Sand Equivalent (SE) Screening Unit (Plant Screens or Screen Deck) Sieve Analysis Skid Resistance Slurry Special Provisions Special or Supplemental Specifications Specific Gravity Stability Standard Deviation A system to allow for additional sampling and testing when there is doubt that the original test results are valid. A relatively small portion of material having the physical and chemical properties as the group or lot from which it is taken. A device used to divide samples of aggregate and other granular materials. A device used to obtain a representative sample of aggregates. Gates or windows in the sides of the hot bins that allow the technician to sample aggregates at the plant. The relative proportions of fine dust or clay-like materials in fine aggregate (or granular soils). Screens located between the dryer and hot bins which separate the heated aggregate into the proper hot bin sizes. The process of determining the distribution of particle sizes, expressed as a percent of the total dry weight. It is used to determine the gradation or distribution of aggregate particle sizes within a given sample of aggregate material. The ability of an asphalt surface to minimize skidding or slipping of vehicle tires, particularly when wet. A mixture of aggregate, asphalt emulsion, and filler, and water, which are mixed together according to a laboratory s design-mix formula. Additions or revisions to the standard or supplemental specifications that are applicable only to an individual project. Approved additions and revisions to the standard specifications. A unit-less ratio of a material s density relative to water when both are at the same temperature (i.e., if we say a material has a specific gravity of 2, then it has twice the mass of water for a given volume. The term 15.6ºC/15.6ºC indicates that both the asphalt and water weights were measured at 15.6ºC. The asphalt pavement s ability to resist displacement (e.g., shoving and rutting) and shearing stress under loads (e.g., traffic).. A measure of variability indicating the amount of variation from the mean. page 6 Appendix A VDOT and Platinum Performance Partners, LLC

283 Glossary of Terms and Definitions Standard Specifications Statistical Control Statistics Storage Silos Stratified Random Sample Stripping Subbase Subgrade Superpave Surface Mixes (SM) Surge Silos Tack Coat Tell-tale Lever Temperature Susceptibility Tensile Strength Ratio (TSR) Thermoplastic Material Thin Binder Film Directions, provisions, and requirements for performing the work illustrated and described in the plans. The items in the standard specifications relate to or illustrate the method and manner of performing the work or describe the qualities and quantities of materials and labor to be furnished under the contract. When repeated measurements from a process are normally distributed about a target value. A mathematical analysis of accumulated data. Silos that are well insulated, heated, near air tight, and are designed to hold hot mix for long periods of time (up to one week). Samples taken from equal portions of a lot at locations which have been selected solely by chance. Separation of asphalt binder film from aggregate surfaces. The layer of aggregate material laid on the subgrade. The native material (i.e., level layer of rock or earth) upon which the foundation of a road is constructed. Superpave is an acronym for Superior Performing Asphalt Pavements, a comprehensive asphalt mix design, evaluation, and analysis system. The upper most layer of the pavement structure is called the surface or wearing course. Silos that are usually insulated, but unheated and are designed to hold hot mix for short periods of time (up to several hours) between truck arrivals. A thin application of emulsified asphalt to an old pavement or base. It may be used to secure the bond where the mix is laid in more than one course. A device on the hot bins of a continuous mix plant that indicates when the material level in the bin is too low. The effect of temperature on a binder s viscosity and elasticity. Measures the strength loss resulting from damage caused by stripping under laboratory-controlled accelerated freeze-thaw conditioning. A plastic that softens when heated and hardens when cooled without changing its engineering properties. The film coating aggregate particles. VDOT and Platinum Performance Partners, LLC Appendix A page 7

284 Glossary of Terms and Definitions Trial and Error Method Total Asphalt Content Variability Viscosity Void Content Voids Filled with Asphalt Voids in the Mineral Aggregate (VMA) Voids in the Total Mixture (VTM) Volumetric Batch Plant Washed Sieve Analysis Weigh Box Weigh Batch Plant Weight Tolerances Wet Mixing Time Workability The method used to determine an optimum combination of aggregates. The amount of asphalt that must be added to the mixture to produce the desired mix qualities. Changeability of the product. A measure of liquid s resistance to flow. Empty spaces within the aggregate particle that can become filled with water, binder, or both. The percentage of voids in the compacted aggregate mass that are filled with asphalt cement; also known as the Asphalt Void Ratio. The air void spaces that exist between the aggregate particles in a compacted paving mixture, including spaces filled with asphalt. The part of the compacted mixture not occupied by aggregate or asphalt, expressed as a percentage of the total volume. VTM is synonymous with Air Voids. An asphalt concrete mixing plant that proportions aggregate and asphalt constituents into the mix by volumetrically measured batches. The method used in Virginia to determine the proportions of various particle sizes in a mineral aggregate. A weigh box or hopper in batch plants connected with the scales, which weighs each aggregate fraction before dropping the aggregate into the pugmill. An asphalt concrete mixing plant that proportions the aggregate constituents into or volume. Permissible variations from the exact desired proportions of aggregates and asphalt material as delivered into the pugmill. The time between the release of the asphalt into the pugmill and the opening of the pugmill discharge gate. The ease with which a paving mixture can be placed and compacted. page 8 Appendix A VDOT and Platinum Performance Partners, LLC

285 MCS: Asphalt Plant Certification B Materials Specifications Table of Contents Section 210--Asphalt Materials Description Materials Detail Requirements Payment Adjustment System... 3 Section 211 Asphalt Concrete Mixtures (SUPERPAVE) (Feb 9, 2010) Description Materials Job-Mix Formula Asphalt Concrete Mixtures Testing Tests Plant Inspections Acceptance Adjustment System Referee System Handling and Storage of Aggregates Asphalt Concrete Mixing Plant Preparation of Mixture Storage System Initial Production Section 248 Stone Matrix Asphalt Concrete (Feb. 9, 2010) Description Materials Composition of SMA Mixture Acceptance SMA Mixing Plant VDOT and Platinum Performance Partners, LLC Appendix B page 1

286 Materials Specifications Section 210--Asphalt Materials Description These specifications cover asphalt material consisting of asphalt, asphalt cement, asphalt cutback, or asphalt emulsion as defined in ASTM D8. a. Asphalt Cements Whenever and wherever within the Contract documents asphalt cements are specified, they shall be defined as Strategic Highway Research Project (SHRP) Performance Graded (PG) asphalt cements. Substitution of AASHTO designated asphalt cements with performance graded asphalt cements shall be in accordance with the following: AASHTO DESIGNATION AC-5 AC-10 AC-20 AC-30 AC-40 SHRP DESIGNATION PERFORMANCE GRADED * PG PG PG PG PG * PG asphalts shall conform to the requirements of AASHTO Provisional Specifications MP Materials Asphalt material shall be homogeneous and shall conform to the following: 1. Rapid curing and medium curing liquid asphalts used as surface treatments shall contain a heatstable additive conforming to the requirements of Section Liquid asphalt material will be tested for coating ability in accordance with the requirements of AASHTO T182, with the following modifications: a. Material that can coat 95 percent of a shady dolomite will be classified Type I. b. Material that can coat 95 percent of a siliceous gravel wetted with 2 percent water by weight will be classified Type II. 3. Rapid curing cutback asphalts shall conform to the requirements of AASHTO M Medium curing cutback asphalts shall conform to the requirements of AASHTO M Cements shall be viscosity graded conforming to AASHTO M226, Table 2, except that the loss on heating shall be not greater than 1.0 for AC-5, 0.8 for AC-20 and 0.5 for all other grades. page 2 Appendix B VDOT and Platinum Performance Partners, LLC

287 Materials Specifications 6. Emulsions shall conform to the requirements of AASHTO M208 and shall be Type I as specified in 2.a. herein except that CRS-2 shall be Type II as specified herein. CRS-1h shall conform to the requirements of AASHTO M208 for CRS-1 except that the penetration shall be 40 to 110. Emulsions will be sampled and tested in accordance with the requirements of AASHTO T59 except that viscosity will be tested in accordance with the requirements of VTM Detail Requirements a. Shipping: Shipments of asphalt material shall be made in transporting media that are free from contamination. Tank trucks or trailers shall be equipped with a sampling device approved by the Engineer. The device shall have an inside diameter of 1/2 to 1 inch and a gate valve or petcock. The device shall be built into the tank or the recirculating or discharge line so that a sample can be drawn during circulation or discharge. b. Storing: Asphalt material to be stored shall be placed in storage tanks that are free from contamination Payment Adjustment System If the material represented by any one sample does not conform to the requirements herein and the material is a pay item, the contract unit price for the item will be reduced by 4 percent for each property that does not conform to the specifications for the quantity represented by the sample that was used on the project. Unused material represented by the failing sample will be rejected. If the material represented by a failing sample was not a pay item, the material will be considered unacceptable and shall be subject to the requirements of Sections and VDOT and Platinum Performance Partners, LLC Appendix B page 3

288 Materials Specifications Section 211 Asphalt Concrete Mixtures (SUPERPAVE) (Feb 9, 2010) Description Asphalt concrete shall consist of a combination of mineral aggregate and asphalt material mixed mechanically in a plant specifically designed for such purpose. An equivalent single axle load (ESAL) will be established by the Engineer, and SUPERPAVE mix types may be specified as one of the types listed as follows: Mix Type Equivalent Single-Axle Load (ESAL) Range (millions) Asphalt Performance Grade (PG)2 Aggregate Nominal Maximum Sieve in.1 SM-9.0 A 0 to /8 in SM-9.0 D 3 to /8 in SM-9.0 E Above /8 in SM-9.5 A 0 to /8 in SM-9.5 D 3 to /8 in SM-9.5 E Above /8 in SM-12.5 A 0 to /2 in SM-12.5 D 3 to /2 in SM-12.5 E Above /2 in IM-19.0 A Less than /4 in IM-19.0 D 10 to /4 in IM-19.0 E 20 and above /4 in BM-25.0 A All ranges in BM-25.0 D Above in 1. Nominal Maximum Size is defined as one sieve size larger than the first sieve to retain more than 10 percent aggregate. 2. Minimum Asphalt Performance Grade (PG) is defined as the minimum binder performance grade for the job mixes as determined by AASHTO T170 or AASHTO M320. Asphalt concrete shall conform to the requirements for the mix type designated. At the Contractor s option, Warm mix Asphalt (WMA) additive or process may be used in lieu of the appropriate HT Mix asphalt Materials a. Asphalt materials shall conform to the requirements of Section 210 except asphalt cement materials shall be performance graded (PG) in accordance with the requirements of AASHTO M320.In addition, asphalt mixtures with the E designation shall meet the asphalt cement requirements in Section (e)1. page 4 Appendix B VDOT and Platinum Performance Partners, LLC

289 Materials Specifications b. Coarse aggregate shall be Grade A or B, conforming to the requirements, except for grading, of Section 203 for quality. In addition, the coarse aggregate sizes retained on and above the No. 4 sieve shall comply with the coarse aggregate requirements in Table II-12A. Flat and elongated (F&E) particles shall be tested in accordance with the requirements of ASTM D 4791, and coarse aggregate angularity (CAA) shall be tested on crushed gravel only in accordance with the requirements of ASTM D c. Fine aggregate shall conform to the requirements except for grading of Section 202 for quality and the fine aggregate requirements in Table II-12A. Fine aggregate angularity (FAA) shall be tested in accordance with the requirements of AASHTO T 304 (Method A) and sand equivalent (SE) shall be tested in accordance with the requirements of AASHTO T 176. d. After a gradation is performed: 1. If 10 percent or more of the material is retained on the No. 4 sieve, that portion will be tested in accordance with the requirements for coarse aggregates. 2. If 10 percent or more of the material passes the No. 4 sieve, that portion will be tested for SE. 3. If 10 percent or more of the material passes the No. 8 sieve, that portion will be tested for FAA. e. Fine or coarse aggregates that tend to polish under traffic will not be permitted in any final surface exposed to traffic except in areas where the two-way average daily traffic is less than 750 vehicles per day and as permitted elsewhere in these specifications. VDOT and Platinum Performance Partners, LLC Appendix B page 5

290 Materials Specifications Table II-12A. Aggregate Properties Coarse Aggregate Properties CAA A STM D4791 Fine Aggregate Properties F & E 1 (5:1) Mix Type 1 fractured Face 2 fractured Faces Percent by weight SE FAA SM-9.0 A 85% min. 80% min. 10% Max1 40% min. 40% min. SM-9.0 D 85% min. 80% min. 10% Max1 45% min. 45% min. SM-9.0 E 95% min. 90% min. 10% Max1 45% min. 45% min. SM-9.5 A 85% min. 80% min. 10% Max1 45% min. 45% min. SM-9.5 D 85% min. 80% min. 10% Max1 45% min. 45% min. SM-9.5 E 95% min. 90% min. 10% Max1 45% min. 45% min. SM-12.5 A 85% min. 80% min. 10% Max1 45% min. 45% min. SM-12.5 D 85% min. 80% min. 10% Max1 45% min. 45% min. SM-12.5 E 95% min. 90% min. 10% Max1 45% min. 45% min. IM-19.0 A 85% min. 80% min. 10% Max1 45% min. 45% min. IM-19.0 D 95% min. 90% min. 10% Max1 45% min. 45% min. IM-19.0 E 95% min. 90% min. 10% Max1 45% min. 45% min. BM-25.0 A 80% min. 75% min. 10% Max1 45% min. 45% min. BM-25.0 D 80% min. 75% min. 10% Max1 45% min. 45% min percent measured at 5:1 on maximum to minimum dimension. f. Mineral filler shall conform to the requirements of Section 201. g. Aggregate for asphalt concrete shall be provided in sufficient sizes to produce a uniform mixture. The Contractor shall indicate on the proposed job-mix formula the separate approximate sizes of aggregate to be used. Where segregation or nonuniformity is evident in the finished pavement, the Engineer reserves the right to require the Contractor to discontinue the use of crusher run or aggregate blends and to furnish separate sizes of open graded aggregate material. h. An antistripping additive shall be used in all asphalt mixes. It may be hydrated lime or an approved chemical additive from the Department s approved list found in the Materials Division s Manual of Instructions, or a combination of both. The mixture shall produce a tensile strength ratio (TSR) value not less than 0.80 for the design and production tests. The TSR value shall be determined in accordance with AASHTO T283, including a freeze-thaw cycle, (4 inch specimens compacted with Marshall hammer or 3.5 x 6 inch specimens when compacted with a gyratory), except that the 16 hour curing time requirement and 72 to 96 hour storage period will be waived. Design tests shall use the same page 6 Appendix B VDOT and Platinum Performance Partners, LLC

291 Materials Specifications materials that are to be used in the production mix and shall be conducted in a laboratory approved by the Department. When Warm Mix Asphalt (WMA) additive or process, as described in (i) of the Specifications, is used in lieu of Hot Mix Asphalt (HMA) in the production of asphalt concrete, the minimum TSR requirement shall be 0.80 for the design and production tests. When a chemical additive is used, it shall be added to the asphalt cement prior to introduction into the mix. Any chemical additive or particular concentration of chemical additive found to be harmful to the asphalt material or which changes the viscosity of the original asphalt cement more than 400 poises or the penetration more than -4 or +10 shall be changed to obtain compliance with these values. i. Hydrated lime shall conform to the requirements of ASTM C977. Hydrated lime shall be added at a rate of not less than 1 percent by weight of the total dry aggregate. A separate bin or tank and feeder system shall be provided to store and accurately proportion the lime into the aggregate in either dry or slurry form. The lime and aggregate shall be mixed by pugmill or other approved means to achieve a uniform lime coating of the aggregate prior to entering the drier. In the event lime is added in dry form, the aggregate shall contain at least 3 percent free moisture. The stockpiling of lime treated aggregate will not be permitted. The feeder system shall be controlled by a proportioning device, which shall be accurate to within ± 10 percent of the specified amount. The proportioning device shall have a convenient and accurate means of calibration. A flow indicator or sensor shall be provided with the proportioning device and interlocked with the plant controls, aggregate feed or weigh system, such that production of the mixture will be maintained and, if there is a stoppage of the lime feed, interrupted. The method of introducing and mixing the lime and aggregate shall be subject to approval by the Engineer prior to beginning production. j. Reclaimed Asphalt Pavement (RAP) material may be used as a component material of asphalt mixtures in conformance with the following: 1. Asphalt surface, intermediate, and base mixtures containing RAP should use the performance grade (PG) of asphalt cement as indicated in Table II-14, however, the choice of PG to use in the mix shall be the responsibility of the Contractor in order to meet the requirements of Section The final asphalt mixture shall conform to the requirements for the type specified. 3. During the production process, RAP material shall not be allowed to contact open flame. 4. RAP material shall be handled, hauled and stored in a manner that will minimize contamination. Further, the material shall be stockpiled and used in such manner that VDOT and Platinum Performance Partners, LLC Appendix B page 7

292 Materials Specifications variable asphalt contents and asphalt penetration values will not adversely affect the consistency of the mixture. 5. RAP shall be processed in such a manner as to ensure that the maximum top size introduced into the mix shall be 2 inches. The Engineer may require smaller sized particles be introduced into the mix if the reclaimed particles are not broken down or uniformly distributed throughout the mixture during heating and mixing. k. Warm Mix Asphalt (WMA) additives or processes shall be approved by the Department prior to use. Approved materials and processes shall be obtained from the Department s approved list which is included in the Materials Division s Manual of Instructions Job-Mix Formula The Contractor shall submit for the Engineer s approval a job-mix formula for each mixture to be supplied. The job-mix formula shall be within the design range specified. The job-mix formula shall establish a single percentage of aggregate passing each required sieve, a single percentage of asphalt material to be added to the aggregate, a temperature at which the mixture is to be produced, and a temperature at which the mixture is to be compacted for SUPERPAVE testing in accordance with the requirements of AASHTO R35. Each approved job-mix formula shall remain in effect, provided the results of tests performed on material currently being produced consistently comply with the requirements of the job-mix formula for grading, asphalt content, temperature, and SUPERPAVE compaction results and the requirements of Section 315. a. SUPERPAVE mixes shall be designed and controlled in accordance with the requirements of AASHTO R35 and as specified herein. The Contractor shall have available all of the equipment outlined in AASHTO T312 (section 4-6) and a Department-certified Asphalt Mix Design Technician. The SUPERPAVE mixture shall be compacted in a gyratory compactor with an internal angle of degrees. The internal angle shall be measured and calibrated using a cold (non-mix) device. The SUPERPAVE Gyratory Compactor (SGC) shall be one from the Department s approved list found in the Materials Division s Manual of Instructions The SUPERPAVE mixes shall conform to the requirements of Table II-13 and Table II-14. Section of AASHTO R30 shall be modified such that the compaction temperature is as specified in (d) 6 herein. The mixture shall be designed and compacted at the N design gyrations specified in Table II-14. The N Max. requirement shall be verified as part of the design process by compacting a minimum of two specimens at the design asphalt content. b. In conjunction with the submittal of a job-mix formula, the Contractor shall submit complete SUPERPAVE design test data, ignition furnace calibration data in accordance with VTM-102 page 8 Appendix B VDOT and Platinum Performance Partners, LLC

293 Materials Specifications prepared by an approved testing laboratory, and viscosity data or supplier temperature recommendations for the asphalt cement if different from (d) 6 herein. c. Three trial blends for gradation shall be run at one asphalt content. Mix Type Table II 13. Asphalt Concrete Mixtures: Design Range 1 Percentage by Weight Passing Square Mesh Sieves 2 in 1 1/2 in 1 in 3/4 in 1/2 in 3/8 in No. 4 No. 8 No. 30 No. 50 No. 200 SM-9.0 A,D,E max SM-9.5 A,D,E max SM-12.5 A,D,E max IM-19.0 A,D,E max BM max C (Curb Mix) SM = Surface Mix; IM = Intermediate Mix; BM = Base Mix; C = Curb Mixture 2 A production tolerance of 1% will be applied to this sieve, regardless of the number of tests in the lot. VTM (%) Production VFA (%) Table II-14. Mix Design Criteria VFA (%) Production Min. VMA Fines/Asph alt Ratio Density (%) at No. of Gyrations N N N Mix Type (Note 1) Design (Note 2) (%) (Note 3) Design Initial Max N Initial SM-9.0 A Notes 1,2, SM-9.0 D Notes 1,2, SM-9.0 E Notes 1,2, SM-9.5 A Notes 1,2, SM-9.5 D Notes 1,2, SM-9.5 E Notes 1,2, SM-12.5 A Notes 1,2, SM-12.5 D Notes 1,2, SM-12.5 E Notes 1,2, IM-19.0 A Notes 1,2, IM-19.0 D Notes 1,2, IM-19.0 E Notes 1,2, BM-25.0 A Notes 2, 3, BM-25.0 D Notes 2, 3, SM = Surface Mix; IM = Intermediate Mixture; BM = Base Mixture VDOT and Platinum Performance Partners, LLC Appendix B page 9

294 Materials Specifications Note 1: Asphalt content should be selected at 4.0 % Air Voids. Note 2: During production of an approved job mix, the VFA shall be controlled within these limits. Note 3: Fines-Asphalt Ratio is based on effective asphalt content. Note 4: Base mix shall be designed at 2.5 percent air voids. BM-25.0 A shall have a minimum asphalt content of 4.4 percent, unless otherwise approved by the Engineer. BM-25.0 D shall have a minimum asphalt content of 4.6 percent, unless otherwise approved by the Engineer. d. The SUPERPAVE design test data shall include but not be limited to the following information: 1. Grading data for each aggregate component of 3 trial blends shall be submitted to the Department. The data for the mixture will show percent passing for sieves 2 inch, 1 1/2 inch, 1inch, 3/4 inch, 1/2 inch, 3/8 inch, No. 4, No. 8, No. 16, No. 30, No. 50, No. 100 and No The grading shall be reported to the nearest 1.0 percent except the No. 200 sieve shall be reported to nearest 0.1 percent. 2. The test data shall include, but not be limited to, the percentage of each aggregate component as compared to the total aggregate in the asphalt mixture. The specific gravity and aggregate properties for coarse and fine aggregates defined in Section (b) and (c), including flat and elongated properties, for each aggregate component or for the total aggregates used in the mixture shall be reported. Aggregate properties, except sand equivalent shall be reported for RAP portions of a mixture. The aggregate specific gravity of RAP shall be the effective aggregate specific gravity calculated from the results of tests conducted in accordance with AASHTO T 209 and VTM The aggregate grading in the asphalt mixture shall be determined by igniting or extracting the asphalt from a laboratory prepared sample. The laboratory sample shall be batched on the basis of component percentages as indicated in (d) 2. Herein and at the proposed jobmix asphalt content. The aggregate shall be obtained in accordance with the requirements of VTM-102 or (VTM-36 when approved). Sieves specified in (d) 1. herein shall be reported, beginning with the top size for the mix. 4. The following volumetric properties of the compacted mixture, calculated on the basis of the mixture s maximum specific gravity determined by AASHTO T-209 shall be reported to the Engineer. The mixture must be aged in accordance with AASHTO R-30 and the bulk specific gravity of the specimens determined in accordance with AASHTO T-166, Method A, for each asphalt content tested. Properties shall be determined and reported in accordance with the requirements of AASHTO R35. a) Voids in total mix (VTM) b) Voids in mineral aggregate (VMA) c) Voids filled with Asphalt (VFA) d) Fines/Asphalt ratio (F/A) page 10 Appendix B VDOT and Platinum Performance Partners, LLC

295 Materials Specifications 5. The value of the maximum specific gravity of the asphalt mixture used in (c) 4. herein shall be reported to three decimal places. 6. The mixing and compaction temperature for testing shall be as follows: a) a. For mix designation A, the mix temperature shall be 300 F to 310 F and the compaction temperature shall be 285 F to 290 F. b) b. For mix designation D, the mix temperature shall be 310 F to 320 F and the compaction temperature shall be 295 F to 300 F. c) c. In cases involving PG or modified binders, the temperatures shall be based on documented supplier s recommendations. 7. The field correction factor as determined by subtracting the bulk specific gravity of the aggregate from the effective specific gravity of the aggregate at the design asphalt content. 8. For surface mixes, permeability test data shall be submitted in accordance with VTM-120 using either single point verification or the regression method for each surface mix having a different gradation. If the average if the permeability results from the single point verification method exceeds 150 x 10-5 cm/sec, or if the regression method predicts a permeability exceeding 150 x 10-5 cm/sec at 7.5% voids, the Contractor shall redesign the mixture to produce a permeability number less than 150 x 10-5 cm/sec. e. (e) The SUPERPAVE design test data shall be plotted on graphs as described in AASHTO R35 and show that the proposed job-mix formula conforms to the requirements of the mix type. f. (f) A determination will be made that any asphalt concrete mixture being produced conforms to the job-mix formula approved by the Department. The Department and Contractor will test the mixture using samples removed from production. The following tests will be run to determine the properties listed: Property Test Asphalt content VTM-102, (VTM-36 when approved) Gradation AASHTO T-30 SUPERPAVE properties AASHTO R35 Asphalt cement material AASHTO T316 or T-201 VDOT and Platinum Performance Partners, LLC Appendix B page 11

296 Materials Specifications For Warm Mix Asphalt (WMA), SUPERPAVE properties will be determined by the Department and Contractor once the WMA has been allowed to cool to 100 degrees F or less and reheated based on the mix designation in Section (d) 6 of the Specifications. The Department will perform rut testing in accordance with the procedures detailed in VTM-110. If the results of the rut testing do not conform to the following requirements, the Engineer reserves the right to require adjustments to the job-mix formula: Mix Designation Maximum Rut Depth, mm A 7.0 D 5.5 E, (M), (S) 3.5 After calibration of the gyratory compactor is completed, adjustments to the job-mix formula may be required by the Engineer. In the event the Department determines that the mixture being produced does not conform to the approved job-mix formula and volumetric properties specified in Table II-14 based on the Department s or Contractor s test results, the Contractor shall immediately make corrections to bring the mixture into conformance with the approved job-mix formula or cease paving with that mixture. Subsequent paving operations, using either a revised or other job-mix formula which has not been verified as described herein, shall be limited to a test run of 100 to 300 tons of mixture if such material is to be placed in Department project work. No further paving for the Department using that specific mixture shall occur until the acceptability of the mixture being produced has been verified using the 100 to 300 ton constraint. Table II-14A. Recommended Performance Grade of Asphalt Cement Percentage of Reclaimed Asphalt Pavement (RAP) in Mix Mix Type % RAP % < % RAP 30% 20.0% < %RAP 35% SM-9.0A, SM-9.5A, SM-12.5A PG PG SM-9.0D, SM-9.5D, SM-12.5D PG PG IM-19.0A PG PG IM-19.0D PG PG BM-25.0A PG PG BM-25.0D PG PG Based on rut testing performed by the Department and/ or field performance of the job-mix, the Engineer reserves the right to require adjustments to the job-mix formula. page 12 Appendix B VDOT and Platinum Performance Partners, LLC

297 Materials Specifications Asphalt Concrete Mixtures Asphalt concrete mixtures shall conform to the requirements of Table II-14 and the following: a) Types SM-9.0A, SM-9.0D, SM-9.0E, SM-9.5A, SM-9.5D, SM-9.5E, SM-12.5A, SM-12.5D, and SM- 12.5E asphalt concrete shall consist of crushed stone, crushed slag, or crushed gravel and fine aggregate, slag or stone screenings or a combination thereof combined with asphalt cement. NOTE: For all surface mixes, except where otherwise noted, no more than 5 percent of the aggregate retained on the No. 4 sieve and no more than 20 percent of the total aggregate may be polish susceptible. At the discretion of the Engineer, a SM-9.5AL or SM-12.5AL may be specified and polish susceptible aggregates may be used (without percentage limits). b) Types IM-19.0A and IM-19.0D and Im-19.0E asphalt concrete shall consist of crushed stone, crushed slag, or crushed gravel and fine aggregate, slag or stone screenings or a combination thereof combined with asphalt cement. NOTE: At the discretion of the Engineer, an intermediate mix may be designated as either a SM- 19.0A or SM-19.0D. When designated as such, no more than 5 percent of the aggregate retained on the No. 4 sieve may be polish susceptible. All material passing the No. 4 sieve may be polish susceptible. c) Types BM-25.0A and BM-25.0D asphalt concrete shall consist of crushed stone, crushed slag, or crushed gravel and fine aggregate, slag or stone screenings or a combination thereof combined with asphalt cement. d) Type C (Curb Mix) asphalt concrete shall consist of a blend of No. 78 or No. 8 crushed aggregate, No. 10 crushed aggregate, fine aggregate, mineral filler and a stabilizing additive from the Department s approved list found in the Materials Division s Manual of Instructions combined with percent of PG This mix does not require a volumetric mix design or volumetric testing under the Superpave system. e) Type SM-9.5, SM-12.5, IM-19.0, BM-25.0 asphalt concrete may be designated E (polymer modified), or stabilized (S) Asphalt mixtures with the E designation may not be stabilized. (1) Type E asphalt mixtures shall consist of mixes incorporating a neat asphalt material with polymer modification meeting the requirements of a PG and have a rolling thin film oven test residue elastic recovery at 77ºF of a minimum 70 percent when tested in accordance with ASTM D 6084 procedure A. E designated mixtures shall not contain more than 15 percent reclaimed asphalt pavement (RAP) material. (2) Type (S) asphalt mixtures shall consist of mixes incorporating a stabilizing additive from the Department s approved list found in the Materials Division s Manual of Instructions. These mixes shall be designated with an (S) following the standard mix designation. The minimum required additive shall be as specified on the Department s approved list found in the Materials Division s Manual of Instructions. VDOT and Platinum Performance Partners, LLC Appendix B page 13

298 Materials Specifications (3) Type L asphalt mixtures will be allowed to contain a 100 percent polishing coarse and fine aggregate. These mixes shall be designated with an L following the standard mix designation Testing The Contractor shall provide the quality control and assurance necessary for the Department to determine conformance with the required grading, asphalt content and temperature properties for asphalt concrete. The Contractor shall have a Department- certified Asphalt Mix Design Technician for designing and adjusting mixes as necessary. The Asphalt Mix Design Technician or certified Asphalt Plant Technician may perform testing of asphalt mixes. The Asphalt Mix Design Technician shall be responsible for reviewing and approving the results of all testing. The Asphalt Mix Design Technician shall be available and have direct communication with the plant for making necessary adjustments in the asphalt concrete mixes at the mixing plant. The Asphalt Mix Design Technician and Asphalt Plant Technician shall be capable of conducting any tests necessary to put the plant into operation; however, it shall be the responsibility of the Asphalt Mix Design Technician to produce a mixture within the requirements of these specifications. The Department will award certification. The Contractor shall maintain all records and test results associated with the material production and shall maintain appropriate current quality control charts. All test results and control charts shall be available for review by the Engineer. The Contractor shall execute a quality control plan of process inspections and tests, including the determination of SUPERPAVE properties. The results of the SUPERPAVE tests shall be used, along with the results of other quality control efforts, to control the quality of the mixture being produced. The Contractor shall perform at least one field SUPERPAVE test per day per mix or per 1000 tons per mix if more than 1000 tons of a mix is produced per day. Aging as described in AASHTO R30 shall not be performed. In the event less than 300 tons of asphalt mixture is produced under a single job-mix formula in a day, field SUPERPAVE testing will not be required. This tonnage shall be added to subsequent production. When the accumulated tonnage exceeds 300 tons, minimum testing frequency shall apply. Field SUPERPAVE test results shall be plotted and displayed in control chart form in the plant immediately following the completion of each individual test. The tests shall determine asphalt content, VTM, VMA, VFA and F/A in percent to the nearest 0.1 percent. The Department will conduct on-site inspections so the Contractor s Asphalt Mix Design Technician can demonstrate knowledge of the SUPERPAVE mix design and production requirements on Department-supplied mixture. Aggregate specific gravity and aggregate property tests shall be conducted by a VDOT certified Aggregate Properties Technician or Asphalt Mix Design Technician on each aggregate component (including RAP) or total aggregate mixture once at design and once prior to beginning production in each page 14 Appendix B VDOT and Platinum Performance Partners, LLC

299 Materials Specifications calendar year. Sand Equivalent shall not be determined on RAP. In addition, for each 50,000 tons of each aggregate size used at each plant, aggregate specific gravity and aggregate property test shall be reported on each aggregate component or the total aggregate mixture. Otherwise, if the total blend (cold feed) is used to determine aggregate specific gravity and aggregate properties, these tests shall be run for each 50,000 tons of the total blend. Field Superpave tests shall be performed to N design gyrations as specified in Table II-14. At the Engineer s discretion, the N max requirement may be verified Tests The Department may sample materials entering into the composition of the asphalt concrete, the mixture or the completed pavement. The Contractor shall cooperate with the Engineer in obtaining these samples. When samples are obtained from the pavement, the resulting voids shall be filled and refinished by the Contractor without additional compensation. Abson recovery samples shall be PG graded according to the requirements of AASHTO M Samples meeting the required grades specified in Section of the Specifications shall be acceptable. When the Department performs PG grading on the asphalt in a Contractor s liquid asphalt storage tank, the Engineer will notify the asphalt concrete producer and binder supplier if tests indicate that the binder properties of the asphalt material differ from those of the approved job-mix. The asphalt concrete producer and binder supplier shall determine corrective action with the approval of the Engineer Plant Inspections The preparation of asphalt concrete mixtures will be accepted under a quality assurance plan. The Contractor shall provide a laboratory as specified in Section In addition, the Contractor shall have all laboratory scales and gyratory compactors calibrated once a year by an independent source. The Contractor shall maintain the calibration records for 3 years Acceptance Acceptance will be made under the Department s quality assurance program which includes the testing of production samples by the Contractor and of monitor samples by the Department. Sampling and testing for the determination of grading, asphalt cement content and temperature shall be performed by the Contractor, and the Department will perform independent monitor checks at a laboratory of its VDOT and Platinum Performance Partners, LLC Appendix B page 15

300 Materials Specifications discretion. The Contractor shall provide copies of such test results to the Department on forms furnished by the Department. Where the Contractor s test results indicate that the mixture conforms to the gradation, asphalt cement content and mix temperature requirements of the Specifications, the mixture will be acceptable for these properties; however, nothing herein shall be construed as waiving the requirements of Sections , and , and 315 or relieving the Contractor of the obligation to furnish and install a finished functional product which conforms to the requirements of the Contract. In the event a statistical comparative analysis of the Contractor s test results and the Department s monitor tests indicate a statistically significant difference in the results and either of the results indicate that the material does not conform to the grading and asphalt cement content requirements of the Specifications, an investigation will be made to determine the reason for the difference. In the event it is determined from the investigation that the material does not conform to the requirements of the Contract, price adjustments will be made in accordance with the requirements of Section Acceptance for gradation and asphalt cement content will be based on the mean of results of eight tests performed on samples taken in a stratified random manner from each 4,000 ton lot (8,000 ton lots may be used when the normal daily production of the source from which the material is being obtained is in excess of 4,000 tons). Unless otherwise approved by the Engineer, samples shall be obtained from the approximate center of the truckload of material. Any statistically acceptable method of randomization may be used to determine when to take the stratified random sample; however, the Department shall be advised of the method to be used prior to beginning production. A lot will be considered to be acceptable for gradation and asphalt content if the mean of the test results obtained is within the tolerance allowed from the job-mix formula, as shown in Table II-15. The temperature of the mixture at the plant shall be controlled to provide load-to-load uniformity during changing weather conditions and surface temperatures. The maximum temperature of mix designations A and D, and base mixes, shall not exceed 350 F, unless otherwise directed by the Engineer. The maximum temperature as recommended by the supplier shall not be exceeded for a mix designated E, (M), or (S). In the event the job-mix formula is modified within a lot, the mean test results of the samples taken will be compared to the applicable process tolerance shown in Table II-15. Asphalt content will be measured as extractable asphalt or weigh after ignition. Field SUPERPAVE tests will be performed by the Department in accordance with the requirements of AASHTO R35 during the production of the approved job-mixes designed by the SUPERPAVE method. Aging, as described in AASHTO R30, shall not be performed. Should any field SUPERPAVE test fail with regard to the limits specified in Table II-14, the Department may require that production be stopped until necessary corrective action is taken by the Contractor. The Engineer will investigate and determine the acceptability of material placed and represented by failing field SUPERPAVE test results. page 16 Appendix B VDOT and Platinum Performance Partners, LLC

301 Materials Specifications Should visual examination by the Engineer reveal that the material in any load or portion of the paved roadway is obviously contaminated or segregated, that load or portion of the paved roadway will be rejected without additional sampling or testing of the lot. In the event it is necessary to determine the gradation or asphalt content of the material in any load or portion of the paved roadway, samples will be taken, tested, and the results compared to the requirements of the approved job-mix formula. The results obtained in the testing will apply only to the material in question. No. Tests Table II-15. Process Tolerance Tolerance on Each Laboratory Sieve and Asphalt Content: Percent Plus and Minus Top Size 1 1 ½ in 1 in 3/4 in 1/2 in 3/8 in No. 4 No. 8 No. 30 No. 50 No. 200 A.C Defined as the sieve that has 100% passing as defined in Table II Adjustment System In the event a lot of material does not conform to the acceptance requirements of Section , adjustment points will be determined as follows: Adjustment Points for Each 1% the Gradation is Outside the Process Tolerance Permitted in Table II-15 Applied in 0.1% Sieve Size Increments 1 1/2 in 1 1 in 1 3/4 in 1 1/2 in 1 3/8 in 1 No. 4 1 No. 8 1 No No No VDOT and Platinum Performance Partners, LLC Appendix B page 17

302 Materials Specifications One adjustment will be applied for each 0.1 percent that the material is out of the process tolerance for asphalt content. In the event the total adjustment for a lot is greater than 25 points, the failing material shall be removed from the road. In the event the total adjustment is 25 points or less and the Contractor does not elect to remove and replace the material, the unit price for the material will be reduced 1 percent of the unit price bid for each adjustment point. The adjustment will be applied to the tonnage represented by the sample or samples. In the event adjustment points are applied against 2 successive lots, plant adjustment shall be made prior to continuing production. The Contractor shall control the variability of his product in order to furnish a uniform mix. When the quantity of any one type material furnished a project exceeds 4000 tons, the variability of the total quantity furnished will be determined on the basis of the standard deviation for each sieve size and the asphalt content. In the event the standard deviation is within the ranges shown in Table II-16, the unit bid price for the material will be adjusted as indicated herein. Adjustments for standard deviation computations will not be made on more than two job mixes for the same type material. Table II-16. Standard Deviation A separate standard deviation will be determined by the Department for each calendar year s production of each mix type produced by a plant. The unit bid price will be reduced by 0.5 percent for each adjustment point applied for standard deviation. The Engineer will determine the disposition of material having standard deviations larger than those shown in Table II Referee System a) In the event the test results obtained from one of the eight samples taken to evaluate a particular lot appear to be questionable, the Contractor may request in writing that the results page 18 Appendix B VDOT and Platinum Performance Partners, LLC

303 Materials Specifications of the questionable sample be disregarded; whereupon, the Contractor shall have either an AASHTO accredited Labor Department lab perform tests on five additional samples taken from randomly selected locations in the roadway where the lot was placed. In the event the Engineer determines that one of the four tests results appears to be questionable, the Department will perform tests on five additional samples taken from randomly selected locations in the roadway where the lot was placed. The test results of the seven original, i.e. unquestioned samples will be averaged with the test results of the five road samples and the mean of the test values obtained for the twelve samples will be compared to the requirements for the mean of twelve tests as shown in Table II-15. b) In the event the Contractor questions the mean of the eight original test results obtained for a particular lot, the Contractor may request in writing approval to have either an AASHTO accredited labor Department lab perform additional testing of that lot. In the event the Engineer determines that the mean of the eight original test results are questionable, the Department will perform additional testing of that lot. The test results of the original eight samples will be averaged with the test results of the four additional samples taken from randomly selected locations in the roadway where the lot was placed and the mean of test values obtained for the eight samples will be compared to the requirements for the mean result of eight tests as shown in Table II-15. If the Contractor requests additional tests, as described in (a) or (b) herein, the Contractor shall sample and have either an AASHTO-accredited labor Department lab test the material in accordance with Department- approved procedures. The Engineer reserves the right to observe the sampling and testing. In the event the mean of the test values obtained for the twelve samples conforms to the requirements for the mean results of twelve tests, the material will be considered acceptable. In the event the mean of the test values obtained for the twelve samples does not conform to the requirements for the mean result of eight tests, the lot will be adjusted in accordance with the adjustment rate specified in Section Samples of the size shown herein shall be saw cut by the Contractor for testing without the use of liquids. VDOT and Platinum Performance Partners, LLC Appendix B page 19

304 Materials Specifications Handling and Storage of Aggregates Aggregates shall be handled, hauled and stored in a manner which will minimize segregation and avoid contamination. Aggregates shall be stockpiled in the vicinity of the plant and on ground that is denuded of vegetation, hard, well drained or otherwise prepared to protect the aggregate from contamination. Placing aggregate directly from the crusher bins into the cold feed may be permitted, provided the material is consistent in gradation. When different size aggregates are stockpiled, the stockpiles shall be separated to prevent commingling of the aggregates Asphalt Concrete Mixing Plant a) Certification for Plant Operation and Sampling: There shall be a certified Asphalt Plant Technician for sampling material at the plant. b) Plant Scales: Scales shall be approved in accordance with the requirements of Section c) Drier: The plant shall include a drier(s) that continuously agitates the aggregate during the heating and drying process. The aggregate shall be dried to a point at which the moisture content of the completed mixture does not exceed 1 percent as determined from samples taken at the point of discharge from the mixing operation. d) Feeder for Drier: The plant shall be equipped with accurate mechanical means for uniformly feeding the aggregate into the drier so that uniform production and uniform temperature will be obtained. Where different size aggregates are required to meet grading specifications, they must be proportioned by feeding into the cold elevator through a multiple compartment feeder bin, one bin for each size used, equipped with positive action gates that can be securely locked to maintain desired proportioning. e) Bins: When bins are used, adequate and convenient facilities shall be provided to make possible the sampling of representative aggregate material for each bin. Each compartment shall be provided with an overflow pipe of such size and at such location to prevent contamination of the aggregate in adjacent compartments and shall be provided with individual outlet gates which, when closed, will allow no leakage. f) Thermometric Equipment: The plant shall be equipped with a thermometric instrument so placed at the discharge chute of the drier as to register automatically or indicate the temperature of the heated aggregate or the completed mix if the drier drum mixing plant is used. A thermometric device shall be fixed in the asphalt feed line at a suitable location near the charging valve at the mixer unit. Thermometric devices shall be maintained in good working condition and shall be subject to checking against the laboratory thermometer. Any instruments that do not operate or register properly shall be removed and repaired or replaced. g) Pollution Control: Pollution control shall conform to the requirements of Section of the Specifications. page 20 Appendix B VDOT and Platinum Performance Partners, LLC

305 Materials Specifications h) Equipment for Preparation of Asphalt Material: Tanks for the storage of asphalt material shall be equipped with a heating system capable of heating and holding the material at the required temperatures. A separate storage tank or a storage tank having separate compartments shall be available for each grade of asphalt cement being used. The heating system shall be designed to heat the contents of the tank by means of steam, electricity or other approved means so that no flame is in contact with the heating surface of the tank. The circulating system for the asphalt material shall be designed to assure proper and continuous circulation during the operating period and to minimize oxidation. All pipelines shall be steam jacketed or insulated to prevent undue loss of heat. Storage facilities for asphalt material shall be sufficient for at least one day s operation or an equivalent means of supply shall be provided which will insure continuous operation. Provisions shall be made for measuring and sampling storage tanks. When asphalt material is proportioned by volume, the temperature of the asphalt material in storage shall be uniformly maintained (±20º F) during operation of the plant by means of an automatic temperature control device. A sampling valve shall be provided for sampling of each asphalt storage tank used in production of the mix. If there are multiple storage tanks, then a dedicated valve for each tank shall be provided. i) Asphalt Control: Asphalt material shall be accurately proportioned by volume or weight. When volumetric methods are used, measurements shall be made by means of meters or pumps, calibrated for accuracy. The section of the asphalt line between the charging valve and the spray bar shall be provided with an outlet valve for checking the meter. When proportioned by weight, the asphalt material shall be weighed on approved scales. Dial scales shall have a capacity of not more than 15 percent of the capacity of the mixer. The value of the minimum graduation shall not be greater than 2 pounds. Except when drier-drum mixing plant is used, the asphalt material bucket, its valves and spray bar shall be steam jacketed or heated by other approved means. The bucket shall have a capacity of at least 115 percent of the weight of the asphalt material required in any mixture and shall be supported by fulcrums. The asphalt shall be delivered to the mixer in multiple uniform streams for the full width of the mixer. j) Proportioning Aggregates: Mineral filler and any bag house fines the Contractor uses shall be metered or introduced by means of an approved device for uniform proportioning by weight or by volume. The weigh hopper shall be of sufficient size to hold the maximum required weight of aggregate for one batch without hand raking or running over. Sufficient clearance between the weigh hopper and supporting devices shall be provided to prevent accumulation of foreign materials. VDOT and Platinum Performance Partners, LLC Appendix B page 21

306 Materials Specifications The discharge gate of the weigh hopper shall be situated in such a manner that the aggregates will not segregate when dumped into the mixer. Gates on the bins and weigh hopper shall be constructed to prevent leakage when closed. k) Drum Mixer: The aggregate shall be proportioned by a positive weight control at the cold aggregate feed by use of a belt scale, which will automatically regulate the supply of material being fed and permit instant correction of variations in load. The cold feed flow shall be automatically coupled with the asphalt flow to maintain the required proportions. l) Batch Mixer: The batch mixer shall be of a twin pugmill or other approved type, steam jacketed or heated by other approved means and capable of producing uniform mixtures within the specified tolerances. It shall be equipped with a sufficient number of paddles or blades, operated at such speeds as to produce a properly and uniformly mixed batch. The number and arrangement of the mixer paddles shall be subject to the approval of the Engineer. Worn or defective blades shall not be used in mixing operations. The mixer shall be provided with an approved time lock which will lock the discharge gate after the aggregates and asphalt have been placed in mixer and will not release the gate until the specified time has elapsed Batch type mixing plants used to produce asphalt concrete shall be equipped with approved automatic proportioning devices. Such devices shall include equipment for accurately proportioning batches of the various components of the mixture by weight or volume in the proper sequence and for controlling the sequence and timing of mixing operations. The automated system shall be designed to interrupt and stop the batching operation at any time batch quantities are not satisfied for each of the materials. A means shall be provided for observing the weight of each material during the batching operation. The aggregate may be proportioned by cold feed controls in lieu of plant screens provided the cold aggregate feed conforms to the requirements specified in (j) herein. Should the automatic proportioning devices become inoperative, the plant may be allowed to batch and mix asphalt materials for a period of not more than 48 hours from the time the breakdown occurs provided alternate proportioning facilities are approved by the Engineer. Written permission of the Engineer will be required for operation without automatic proportioning facilities for periods longer than 48 hours. m) Continuous Mixing Plant: A continuous mixing plant shall include a means for accurately proportioning each size of aggregate either by weighing or volumetric measurement. When gradation control is by volume, the unit shall include a feeder mounted under the compartment bins. Each bin shall have an accurately controlled individual gate to form an orifice for volumetrically measuring the material drawn from each respective bin compartment. The orifice shall be rectangular, with one dimension adjustable by positive mechanical means and shall be provided with a lock. Indicators shall be provided to show the individual gate opening in inches. The plant shall be equipped with a satisfactory revolution counter. page 22 Appendix B VDOT and Platinum Performance Partners, LLC

307 Materials Specifications The plant shall include a means for calibrating gate openings by weight. The materials fed out of the bins through individual orifices shall be bypassed to a suitable test box, with each component material confined in a separate section. The plant shall be equipped to conveniently handle test samples weighing up to 200 pounds per bin and accurate platform scales shall be provided for this purpose. Positive interlocking control shall be provided between the flow of aggregate from the bins and the flow of asphalt material from the meter or other proportioning device. This shall be accomplished by approved interlocking devices or other approved positive means. Accurate control of the asphalt material shall be obtained by weighing, metering or volumetric measurement. The aggregate may be proportioned by cold feed controls in lieu of plant screens provided the cold aggregate feed conforming to the requirements specified in (j) herein. The plant shall include a continuous mixer of an approved type, which is steam jacketed or heated by other approved means. The paddles shall be of any adjustable type for angular position on the shafts and reversible to retard the flow of the mixture. Interlock cutoff circuits shall be included to interrupt and to stop the proportioning and mixing operations when the aggregate level in the plant or the asphalt material in storage falls below that necessary to produce the specified mixture. n) Trucks, Truck Scales, and Automatic Printer System: These shall conform to the requirements of Section Preparation of Mixture The asphalt and aggregate shall be introduced into the mixer at a temperature that will produce a mixture within the requirements of the job-mix formula. After the required amounts of aggregate and asphalt material have been introduced into the mixer, the materials shall be mixed until a uniform coating of asphalt and a thorough distribution of the aggregate throughout the mixture is secured within the requirements of the Ross Count procedure described in AASHTO T195. Wet mixing time, based on the procedures of AASHTO T195, shall be determined by the Contractor at the beginning of production and approved by the Engineer for each individual plant or mixer and for each type of aggregate used; however, in no case shall the wet mixing time be less than 20 seconds. The wet mixing time is the interval of time between the start of introduction of the asphalt material into the mixer and the opening of the discharge gate. A wet mixing time which will result in fully coating a minimum of 95 percent of the coarse particles, based on the average of the 3 samples and provided that none of the 3 samples result in fully coating less than 92 percent of the coarse particles, shall be the minimum wet mixing time requirement. VDOT and Platinum Performance Partners, LLC Appendix B page 23

308 Materials Specifications A dry mixing time of up to 15 seconds may be required by the Engineer to accomplish the degree of aggregate distribution necessary to obtain complete and uniform coating of the aggregate with asphalt Storage System In the event the Contractor elects to use a storage system, the system shall be capable of conveying the mix from the plant to the storage bins and storing the mix without a loss in temperature, segregation or oxidation of the mix. Storage time shall be limited by the ability of the bins to maintain the mix within the quality requirements specified herein with a maximum time limit not to exceed 10 days. Material may be stored in bins for no more than 24 hours without an approved heating system. The conveyor system may be a continuous or skip bucket type. Continuous type conveyors shall be enclosed so that the mix temperature is maintained. The storage bins shall be designed in a manner to prevent segregation of the mix during discharge from the conveyor into the bins and shall be equipped with discharge gates that will not cause segregation of the mix while the mix is loaded into the trucks. Approval for the use of storage bins may be withdrawn by the Engineer in the event there is an excessive amount of heat loss, segregation or oxidation of the mix Initial Production a) Warm Mix Asphalt (WMA): At the start of production, the Contractor shall place no more than 500 tons or up to one day s production as directed by the Engineer at an approved site, which may be the project site, so the Engineer can examine the process control of the mixing plant, the Contractor s placement procedures, surface appearance of the mix, compaction patterns of the Contractor s roller(s), and correlation of the nuclear density device. b) Hot Mix Asphalt (HMA): At the start of production of a mix not previously used on a state roadway, the Contractor shall place 100 to 300 tons or up to one day s production as directed by the Engineer at an approved site, which may be the project site, so the Engineer can examine the process control of the mixing plant, the Contractor s placement procedures, surface appearance of the mix, compaction patterns of the Contractor s roller(s), and correlation of the nuclear density device. The material shall be placed at the specified application rate and will be paid for at the contract unit price for the specified mix type. The Engineer will determine the disposition of material that was not successfully produced and/or placed due to negligence in planning, production, or placement by the Contractor. page 24 Appendix B VDOT and Platinum Performance Partners, LLC

309 Materials Specifications Section 248 Stone Matrix Asphalt Concrete (Feb. 9, 2010) Description These specifications cover the materials used to produce stone matrix asphalt (SMA) concrete pavement. SMA shall be in accordance to this specifications and Section 211. SMA consists of a combination of coarse aggregate, fine aggregate, mineral filler, fiber additives, and liquid asphalt binder mechanically mixed in a plant to produce a stable gap-graded asphalt concrete paving mixture Materials a) Coarse Aggregate: Coarse aggregate shall conform to the following requirements when tested in accordance with the specified tests Except for the determination of flat and elongated particles (Section (a)2 of the Specifications), the aggregate properties specified are for each stockpile of coarse aggregate material designated on the job mix form (Form No. TL-127). The material contained in each stockpile shall meet the minimum or maximum criteria specified. For flat and elongated particles, these values are based on the mathematical blend of the coarse aggregate material designated on the job mix form (TL-127). During production, these values are based on the SMA material sampled during the acceptance process (QC testing). The use of slag will not be permitted. At the discretion of the Engineer, mixes containing Reclaimed Asphalt Pavement (RAP) may be tested by VDOT for aggregate breakdown during lab compaction in accordance with VTM-99. If the percent of the total mix passing the No. 4 sieve increases by more thant10 percent after being compacted to N design then the RAP component shall be changed or the authorization to use the mix will be discontinued. VDOT and Platinum Performance Partners, LLC Appendix B page 25

310 Materials Specifications b) Fine Aggregate: Virgin fine aggregate shall consist of a blend of 100 percent crushed aggregate. If RAP is being used as a component in SMA hen the portion of the final SMA blend passing the No. 8 sieve shall have a minimum Fine Aggregate Angularity value of 45 percent as determined in accordance with AASHTO T3049 (Method A).The magnesium sulfate soundness loss in 5 cycles shall not exceed 20 percent. In addition, the liquid limit shall not exceed 25 as determined in accordance with AASHTO T89. c) Asphalt Binder: Asphalt binders shall be performance-graded binder PG or polymer modified binder PG conforming to the requirements of the mix designation (E) so designated by the Department. The supplier shall certify to the Department that the binder complies with the requirements for all properties of that grade as specified in AASHTO M320 Table 1 for performance-graded asphalt binder. This certification shall be based on testing performed on samples of binder provided to the Contractor for incorporation into the mixture. Certification based on testing performed on laboratory-produced binders will not be acceptable. The Contractor shall submit to the Engineer for Department review the source, formulation, and PG grading of the binder at least 15 days prior to the production of the SMA mixture. During mixture production, testing to determine the binder PG grade will be performed by the Department on samples taken from storage at the hot-mix asphalt plant as directed by the Engineer. The Contractor shall be responsible for obtaining the sample of binder when requested. In the event it is determined that the binder does not comply with the requirements of the specified PG grade, production shall be stopped until further testing indicates that the problem has been corrected. d) Mineral Filler: Mineral filler shall consist of finely divided mineral matter such as rock or limestone dust or other suitable material. Hydrated lime and fly ash will not be allowed. Up to two mineral fillers may be blended to comply with the mineral filler requirements. Mineral filler shall conform to the requirements of Section 201 with the following modifications. The mineral filler or mineral filler blend used in surface and intermediate SMA shall have a minimum of 55 percent passing the No. 200 sieve. At the time of use, it shall be sufficiently dry to flow freely and be essentially free from agglomerations. e) Fiber Additive: Cellulose fiber in either loose or pelletized form shall be used. The minimum dosage rate for cellulose is 0.3 percent by weight of the total mixture. During production, the Department may require the percentage of fiber additive to be increased if visual inspection or draindown testing on plant-produced material indicates that draindown in excess of 0.3 percent by weight of the mixture is occurring as determined in accordance with VTM-100. Allowable tolerances of fiber dosage shall be ±10 percent of the required fiber weight. NOTE: When using pelletized fiber, the dosage rate shall be adjusted to comply with the specified minimum dosage rates for cellulose fiber. Pelletized fiber consists of cellulose fiber and a binder. The specified minimum dosage rates are based on fiber content only. Therefore, the amount of pelletized fiber added shall typically be higher than for loose fiber. page 26 Appendix B VDOT and Platinum Performance Partners, LLC

311 Materials Specifications Fibers will be accepted based on the manufacturer s certification. Table II-23 1 Method A: Alpine Sieve Analysis. Performed using an Alpine Air Jet Sieve (Type 200 LS). A representative 5-gram sample of fiber is sieved for 14 minutes at a controlled vacuum of 22 inches (±3 inches) of water. The portion remaining on the screen is weighed. 2 Method B: Mesh Screen Analysis. This test is performed using standard Nos. 20, 40, 60, 80, 100, and 140 sieves, nylon brushes, and a shaker. A representative 10-gram sample of fiber is sieved, using a shaker and two nylon brushes on each screen. The amount retained on each sieve is weighed and the percentage passing calculated. 3 Ash Content: A representative 2- to 3-gram sample of fiber is placed in a tared crucible and heated between 1100 and 1200 degrees F for not less than 2 hours. The crucible and ash are cooled in a desiccator and reweighed. 4 ph Test: Five grams of fiber is added to 3.5 ounces of distilled water, stirred, and allowed to set for 30 minutes. The ph is determined with a probe calibrated with a ph 7.0 buffer. 5 Oil Absorption Test: Five grams of fiber is accurately weighed and suspended in an excess of mineral spirits for not less than 5 minutes to ensure total saturation. It is then placed in a screen mesh strainer (with a hole size of approximately 0.5 square millimeter), and shaken on a wrist action shaker for 10 minutes (approximately 1¼-inch motion at 20 shakes/minute). The shaken mass is then transferred without touching to a tared container and weighed. Results are reported as the amount (number or times its own weight) the fibers are able to absorb. VDOT and Platinum Performance Partners, LLC Appendix B page 27

312 Materials Specifications 6 Moisture Content: Ten grams of fiber is weighed and placed in a 250 degree F forced air oven for 2 hours. The sample is then reweighed immediately upon removal from the oven. f) RAP: Reclaimed Asphalt Pavement (RAP) material may be used as component material of SMA mixtures in conformance with the following : 1) SMA surface and intermediate mixtures containing RAP shall use the PG grade of asphalt cement designated by the mix specified on the plans or in the proposal e.g. and SMA-12.5 (76-22). 2) The final asphalt mixture shall conform to the requirements for the type specified. 3) During the production process, RAP material shall not be allowed to contact open flame. 4) RAP material shall be handled, hauled and stored in a manner that will minimize contamination. Further, the material shall be stockpiled and used in such manner that variable asphalt contents and asphalt penetration values will not adversely affect the consistency of the mixture Composition of SMA Mixture The SMA mixture shall be designed and tested using a gyratory compactor and shall conform to the requirements listed in Table II-24 and Table II-25 One percent hydrated lime will be required as an antistripping additive. An alternative antistripping additive can be used only if permitted by the Engineer. Mix Type & PG Allowable RAP Percentage in Mix SMA-9.5 (70-22), SMA-12-5(70-22) & SMA-19.0(70-22) 0.0 to 20.0 SMA-9.5 (76-22), SMA-12-5(76-22) & SMA-19.0(76-22) 0.0 to 15.0 page 28 Appendix B VDOT and Platinum Performance Partners, LLC

313 Materials Specifications Table II-24. SMA Design Range Table II-25. SMA Mixture Requirements Acceptance A lot will be considered acceptable for gradation and asphalt content if the mean of the test results obtained is within the tolerance allowed from the job-mix formula. The production tolerances for the control sieves and asphalt content shall be as follows: VDOT and Platinum Performance Partners, LLC Appendix B page 29

314 Materials Specifications Production tolerance for the specimen height after compaction is 4.25 to 4.75 inches. The Contractor shall check and report the VCA of the mix during production for each gyratory sample. If the VCA of the mix exceeds the VCA of the DRC, the Contractor shall stop production and notify the Engineer. Production shall not resume until the Contractor has taken corrective action. The Contractor shall check and report the percentage of flat and elongated particles (F&E) in the coarse aggregates of the mix design during production. When the SMA material is sampled for acceptance (gradation and AC content); two of the eight sub-lots must be selected for F&E verification in the first lot. The F&E testing will be performed on the coarse aggregate material retained on the #4 sieve in accordance with the requirements of VTM-121, after the gradation is performed. If passing results are obtained on each sample in the first lot, then F&E testing shall be performed on a frequency of every second lot of material produced (i.e. Lots 3, 5, 7, etc.) by randomly selecting two random sub-lots. If the F&E of the mix exceeds the specified limits, the Contractor shall stop production and notify the Engineer. Production shall not resume until the Contractor has taken corrective action and the Engineer has approved the corrective action. Once production has resumed, the Contractor shall determine the F&E of the mix for two consecutive lots by randomly selecting two sub-lots per lot. If passing results are obtained for these two lots, then the F&E testing frequency shall return to every second lot of material produced. In the event the Department determines that the mixture being produced does not conform to the approved job-mix formula and volumetric properties in Table I-B based on Department or Contractor s test results, the Contractor shall immediately make corrections to bring the mixture into conformance with the approved job mix formula or cease paving with that mixture. Subsequent paving operations, using either a revised or other job-mix formula which has not been verified as described herein, shall be limited to a test run of 300 tons maximum if such material is to be placed in Department project work. No further paving for the Department using that specific mixture shall occur until the acceptability of the mixture being produced has been verified using the 300-ton constraint. page 30 Appendix B VDOT and Platinum Performance Partners, LLC

315 Materials Specifications SMA Mixing Plant Plants used for the preparation of the SMA mixture shall conform to the following: a) Handling of Mineral Filler: Adequate dry storage shall be provided for the mineral filler that will, at a minimum, consist of a waterproof cover that shall completely cover the stockpile at all times. Provisions shall be made for metering of the filler into the mixture uniformly and in the desired quantities. In a batch plant, mineral filler shall be added directly into the weigh hopper. In a drum plant, mineral filler shall be added directly onto the cold feed belt. Equipment shall be capable of accurately and uniformly metering the large amounts of mineral filler up to 25 percent of the total mix. b) Fiber Addition: Adequate dry storage shall be provided for the fiber additive, and provisions shall be made for accurately and uniformly metering fiber into the mixture at plus or minus 10 percent of the desired quantities. Introduction of loose or pelletized fiber shall require a separate system that can accurately proportion, by weight, the required quantity of fiber in such a manner as to ensure consistent, uniform blending into the mixture at all rates of production and batch sizes. This supply system shall be interlocked with the other feeding devices of the plant system, and sensing devices shall provide for interruption of mixture production if the introduction of fiber fails. Batch Plant: Loose fiber or pelletized fiber shall be added through a separate inlet directly into the weigh hopper above the pugmill. The addition of fiber shall be timed to occur during the hot aggregate charging of the hopper. Adequate dry mixing time is required to ensure proper blending of the aggregate and fiber stabilizer. Therefore, dry mixing time shall typically be increased 5 to 15 seconds. Wet mixing time shall typically be increased at least 5 seconds for cellulose fibers to ensure adequate blending with the asphalt cement. When fiber is used, the fiber supply system shall include low level and no flow indicators and a printout of the date, time, and net batch weight of fiber. Drum Mix Plant: When fiber is used, the fibers shall be added in such a manner as not to be entrained into the exhaust gases of the drum plant. The fiber supply system shall include low level and no flow indicators and a printout of status of feed rate in pounds per minute. When pelletized fibers are used, they shall be added directly into the drum mixer through the RAP inlet or a specialized fiber inlet. Operation of the drum mixer shall be such as to ensure complete blending of the pelletized fiber into the mix. c) Hot Mixture Storage: When the hot mixture is not hauled immediately to the project and placed, suitable bins for storage shall be provided. Such bins shall be either surge bins to balance production capacity with hauling and placing capacity or storage bins that are heated and insulated and that have a controlled atmosphere around the mixture. The holding times shall be within limitations imposed by the Engineer, based on laboratory tests of the stored mixture. In no case shall the SMA mixture be kept in storage more than 8 hours. VDOT and Platinum Performance Partners, LLC Appendix B page 31

316 Materials Specifications d) Mixing Temperature: The recommended plant mixing temperature for PG should be 315 to 340 degrees F and at no time shall the temperature exceed 350 degrees F. For PG 76-22, the plant mixing temperatures shall be within the limits of the asphalt supplier s recommendations. page 32 Appendix B VDOT and Platinum Performance Partners, LLC

317 Materials Specifications SS August 3, 2011 VIRGINIA DEPARTMENT OF TRANSPORTATION 2007 ROAD AND BRIDGE SUPPLEMENTAL SPECIFICATIONS SUPPLEMENTAL SECTION 211 ASPHALT CONCRETE SECTION 211 ASPHALT CONCRETE of the Specifications is amended as follows: Section Description is replaced with the following: Asphalt concrete shall consist of a combination of mineral aggregate and asphalt material mixed mechanically in a plant specifically designed for such purpose. An equivalent single-axle load (ESAL) will be established by the Engineer, and SUPERPAVE mix types may be specified as one of the types listed as follows: Mix Type Equivalent Single-Axle Load (ESAL) Range (millions) Minimum Asphalt Performance Grade (PG) 2 Aggregate Nominal Maximum Size 1 SM-9.0A 0 to /8 in SM-9.0D 3 to /8 in SM-9.0E Above /8 in SM-9.5A 0 to /8 in SM-9.5D 3 to /8 in SM-9.5E Above /8 in SM-12.5A 0 to /2 in SM-12.5D 3 to /2 in SM-12.5E Above /2 in IM-19.0A Less than /4 in IM-19.0D 10 to /4 in IM-19.0E 20 and above /4 in BM-25.0A All ranges in BM-25.0D Above in 1 Nominal Maximum Size is defined as one sieve size larger than the first sieve to retain more than 10 percent aggregate. 2 Minimum Asphalt Performance Grade (PG) is defined as the minimum binder performance grade for the job mixes as determined by AASHTO T170 or AASHTO M320. Asphalt concrete shall conform to the requirements for the mix type designated. At the Contractor s option, an approved Warm Mix Asphalt (WMA) additive or process may be used to produce the asphalt concrete (AC) mix type designated. Section (h) antistripping additive is amended by adding the following to the second paragraph: When a Warm Mix Asphalt (WMA) additive or process, as described in (i) of the Specifications, is used in the production of asphalt concrete, the minimum TSR requirement shall be 0.80 for the design and production tests. VDOT and Platinum Performance Partners, LLC Appendix B page 33

318 Materials Specifications Section (j)1 is replaced with the following: 1. Asphalt surface, intermediate and base mixtures containing RAP should use the performance grade (PG) of asphalt cement as indicated in Table II-I4A, however, the choice of PG to use in the mix shall be the responsibility of the Contractor in order to meet the requirements of Section of the Specifications. Section Materials is amended by adding the following: (k) Warm Mix Asphalt (WMA) additives or processes shall be approved by the Department prior to use. Approved materials and processes shall be obtained from the Department s approved list which is included in the Materials Division s Manual of Instructions. TABLE II-12A AGGREGATE PROPERTIES is amended to add Mix Type IM-19.0E as follows: TABLE II-12A Aggregate Properties Coarse Aggregate Properties CAA ASTM D fractured 2 fractured F & E (5:1) Fine Aggregate Properties Mix Type face faces % by weight SE FAA IM-19.0 E 95% min. 90% min. 10% max. 1 45% min. 45% min. TABLE II-13 ASPHALT CONCRETE MIXTURES: DESIGN RANGE is amended to add Mix Type IM-19.0E to IM-19.0 A,D as follows: Mix Type 2 in TABLE II-13 Asphalt Concrete Mixtures: Design Range 1 1 1/2 in 1 in Percentage by Weight Passing Square Mesh Sieves 3/4 1/2 3/8 No. No. No. in in in IM-19.0 A,D,E max No. 50 No. 200 page 34 Appendix B VDOT and Platinum Performance Partners, LLC

319 Materials Specifications TABLE II-14 MIX DESIGN CRITERIA is replaced with the following: Mix Type VTM (%) Production VFA (%) TABLE II-14 Mix Design Criteria VFA (%) Production Min. VMA Fines/Asphalt Ratio No. of Gyrations (Note 1) Design (Note 2) (%) (Note 3) N Design SM-9.0A Notes 1,2, SM-9.0D Notes 1,2, SM-9.0E Notes 1,2, SM-9.5A Notes 1,2, SM-9.5D Notes 1,2, SM-9.5E Notes 1,2, SM-12.5A Notes 1,2, SM-12.5D Notes 1,2, SM-12.5E Notes 1,2, IM-19.0A Notes 1,2, IM-19.0D Notes 1,2, IM-19.0E Notes 1,2, BM-25.0A Notes 2,3, BM-25.0D Notes 2,3, SM = Surface Mixture; IM = Intermediate Mixture; BM = Base Mixture. Note 1: Asphalt content should be selected at 4.0 % Air Voids, Note 2: During production of an approved job mix, the VFA shall be controlled within these limits. Note 3: Fines-asphalt ratio is based on effective asphalt content. Note 4: Base mix shall be designed at 2.5% air voids. BM-25.0 A shall have a minimum asphalt content of 4.4% unless otherwise approved by the Engineer. BM-25.0D shall have a minimum asphalt content of 4.6% unless otherwise approved by the Engineer. Section Job-Mix Formula is amended by deleting the second paragraph of (a). Section Job-Mix Formula is amended to replace (c) with the following: (c) Three trial blends for gradation shall be run at one asphalt content. Section Job-Mix Formula is amended to replace (d)8 with the following: 8. For surface mixes, permeability test data shall be submitted in accordance with VTM 120 using either single point verification or the regression method for each surface mix having a different gradation. If the average of the permeability results from the single point verification method exceeds 150 x 10-5 cm/sec, or if the regression method predicts a permeability exceeding 150 x 10-5 cm/sec at 7.5% voids, the Contractor shall redesign the mixture to produce a permeability number less than 150 x 10-5 cm/sec. VDOT and Platinum Performance Partners, LLC Appendix B page 35

320 Materials Specifications Section Job-Mix Formula is amended to replace (f) with the following: (f) A determination will be made that any asphalt concrete mixture being produced conforms to the job-mix formula approved by the Department. The Department and Contractor will test the mixture using samples removed from production. The following tests will be conducted to determine the properties listed: Property Test Asphalt content VTM-102, (VTM-36 when approved) Gradation AASHTO T-30 SUPERPAVE properties AASHTO R35 Asphalt cement material AASHTO T316 or T-201 For Warm Mix Asphalt (WMA), SUPERPAVE properties will be determined by the Department and Contractor based on the mix designation in Section (d)6 of the Specifications. The Department will perform rut testing in accordance with the procedures detailed in VTM-110. If the results of the rut testing do not conform to the following requirements, the Engineer reserves the right to require adjustments to the job-mix formula: Mix Designation Maximum Rut Depth, mm A 7.0 D 5.5 E, (S) 3.5 After calibration of the gyratory compactor is completed, adjustments to the job-mix formula may be required by the Engineer. In the event the Department determines that the mixture being produced does not conform to the approved job-mix formula and volumetric properties specified in Table II- 14 based on the Department s or Contractor s test results, the Contractor shall immediately make corrections to bring the mixture into conformance with the approved job-mix formula or cease paving with that mixture. Subsequent paving operations using either a revised or other job-mix formula that has not been verified as described herein shall be limited to a test run of 100 to 300 tons of mixture if such material is to be placed in Department project work. No further paving for the Department using that specific mixture shall occur until the acceptability of the mixture being produced has been verified using the 100 to 300 ton constraint. page 36 Appendix B VDOT and Platinum Performance Partners, LLC

321 Materials Specifications TABLE II-14A Recommended Performance Grade of Asphalt Cement Percentage of Reclaimed Asphalt Pavement (RAP) in Mix Mix Type %RAP 25.0% 25.0% < %RAP 30% 25.0% < %RAP 35% SM-4.75A, SM-9.0A, SM-9.5A, SM-12.5A SM-4.75D, SM-9.0D, SM-9.5D, SM-12.5D PG PG PG PG IM-19.0A PG PG IM-19.0D PG PG BM-25.0A PG PG BM-25.0D PG PG Based on rut testing performed by the Department and/or field performance of the job mix, the Engineer reserves the right to require adjustments to the job-mix formula. Section Asphalt Concrete Mixtures is amended by replacing (b) with the following: (b) Types IM-19.0A, IM-19.0D, and IM-19.0E asphalt concrete shall consist of crushed stone, crushed slag, or crushed gravel and fine aggregate, slag or stone screenings, or a combination thereof combined with asphalt cement. NOTE: At the discretion of the Engineer, an intermediate mix may be designated as either SM-19.0A, SM-19.0D or SM-19.0E. When designated as such, no more than 5 percent of the aggregate retained on the No. 4 sieve may be polish susceptible. All material passing the No. 4 sieve may be polish susceptible. Section Asphalt Concrete Mixtures is amended to replace (e) with the following: (e) Type SM-9.5, SM-12.5, IM-19.0 and BM-25.0 asphalt concrete may be designated E (polymer modified), or stabilized (S). Asphalt concrete mixtures with the E designation may not be stabilized. 1. Type E asphalt mixtures shall consist of mixes incorporating a neat asphalt material with polymer modification complying with the requirements of PG and have a rolling thin film oven test residue elastic recovery at 77 degrees F of a minimum of 70 percent when tested in accordance with ASTM D 6084 procedure A. E designated mixtures shall not contain more than 15 percent reclaimed asphalt pavement (RAP) material. 2. Type (S) asphalt mixtures shall consist of mixes incorporating a stabilizing additive from the Department s approved list found in the Materials Division s Manual of Instructions. These mixes shall be designated with an (S) following the standard mix designation. The minimum required additive shall be as specified on the Department s approved list found in the Materials Division s Manual of Instructions. 3. Type L asphalt mixtures will be allowed to contain a 100 percent polishing coarse and fine aggregate. These mixes shall be designated with a L following the standard mix designation. Section Testing is amended to delete the last sentence of the last paragraph. VDOT and Platinum Performance Partners, LLC Appendix B page 37

322 Materials Specifications Section Tests is replaced with the following: The Department may sample materials entering into the composition of the asphalt concrete, the mixture, or the completed pavement. The Contractor shall cooperate with the Engineer in obtaining these samples. When samples are obtained from the pavement, the resulting voids shall be filled and refinished by the Contractor without additional compensation. Abson recovery samples shall be PG graded according to the requirements of AASHTO M Samples meeting the required grades specified in Section of the Specifications shall be acceptable. When the Department performs PG grading on the asphalt in a Contractor s liquid asphalt storage tank, the Engineer will notify the asphalt concrete producer and binder supplier if tests indicate that the binder properties of the asphalt material differ from those of the approved job-mix. The asphalt concrete producer and binder supplier shall determine corrective action with the approval of the Engineer. Section Acceptance is amended to replace the second paragraph with the following: Acceptance for gradation and asphalt cement content will be based on the mean of results of eight tests performed on samples taken in a stratified random manner from each 4,000-ton lot (8,000-ton lots may be used when the normal daily production of the source from which the material is being obtained is in excess of 4,000 tons). Unless otherwise approved by the Engineer, samples shall be obtained from the approximate center of the truckload of material. Any statistically acceptable method of randomization may be used to determine when to take the stratified random sample; however, the Department shall be advised of the method to be used prior to the beginning of production. Section Acceptance is amended to replace the third sentence of the fourth paragraph with the following: The maximum temperature as recommended by the supplier shall not be exceeded for a mix designated E or (S). Table II-15 PROCESS TOLERANCE is replaced with the following: No. Test s TABLE II-15 Process Tolerance Tolerance on Each Laboratory Sieve and Asphalt Content: Percent Plus and Minus Top No. No. No. No. Size 1 ½ 1 ¾ ½ 3/ No. 200 A.C Defined as the sieve that has 100% passing as defined in Table II-13. page 38 Appendix B VDOT and Platinum Performance Partners, LLC

323 Materials Specifications Section is amended to replace the last three paragraphs with the following: The unit bid price will be reduced by 0.5 percent for each adjustment point applied for standard deviation. Section Referee System is amended to replace (a) and (b) with the following: (a) In the event the test results obtained from one of the eight samples taken to evaluate a particular lot appear to be questionable, the Contractor may request in writing that the results of the questionable sample be disregarded, whereupon the Contractor shall have either an AASHTO-accredited lab or Department lab perform tests on five additional samples taken from randomly selected locations in the roadway where the lot was placed. In the event the Engineer determines that one of the 8 test results appears to be questionable, the Department will perform tests on five additional samples taken from the randomly selected locations in the roadway where the lot was placed. The test results of the seven original, i.e. unquestioned, samples will be averaged with the test results of the five road samples, and the mean of the test values obtained for the twelve samples will be compared to the requirements for the mean of twelve tests as specified in Table II-15. (b) In the event the Contractor questions the mean of the eight original test results obtained for a particular lot, the Contractor may request in writing approval to have either an AASHTO-accredited lab or Department lab perform additional testing of that lot. In the event the Engineer determines that the mean of the eight original test results are questionable, the Department will perform additional testing of that lot. The test results of the eight samples will be averaged with the test results of the four additional samples taken from randomly selected locations in the roadway where the lot was placed, and the mean of the test values obtained from the twelve samples will be compare to the requirements for the mean of twelve tests as specified in Table II-15. If the Contractor requests additional tests, as described in (a) or (b) herein, the Contractor shall sample the material and have either an AASHTO-accredited lab or Department lab test the material in accordance with Department-approved procedures. The Engineer reserves the right to observe the sampling and testing. In the event the mean of the test values obtained for the twelve samples conforms to the requirements for the mean of twelve tests, the material will be considered acceptable. In the event that the mean of the test values obtained for the twelve samples does not conform to the requirements for the mean result of twelve tests, the lot will be adjusted in accordance with the adjustment rate specified in Section of the Specifications. Samples of the size shown herein shall be saw cut by the Contractor for testing without the use of liquids: Application Rate Minimum Sample Size 125 lb/yd 2 8 by 8 in 150 lb/yd 2 7 by 7 in 200 lb/yd 2 6 by 6 in 300 lb/yd 2 5 by 5 in VDOT and Platinum Performance Partners, LLC Appendix B page 39

324 Materials Specifications Section Initial Production is replaced with the following: (a) (b) Warm Mix Asphalt (WMA): At the start of production, the Contractor shall place no more than 500 tons or up to one day s production as directed by the Engineer at an approved site, which may be the project site, so the Engineer can examine the process control of the mixing plant, the Contractor s placement procedures, surface appearance of the mix, compaction patterns of the Contractor s roller(s), and correlation of the nuclear density device. Hot Mix Asphalt (HMA): At the start of production of a mix not previously used on a state roadway, the Contractor shall place 100 to 300 tons or up to one day s production as directed by the Engineer at an approved site, which may be the project site, so the Engineer can examine the process control of the mixing plant, the Contractor s placement procedures, surface appearance of the mix, compaction patterns of the Contractor s roller(s), and correlation of the nuclear density device. The material shall be placed at the specified application rate and will be paid for at the contract unit price for the specified mix type. The Engineer will determine the disposition of material that was not successfully produced and/or placed due to negligence in planning, production, or placement by the Contractor. page 40 Appendix B VDOT and Platinum Performance Partners, LLC

325 MCS: Asphalt Plant Certification C Tests and Procedures Sand Equivalent Test The sand equivalent test, described in AASHTO T 176, is a method of determining the relative proportion of detrimental fine dust or clay-like materials in the portion of aggregate passing the 4.75 mm (No. 4) sieve. The sand equivalent test is conducted as follows: 1. A sample of material is placed in a transparent, graduated cylinder containing a prepared solution of calcium chloride, glycerin and formaldehyde in water. 2. The sample and solution are shaken in a prescribed manner. 3. An identical solution is passed through an irrigator tube which, under pressure, is used to wash the clayey material upward and out of the sample as the cylinder is gradually filled. 4. After a 20 minute settling period, the top of the clay suspension is read. 5. A metal weighted foot is lowered into the cylinder and allowed to come to rest on top of the clean sand. 6. The level of the bottom of the foot is read. 7. The sand equivalent value is the ratio, multiplied by 100, of the reading at the top of the sand, divided by the reading at the top of the clay. For all sands, the minimum sand equivalent is 30. VDOT and Platinum Performance Partners, LLC Appendix C page 1

326 Test and Procedures Magnesium Sulfate Soundness Test Equipment and test procedures are detailed in AASHTO T 104. A brief description of the test follows: 1. Container of sized fractions of an aggregate are immersed in a saturated solution of magnesium sulfate. The sample containers are constructed to allow free access to and drainage of the solution from the sample without loss of aggregate. 2. Samples are oven-dried after immersion. 3. After the required number of immersion and drying cycles, the percent weight loss of the sized fractions is determined by sieving. 4. Weighted average percent losses for each size fraction, based upon the graduation of the original sample, are determined. The total of these values is the percent loss test value. Silica Content of Sand Sands that are used for deslicking mixes must not only be free of clay and dirt, but must also have a high silica content. The chemistry Laboratory will determine the percent of silica (SiO2) in sands for checking boil time. Virginia Test Method 13 Anti -Stripping Additive - November 1, Scope 1.1. This method of test covers a procedure for determining the effectiveness of an anti-stripping additive when used as an asphalt anti stripping compound in asphalt mixtures This standard may involve hazardous materials, operations, and equipment. This standard does not purport to address all of the safety problems associated with its use. It is the responsibility of whoever uses this standard to consult and establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. 2. Apparatus 2.1. A balance, accurate to 0.10 gram Pans and spatula for mixing the aggregate and asphalt anti stripping additive Beakers, approximately 600 ml, for boiling asphalt mixtures A gas burner for heating water in beakers Stopwatch for checking boil time. page 2 Appendix C VDOT and Platinum Performance Partners, LLC

327 Test and Procedures 3. Material 3.1. A standard aggregate is used. The aggregate is obtained from Lone Jack Limestone Co., Glasgow, Virginia. It is a 50:50 blend of #8 (2.36 mm) and #10 (0.425 mm) Quartzite. The blend shall be separated by dry sieving and proportioned to meet the following gradation for each test batch. Sieve Size % Passing (in.) (mm) 1/ mm /8 9.5 mm 90.0 No mm 62.0 No mm 42.0 No mm 18.0 No mm 12.0 No mm 8.0 No mm The asphalt is AC 20 (PG 64-22) and meets Virginia specifications. 4. Procedure g of asphalt cement, treated with the anti-stripping additive at the manufacturer s recommended percentage shall be placed in a clean container and heated at 275 F± 5 F (135 ±3 C). The container shall be sealed securely and placed in an oven which will hold this temperature for 96 hours Remove the sample from the oven and stir thoroughly Mix 6 percent of the treated asphalt with the proportioned test batch to produce a total mix of 400 g. The total mix shall be 24 g treated asphalt, and 376 g of proportioned aggregate (one test batch). Heat on hot plate and stir until coated After complete coating, allow mixture to cool to 230 F± 10 F (110±5 C), place approximately 200 g on a paper towel before boiling. Place the remainder (approximately 200 g) of the mixture in boiling water and continue boiling for 10 minutes ± 30 seconds. Then remove from heat source Drain the water from the mixture and place the mixture on a paper towel. Allow to cool to room temperature The next morning compare the boiled and un-boiled portions on the paper towels. If the boiled portion shows more signs of stripping than the un-boiled portion, the test fails. VDOT and Platinum Performance Partners, LLC Appendix C page 3

328 Test and Procedures 5. General Requirements 5.1. The anti-stripping additive shall contain no ingredient harmful to the asphalt material and shall not alter appreciably the specified characteristics of the asphalt material when added in the recommended proportions. It shall be capable of thorough dispersion in the asphalt material at the temperature of use and shall be capable of remaining in the asphalt material in storage indefinitely at temperature normally encountered without detrimentally affecting the asphalt material, or losing its effectiveness as an asphalt anti stripping compound and without any discernible settlement or stratification. 6. Report 6.1. Report as passing or failing the Boiling Test on Form TL 50. Field Testing 1. Scope a. The following procedure is to be used for determining the effectiveness of an anti-stripping additive in combination with the materials used for production at the asphalt concrete plant. 2. Apparatus a. 12.5mm (l/2 inch) sieve. b. A balance, accurate to one gram (0.04 oz). c. Beakers, approximately 600 ml (20 oz) for boiling asphalt mixtures. d. A gas burner for heating water in beakers. e. Stopwatch for checking boil time. 3. Procedure a. For control testing of plant mixed material, use approximately 400 g of the mixture passing the 12.5mm (l/2 inch) sieve. b. The test will be performed at the District or Central Laboratory and shall be run within 30 hours after obtaining the sample. The sample shall be heated to a temperature of 230 F ±10 F (110 ±5 C). (The sample shall not remain at this temperature more than 30 minutes). When necessary for the test to be run at the plant, it shall be conducted as soon as the sample cools to 230 F ± 10 F (110 ±5 C). Note: Remove plus 12.5mm (l/2 inch) material from mixture prior to attaining specified temperature. page 4 Appendix C VDOT and Platinum Performance Partners, LLC

329 Test and Procedures c. Place approximately 200 g on a paper towel before boiling. d. Place the remainder (approximately 200 g) of the mixture in boiling water and continue boiling for 10 minutes ±30 seconds. Then remove from heat source. e. Drain the water from the mixture and place the sample on a paper towel. Allow to cool at room temperature. f. The next morning compare the boiled and un-boiled portions on the paper towels. If the boiled portion shows more signs of stripping than the un-boiled portion, the test fails. The producer shall be notified immediately and a second sample is taken and tested as stated herein. g. If the second sample fails, production shall be halted until corrective action is taken to the satisfaction of the Engineer. h. On resumption of production, samples will be taken immediately and tested as stated above. 4. Report a. Report as passing or failing the Boiling Test on Form TL 50. VDOT and Platinum Performance Partners, LLC Appendix C page 5

330 Test and Procedures Virginia Test Method 22 Field Determination of Percent Density of Compacted Asphalt Concrete Mixtures - (Asphalt Lab) - October 1, Scope This method covers the procedure for determining the percent density of compacted Asphalt Concrete mixtures in the field. 2. Apparatus 2.1. Rotary saw or coring machine as specified in VDOT specifications or special pro visions. 3. Test Specimens 3.1. Two 4 x 4 in. (100 x 100 mm) sawed specimens shall be taken per site or two 4 in. (100 mm) diameter core specimens Care shall be taken to avoid distortion, bending or cracking of specimens during and after removal from the pavement To aid in cooling specimens, CO2, or dry ice is recommended for use prior to sawing and removing from the pavement If necessary, specimen may be separated from other pavement layers by sawing or other satisfactory means. 4. Procedure 4.1. Measure thickness of test specimen Determine the bulk specific gravity of the specimen in accordance with VTM The initial theoretical maximum specific gravity of asphalt concrete mix ure may be the job-mix value determined at the job-mix asphalt content until the production value has been determined on the material being placed in accordance with AASHTO T-209. AWARENESS/IMPORTANT Note: The initial theoretical maximum specific gravity value shall be verified by the District or Central Office Laboratory For dense graded asphalt concrete mixes (i.e. SUPERPAVE mixes), the theoretical maximum specific gravity used as the denominator for the percent density calculation shall be determined by a moving average of five values based on the contractor s test results. page 6 Appendix C VDOT and Platinum Performance Partners, LLC

331 Test and Procedures For stone matrix asphalt concrete mixes, the theoretical maximum specific gravity used as the denominator for the percent density calculation shall be determined by using the simple average of the contractor s daily production test results. Only the theoretical maximum specific gravity results for that day s production shall be used Until five values are obtained from the contractor s testing, the theoretical maximum specific gravity used shall be a simple average. 5. Calculation 5.1. Calculate the percent density of each Site as follows, where the Average Bulk Specific Gravity is either the average of the two specimens per site or the average bulk specific gravity of the total sites being evaluated, reported to 3 decimal places: Percent Density = Average Bulk Specific Gravity Theore cal Maximum Specific Gravity 100 Where the Average Bulk Specific Gravity is either the average of the two specimens per site or the average bulk specific gravity of the total sites being evaluated, reported to 3 decimal places 6. Report 6.1. Report depth to nearest 0.1 in. (3 mm) Report percent density of each test specimen to nearest 0.1 percent. 7. Precision 7.1. If the difference in the bulk specific gravity between two specimens from the same test site varies by more than 0.045, discard and obtain two more specimens from a new test site If the difference in theoretical maximum specific gravity between the VDOT monitor sample and the contractor sample varies by more than per AASHTO T-209, then the results (VDOT and contractor) shall not be used in the calculation of percent density unless testing error is identified. If testing error is identified, then VDOT will determine which maximum theoretical specific gravity result to use in the percent density calculation. VDOT and Platinum Performance Partners, LLC Appendix C page 7

332 Test and Procedures Virginia Test Method 36 Quantitative Extraction of Bitumen From Asphalt Paving Mixtures By the Reflux Method November 1, 2000 AASHTO T 164, Method B, shall be followed, except as modified below: 1. Scope 1.1. The aggregate remaining shall be used for sieve analysis according to AASHTO T This standard may involve hazardous materials, operations, and equipment. This standard does not purport to address all of the safety problems associated with its use. It is the responsibility of whoever uses this standard to consult and establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. 5. Apparatus 5.1 Oven may be omitted. 5.2 Pan minimum dimensions of 12 in. (300 mm) long, 8 in. (200 mm) wide, and 1 in. (25 mm) deep. 5.3 The balance shall be capable of weighing at least 2000g to an accuracy of 1.0 g. 5.4 The hot plate shall be thermostatically controlled. 5.6 Ignition Dish may be omitted. 5.7 Desiccators may be omitted. 6. Reagent 6.1 May be omitted. 6.2 May be omitted. 6.3 Use 1000 ml of solvent (800 ml of 1,1,1, Trichloroethane, inhibited, and 200 ml of 95% ethyl alcohol (denatured)). 6.4 May be omitted. 8. Sampling 8.1 The test sample shall be the end result of quartering a larger sample taken in accordance with VTM 48. (AASHTO T 248 may be used as a guide to quartering.) page 8 Appendix C VDOT and Platinum Performance Partners, LLC

333 Test and Procedures The size of the test sample shall be governed by the nominal maximum aggregate size in the mixture. In no case shall the test sample weigh less than the minimum weight of sample shown below: Nominal Maximum Aggregate Size Size of Sample Minimum Weight (Mass) of Sample No. 4 (4.75 mm) 400 g 3/8 in. (9.5 mm) 500 g 1/2 in. (12.5 mm) 1000 g 3/4 in. (19.0 mm) 1200 g 1 in. (25.0 mm) 1400 g 1 1/2 in. (37.5 mm) 1800 g 9. Moisture Content 9.1 The moisture determination (VTM 49) will be made as deemed necessary. When the sample for moisture determination is to be used for the determination of Asphalt Content, care should be taken to completely wash all the mixture from the pan into the Reflux apparatus using the solvent for that test. The dry weight of the mixture shall be used in the calculation of Asphalt Content. 13. Apparatus Glass Jar, cylindrical, plain, 8 3/4 in. ( mm) OD, 18 in. (457 mm) high, made of heat resistant glass The filter paper to be used shall be Whatman No. 2, Eaton Dikeman, Grade 613, or equivalent, 38.5 cm in diameter. This type of filter paper eliminates the ash correction. 15. Procedure Fold each sheet of filter paper on its diameter and fold once again. Open to form a hollow cone with one ply on one side and three plies on the other, and a single one ply seam May be omitted Place the test portion in the frame(s). If two frames are used, distribute the test portion approximately equally between the two. VDOT and Platinum Performance Partners, LLC Appendix C page 9

334 Test and Procedures Pour the 1000 ml of solvent into the glass jar and place the loaded cone(s) and frame(s) in the jar. The solvent level must be below the tip of the lower cone Remove the frame assembly from the cylinder. Allow to dry in air as close as practical to an exhaust fan or in a vented hood. Then remove the filter paper(s) containing the sample and place in a pan. Dry to constant mass and then burn the filter paper. Record the mass of extracted aggregate May be omitted. page 10 Appendix C VDOT and Platinum Performance Partners, LLC

335 Test and Procedures Virginia Test Methods - 48 Sampling Asphalt Paving Mixtures November 1, 2000 AASHTO T 168 shall be followed, except as modified below. 1. Scope 1.1. These methods cover the procedures for sampling mixtures of asphalt materials with mineral aggregate as prepared for use in paving. The samples may be used for either of two purposes: To ascertain the periodic variation in characteristics of the mixture for the purpose of controlling uniformity, or To represent an average of the asphalt mixture This standard may involve hazardous materials, operations, and equipment. This standard does not purport to address all of the safety problems associated with its use. It is the responsibility of whoever uses this standard to consult and establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. 3. Size of Sample 3.1. The size of sample shall be governed by the Materials Division Manual of Instructions. 4. Sampling Plant Mixed Asphalt Mixtures at Place of Manufacture 4.1. Production Control (Producer) and Acceptance (Monitor) samples for determination of gradation and asphalt content shall be taken from the truck by means of a square point shovel. Using the square point shovel, remove a minimum of 6 (150 mm) of the material from the top by scraping horizontally across the location to be sampled. This will leave a relatively flat area in which to take the sample. With horizontal movements of the square point shovel through the area to be sampled, take sufficient material for the type of sample. A stratified random method of sampling shall be used as approved by the Engineer All other samples of asphalt mixtures shall be obtained from two or more locations in the truck and combined to form a representative sample. With the exception of the stratified random method of sampling, the sampling procedure as outlined in 4.1 above shall apply Delete 4.4. Delete VDOT and Platinum Performance Partners, LLC Appendix C page 11

336 Test and Procedures 5. Sampling Plant Mixed Asphalt Mixtures from Roadway 5.1. Samples of asphalt paving mixtures taken from the finished pavement for determination of gradation and asphalt content shall be taken in accordance with Section of the specifications. Samples taken for the purpose of density determination shall be in accordance with Section (d) of the specifications Samples taken for other purposes shall be taken as directed by the Engineer Samples taken for other purposes shall be taken as directed by the Engineer. page 12 Appendix C VDOT and Platinum Performance Partners, LLC

337 Test and Procedures Virginia Test Method 99 The Design of Stone Matrix Asphalt (SMA) Mixtures (Asphalt Lab) March Scope 1.1. This test method covers the design of stone matrix asphalt (SMA) mixtures. It is based on the idea of designing the aggregate skeleton so that stone-on-stone contact is maintained in the mixture. Stone-on-stone contact will provide load carrying capacity for heavy traffic situations. This method is organized into three distinct sections: Procedures, Calculations and Equations and a Design Example. The method involves the determination of volumetric properties of the coarse aggregate fraction compacted by a dry rodding procedure and of specimens prepared with a SUPERPAVE gyratory compactor This standard may involve hazardous materials, operations, and equipment. This standard does not purport to address all of the safety problems associated with its use. It is the responsibility of whoever uses this standard to consult and establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. 2. Significance and Use 2.1. This method is used in the laboratory mix design of SMA mixtures. The Voids in the Coarse Aggregate (VCA) is determined for the coarse aggregate fraction of the mixture by a dry rodding procedure for three aggregate blends. These blends are combined with asphalt cement, compacted and the volumetric properties are determined. The desired stone-on-stone contact of the coarse aggregate fraction exists when the VCA of the mixture is equal to or less than the VCA of the coarse aggregate obtained by the dry rodding procedure. The selected job mixture gradation blend is then used to make additional samples with a Gyratory device at additional asphalt contents. The optimum asphalt content is then selected to give the desired volumetric properties. Additional drainage tests shall be performed as specified to assure that the asphalt will not drain from the mixture during construction. 3. Referenced Documents 3.1. AASHTO Standards MP8 Standard Specification for Designing SMA PP41 Standard Practice for Designing SMA T19 Bulk Density ("Unit Weight") and Voids in Aggregate T166 Bulk Specific Gravity of Compacted Asphalt Mixtures Using Saturated Surface-Dry Specimens T209 Theoretical Maximum Specific Gravity and Density of Bituminous Paving Mixtures T283 Resistance of Compacted Bituminous Mixture to Moisture-Induced Damage VDOT and Platinum Performance Partners, LLC Appendix C page 13

338 Test and Procedures T312 Preparing and Determining the Density of HMA Specimens by Means of the Superpave Gyratory Compactor 3.2. Virginia Test Methods VTM-100 Determination of Draindown Characteristics in Uncompacted Asphalt Mixtures VTM-102 Determining the Asphalt Binder Content of HMA by the Ignition Method 4. Procedure Selection of gradation - At least three gradations within the SMA Design Range should be evaluated. The trial gradations, which are obtained by adjusting the amount of fine and coarse aggregates in each blend, should have the following approximate percent passing: SMA-19.0 Intermediate SMA-12.5 Surface SMA-9.5 Surface 30, 37 and 45 percent passing the 3/8-in. (9.5 mm) sieve 22,26 and 28 percent passing the No. 4 (4.75 mm) sieve 15, 20, and 25 percent passing the No. 8 (2.36 mm) sieve These blends are obtained by combining various percentages of the raw aggregates that are available for the project. It is recommended that the percentage of material passing the No. 200 (0.075 mm) sieve should be approximately 10.0 percent Determination of VCA in the coarse aggregate fraction - The coarse aggregate is defined as all component materials with 10 percent or more retained on and above the Break Point (B.P.) Sieve: Mix Type SMA-9.5 SMA-12.5 SMA-19.0 Break Point Sieve #8 (2.36 mm) #4 (4.75 mm) #4 (4.75 mm) Combine the coarse aggregates in the percentages determined in and then remove the particles passing the breakpoint sieve for the mixture type being designed. Wash the coarse aggregate and determine the Dry Rodded Unit Weight of the resulting combined coarse aggregate fraction in accordance with AASHTO T-19. page 14 Appendix C VDOT and Platinum Performance Partners, LLC

339 Test and Procedures Where: VCA DRC = G ca γ w - γ s G ca γ w 100 s = Unit weight of the coarse aggregate fraction in the dry rotted condition (lbs/ft 3 ) (kg/m 3 ) 2 w = unit weight of water (62.4 lbs/ft 3 ) (1000 kg/m 3 ) G ca = The bulk specific gravity (G sb ) of the coarse aggregate These values will be compared to the VCA mix values of the compacted mix to ensure that stone on stone contact is achieved Selection of trial asphalt content Use the following table in choosing the initial asphalt content of the mixture for the gradation selection phase. Each trial blend will be evaluated at this same AC content. Mix Type Recommended AC Content Minimum AC Content 1 SMA % 6.3% SMA % 6.3% SMA % 5.5% Note: The minimum AC content should only be approached when using aggregates with a G sb greater than 2.75; otherwise the VMA criteria will not meet the minimum VMA specified by VDOT Sample preparation and testing - Twelve samples are required; four samples at each of the three trial gradations at the asphalt content selected above. The mixing and compaction temperature shall be as follows: For mix designated as a 70-22, i.e. SMA-12.5 (70-22), the mix temperature shall be 310 degrees F to 320 degrees F and the compaction temperature shall be 295 degrees F to 300 degrees F. For mixes designated as PG or modified binders, the temperatures shall be based on documented supplier s recommendations. The aggregates are to be heated to no more than 50 ( o F) higher than the mixing temperature. Heat the asphalt binder to the mixing temperature. Aggregates and fibers should be dry mixed before adding the asphalt cement. Specimens shall be short term conditioned according to AASHTO R 30. VDOT and Platinum Performance Partners, LLC Appendix C page 15

340 Test and Procedures Three of the four samples for each trial gradation shall be compacted with a gyratory compactor (AASHTO T-312) to 75 Gyrations. The fourth sample shall be used to determine the theoretical maximum specific gravity according to AASHTO T-209 (sample size should be determined based on the maximum aggregate size). Note: Prior to mixing specimens, a butter batch is required for coating the mixing equipment. The gyratory compactor shall be one from the Materials Division s Approved List for Gyratory Compactors Selection of the job mix gradation For each trial gradation calculate the following properties: VCA mix = G mb P G bp ca VMA = 100- G mb P G s sb VTM = G mb G mm Where: G mb = average bulk specific gravity of the mix G sb = the bulk specific gravity of total aggregate P s = the percent aggregate in the total mix G ca = the bulk specific gravity of the coarse aggregate P bp = the coarse aggregate fraction as percent of the total mix G mm = the theoretical maximum density of the mixture The blend that: exceeds the minimum VMA requirement and has a VCA mix that is less than the VCA DRC should be selected as the mix design aggregate blend. Consideration should be given to the mix with least coarse aggregate if more than one of the blends satisfies the VMA and VCA criteria. 4.2 Determination of the optimum asphalt content - The optimum asphalt content is determined by the Gyratory procedure using a compactive effort of 75 Gyrations. The mixing and compaction temperature shall be the same as specified in section The number of samples required shall be 12 (three compacted and one un-compacted at each of three asphalt contents). The un-compacted samples shall be used for the maximum theoretical specific gravity determination. The design air void content, Va, shall be 3.0 percent and the remaining properties shall meet those specified in the Special Provision for SMA. The optimum asphalt content shall be at a minimum 6.3 percent for the SMA-9.5, and SMA-12.5 and 5.5 percent for the SMA The fines to effective binder content ratio (P /P be ) for SMA-9.5, 12.5 and 19.0 shall be greater or equal to 1.2 and less or equal to 2.0. page 16 Appendix C VDOT and Platinum Performance Partners, LLC

341 Test and Procedures 4.3 Draindown test - Draindown shall be determined according to VTM 100. The test should be performed at the anticipated plant production temperature and should satisfy the specified maximum of 0.30 percent. If the mixture fails to meet this requirement then the percent fibers should be increased to a level that reduces draindown to the acceptable limit. 4.4 Tensile Strength Ratio (TSR) Determine in accordance with AASHTO T-283 accept as modified in section 211 of the Road and Bridge specifications. 4.5 Furnace correction factor Determined in accordance with VTM Aggregate Properties Fine Aggregate Angularity (FAA): The FAA for all SMAs containing RAP shall be run in accordance with AASHTO T 304 Method A during design. The materials for the FAA tests shall be collected from the aggregates extracted from the ignition oven blanks used in determining the oven correction factor at the final Job Mix Formula AC content and Gradation. Flat and Elongated (F&E): The F&E test for all SMAs shall be run in accordance with VTM 121 and ASTM Materials for the F&E tests shall be collected from the aggregates extracted from the ignition oven blanks used in determining the oven correction factor at the final Job Mix Formula AC content and Gradation. 5. Equations and Calculations This section will expand upon the equations used in Section 4 and define how to use each property in the design and production of SMA for VDOT. Selection of Design Aggregate Structure: VCA DRC, VCA mix and VMA VCA DRC & G ca VCA DRC = G ca γ w - γ s G ca γ w 100 Where, s = Unit weight of the coarse aggregate fraction in the dry rotted condition (lbs/ft 3 ) (kg/m 3 ) 2 w = unit weight of water (62.4 lbs/ft 3 ) (1000 kg/m 3 ) G ca = The bulk specific gravity (G sb ) of the coarse aggregate VDOT and Platinum Performance Partners, LLC Appendix C page 17

342 Test and Procedures Note: For each trial aggregate structure combine each aggregate component together at the percentages required to meet the targeted trial gradation. Scalp this blended portion of coarse aggregates over the appropriate breakpoint sieve, and determine s according to AASHTO T-19. When determining the Rodded Unit weight of the coarse aggregate for mixes containing RAP, use the aggregate retained on the B.P. Sieve extracted from the RAP by ignition oven samples as one of the components. Calculate G ca for each trial gradation: = Where, = Percent of Aggregate I as a percent of the coarse aggregate (only include aggregates that have 10% or more retained on the BP sieve) = Percent of Aggregate 2 as a percent of the coarse aggregate (only include aggregates that have 10% or more retained on the BP sieve) + = Denoting to include all coarse aggregate components (only include aggregates that have I0% or more retained on the BP sieve) = Specific Gravity of Aggregate I = Specific Gravity of Aggregate 2 = Specific Gravity of Aggregate n To calculate the individual coarse aggregate component as a percentage of the total coarse aggregate: Where, P Cn = P n n i=1 P n P n = The individual coarse aggregate's bin percentage of the total blend (for aggregates that retain more than 10% above the break point sieve) n i=1 P n = The sum of bin percentages of all aggregate components that retain I0% or more above the break point sieve page 18 Appendix C VDOT and Platinum Performance Partners, LLC

343 Test and Procedures When using RAP, each component's contribution to the coarse aggregate bulk specific gravity is calculated the same as for virgin mixes. However the coarse bulk specific gravity (G) and coarse aggregate contribution of the RAP (P c ) must be estimated as follows: Determine the G se of the coarse portion of the RAP and convert to G sb : Determine the G se (effective bulk specific gravity) of the coarse portion of the RAP (the portion retained above the break point sieve) by determining its AC content via VTM- 102 and its maximum specific gravity (G mm ) via AASHTO T 209 and apply the following formula: G se = 100 %AC 100 %AC Gmm G b Where, G b is the binder gravity and is estimated to be For use in the G ca and subsequent VCA mix and VCA drc calculations the G se must be converted to a G sb by applying the following formula: G sb = Where, G se P bag se 100 G b + 1 P ba, is the percent binder absorbed and is estimated to be 0.8. Determine P C for coarse portion of RAP: Determine the RAP's contribution to the total coarse aggregate in the mix: P C RAP = (%RAP in the mix) X (RAP's %Retained on the Break Point Sieve) Determine the RAP's coarse aggregate contribution as a percent of just the coarse aggregate: P Cn RAP = P n n i=1 P n Use the RAP's Coarse Aggregate G sb and P C RAP when calculating G ca for use with VCA mix and VCA DRC. VDOT and Platinum Performance Partners, LLC Appendix C page 19

344 Test and Procedures VCA mix VCA mix = 100 G mb G ca Where: G mb = G ca = P bp = Bulk specific gravity of compacted specimens combined bulk specific gravity of the coarse aggregate as measured in Section = Percent aggregate by total mixture weight retained on and above the breakpoint sieve: P bp = (P s )(PA Pb ) x 100 Where: Ps = (100 AC) = Percent aggregate in the mixture expressed as a decimal (94% = 0.94) And PA bp = (100 % passing the break point sieve) Percent aggregate by total aggregate weight retained on and above the breakpoint sieve (for calculations must be expressed as a decimal i.e. 76.7% = 0.767) page 20 Appendix C VDOT and Platinum Performance Partners, LLC

345 Test and Procedures 6. Design Example Step 1: Determine aggregate and RAP components to be used and choose a target gradation for Blend 1: Target Sieve Size CA1 CA2 CA3 FA1 MF BH RAP 1 Gradation [mm] % 100.0% 100.0% 100.0% 100.0% 100.0% 100.0% % 100.0% 100.0% 100.0% 100.0% 100.0% 100.0% % 94.0% 64.0% 100.0% 100.0% 100.0% 98.0% % 65.0% 33.0% 100.0% 100.0% 100.0% 94.0% % 8.0% 6.0% 96.0% 100.0% 100.0% 71.0% % 2.0% 1.6% 67.0% 100.0% 100.0% 56.0% % 1.4% 1.5% 48.0% 100.0% 100.0% 44.0% % 1.2% 1.3% 35.0% 100.0% 100.0% 33.0% % 1.0% 1.2% 25.0% 87.0% 100.0% 21.0% % 0.9% 16.0% 75.0% 100.0% 13.0% % 0.8% 0.9% 11.0% 70.0% 98.0% 9.0% Step 2: Determine the required Bin Percentages to meet the target Gradation: Aggregate Bin Percentages Blend 1 15% RAP CA1 CA2 CA3 FA1 MF BH RAP Step 3: Resultant Gradation: Sieve Size [mm] Target Gradation Blend 1 15% RAP VDOT and Platinum Performance Partners, LLC Appendix C page 21

346 Test and Procedures Step 4: Determine Aggregate and RAP gravities: Aggregate Bin Percentages and Gravities Blend 1 15% RAP CA1 CA2 CA3 FA1 MF BH G sb G sa Use the calculated RAP G se as follows for use in the final mix G sb RAP Gravities RAP 1* RAP 1 (+BP) G mm %AC 5.60% 2.70% G se G sb G b 1.03 P ba 0.8 Where: = and G sb = % % G se P ba G se 100 G b + 1 * Separate RAP Gravities must be determined for the coarse component of the RAP if the percent retained on the break point (BP) sieve is greater than 10%. Step 5: Determine the RAP's percentage of the coarse aggregate (CA) on a component basis for the G ca Calculation RAP's Percent of the CA Component, P C 4.35 = (0.15) X (100-71) Sum of Non RAP Coarse Aggregate Components (Virgin aggregates that retain 10% or more on 74 = the BP sieve) Total CA Components to include RAP n i=1 P n = page 22 Appendix C VDOT and Platinum Performance Partners, LLC

347 Test and Procedures Step 6: Determine G ca for the VCA calculations: G ca Calculation P Cn = P n n i=1 P n CA1 19.1% = 15 / % = 19.1 / CA2 45.9% = 36 / % = 45.9 / CA3 29.4% = 23 / % = 29.4 / RAP1 5.6% = 4.35 / % = 5.6 / See note Sum 37.5% G ca = 100 / 37.5 Where: = Note: the G sb used for the RAP is that calculated for the material retained on and above the break point sieve. Step 7: Determine VCA DRC for trial blend 1 in accordance with AASTHO T-19 using G ca calculated in Step 6. Using virgin and RAP aggregates (ignition oven extracted) retained on the B.P. Sieve at the trial blend percentages, determine the Dry Rodded Unit weight of the coarse aggregate. Unit Weight of Dry Rodded Stone (per AASHTO T-19) Mass of Aggregate & Measure[kg] Mass of Measure [kg] Volume of Measure [m3] Unit Weight of Rodded Stone [kg/m3] = ( ) / Using this unit weight and the measured G ca from Step 6, calculate VCA DRC. VCA DRC G ca Unit Weight of Water ( ) [kg/m 3 ] Unit Weight of Stone (( ) [kg/m 3 ] VCA DRC 42.2% = VDOT and Platinum Performance Partners, LLC Appendix C page 23

348 Test and Procedures Where: VCA DRC = G ca γ w - γ s G ca γ w 100 Step 8: Determine the Blend G sb for VMA calculations. = GSB BIN % (P n ) (P n ) / G SB CA = 15 / CA = 36 / CA = 23 / MF = 10 / BH = 1 / RAP1 (G se ) = 15 / SUM = Blend G sb = 100 / Step 9: Batch and compact the required samples to calculate the volumetric properties of the trial blend. G mm Blend G sb Blend G ca Trial %AC 6.70% Weight in Air Weight in Water SSD Weight Bulk Sp. Gravity G mb A C B VTM % VMA % % 18.9% % 18.9% % 18.9% Averages % 18.9% page 24 Appendix C VDOT and Platinum Performance Partners, LLC

349 Test and Procedures Using the information from the gyratory volumetrics calculate VCA mix Gmb Gca PApb 72.3% = PS 93.3% = Pbp 67.4% = ( 72.3 * 93.3)/100 VCA mix 40.8% = Where: = 100 Results: VCA mix = 40.8 < VCA DRC = 42.2, OK VMA = 18.9 > Minimum VMA = 17, OK VTM = 3.9 > Design VTM = 3.5% Step 9: Repeat Steps 1 8 for Trial Blends 2 and 3 Step 10: Select the Blend that satisfies both the VCA and VMA requirements. If more than one meets both requirements take into account: Plant break down on the VMA (VMA will usually decrease by ~1% during production) and Lower percent total coarse aggregate. Step 11: Optimize AC content in accordance with Section 4.2 and VDOT s Special Provision for Stone Matrix Asphalt Step 12: Once a design AC and Aggregate Structure have been finalized then verify the aggregate properties that are measured on the blend (F&E and FAA) and determine the Oven Correction Factor per VTM 102. The materials for the aggregate tests should be collected from the aggregates extracted from the ignition oven blanks used in determining the correction factor. VDOT and Platinum Performance Partners, LLC Appendix C page 25

350 Test and Procedures Virginia Test Method 102 Determination of Asphalt Content From Asphalt Paving Mixtures By the Ignition Method (Asphalt Lab), December 1, Scope A. This test method covers the determination of asphalt content of hot-mixed paving mixtures by ignition of the asphalt cement at 1000 F (538 C) in a furnace. The aggregate remaining can be used for sieve analysis using AASHTO Test Method T 30. B. The values stated in metric units are to be regarded as the standard. C. This standard may involve hazardous materials, operations, and equipment. This standard does not purport to address all of the safety problems associated with its use. It is the responsibility of whoever uses this standard to consult and establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. 2. Referenced Documents AASHTO Standards: T 248 Reducing Field Samples of Aggregate to Testing Size T 168 Sampling Bituminous Paving Materials T 30 Mechanical Analysis of Extracted Aggregate 3. Summary of Test Methods A. The asphalt in a sample of hot-mix paving material is burned by ignition at 1000 F (538 C).The asphalt content is calculated from the mass of ignited aggregate, moisture content, and temperature compensation for the change in mass of the sample container. The asphalt content is expressed as mass percentage of the moisture-free mixtures. This method may not be applicable to mixes containing fibers or ground tire rubber (dry process). 4. Apparatus 4.1 A forced air ignition furnace, capable of maintaining the temperature at 1200 F (650 C) with an internal balance thermally isolated from the furnace chamber accurate to 0.1 g. The balance shall be capable of weighing a 3,500 gram sample in addition to the sample baskets. The furnace shall calculate a temperature compensation factor for the change in weight of the sample basket(s) and provide for the input of a calibration factor for aggregate loss. The furnace shall provide a printed ticket with the initial specimen weight, specimen weight loss, temperature compensation, calibration factor, corrected asphalt content (%), test time, and test temperature. A method for reducing furnace emissions shall be provided. The furnace shall provide an audible alarm and indicator light when the sample weight loss does not exceed 0.02 page 26 Appendix C VDOT and Platinum Performance Partners, LLC

351 Test and Procedures percent of the total sample weight for two consecutive minutes. The furnace door shall be locked until the completion of the test procedure. 4.2 Tempered stainless steel No. 8 (2.36 mm) mesh or otherwise perforated basket(s) with legs. If multiple baskets are used, the baskets shall be nested. The basket(s) shall be provided with screening to confine the aggregate. 4.3 A stainless steel catch pan. 4.4 Oven capable of maintaining 257 ±9 F (125 ±5 C). 4.5 Balance, 8-kg or greater capacity, sensitive to 0.5 g for weighing sample in basket(s). 4.6 Safety Equipment: safety glasses or face shield, high temperature gloves, and long sleeve jacket. Additionally, a heat resistant surface capable of withstanding 1200 F (650 C) and a protective cage capable of surrounding the sample baskets shall be provided. 4.7 Miscellaneous Equipment: pan for transferring samples after ignition, spatulas, bowls, and wire brushes. 5. Sampling A. The test sample shall be the end result of quartering a larger sample taken in accordance with VTM-48 (AASHTO T 248 may be used as a guide to quartering.) Note: VTM-48 is a modified version of AASHTO T 168 B. Preparation of Test Specimens: 5.B.1. If the mixture is not sufficiently soft to separate with a spatula or trowel, place it in a large flat pan and warm to 257 F ±9 F (125 C ± 5 C) for 25 minutes. The sample shall not be heated for more than 1 hour. 5.B.2. The size of the test sample shall be governed by the nominal maximum aggregate size of the mixture and shall conform to the mass requirement shown in Table 1 (Note 1): Note: When the mass of the test specimen exceeds the capacity of the equipment used, the test specimen may be divided into suitable increments, tested, and the results appropriately combined for calculation of the asphalt content (weighted average). VDOT and Platinum Performance Partners, LLC Appendix C page 27

352 Test and Procedures Nominal Maximum Aggregate Size, mm Table 1 Size of Sample Sieve Size Minimum Mass of Sample g 4.75 (No. 4) /8 in ½ in ¾ in in ½ in Sample sizes should not be more than 500 g greater than the minimum recommended sample mass. Large samples of fine mixes tend to result in incomplete ignition of the asphalt. 5.B.3. In addition, a test specimen for moisture determination (VTM-49) will be made as deemed necessary. The specimen used for moisture determination may not be used for asphalt content determination. 6. Calibration A mixture calibration procedure is required. For mix designs containing RAP, sufficient quantity of RAP should be sampled such that the binder content of the RAP may be estimated, and to provide for the RAP to be used in the mix calibration. The binder content of the RAP will be estimated from the average of four samples (RAP only) burned in the furnace. The portions of RAP should be obtained using a sample splitter. Typically, calibration testing will be performed at 1000 F (538 C). However, certain aggregate types may result in an unusually high calibration factor and erroneous gradation results. Such mixes should be calibrated and tested at a lower temperature, typically 900 F (482 C)as approved by the Engineer. A. Calibration Procedure for Hot-Mix Asphalt 6.A.1. This method may be effected by the type of aggregate in the mixture. Accordingly, to optimize accuracy, a calibration factor will be established with the testing of a set of calibration samples for each mix type. This procedure must be performed before any acceptance testing is completed. 6.A.2. Four calibration specimens conforming to the mass requirements of Section shall be prepared at the optimum asphalt content. A butter mix shall be prepared at the design asphalt content, mixed and discarded prior to mixing any of the calibration specimens to ensure an accurate asphalt content. Aggregate used for the calibration specimens shall be sampled from stockpiled material produced in the current construction season. Any method may be used to combine the aggregates, however an additional blank specimen shall be batched and tested according to AASHTO T 30. The washed gradation shall fall within the JMF (mix design) tolerances. Note: When batching calibration samples, be sure to account for the AC% contribution of the RAP to the total asphalt content of the specimens. page 28 Appendix C VDOT and Platinum Performance Partners, LLC

353 Test and Procedures 6.A.3. 6.A.4. 6.A.5. 6.A.6. 6.A.7. 6.A.8. 6.A.9. 6.A A.11. The freshly mixed specimens may be placed directly in the sample basket(s). If allowed to cool, the samples must be preheated in a 257 F (125 C) oven for 25 minutes. Do not preheat the sample basket(s). Ignition furnace: 6.A.4.1. Preheat the ignition furnace to 1000 F (538 C) Record the furnace temperature (set point) prior to the initiation of the test. 6.A.4.2. Enter a calibration factor of 0.00 in the ignition furnace. Weigh and record the weight of the sample basket(s) and catch pan (with guards in place). Place the sample basket in the catch pan. Evenly distribute the calibration specimen in the basket taking care to keep the material away from the edges of the basket. Use a spatula or trowel to level the specimen. When multiple sample baskets are used, place a sample basket in the catch pan. Evenly distribute an equal portion of the specimen in the basket, taking care to keep the material away from the edges of the basket. Each subsequent basket should be placed on top of the preceding basket with an equal portion of the specimen evenly distributed in each basket. Care should be taken to keep the material away from the edges of the baskets. Use a spatula or trowel to level the specimen. Weigh and record the sample, basket(s), catch pan, and basket guards. Calculate and record the initial weight of the sample specimen (total weight - the weight of the sample basket assembly). Note: The initial weight of the sample must check the total intended batch weight within 0.1 percent. Input the initial weight of the sample specimen in whole grams into the ignition furnace controller. Verify that the correct weight has been entered. Open the chamber door and place the sample basket(s) in the furnace. Close the chamber door and verify that the sample weight (including the basket(s) displayed on the furnace scale equals the total weight recorded in Section 6.8 within ± 5g. Differences greater than 5 grams or failure of the furnace scale to stabilize may indicate that the sample basket(s) are contacting the furnace wall. Initiate the test by pressing the start/stop button. This will lock the sample chamber and start the combustion blower. Allow the test to continue until the stable light and audible stable indicator indicates the test is complete. Press the start/stop button. This will unlock the sample chamber and cause the printer to print out the test results. 6.A.12. Open the chamber door, remove the sample basket(s) and allow to cool to room temperature (approx. 30 minutes). 6.A.13. Perform a gradation analysis on the residual aggregate as indicted in Section 8. VDOT and Platinum Performance Partners, LLC Appendix C page 29

354 Test and Procedures 6.A.14. Once all of the calibration specimens have been burned, determine the difference between the actual and measured asphalt contents for each sample. The mix calibration factor is calculated as follows: MCA = AC% test 1 + AC% test 2 + AC% test 3 + AC% test 4 4 where: MCA = Mixture Calibration Average AC % = Difference between actual binder content (including RAP AC%) and measured asphalt content 6.A.15. If the difference between any two asphalt binder contents from the four specimens exceeds 0.15 percent, then discard the high and the low result and report the average MCA resulting from the remaining two specimens. B. Calibration Procedure for Slurry Seal and Micro-surfacing 6.B.1. This method may be affected by the type of aggregate in the mixture. Accordingly, to optimize accuracy, a calibration factor will be established with the testing of a set of calibration samples for each mix type. This procedure must be performed before any acceptance testing is completed. 6.B.2. 6.B.3. 6.B.4. Four calibration specimens conforming to the mass requirements of Section shall be prepared at the optimum asphalt content. The calibration samples will be batched using base asphalt. A butter mix shall be prepared at the design asphalt content, mixed and discarded prior to mixing any of the calibration specimens to ensure an accurate asphalt content. Aggregate used for the calibration specimens shall be sampled from stockpiled material produced in the current construction season. Any method may be used to combine the aggregates, however an additional blank specimen shall be batched and tested according to AASHTO T 30. The washed gradation shall fall within the JMF (mix design) tolerances. The freshly mixed specimens may be placed directly in the sample basket(s). If allowed to cool, the samples must be preheated in a 257 F (125 C) oven for 25 minutes. Do not preheat the sample basket(s). Ignition furnace: 6.B.4.1. Preheat the ignition furnace to 1000 F (538 C). Record the furnace temperature (set point) prior to the initiation of the test. 6.B.4.2. Enter a calibration factor of 0.00 in the ignition furnace. 6.B.5. Weigh and record the weight of the sample basket(s) and catch pan (with guards in place). 6.B.6. 6.B.7. Place the sample basket in the catch pan. Evenly distribute the calibration specimen in the basket taking care to keep the material away from the edges of the basket. Use a spatula or trowel to level the specimen. When multiple sample baskets are used, place a sample basket in the catch pan. Evenly distribute an equal portion of the specimen in the basket, taking care to keep the page 30 Appendix C VDOT and Platinum Performance Partners, LLC

355 Test and Procedures material away from the edges of the basket. Each subsequent basket should be placed on top of the preceding basket with an equal portion of the specimen evenly distributed in each basket. Care should be taken to keep the material away from the edges of the baskets. Use a spatula or trowel to level the specimen. 6.B.8. Weigh and record the sample, basket(s), catch pan, and basket guards. Calculate and record the initial weight of the sample specimen (total weight - the weight of the sample basket assembly). 6.B.9. Input the initial weight of the sample specimen in whole grams into the ignition furnace controller. Verify that the correct weight has been entered. 6.B.10. Open the chamber door and place the sample basket(s) in the furnace. Close the chamber door and verify that the sample weight (including the basket(s) displayed on the furnaces scale equals the total weight recorded in Section 6.8 within ± 5g. Differences greater than 5 grams or failure of the furnace scale to stabilize may indicate that the sample basket(s) are contacting the furnace wall. Initiate the test by pressing the start/stop button. This will lock the sample chamber and start the combustion blower. 6.B.11. Allow the test to continue until the stable light and audible stable indicator indicates the test is complete. Press the start/stop button. This will unlock the sample chamber and cause the printer to print out the test results. Note: Do not use the asphalt content given by the print out. Calculate the measured asphalt content as shown in 6B B.12. Open the chamber door, remove the sample basket(s) and allow to cool to room temperature (approx. 30 minutes). 6.B.13. Weigh and record sample weight. 6.B.14. Calculate measured asphalt content as follows: Measured AC = Weight of sample (before) - Weight of sample (after) Weight of sample (after) 6.B.15. Once all of the callibration specimens have been burned, determine the difference between the actual and measured asphalt contents for each sample. The mix calibration factor is calculated as follows: MCA = AC% test 1 + AC% test 2 + AC% test 3 + AC% test 4 4 where: MCA = Mixture Calibration Average AC % = Difference between actual binder content and measured asphalt content (as determined in ) VDOT and Platinum Performance Partners, LLC Appendix C page 31

356 Test and Procedures 7. Test Procedure 7.A. Hot-Mix Asphalt Mixtures 7.A.1. Preheat the ignition furnace to 1000 F (538 C) Record the furnace temperature (set point) prior to the initiation of the test. 7.A.2. Enter the calibration factor for the specific mix to be tested as determined in Section 6.1 in the ignition furnace. 7.A.3. Weigh and record the weight of the sample basket(s) and catch pan (with guards in place). 7.A.4. Prepare the sample as described in Section 5.2. Place the sample basket in the catch pan. Evenly distribute the specimen in the sample basket taking care to keep the material away from the edges of the basket. Use a spatula or trowel to level the specimen. 7.A.5. When multiple sample baskets are used, place a sample basket in the catch pan. Evenly distribute an equal portion of the specimen in the basket, taking care to keep the material away from the edges of the basket. Each subsequent basket should be placed on top of the preceding basket with an equal portion of the specimen evenly distributed in each basket. Care should be taken to keep the material away from the edges of the baskets. Use a spatula or trowel to level the specimen. 7.A.6. Input the initial weight of the sample specimen in whole grams into the ignition furnace controller. Verify that the correct weight has been entered. 7.A.7. Open the chamber door and place the sample basket(s) in the furnace. Close the chamber door and verify that the sample weight (including the basket(s)) displayed on the furnaces scale equals the total weight recorded in Section 7.8 ± 5g. Differences greater than 5 grams or failure of the furnace scale to stabilize may indicate that the sample basket(s) are contacting the furnace wall. Initiate the test by pressing the start/stop button. This will lock the sample chamber and start the combustion blower. 7.A.8. Allow the test to continue until the stable light and audible stable indicator indicate the test is complete. Press the start/stop button. This will unlock the sample chamber and cause the printer to print out the test results. 7.A.9. Open the chamber door, remove the sample basket(s) and allow to cool to room temperature (approximately 30 minutes). 7.B. Slurry Seal and Micro-surfacing 7.B.1. Cure the material in an oven at 225 F (107 C) until the weight loss in a two hour period does not exceed 0.02% by weight ( i.e. for 5000 gms., the material does not lose more than 1 gm in a two hour period). page 32 Appendix C VDOT and Platinum Performance Partners, LLC

357 Test and Procedures 7.B.2. Preheat the ignition furnace to 1000 F (538 C) Record the furnace temperature (set point) prior to the initiation of the test. 7.B.3. Weigh and record the weight of the sample basket(s) and catch pan (with guards in place). 7.B.4. Prepare the sample as described in Section 5.2. Place the sample basket in the catch pan. Evenly distribute the specimen in the sample basket taking care to keep the material away from the edges of the basket. Use a spatula or trowel to level the specimen. 7.B.5. When multiple sample baskets are used, place a sample basket in the catch pan. Evenly distribute an equal portion of the specimen in the basket, taking care to keep the material away from the edges of the basket. Each subsequent basket should be placed on top of the preceding basket with an equal portion of the specimen evenly distributed in each basket. Care should be taken to keep the material away from the edges of the baskets. Use a spatula or trowel to level the specimen. 7.B.6. Weigh and record the sample, basket(s), catch pan, and basket guards. Calculate and record the initial weight of the sample specimen (total weight - the weight of the sample basket assembly) 7.B.7. Input the initial weight of the sample specimen in whole grams into the ignition furnace controller. Verify that the correct weight has been entered. 7.B.8. Open the chamber door and place the sample basket(s) in the furnace. Close the chamber door and verify that the sample weight (including the basket(s)) displayed on the furnaces scale equals the total weight recorded in Section 7.8 ± 5g. Differences greater than 5 grams or failure of the furnace scale to stabilize may indicate that the sample basket(s) are contacting the furnace wall. Initiate the test by pressing the start/stop button. This will lock the sample chamber and start the combustion blower. 7.B.9. Allow the test to continue until the stable light and audible stable indicator indicate the test is complete. Press the start/stop button. This will unlock the sample chamber and cause the printer to print out the test results. Note: Do not use the asphalt content given by the print out. 7.B.10. Open the chamber door, remove the sample basket(s) and allow to cool to room temperature (approximately 30 minutes). 7.B.11. Weigh and record the sample weight. 7.B.12. Calculate asphalt content using the following: Measured AC = Weight of sample (before) - Weight of sample (after) Weight of sample (after) VDOT and Platinum Performance Partners, LLC Appendix C page 33

358 Test and Procedures 7.B.13. Calculate actual asphalt contact using the following: Actual AC = Measured AC MCA 7.B.14. Report Actual AC. 8. Gradation 8.1. Allow the specimen to cool to room temperature in the sample basket(s) Empty the contents of the basket(s) into a flat pan. Use a small wire sieve brush to ensure that any residual fines are removed from the basket(s) Perform the gradation analysis according to AASHTO T Report 9.1. Always report corrected asphalt content, mix calibration factor, temperature compensation factor, total percent loss, sample mass, and test temperature. Attach the original printed ticket to the report. An example data sheet is attached. 10. Precision and Bias Precision and Bias were determined in an NCAT Round-Robin study for surface mixes. Asphalt Content Standard Deviation, % Acceptable Range of Two Test Results (%) Single-Operator Precision Multi laboratory Precision Note: These precision statements are based on 4 aggregate types, 4 replicates, and 12 laboratories participating with 0 laboratory results deleted as outlying observations. All 4 aggregates were tested in surface mixes and had relatively low absorption values. page 34 Appendix C VDOT and Platinum Performance Partners, LLC

359 MCS: Asphalt Plant Certification D Lime Safety Precautions Hydrated lime (calcium hydroxide), like most materials or chemicals in common use, is not dangerous to work with as long as a few simple precautions are exercised. Quicklime (calcium oxide), also called hot lime, is considerably more dangerous to use than hydrated lime. While both types of lime are strongly alkaline, quicklime is much more caustic and can produce severe burns quickly when it comes in contact with moist skin. Prevent hydrated lime from coming into contact with workers skin, to the extent possible. Danger from severe burns is remote. However, prolonged contact of hydrated lime with a perspiring workers skin has produced bad burns, especially where the skin is also chafed by tight clothing. Additionally, people with particularly sensitive skin have developed forms of skin irritation (dermatitis) through prolonged contact. There is no urgency in removing hydrated lime from skin, but it should be flushed off with water as soon as convenient. Quicklime, which is caustic, should be washed off or at least brushed off immediately after contact with skin. Hot, humid weather conditions tend to heighten the caustic effect of hydrated lime on a worker s skin. If the following recommendations are carried out, there is no possibility of burns or skin irritation to workers: Clothing 1. Wear at least one long-sleeved shirt or sweat shirt. Rolled up sleeves or short-sleeved shirts should not be permitted. In cool weather, a second long sleeved shirt provides added protection. 2. Wear high top shoes or laced boots. 3. Wear trouser legs tied over shoe tops. (Shorts should not be permitted). 4. Wear a hat or cap to protect the scalp from accumulated lime dust. 5. Wear gauntlet-type gloves. 6. Do not wear clothes that bind too tightly around neck or wrists, since the resulting chafing may cause lime to be more irritating to skin. VDOT and Platinum Performance Partners, LLC Appendix D page 1

360 Lime Safety Precautions Protective Cream A protective cream, like West s #311 Cream, should be applied to exposed parts of the body, like neck, face, wrists, or ankles when a worker will be exposed to prolonged lime dust. Properly applied, it makes a thin, protective film which is easily removed by soap and water. Eye Protection Wear safety glasses with side shields, or goggles, at all times while working with lime. All workers emptying bags of lime must be equipped with close-fitting goggles. If a worker in a bent-over position should drop an open bag of lime on the ground, the impact can cause a dense cloud of lime dust to arise directly on the worker s face. If his eyes are unprotected by goggles, loss of sight may result from lime burns. Mouth and Nose Protection When construction conditions are quite dusty, a light-weight filter mask should be worn, although inhalation of some lime dust is not injurious. After Work Bathe or shower after a workday to cleanse the body entirely of lime and protective cream. First Aid 1. Skin burns Wash thoroughly with soap and warm water to remove all lime. Apply a standard burn ointment used for heat or caustic burns, and cover with sterile bandages. Keep bandaged during healing to prevent infection. 2. Lime in the Eyes Hold worker s eye open and flush out with cool, clean water immediately for at least 15 minutes. Hold the head under the tap or pour water into the eye using a clean container and keep the eye open as widely as possible during flooding. 3. Medical Attention Report all burns from lime or cases of lime in eyes immediately, so that medical attention can be provided without delay. Prevention Prevention is the key to safety. All Contractors should have Lime Safety Precautions and should: Carefully brief each worker on lime precautions Check to ensure that the workers abide by these few simple safety rules. The workers most vulnerable to lime burns, and who should practice the above precautions most rigorously, are those handling bagged lime on the roadway and those operating bulk spreader trucks. In general, greater care should be exercised in bag applications than bulk. The least hazard from lime burns is encountered in slurry applications. Only workers with unusually sensitive skins could be adversely affected by slurry (or the thick whitewash ) splashing on their bare skin. But the same rigid care should be exercised to prevent any form of lime from getting into the eyes. Practically speaking, hydrated lime or slurry is no more dangerous to the skin than cement or grout. Lime is simply lighter and finer than cement and more prone to blow. The above precautions are largely intended for those contractors who are using lime for the first time. Most contractors experienced with lime have never had trouble from burns. Page 2 Appendix D VDOT and Platinum Performance Partners, LLC

361 MCS: Asphalt Plant Certification E Proficiency Tests AASHTO T30 Mechanical Analysis of Extracted Aggregates AASHTO T166 Bulk Specific Gravity AASHTO T209 Maximum Specific Gravity AASHTO T269 Percent Air Voids VTM Asphalt Content by Ignition * AASHTO T312 Preparing & Determining Density of HMA Specimens by Gyratory Compactor ** AWARENESS/IMPORTANT *No demonstration of Oven Calibration Factor Procedure required for Asphalt Plant Level I certification. **No demonstration of Preparation of Mixture - Lab Prepared Specimens required for Asphalt Plant Level I certification. VDOT and Platinum Performance Partners, LLC Appendix E page 1

362 Appendix E Proficiency Tests Mechanical Analysis of Extracted Aggregate AASHTO T30 (1998) 1. Equipment a. Nest of Sieves: upper sieve No. 10 or 16 (2.00 or 1.18mm) sieve. lower sieve a No. 200 (0.075mm) sieve b. Oven or hot plate capable of maintaining 230 ± 9 F (110 ± 5 C) c. Balance capable of weighing to 0.1% of sample mass d. Woven wire- cloth sieves conforming requirements of M Procedure a. Sample consisting of all aggregate after extraction b. Minimum mass of mix sample based on nominal maximum size c. Sample placed in container and covered with water d. Wetting agent added e. Contents agitated vigorously f. Wash water poured through nest of sieves Washing continued until wash water is clear g. Material placed in pan h. Material dried to constant mass at 230 ± 9 F i. Material weighed to nearest 0.1 percent j. Material sieved on specified sieve sizes j.1. Sieving continued until not more than 0.5 percent by mass of total sample passes a given sieve in 1 minute k. Each fraction of aggregate weighted l. Summation of aggregate mass check total washed dry mass within 0.2 percent? page 2 Appendix E VDOT and Platinum Performance Partners, LLC

363 Appendix E Proficiency Tests Bulk Specific Gravity of Compacted Bituminous Mixtures Using Saturated Surface-Dry Specimens AASHTO T Method A 1. Equipment a. Balance and Suspension: 1. Conforms to M231 for class required for principle sample mass of samples tested 2. Suspension from center of balance pan 3. Suspension wire of smallest practical size 4. Holder and sample completely immersed 5. No trapped air bubbles exist under specimen 6. Can determine constant mass of specimen to 0.1 percent b. Water Bath: 1. Equipped with overflow outlet 2. Deep enough to completely immerse holder and sample c. Room Temperature: 2. Procedure 1. Room temperature 77 ± 9 F (25 ± 5 C). a. Molded specimens cooled to room temperature and weighed. b. Mass of dry sample in air determined in grams. c. Sample immersed in water bath. c.1. Immersed for 4± 1 minutes c.2. Water at 77± 1.8 F (25 ± 1 C) c.3. Specimen water height recorded for each specimen d. Sample removed and blotted with damp towel e. Saturated surface-dry mass determined f. Percent water absorbed determined to be less than 2 percent g. Bulk specific gravity calculated A/(B-C) h. Bulk specific gravity reported to nearest VDOT and Platinum Performance Partners, LLC Appendix E page 3

364 Appendix E Proficiency Tests Maximum Specific Gravity of Bituminous Mixtures AASHTO T Flask or bowl calibrated a. Bowl weighed suspended in water after 10 ± 1 minutes 2. Sample obtained by splitting or quartering 3. Mass of sample as follows (samples larger than the capacity of the container may be divided into suitable increments, tested and the results averaged). Largest Particle Size Minimum Sample Size (g) 4. Particles of sample separated 2 in (50 mm) /2 in (37.5 mm) in (25 mm) /4 in (19 mm) /2 in (12.5 mm) /8 in (9.5 mm) 1000 No. 4 (4.75 mm) Care used not to fracture mineral fragments 6. After separating, fine aggregate particles not larger than ¼ in (6.3 mm) 7. Sample at room temperature 8. Bowl weighed in air 9. Sample placed in flask or bowl and weighed 10. Water at approximately 77 F (25 C) added to cover sample 11. Vacuum increased until manometer reads ± 2.25 mm Hg 12. Entrapped air removed using partial pressure for 15 ± 2 minutes 13. Container and contents agitated vigorously by mechanical device or manual shaking at intervals of 2 minutes 14. Release of entrapped air facilitated by addition of wetting agent. (optional) 15. Release of vacuum by increasing pressure at a rate not exceeding 8 kpa per second 16. Bowl and contents immersed in water for 10 ± 1 minutes 17. Weight recorded 18. Maximum specific gravity calculated and reported to nearest Max. specific gravity = (C-A) / (C-A)(D-B) page 4 Appendix E VDOT and Platinum Performance Partners, LLC

365 Appendix E Proficiency Tests Percent Air Voids in Compacted Specimens AASHTO T Bulk specific gravity determined according to AASHTO T Maximum specific gravity determined according to AASHTO T Percent air voids calculated in accordance with the following: Percent air voids = 100 x (1-(Gmb/ Gmm)) VDOT and Platinum Performance Partners, LLC Appendix E page 5

366 Appendix E Proficiency Tests Ignition Method Virginia Test Method 102 (VTM-102) 1. Ignition Oven Calibration Factor Procedure (Not required for Level I) 2. Sample Preparation a. If necessary, mixture warmed in pan (221 ± 9 F) to constant weight b. Sample obtained by splitting or quartering c. Size of Sample Nominal Maximum Aggregate Size Minimum Sample Mass in grams 1-1/2 in 4000* 1 in 3000* 3/4 in /2 in /8 in 1200 No * Sample may be split and results combined using weighted average d. Sample baskets tared and weight recorded e. Sample divided into equal portions for top and bottom basket f. Baskets set in drip pan when loading and care taken not to lose fines g. Sample spread with heated spatula into thin even lift 3. Determination of Asphalt Content by Ignition Method a. Furnace preheated to 538 C (1000 F) b. Correction factor for specific gravity entered c. Sample weight entered and recorded to nearest gram d. Initial sample weight entered and verified in furnace controller e. Sample loaded into furnace and total weight (including baskets) verified prior to initiation of test f. Proper safety equipment worn when loading sample g. Sample removed promptly when audible stable indicator indicates constant weigh achieved page 6 Appendix E VDOT and Platinum Performance Partners, LLC

367 Appendix E Proficiency Tests h. Proper safety equipment worn when removing sample i. Sample allowed to cool to room temperature in safety enclosure 4. Gradation Determination a. Entire contents of sample baskets and drip pan emptied into flat pan, sample baskets cleaned into flat pan with a wire brush b. Sample weight determined to nearest 0.1 percent (1 gram for sample sizes greater than 1000 grams) for gradation c. Gradation analysis performed in accordance with AASHTO T30 VDOT and Platinum Performance Partners, LLC Appendix E page 7

368 Appendix E Proficiency Tests Standard Method for Preparing & Determining the Density of Hot-Mix Asphalt (HMA) Specimens by Means of the Superpave Gyratory Compactor AASHTO T 312 (Was AASHTO TP 4) 1. Gyratory Compactor a. One from approved list 2. Molds a. Inside diameter to mm b. At least 250 mm high c. Walls at least 7.5 mm thick 3. Ram and base plate faces a. Ground flat b. Diameter of to mm 4. Balance - G5 readable to 1 gram 5. Forced draft oven thermostatically controlled to ± 3 C 6. Thermometers armored, glass or dial-type with metal stems 7. Verification of calibration (following items checked periodically) a. Ram pressure b. Angle of gyration c. Gyration frequency d. LVDT or other continuous height recorder e. Mold dimensions f. Plate faces g. Oven temperature 8. Preparation of Apparatus a. Main power switch turned on for required warm up period page 8 Appendix E VDOT and Platinum Performance Partners, LLC

369 Appendix E Proficiency Tests b. Angle, pressure and gyration level set c. Bearing surfaces lubricated per manufacturer s instruction 9. Preparation of Mixture Lab Prepared Specimens (Not required for Level I) 10. Preparation of Mixture - Field prepared samples a. Loose mix brought to compaction temperature by uniform heating 11. Compaction of Specimens a. Mold, base plate, and upper plate (when required) removed from oven and paper disk placed on bottom of mold b. Mixture placed in mold in one lift, leveled and paper disk and upper plate (when required) added c. Mold loaded into compactor and compaction started. (recorded to nearest 0.1 mm) d. Compactor shuts off when completed e. Mold removed and specimen extruded f. Paper disks removed g. Specimens conform to height requirements of 115 ± 5 mm VDOT and Platinum Performance Partners, LLC Appendix E page 9

370 Appendix E Proficiency Tests This page is blank intentionally page 10 Appendix E VDOT and Platinum Performance Partners, LLC

371 MCS: Asphalt Plant Certification F Study Question & Answers This appendix contains study questions and problems from Chapters 3-10, along with answers and details on how problems were solved. (There are no study questions for Chapters 1 and 2.) Use this appendix to check yourself and your learning. For multiple choice and true/false answers, the answers appear on the right, enabling you to cover the answer and reveal it after you have made your selection. VDOT and Platinum Performance Partners, LLC Appendix F page 1

372 Study Question and Answers Chapter Three: Components of Asphalt Concrete 1. A method of classification used to determine the performance properties of binder is: D. Performance grading 2. Binder blended with a kerosene-type material is known as: C. MC asphalt 3. A method of determining flow properties of binder is: B. Viscosity 4. Binder which has been liquefied with heat, petroleum solvents, or emulsified with water, is known as: B. Liquid asphalt 5. Binder blended with a naphtha or gasoline-type material is called: D. RC asphalt 6. An example of an artificial aggregate is blast furnace slag. A. True 7. Aggregates should be handled and stockpiled in such a manner as to minimize: B. Segregation 8. Hot-mix asphalt concrete can be considered to be made up of two ingredients: B. Binder and aggregates 9. A suspension of binder in water containing an emulsifying agent, such as soap, is called: D. Emulsified asphalt 10. Asphalt binders become harder (more viscous) as their temperature decreases and softer (less viscous) as their temperature increases A. True 11. How should the site for stockpiles be prepared? The stockpile site should be on ground that is denuded of vegetation, hard, well drained or otherwise prepared to protect the aggregate from contamination. Page 2 Appendix F VDOT and Platinum Performance Partners, LLC

373 Study Question and Answers 12. How should stockpiles be handled? Aggregates shall be handled, hauled and stored in a manner that will minimize segregation and avoid contamination. 13. How much material should be on hand before starting daily operations? Enough to ensure continued processing for the working day. VDOT and Platinum Performance Partners, LLC Appendix F page 3

374 Study Question and Answers Chapter Four: Asphalt Concrete Mixtures 1. The frictional resistance of the surface of the pavement to insure safe driving and stopping of the vehicle is called: D. Skid-resistance 2. The ability of the asphalt pavement to withstand repeated flexing or slight bending caused by the passage of wheel loads is called: B. Fatigue resistance 3. The resistance of pavement to the effects of traffic, water, air, and temperature changes is known as: A. Durability 4. The ability of a pavement to adjust itself to settlement of the base without cracking is known as: D. Flexibility 5. The ease with which the material can be placed to the desired uniformity and compacted to the required density is known as: C. Workability 6. Type SM-12.5A asphalt concrete is a: B. Surface course mix 7. Four physical properties that are required of asphalt concrete mixtures are: D. Stability, flexibility, durability, and resistance to skidding 8. Type IM-19.0A asphalt concrete is: C. Intermediate course mix 9. The resistance an asphalt concrete pavement has to the passage of air and water into or through the pavement is known as: C. Impermeability 10. Type BM-25.0 asphalt concrete is a: A. Base course mix 11. The upper or top layer of an asphalt concrete pavement structure is the: B. Surface course 12. The subgrade ultimately carries all traffic loads. A. True Page 4 Appendix F VDOT and Platinum Performance Partners, LLC

375 Study Question and Answers 13. The main structural strength element of a pavement is the: B. Base course 14. The layer of an asphalt concrete pavement that distributes traffic loads to the subgrade is the: C. Base course 15. Stability may be improved by using aggregates with rough surface texture. A. True VDOT and Platinum Performance Partners, LLC Appendix F page 5

376 Study Question and Answers Chapter Five: Asphalt Concrete Plants 1. The overflow chutes on a batch plant are used to: B. Prevent contamination by intermingling from adjacent bins 2. The asphalt material shall be delivered into the mixer in a thin, uniform sheet or multiple streams for the full width of the mixer. A. True 3. Increasing the dryer time will remove more moisture than increasing the heat. A. True 4. The asphalt content for batch weight calculations is obtained from the: B. Job mix formula 5. During the drying operation, wet aggregate will reduce the dryer s capacity. A. True 6. In the drum mix plant, moisture content of aggregate must be determined before drying. A. True 7. The maximum amount of moisture allowed in the completed mixture is: B. 1% 8. What conditions affect screening efficiency? (1) Condition and cleanliness of screens (2) Excessive material being fed to screens (3) Excessive wearing causing enlarged openings (4) Screen not properly installed 9. What are some of the methods of controlling carry-over? (1) Cleaning the screens (2) Regulating the quantity of material coming from the cold feed (3) Daily visual inspection of the screens for defects Page 6 Appendix F VDOT and Platinum Performance Partners, LLC

377 Study Question and Answers 10. What is meant by proportioning of aggregates and asphalt? Blending of the correct amount of each size aggregate and the correct amount of asphalt to produce the required mix. 11. What conditions will best insure a uniform flow of the proper aggregate sizes from the cold feed? (1) Correct sizes of aggregates in the stockpile (2) Segregation should be prevented (3) Intermixing of stockpiles should be prevented (4) Feeder gates should be accurately calibrated, set and secured (5) Gates should be kept clear of obstruction (6) Excessive arching in the fine aggregates should not be allowed 12. Why is proper cold feeding essential? (1) A sudden rush of cold sand may cause a considerable change of temperature in the aggregate leaving the dryer (2) A sudden increase in the cold feed can overflow the screens (3) Erratic feeding may cause some bins to overfill while starving others 13. When hydrated lime is used in asphalt concrete as an anti-stripping additive, it shall be added at what rate? Not less than one percent by weight of the total dry aggregate 14. What problems arise from overheating? The asphalt can be damaged 15. What problems arise from underheating aggregate? (1) Aggregate is difficult to coat (2) Mix is difficult to place (3) Aggregate may not be dry enough 16. What could cause leakage of aggregate into the weigh hopper after the desired amount has been withdrawn? Worn gates on the bottom of the bins. 17. How often and by whom should hopper and truck scales be serviced and tested? At least every six months by a scale service representative. VDOT and Platinum Performance Partners, LLC Appendix F page 7

378 Study Question and Answers 18. How often and by whom shall scales used in the weighing of materials paid for on a tonnage basis be approved and sealed? Every six months and upon being moved The Bureau of Weights and Measures approves and seals 19. When using a metering device instead of a weigh bucket for proportioning asphalt to the mixer, what is one important thing that should be remembered? The metering device shall be calibrated for accuracy. 20. What is the maximum dry mixing time for aggregates released into the pugmill? Fifteen (15) seconds 21. What is the minimum wet mixing time allowed? Twenty (20) seconds 22. Who determines the mixing time? Who approves the mixing time? The Producer s technician determines the mixing time. Approval is by the District Materials Engineer. 23. Asphalt storage at the plant should be equal to at least: B. One day s output Problem No. 1 Answers: Establishing the Wet Mixing Time Given: The plant is operating on a 22-second wet mixing cycle. Two previous determinations yielded results of 94.3% and 95.1% completely coated particles. The third determination has shown that of the 230 particles there are 6 that are not completely coated. Find: 1. The Ross Count for the third determination. Ross Count = Number of Completely Coated Particles X 100 Total Number of Particles Step 1) = 224 Step 2) 224 X Step 3) X 100 = 97.4% Page 8 Appendix F VDOT and Platinum Performance Partners, LLC

379 Study Question and Answers 2. Does this meet the VDOT requirements for the wet mixing time? Yes Step 1) = Step 2) X What steps are taken if after conducting a Ross Count, the results do not meet VDOT requirements? A. Increase the mixing time 5 seconds and repeat test. B. Does not meet requirements if an average of 3 samples is less than 95% or one sample is less than 92%. Problem No. 2 Answers: Establishing the Wet Mixing Time Given: The plant is operating on a 21-second wet mixing cycle. Two previous determinations yielded results of 95.3% and 92.5% completely coated particles. The third determination has shown that of the 216 particles there are 14 that are not completely coated. Find: 1. The Ross Count for the third determination. 93.5% Ross Count = Number of Completely Coated Particles X 100 Total Number of Particles Step 1) = 202 Step 2) X 100 Step 3) x 100 = 93.5% 2. Does this meet the VDOT requirements for the wet mixing time? No Step 1) = Step 2) X 93.8% VDOT and Platinum Performance Partners, LLC Appendix F page 9

380 Study Question and Answers 3. What steps are taken if after conducting a Ross Count, the results do not meet VDOT requirements? A. Increase the mixing time 5 seconds and repeat test. B. Does not meet requirements if an average of 3 samples is less than 95% or one sample is less than 92%. Problem No. 3 Answers: Determining Aggregate Moisture Determine the percent moisture in an aggregate sample that had a wet weight of 1335 grams, and after drying, a dry weight of 1290 grams. (Answer to nearest tenth of a percent.) % Moisture = Wet Weight Dry Weight X 100 Dry Weight Step 1) Step 2) X X Step 3) x 100 = 3.5% Problem No. 4 Answers: Determining Aggregate Moisture Determine the percent moisture in an aggregate sample that had a wet weight of 1275 grams, and after drying, a dry weight of 1235 grams. (Answer to nearest tenth of a percent.) % Moisture = Wet Weight Dry Weight X 100 Dry Weight Step 1) Step 2) X X Step 3) x 100 = 3.2% Page 10 Appendix F VDOT and Platinum Performance Partners, LLC

381 Study Question and Answers Problem No. 5 Answers: Determining Moisture of an Asphalt Mixture Given the Following information, determine the percent moisture in the BM-25.0 asphalt concrete sample below. Does this meet the VDOT Specifications? Yes Weight of Moist Sample = 2254 Weight of Dry Sample = 2232 % Moisture = Wet Weight Dry Weight X 100 Dry Weight Step 1) Step 2) X 100 X 100 Step 3) x 100 = 0.99 or 1.0% The moisture content of an asphalt mixture should not exceed 1% Problem No. 6 Answers: Determining Moisture of an Asphalt Mixture Given the following information, determine the percent moisture in the BM-25.0 asphalt concrete sample below. Does this meet the VDOT Specifications? No Weight of Moist Sample = 2376 Weight of Dry Sample = 2342 % Moisture = Wet Weight Dry Weight X 100 Dry Weight Step 1) X 100 Step 2) X 100 Step 3) x 100 = 1.45 or 1.5% The moisture content of an asphalt mixture should not exceed 1% VDOT and Platinum Performance Partners, LLC Appendix F page 11

382 Study Question and Answers Chapter Six: Sampling and Analysis of Aggregates 1. A process in which an aggregate is separated into its various sizes by passing it through screens of various size openings for the purpose of determining the distribution and particle size is: B. Sieve analysis 2. Coarse aggregate used in Asphalt Concrete is defined as all the material retained on or above the: A. No.4 (4.75 mm) sieve 3. A relatively small portion of material having the same physical properties as the group or lot from which it is taken is called a: B. Representative sample 4. Fine aggregate used in Asphalt Concrete is defined as all the material passing the: A. No. 4 (4.75 mm) sieve 5. What is the most important thing in sampling of materials? Obtaining the average gradation of a material. 6. What determines the size sample required to run a sieve analysis? The size of the sample will vary according to the aggregate size; the larger the aggregate size, the larger the sample would have to be to remain a representative sample. 7. What are two methods of reducing an aggregate sample to size for testing? (1) Sample splitter (2) Quartering 8. How would you prepare a sample for sieve analysis? 1) Reduce sample to proper size by splitting or quartering 2) Dry thoroughly 3) Weigh and record total dry weight of sample before washing 9. Washed sieve analysis is a method used in Virginia for asphalt mixes for determining proportions of various particle sizes in a mineral aggregate. A. True Page 12 Appendix F VDOT and Platinum Performance Partners, LLC

383 Study Question and Answers 10. The purpose of the washed sieve analysis is to separate the amount of material finer than what size sieve? No. 200 (75μm) sieve 11. Which dry weight is used to calculate the percent retained? A. Total dry weight of sample before washing 12. As a check against sample loss when running a sieve analysis, the combined grams on each individual sieve, in the weight retained column, should equal the: B. Dry weight of sample after washing 13. How are the different sizes of aggregate in a sample separated? By using the correct sieves selected for compliance with the specification. 14. When conducting a sieve analysis, after the total sample has been shaken, the weight of material retained on each sieve size is recorded. A. True Problem No. 1 Answers: Determining Gradation Complete the following analysis. Total dry weight of aggregate before washing Dry weight of aggregate after washing grams grams Sieve Wt. Retained on each sieve % Retained % Passing 3/4 in /2 in /8 in No No No No No Pan 3.1 Percent Retained= Wt. on the sieve Total dry wt. of sample X 100 VDOT and Platinum Performance Partners, LLC Appendix F page 13

384 Study Question and Answers No 4) X 100 = 0.1 No 8) X 100 = 9.5 No 30) X 100 = 45.1 No 50) X 100 = 33.8 No X 100 = 9.9 Total percent passing each sieve Problem No. 2 Answers: Determining Gradation Complete the following analysis. Total dry weight of aggregate before washing Dry weight of aggregate after washing grams grams Sieve Wt. Retained on each sieve % Retained % Passing 3/4 in /2 in /8 in No No No No No Pan 22.7 Percent Retained= Wt. on the sieve X 100 Total dry wt. of sample Page 14 Appendix F VDOT and Platinum Performance Partners, LLC

385 Study Question and Answers No 4) X 100 = 1.1 No 8) X 100 = 25.7 No 30) X 100 = 36.1 No 50) X 100 = 11.7 No X 100 = 13.9 Total percent passing each sieve Problem No. 3 Answers: Determining Gradation Total dry weight of aggregate before washing Dry weight of aggregate after washing grams grams Sieve Wt. Retained on each sieve % Retained % Passing 2 in ½ in in /4 in /2 in /8 in No No No No No No Percent Retained= Wt. on the sieve Total dry wt. of sample X 100 VDOT and Platinum Performance Partners, LLC Appendix F page 15

386 Study Question and Answers 1 inch) X 100 = 8.1 3/4 inch) X 100 = /2 inch) X 100 = /8 inch) X 100 = 7.7 No. 4) X 100 = 19.9 No. 8) X 100 = 18.5 No. 30) X 100 = 11.0 No. 50) X 100 = 4.5 No. 100) X 100 = 1.5 No. 200) X 100 = 0.8 Total percent passing each sieve Problem No. 4 Answers: Determining Gradation Mix Type: SM-12.5E Total dry weight of aggregate before washing Dry weight of aggregate after washing grams grams Sieve Wt. Retained on each sieve % Retained % Passing 2 in ½ in in /4 in /2 in /8 in No No No No No No Page 16 Appendix F VDOT and Platinum Performance Partners, LLC

387 Study Question and Answers Percent Retained= Wt. on the sieve Total dry wt. of sample X 100 1/2 inch) X 100 = 1.2 3/8 inch) X 100 = 9.5 No. 4) X 100 = 28.4 No. 8) X 100 = 11.7 No. 30) X 100 = 27.9 No. 50) X 100 = 9.6 No. 100) X 100 = 4.0 No. 200) X 100 = 2.2 Total percent passing each sieve VDOT and Platinum Performance Partners, LLC Appendix F page 17

388 Study Question and Answers Problem No. 5 Answers: Determining Gradation Determine the gradation of the extracted aggregate (answer to the nearest tenth of a percent) for the following asphalt concrete mixture. Mix Type: SM 12.5D Total dry weight of aggregate before washing Dry weight of aggregate after washing grams grams Sieve Wt. Retained on each sieve % Retained % Passing 2 in 1 ½ in 1 in 3/4 in /2 in /8 in No No No No No No Percent Retained= Wt. on the sieve Total dry wt. of sample X 100 Page 18 Appendix F VDOT and Platinum Performance Partners, LLC

389 Study Question and Answers Chapter Seven: Blending Aggregates 1. Where are the design range limits found for the different types of asphalt concrete mixtures? VDOT Road and Bridge Specifications Book, Section Job Mix Formula Table II If the job mix on the 1/2 inch (12.5 mm) sieve is 81% passing, what is the acceptance range for the 8 tests? Section Table II-15 (± 2.8) To whom should the job-mix be submitted? Section The Engineer (the District Materials Engineer) 4. The range from which the job mix is chosen is called: B. Design range 5. The Trial and Error method is commonly used to determine the relative proportions of different aggregates needed to produce a final gradation that meets specifications. A. True 6. The target values for the combined gradation are provided by: C. The Asphalt Mix Design Technician Problem No. 1 Answers: Cold Feed Blending Worksheet Determine the Job Mix Formula (Total Blend) Type Mix: SM-12.5A Mat l % Used Screenings Stone Sieve (in) % Pass % Blend % Pass % Blend Total Blend Target Value Design Range 1 1/2 in 1 in 3/4 in /2 in /8 in max No. 4 No No. 30 No. 50 No This is just one example of blending choices. VDOT and Platinum Performance Partners, LLC Appendix F page 19

390 Study Question and Answers Problem No. 2 Answers: Cold Feed Blending Worksheet Determine the Job-Mix Formula (Total Blend) Type Mix: IM-19.0D Mat l % Used No. 10 1/2 Cr/ Run No Sieve (in) % Pass % Blend % Pass % Blend % Pass % Blend Total Blend Target Value Design Range 1 1/2 in 1 in /4 in /2 in max 3/8 in No. 4 No No. 30 No. 50 No This is just one example of blending choices. Problem No. 3 Answers: Cold Feed Blending Worksheet Determine the Job-Mix Formula (Total Blend) Type Mix: Mat l % Used SM-12.5D No. 78 No. 10 Sand Sieve (in) % Pass % Blend % Pass % Blend % Pass % Blend Total Blend Target Value Design Range 1 1/2 in 1 in 3/4 in /2 in /8 in max No. 4 No No. 30 No. 50 No This is just one example of blending choices Page 20 Appendix F VDOT and Platinum Performance Partners, LLC

391 Study Question and Answers Problem No. 4 Answers: Hot Bins Blending Worksheet Batch Plant set up: A. Determination of hot bin proportions. 1. Determine the percentage to be pulled from each bin to meet the job mix formula. 2. Show blend determined under column listed total blend. 3. Show acceptance range in column listed acceptance range. Determine the Job-Mix Formula (Total Blend) Type Mix: BM-25.0 Bin No. Bin 1 Bin 2 Bin 3 Bin 4 % Used Sieve (in) % Pass % Blend % Pass % Blend % Pass % Blend % Pass % Blend Total Blend Job-Mix Formula Accept Range 1 1/2 in in /4 in /2 in 3/8 in No. 4 No No. 30 No. 50 No B. Using the percentage determined to be pulled from each bin above and an asphalt content of 4.5%, calculate the weight of asphalt, weight of aggregates from each bin, and accumulative weights per bin to be pulled in an 8000 pound batch. Bins Percent Weight of Aggregates per Bin Accumulative Weights per Bin Bin Bin Bin Bin Weight of Asphalt 360 VDOT and Platinum Performance Partners, LLC Appendix F page 21

392 Study Question and Answers Problem 5 Answers: Hot Bin Blending Worksheet Batch Plant set up: A. Determination of hot bin proportions. 1. Determine the percentage to be pulled from each bin to meet the job mix formula. 2. Show blend determined under column listed total blend. 3. Show acceptance range in column listed acceptance range. Determine the Job-Mix Formula (Total Blend) Type Mix: IM-19.0 A Bin No. Bin 1 Bin 2 Bin 3 Bin 4 % Used Sieve (in) % Pass % Blend % Pass % Blend % Pass % Blend % Pass % Blend Total Blend Job-Mix Formula Accept Range 1 1/2 in 1 in /4 in /2 in /8 in No. 4 No No. 30 No. 50 No B. Using the percentage determined to be pulled from each bin above and an asphalt content of 4.7%, calculate the weight of asphalt, weight of aggregates from each bin, and accumulative weights per bin to be pulled in a 5500 pound batch. Bins Percent Weight of Aggregates per Bin Accumulative Weights per Bin Bin Bin Bin Bin Weight of Asphalt 259 Page 22 Appendix F VDOT and Platinum Performance Partners, LLC

393 Study Question and Answers Chapter Eight: Duties of the Technician 1. Who is responsible for the submission of the job mix formula? B. Asphalt Contractor/Technician 2. Who approves the job-mix formula? C. District Materials Engineer 3. Whose responsibility is it to assure that all materials are properly handled and stored? A. Asphalt Mix Design Contractor/Technician 4. Asphalt cement used for state work must be certified or tested. A. True 5. Whose responsibility is it to sample, make proportioning determinations and to make all adjustments necessary to insure proper operational control? B. Contractor s Asphalt Mix Design Technician 6. A chart that shall be set up to alert the Producer when to investigate his process is known as the: B. Control chart 7. Samples taken from equal portions of a lot at locations which have been selected solely by chance are known as: C. Stratified random samples 8. A method to re-evaluate asphalt concrete when there is doubt that the original test results are valid is known as the: B. Referee system 9. Where should monitor samples be taken? B. At the plant 10. Monitor samples are taken by the Producer s Certified Asphalt Concrete Plant Technician in the presence of the District Monitor. A. True 11. What is the maximum time required after production starts before taking the first sample? No time limit 12. What procedure should be used when two samples are randomly selected to be taken from one truckload of material? Discard the second number and draw again. VDOT and Platinum Performance Partners, LLC Appendix F page 23

394 Study Question and Answers 13. How should the sample be taken from the truck? Take the sample from the approximate center of the truckload. Strike off the top 6 inches of material and take the sample horizontally, 6-12 inches below the surface of the load. 14. What is the normal size of a lot? 4000 tons 15. What is the difference between random sampling and representative sampling? Random samples are selected solely by chance. A representative sample is selected by trying to sample the average of the material. 16. In stratified random sampling, what would be the number of samples required per 4000 ton lot? 8 samples per 4000 ton lot Page 24 Appendix F VDOT and Platinum Performance Partners, LLC

395 Study Question and Answers Chapter Nine: Testing of Asphalt Concrete 1. The Ignition Method test utilizes a sample of Asphalt Concrete taken from the truck. A. True 2. The Ignition Oven is the method used to determine the asphalt content in asphalt mixtures. A. True 3. The Virginia test method for determining the Percent Binder or Asphalt Content in asphalt mixtures is the centrifuge method. B. False 4. The actual test sample of an asphalt mixture used in the Ignition Oven shall be a minimum of 1500 grams for an SM- 12.5A mix. A. True 5. What is the purpose of the Ignition Method? To determine the asphalt content for a mixture and recover aggregate for the sieve analysis 6. Specifications allow what percent voids in the total mix for an SM-12.5A? percent 7. VFA are voids in a filler aggregate in asphalt mixtures. B. False 8. VMA are voids in a mineral aggregate. A. True 9. Asphalt test procedures can be found in the appropriate AASHTO procedure or Virginia Test Method (VTM). A. True 10. is added to asphalt as an anti-stripping agent. Hydrated lime 11. The Test checks the effectiveness of an anti-stripping additive. Boil VDOT and Platinum Performance Partners, LLC Appendix F page 25

396 Study Question and Answers Problem No. 1 Answers: Volumetric Calculations The results of laboratory testing of a SM-9.5A yielded the following results: Asphalt Content = 5.05 Correction Factor =.017 Asphalt Binder Specific Gravity = Percent minus 200 = Complete the following tables: Maximum Specific Gravity of Mix (G mm ): = ( ) ( ) Variables Grams Mass Container in Air A Mass Container in Water B Mass Container and Sample in Air C Mass Container and Sample in Water D Maximum Specific Gravity (G mm ) = = ( ) ( ) Bulk Specific Gravity of Mix (G mb ): Variables Specimen 1 Specimen 2 Specimen3 Mass of Specimen in Air A SSD mass of Specimen B Mass of Specimen in Water C Specimen Bulk Specific Gravity Average G mb = Page 26 Appendix F VDOT and Platinum Performance Partners, LLC

397 Study Question and Answers Specimen Bulk Specific Gravity = ( ) G mb Specimen = ( ) = G mb Specimen 2 G mb Specimen = ( ) = ( ) = = Avg. G mb G mb Specimen 1 + G mb Specimen 2 + G mb Specimen 3 3 Avg. G mb = 3 3 = A. Calculate the Effective Specific Gravity of the Aggregate (G se ) = [100% (total sample) - % asphalt content] = Ps = G se = P s 100 G mm - P b G b G 94.5 se = = = = B. Calculate the Bulk Specific Gravity of the Aggregate (Gsb) = 2.75 Gsb = Gse CF => = Calculate the VTM, VMA, VFA, and F/A ratio for this mix. VTM VTM = 100 X 1. VTM = 100 X 1. VTM = 100 x ( ) VTM = 100 x = 4.4. VDOT and Platinum Performance Partners, LLC Appendix F page 27

398 Study Question and Answers VMA VMA = VMA = VMA = VMA = = 15.8 VFA VFA = 100 X VMA-VTM VMA VFA = 100 X VFA = 100 X VFA = 100 X = 72 F/A Ratio First must calculate the Effective Asphalt Content (P be ) P be = Pb - (P s G b ) G se- G sb G se G sb F/A Ratio = % passing 200 sieve P be P be = ( ) F/A Ratio = P be = (97.80).. F/A Ratio = 0.9 P be = (97.80) (0.002) P be = P be = 4.85 Page 28 Appendix F VDOT and Platinum Performance Partners, LLC

399 Study Question and Answers 4. Do all the volumetric properties meet the mix design criteria for this mix during production? Design Range Criteria Specification Criteria Calculated Results: Design Range Criteria Specification Criteria Calculated Results Meet Spec.? VTM Yes VMA Min Yes VFA Yes F/A Yes Problem No. 2 Answers: Volumetric Calculations The results of laboratory testing of a SM-12.5D yielded the following results: Asphalt Content = 5.01 Correction Factor =.018 Asphalt Binder Specific Gravity = Percent minus 200 = Complete the following tables: Maximum Specific Gravity of Mix (G mm ): = ( ) ( ) Variables Grams Mass Container in Air A Mass Container in Water B Mass Container and Sample in Air C Mass Container and Sample in Water D 1875 Maximum Specific Gravity (G mm ) = = ( ) ( ) VDOT and Platinum Performance Partners, LLC Appendix F page 29

400 Study Question and Answers Bulk Specific Gravity of Mix (G mb ): Variables Specimen 1 Specimen 2 Specimen3 Mass of Specimen in Air A SSD Mass of Specimen B Mass of Specimen in Water C Specimen Bulk Specific Gravity Average G mb = Specimen Bulk Specific Gravity = ( ) G mb Specimen = ( ) = G mb Specimen 2 G mb Specimen = ( ) = ( ) = = Avg. G mb G mb Specimen 1 + G mb Specimen 2 + G mb Specimen 3 3 Avg. G mb = 3 3 = A. Calculate the Effective Specific Gravity of the Aggregate (G se ) = [100% (total sample) - % asphalt content] = Ps = G se = P s 100 G mm - P b G b G se = = = = Page 30 Appendix F VDOT and Platinum Performance Partners, LLC

401 Study Question and Answers 2B. Calculate the Bulk Specific Gravity of the Aggregate (G sb ) = G sb = G se CF = Calculate the VTM, VMA, VFA, and F/A ratio for this mix. VTM VTM = 100 X 1. VTM = 100 X VTM = 100 x ( ) VTM = 100 x = VMA VMA = VMA = ( x 94.99) VMA = VMA = = 13.5 VFA VFA = 100 X VMA-VTM VMA VFA = X. VFA = 100 X VFA = 100 X = 84 VDOT and Platinum Performance Partners, LLC Appendix F page 31

402 Study Question and Answers F/A Ratio - First must calculate the effective Asphalt Content (P be ) P be = P b - (P s G b ) G se- G sb G se G sb F/A Ratio = % passing 200 sieve P be P be = ( ) F/A Ratio = P be = (97.84).. F/A Ratio = 1.3 P be = (97.84) (0.002) P be = P be = Do all the volumetric properties meet the mix design criteria for this mix during production? Design Range Specification Calculated Meet Spec.? Criteria Criteria Results VTM Yes VMA Min No VFA No F/A No Page 32 Appendix F VDOT and Platinum Performance Partners, LLC

403 Study Question and Answers Problem No. 3 Answers: Volumetric Calculations The results of laboratory testing of an IM-19.0A yielded the following results: Asphalt Content = 5.40 Correction Factor =.023 Asphalt Binder Specific Gravity = Percent minus 200 = Complete the following tables: Maximum Specific Gravity of Mix (G mm ): G mm = C-A C-A - D-B Variables Grams Mass Container in Air A Mass Container in Water B Mass Container and Sample in Air C Mass Container and Sample in Water D Maximum Specific Gravity (G mm ) = = ( ) ( ) Bulk Specific Gravity of Mix (G mb ): Variables Specimen 1 Specimen 2 Specimen3 Mass of Specimen in Air A SSD Mass of Specimen B Mass of Specimen in Water C Specimen Bulk Specific Gravity Average G mb = VDOT and Platinum Performance Partners, LLC Appendix F page 33

404 Study Question and Answers Specimen Bulk Specific Gravity G mb = A B - C G mb Specimen = ( ) = G mb Specimen 2 G mb Specimen = ( ) = ( ) = = Avg. G mb G mb Specimen 1 + G mb Specimen 2 + G mb Specimen 3 3 Avg. G mb = 3 3 = A. Calculate the Effective Specific Gravity of the Aggregate (G se ) = [100% (total sample) - % asphalt content] = Ps = G se = P s 100 G mm - P b G b G se = = = = B. Calculate the Bulk Specific Gravity of the Aggregate (G sb ) = Gsb = Gse CF = Page 34 Appendix F VDOT and Platinum Performance Partners, LLC

405 Study Question and Answers 3. Calculate the VTM, VMA, VFA, and F/A ratio for this mix. VTM VTM = 100 X 1. VTM = 100 X VTM = 100 x ( ) VTM = 100 x = VMA VMA = VMA = ( x 94.60) VMA = VMA = = 15.3 VFA VFA = 100 X VMA-VTM VMA VFA = 100 X 15.3 VFA = 100 X VFA = 100 X = 78 VDOT and Platinum Performance Partners, LLC Appendix F page 35

406 Study Question and Answers F/A Ratio - First must calculate the effective Asphalt Content (P be ) P be = Pb - (P s G b ) G se- G sb G se G sb F/A Ratio = % passing 200 sieve P be P be = ( ) F/A Ratio = P be = (97.44).. F/A Ratio = 1.2 P be = (97.44) (0.003) P be = P be = Do all the volumetric properties meet the mix design criteria for this mix during production? Design Range Criteria: Specification Criteria, Calculated Results: Design Range Criteria VTM VMA VFA F/A Specification Criteria Calculated Results Meet Spec.? Yes Min Yes Yes Yes Page 36 Appendix F VDOT and Platinum Performance Partners, LLC

407 Study Question and Answers Chapter Ten: Quality Acceptance and Data Processing 1. A mathematical analysis of accumulated data is called: B. Statistics 2. The job mix formula with the tolerance applied is the: B. Acceptance range 3. The quantity of material to be checked for compliance with specifications is called: B. A lot 4. The job mix formula is chosen from the: B. Design range 5. A reduction in the unit bid price of material is known as: C. A price adjustment 6. When the normal daily production of the source from which asphalt concrete is being obtained is in excess of 4000 tons, the lot size may be increased to: C tons 7. Standard deviation computations are not normally made on more than two job mixes for the same type material on a single project. A. True 8. The amount of deviation allowed from the job mix formula is known as the: B. Process tolerance 9. How many adjustment points may a material have and still remain in the road? C. 25 or less 10. Variability can be computed on any number of samples except: A. One 11. Would the process tolerance be the same for three tests as a lot with four tests? B. No 12. After running analysis on a sample, how is it checked for conformity with specifications? 13. On a failing lot, who is responsible for applying the adjustment points? The average of four results is compared to the job mix, individual test results are not District Materials Engineer VDOT and Platinum Performance Partners, LLC Appendix F page 37

408 Study Question and Answers 14. If a job mix is in the design range, can it be disapproved? Yes, if the mix will not meet specification requirements such as density 15. Where are the standard deviation limits found for asphalt concrete? Section Table II What number of adjustment points constitutes the removal of the material from the road? More than 25 (Section ) 17. Why is it important that a Producer know what the product variability is at all times? 18. Calculations for the gradation of aggregate in the mixture are shown to what percent? The asphalt content to what percent? In order to know whether his process is in control Aggregate to the nearest tenth. Asphalt to the nearest hundredth. 19. What, if any adjustment points would be applied to a mix if the standard deviation for the No.200 material is 2.3? Two (2) adjustment points Page 38 Appendix F VDOT and Platinum Performance Partners, LLC

409 Problem No.1 Answers Study Question and Answers TL-100A VIRGINIA DEPARTMENT OF TRANSPORTATION REV: 03/2010 MATERIALS DIVISION ASPHALT CONCRETE - TEST RESULTS INPUT FORM VDOT and Platinum Performance Partners, LLC Appendix F page 39