PROJECT OFFICE MANUAL

Transcription

1 REPLACES D PENNSYLVANIA DEPARTMENT OF TRANSPORTATION PROJECT OFFICE MANUAL PART 22-1 May 15, 2015 SUJECT MINIMUM QUALITY CONTROL REQUIREMENTS FOR INCOMING RAP STOCKPILES AND PROCESSED RAP STOCKPILES AT ITUMINOUS CONCRETE PLANTS These RAP stockpile requirements are a supplement to the Project Office Manual (POM), Part, Section, Page 5-1, Minimum Quality Control Plan for ituminous Concrete when a bituminous producer proposes to produce bituminous mixtures containing RAP with RR > for wearing/binder courses, or RAP with RR > 0.25 for base courses. RR (Reclaimed Asphalt inder Ratio), for use of thisthese minimum QC requirements, is defined as the ratio of reclaimed asphalt binder from RAP in the mixture to the total asphalt binder content of the mix greater than 15% RAP and less than or equal to 35% RAP. These minimum stockpile requirements are intended for both incoming RAP material (raw RAP) and processed RAP material where the processed RAP material is processed and stockpiled prior to being incorporated into the plant production process. These minimum quality control guidelines do notinclude address incoming RAP material that is processed in-line as part of the plant production process and directly incorporated into the plant production process. Each bituminous concrete producer intending to produce bituminous mixtures containing RAP with RR>0.20 for wearing/binder courses, or RAP with RR > 0.25 for base courses or Tier 3greater than 15% RAP and less than or equal to 35% RAP, must include these supplemental minimum requirements in their Quality Control Plan under Section.13., RAP Material or Section C.1., Aggregate/RAP/RAM/RAS Stockpiles of the POM, Part, Section, Page 5-1. The following Quality Control Plan is the minimum plan designed to meet these standards: A. Stockpile StockpilingPreparation of Incoming RAP Material (Raw RAP) 1. Incoming raw RAP material is not required to be stockpiled on a prepared pad as required under Pub. 408, Section (b) unless the producer plans to immediately use the incoming raw RAP material in production (i.e., incoming freshly milled RAP material). If the producer plans to immediately use the incoming raw RAP material, the RAP shall be stored according to either Section.2. or C.2. and C.3. hereinprepare stockpile area by constructing a level pad. Construct the pad according to the aggregate storage requirements in Section (b) for use in bituminous concrete. 2. Producer The producer is responsible to monitor the unprocessed RAP stockpile to prevent the incorporation of non-rap material (uncoated aggregate, subbase material, subgrade material, etc.), contaminated or deleterious material into the stock pile. Non-RAP material, contaminants and deleterious material This type of material must be immediately removed from

2 22-2 the stockpile. Other examples of contamination include milled-up paving geosynthetics, reflective lane markers, road debris, and construction trash. 3. Do not incorporate bituminous plant waste material consisting of uncoated or partially coated aggregate material discarded from the plant during mixture transition or plant start-up. 4. When incoming RAP material is to be used in wearing courses, the Producer is responsible for monitoring, documenting (SRL and quantity), and segregating (separate stockpiles) the incoming RAP material for SRL from both PennDOT projects and other projects (commercial, municipal, etc.). 5. When possible, For a specific designated unprocessed RAP stockpile to be utilized in a wearing course, Penn DOT will provide the producer with the SRL of the wearing course(s) to be milled from PennDOT projects based on pavement history documentation or other District information. (This information will be provided in the contract document). This information is typically provided in the pavement history part of the contract documents). The producer will be responsible for maintaining the integrity of the SRL for that designated stockpile.. Processing, and Sampling, and Stockpiling of RAP Stockpile Material Prior to Incorporating into Asphalt Concrete Mixtures by the Direct Feed RAP System (Processed RAP) 1. The Direct Feed RAP System is defined as an asphalt concrete plant system where crushed, screened, and/or processed RAP material is introduced into the asphalt concrete mixture directly through a feed hopper which then directly feeds onto aone or more scalping or sizing screen(s) before the RAP material is incorporated into the production of the asphalt concrete mixture. 100% or near 100% (less scalping) of RAP material fed into a Direct Feed RAP system gets incorporated into the asphalt concrete mixture 2. Prior to crushing, screening or processing incoming raw RAP material, prepare a crushed, screened and/or processed RAP material stockpile area Prepare a stockpile area by constructing a level pad. Construct the pad according to the aggregate storage requirements in Section (b) for use in bituminous concrete. As an alternative, construct a pad of incoming raw RAP material compacted to a 150 mm (6 inch) depth The maximum size of aggregate or particles of processed RAP material as weighed and entered directly into the asphalt concrete mixture after screening or scalping (during asphalt mixture production) in the processed RAP shall be no greater than the maximum aggregate in the JMF. 3.4.During crushing, screening, and/or processing of the incoming RAP material, a representative sample shall be taken every 500 1,000 tons to determine the

3 22-3 asphalt content and, aggregate gradation, and a representative sample shall be taken every 3000 tons to determine maximum theoretical specific gravity (Gmm), RAP aggregate effective specific gravity (Gse), and RAP aggregate bulk specific gravity (Gsb). The RAP asphalt content must be determined using PTM No. 02 if the processed RAP stockpile will be used to produce mix designs with reclaimed asphalt binder ratio (RR) equal to or exceeding As an example, if an asphalt mix is designed wth RR = 0.28, then asphalt content of the processed RAP material, for the purpose of quality control, must be determined using PTM No. 02. Sampling must be done in a way to avoid segregation and/or contamination, and to provide an unbiased representative sample of the main RAP stockpile. Miniature sampling stockpiles shall be created and flattened using the equipment blade and a back-dragging technique. Each sample shall be obtained by taking at least three portions from the flattened surface with a square-ended shovel. Process is repeated at different locations around the main stockpile. Note 1: If the producer desires to use PTM No. 5 to determine asphalt content and gradation of the crushed, screened and/or processed RAP, a minimum of five (5) companion samples must initially be collected and tested according to PTM No. 5 at the beginning of each RAP crushing, screening and/or processing operation or annually, whichever is more frequent. Compare the asphalt content and gradation results determined by PTM No. 5 and PTM No. 02 and PTM No. 39 and determine average correlation factors for both asphalt content and percent passing the 5 µm (No. 200) sieve. After determining the average correlation factors for asphalt content and percent passing the 5 µm (No. 200) sieve, PTM No. 5 may be used to test the remaining samples from the RAP crushing, screening, and/or processing operation. Apply the average correlation factors for asphalt content and percent passing the 5 µm (No. 200) sieve to the PTM No. 5 test results to determine the final asphalt content and gradation of the crushed, screened, and/or processed RAP 4.5.After obtaining and testing ten (10) samples, calculate the average and standard deviation for each individual sieve, and asphalt content, and effective specific gravity (Gse) for these ten (10) samples. These calculated values will serve as a baseline for the aggregate gradation and asphalt content. Each additional RAP sample will be evaluated against the baseline criteria. The maximum standard deviation for asphalt content and gradation of the baseline stockpile shall not exceed the values specified in Section 409, Table -1. If these values are not met, the RAP stockpile has high variability and needs to be investigated before usecannot be used without further processing and resampling to determine a new baseline and comparison of the new baseline to the standard deviation requirements specified in Section 409, Table -1. If the stockpile meets specification requirements, additional RAP is allowed to be added to the stockpile. If tthe asphalt content and gradation

4 22-4 of the material to be added will be included with the previous data on asphalt content and gradation (baseline data and any previously added material) to calculate a new standard deviation. Any newly computed standard deviation shall not exceedvaries more than +/- 1.0% from the baseline value, the standard deviations of Table -1 in Section 409. Otherwise, this material will not be added to the stockpile and further production should be halted or placed on a separate stockpile until material can be produced within this guideline. If the gradation of a sample results in a significant variation from the baseline aggregate gradation; production should be halted or placed on a separate pile until the production process has been corrected. Significant variation in gradation is defined as a sample gradation that would result in the completed ituminous or Asphalt Mixture varying outside the Section 409, Table A, multiple sample (n 3) gradation tolerances if the processed RAP was incorporated into the completed mixture at 35%. Maintain an overall average and standard deviation of all samples for each standard sieve size and, asphalt content, and the effective specific gravity (Gse) of the processed RAP stockpile. 6. The three samples taken for specific gravity will be processed to determine Gmm, Gse, and Gsb. RAP aggregate bulk specific gravity (Gsb) shall be determined according to one of the procedures established in Appendix H, ulletin 2. Calculate the average and standard deviation of Gsb for these three (3) samples. These calculated values will serve as a baseline for the RAP aggregate bulk specific gravity. The maximum standard deviation for Gsb shall not exceed the value specified in Section 409.2(e).2c. If this value is not met, the RAP stockpile cannot be used without further processing and resampling to determine a new baseline and comparison of the new baseline to the standard deviation requirements specified in Section 409.2(e). If the stockpile meets specification requirements, additional RAP is allowed to be added to the stockpile. The Gsb of the material to be added will be included with previous data on Gsb (baseline data and any previously added material) to calculate a new standard deviation. Any newly computed standard deviation shall not exceed the standard deviations of Section 409.2(e).2c. Otherwise, this material will not be added to the stockpile and further production should be halted or placed on a separate stockpile until material can be produced within this guideline. Maintain an overall average and standard deviation of all samples for Gsb of the processed RAP stockpile.

5 Identify the RAP stockpile if being utilized in a wearing course for a Designated Project and identify the RAP stockpile if intended and meeting the requirements for a Tier 3 asphalt mixture design (high RAP). 8. All RAP stockpiles designated for a specific project must be approved by the District before the material is utilized in the production of an approved JMF. This is to insure ensure that the designated stockpile complies with the projects aggregate and SRL requirements. Note 2: Fractionating RAP into multiple size ranges is recommended when RAP content falls in Tier 3 (high RAP). Since the outcome of fractionating is different RAP sizes, it provides flexibility in meeting mix design requirements. Fractionating provides better control of gradation and less variability but, in general, increases the cost as additional bins will be needed to simultaneously feed multiple fractions. Note 3: There is conflicting evidence whether RAP from multiple sources can be combined or RAP stockpiles from different sources should be kept separated. NCHRP Report 52 reports that processed RAP from multiple sources is typically more consistent than virgin aggregate and therefore, the requirements to limit RAP to single-source materials are not justified. Others advocate that keeping single source RAP eliminates the need for crushing or fractionating and therefore saving time and money. RAP from multiple sources can be combined as long as proper steps are taken to ensure consistency and uniformity of the stockpile as discussed in this document. However, when large quantities of RAP become available from one source, it is always good practice to generate a RAP stockpile allocated to this source only and separate from other RAP stockpiles. Note 4: In most RAP crushing practices, a single maximum size, such as 1 inch, 1/2 inch, or 3/8 inch, is considered. Crushing large aggregate particles in the RAP generates fines. In many cases, the amount of fines generated in RAP limits the percentage of RAP that can be used in the mix. Therefore, over-crushing should be avoided to limit the amount of fines generated in the RAP. The least desirable option is to crush the millings to the point that they all can pass the desired screen size. In this option, more uncoated faces of RAP particles and excessive dust are generated. It is considered a best practice to minimize crushing of the millings, and use screening to remove large particles from the millings. Prescreening is a best practice if the millings are to be processed in a crusher. With prescreening, the fines are filtered out first before crushing. Note 5: While not required, it is good practice to store processed RAP material under a roof while allowing circulation of air from open ends, to protect it from precipitation. This will help to minimize moisture in the RAP. It is not good practice to cover the RAP with tarp or plastic. It is also

6 22-6 recommended to store the processed RAP material at a maximum stockpile height of 20 feet. C. Processing, Sampling and Directly Incorporating RAP Material into Asphalt Concrete Mixtures Utilizing an In-Line RAP System. 1. An In-Line RAP System is defined as an asphalt concrete plant system where the RAP material introduced into the asphalt concrete mixture is material that passes through one or more sizing screens. The larger particles that do not pass through the sizing screen(s) are conveyed to an in-line breaker or crusher system and recirculated in a closed loop process back across the sizing screen(s). 2. The incoming raw RAP material intended for use in the In-Line RAP System must be either milled or crushed prior to introduction into the In-Line RAP System to avoid very large material agglomerations. This milled or crushed RAP material must then be stockpiled and tested according to section C.8. herein. 3. Prior to milling or crushing the incoming raw RAP material, prepare a milled or crushed RAP material stockpile area by constructing a pad according to the aggregate storage requirements in Section (b). As an alternative, construct a pad of incoming raw RAP material compacted to a 150 mm (6 inch) depth. 4. All milled or crushed RAP material stockpiles intended to be used in an In- Line RAP System for a specific project or specific mix design(s), which requires a specific SRL and aggregate requirement, must be approved by the District Materials Engineer/Manager before the material is utilized in the production of an approved JMF. This is to ensure that the designated stockpile complies with the project aggregate and SRL requirements. 5. The maximum size of aggregate or particles of RAP material as weighed and entered directly into the asphalt concrete mixture after the In-Line RAP System (fully processed RAP) shall be no greater than the maximum aggregate size in the JMF. 6. Calibrate the In-Line RAP System to meet the applicable Plant Tolerances in ulletin 2, Chapter 1 for either batch plants or drum mix plants. During calibration of the In-Line RAP System, calibrate using the incoming raw RAP material or the milled or crushed RAP material that will be used during asphalt concrete mixture production. If calibrating only the RAP scale, standard aggregate material may be used as an alternate to RAP material.. For batch plants, the fully processed RAP material must be sampled prior to entering the weigh box or hopper. For drum mix plants, the fully processed RAP material must be sampled just prior to entering the drum by either taking a sample from the fully processed RAP material conveyor belt or taking a sample of the fully processed RAP material that has been diverted from

7 22- entering the plant using a diverter chute. Sample the fully processed RAP material at the designated locations according to AASHTO T Ideally in-line crushing circuits will be designed to only break up agglomerations. During the milling or crushing process of the incoming raw RAP material, a representative sample of the milled or crushed RAP material shall be taken every 1000 tons to determine the asphalt content and aggregate gradation regardless of material coming from one source or from more than one material course or location. The average and standard deviation for asphalt content and gradation of 10 samples will be determined. The maximum standard deviation for asphalt content and gradation of the baseline stockpile shall not exceed the values specified in Section 409, Table 1. An average baseline asphalt content will be established based on these 10 samples. If the asphalt content and gradation of the material to be added, vary from the baseline average value, more than twice the standard deviations of Table 1 in Section 409, this material will not be added to the stockpile. The RAP asphalt content and gradation of the stockpiled RAP can be determined using PTM No. 02 or PTM No. 5. The contractor may choose higher frequency of sampling/testing the stockpiled RAP if this further sampling/testing is deemed necessary by the contractor for better control of the in-line processed RAP. 9. The asphalt content and gradation of the fully processed RAP (i.e. the material that has been processed through the In-Line system) will be used to establish mix design inputs for the RAP material. During asphalt concrete mixture production using the In-Line RAP System, a representative sample of the In-Line RAP System (fully processed RAP) material shall be taken every 1,000 tons to determine the asphalt content and aggregate gradation. The RAP asphalt content during production must be determined using PTM No. 02 for Tier 3 (high RAP) mix designs, unless correlation factors between the results from PTM 02 and PTM 5 are first established for the fully processed RAP (See Note 1). The asphalt content and gradation of the fully processed RAP must follow requirements stated under subsections.4 and.5 for the Direct Feed System processed stockpile. 6. Note : For the In-Line Processing system, if the asphalt content and gradation of the fully processed RAP is proven to be similar to the stockpiled RAP, and within specification limits, then the asphalt content and gradation of the stockpiled RAP maybe used for mix design and quality control, and one daily sample of the fully processed RAP is sufficient for comparison.