The University of Nottingham. Department of Civil Engineering

Transcription

1 The University of Nottingham Department of Civil Engineering USING RECYCLED AGGREGATE IN HOT ASPHALT MIXTURES IN GAZA STRIP By Rami M Alfaqawi Department of Civil Engineering, University of Nottingham, UK Supervisor: Dr. Tony Parry Project Submitted to the University of Nottingham in partial fulfilment of the degree of Master of Science in Infrastructure September 2012 i

2 DECLARATION This is to confirm that this is my own work and does not break the University, school or module conventions on plagiarism as outlined on p30 of the School of Civil Engineering MSc in Civil Engineering/Infrastructure/Civil Engineering Mechanics course handbook Date: 30/08/ i

3 ABSTRACT Recycled Aggregate used for pavement construction can be a solution for the shortages of natural aggregate and lack of the dumping landfills. The potential use of recycled coarse aggregates (RCA) resulted from crushing cement hollow blocks in Hot mix asphalt (HMA) is investigated in this study. Mixtures with 30% and 60% of RCA are evaluated for their mechanical properties and for their performance. The results show that the mixtures with 30% RCA satisfy all the specification requirements in Gaza Strip and it exhibits better performance compared to a control mix made from limestone natural aggregates (NA). this mixture with 30% RCA has 25% higher stiffness modulus compared to control mix and more than 100% better fatigue life at optimum bitumen content. However, its optimum bitumen content is 0.35% higher than for the natural aggregate mixture. The mixture with 60% recycled aggregate shows lower performance characteristics compared to the NA for both tests. All results indicate that using this RCA is feasible, and it can improve properties of asphalt mixture and its performance, however increasing the RCA in the mixture to 60% may results in reduction of these performance properties. ii

4 ACKNOWLEDGEMENT I would like to express my deep gratitude to my supervisor Dr. Tony Parry for the great help and close supervision he provided for me in carrying out this work. Sincere thanks are also extended to the School of Civil Engineering laboratory technical staff; Richard Blakemore, Michael Winfield, Martyn Barret and Nancy Milne for their genuine assistance in the laboratory works. Many thanks are given to Dr. James Grenfell who has spent plenty of time to discuss with me the experimental program and for his support that helped me to successfully finish this research. Thanks are also due to my colleagues for their constructive suggestions and supports. Sincere thanks, to my Parents, Brothers and Sisters for their continuous support, encouragement and patience, who have always believed in me and constantly support alongside. Finally, I would like to express many thanks to Hani Qaddumi Scholarship Foundation (HQSF) for their generous sponsorship of my Master program which without their help this work cannot be implemented. iii

5 Table of Contents ABSTRAC... ii ACKNOWLEDGEMENT... iii LIST OF TABLES... vii LIST OF FIGURES... viii Notations... x 1. INTRODUCTION Background Problem Statement Aims and Objectives of Research Aim of Research Objectives of Research Research Methodology Literature Review Aggregate Samples Preparations Aggregate Tests Preparing HMA Samples for Test Experimental Tests on HMA Samples Evaluating the Results and Recommendations Layout of Dissertation LITERATURE REVIEW General Background Recycling Aggregates in Different Countries Recycling in Gaza Strip: UNDP Project Government Project: Physical and Mechanical Properties of RCA in Gaza Strip: Sieve Analysis: Impact Value Test Other Tested Properties Economical Assessments of Recycled Aggregate: Problems Encountered in Recycling Potential Uses of Recycled Aggregates: Using RCA in HMA iv

6 2.7 Conclusion: ROAD PAVEMENT AND SPECIFICATIONS Road Pavement Mix Design Binder Course Specification International Specifications (ASTM D3515-D-4) Egyptian Specification Specifications Required By UNDP Projects in Gaza Strip Conclusion EXPERIMENTAL PROGRAM General Materials Bitumen Fine Aggregates Natural Coarse Aggregates Recycled Aggregates Aggregate Tests Sieve analysis Particle Density and Water Absorption Sample Preparation Marshall Method Finding Optimum Bitumen Content Density Voids Analysis Performance Tests Indirect Tensile Stiffness Modulus (ITSM) Fatigue Test (ITFT) RESULTS AND DISCUSSION Tests Results Determination of Particle density and water absorption Gradation test Maximum density of the mixture The results of density voids analysis Indirect Tensile Stiffness Modulus Indirect Tensile Fatigue Test Results v

7 5.2 Results Discussion Particle density and water absorption The gradation test The maximum density Marshall Properties and Optimum Bitumen Content Indirect Tensile Stiffens Modulus Indirect Tensile Fatigue Test CONCLUSION AND RECOMMENDATIONS Conclusion Limitation of This Study Recommendations and Further Work References vi

8 LIST OF TABLES Table Table2.1: Sieve analysis for different types of natural and recycled aggregate.. Table2.2: Main properties of recycled coarse aggregates in Gaza strip after Ghuraiz et al. (2006). Table 2.3: Recycled fine aggregate properties compared with natural sand after Ghuraiz et al. (2006).. Page Table 2.4: Mechanical test results by Pérez et al (2011) 16 Table 2.5: Summary of RCA test result 23 Table 3.1: The desired properties of Asphalt mixtures 26 Table 3.2: Gradation of Asphalt Binder course ASTM D (2001). 27 Table 3.3 Gradation of Asphalt Binder course in Egyptian specification 28 Table 3.4: The Mechanical Properties of the Egyptian Asphalt Binder Course. 29 Table 3.5: Gradation of Asphalt Binder course required for UNDP projects 30 Table 3.6: The Mechanical Properties of the Egyptian Asphalt Binder Course. 30 Table 4.1: Marshall property limits to satisfy all specifications 39 Table 5.1: Particle density test results for NA. 48 Table 5.2: Particle density test results for RCA. 48 Table 5.3: NA gradation test results for different aggregate sizes 49 Table 5.4: RCA gradation test for different aggregate sizes 49 Table 5.5: NA gradation curve used in mixture design 50 Table 5.6: RCA-30 gradation curve used in mixture design 52 Table 5.7: RCA-60 gradation curve used in mixture design 54 Table 5.8: The maximum density of the mixtures.. 56 Table 5.9: the stiffness modulus and the standard deviation for mixtures 75 vii

9 LIST OF FIGURES Figure Page Figure 2.1: Destroyed buildings and some debris - Gaza Figure 2.2: UNDP Crusher-Khanyounis-south of Gaza.. 7 Figure 2.3: Crusher removing destroyed building debris. 8 Figure 2.4: UNDP sample gradation curve.. 9 Figure 2.5: Governmental sample gradation curve 10 Figure 2.6: Dynamic Modulus of selected VA-RCA by Mills-Beale & You (2010).. 17 Figure 2.7: The resilient modulus test setup. 18 Figure 2.8: The indirect tensile strength results obtained by Chen et al. (2011) 21 Figure 2.9: IDT results for water sensitivity tests obtained by Chen et al. (2011). 21 Figure 2.10: Fatigue life test results after Chen et al. (2011).. 22 Figure 3.1: Typical cross section of the flexible pavement 24 Figure 3.2: Gradation of Asphalt Binder course ASTM D (2001). 28 Figure 3.3: Gradation of Asphalt Binder course Egyptian specification 29 Figure 3.4: Gradation of Asphalt Binder course required for UNDP projects.. 30 Figure 3.5: Gradation of different specifications in Gaza Strip.. 31 Figure 4.1: Fine limestone aggregates.. 33 Figure 4.2: Different sizes of the limestone coarse aggregates 33 Figure 4.3: Different sizes of the Recycled Coarse Aggregates 34 Figure 4.4: Marshall Samples for different mixtures. 37 Figure 4.5: Selection of Optimum Bitumen Content (by Roberts et al. (1996)) 38 Figure 4.6: ITSM test of samples using Nat machine 44 Figure 4.7: ITFT test for one of the samples using Nat machine.. 45 Figure 4.8: NA samples tested for ITFT at 20 o C 46 Figure 5.1: Comparing NA gradation with ASTM limits. 50 Figure 5.2: Comparing NA gradation with Egyptian limits. 51 Figure 5.3: Comparing NA gradation with UNDP limits. 51 Figure 5.4: Comparing RCA-30% gradation with ASTM limits. 53 Figure 5.5: Comparing RCA-30% gradation with Egyptian limits. 53 Figure 5.6: Comparing RCA-30% gradation with UNDP limits. 54 Figure 5.7: Comparing RCA-60% gradation with ASTM limits. 55 Figure 5.8: Comparing RCA-60% gradation with Egyptian limits. 55 Figure 5.9: Comparing RCA-60% gradation with UNDP limits. 56 viii

10 Figure 5.10: Comparing Marshal property curves for different mixtures.. 58 Figure 5.11: Marshal property curves for NA mixture 59 Figure 5.12: Marshal property curves for RCA-30% mixture 60 Figure 5.13: Marshal property curves for RCA-60% mixture.. 61 Figure 5.14: Determining the optimum bitumen content for NA mixture. 62 Figure 5.15: Determining the optimum bitumen content for RCA 30% Figure 5.16: Determining the optimum bitumen content for RCA-60% 63 Figure 5.17: Average stiffness modulus for NA. 63 Figure 5.18: Verage stiffness modulus t for RCA-30%. 64 Figure 5.19: Average stiffness modulus content for RCA-60%.. 64 Figure 5.20: Average stiffness modulus for different mixtures.. 65 Figure 5.21: Variation of number of fatigue cycle to failure with bitumen content for NA 65 Figure 5.22: Variation of number of fatigue cycle to failure with bitumen content for RCA-30%. 66 Figure 5.23: Variation of number of fatigue cycle to failure with bitumen content for RCA-60% 66 Figure 5.24: Comparing fatigue characteristics for different mixtures 67 Figure 5.25: Mean stiffness modulus at different bitumen content at 10⁰C. 67 Figure 5.26: Calculated horizontal strain for NA at different bitumen content. 68 Figure 5.27: Calculated horizontal strain for RCA-30% at different bitumen content 68 Figure 5.28: Calculated horizontal strain for RCA-60% at different bitumen content 69 Figure 5.31: The breaking plan of the NA samples tested for ITFT. 76 Figure 5.31: The breaking plan of the NA samples tested for ITFT. 77 Figure 5.31: The breaking plan of the NA samples tested for ITFT. 77 ix

11 Notations HMA NA RA RCA RFAP RCA-30% RCA-60% Nat NTEC VMA V.F.B. ITSM ITFT ITST UNDP Hot Mix Asphalt Natural Aggregates Recycle Aggregates Recycled Coarse Aggregates Recycled Fine Aggregate Powder Mixture made with NA and 30% of RCA Mixture made with NA and 60% of RCA Nottingham Asphalt Tester machine Nottingham Transportation Engineering Centre Voids in Mineral Aggregates Voids Filled with Bitumen Indirect Tensile Stiffness Modulus Indirect Tensile Fatigue Test Indirect tensile Stiffness test United Nation Development Program x

12 Chapter 1 Introduction 1. INTRODUCTION 1.1 Background Recycling of different materials is a matter of global concern it is of the greatest international interests. The urgent need for recycling aggregates has been raised in recent years as a result for the shortage of natural materials, and the increasing cost of landfill in most countries. Moreover, environmental considerations play a major role, where recycling saves virgin material and energy, also it reduces greenhouse gas emissions and delivers better sustainable future (Aatheesan, 2011). Reusing the materials of demolished buildings is not a new concept, as many countries have been crushing the rubbles to aggregate for a number of years. In Gaza Strip (which is a small closed coastal area of Palestine with a total area of 365 Km 2), recycling and reusing of demolishing rubbles has gained more interest especially after 2006 when Israel disengagement from Gaza ex-settlements, huge amount of debris has been generated. Moreover as a result of Israeli attack on Gaza Strip in December 2008 and besides the hundreds tons of rubble generated annually due to reconstruction, it becomes very important to study all the possibilities of using this rubble in construction. However, limited research have been conducted to investigate the potential use of recycled aggregates in Gaza, the main fields covered were: concrete mixes, hollow blocks and using it as sub base in roads (Rustom et al. 2007). In recent years using recycled aggregate in hot mix asphalt (HMA) has been an important topic for research studies in many countries, the performance of HMA with recycled coarse aggregates (RCA) is mainly related to the heavy crushed face, which contributes to the internal friction for permanent deformation resistance. From this point of view, HMA made with RCA performs better in terms of permanent deformation and stiffness than HMA with only natural aggregates (NA) (Pérez et al. 2012). 1

13 Chapter 1 Introduction 1.2 Problem Statement The disposal of construction and demolished buildings in Gaza Strip is one of the challenging problems, due to the lack of open lands and limited size of municipal dumping sites to accommodate the large quantities of rubbles generated in the last years. So that make it necessary for researchers to think seriously in finding ways and possibilities to reuse these rubbles as an alternative substitution for the natural aggregates in infrastructure projects, like the asphalt pavements. Also this will solve the problem of the lack of NA in Gaza Strip, where it is not available in Gaza Strip and it is used to be imported from abroad, but during the latest years it becomes very difficult to get it due to the Israeli siege on Gaza. 1.3 Aims and Objectives of Research Aim of Research In line with the above-defined problems, the principal aim of this research is to investigate the effects of using demolishing debris, (which mainly consist of crushed hollow blocks and concrete) as alternative for natural aggregates in HMA. This study will mainly consider the low traffic highways in Gaza Strip, since it is believed that the RCA will behaves better in low traffic roads Objectives of Research In order to achieve the aim of this research the following main objectives should be assessed: Study and understand the main properties of the demolishing debris in Gaza Strip Economical assessment of using Recycled Aggregate Evaluate the main mechanical properties of recycled aggregates such as Unit weight, specific gravity and water absorption. Investigate the main volumetric properties of the asphalt mixture and study the performance of the mixture in terms of the required properties and specifications for low traffic volume roads and compare it with the local standards in Gaza, this includes air voids, binder content, stiffness and fatigue. 2

14 Chapter 1 Introduction 1.4 Research Methodology The research method is based on laboratory investigations. In order to achieve the research objectives, the following methodology has been followed: Literature Review An extensive survey about using demolishing construction rubbles as recycle aggregates has been performed to improve a strong background in this area and in order to investigate the potential use of these rubbles Aggregate Samples Preparations Two types of aggregates have been used in this research one is the natural aggregates which is limestone and the second is recycled hollow block (which has a strength of 3.6 KN) that has been crushed into aggregates of maximum size of 20 mm and sieved to get the required gradation for the dense asphalt mixture Aggregate Tests A series of experimental tests were conducted to both recycle and natural aggregates sample to compare the mechanical and physical properties and to insure that it satisfies the national standards and requirements, these tests include sieve analysis, particle densities and water absorption Preparing HMA Samples for Test HMA samples were prepared using Marshall Method with four different binder contents and with different RCA percentages in the mixture, these samples then trimmed to 40mm thickness to fit the Nottingham asphalt tester Machine (NAT) which required 40 mm thickness for the samples to be tested Experimental Tests on HMA Samples Volumetric properties and performance of the HMA have been investigated by conducting the density tests, stiffness and fatigue tests to evaluate the applicability of using the this type of blocks as RCA in HMA by comparing the results with the samples with NA and to insure that it is within the limits and specifications in Gaza Evaluating the Results and Recommendations After conducting the experiments and analyzing the results the decision about using this recycle aggregate in HMA will be taken and the recommendations for future and further research will be suggested to continue the study and for more confident results. 3

15 Chapter 1 Introduction 1.5 Layout of Dissertation CHAPTER 1 is an introduction, which presents a background to the applicability of using the construction and demolishing debris as RCA in HMA. The aims and objectives of the research are presented in this chapter as well. In CHAPTER 2 of this dissertation, a review of previous work literature is presented, and it mainly concentrates on the following points: - The main sources of demolishing rubbles and the importance of recycling in Gaza Strip. - Economical evaluation of recycling process in Gaza Strip. - Historical uses and potential application of RCA in various structures around the world. -Experimental tests and investigations were performed on RCA to determine the applicability of using RCA in different applications especially in HMA -Recommendations and suggestions that must be taken into considerations when dealing with RCA and during the experiment conducting. Road pavements and specifications of asphalt binder course are covered in CHAPTER 3. In this chapter three different specifications that used in Gaza Strip are presented and compared. In CHAPTER 4 the experimental work and methodology used in the laboratory tests are presented. CHAPTER 5 includes the results and discussion of the findings. a comparison of the results with the specifications are covered in this chapter. Finally, in CHAPTER 6 the conclusion, recommendations, and some suggestions for father works are presented. 4

16 Chapter 2 Literature review 2. LITERATURE REVIEW 2.1 General Background Recycling of demolished building rubble is not a new concept, as several countries have been crushing rubbles to aggregate for a number of years. In recent years, the recycling, and reuse of concrete rubble in Gaza Strip has gained more interest, where after Israeli disengagement from Gaza ex-settlements in 2006, and as a result of last war on Gaza in December 2008, beside hundreds tons of rubble generated annually, a huge amounts of demolition debris were formed. The main focus of the recycling effort has been on the concrete rubble and the production of recycled aggregate since concrete rubble makes up the largest segment in Gaza Strip waste (El Kharouby, 2011). Figure2.1 shows some demolished buildings in Gaza. Figure 2.1: Destroyed buildings and some debris - Gaza However almost of reinforced construction in Gaza accompanied with blocks and tile materials. Thus, the collected Demolishing Debris from the damaged structures contain considerable amount of hollow blocks and tile as well as waste concrete. The properties of the recycled blocks and tiles and their effects on the on pavement or concrete mixes are less well known in the literature. 5

17 Chapter 2 Literature review According to the Governmental statistics it was found that the amount of debris lies in the range of 1,250,000 to 1,500,000 ton and its removal costs 16.5 m$. Also United Nations Development Program (UNDP) in Gaza estimated this debris in the range of 500,000 to 600,000 ton of rubble in good and clean conditions (Aljassar et al. 2005). So these large amounts of debris are considered as a serious problem which affects the environment in different ways. Therefore, many researches and several projects for crushing and recycling this debris started to explore the potential uses for this material, so it found that this would solve two problems: The first one is environmental problem; the second one is that recycling was a solution for lack of construction materials in Gaza Strip. So it was a good alternative (Rustom et al. 2007, El Kharouby, 2011, Ghuraiz et al. 2011). Some private companies started crushing of concrete and recycled it. This process took place in small blocks and paving blocks factories in Gaza Strip and showed successful results. Some studies investigated the suitability of the crushed material generated by crushers in Gaza Strip to be used as recycled aggregate in road pavement as subbase and base course layers. The results shows that, from technical point of view, it is suitable to be used as subbase and base course material and it is good alternative of natural aggregate based on economical assessment standpoint (Jendia & Besaiso 2011). 2.2 Recycling Aggregates in Different Countries The recycling of different materials especially recycling of the construction demolishes and debris showed a rabid increase in many countries. As an example, Zebau (2006) shows that during 2002 and 2003 In Germany around 86% of generated Construction and demolition materials wastes were recycled which represents around 60% of the total waste material of about 380 million ton. In the UK, the demand for aggregates has risen steadily after the Second World War, and this is due to the argent need for houses as well as the new network of roads. Road construction accounts for about third of this annually demand. However the available specifications for the use of recycled aggregates in pavement construction for suitability of using it is judged by existing standards for the virgin aggregates, these standards are imposing a barrier on the use of 6

18 Chapter 2 Literature review recycled aggregates, since they impose characteristics such as required densities that cannot be met by recycled materials. In Europe, surveys showed that 25% of the waste is coming from the demolition of buildings and roads, 90% of it is recyclable, but only 30% of this waste is recycled (Khalaf, 2004). 2.3 Recycling in Gaza Strip: As a result for the huge amounts of debris after the last war on Gaza Strip 2009, and due to the shortage of the natural materials in addition to the limited size of municipal landfill sites to accommodate large quantities of debris, the recycling of these materials gains a lot of interest and a potential uses were discussed and studied. Two main projects for crushing and recycling these debris where established UNDP crushing project and Governmental project UNDP Project The UNDP owns a crusher with 800 to 1000 ton daily capacity, which crush and discharge a grade of (0/10) cm located in the land known previously as (GANOR settlement).this crusher is shown in Figure 2.2. Figure 2.2: UNDP Crusher-Khanyounis-south of Gaza The UNDP project is divided into four stages: Stage 1: Collecting the debris which contains a lot of materials: concrete, steel, wood, brick, toxic materials, explosive objects. Stage 2: Sorting of the previous materials and the hand separation of elements. 7

19 Chapter 2 Literature review Stage 3: Preliminary crushing of sorted debris in order to prepare it to enter the crusher which requires the max size of 70 cm so the crushing is to 50 cm pieces Stage 4: Charging sorted debris into the crusher Government Project: Governmental Project is divided into three stages: Stage 1: The removal of debris.the government in Gaza strip started the removal process with a productivity of 20,000 tons/month. Figure 2.3 shows a dredger removing destroyed building debris. Stage 2: The separation process. Stage 3: The crushing process. Figure 2.3: Crusher removing destroyed building debris. According to the governmental information: There are 4 crushers in Gaza strip working with a rate of 3300 ton/day, and the amount of debris need to be crushed is estimated about 1,200,000 tons (Jendia & Besaiso 2011). 2.4 Physical and Mechanical Properties of RCA in Gaza Strip: In order to investigate the potential uses of RCA, investigation of Physical and Mechanical properties of this material firstly needed. These properties will play a major role in determining the most suitable uses of the RCA. The main properties needed to be reviewed are: grading, relative density, porosity, water absorption, strength, shape, and surface texture. 8

20 % Passing Chapter 2 Literature review Many researches and studies in Gaza strip were carried out focusing on the potential uses of RCA in Gaza Strip, and determine the main properties of it, and to test the applicability of using it in different engineering applications. The main two applications that most researchers focusing on were: using of RCA as alternative for natural aggregates in concrete mixes, and using it for road subbase layer. But in this review another application will be considered, which is to investigate the applicability of using RCA which contains concrete and crushed hollow blocks as main parts as aggregates in HMA for the binder coarse in low traffic roads. Some of the results obtained by the previous researchers will be reviewed in the following sections Sieve Analysis: The sieve analysis "gradation test" shows the distribution of aggregate particles, by size, within a given sample in order to determine compliance with design, production, control requirements, and verification of specifications. And as mentioned before two types or crushers in Gaza strip used, Jendia & Besaiso (2011) conducted the sieve analysis tests for samples of both crushers Governmental and UNDP, the gradation curves were as shown in Figure 2.4 and 2.5, respectively Sieve opening (mm) Figure 2.4: UNDP sample gradation curve 9

21 % Passing Chapter 2 Literature review Sieve size (mm) Figure 2.5: Governmental sample gradation curve Ghuraiz et al. (2011) conducted the gradation tests for different types of RA in Gaza strip in order to examine the effect of using it on the creep behavior of concrete, two types of coarse aggregates were used RA1:crushed concrete only, and RA2:mix of concrete and crushed block in addition to a recycled fine aggregates. The sieve tests results for these three types and comparison with the natural material available in Gaza are shown in Table 2.1 where the terms Adasia and Semsemia are the common names referred to the maximum size in the sample. Adasia (max size 5/8", 16mm) and Semsemia (max. size 3/8", 10mm). Table2.1: Sieve analysis for different types of natural and recycled aggregate Analyzing the gradation results, it show that the percentage of the coarse material is high, but is acceptable for some application such as road applications. 10

22 Chapter 2 Literature review Impact Value Test For aggregate impact value test, the sample of the aggregate is placed in a cylindrical container where a standard hammer falling 15 times under its own weight. The impact value is determined as a percentage passing on 2.36 mm size sieve. The high value percentage denotes a low performance of aggregate or lower strength. Aggregate Impact Values Toughness indicate aggregate strength properties. Aggregate Impact Values, (AIV's), less than 10% are regarded as strong, and AIV's above 35% would normally be regarded as too weak for use in road surfaces. BS 812 part 112 (BSI, 1990) prescribes the following maximum values of the average of duplicate samples: 25% when the aggregate is to be used in heavy-duty concrete floor finishes. 30% when the aggregate is to be used in concrete pavement wearing surfaces. 45% when to be used in other concrete applications. The value for impact test reported by Jendia & Besaiso (2011) was 21.89% which indicate that the tested material is suitable for the above mentioned applications according to BS Other Tested Properties The other main properties for the material tested by Ghuraiz et al. (2011) can be summarized in Table 2.2 for coarse aggregates RA1: crushed concrete only, and RA2: mix of concrete and crushed block and Table 2.3 as well as for fine aggregates. Table 2.2: Main properties of recycled coarse aggregates in Gaza strip after Ghuraiz et al. (2011). Aggregate Type Natural Aggregate (semsemia) Unit weight kg/m 3 Specific gravity (Dry) Absorption % Fine material <0.075mm % RA RA

23 Chapter 2 Literature review Table 2.3: Recycled fine aggregate properties compared with natural sand after Ghuraiz et al. (2011) Property Natural Sand Recycled Fine Aggregate Dry unit weight (kg/m 3 ) Moisture content 0.50% 1.75% Absorption 0.60% 7.90% Bulk specific gravity Fineness modulus 1.54% 2.01% % passing 0.6 mm 98.50% 91.70% From the previous properties it is clearly shown RCA which contains considerable amount of hollow blocks has a good properties comparing with natural materials, so it could be a beneficial to use it as alternative source in engineering applications, thus more investigations and tests should be done to find determine it is suitability for using in HMA binder coarse. 2.5 Economical Assessments of Recycled Aggregate: A good understanding for the economic aspects affecting the process of aggregate recycling is useful in estimating the applicability of using Recycled material in different engineering applications. Some studies discussed this issue were reviewed and the information of the economical assessment of recycled aggregate obtained can be presented as below: Crushing cost of recycled aggregate ranges is between 4 and 6 $/ton (about ). This cost includes crusher operation cost and maintenance as well as labor cost. Transportation cost of debris to the recycling facility ranges between 1.8 and 2.2 $/ton (about ) in average. Labor cost lies between 18 and 22 $/day (6-10 ) for each worker. There is no land lease cost because the land of recycling facility is granted from local government. Based on information mentioned above, production cost of recycled aggregate is approximately 20 $/ton (6 /ton). Production cost includes crushing, transportation and land lease cost. On the other hand, importing cost of natural aggregate is 18 $/ton (10 /ton). It can be concluded that production cost of recycled aggregate is lower than importing cost of natural aggregate (Jendia & Besaiso 2011) Problems Encountered in Recycling In construction industry, adopting new types of material is always facing conservatism thus; some countries have taken several years to develop the wide 12

24 Chapter 2 Literature review adoption of recycled materials some of the difficulties may be encountered are summarized below: a) Less confidence using new construction materials and their properties and the long-term performance; b) There is no enough experience in the use of these materials locally; c) Insufficient Specifications and technical practice; d) Uncertainties on the steady supplies of the recycled materials; e) The possibility of cheap supplies of natural aggregate from neighbourhood areas; f) No obligation of landfill charges and in some countries (Chan & Fong 2002). Applying these considerations on the situation in Gaza strip it is clearly shown that most of these problems are not applicable, and as an economical and environmental point of view, Recycling and reuse DD is the solution for this material. In the following sections the potential uses will be discussed mainly the possibility of using DD in asphalt mixtures. However other possibilities were discussed before by some researchers, showed acceptable results for using it as subbase for road constructions and as alternative for natural aggregates in concrete mixtures, but there is still some limitation in using it and no considerable projects have been done yet. 2.6 Potential Uses of Recycled Aggregates: The recycled demolishing debris or rubbles have been used for different engineering applications such as, road base and subbase and for production of new structural concrete up to strength of 20 MPa also it can be used as filler in asphalt mixtures. Many researchers around the world have been investigating the potential uses of the recycled aggregates; they mainly focused on recycled concrete aggregates and uses of it in concrete structures or on road subbase. Poon et al. (2002) reported: the replacing of coarse and fine natural aggregates by recycled aggregates with 25% and 50% had a slight effect on the compressive strength of the paving blocks. Investigations of the effects of recycled fine aggregate and recycled aggregates made from building rubble which contains concrete, bricks and tiles on the mechanical properties of recycled concrete mixtures have been done by Chen et al (2006) and the results showed that the 13

25 Chapter 2 Literature review different rubble from buildings could be considered as useful recycled aggregate if it have a proper processing. And they indicated that the modulus of elasticity for recycled concrete was around 70% that of normal concrete, also using recycled fine aggregates in concrete mixtures have a significant effect on reduction of concrete strength, and in order to achieve High-strength concrete, an increase in cement would be needed. However, this would not be an economical mixture proportion. According to Rustom et al. (2007), limited research were carried out in Gaza to investigate the potential uses of recycled RA, the main fields covered were; concrete mixes, road construction as subbase and base coarse, The results can be summarized below: Concrete made with RA has a less compressive strength 27-30% compared with that of natural aggregates, in road construction, investigations for using RA as subbase and base coarse shows that no swelling was noticed in any CBR test and the results of physical tests showed the potential us of crushed materials in road constructions. However, these studies showed some acceptable results from a mechanical point of view, other environmental consideration should be studied to investigate the environmental effects of using this Using RCA in HMA The design of HMA involves determining an economical blend of aggregates that provides a combined gradation within the limits of the specifications. and a determination of the percent of asphalt binder to be mixed with the aggregate blend, which meets volumetric specifications and to evaluate the performance of the designed mixes. it is needed to test the different properties of the mixes according to the specification requirements to investigate its properties. Paranavithana & Mohajerani (2006) performed experiments on the effects of RCA on properties of HMA, 50% RCA was used as coarse aggregates in HMA, the performance tests carried out on this mix compared with the mix NA showed that the use of RCA in HMA decreases the resilient modulus and creep resistance of the mix. Also this increases the stripping potential of mix. In addition, the mixes containing RCA showed large variations of strength under dry and wet conditions. 14

26 Chapter 2 Literature review One of the recent studies carried out in this field was conducted by Pérez et al. (2011), where they investigated the possibility of designing HMA using construction and demolishing debris DD as a coarse aggregates for low volume roads. Samples containing 0%, 20%, 40% and 60% recycled aggregates were tested in several tests to determine its mechanical and physical properties. All tests were conducted according to the Spanish General specification. The recycled aggregate fractions was (0/40mm) and its composition were as follows (72.5% concrete, 21.5 stone, 4% miscellaneous bituminous, 1% ceramic material and 1% impurities),two types of filler -Portland cement and lime - were used to investigate the effects of the different types of filler on the behaviour of HMA with recycled aggregates. The following tests were conducted: 1. Marshal test This test is designed to evaluate the suitability of Aggregates for road pavement by determining the optimum value of binder content to archive maximum density and stability with acceptable flow or deformation under load. So that the results obtained for the recycled aggregates can be compared with mixtures with Natural Aggregates (NA). Eight specimens were designed according to the Spanish specification, four of these (C0 C20 C40 C60) were with Cement filler and recycled coarse aggregates with percentages of 0% 20% 40% 60% respectively, and others (L0 L20 L40 L60) were with lime filler with same percentages of RCA as for cement filler. They reported that the results were acceptable by Spanish specifications for low volume roads. Also the specific gravity decreases as the percentage of coarse RA increases. They refer this to the increasing of the mortar attached to coarse RCA, that can be translated to lower in Unit weight of mixtures, and increase in voids in mineral aggregates (VMA).So in order to satisfy the specified air void contents (VA) an increase in binder content is needed. Observing the effect of filler type it can be seen that for lime filler the increase in coarse RCA percentage followed by decreasing in stability and increasing in deformation, however this relation is not valid for cement filler. Also it can be observed that a stiffer mixes can be obtained using cement filler, which may be due to the large amount of moisture absorbed by the lime or may be due to chemical reaction between the lime and the mortar. The results they obtained from marshal test are shown in Table

27 Chapter 2 Literature review 2. Wheel Track Test: The wheel tracking test is used to evaluate the resistance to permanent deformation, they reported they carried out the test according to Spanish specifications where the permanent deformation rate (PD rate) must be lower 20µm/min. and all the obtained results were below the limit also the results showed decreasing in PD while the percentages of coarse RA increases. The obtained results are shown in Table Immersion compression Ratio Test: In this test the effect of water on compressive strength of mixture can be evaluated, where cylindrical samples can be prepared with the marshal optimum asphalt content, then determining the index of retained strength. The index of retained strength is calculated using equation 2.1: S Index of retained strenght (%) 100 S Where: S1 is the compressive strength of a dry specimen and S2 is the compressive strength of an immersed specimen 2 1 (2.1) The results they reported for this test show that the retained strength ratio (RSR) are insufficient where the minimum acceptable value is 75% and the resulted values were in the range of 50-70% and that causes durability problems some reasons for this insufficient values may be due to the cement mortar that may brakes during the compaction, or it is may be due to the absorption of binder that reduces the effective binder covering the aggregates. More results can be shown in Table 2.4. Table 2.4: Mechanical test results by Pérez et al. (2011) Mills-Beale & You (2010) studied the mechanical properties of asphalt mixtures containing Recycled Concrete Aggregates (RCA) for low volume traffic where in 16

28 Chapter 2 Literature review their hypothesis, RCA would perform better for low trafficked volume road. The ASTM and AASHTO specification were used in their study, also a Superpave TM mix performance specifications were used to assess the mix design. Firstly tests of the RCA themselves were conducted specific gravity, void content, and resistance to degradation (Los Angeles LA), the RCA passes all the required specifications except for LA where the maximum of 40% for HMA to be used as a surface coarse. And the average results obtained was 43%, however a combination of RCA and Virgin Aggregate VA-RCA would be adequate for HMA. So samples of 25%, 35%, 50% and 75%RCA were prepared and tested. And the results they represented were: 1. Volumetric Analysis: According to the superpave TM Specification standards, a nominal maximum aggregate size of 9.5mm for ESAL level of 1 million ESAL required, minimum VMA 15%, VFA ranges between 65% and 75%. The obtained results compared with this specification shows that with increasing the percentages of RCA, VMA decreases while air void increases, that may be due to the surface pores on the RCA which leads to asphalt absorption and reduce the effective asphalt content. 2. Dynamic modulus at various temperatures and loading Frequencies The test of the mixes was done at 13, 21.3, and 39.2 C, and 25, 10, 5, 1 and 0.1 Hz frequencies. And the results of different percentage of recycled aggregate are presented in the form of logarithmic master curve are in Figure 2.6. This Figure shows that the dynamic modulus (stiffness) decreases as more RCA added to HMA. Figure 2.6: Dynamic Modulus of selected VA-RCA by Mills-Beale & You 17

29 Chapter 2 Literature review 3. IDT resilient modulus The resilient modulus values can be determined by using cores of HMA materials using the repeated load indirect tensile test as in Figure 2.7. Resilient modulus values can be used with structural response analysis models to calculate the pavement structural response to vehicle wheel loads. At temperatures 5, 25 and 40 C, the resilient modulus is to be determined in order to understand insightfully the effect of temperature and loading rate on the mix. Figure 2.7: The resilient modulus test setup The results found by the researchers indicate that increasing percentage of RCA decreases the resilient modulus. Also it is proved that the test temperature is responsible for this difference more than the percentage RCA in the mix. 4. Moisture susceptibility: According to the Their the minimum permissible tensile strength ratio should be 80% in order to have an asphalt mixture that sufficiently resists moisture and water-related damage, otherwise known as stripping. The test can be conducted at 25 C. The test results they reported shows that, all specimens have a tensile strength ratio more than 80% which is within the specification except that for 75% RCA. Also it is shown that as the percentage of RCA increases the degree of moisture susceptibility increase. 18

30 Chapter 2 Literature review 5. Rutting failure potential: The results obtained by the researcher indicate that increasing percentages of RCA leads to increase in permanent deformation; however it satisfied their specification which is 8mm. Wen & Bhusal (2011) investigated the feasibility of using RCA as HMA aggregate. They evaluated the effects of RCA on performance behaviour of HMA including fatigue cracking, thermal cracking, rutting, and moisture susceptibility. Five different samples were prepared using five different percentages of RCA (20%, 40%, 60%, 80%, and 100%) blended with virgin aggregate. The tests for aggregate properties were conducted for the samples with the different RCA percentages, It was found that 100% RCA met most of their local specification, but failed the degradation factor for moisture suitability. However when it was blended with 20% Natural aggregate it satisfy the specification requirements. Different laboratory experiments were carried out to investigate the mix properties. The results show that mixes with RCA were highly absorptive and the porous structure leads to low specific gravity. The increase of RCA percentage leads to an increase of asphalt content. The use of RCA significantly reduced the tensile strength at both intermediate and low temperatures, resulting in reduced resistance to rutting, fatigue, thermal cracking and moisture damage. Similar study carried out in Kuwait by Aljassar et al. (2005) where they used up to 70% of recycled coarse aggregates in asphalt mixture and they reported that produced HMA met all the requirements of the Kuwait specifications. The optimum binder content was 7.2%. Wheel-track test was conducted as per BS 598 part 110, the exhibited rutting depth at 45 C and at 70 C was 2.4mm and 12.2mm respectively which less than the maximum by specification 15mm, Immersion compression ratio obtained was 92% compares with minimum 70% as per specification, Loss of stability test results was also acceptable where the obtained value was 24% less than the maximum which is 25%. So as conclusion for these tests it is feasibly to use the RCA in HMA. General conclusion for the previous investigations, show that some researchers have reported that HMA made with coarse RA exhibited sufficient durability and volumetric and mechanical properties compared with their local specifications. However in contrast, other researcher have indicated that, at first, HMA made with RCA presented acceptable volumetric and mechanical properties, but due to the action of water, it proved to have insufficient durability also the samples with RCA needed more binder content, and this may be uneconomical approach. 19

31 Chapter 2 Literature review As a result, in this line of investigation there are controversial opinions among researchers. For this reason, more investigation needed to evaluate the possibility of using RCA as coarse aggregates in binder coarse in HAM pavement. Also it is important to make a comparison investigation for the different specification and the different tests mentioned above to remove the clue and to have clear and sufficient information for future investigation. Some other researchers investigated the use of fine recycled aggregates such as (Wong et al. 2007) investigated the feasibility of using fine waste concrete aggregates (<3 mm) as partial substitution of granite aggregates in hot-mix asphalt (HMA) and the conclusion was affirmative. Ahmed et al. (2006) investigated the effect of using waste cement dust as mineral filler on the mechanical properties of asphalt mixture, and the results indicated cement dust can totally replace limestone powder in asphalt paving mixture. One of the recent research carried out by Chen et al. (2011) studied the feasibility of using Recycled Fine Aggregate Powder (RFAP) having size rages between (0-18)mm as filler in HMA. Several tests were conducted including indirect tensile tests (IDT), three point bending tests, dynamic creep tests, water sensitivity tests and fatigue tests, these tests were conducted according to AASHTO specifications, the results of these tests will be reviewed and discussed bellow: 1. Indirect Tensile Tests (IDT) Modulus is the most important parameter of asphalt mixtures in pavement deign. This tests was conducted under 5 C, 25 C and 40 C, for two different samples: one with lime powder (LP) filler and the second with RFAP filler. The obtained results shown in Figure 2.8 which indicates that at 5 C and 40 C the samples with RFAP filler exhibit a higher modulus and that may lead to better rutting resistance. 20

32 Chapter 2 Literature review Figure 2.8: The indirect tensile strength results obtained by Chen et al. (2011). 2. Low and high temperature properties: Three point bending test were conducted to evaluate the low-temperature cracking resistance performance, and the results show that using RFAP may cause a slightly decreasing in low temperature performance comparing with asphalt mixtures with LP. They also carried out creep tests to investigate the potential rutting of mixture at high temperature and they reported that mixtures with LP have higher creep strains than that with RFAP filler, which indicates that the mixtures with RFAP have higher stiffness modulus at high temperatures. From these tests it can be included that asphalt mixtures with RFAP are more suitable for hot regions. 3. Water sensitivity: The water sensitivity of asphalt mixtures can be evaluated by measuring the loss of indirect tensile strength after one cycle, two cycles, and three cycles, of freezethaw cycles at 25 C. the results reported by the researchers shown in Figure 2.9, which shows that using RFAP as filler in asphalt mixture have higher tensile strength than the samples of recycled aggregates. Figure 2.9: IDT results for water sensitivity tests obtained by Chen et al. (2011). 21

33 Chapter 2 Literature review 4. Fatigue Life Test: The fatigue life of asphalt mixture can be evaluated using the four-point bending stress test under the controlled strain mode. The results of this test obtained by the researchers are shown in Figure 2.10 which indicates that the asphalt mixture with RFAP exhibit higher fatigue life at each microstrain than the mixture with L.P Figure 2.10: Fatigue life test results after Chen et al. (2011). In general all previous tests show that utilization of RFAP as filler can improve the water sensitivity, high-temperature properties and fatigue life of asphalt mixture. However, RFAP may cause a small decrease of the low-temperature performance of asphalt mixture. So that means using RFAP as filler in asphalt mixture is feasible, especially in hot regions. However, further study on field performance should be carried out to support the reviewed results. 2.7 Conclusion: The objective of this review is to investigate the potential uses of recycled aggregate in Gaza Strip which contain different fragments such as hollow blocks, tiles and as well concrete wastes for using in HMA as a binder coarse in road pavement. Firstly, the properties of the recycled aggregates in Gaza strip were reviewed and the studies showed that RCA have comparable properties to the NA so it is feasible to use it in different engineering applications. Also the economical assessment supports these findings. However, the feasibility of using the RCA in HMA shows that there is a controversial opinion among the researchers. The main findings of the reviewed studies can be summarized in Table 5 22

34 Chapter 2 Literature review Table 2.5: Summary of RCA test results It can be seen that the findings were inconsistent and largely depended on the sources of RCA used. In addition, the laboratory tests employed by the previous researchers were conducted according to their limitations and specifications in different countries. Therefore, study is needed to address RCA physical properties (specific gravity, absorption) and their effects on mix design properties (volumetrics) and performance of mix, based on performance tests, thus more investigation needed to evaluate the possibility of using RCA in Gaza strip in HMA pavement roads. Finally, more extensive research is needed especially to study the durability behaviour of HMA made with RA from DD waste. 23

35 Chapter 3 Road Pavement and specifications 3. ROAD PAVEMENT AND SPECIFICATIONS In this chapter a summary about pavement types and the specification of the binder coarse in Gaza Strip will be presented. 3.1 Road Pavement A highway pavement is a structure consisting of superimposed layers of processed materials above the natural soil sub-grade, whose primary function is to distribute the applied vehicle loads to the sub-grade where it is sufficiently reduced it, so that will not exceed the bearing capacity of the soil. The pavement structure should be able to provide a surface of acceptable riding quality, adequate skid resistance, favorable light reflecting characteristics, and low noise pollution (Mathew, 2007). There are two types of asphalt pavement: flexible pavement where the wheel load stresses transmits to the lower layers by grain-to-grain transfer through the points of contact in the granular structure, and rigid pavements have sufficient flexural strength to transmit the wheel load stresses to a wider area below. The type of pavement, which used in Gaza Strip, is the flexible pavement, which usually consists of specific materials that positioned on the Natural subgrade a typical cross section of the flexible pavement is shown in Figure 3.1. Figure 3.1: Typical cross section of the flexible pavement 24

36 Chapter 3 Road Pavement and specifications Each layer of these layers has its specifications and requirements in the design of the road sections: Surface Course It is a layer, which is directly in contact with traffic loads, so it contains the high quality materials, and it is usually constructed with dense graded asphalt concrete. It must be strong to resist the distortion under traffic and provide a smooth and skid resistant riding surface. Binder course This layer provides the bulk of the asphalt concrete structure. Its main purpose is to reduce the stresses which affect the base course. It is usually consist of aggregates having less binder and does not require high quality as the surface course. In addition to that role of the binder course, it must be designed to resist the abrasive forces of traffic and reduce the amount of water that goes through the pavement layers. Base course It is the layer of material directly beneath the binder course and it provides additional load distribution and contributes to the sub-surface drainage. Sub-Base course The sub-base course is the layer beneath the base course and the main functions are to provide structural support and reduce the intrusion of fines from the subgrade in the pavement structure also it help to improve drainage. Sub-grade It is the top soil of the natural soil prepared to receive the stress from the layers above so that required it to be compacted to a desirable density to satisfy the needed properties (Mathew, 2007). 3.2 Mix Design Mix Design aims to determine the exact proportions of bitumen, aggregates and fillers to achieve the required properties for the pavement layer such as workability, strength, durability, stability and to ensure economical mix. Traditional mix design methods are established to determine the optimum asphalt content that would perform satisfactorily, particularly with respect to stability and durability. There are different methods for mix design that used around the world; one of the most widely accepted method is Marshal Mix design method and Hveem mix design method. Furthermore, a recent method can be used as 25

37 Chapter 3 Road Pavement and specifications alternative for marshal and Hveem methods is called Superpave Method (Asi, 2007). In this study the marshal method was used in sample preparing, this method will be discussed later in chapter 4. Design of asphalt mix consists of the following steps: Select the type and gradation of the aggregates, select type and grade of binder, and Select the optimum binder content to satisfy the specific requirements for mix properties. Some of the main properties of desired from the mixture most of projects are summarized by Lee & Mahboub (2006) in Table 3.1 Table 3.1: The desired properties of Asphalt mixtures Property Definition Mix Variables Which have Influence Stiffness Relationship between stress and Aggregate gradation strain at a specific temperature Asphalt stiffness and time of loading Degree of compaction Water sensitivity Asphalt content Stability Resistance to permanent Aggregate surface texture deformation (usually at high Asphalt gradation temperature and long times of Asphalt stiffness loading- conditions Asphalt content Degree of compaction Water sensitivity Durability Resistance to weathering effects Asphalt content (both air and water) and to the Aggregate gradation abrasive action of traffic. Degree of compaction Water sensitivity Fatigue Resistance Ability Of mix to bend repeatedly Aggregate gradation. without fracture Asphalt Content. Degree of compaction. Asphalt stiffness. Water sensitivity. Fracture Characteristics Strength of mix under single Aggregate gradation. tensile stress application. Aggregate type. Asphalt Content. Degree of compaction. Asphalt stiffness. Water sensitivity. Permeability Ability of air, water, and water Aggregate gradation. vapor to move into and through Asphalt content. mix. Degree of compaction Workability Ability of mix to be placed and Asphalt content. compacted to specified density Asphalt stiffness at placement. Aggregate surface texture. Aggregate gradation. 26

38 Chapter 3 Road Pavement and specifications 3.3 Binder Course Specification The road specifications for each layer are important to control the production of asphalt pavement and to judge the suitability of the used material in this layer. Each country has its different road specifications and the most famous specifications are American Society for Testing and Materials ASTM 3515-D-4 (ASTM, 2004), British Specification (BS 594). In Gaza strip the specifications for the road and pavements are taken from the above standards or from the Arab countries such as Egyptian specifications (Egyptian Code for development of the urban and rural roads). Some projects implemented by international organizations in Gaza Strip, sometimes have their own specifications and requirements, such as the United Nation Development Program in Gaza UNDP (UNDP specifications, 2012) International Specifications (ASTM D3515-D-4) The asphalt grading for the binder course in this specification are used and it is limits are shown in Table 3.2 and Figure 3.2 (ASTM, 2004). Table 3.2: Gradation of Asphalt Binder course (ASTM D3515-D-4) Sieve size (mm) Percentage by Weight Passing Min Max

39 % Passing Chapter 3 Road Pavement and specifications Sieve Size (mm) Figure 3.2: Gradation of Asphalt Binder course (ASTM D3515-D-4) Some of the mechanical properties for the binder course specified by the ASTM D3515-D-4 are the air voids percentages in the mixture which limits are between 3% and 5%, Bitumen content in the mixture is in the range between 4.5%and 6% Egyptian Specification The Egyptian specification also is used in Gaza Strips in many projects and it has specifications for gradation and for volumetric properties. The gradation limits are presented in Table 3.3 and Figure 3.3 (MOHU, 1998). Table 3.3 Gradation of Asphalt Binder course in Egyptian specification Percentage by Weight Passing Sieve Size (mm) Lower Upper

40 % Passing Chapter 3 Road Pavement and specifications Sieve Size (mm) Figure 3.3: Gradation of Asphalt Binder course Egyptian specification The mechanical properties that required by the Egyptian specification for the binder course such as the Marshal stability and flow, some of the volumetric properties for the mixture such as the air void percentages, Voids in Mineral Aggregates (VMA) and bitumen content are shown in Table 3.4 Table 3.4: The Mechanical Properties of the Egyptian Asphalt Binder Course Property Value Stability (Kg) 272 Flow (mm) 2-4 Air voids in mix (% ) 3-8 VMA (%) 15 No. of Marshal blows 50 Bitumen content (%) Specifications Required By UNDP Projects in Gaza Strip United Nations Development Program (UNDP), which is a Program of Assistance to the Palestinian People, has many pavement projects in Gaza Strip. The required gradation for the binder layer is shown in Table 3.5 and Figure 3.4 (UNDP specifications, 2012). 29

41 % Passing Chapter 3 Road Pavement and specifications Table 3.5: Gradation of Asphalt Binder course required for UNDP projects Sieve Size (mm) Percentage by Weight Passing In mm Lower Upper 3/4'' /2'' /8'' No No No No No Sieve Size (mm) Figure 3.4: Gradation of Asphalt Binder course required for UNDP projects Also in the specification by the UNDP some mechanical properties are required, these properties are shown in Table 3.6 where V.F.B. is the voids filled with bitumen. Table 3.6: The Mechanical Properties of the Egyptian Asphalt Binder Course Property Value Stability (Kg) 900 Flow (mm) 2-4 Air voids in mix (% ) 3-7 Min VMA (%) 13.5 V.F.B. (%) Bitumen content (%) 3-6 No. of Marshal blows 50 Maximum density of Mixture(Kg/m 3 ) >

42 % Passing Chapter 3 Road Pavement and specifications 3.4 Conclusion There are different specifications for the Binder course layer are used in Gaza Strip and there are different requirements for each specification, the comparison between different gradation requirement is shown in Figure 3.5 From Figure 3.5, it can be seen that the ASTM has the widest gradation limits while the Egyptian specifications has the narrowest gradation, Also it shows that the gradation required by the UNDP is coarser. Regarding to the Mechanical properties it seems that there are some minor differences between the specifications in Air voids, VMA, and binder content. However all these three specifications are used in Gaza Strip, so to investigate the applicability of using the recycled blocks in HMA, the obtained results in this research will be compared with all the three specifications above. 100 UNDP 90 EGYPT 80 ASTM Sieve Size (mm) Figure 3.5: Gradation of different specifications in Gaza Strip 31

43 Chapter 4 Experimental program 4. EXPERIMENTAL PROGRAM 4.1 General The principal reason of conducting this work is to evaluate the applicability of using the RCA in Gaza Strip as an alternative for the NA in HMA for the binder course layer. It can be recognized from the literatures, there is no any similar studies has been done before in Gaza Strip for using the RCA in asphalt binder course. However some researchers around the world conduct some tests to investigate the properties of asphalt mixtures with RCA and compare it with their national specifications. Examples of these studies: Aljassar et al. 2005; Chen et al. 2006; Mills-Beale & You 2010; Pérez et al. 2012). This project is based on laboratory tests on the limestone NA that is similar to the aggregates used in Gaza Strip, and recycled Hollow blocks which is obtained by crushing a medium density cement block to the required size. Some tests carried out on the bitumen and Hot mixed asphalt samples prepared with different percentages of recycled aggregates to investigate the performance and mechanical properties of asphalt making with this recycled aggregates, and finally to compare it with the specifications in Gaza Strip. This chapter describes the materials used in the experiments and the tests and standards followed in this experimental program. It also presents a comprehensive description of the work. 4.2 Materials Bitumen One type of bitumen was used to produce all test specimens in this study so the effect of different types and percentages of coarse aggregates in the samples can be investigated. The used bitumen was 70/100 grade binder, it was supplied by Shell bitumen in UK. Some tests were conducted on this bitumen showed that the penetration was 86 dmm and softening point of 47.8 C and this in the acceptable range in ASTM specification used in Gaza which required dmm and Softening point between C. The density of the bitumen was determined and it was 1.02 Mg/m 3. 32

44 Chapter 4 Experimental program Fine Aggregates One type of fine aggregates or dust, which passes through the 4mm sieve, was used during the experiments. By using one type of fine aggregates, the effect of different types of coarse aggregates in the mixture can be studied. Figure 4.1 below show the fine aggregates used in the experiments. Figure 4.1: Fine limestone aggregates Natural Coarse Aggregates The natural limestone coarse aggregate used in this investigation which is similar to the aggregates that are used in Gaza Strip for pavement projects. Aggregates of maximum 20 mm size were used. A single size of 20, 14, 10 and 6mm were used to prepare the gradation curve of the dense asphalt concrete, which had been successfully used before to produce a good quality mixture in Gaza Strip and in UK. The main purpose of using the natural aggregates is to make a comparison with the recycled aggregates in different tests conducted through the experimental work. Tarmac Dene Qurray provided this limestone to the Nottingham Transportation Engineering Centre (NTEC) at the University of Nottingham. It was observed that the limestone aggregate particles have smother surface. Figure 4.2 shows the different sizes of the limestone aggregates used in the experiments. 20mm 14mm 10mm 6mm Figure 4.2 Different sizes of the limestone coarse aggregates 33

45 Chapter 4 Experimental program Recycled Aggregates The recycled aggregates used in the experiments were obtained by crushing a Medium Density Block 44x21.5x10 cm provided by Wickes in Nottingham. These blocks have a compressive strength of 3.6N/mm 2. The blocks were crushed using a crusher to produce recycled aggregates with a maximum size of 20mm and with different coarse aggregates single sizes as for natural aggregates 20, 14, 10, and 6 mm. Then these aggregates were sieved and used to produce the gradation curve later. The main reason for using this type of blocks to be recycled in this study, is that a similar type of blocks with the same strength is used in most buildings in Gaza Strip and it comprises more than 70% of the materials in rubbles generated by demolished houses in Gaza Strip. The other 30% mainly consists of crushed concrete and tiles. The concrete is stronger than the blocks and its properties have been tested by many researchers as shown in the literature, however, the block properties and its performance in HMA are still less known. Therefore, it is a good opportunity to find the effect of the blocks itself on the mixtures and to study its applicability to be used as recycled aggregate in HMA. Figure 4.3 shows the crushed block aggregates. 20mm 14mm 10mm 6mm Figure 4.3 Different sizes of the Recycled Coarse Aggregates 4.3 Aggregate Tests In order to compare the recycled coarse aggregates with the natural aggregates properties and to determine its suitability for pavement projects, the properties of aggregates should be studied first. The sieve analysis test, particle density tests, and absorption test were conducted in the Nottingham Transportation Engineering Centre (NTEC) Laboratory at the University of Nottingham. 34

46 Chapter 4 Experimental program Sieve analysis The sieve analysis was carried out on both aggregate types NA and RCA in accordance with BS EN 933 part 1 (2012); the main purpose of this test was to determine the percentage passing from asset of sieves and compare it with the limits used in Gaza Strip. The chosen gradation was 0/20 mm dense asphalt concrete, so both aggregates will be within the limits and then the varying aggregate types can be investigated Particle Density and Water Absorption The particle density and the absorption test of the coarse aggregate were conducted according to the British standard BS EN 1097 Part 6 (2000). The Pyknometer method for aggregate particles between mm was used. This test mainly conducted to determine the particle densities of RCA and compare it with the NA. This also will be used in preparing the mixture of HMA samples to be tested. This also will affect the properties and performance of the mixture. In this test the percentage of water absorption is determined and the particle densities of each individual single size of the aggregates 20, 14,10,6 mm and the fine aggregate can be determined. This result can affect the optimum binder content in the mixture and also it will have some effect on the adhesion between the aggregates and the Bitumen. 4.4 Sample Preparation The experimental program is based on making samples of NA to be the base for comparison as a control, and then making samples of NA with various percentages of RCA 30% then 60% in the mixture. Several samples of each mixture were prepared using marshal compaction method with different percentages of Binder content as follows (5%, 5.3%, 5.7% and 6%).The concept is based on preparing 3 samples of each binder contents, so 12 samples of each mixture type were prepared and then tested for their properties. 35

47 Chapter 4 Experimental program Marshall Method After preparing the gradation curves for the three mixtures: NA, NA with30% RCA and NA with 60% RCA, then trial mixes for each mixture type were carried out in NTEC laboratory using various bitumen content percentages (5%, 5.3%, 5.7% and 6%). Marshall Method was used for preparing and compaction of the samples and following steps were carried: 1. Selecting the aggregates grading to be in the specification limits. 2. The required mass of aggregates was weighed and then heated to 150 C for 24 hours. 3. The needed quantity of bitumen was weighed out and heated to 150 C. 4. The aggregates and the bitumen were poured into the mixing bowl and then carried out the manual mixing until the all aggregates are coated with bitumen, bearing in mind that the mixing temperature should be in the same range 150 C. 5. Marshall sample mould which is mm diameter and 76.2 mm high was heated in the oven to the same temperature as aggregates. 6. A filter paper was used in the bottom of the mould and the mixture was poured into the mould. 7. The mould was placed on the compaction machine which gives the mixture 50 blows on the top surface then the mould was reversed for another 50 blows on the second surface. The blows were done with a Kg compacting hammer falling freely from a height of mm. The 50 blows were used because in ASTM the specification for the low traffic road 50 blows for marshal test are required. 8. The specimens then were left to cool to room temperature on a smooth flat surface. 9. The samples were carefully extruded from the mould and labeled with sample number. 10. Finally, the marshal samples with mm diameter and 76.2 mm height were trimmed to 40 mm height, to be used in Nat machine test for stiffness and fatigue test since this is the required sample thickness by the specifications for stiffness and fatigue test. Figure 4.4 shows the Marshall samples before trimming. 36

48 Chapter 4 Experimental program NA NA +30% RCA NA+60% RCA Figure 4.4: Marshall Samples for different mixtures Finding Optimum Bitumen Content The optimum Bitumen content is the bitumen content that achieve the best performance of the mixture so it seeks to choose the bitumen content at desired density that satisfy minimum stability and range of flow values. The Marshal Method can use any suitable method for determining the optimum bitumen content and usually depend on the local procedures and experience. It is basically selected based on the combination of the results of Mix density analysis, air void analysis and Marshall Stability and flow. The procedures below can be followed by Roberts et al. (1996) to determine the optimum bitumen content. 1. Plot the following graphs: Bitumen content vs. density. Generally density increases by increasing bitumen content until reach the maximum then decreases. Bitumen content vs. air voids, where the air voids should decreased by increasing the bitumen content. Asphalt binder content vs. voids in mineral aggregates (VMA),its purpose is to provide more space for sufficient bitumen to satisfy the adequate adhesion and durability without bleeding when temperature rise and bitumen expands. The typical curve of the VMA against Bitumen content is a flat curve decreases by bitumen increasing until reaching the minimum, then increases again. Bitumen content vs. voids filled with Asphalt-bitumen- (VFA). VFA increases with increasing asphalt content, it is a percentages of VMA Bitumen content vs. flow and bitumen content vs. stability where the stability increases until reach the beak, the decreases. 2. After plotting the graphs the bitumen content corresponding to 4% air voids is selected, this is the optimum bitumen content. 3. The mixture properties at this optimum bitumen content are determined referring to the plots, and these properties are then checked against the 37

49 Chapter 4 Experimental program specifications if they are all within the limits, then this optimum bitumen content is satisfactory. Otherwise, the mixture should be redesigned. A summary of these steps and sample of the typical relations between bitumen content and different mixture properties are shown in Figure 4.5. Figure 4.5 Selection of Optimum Bitumen Content (by Roberts et al., 1996) The optimum binder content can carried out in accordance to the procedure and design criteria proposed by the design manual of the Asphalt Institute (Asphalt Institute Manual, 1993). Using the property curves and the specified limits for these properties according to the specifications, the narrow range of acceptable bitumen contents that pass all criteria can be drown and then the optimum bitumen content will be in the middle of this range. This method was used in this study to determine the optimum bitumen content. As a result for using more than one specifications in Gaza Strip a narrow range of the limits satisfy all used specifications was prepared and these limit are shown in Table

50 Chapter 4 Experimental program Table 4.1: Marshall property limits to satisfy all specifications Property Limits Air voids, % 3-5 Minimum VMA, % 15 V.F.B, % Bitumen content In this study, in order to produce the needed plots to determine the optimum binder content, the density voids analysis were determined according to the European standard specifications. However, the stability and the flow tests were not performed in the NTEC laboratory and the plots resulted from density voids analysis only used for determining the Optimum binder content The tests and procedures will be presented in the following sections Density Voids Analysis Densities and voids are used in all mix design methods for determining the main HMA physical properties. The two measures of the densities are required for this analysis, Asphalt maximum density which was determined by BS EN part 5 (2009), and asphalt bulk density which was determined using BS EN part 6 (2003). Then these densities are used for calculating the voids volumetric properties of the mixture. The measured voids expression used are, Air voids (V m ) which is the voids in the total mixture, The voids content in the mineral aggregates (VMA), The percentage of the voids in the aggregate filled with bitumen (VFB) BS EN part 8 (2003) was used for calculating the air voids Maximum Density The maximum density is the mass of sample per unit volume without air voids. There are three procedures discussed in BS EN part 5 (2009) specifications for determining the maximum density: volumetric procedure, hydrostatic procedure, and mathematical procedure. In this study the mathematical procedure was used since the apparent densities of all aggregates used in the mixtures where determined before and the bitumen density was determined as well. The proportion of each component in the mixture was determined during samples preparation stage. So Equation 4.1 was used to calculate the maximum density of the mixture 39

51 Chapter 4 Experimental program m 100 p / p /... pb / a1 a1 a2 a2 b (4.1) m is the maximum of the mixture in (Mg/m 3 ) p a1 is the proportion of aggregate 1 in the mixture (by mass), in per cent (%); a1 is the apparent density of aggregate 1 in (Mg/m 3 ) ; p a2 is the proportion of aggregate 2 in the mixture (by mass), in per cent (%); a2 is the apparent density of aggregate 2 in (Mg/m 3 ) ; p b is the proportion of binder in the mixture (by mass); b is the density of the binder in (Mg/m 3 ) Bulk Density Bulk density of the mixture is the mass per unit volume, including the air voids, of the sample. The mass of the sample can be obtained by weighing the dry sample in air and the volume can be obtained from the difference of the sample weight in air and its weight in the water. In the BS EN part 6 (2003) there are four different procedures for determining the bulk density. The used procedure in this study was Bulk Density-Sealed specimen (foil method) where the following procedures were carried out: 1. Determining the mass of dry sample (m1). 2. Determining the water density which depends on the water temperature (ρ w ). 3. The samples were sealed in foil keeping the internal voids as a part of the volumetric material and no extra voids between the seal and the sample. 4. The mass of the sealed sample were determined (m2). 5. The mass of the sealed sample immersed in water bath were determined (m3). 6. The bulk density of the sealed sample can be determined from equation 4.2 bsea m m m m m / / w 2 1 sm (4.2) Where: is the bulk density sealed in (Kg/m3) ; bsea m1,m2,m3 are the masses as mentioned above in grams (g); is the density of the water at test temperature in (Kg/m 3 ) ; w is the density of the sealing material at test temperature in (Kg/m 3 ). sm 40

52 Chapter 4 Experimental program Air void Analysis The European Standard BS EN part 8 (2003) describes the method for determining two main volumetric characteristics of the compacted bituminous samples: the air voids content (V m ) and the voids in the mineral aggregate filed with binder (VFB). The air voids content of a bituminous specimen is calculated using the maximum density of the mixture and the bulk density of the specimen. The percentage of air voids in the mixture can be calculated as shown in equation 4.3 V m m b 100% m (4.3) Where: V m is the air void content in the mixture in per cent; is the maximum density of the mixture in (Kg/m 3 ); m is the bulk density of sample in (Kg/m 3 ). b To calculate V.F.B., the Voids in the Mineral Aggregate (VMA) is required. VMA is the volume of intergranular void space between the aggregate particles of a compacted mixture expressed as a per cent of the total volume of the specimen. When VMA is too low, there is not enough space in the mixture to add sufficient asphalt binder to adequately coat the aggregate particles. Mixes with a low VMA are more sensitive to small changes in asphalt binder content. (Roberts et al., 1996). The VMA can be calculated from equation 4.4: VMA V m B b % B (4.4) Where: VMA is the per cent of voids content in the mineral aggregate; V m B is the per cent of air voids content in the mixture; is the per cent of the binder content in the sample; b is the bulk density of sample in (Kg/m 3 ) ; B is the density of the bitumen in (kg/m3). 41

53 Chapter 4 Experimental program The percentages of the voids in the aggregate filled with binder (VFB) can be calculated as shown in equation 4.5: VFB B b / B VMA 100% (4.5) Where: VFB is the percentage of the voids in the mineral aggregate filled with binder; B is the maximum density of the mixture in (Kg/m 3 ); is the bulk density of sample in (Kg/m 3 ) ; b B VMA is the density of the bitumen in (kg/m3); is the percentages of the voids in the mineral aggregate. The previous volumetric parameters were calculated for the samples at the four different binder contents and the relationships between them against the binder content were plotted to find the optimum binder content as mentioned above. 4.5 Performance Tests Many tests can be used to assist the performance of the HMA samples, these tests includes stiffness test, fatigue test, repeated load axial test and moisture susceptibility test. In this study, experimental work includes two performance tests to be carried out in the NTEC laboratory. These tests are the stiffness test and the fatigue test the two tests were carried out on all samples with different binder content and different types of aggregates. The relationship between the stiffness against bitumen content and the fatigue results against the bitumen content were prepared to compare the effect of the RCA at different bitumen content and at the optimum binder content as well. However, more tests are required for more confidence of the results and more information about the performance of the HMA with RCA Indirect Tensile Stiffness Modulus (ITSM) Indirect Tensile Stiffness Modulus Test (ITSM) is a simple and rapid test method for measuring stiffness modulus of asphalt mixture, which is the most important input for pavement design to obtain the structural behavior in the road. 42

54 Chapter 4 Experimental program Stiffness modulus is dependent on a number of factors such as: asphalt mixture composition, binder grade and level of compaction as well as of test conditions (temperature, loading time and the stress magnitude at elevated stress level). The test is normally carried out on 100mm or 150mm diameter samples a thickness between 30mm and 75mm can be used for the tested samples. In this study, the Marshall samples were trimmed to 40mm thickness to fit this test. The test was conducted according to the European standard BS EN part 26 (2004) using NAT equipment. Principle of ITSM test is that cylindrical specimen is exposed to repeated sinusoidal compressive loads through the vertical diameter plane, which develops a relatively uniform tensile stress perpendicular to the direction of the applied load and along the vertical diametral plane. The resulting horizontal deformation of the specimen is measured and an assumed Poisson s ratio is used to calculate the tensile strain at the centre of the specimen. According to the BS EN part 26, stiffness modulus are calculated using measurements from the 5 load pulses and using equation 4.6: Where: S m stiffness modulus (MPa) F applied vertical load (N) Poisson ratio (0.35) z h S m F 0.27 z h amplitude of horizontal deformation (mm) thickness of the sample (mm) (4.6) The testing conditions for all samples were : temperature 20 o C 0.2 o C, rise time 124 milisecs, mean horizontal deformation 5μm. The samples were tested in tow direction without relaxation time between testing. The two tested diameters were perpendicular to each other and the mean value of the stiffness for the second diameters test should be in the specified limits by EN part 26 which is - 20% and +10% of the mean value recorded for the first position. Figure 4.6 shows one sample testing for ITSM using NAT machine. All the samples at different binder content were tested and the relationship between the mean stiffness and the bitumen content were plotted to investigate the performance of the different mixtures at different bitumen content and comparing them. 43

55 Chapter 4 Experimental program Figure 4.6: ITSM test of samples using Nat machine Fatigue Test (ITFT) The principle of ITFT test, like with ITSM test, is that cylindrical specimen is exposed to repeated sinusoidal compressive loads through the vertical diameter plane, which develops a relatively uniform tensile stress perpendicular to the direction of the applied load and along the vertical diametral plane (see Figure 4.7). The resulting horizontal deformation of the specimen is measured and an assumed Poisson s ratio is used to calculate the tensile strain at the center of the specimen. The fatigue life is defined as the total number of load applications before fracture of the specimen occurs. There are two main types of fatigue test: controlled stress and controlled strain. In a controlled stress test the magnitude of the applied stress pulse is maintained constant until failure. In a controlled strain test the magnitude of the strain is maintained constant during the test. Whereas failure usually occurs relatively soon after crack initiation under controlled stress condition the crack propagation in controlled strain is generally a considerable portion of the total test period. In controlled strain testing, therefore, the test is usually terminated when the stiffness modulus of the specimen has fallen to certain percentage of the stiffness modulus at the start of the test. The controlled stress test was used in this study. Fatigue Test (ITFT) is normally carried out on samples of 100mm diameter by 40mm thickness of asphaltic materials. Before fatigue testing, the stiffness modulus of each sample should be determined at the stress to be used in the fatigue test. The Indirect Tensile Stress Test (ITST) is the best method for doing this. 44

56 Chapter 4 Experimental program The ITST test is a non-destructive method for measuring the stiffness modulus of asphaltic paving materials at selected horizontal stress. For the same samples and at the same temperature which will be used for the fatigue test. The NAT machine was used to find the stiffness modulus at 10 o C and 500 KPa horizontal stress. The test was carried out for all the samples from different mixtures at different bitumen content and the results of this test ware used in calculating the horizontal strain for the fatigue test. The fatigue test was carried out in according to DD ABF(2003), the testing temperature was 10 o Cand the horizontal stress of 500KPa was used. Three samples were tested at each bitumen content and number of cycles to the failure against the bitumen content was plotted for different mixtures and compared with each other. Figure 4.7:ITFT test of the samples using Nat machine The horizontal strain then was calculated and also plotted against the bitumen content for the different mixtures to be compared. The horizontal strain was calculated using equation

57 Chapter 4 Experimental program Where x max x max S m (4.7) x max Is the maximum horizontal tensile stress at centre of sample (micro-strain); x max is the maximum horizontal tensile stress (KPa) ; is the Poisson s ratio assumed to be 0.35 S m is the Indirect tensile stiffness modulus at the same stress for fatigue The tensile stress at the center of the sample can be calculated form equation 4.8. x max 2F D h (4.8) Testing ITFT at 20 o C In this study firstly the ITFT was conducted at 20 o C and 500 KPa horizontal stress, but the obtained results was surprisingly unexpected, since the fatigue life was decreasing with the increasing of bitumen content. The results also show that all samples have very low number of cycles to failure which was in the range of cycles, and the corresponding horizontal strain were relatively high which was about 700 micro-strain.it was noticed that the samples have been deformed too much during the test before breaking. Figure 4.8 show some of the tested samples for ITFT at 20 o C. Figure 4.8: Samples tested for ITFT at 20 o C 46

58 Chapter 4 Experimental program These unexpected results can be explained by that the 500 Kpa horizontal stress may was too high and that explain why the number of cycles to failure was low, this high stress also was responsible for the high strain alongside with the lower stiffness at this temperature. Some suggestions for using lower stresses further research to be used in and check the results. However in this study lower temperature was used to according to the fact that the Asphalt samples will be stiffer at lower temperatures, so the Horizontal strain would be reduced and fatigue life would be increased. Also the compaction method used for preparing the samples may have some effect on these results, since the sample faces were not smooth have some and this may affect the sitting of the sample in the testing machine. The decreasing of fatigue life with increasing the bitumen content can be explained by the large deformation noticed so may be during the test the deformation has the most effect than the fatigue. And this small number of cycles to failure cannot easily show the real trend of the fatigue since this difference between the samples was not much. 47

59 Chapter 5 Results and discussion 5. RESULTS AND DISCUSSION This chapter provides a description of the tests conducted. It also analyses the results and compares the it with the specifications. Some calculations are provided in this chapter; however, more details, calculations and spreadsheets that used for preparing the results are enclosed in Appendix (A). 5.1 Tests Results Determination of Particle density and water absorption As mentioned in chapter 4 the particle density for both NA and RCA were conducted according to BS EN 1097 Part 6.The results are presented in Table 5.1 and 5.2 for NA and RCA respectively.(for detailed calculation refer to Appendix A). Table 5.1: Particle density test results for NA Aggregate size 20 mm 14 mm 10 mm 6 mm Dust Apparent particle density (Kg/m 3) Water absorption (% of dry mass) Table 5.2: Particle density test results for RCA Aggregate size 20 mm 14 mm 10 mm 6 mm Apparent particle density (Kg/m 3) Water absorption (% of dry mass) Gradation test The results of each single size of the NA and RCA 20, 14, 10, and 6 mm were obtained from the sieve analysis tests that conducted according to the British Standard BS EN 933 part 1 (2012). As mentioned in chapter 4. Then these results were used to carry out the best percentages of each size to design the gradation curve for each mixture to meet the specifications. The results of the sieve analysis tests are shown in Table 5.3 and 5.4 for NA and RCA respectively. 48

60 Chapter 5 Results and discussion Table 5.3: NA gradation test results for different aggregate sizes Sieve size % Pass 20 mm 14 mm 10 mm 6 mm 31 mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm Pan Table 5.4: RCA gradation test for different aggregate sizes Sieve size % Pass 20 mm 14 mm 10 mm 6 mm 20 mm mm mm mm mm mm mm mm mm mm mm mm mm mm Pan The calculated percentages of each aggregate size and the final design curve for NA which used in mixture design are shown in Table 5.5 while a comparison with the specification limits are shown in Figures 5.1 to

61 % Passing Chapter 5 Results and discussion Table 5.5: NA gradation curve used in mixture design Aggregate 20 mm 14 mm 10 mm 6 mm Dust (%) Size Passing % Weight mm mm mm mm mm mm mm mm mm mm mm mm mm mm Pan NA 10 ASTM limits Sieve Size (mm) Figure 5.1: Comparing NA gradation with ASTM limits 50

62 % Passing % Passing Chapter 5 Results and discussion Sieve Size (mm) Figure 5.2: Comparing NA gradation with Egyptian limits NA Egyptian gradation limits NA UNDP limits Sieve Size (mm) Figure 5.3: Comparing NA gradation with UNDP limits The gradation Table and the used percentages of each aggregate single size for preparing the RCA-30% mixture are shown in Table 5.6 and the comparison of the gradation with specifications are shown in figures 5.4 to

63 Chapter 5 Results and discussion Aggregate Size % Weight Table 5.6: RCA-30 gradation curve used in mixture design 20 mm 14 mm 10 mm 6 mm Dust NA RCA NA RCA NA RCA NA RCA (%) Passing 31.5mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm Pan

64 % Passing % Passing Chapter 5 Results and discussion RCA-30% Sieve Size (mm) Figure 5.4: Comparing RCA-30% gradation curve with ASTM limits RCA-30% 10 Egyptian limits Sieve Size (mm) Figure 5.5: Comparing RCA-30% gradation curve with Egyptian limits 53

65 % Passing Chapter 5 Results and discussion RCA-30% 10 UNDP limits Sieve Size (mm) Figure 5.6: Comparing RCA-30% gradation curve with UNDP limits For the RCA-60%, table 5.7 shows the percentages of each individual aggregate size used for preparing the mixture gradation curve with 60% RCA. Figures compare the prepared gradation with specifications. Aggregate Size % Weight Table 5.7: RCA-60 gradation curve used in mixture design 20 mm 14 mm 10 mm 6 mm NA RCA NA RCA NA RCA NA RCA Dust (%) Passing 31.5mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm Pan

66 % Passing % Passing Chapter 5 Results and discussion RCA-60% ASTM limits Sieve Size (mm) Figure 5.7: Comparing RCA-60% gradation curve with ASTM limits RCA-60% 10 Egyptian limits Sieve Size (mm) Figure 5.8: Comparing RCA-60% gradation curve with Egyptian limits 55

67 % Passing Chapter 5 Results and discussion 100 RCA-60% 90 UNDP limits Sieve Size (mm) Figure 5.9: Comparing RCA-60% gradation curve with UNDP limits Maximum density of the mixture The maximum density of the mixture has been calculated according to BS EN part 5 (2009). From the equation 4.1 as discussed in section , using the percentages of each size of aggregates in each mixture as shown in Tables and its corresponding apparent density from Tables 5.1 and 5.2 and using the measured density of the bitumen of 1.02 Mg/m 3. The calculated maximum densities at different binder content for the different mixtures are shown in Table 5.8 (for detailed calculation refer to Appendix A) Table 5.8: The maximum density of the mixtures at different binder contents Bitumen % NA RCA-30% RCA-60% 5 % % % % The results of density voids analysis The marshal properties against the bitumen percentages for different mixtures were plotted and compared in Figure Then the property curves for each mixture type were drawn separately to be used for determining the optimum 56

68 Chapter 5 Results and discussion binder content for each mixture. The results are shown Figures 5.11, for NA, RCA-30% and RCA-60% respectively. The determination of the optimum content was carried out in accordance to the procedure and design criteria proposed by the mix design manual of the Asphalt Institute (Asphalt institute manual 1993). Using the property curves and the specified Marshal design criteria specified, the narrow range of acceptable bitumen contents that pass all criteria can be drawn in Figures 5.14, 5.15, and 5.16 then the optimum binder content can be determined as the mid bitumen content in this range. 57

69 V.F.B., % Air voids, % VMA, % Air voids vs Bitumen content Bitumen content, % NA RCA- 30% V.F.B. vs Bitumen content- RCA-60% Bitumen content, % Bulk density, Kg/m VMA% vs Bitumen content Bitumen content, % Bulk density vs Bitumen content Bitumen content, % Figure 5.10: Comparing Marshal property curves for different mixtures 58

70 V.F.B,% Bulk Density (Kg/m3) Air voids, % VMA, % Max 5 Min 3 Air voids vs Bitumen content Bitumen content, % Max 75 Min 60 % V.F.B vs Bitumen content % Bitumen Content Min 15 VMA% vs Bitumen content % Bitumen Content Bulk density vs Bitumen content % Bitumen Content Figure 5.11: Marshal property curves for NA mixture 59

71 VFB, % Bulk density, Kg/m3 Air voids, % VMA,% Max 5 Min 3 Air voids vs Bitumen content Bitumen content, % Max 75 Min 60 VFB vs Bitumen content Bitumen content, % Min 15 VMA% vs Bitumen content Bitumen content, % Bulk density vs Bitumen content Bitumen content, % Figure 5.12: Marshal property curves for RCA-30% mixture 60

72 V.F.B., % Air voids, % VMA, % Air voids vs Bitumen content- RCA-60% Max Bitumen content, % Max 75 Min 60 V.F.B. vs Bitumen content- RCA-60% Bitumen content, % Bulk density, Kg/m VMA% vs Bitumen content- RCA-60% Min Bitumen content, % Bulk density vs Bitumen content- RCA-60% Bitumen content, % Figure 5.13: Marshal property curves for RCA-60% mixture 61

73 Chapter 5 Results and Discussion To calculate the binder content as mentioned before, the Figures were used. Thus, the optimum bitumen content of the NA mixtures was 5.5% with acceptable variation of bitumen content from the optimum of ±0.15%. Similarly the optimum bitumen content of the mixtures with 30% RCA was found to be 5.85% ± 0.15%. And for the mixture with 60% RCA it was found that some criteria such as the air voids was not achieved in the acceptable range for bitumen content by the specifications, thus it may be little bit higher than 6% since the other criteria were achieved in this range. Low BC Acceptaple BC High Passes all criteria Optimum BC =5.5% VFB VMA Air voids Bitumen content, % Figure 5.14: Determining the optimum bitumen content for NA mixture Low BC Acceptaple BC High Passes all criteria Optimum BC =5.85% VFB VMA Air voids Figure 5.15: Determining the optimum bitumen content for RCA-30% mixture 62

74 Stiffness, MPa Chapter 5 Results and Discussion Low BC Acceptaple BC High Optimum BC > 6 VFB VMA Air voids Figure 5.16: Determining the optimum bitumen content for RCA-60% mixture Indirect Tensile Stiffness Modulus The indirect tensile stiffness modulus (ITSM) was determined with the use of NAT equipment and in accordance to BS EN part 26 (2004). The testing conditions for all samples tested were: temperature 20 o C±0.2 o C, rise time 124 milisecs, and mean horizontal deformation 5μm. The average mean value of stiffness moduli for each bitumen content for the different mixtures are shown in Figures Stiffnes vs Bitumen Content for NA y = x R² = Bitumen content, % Figure 5.17: Average stiffness modulus at different bitumen content for NA 63

75 Stiffness MPa Stiffness MPa Chapter 5 Results and Discussion Stiffnes vs Bitumen Content y = x R² = Bitumen content % Figure 5.18: Average stiffness modulus at different bitumen content for RCA-30% 9000 Stiffnes vs Bitumen Content Bitumen content % Figure 5.19: Average stiffness modulus at different bitumen content for RCA-60% 64

76 Nomber of cycles to falilure,n Stiffness, MPa Chapter 5 Results and Discussion A comparison between the stiffness of the three different mixtures can be shown in Figure Stiffnes vs Bitumen Content NA 500 RCA-30 RCA Bitumen content, % Figure 5.20: Average stiffness modulus at different bitumen content for different mixtures Indirect Tensile Fatigue Test Results The determination of the indirect tensile fatigue characteristics of the mixtures was carried out with the NAT equipment according to the DD ABF/2003() method. The testing temperature was 10 o C ±0.2 o C. The fatigue life against the bitumen content for the different mixtures are shown graphically in Figures Number of cycles vs Bitumen content -NA Bitumen content, % Figure 5.21: Variation of number of fatigue cycle to failure with bitumen content for NA 65

77 Nomber of cycles to falilure Nomber of cycles to falilure Chapter 5 Results and Discussion Fatigue life at 500KPa and 10 C- RCA-30% Bitumen content Figure 5.22: Variation of number of fatigue cycle to failure with bitumen content for RCA-30% 4500 Fatigue life at 500KPa and 10 C- RCA-60% Bitumen content Figure 5.23: Variation of number of fatigue cycle to failure with bitumen content for RCA-60% 66

78 Stiffness, MPa Nomber of cycles to falilure Chapter 5 Results and Discussion A comparison between the different mixtures Fatigue life is shown in Figure Cycles to failure at 10 C vs Bitumen Content NA 5000 RCA-30 RCA Bitumen content, % Figure 5.24: Comparing fatigue characteristics for different mixtures The horizontal strain corresponding to each sample was calculated from equation 4.7 and as mentioned in section The stiffness modulus S m was calculated at the same temperature (10 C) used for calculating the horizontal strain. The mean stiffness modulus at each bitumen content is shown graphically in Figure 5.25 for the different mixtures. ITST at 10 C Vs Bitumen Content- RCA NA RCA RCA Bitumen content, % Figure 5.25: Mean stiffness modulus at different bitumen content at 10⁰C 67

79 Horizontal strain (microstrain) Horizontal strain (microstrain) Chapter 5 Results and Discussion The horizontal strain then calculated and the results are shown in Figures for NA, RCA-30% and RCA-60% respectively 250 Horizontal strain Vs Bitumen content-na Bitumen content, % Figure 5.26: Calculated horizontal strain for NA at different bitumen content 250 horizontal strain Vs Bitumen content- RCA-30% Bitumen content Figure 5.27: Calculated horizontal strain for RCA-30% at different bitumen content 68

80 Horizontal strain (microstrain) Chapter 5 Results and Discussion horizontal strain Vs Bitumen content-rca Bitumen content Figure 5.28: Calculated horizontal strain for RCA-60% at different bitumen content 69

81 Chapter 5 Results and Discussion 5.2 Results Discussion This study was conducted to investigate the possibility of using RCA, (which is mainly from recycled cement hollow blocks with nominal strength of 3.6N/mm 2 ) in HMA, and investigate its effect on the performance of the asphalt mixtures Particle density and water absorption The Particle density and water absorption result were as expected where the RCA has a lower density compared with the NA. There was a significant difference between the NA and recycled aggregate densities, which is around 400 Kg/m 3. Therefore, it is important to notice that an adjustment is required before blending and mixing the different aggregates in order to obtain the correct volume of the materials to be mixed. This lower density obtained was due to the high porosity of the used blocks also as a result of the irregular shape of the particles of the RCA which will results in more space occupied by the aggregates, thus reduce the density. The results show that RCA has very high water absorption of about 12% in average and this high per cent will result in increasing of optimum bitumen content. However, there are no limits for the water absorption in the specifications but the decision of using this material will depend on other properties of the asphalt mixture which reflect the aggregates properties such as the apparent density and the water absorption. The higher water absorption may be as a result for the higher porosity of the RCA and due to the chemical characteristic of the cement blocks used in this study. So more investigations and tests for the chemical properties of the RCA are needed for future studies. The obtained results from this test were in good agreement with the results presented by Mills-Beale & You (2010) and Pérez et al. (2012). However the obtained water absorption percentages in this study were higher. Pérez et al. (2012) refers the high water absorption percentages to the attached mortar with the RCA The gradation test For the gradation test, it can be seen from Table 5.3 and 5.4 that for both NA and RCA the individual aggregates are of single size aggregate, which mean that the most of this aggregate passes one sieve and returned on the next smaller sieve size. For example the 14 mm aggregates from the RCA, 99.6% passes the 14 mm sieve and only 11% passes the 10 mm sieve and this make it easier to prepare the final gradation curve to be used in the mixture. Table 5.5 shows the selected percentages of each aggregate size of the NA to prepare the dense grading curve. The 20 mm dense grading was used because it proved a good performance in hot asphalt mixtures, and it can be seen from 70

82 Chapter 5 Results and Discussion Figures 5.2 to 5.5 that this grading satisfies all specifications where it lays in the middle of the ASTM gradation limits. However it closer to the upper limits of the Egyptian gradation limits and lower limits of UNDP specifications which have a narrower limits than the ASTM. Similarly, for RCA-30%, many trials were conducted to choose the percentages of the NA and RCA to achieve the gradation of the specifications and the final percentages are presented in Table 5.6. In this table, the total coarse aggregate size in the mixture is 60%. Thus the 30% of this will be 18% of the total mixture. this 18% RCA percentages were as follows: 4% for both 20 mm and 14 mm and 5% for both 10 mm and 6 mm aggregates. Since it is believed that the RCA are weaker than the NA, then the larger particles of RCA are not preferable in the mixture and that what the above percentages reflect. Figures proof that the selected grading curve for the RCA-30% satisfies all specifications. Similarly for RCA-60% it can be seen from Figures that the prepared curve satisfies the specifications, however for the UNDP limits it just at the lower limits and cross it in some points but it still acceptable The maximum density The maximum density of the mixture presented in Table 5.8 shows that the maximum density decreases with the increasing the percentages of the RCA in the mixture, and it decreases by increasing the bitumen content in the mixture. These results are logical results since the density of the RCA are lower than the NA density. It is obvious from equation 5.1 that using higher percentages of lower density materials leads to lower maximum density. And it is the same for the bitumen content where its density is lower than the aggregates, which is 1.02 Mg/m Marshall Properties and Optimum Bitumen Content The volumetric analysis and Marshall properties in Figure 5.10 confirm some results reported by other studies (e.g. Khalaf, 2004; Lee et al. 2012; Pérez et al. 2012). It proves that the air voids in HMA increases with increasing the incorporation of RCA. It also shows that the VMA increase with increasing the RCA percentages in the mixture and as result for this the VFB decreases. It also shows that the bulk density of RCA is lower than the NA. In Figures (which used for determining the optimum bitumen content of the Na, RCA-30% and RCA-60% respectively), It can be seen that the relationship between the different properties with the bitumen content are as expected and it is combatable with the typical relations presented in chapter 4. 71

83 Chapter 5 Results and Discussion For NA, it can be seen from Figure 5.11, that air voids decreasing linearly with the increase of bitumen content. For voids in mineral aggregates, it can be seen that a polynomial relationship of the order of 2 can be used to represent the obtained values. The typical relation start from a higher VMA values then decreases until reaching a minimum value at optimum bitumen content then start to increase again, this relation can be seen in Figure 5.11 for VMA. The minimum value for VMA specified by the specification is 15% and this was satisfied for all bitumen contents used in this study. As a result of increasing of VMA the V.F.B. increased with the increasing of bitumen content reaching the maximum acceptable V.F.B. by specification which is 75% at a bitumen content of 5.7%. For the air voids to satisfy the requirements of the specification of 3-5%, a minimum 5.3% bitumen content required for NA. From the above and from Figure 5.14, the optimum bitumen content can be determined to be in the narrow range that satisfies all tested criteria required by the specifications, it can be seen this ranges between 5.3% and 5.7% thus the optimum bitumen content can be selected as 5.5% with acceptable variation of ± This range also satisfies the required properties at the optimum binder content where it provides the minimum VMA and maximum density and acceptable air voids. Similarly for the RCA-30% it can be seen from Figure 5.12 that the relations between the different properties and the bitumen content as the typical relations. It is obvious that the VMA has a higher value at 5% bitumen content then start decreasing and reach the minimum value at 5.8% then increases again it satisfy the specifications for all bitumen continent. The air voids that satisfies the criteria are for the bitumen content higher than 5.7%. For V.F.B. bitumen contents greater than 5.28% are required to satisfy the minimum specifications of 60%. Thus, from this and from Figure 5.15 the optimum bitumen content for RCA-30% should be in the rang to satisfy all specifications and the maximum allowable bitumen content of 6%. So 5.85% will be the optimum bitumen content for RCA- 30% with acceptable variation of ± 0.15.This range also satisfy the maximum bulk density and min VMA with the acceptable air voids. For the RCA-60%, it can be seen from Figure 5.13 that the property curves are changing significantly with the variation of the Bitumen content, specially for air voids which started at 15% air voids for 5% bitumen content and decreasing linearly with the increasing of bitumen content to be 7% air voids at 6% bitumen content. However, it is still greater than the maximum allowable air voids in the 72

84 Chapter 5 Results and Discussion mixture of 5%. The higher air voids percentage may be due to the increasing of the coarser aggregate percentages in the mixture from the RCA where the 20 mm and 14 mm RCA count about 18% from the total aggregates in the mixture and counts 30% of the of the coarse aggregate percentages in the mixture. This high amount of coarser recycled aggregates with the irregular surface and the high porous material responsible for the increasing of the air voids in the mixture. These large recycled aggregate particles are weaker than the natural aggregates, so it results in reducing the stiffness of the asphalt mixture. So it is advisable for the future studies and experiments to use smaller amounts of the larger recycled aggregate particles and to use some types of fillers which will results in reducing the air voids in the mixture and increase the stiffness. It is clear from Figure 5.13 that the other properties such as VMA and V.F.B. satisfy the specification requirements. A closer look at these curves, it can demonstrate the findings shown by the air void curve, that the optimum bitumen content cannot be in this rang of the examined bitumen content, since the VMA still decreasing and did not reach the minimum value in this range. Similarly, the same thing can be shown form the Bulk density curve, it increases with the increasing of bitumen content, however it did not reach a maximum then decreases again. That demonstrate that the optimum binder content to satisfy all the criteria and the logical relations between Marshal properties and bitumen content will be grater then 6% which is the maximum allowable percentage by ASTM specification. Generally it can be seen that the optimum binder content increases with increasing RCA percentages in the mixture as shown above, 5.5% for 0% RCA and 5.85% for 30% RCA and increases to more than 6% by using 60% RCA in the mixture. It can be seen at the optimum binder content, the bulk density of the mixture decreases from 5353 Kg/m 3 for NA to 2260 Kg/m 3 for the RCA-30%. The reason for such increase in the bitumen content was the high porosity of the RCA and the rougher surfaces for their particles compared to the NA particles. And it is believed that materials with higher porosity absorb more bitumen due to the high number and size of pores. In addition, rougher surfaces require more bitumen to overcome the friction between the particles during the mixing of the asphalt. Along with this, and since the batching of the materials to prepare Marshall samples was by the weight, so the lower density of RCA means there is more coarse aggregate particles per mix as opposed to NA. This means the surface 73

85 Chapter 5 Results and Discussion area for the bitumen to cover is higher and more bitumen needed to ensure a good workability during the mix and to provide the best properties and performance. The finding of this study agrees with the previous studies (Khalaf, 2004; Lee et al. 2012; Pérez et al. 2012) Indirect Tensile Stiffens Modulus From the results presented in Figures 5.17 to 5.20, it was found that the mixtures with 30% RCA possess greater stiffness moduli than those with NA or with 60% RCA. The 60% RCA was found to possess the lowest stiffness moduli. In all cases the stiffness modulus decreases as the bitumen content increases. The relation between stiffness modulus and bitumen content was found to linear with correlation factors (R 2 ) were 0.74, 0.63 and 0.08 for NA, RCA-30% and RCA-60% respectively. The Stiffness modulus of the RCA-30% mixture at its optimum bitumen content was 3017 MPa compared to the stiffness modulus of 2400 for the NA at its optimum bitumen content. This means that, the stiffness has been increased by 25% using 30% of the RCA. These findings mean that using 30% of RCA increases the stiffness by 25% compared with the NA, and this corresponding to increasing of the optimum bitumen content from 5.5 to 5.85% (only 0.35%).This higher stiffness modulus means that the thickness of the asphalt layer can be significantly reduced when an analytical pavement design method is employed. However, more samples should be tested to support these findings and increase the confidence of the results. In general, mean standard deviation of the stiffness modulus values decrease as bitumen content increases. Greater variability of stiffness moduli results was found for the NA. The smaller variations were found to be exist for the RCA-60%. The standard deviation for the stiffness moduli for different mixtures are shown in Table 5.9. These results cannot be easily explained and further investigations are needed to find the some correlations between Marshall properties and the performance tests such as the stiffness and the fatigue. Table 5.9: the stiffness modulus and the standard deviation for different mixtures bitumen content, % Stiffness, MPa NA RCA-30% RCA-60% Standard deviation Stiffness, MPa Standard deviation Stiffness, Mpa Standard deviation

86 Chapter 5 Results and Discussion The results also show that the NA mixture is the most affected by the increasing of bitumen content in the mixture. It has the sharpest decreasing line with the increasing of bitumen content and the RCA-60% is the lowest affected by the increasing of bitumen content. The reason for the greatest stiffness for the RCA-30% mixture can be explained by the fact that the RCA presents a multiple sectional corners and it has irregular shapes and rough surfaces. This can lead to stronger abrasion forces resulting from the dislocation amount aggregates to cause the interlocking action after being compacted, thus enhancing the ability of resisting the sliding among aggregate and boost the ITSM. In this way, it improves interlocking action effect and strength among aggregates. By using 60% of RCA, the stiffness was very low compared to other mixtures at low binder contents, however at higher bitumen contents it possess mean stiffness modulus as the same as the for the NA. This very low stiffness at low bitumen content for the RCA-60% mixture, may be as a result of the lack of required binder to cover the aggregates and bond it together. other suggestions for this low stiffness may be the high air voids exist in the mixture and the low V.F.B means that the aggregates are not stick together and it can be easily reallocated in the mixture Indirect Tensile Fatigue Test From the results presented in Figures 5.21 to 5.24 it can be seen that, it in concurring with results of the ITSM test where the mixture with 30%RCA exhibits the highest fatigue life and the mixture with 60% RCA show the lowest fatigue cycles to failure. The results from Figure 5.25 show the stiffness moduli of the different mixtures at 10 C and it show that the RCA-30% possess the highest stiffness modulus, and this interpreted to the lowest horizontal strain for the RCA-30% and the highest horizontal strain for RCA-60%. At its optimum bitumen content, RCA-30% mixture has a fatigue life of cycles to failure compared to 8671 Cycle to failure for the NA at its optimum bitumen content. This surprisingly result means that the fatigue life for RCA-30% has been increased more than 100% by using 30% of RCA compared to NA, these results should be investigated more to increase the confidence and making a better judgment on using this material. The RCA-60% mixture has the lowest fatigue life at all bitumen contents, where the maximum exhibited fatigue life of 2800 was observed at 6% bitumen content. 75

87 Chapter 5 Results and Discussion The better performance of the RCA-30% may be explained as a result of the more adhesion between the RCA and bitumen, which resulted from the high absorption of the RCA. Since the presence of RCA in the mixture was with more smaller particles it is easy to distribute in the mixture during the mixing, and this results in increasing the adhesion force however no effect on fractional properties. For RCA-60%, it was noticed that the low fatigue life may be due to the presence of more larger RCA particles of 20 mm and 14 mm. and since the RCA are weaker than the NA it easy to break during the test and this can be clearly shown in Figures Figure 5.31demonestrate this for RCA-60%, where it showes the particles of the RCA were broken in the fatigue failure plan. Figure 5.29: The breaking plan of NA samples tested for ITFT 76

88 Chapter 5 Results and Discussion Figure 5.30: The breaking plan of RCA-30% samples tested for ITFT Figure 5.31: The breaking plan of RCA-60% samples tested for ITFT 77