rutting performance evaluation of polymer modified binder in HMA mix design


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rutting performance evaluation of polymer modified binder in HMA mix design

  1. 1. CHAPTER 1 INTRODUCTION 1.1 Background of study The deterioration of surface roads is defined by the damage type of its condition of the surface over time. The distress such as permanent deformation, cracking and disintegration is classified as pavement surface defects. Flexible pavement distress modes normally considered in the flexible pavement analysis and design is fatigue cracking, rutting and low temperature cracking (Thompson and Nauman, n.d.). In this case study, the focus is on rutting or permanent deformation because rutting is one of the common pavement distresses happen in Malaysia which lead to lower riding quality for road users and high maintenance costs. It describes that permanent deformation or rutting happens as a consequence of continuous loading including heavy load which lead to progressive accumulation of permanent deformation under continuous tire pressure. Rutting happened in the form of longitudinal depression across the wheel path due to the continuous application of axle loading. The factors that contribute to the rutting are coming from the excessive traffic consolidation in the upper layer of the pavement, plastic deformation due to the inadequate mixture stability and also instability caused by stripping of asphalt binder below the riding surface of the pavement (Ahmad et. al, 2011). It also stated that increase in temperature will result in rutting increases even though the traffic loading is under control and stability in HMA mixtures provided higher resistance against deformation 1
  2. 2. process under repetitive loading ( Hafeez, 2010). In order to limit the rut depth at the acceptable levels, careful attention must be made in surface layers and the subgrade. The polymer modified binder in asphalt has been shown in improving the strength and performance of the HMA pavement. Hence, binders such as latex and polyacrylate have been selected in this case study to be used with Hot Mix Asphalt as a binder. The comparison between modified asphalt and conventional asphalt also been made to see their rutting performance. There are four tests commonly used in monitoring rutting resistance of asphalt mixture such as repeated-load creep test, wheel tracking test, static creep test, indirect tensile test and Simple Performance Test (SPT). Many methods could be used in designing HMA mix, and the old methods are Marshall and Hveem methods where these methods are used in the early 1940s until mid-1990s. Research done by the Strategic Highway Research Program (SHRP) on asphalt binder and asphalt mixture has introduced the new method called Superpave (Superior Performing Asphalt Pavement). The Superpave Mix Design Method consist of a method for specifying mineral aggregates and asphalt binders, mixing design for asphalt and a procedure for analyzing and predicting the performance of the pavement. A major difference between Superpave mix design and other design methods, such as the Marshall ad Hveem methods, is that the Superpave mix design method mainly uses performancebased and performance-related characteristics as the selection criteria for the mix design (Garber and Hoel, 2010) 2
  3. 3. 1.2 Problem statement In recent years, the capacity on road increase since the increasing of vehicle ownership and development of world transportation. This kind of situation may lead to higher traffic volumes, traffic loads and tire pressure. These factors will increase pavement deformation such as the rutting. In Malaysia, permanent deformation or rutting is a failure that usually happens on flexible pavement. Rutting exists when the interlocking between aggregate and bitumen not really strong and happen in the form of longitudinal depression in wheel path. Another possible factor that causes rutting is improper mix design like the excessive asphalt content and an insufficient amount of aggregate particles in mixtures. The presence of rutting could reduce the serviceability life of the flexible HMA pavement and lead to certain safety risks as well. Furthermore, rut can lead to car accidents because it tends to pull a vehicle towards the rutted track as it is steered across the rut and it is also may cause the hydroplaning of the vehicle during rainy day as water filled up the rut. As road consumer, this study is significant in the sense of obtaining good quality of pavement which provided long term road serviceability. It is necessary to provide pavement which has good characteristics in term of durability, strength, moisture content and air void that can resist the formation of surface deformation. There are two principle solutions to construct a more durable pavement; first by applying a thicker asphalt pavement which will increases the construction cost and secondly making an asphalt mixture with modified characteristics (Moghaddam, 2011). There are several actions can be done in improving the HMA mixtures. One of action is using additives such as polymer modified binder in hot mix asphalt to increase durability of pavement 3
  4. 4. structures because additives have abilities to captivate amount of distress imposed by a continuous heavy traffic load. The aim of this study is to evaluate the rutting performance on the HMA mix design using latex and polyacrylate thus, to determine the most suitable modified binder to be used in order to minimize the rutting resistance on HMA pavement. This study shows comparisons between three types of polymer modified binder on Hot Mix Asphalt by using Superpave Design Method and evaluation of rutting performance on those mixes. 1.3 Objectives The main objective of this study is to evaluate the rutting performance on hot mix asphalt using polymer modified binder. To achieve this aim, the following secondary objectives must be carried out: i. To determine the rutting performance of Hot Mix Asphalt on Superpave mix design using unmodified and polymer modified binder. ii. To compare the rutting performance of Hot Mix Asphalt on Superpave Mixtures on unmodified and polymer modified binder. 1.4 Significant of Study The total volume of vehicles on the road keeps increasing every year which cause the pavement deformation such as rutting also increases. The existence of rutting is dangerous for road user since it accumulates water in the wheel path and this may lead to accidents and hydroplaning. Thus, it is necessary to improve pavement quality that can minimize pavement problems such as pavement deformation, cracking and surface 4
  5. 5. defects. It is also important to extend the service life of the road pavement by minimizing the rut depth and this can be done by improving the performance of asphalt mixture. The usage of modified binder and non-modified binder in HMA mixture bring a huge impact on performance of hot mix asphalt.So, the relationship between binder characteristics and mix results were evaluated to see the binder performance in term of rutting. From this study, the performance of rutting using control, latex and polyacrylate as a binder on hot mix asphalt is observed through Asphalt Pavement Analyzer (APA) machine. 1.5 Scope of Work The focus of the study is to evaluate the rutting performance of polymer modified binder in hot mix asphalt using Superpave Design Method through Asphalt Pavement Analyzer machine. The comparison between modified asphalt and non-modified asphalt as binder has been made to identify if the modified asphalt capable to strengthen the pavement sample in term of rut resistance. In addition, the selection of suitable modified binder against rutting can be done in this study. The specification used in preparing HMA sample is Superpave mix design with NMAS 19mm. In this study there are 2 types of polymer modified binder used which are latex and polyacrylate. The percentage of polymer modified binder used in hot mix asphalt was 8% for latex and 6% for polyacylates which these data are obtained from previous research work done by Atikah, 2013. The aggregates used in mix design is obtained from Blacktop Quarry in Jalan Templer, Rawang, Selangor. The binder used is penetration grade 80/100 where it is obtained from Port Klang. The performance of rutting on hot mix asphalt was monitor 5
  6. 6. through Asphalt Pavement Analyzer machine. In addition, the scope of the study also covers the following: i. Desk study. ii. Materials selection for aggregates and binders. iii. To compact and test the HMA mixtures trial blends using the Superpave Gyrator Compactor device. iv. Evaluation of rutting performance based on the compiled final design HMA mixtures using the Asphalt Pavement Analyzer machine. v. Data analysis and result. The general outline procedure of study was illustrated as shown in Figure 1.1. 6
  7. 7. Objective of the research Literature review Selection of material (Aggregates and Asphalt Binder) Preparation of HMA mix design sample at 7±0.5% air void Evaluation of Rutting Performance on the final compiled of Design Asphalt Mixture using Asphalt Pavement Analyzer (APA) machine No Achieved 7±0.5% air void? Yes Data Analysis and Result Conclusion Report Submission and Presentation Figure 1.1: The Outline Procedure of the Research Study (HMA using Superpave method and Asphalt Pavement Analyzer to evaluate the rutting performance) 7
  8. 8. CHAPTER 2 LITERATURE REVIEW 2.1 Introduction In the late 1950’s, test on the rigid and flexible pavement in Ottawa, Illinois was conducted by AASHO (American Association of State Highway Officials) to determine and identify how traffic can contribute to the deterioration of highway pavements. Through the information and data obtained, knowledge of designing pavement structure, pavement performance, load equivalencies and climate effects could be improve and expand. The results that obtained from the AASHO road test were used to develop design guides of structural pavement including the AASHTO Guide for the Design of Pavement Structures and develop empirical equations and calculations to be used for the design of pavement structures. Flexible pavement and rigid pavement are two types of pavement as shown in Figure 2.1. The scope of this study is focusing on the flexible pavement. The surface of flexible pavement must be high quality and strong enough in order to resist large axle loads and high temperature. Thus, flexible pavement is constructed with layers of different materials that the surface strength increase as move towards the surface (weakest layer on the bottom and strongest layer at the surface). Traffic load distribution of flexible pavement depends on the layered system over the subgrade. The layers of a flexible pavement structure basically consist of hot mix asphalt (HMA) at the pavement surface, with a stabilized base, base course gravel, and sub base course gravel. In Malaysia the 8
  9. 9. common flexible pavement structure normally consists of bitumen pavement, granular road base, drainage sub-base and the subgrade (Hassan and Sufian, 2008). The design of pavement structure must according to the Arahan Teknik (Jalan) 5/85 which is derived from the AASHO Road Test. Figure 2.1 Flexible and Rigid Pavement Cross Section 2.2 Asphalt Asphalt mixtures basically formed through the combination of asphalt cement, fine aggregates, coarse aggregates and other materials, which depend on the type of the mixtures. There are three types of asphalt mixtures that usually used in pavement construction which are hot-mix hot-laid asphalt mixture, hot-mix cold-laid asphalt mixture and cold-mix cold-laid asphalt mixture. Asphalt is a thermoplastic viscoelastic adhesive which acts as a glue. It softens slowly and change the physical state from solid to liquid when heated. It is characterized by its consistency at certain temperatures. Its relevant properties are its workability, strength, durability, imperviousness and adhesion. Generally, the asphalt properties in term of 9
  10. 10. viscosity is should be in specified fluid in order to allow it easy to conduct during the construction process and process of aggregates coat and wet. To avoid problem such as fracture and crack the viscosity of asphalt must restrain high temperature exposure so that it will not permanently deform through heavy traffic load and low pavement temperature. Factors need to be considered during selection of asphalt penetration grade and types are the climate of the construction area where the temperature of the atmosphere has to take into account and type of construction to be applied. Asphalt can be classified into two; unmodified asphalt and modified asphalt. It is not recommended to use unmodified asphalt because it has a lower quality of resistance and formation of pavement distress can be easily formed when repetitive and heavy load is passed through the pavement. Chemical composition if asphalt also effecting the penetration grade of asphalt and it is stated that the chemical percentage of pure asphalt is 80 to 88% of carbon (C), 0.5 to 10% of oxygen (O2), 9 to 11% of hydrogen (H2) and 0 to 1% of Nitrogen (N2) . 2.3 Hot Mix Asphalt Hot Mix Asphalt (HMA) is a common type of mix that broadly be used all over the world. Basic materials in HMA are a combination of asphalt binder and aggregates which is conducted through a specific design method such as Marshall, Hveem and Superpave. In addition, criteria of selecting the HMA mixtures are based on the different coefficient (Hafeez et. al, 2010). The special procedure of HMA is it must be heated first before proceed to the next step. Besides that in HMA mix design asphalt binder and aggregates are heated together in order to ensure that the asphalt in fluid form and the aggregates is totally dry during coating the aggregates. The newest method in designing HMA is called Superpave Mix design method. 10
  11. 11. 2.3.1 Basic Materials Aggregate Aggregate is one of the main materials in the industry of construction and it contribute a large portion in the construction of an asphalt pavement. American Society Testing Materials (ASTM) had describe aggregates as a granular or coarse material in the composition of mineral such as crushed stone, sand and gravel. It can form into compound materials such as asphalt concrete and Portland cement concrete when it binds together with a medium like water, bitumen, Portland cement and lime. Furthermore, aggregate also used in constructing base and sub-base layers for rigid and flexible pavements. Aggregate is usually based from mineral composition and it can be either natural or undergo mechanical process with the purpose of specific applications. The natural aggregates are usually extracted or taking out from the large formation of the rock by an open excavation. Basically, it is categorized into three geologic classification of rock, which are igneous, metamorphic and sedimentary. Crushed stone, sand and gravel are three types of the aggregates. Crushed stone also known as crushed rocks and mostly crushed stone is excavated from the bedrock. The second type of rock is gravel, it is the result from the erosion and destruction of bedrock and surficial resources. Gravel also can be crushed, since it has a large contribution in constructing asphalt 11
  12. 12. pavement or bases. The formation of sand is either from the erosion of bedrock or mechanically crushed. Asphalt Binder Binder or binder courses describe as a medium which acting as an intermediate paving courses in Hot Mixed Asphalt (HMA) pavement.Modified binder such as polymer modified binder are recommended to improve resistance of asphalt binder against rutting and thermal cracking (Moghaddam, et al, 2011) Nowadays, the grading of binder is base on the Performance Graded (PG) system in Superpave research instead of previously method such as penetration and viscosity test. Asphalt binders can have significant different characteristics within the same grading category. Grading is more accurate and there is less overlap between grades, tests and specifications are intended for asphalt binders to include both modified and unmodified asphalt cements. Asphalt binder tests for Superpave performance grading are as follows: i. Rolling thin film oven; ii. Pressure aging vessel iii. Dynamic shear rheometer; and iv. Bending beam rheometer. 12
  13. 13. Mineral Filler Mineral fillers have traditionally been used in asphalt mixtures to fill the voids between the larger aggregate particles. Generally, the aggregate material passing the No.200 sieve is referred to as filler. In ASTM D242, mineral filler is defined as consisting of finely divided mineral matter, such as rock dust, slag dust, hydrated lime, hydraulic binder, fly ash, loess, or other suitable mineral matter. Other materials, such as carbon black and sulfur, have been used primarily to modify asphalt binder properties, but they do have a role as filler, also. Fillers may be used to: i. Fill voids and, hence, decrease the optimum asphalt content ii. Meet specifications for aggregate gradation iii. Increase stability and strength iv. Improve the bond between asphalt cement and aggregate Mineral fillers have been used to largely fill in the voids between the aggregate particles and to meet specified gradations for HMA. 2.4 Modes of Pavement Distress in Malaysia 2.4.1 Cracking Through the research work done by Public Works Institute Malaysia (IKRAM) has stated that the most common failed faces by asphaltic concrete is cracking as shown in Figure 2.2. The asphaltic concrete road which is constructed for the first time usually exposed to fatigue and top-down cracking while reflection cracks 13
  14. 14. tend to exists on the road that has done resurfacing before on the top cracked surface (Hassan and Sufian, 2008). Figure 2.2 Cracking failures that exist on the asphaltic concrete road 2.4.2 Top-down Cracking In Malaysia, the common grade of asphalt use for asphaltic surface is PEN 80/100 as a binder. The process of making asphaltic concrete acquire heat apply 150 – 170 ˚C during the mixing process between hot aggregates and PEN 80/ 100 asphalt (Hassan and Sufian, 2008). According to JKR, the asphalt tends to strengthen and become hard at the primary stage of the procedure, in storage, during the process of mixing and in service. Top-down cracking is referred as the external (surface) crack downwards propagation which happen when the hardening process go deeper in the surface crack. Figure 2.3 shows the existence of top-down cracking on the road. 14
  15. 15. Top-down cracking exists on the new constructed asphaltic concrete road due to the thickness of the bitumen mix 5-10 micron which is thin. In addition, factors such as improper design method and poor compaction causes higher void content 5 - 8 % during hardening process and lead to cracking existence (Hassan and Sufian, 2008). Besides, ultra violet exposure and moisture content also contribute to the distress of the asphaltic concrete road. Figure 2.3 Top-down Cracking 2.4.3 Reflection Crack The reflected crack shown in Figure 2.4 is a exist crack where had been reflected toward the new layer of asphaltic concrete with 40mm overlay thickness in a relatively short period. The rate of reflection crack depends on the sort of magnitude and cracking of the surface road bonded to overlay, and the volume of vehicle passes along the road after the construction (Hassan and Sufian, 2008). Based on the research study, the 40 mm thickness overlays of asphaltic concrete are unsuitable for rehabilitation of the asphaltic concrete road. 15
  16. 16. Figure 2.4 Reflection Crack 2.5 Rutting Rutting is dangerous surface distress for road user where it causes accumulation of surface water; hence it increases the possibility of hydroplaning and skidding (Hassan and Sufian, 2008). Water that accumulates on the pavement distress during rain will increase the water infiltration rate into the pavement layer and the existence of deformation will cause the vehicle to lost control especially during lane changes which both of these factors is dangerous for road users. Rutting also defined as longitudinal cracking in road pavement where the presence of rutting will bring uncomfortable in driving comfort for road user and affects safety and health. Rehabilitation is one of the ways to overcome the permanent deformation problem and it must continuously apply on the road after the road reach its service life. Figure 2.5 shows pictures of permanent deformation or rutting. 16
  17. 17. Figure 2.5 Permanent deformations or rutting 2.5.1 Factors Affecting Rutting Permanent deformation or rutting is categorized as a longitudinal depression which is formed along the wheel paths. Figure 2.6 shows the rutting that happens on the road. It happened due to the accumulation of minor deformations that caused by high temperature and repetitive heavy loads. Factors that contribute to deformations may be caused by too much continuous stress by tire being applied to the subgrade or by an unstable asphalt mixture where shear strength of the mixture is too low. In addition, rutting also considered as a structural problem. It is generally the result happened because of wrong calculation during the pavement design or of properties in the subgrade that has been weakened due to the moisture intrusion. In the other research study, the presence of rutting is due to the accumulated deformation happened in the asphalt surface layers rather than in the subgrade layer. Incorrect procedure in preparing the asphalt mixture also contributes to the permanent deformation. It is explained that when a layer of 17
  18. 18. asphalt pavement has inadequate shear strength it will cause shear deformation to occur every time a heavy load such as truck passes through the pavement. A rut will then appear after the asphalt pavement achieves the maximum load where it can resist. This type of road distress can reduce the serviceability of the asphalt pavement and the road user was exposed to a safety hazard. Figure 2.6 Rutting or permanent deformation on the pavement 2.5.2 Laboratory Test Related to Rutting Hamburg Wheel Tracker The Hamburg Wheel Tracker (HWT) was developed and established by Helmut Wind in Hamburg Germany. The advantage of HWT is it can conduct the test of HMA beam and cylindrical sample in water. 18
  19. 19. The vertical load subjecting to the sample is 705 N and applied on a solid rubber wheel. The diameter of loaded wheel is 194 mm and a width of 47 mm. The sample is compacted to an air void content of 7±1 percent, are typically subjected to a maximum of 20,000 loading repetitive passes at a rate of about 340 mm/s (Choubane et al, 1998). Figure 2.7 below shows the Hamburg Wheel Tracker device. Figure 2.7 Hamburg Wheel Tracking Device Couch Wheel Tracker The Couch Wheel Tracker (CWT) is modified version of Hamburg Wheel Tracker. However in CWT tests only HMA beam samples being submerged in the water (Choubane et al, 1998). Test samples are subjected with a 705 N vertical load which is applied through a solid rubber wheel. The rutting performance is determined by measuring the 19
  20. 20. height position of the loading wheel at the center of the travel span after the process of continuous loading finish The measurements are constantly recorded on a provided chart during the testing. Georgia Loaded Wheel Tester The development of Georgia Loaded Wheel Tester (GLWT) is from the Georgia Institute of Technology at the Georgia Department of Transportation in the mid-1980's (Choubane et al, 1998). It was designed and planned with the aim of developing a simplified method to enhancement the method of Marshall in evaluate the rutting characteristics of the asphalt mixes which is used in Georgia. Figure 2.8 shows a schematic drawing of one version of the Georgia Loaded Wheel Tester Figure 2.8 Schematic drawing of one version of the Georgia Loaded Wheel Tester 20
  21. 21. The advantages using GLWT is it capable of testing samples of the confined asphalt concrete beam. It tests the samples of asphalt concrete beam by using a stiff pressurized hose which is mounted at the top of the specimens. The purpose of the hose was same as a tire which is to transfer the load that is received from the loaded wheel directly to the beam (Choubane et al, 1998). One complete loading cycle will involves back and forth pass through of the loaded wheel. The rut depth is measured and evaluated using a dial gauge that connected to the device and used a reference template at set cycle intervals. The result then will be compared to a pass or fail criteria. LCPC (French) Wheel Tracker The Laboratoire Central des Ponts et Chaussées (LCPC) wheel tracker which is also known as Franch Wheel Tracker (FWT) majorly used in France for more than a decade to determine rutting in HMA pavements (Choubane et al, 1998). The function of LCPC is to carry out beam sample test in the air. The samples will be subjected to 5,000 N loads through a pneumatic tire which has been inflated to 600 kPa. The total deformation depth of the slab is determined and recorded as the average of a series of 15 measurements where three measurements is taken randomly across the sample width at each of five points along the sample length. The passing criterion for the sample is the average deformation depth must less than 10 percent from the original sample thickness. Figure 2.9 shows a France Wheel Tracker device 21
  22. 22. Figure 2.9 France Wheel Tracker device 2.6 Polymer Modified Asphalt 2.6.1 The Purpose of Asphalt Modification Polymer modified Asphalt is asphalt which has undergone modification by addition of modified binder such as latex and polyacrylates into the mix. The advantages of using polymer modified asphalt are it has better performance in durability, resistance and strength. Besides the physical properties of the asphalt when added modified binder does not change the chemical nature of the asphalt. Research done also stated that modified asphalt binders make the texture of the mixture become soft and smooth at lower temperature which resulting in reduction of thermal cracking. In addition to fatigue resistance of the asphalt 22
  23. 23. mixes is being improved with the polymer modified asphalt usage and since the fatigue resistance of asphalt improves the pavement can resist more traffic load and extreme climate temperature changes. Figure 2.10 shows the stress diagram of unmodified asphalt and modified asphalt. Shear stress ( ) Asphalt binders Modified Asphalt Large ‘c’ Unmodified Asphalt Small ‘c’ Normal stress ( ) Figure 2.10 Stress Diagram of Modified and Unmodified Binder 2.6.2 Type of Asphalt Modifiers Asphalt modifiers can be categorized in several ways which depends on the mechanism where the modifier alters the asphalt properties, on the composition and physical nature of the modifier itself, or on the properties of the target asphalt that needs improvement or enhancement. A list of the types of modifiers commonly used in the asphalt industry is given in Table 2.1. The modifiers are classified based on the nature of the modifier and the generic types of asphalt modifiers (National Cooperative Highway Research Program, 2001). The target distress shown in the table corresponds to the main distress the additive is expected, or claimed, to reduce. The information is based on an interpretation of the published information for brands of modifiers that belong to the modifier classes shown. The information in Table 2.1 indicates that asphalt modifiers vary in many respects. They can be particulate matter or additives that will disperse 23
  24. 24. completely or dissolve in the asphalt. They range from organic to inorganic materials, some of which react with the asphalt, while others are added as inert fillers. The modifiers generically vary in their specific gravity as well as other physical characteristics. They are expected to react differently to environmental conditions such as oxidation and moisture effects. Table 2.1 Generic types of asphalt modifiers currently used for paving applications Effects on Distress Modifier type Fillers Extenders Polymers-Elastomers Polymers-Plastomers Crumb rubber Oxidants Hydrocarbons Antistrips Class PD Carbon black Mineral: Hydarted lime Fly ash Portland cement Baghouse fines Sulphur Wood lignin Styrene butadiene di-block SB Styrene butadiene triblock/ radial block (SBS) Styrene isoprene (SIS) Styrene ethylbutylene (SEBS) Styrene butadiene rubber latex SBR Polychloroprene latex Natural rubber Acrylorite butadiene styrene (ABS) Ethylene vinyl acctate (EVA) Ethylene propylene diene monomer (EDPM) Ethylene acrylate (EA) Polyisobutylene Polyethylene (low density and high density) Polypropylene Different sizes, treatment and process Manganese compunds Aromatics Napthenics Paraffinics/ wax Vacuum gas oil Asphaltenes: ROSE process resins SDA asphalteners Shale oil Tall oil Polyamides Hydrated lime Organo-metallics x x x x x x 24 x x x x x x x x x x x x x x x FC LTC MD AG x x x x x x x x x x x x x x x x x x x x x x x x x
  25. 25. Fiber Polyropylene x x x Polyster x x Fiberglass Steel x x x Reinforcement x x x Antioxidants Carbon black x Calcium Salts Hydarted lime x Phenols Amines x PD: Permament Deformation MD: Moisture Damage FT: Fatigue Cracking OA: Oxidative Aging LTC: Low Temperautre Cracking ( National Cooperative Highway Research Program, 2001) 2.6.3 The Ideal Modified Binder The most important property of asphalt when it is used in pavement construction is changing in its stiffness with temperature. The ideal binder is necessary to be hard and stiff enough at changes temperatures so that it can resist against deformation and it also must be flexible enough at a lower temperature so as to inhibit cracking. An ideal binder must exhibit the following properties: i. Adequate rigidity and inelasticity in order to minimize the rutting on a hot day. In addition, it must have a progressive effect on the fatigue effect of the bituminous hot mixture. ii. Flexible enough even during the cold temperature to avoid cracks such as thermal cracks. iii. The binder must have light characteristics to allow the pumping process of liquid binder smooth and fast and the binder is ideal when the viscosity decreased to facilitate mixing and compaction of the hot bituminous mixtures. 25 x x x x x
  26. 26. 2.7 Superior Performing Asphalt Pavement Superior Performing Asphalt Pavement, better known as Superpave is a one of the outcomes of the Strategic Highway Research Program (SHRP). SHRP target of constructing the pavement requires less maintenance, provide a smooth ride, and is a good value for tax payer’s money. The research was done in 1993, providing several new elements in the system such as asphalt binder being graded by performance grade (PG), consensus properties of aggregate, new mix design procedure, and mixture analysis (National Cooperative Highway Research Program, 2001). Currently, the Superpave mix design system has become the choice for the majority of transportation companies for HMA mix design. The key equipment in Superpave method is the Superpave Gyratory Compactor (SGC). 2.7.1 Background of Superpave Through the development of asphalt mix design, there are now several different types of laboratory compaction devices have been established in order to produce specimens for volumetric and/or physical characterization (National Cooperative Highway Research Program, 2001). Bruce Marshall and Francis Hveem are the one whose developed mix design methods and by the late 1950s, these methods were largely used in pavement construction. The Marshall mix design method adopted the impact type of compaction while the Hveem mix design method uses tampering blow and kneading compactor (Hafeez et. al, 2010). The gyratory concept was credited to Phillipi, Raines, and Love of the Texas Highway Department, which was a manual unit of gyratory pressing. In the 26
  27. 27. 1950’s, the concept was copied by John L. Macrae, with the U.S. Corps of Engineers, developing a new device called gyratory kneading compactor, which was named as the Gyratory Testing Machine (GTM) in 1993. Another important contribution to the improvement of gyratory concept is through the Laboratory Central des Ponts et Chausées (LCPC) in France, where it has a fixed external, external mold wall angle of one degree with a compaction pressure to 600kPa. 2.8 Superpave Gyratory Compacter The equipment used in the Superpave mix design method and which is the key piece is a gyratory compactor as shown in Figure 2.11 which is the principle goals was to develop a laboratory compaction method, which can consistently produce specimens representative of in-service pavements. The Superpave Gyratory Compactor (SGC) compact HMA sample to densities achieved under traffic loading conditions. Its ability to estimate specimen density at any point during the compaction process is its key feature. Figure 2.11 shows Superpave Gyratory compactor. Figure 2.11 Superpave Gyratory Compactor 27
  28. 28. 2.9 Asphalt Pavement Analyzer The Asphalt Pavement Analyzer (APA) is the new version of the wheel tracker device which is adapted from the Georgia Loaded Wheel Tester (Choubane et al, 1998). The APA has implemented additional features which are installation of water storage tank and is having the ability of testing both gyratory and beam samples. Generally, APA is a wheel tracking device that applies a vertical load to a steel wheel (A Sholar and Page, 1999) Three beams or six gyratory of the samples can be performed and tested simultaneously. The loaded wheels are applied to sample test of three pneumatic cylinders, where each of it is equipped with standard aluminium wheels. The load from each of the moving wheel is shifted and transferred to a test sample through a pressurized rubber hose mounted along the top of the sample. The advantage of using APA is it can evaluate not only the rutting performance of an HMA mixture, but it also can determine the fatigue cracking and moisture susceptibility under certain condition of the service. Figure 2.12 and Figure 2.13 shows an Asphalt Pavement Analyzer device and schematic drawing of the device respectively. Figure 2.12 Asphalt Pavement Analyzer Device 28
  29. 29. Figure 2.13 Schematic Drawing of the Asphalt Pavement Analyzer 29
  30. 30. 2.10 Gap of Research Study Based on the studied journals, there are more focusing on evaluation of rutting performance using different types of machineries used and gradation of aggregates. The journal that using different type of machineries to evaluate the rutting performance such as Simple Performance Test (SPT), Uniaxial Repeated Creep and Wheel Tracker Tests were focused on determining the correlation of rutting performance using those machines. Besides that, a journal that used different types of aggregate gradation is to identify how the size of aggregates can affect the performance of rutting. The study of aggregate physical properties such as elongation and flakiness on rutting impact also was the main focus of this journal. On my research work, I’m focusing into the performance of polymer modified binder against permanent deformation by comparing them with unmodified binder. There were two types of polymer binder use of this work which are latex and polayacrylates. Furthermore these two polymer modified binders were also comparable to each other to select the best used of polymer against rutting. The criteria needed to be compared are the rut depth which this was obtained through an Asphalt Pavement Analyzer. The result was shown in term of graph and bar chart for better understanding of their performance on the pavement. The characteristics of the polymer were analyzed and discussed to understand why the performance of each polymer modified binder was differ from others polymer modified binder. Table 2.2 shows a gap of research study. 30
  31. 31. Table 2.2 Gap of research study Year Title Authors Purpose Finding 2011 Rutting Evaluation of Dense Graded Hot Mix Asphalt Mixture Juraidah Ahmad, Mohd Yusof Abdul Rahman, Mohd Rosli Hainin To investigate rutting potential using SPT dynamic modulus test and how well this test correlates with Wessex wheel tracking test to evaluate the rutting potential of local HMA The change in HMA mixture behaviour using SPT dynamic modulus test was effective to determine the rutting potential of the HMA mix with varying temperatures and loading frequencies. 2010 Evaluation of Rutting in HMA Mixtures Using Uniaxial Repeated Creep & Wheel Tracker Tests Imran Hafeez, Mumtaz Ahmed Kamal and Muhammad Waseem Mirza To predict the permanent deformation of HMA mixtures at elevated temperature with uniaxial repeated creep and wheel tracker test) The specimen from the wheel tracker specimen test is observed to produce a less rate of increase in rut depth compared to unconfined uniaxial repeated creep test. 2011 A review of Taher Baghaee To review previous fatigue and Moghaddam, studies carried on rutting Mohamed Rehan fatigue and rutting performance of Karim and Mahrez properties of asphalt asphalt mixes Abdelaziz concrete (AC) and the effects of additives to slow the deterioration of asphalt mixture. It was determined that mixtures with larger aggregate gradation and higher asphalt content result in lower the fatigue life and slower the presence of rutting 2012 Performance of Ashok Pareek, Polymer Modified Trilok Gupta and Bitumen For Ravi K Sharma Flexible Bitumen Shows that the performance of polymer modified bitumen is better than conventional bitumen PEN 60/70 31 To investigate the performance using polymer modified bitumen and unmodified bitumen in term of rutting performance.
  32. 32. CHAPTER 3 RESEARCH METHODOLOGY 3.1 Introduction In this chapter, the detail of progress work and the procedure of how this study was conducted is explained. Before proceeding to the procedure of laboratory test, information searching were collected to explore the background of the study. The aim of this study is to evaluate the rutting performance of polymer modified binder in Hot Mix Asphalt mix design. Thus, method and process to be used in determining the rutting performance is listed in detail to achieve the aim of the study. The test is conducted according to the required specifications, laboratory test procedure and information on the materials used and also based on the sample properties. The method used in the sample preparation is the Superpave Mix Design method. The sample mix involves for rutting performance basically have two types of polymer modified binder which is latex and polyacrylate. The result of the rutting performance of latex and polyacrylate was compared and analyzed. After all process are fulfilled, the evaluation of routing performance on the final compiled HMA sample was conducted through Asphalt Pavement Alyzer machine. Figure 3.1 shows an illustration design of research studies. Figure 3.2 shows the Overall Evaluation of Rutting Performance of Polymer Modified Binder in HMA Mix Design. 32
  33. 33. Stage 1 Stage 2 Superpave Mix Design Method Desk Study Stage 3 Rutting Performance Evaluation on Polymer Modifed Binder in HMA ; -the specimen was 7±0.5% air void Materials Collection for the Project 1. Blending of Specimen: -Asphalt Pavement Analyzer -Unmodified Binder-Control -Modified Binder- Latex at 160°C and 1270 rpm -Polyacrylate 140°C and 1650 rpm 1. Asphalt binder PEN 80/100 2. Aggregate of 19 mm Control nom. max size 3. Binderlatex & polyacrlates Mixing of HMA mixture -automatic mixer Compacting and Testing Samples with Superpave Gyrator Compactor Figure 3.1 Design of Research Study 33 Result and Data Analysis Conclusion
  34. 34. Superpave Method Material Collection Asphalt binder PEN 80/100 Aggregate of 19 mm nom. max size Mixture Design Compacting and testing with Superpave Gyrator Compactor Mathematical Calculation Compiling and Establishing Final Blend Bituminous Paving Mixture Evaluation Rutting on Compiled final Bituminous Paving Mixture by Asphalt Pavement Analyzer Conclusion Figure 3.2 Overall Evaluation of Rutting Performance of Polymer Modified Binder in HMA Mix Design 34
  35. 35. 3.2 Materials Selection 3.2.1 Asphalt Binder The binder used in this research study is grade PEN 80/100 and based on the current study, it also stated that asphalt binder is obtained from Port Klang. Type of asphalt cement binders is classified based on their depth of penetration at various temperatures. In Superpave mix design the selection of asphalt binder is totally depends on climate which changes of temperature must be recorded and traffic-loading conditions of the selected project location. Softening Point Softening point which also known as ring and ball test is a method to determine the softening point of asphalt binders, in the range of temperature of 30 °C to 150 °C. Two horizontal discs of asphalt binder, cast in shouldered brass rings, are heated at a controlled rate in a liquid bath while each supports a steel ball. The softening point is reported as the mean of the temperatures at which the two discs soften enough to allow each ball, enveloped in a asphalt binder which were control, latex and polyacrylates to fall a distance of (25,0 ± 0,4) mm. Ductility Test The ductility of a asphalt material is measured by the distance in cm to which it will elongate before breaking when a standard briquette specimen of the material is pulled apart at a specified speed and a specified 35
  36. 36. temperature. Ductility is the property of bitumen that permits it to undergo great deformation or elongation. In addition, ductility is defined as the distance in cm, to which a standard sample of the material will be elongated without breaking. The procedure of the ductility start by the asphalt (control, latex and polyacrylate) were heated and poured in the mould assembly placed on a plate. These samples with moulds are cooled in the air and then in water bath at 27 °C temperature. The excess asphalt was cut and the surface was leveled using a hot knife. Then the mould with assembly containing sample is kept in a water bath of the ductility machine for about 90 minutes. The sides of the molds are removed, the clips are hooked to the machine and the machine was operated. The distance up to the point of breaking of thread was the ductility value which is reported in cm. The ductility value gets affected by factors such as pouring temperature, test temperature and rate of pulling. The ductility value of the control, latex and polyacrylate were then compared to determine the binder properties between modified binder and unmodified binder. Penetration Test In this test, the consistency of asphalt was examined by determining the distance in tenths of a millimeter that a standard needle vertically penetrates into the bitumen specimen under known conditions of loading, time and temperature. This is the most common methods of measuring the consistency of a asphalt material at a given temperature. The modified asphalt (latex and polyacrylate) and unmodified asphalt (control) were 36
  37. 37. examined together to determine the penetration value between the three specimens. 3.2.2 Aggregates Aggregates used in the asphalt mixture include various particle sizes which are coarse and fine aggregates. Figure 3.3 and Figure 3.4 show the aggregate was obtained from the Blacktop Quarry at Rawang and filled in the sack. The selection of aggregates is necessary because it affects the performance of HMA mixes. The preparation of aggregates can be classified into two properties; consensus properties and source properties as shown in Table 3.1 Figure 3.3 Sample is taken from Blacktop Quarry, Rawang 37
  38. 38. Figure 3.4 Sample Filled in Sack Table 3.1 Properties of aggregates Consensus Properties Source properties a) Coarse aggregate angularity a) Specify gravity b) Fine aggregate angularity b) Soundness c) Flat and elongated criteria c) Toughness d) Gradation Flat and Elongation Flat and elongation particles defined as the percentage by mass of coarse and granular aggregates that have a maximum to minimum measurement ratio greater than five. This classification is used in the Superpave requirement in purpose to identify aggregates that have a tendency to obstruct compaction. Flat and elongated particles have a tendency to lock up between particles more readily during compaction process which makes the compaction more difficult. 38
  39. 39. Toughness Abrasion test is carried out to check the toughness property of aggregates and to select whether the aggregates are suitable for different pavement construction works. The Los Angeles abrasion test is a suggested one for carrying out the toughness property. The standard of Los Angeles abrasion test is to determine the percentage wear due to relative rubbing and crushing action between the aggregate and steel balls used as a medium to abrasive charge. The Los Angeles machine comprises of round drum of internal diameter of 700 mm and length 520 mm mounted on a horizontal axis to make it rotated. The steel spherical balls of 48 mm diameters and weight 340-445 g were placed inside the machine together with the aggregates. The number of the abrasion varies depending on the grading of the sample. The quantity of aggregates to be used usually ranges from 5-10 kg. The speed of the cylinder to rotate was 30-33 RPM for a total of 500 -1000 revolutions subject to the gradation of aggregates. After the desired revolution was achieved, the material is sieved and passed fraction is said as the percentage total weight of the sample. This value is called a Los Angeles abrasion value. Figure 3.5 shows the Los Angeles Abrasion Machine. 39
  40. 40. Figure 3.5 LA Abrasion Machine 3.3 Superpave Hot Mix Asphalt Design The Superpave procedure was used to design the HMA mix used for the performance test evaluation for this study. The design procedure is based on the percentage of asphalt for the aggregate blends using the volumetric properties of the mix as the primary criteria. These include a 4% air voids and a set of minimum values for the voids in HMA sample, however HMA sample at 7% air voids were prepared for rutting performance test. 40
  41. 41. 3.3.1 Aggregates Preparation The aggregates were oven-dried in oven in large quantity for at least 12 hours at a temperature of 100° C as shown in Figure 3.6 and Figure 3.7, then the aggregates are then left to cool at room temperature. The aggregates were then sieved and separated into their individual particle sizes as shown in the table below. Table 3.2 shows the aggregate gradation for Superpave mixes. Figure 3.6 Loose Aggregates Before Mixing Figure 3.7 Oven 41
  42. 42. Table 3.2 Aggregates Gradation for Superpave Mixes Sieve size Blending Passing % Retained 25 100 0.0 19 96 4.0 12.5 81.0 15.0 9.5 75.0 6.0 4.75 55.0 20.0 2.36 43.0 12.0 1.18 32.0 11.0 0.6 23.0 9.0 0.3 13.0 10.0 0.15 8.0 5.0 0.0075 4.0 4.0 (mm) Pan 4.0 Total 100.0 Dust Loss After Wet Sieving 3.3.2 Polymer Modified Binder The device used to mix the binder with polymer is a hot plate mixer as shown in Figure 3.8. For the research study, the selected mix method to be used is a wet method is used to mix with asphalt grade PEN 80/100 where the polymer modified binder were weight using an electronic scale as shown in Figure 3.9 and Figure 3.10 respectively. The binder parameter in the research study is shown in Table 3.3 which is obtained through previous project done by Atikah (2013). 42
  43. 43. Figure 3.8 Hot Plate Mixer for Modified Asphalt Figure 3.9 Modified Asphalt Preparation (Latex and Polyacrylate) 43
  44. 44. Figure 3.10 Electronic Weighing Scale Table 3.3 Binder Parameter of Polymer Modified Binder Mixes Optimum Blending Blending Polymer Content Temperature, °C Velocity Polyacrylate 6% 140 1650 Latex 8% 160 1270 Types of binder 44
  45. 45. 3.3.3 Preparation Process of Polymer Modified Binder The preparation of polymer modified binder is shown in Figure 3.11 1. Measure • The 500 g conventional binder is measure • Heat the over at 120°C and put the binder inside oven 2. Heat • Calculate the weight of polymer using following equation; • 𝑃 100 × 𝐴 = 500𝑔 … 1 • 𝑊𝑒𝑖𝑔𝑕𝑡 𝑜𝑓 𝑝𝑜𝑙𝑦𝑚𝑒𝑟 𝑚𝑜𝑑𝑖𝑓𝑖𝑒𝑑 𝑏𝑖𝑛𝑑𝑒𝑟 = 𝐴 − 500𝑔 … (2) 3. Calculate • Which: • P = 100% of mixture minus by percentage of polymer modified binder • A = weight of conventional binder + polymer modified binder • % of polymer modified binder is based on the previous research work 4. Mix • Mix the polymer modified binder using laboratory mixer based on the mixing parameter as shown in Table 2. Figure 3.11 Blending Procedure of Polymer Modified Binder 45
  46. 46. After finishing the mix process, the step was repeated with different percentage of polymer modified binder which is 6% of Polyacrylate and 8%. Figure 3.12 shows propeller mixer and the blade was used in mixing the binder and duration of mixing was one hour and heated using an electric hot plate with temperature control of laser temperature. Figure 3.12 Mixing Process for Modified Asphalt 3.3.4 HMA Mixing Process The aggregates and the modified asphalt were initially heated in the oven at a temperature of 160ºC for about 2 hours as shown in Figure 3.13. The mixer also switched on to heat up the mixer bucket. After 2 hours, the aggregates and the 46
  47. 47. modified asphalt were weighed according to their optimum binder content percentage. Figure 3.14 shows the mixing process which took approximately 5 to 10 minutes to allow aggregates to be well coated with binder. Three samples of aggregate weighing 2200g, 2300g and 2400g for each control sample with modified asphalt were mixed and compacted in the first place in the Superpave Gyratory Compactor. Another three samples of aggregates of weighing 1500g were mixed to determine to maximum specific gravity (Gmm).Table 3.4 shows the optimum binder content and mix design properties obtained from previous research (Atikah, 2013). Figure 3.13 Heating of Aggregates and Binder 47
  48. 48. Figure 3.14 Heating of Aggregates and Binder Table 3.4 Mix Design Properties Mix property DESIGN MIXTURE PROPERTIES 19mm NMAS mixture types control polyacrylate latex Criteria Air voids% VMA % 4.0 15.8 4.0 16.0 4.0 15.9 4 14 min VFA % Dust proportion% %Gmm@ Nini=8 74.7 0.8 75.0 0.8 74.8 0.9 65-75 0.6-1.2 86.5 5.5 87.6 5.4 86.2 less than 89 5.3 (Source: Atikah,2013) Asphalt Binder content 48
  49. 49. 3.3.5 Short Term Oven Aging (STOA) All HMA mixes were short term aged in the oven for 2 hours at temperature of 140ºC to induce a short term oven aging (STOA). However, loose mix to determine the maximum specific gravity was left at room temperature to cool as shown in Figure 3.15. Figure 3.15 Loose HMA mixture after mixed process 3.3.6 Compaction The HMA samples are compacted in the Superpave Gyrator Compactor Device (Figure 3.17) after STOA for two hours. Figure 3.16 shows the 150mm diameter mould used to compact HMA sample. After compaction the sample allowed to cool for 24 hours in room. The Bulk Specific Gravity (Gmb) was then determined using buoyancy apparatus for each of the compacted HMA samples. From both Gmm and the Gmb data, the percentage air voids for each control, latex and 49
  50. 50. polyacrylates samples are calculated. Figure 3.18 shows that the immersed samples in water to determine the Gmb. A back-calculation formula was used to identify the percentage of weight of sample needed for net performance test based on 7% air void. The final HMA mixture aggregate is then mixed and compacted and to the corresponding to Ndes gyrations. Figure 3.16 Compaction Mould 50
  51. 51. Figure 3.17 Superpave Gyratory Compactor Figure 3.18 Sample immersed in water 51
  52. 52. 3.4 Compacting and Testing HMA mixture of trial blend with Superpave Gyrator Compactor Device The Servopac Gyratory Compactor (SGC) is a device used to compact the HMA mixture in mix design. It is capable to compact the HMA samples to a density which is required in the field pavement. Basically, there are three main parameters that control the compaction of the Superpave mix design which are vertical pressure, number of gyrations and angle of gyration. For vertical stress it was set at 600-kPa, and the angle of gyration was set at 1.25º, and lastly the number of gyrations, which is not being set up because it may be various depending on condition of HMA samples. Three (3) samples for each polymer modified binder and control were compacted at 1.25º in the Servopac Gyratory Compactor to obtain the air void as shown in Figure 3.19. Figure 3.19 Compacted HMA Sample The procedure for sample preparation and testing in the Servopac started with weighing the aggregates of 2200g, 2300g and 2400g respectively according to the required job mix formula shown in Figure 3.20. The aggregate and asphalt binder for control, latex and polyacrylates are preheated separately at 140ºC for about two hours then both are mixed 52
  53. 53. until the aggregates are fully coated with binder. The amount of binder used is based on optimum binder content obtained from previous research conducted by Atikah, 2013. The HMA mixture was then placed in the oven for two hours for short-term oven aging (STOA). Prior to compaction in 150mm mold diameter and 65mm height. The three samples were then compacted at 1.25º angle of the gyration. Each specimen was left to cool at room temperature (approximately 25ºC) for at least 24 hours after the compaction process. The Bulk Specific Gravity of the specimen is then determined using buoyancy balance apparatus. The maximum specific gravity of the mixture was determined using Corelox machine and buoyancy balance apparatus. From both Gmm and Gmb result obtained, the air void of the HMA samples was determined using the following equation to achieve 7± 0.5% air void before proceeding with rutting performance test. 𝐴𝑖𝑟 𝑜𝑖𝑑 = 100 × (1 − Where, A = bulk specific gravity (gmb) B = theoretical maximum specific gravity (gmm) 53 𝐴 )
  54. 54. a) Aggregates- put into oven with150°C - 160°C for more than 4 hours b) Binder- put into oven with 150°C at one – two hours Heat both binder and aggregates The cynlinder mould is place into oven at 160°C for one – two hours Heat cyclinder mould The binder and aggregates is mix together at 160°C to ensured the aggregates fully coated with binder Mix aggregates and binder a) Place the mixes of aggregates and binder into oven for two hours (ageing process) at 160°C b) Compact the HMA mixture using SGC c) Determine the specify gravity with corelox Gmb a) Store at room temperature for 24 hours b) Proceed with Corelok to get specifc gravity Gmm Figure 3.20 Preparation Sample of HMA mixes 54
  55. 55. 3.5 Evaluation of Rutting Performance on HMA Mixture Rutting or permanent deformation of the laboratory designed mixtures was evaluated using the Asphalt Pavement Analyzer (APA) as shown in Figure 3.21. This wheel tracking machine operates under a pair of wheels apply moving loads above two rubber hose to the specimen in order to simulate the rutting performance in an accelerated manner. The depth of depression or rut formed on the sample is measured and analyzed using computer software. The test measures the depth and number of wheel passes to failure. Each moving steel wheel of APA machine was 8 inches (203.6 mm) in diameter and 1.85 inches (47 mm) wide. The aggregates and asphalt mixtures were heated to 150°C, blended together then returned to the oven for 2 hours before compaction. The HMA samples after the compaction, is placed in the laboratory with room temperature at least for 24 hours to allow the aggregates to uniformlly bind with the asphalt mixture . All samples were compacted to reach target air voids of 7 percent to simulate the typical initial density in the field. Figure 3.22 shows the set up the specimen. 55
  56. 56. Figure 3.21 Asphalt Pavement Analyzer Machine Figure 3.22 Sample is placed in APA machine For APA testing, eight cylindrical samples of which four are control samples, two latex and two poly were compacted using Superpave Gyratory Compactor. The desired density 56
  57. 57. of HMA mixture was obtained by adjusting the weight of the mixture. Prior to real testing, the sample was first conditioned in the APA chamber machine for two hours. Testing on the APA machine was performed at 60°C with the sample sides in full confinement and the pressure of rubber hose and wheel load was respectively set up at 690 kPa (100psi). The analysis of rut measurements was collected at 0, 25, 4000 and 8000 loading cycles. Figure 3.23 and Figure 3.24 shows the condition of the specimens after the performance test. Figure 3.23 Specimen condition after the test 57
  58. 58. Figure 3.24 Rut depth on the HMA sample 3.6 Data Analysis In this study, the performance of pavement by using a polymer modified binder was analyzed. The performance graph and bar chart are used to analyze the performance of each polymer modified binder in terms of rut depth. The APA rut depth measurements as collected during the performance test are summarized in result and discussion section. The result was analyzed the effectiveness of rut potential of asphalt mixes between polymer modified binder and control mixes. 58
  59. 59. CHAPTER 4 RESULT AND DISCUSSION 4.1 Introduction This chapter discusses the results of laboratory HMA mix rut performances NMAS 19.0mm Superpave mixtures. The cylindrical samples were examined with respect to rutting at three different mixtures which are control, latex and polyacrylate. Performances of laboratory mixes were evaluated in terms of rutting by using the Asphalt Pavement Analyzer machine. From this study, it determines that the design of hot mix asphalt mixture using Superpave mix design suitable to be developed based on Malaysian standard. The major steps in testing and analyzing process lead to the outcome of this study. 4.2 Aggregates Properties Test Three types of aggregates which are sand, screening and quarry dust were used in order to developed aggregates blends meeting the requirements of gradation. The standard for the consensus aggregate test is based on the traffic level and position the pavement layer. The importance of the source aggregate property test is to estimate the specific stockpile fraction. The toughness test by LA Abrasion is used to evaluate the percentage change in coarse particle size of aggregates while aggregate soundness test capabilities to assess both coarse and fine aggregates. Table 4.1 and Table 4.2 show results of consensus properties and source properties respectively. 59
  60. 60. Based on the achieved result, the value for both consensus and sound properties is satisfied and fulfilled the standard of mix design. Thus, the aggregates sample from Blacktop Quarry,Rawang can be used in Superpave mix design. Table 4.1 Consensus Aggregates Properties Result Blacktop Quarry, Rawang Consensus Properties References Test Method Result Criteria ASTM D 4791 Flat or Elongation in Flakiness Index: Coarse Aggregates 3.10% <10 % Elongation Index: 16.6% <20% Table 4.2 Source Aggregates Properties Result Blacktop Quarry, Rawang Source Properties References Result AASTHO T 96 Los Angeles Abrasion Percentage of loss: Test 4.3 Test Method Criteria 25.35 <45 % Binder Properties Test Three test have been carried out to test the physical properties of asphalt which are penetration test, softening point ad ductility test as shown in Table 4.3. Table 4.3 Physical Properties of Aphalt Conventional Bitumen Polyacrylate (Modified) Latex (Modified) Penetration value (mm) 85 60 55 Softening Point (ºC) 58 65 70 Ductility Test (cm) 95 125 150 60
  61. 61. Penetration test is a commonly adopted test on bitumen to grade the material in terms of its hardness and it was used to measure the consistency of bitumen, so that the bitumen can be classified into standard grades. In this work the penetration grade used were 80/100 where it means that the penetration value lies between 80 and 100. The penetration value of bitumen helps to assess its strength between modified and unmodified asphalt. The greater value of penetration indicates softer consistency. Generally higher penetration bitumen are preferred for use in cold climate and smaller penetration bitumen are used in a hot climate area. In our climate we preferred lower penetration grade to avoid softening due to the high temperature of the climate, and based on the result it was said that modified asphalt has lower penetration value compared to unmodified asphalt so the use of polymer modified binder in this work can be proceed to the performance test. Temperature is noted when the softened bitumen touches the metal plate which is at a specified distance below. Based on the table 4.3, the lowest temperature of softening point was 58 ºC using control sample. However the temperature of softening point of where the ball fall was increased using latex and polyacrylates. The difference of softening point may influenced by the properties of the asphalt binder. Asphalt that consists latex has the highest softening point, where high temperature need to soften the bitumen and same thing goes to polyacrylates specimen. Generally, the higher softening point indicates lower temperature susceptibility and was preferred in hot climates thus modified asphalt was showing positive results in strengthening the HMA mixture for this work study. 61
  62. 62. Ductility is the property of bitumen that allows it to undergo elongation. In this work asphalt binder are used in the HMA mixtures. It is important that bituminous material forms ductile thin film around the aggregates that serves as a binder. From the table, the modified binder has a longer ductility value which is 125 m and 150 cm for polyacrylates and latex respectively compared to control. The binder material not of sufficient ductility renders pervious pavement surface and leads to development of cracks. Therefore, the longer the elongation of the bitumen can resist mean the better it can serve as a binder. 4.4 Evaluation of Rutting Performance using Asphalt Pavement Analyzer The rut depth from APA at a number of wheel cycles was measured for control, latex and polyacrylate sample to follow the rate of rutting for these samples. These are shown in Figure 4.1 and Figure 4.2. It is observed that for all the samples, the APA rutting accumulated at the end of 8000 cycles and it is measured within the first 25strokes whiles about two-thirds of the rutting are mobilized at 4000 cycles. This may indicate that in practice a greater portion cycles such as 4000 cycles of the entire rutting accumulated within the pavement over its service period is likely to happen very quickly after the first few months of traffic loading. The higher the depth of rut indicates that the asphalt used in HMA mixture has lower strength to against rutting in terms of the bonding with aggregates. This rut depth will be in the form of densification rutting and it will not be dangerous enough to cause hazard, but may be risky for motorist if it is deep enough and uneven across the pavement surface. A very high rutting measured next the first few passes of cycles may seem to have problem such as unstable mixture especially when the rutting does not begin to stabilize during this level. This behavior of rutting was observed in the APA rutting for 62
  63. 63. the control sample, which explain that it has unstable mixtures. However, for the purposes of comparison of the performance control sample and modified asphalt is to determine the effect of rutting on polymer modified binder and also determined the best modified asphalt (latex and polyacrylates) can be used to against rutting. The HMA mixtures were tested with the Asphalt Pavement Analyzer (APA), which is used as an indirect measure to predict rutting on the field. The mould diameter HMA samples used were 150mm cylindrical and were compacted to approximately 7% air voids. The sample was placed and maintained at a temperature of 60ºC in the APA chamber for at three hours before the test started. Two replicates for each mixture were tested for 8000 numbers of wheel cycles and the computer software will measure and averages the rut depths. Figure 4.3 and Figure 4.4 shows the rut depths at the end of 8000 cycles, and other modified asphalt such as latex and polyacrylates. The APA rut depths obtained from the rutting test show that polymer modified binder which using latex is the most resistant to rutting with an average rut depths of 5.1mm. The modified asphalt with polyacrylates average rut depth is 6.5mm while the control sample is 8.00 mm. Therefore, polyacrylate was considered as more resistant to rutting compared with control samples. This shows that the polymer modified binder with latex is the most resistant to rutting followed by polymer modified binder with polyacrylate. This could be concluded that the properties of unmodified binder was not strong enough in binding with aggregates compared to the binding properties of modified asphalt with aggregates. It is also said that hence its natural characteristics which is rubber, the latex tends to glue itself more strongly to the aggregates and providing strong HMA mixtures. This suggests that adding polymer into binder could enhance the performance of the binder itself. 63
  64. 64. Rut Depth Control latex 14 12 Depth(MM) 10 8 6 4 2 0 0 401 801 1201 1601 2001 2401 2801 3201 3601 4001 4401 4801 5201 5601 6001 6401 Cycles (60 Cycles Per Minute) Figure 4.1 Asphalt Pavement Analyzer Graph (control and latex sample) for 19 mm nominal size 64
  65. 65. Rut Depth Control Polyacrlate 14 12 Depth(MM) 10 8 6 4 2 0 0 400 800 1200 1629 2029 2429 2829 3229 3629 4029 4429 4829 5229 5629 6029 6429 Cycles (60 Cycles Per Minute) Figure 4.2 Asphalt Pavement Analyzer Graph (control and polyacrlate sample) for 19 mm nominal size 65
  66. 66. Rut Depth Control Latex 14 12 Depth(MM) 10 8 6 4 2 0 0 401 8011201 1601 2001 2401 2801 3201 3601 4001 4401 4801 5201 5601 6001 6401 6801 7201 7601 8001 Cycles (60 Cycles Per Minute) Figure 4.3 Asphalt Pavement Analyzer Graph (control and latex sample) for 19 mm nominal size 66
  67. 67. Rut Depth Control Polyacrylate 14 12 Depth(MM) 10 8 6 4 2 0 0 400 8001200 1629 2029 2429 2829 3229 3629 4029 4429 4829 5229 5629 6029 6429 6829 7229 7629 Cycles (60 Cycles Per Minute) Figure 4.4 Asphalt Pavement Analyzer Graph (control and polyacrlate sample) for 19 mm nominal size 67
  68. 68. CHAPTER 5 CONCLUSION AND RECOMMENDATION 5.1. Conclusion The Superpave method using HMA mixtures performances was used in this study to evaluate the rutting performance between modified asphalt and unmodified asphalt of Superpave mixtures. During the preparation of the samples it was noted that the mixes with the polymer modified binder which are latex and poly were difficult to mix compared to preparation of control sample. At lower temperature, it will increase the cooling effects on the mix thus it increases the stiffness of the mix and viscosity of the asphalt. For polymer modified binder the temperature of the pan and velocity of the blade must be aware during mixing in order to stabilize the properties of the polymer modified binder. The compiled final sample was obtained through the calculation where the weight of aggregates and asphalt were being adjusted and the preparation sample was based on the Superpave mix design procedures. The HMA mixtures were tested in Servopac Gyratory Compactor, and Asphalt Pavement Analyzer and their evaluation of ruting performance were compared with modified (latex and poly) and unmodified (control) asphalt of HMA mixtures. Meeting the current rutting performance requirement appears to result in high rutting depth for control samples; consequently these mixtures may have poor rutting resistances even though these samples may meet the standard of the Superpave mix design. It appears that at lower asphalt contents which the OBC is lower such as 5.3% for latex, the 68
  69. 69. aggregate may have greater impact on the mixture performance of rutting, overriding that of the asphalt. The rut depths were measured and analyze for the sample tested in the APA seems to have a correlation with rutting resistance of the sample. In this study, it was determined that average rut depth of control, latex and polyacrylates at 6500 cycles were 7.5mm, 4.9mm and 6.5mm respectively. It was obtained that latex has the least depth of rut compared to control and polyacrylate hence it show that latex is highly recommended as a polymer modified binder to use in road construction in purpose to against rutting. The sample with high rut depth in the APA corresponds to have a low rutting resistance of the sample, while a relatively low depth of the rut in the APA also relates to a relatively higher rutting resistance of the sample. 5.2. Recommendation The following recommendations are based on the above findings evolving from this study and other related research efforts. Further study and more data are required to validate the findings and conclusions as well as increase the level of confidence in these findings. i. The rate of change of weight of aggregates and asphalt content, , measured from compaction in the Servopac Gyratory Compactor may in terms of density will be a potential parameter for assessing the rutting resistance of coarse mixtures in the laboratory and, therefore, should be investigated further for this purpose. It must also be investigated for fine mixtures. ii. Rut depth measured from the APA has a potential relationship with the rutting resistance of mixtures and could be used to predict the rutting performance of mixtures in the laboratory. 69
  70. 70. iii. Study can be conducted by using all modified asphalt in three types of gradation such as 9.5 mm NMAS and 12.5mm NMAS through an engineering test such as APA to observed the correlation of rutting on different gradation. iv. The study also recommended to be done by adding some additive such as hydrated lime in a small percentage to the different types of hot mix asphalt gradation. The outcomes of the research are to determine whether the additives help to resist rutting and identify types of gradation with additives can resist rutting better. 70
  71. 71. REFERENCES A Scholar,G and Page, G.C (1999), Follow Up Evaluation of The Asphalt Pavement Analyzer, Research Report,99-436 Ahmad, J. Abdul Rahman, M.Y and Hainin M.R (2011), Rutting Evaluation of Dense Graded Hot Mix Asphalt Mixture. International Journal of Engineering and Technology, 11, 5660 Choubane, B, Page, G.C and Musselman, J.A (1998), Investigation of the Suitability Asphalt Pavement Analyzer for Predicting Pavement Rutting, Research Report,88-427 Garber, N.J. and Hoel, L.A. (2010), Traffic and Highway Engineering, Cengage Learning,Usa, Edition 4 Hassan, A. and Hj. Suffian, Z. (2008), Speciality Mixes in the New Malaysian Public Work Department Road Specification, Highway Materials and Construction, 1,4-10 Hafeez, I., Kamal, M.A and Mirza, M.W (2010), Evaluation of Rutting in HMA Mixtures Using Uniaxial Repeated Creep and Wheel Tracker Tests. Pak. J. Engg. & Appl. Sci., 7, 55-64 Moghaddam, T.B., Karim, M.R. and Abdelaziz, M. (2011), A review on fatigue and rutting performance of asphalt mixes. Scientific Research and Essay, 6(4) Muzaffar Khan, K, Page, G.C and Ahmed Kamal, M (2012), Rutting Based Evaluation of Asphalt Mixes, Pak. J. Engg. & Appl. Sci.,11, 60-65 Pareek, A, Gupta, T and K Sharma, R (2012), Performance Of Polymer Modified Bitumen For Flexible Pavements Pak. J. Engg. & Appl. Sci.,1, 1-10 Thompson, M.R. and Nauman, D. (n.d.), Rutting Rate Analyses of the AASHO Road Test Flexible Pavements. Transportation Research Record, 1384, 36- 48 71