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Rutting resistance in warm mix asphalt


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rutting resistance of warm mix asphalt incorporating sasobit

rutting resistance of warm mix asphalt incorporating sasobit

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  • 2. 2 TABLE OF CONTENTS TITLE PAGE TITLE i TABLE OF CONTENTS ii LIST OF TABLES iii LIST OF FIGURES iv CHAPTER 1 INTRODUCTION 9 1.1 Background of the research 9 1.2 Problem Statement 11 1.3 Objectives 12 1.3.1 Aim 12 1.3.2 The objectives are as follows 13
  • 3. 3 1.4 Scope of research 13 1.5 Organization of the thesis 14 CHAPTER 2 LITERATURE REVIEWS 15 2.1 Introduction 15 2.2 Warm-mix asphalt 16 2.2.1 Benefits of utilizing WMA 18 Environmental Benefit 19 Paving Benefit 22 Economic Benefit 24 2.3 Warm Mix Asphalt Technologies 24 2.3.1 Organic-based WMA technologies 25 2.3.2 Chemical Additive-based Technologies 25 2.3.3 Water-based WMA Technologies 26 2.3.4 Water Bearing Additive Technologies 26 2.4 Basic Materials in Warm Mix Asphalt 27 2.4.1 Aggregate 27 2.4.2 Binder 28 Types and Grades of Bitumen Characteristics of Bitumen 29 29
  • 4. 4 2.5 Problems Related with Warm Mix Asphalt 30 2.5.1 Moisture Susceptibility of WMA 31 2.5.2 Rutting 31 2.5.3 2.5.4 2.5.5 2.5.6 2.5.7 2.5.8 2.5.9 Insufficient data for evaluation Long term performance Water presence Economical Low temperature behavior Life cycle assessment Use with SBS polymer modified bitumen 31 32 32 33 33 34 34 2.6 Anti-stripping agents 35 2.6.1 Hydrated lime 35 2.7 2.8 2.9 2.10 2.6.2 Liquid Anti-Stripping Agents Mineral Filler Pavement modifier Stripping Rutting 36 36 37 39 40 2.10.1 Types of Rutting 42
  • 5. 5 2.10.2 2.10.3 2.10.4 2.10.5 Causes of Rutting Factor Affecting rutting Mechanism of rutting Laboratory Test Related to Rutting Wheel Tracking device 44 45 46 48 48 2.11 Other test Related to rutting 49 2.11.1 Homburg wheel tracking device 49 2.12 Summary 50 CHAPTER 3 METHODOLOGY 52 3.1 Introduction 52 3.2 Laboratory tests procedures 54 3.3 Materials selection 3.3.1 Asphalt binder 3.3.2 Softening Point 3.3.3 Penetration Test 3.3.4 Rational viscosity test 54 54 55 55 56 3.4 Dynamic Shear Rheometer 56 3.5 Aggregates 3.5.1 Aggregate impact value test 3.5.2 Sieve analysis test 57 58 58
  • 6. 6 3.5.3 Flakiness and Elongation Index Test 59 3.6 Sample Preparation 60 3.7 3.8 3.9 3.10 Warm mix asphalt additive Design of binder content Moisture Susceptibility test Rutting Tests 60 61 62 63 3.10.1 Wheel tracking test 63 3.10.2 Compaction of specimen for wheel tracking test 64 3.11 Analysis and discussion CHAPTER 4 EXPECTED RESULTS 4.1 Expected Result 65 REFERENCES 67
  • 7. 7 LIST OF TABLES 2.1 Recommended amount of some available WMA additive (Oliveira j, et al, 2010). 18 2.2 Emission reduction Measured from WMA Projects (Gandi, 2008) 19 2.3 Placement and compaction temperature, (Gandhi 2011) 20 2.4 Emission reduction in plants with WMA (%) (D’angelo et al., 2008) 21 2.5 physical Properties of the Mineral Fillers 37 2.6 (Kandahar, et al, 2003) 46 3.1 Gradation limit for AC 14 according to JKR/SPJ/2008 59 3.2 Standard specification test for bituminous mixture 61 LIST OF FIGURES 2.1 Classification of Asphalt Mixture Types According to Production Temperature and Fuel Usage (D’ Angelo et al, 2008). 21 2.2 Modification of binder Temperature/viscosity relationship (Jean-Martin et al, 2008) 23 2.3 Temperature-viscosity relationship 25 2.4 Stripping in pavement (pavement interactive,2010 40
  • 8. 8 2.5 Rutting pattern on road 42 2.6 Determination of rutting depth (highway association, 1999) 42 2.7 Characterization of downward and total rutting, (Williams and Romero, 2009) 43 2.8 Wheel Tracker Solid Rubber Tyre (After Cooper, 2006) 48 2.9 Hamburg Wheel-Tracking device (Hans,2006) 50 3.1 Research methodology flow chart 53
  • 9. 9 CHAPTER 1 INTRODUCTION 1.1 Background of the Research Conventional hot mix asphalt (HMA) has been the primary material used in asphaltic paving in past decades. Recently, compared to conventional HMA mixtures, warm mix asphalt (WMA) mixtures have shown great potential and offer benefits not given by HMA mixtures, since the WMA mixtures can produce asphaltic layers at lower temperatures.WMA additives can reduce the viscosity of the binder or mixture; thus, the production and compaction temperatures can be lower, compared to those needed for conventional HMA (Kim, 2011). WMA originated in Europe and has been used only recently in the United States (Wasiuddin et al. 2007). Warm Mix Asphalt (WMA) is mixes that are manufactured and spread at lower temperatures than Hot Mix Asphalt. This temperature reduction of 20-40 0 C has led to the following temperature based classification of asphalt mixes: Hot Mix Asphalt or HMA (190-150o C);Warm Mix Asphalt or WMA(100-140o C);Half-Warm Mix Asphalt or HWMA (60-100O C)(The use of Warm Mix Asphalt, 2010; Vaitkus et al, 2009).The WMA temperature reduction is the result of recently developed technologies that involve the use of organic additives, chemical additives, and water-based or water
  • 10. 10 containing foaming processes (You and Goh, 2008;Zaumanis, 2010).Even though these technologies quite different, but they have the same function to lower the bitumen viscosity, improve workability and emission condition. One of the causes of pollution associated with the construction of transportation infrastructure is the emission of greenhouse gases into the atmosphere (Rubio, 2011).Curtis (2009) reported that greenhouse gases emission (CO2) produced anthropogenic climate change and raised global concern on global warming. The elevated daily temperature, rising sea level, more frequent intense precipitation events, and increases in hurricane intensity has a physical impact related to both infrastructure and the operations of various transport modes. So the used of WMA technologies can help improve the environment because it produces asphalt t temperature 20-40o C lower in comparison to Hot Mix Asphalt. Even though the use of Warm Mix Asphalt technology has many advantages, Kim et al., (2012) reported that asphalt mixture prepared using the WMA additives suffered the increasing tendencies to rutting, in contrary decreasing the aging of asphalt binder due to mixing and compaction at lower temperatures. Rutting is one of the most important distresses for asphalt pavement. It is caused by material consolidation and lateral movement due to repeated heavy wheel loadings on the various pavement layers/subgrade. The distress is manifested by a depressed rut along the wheel path on the pavement surface. The rutting distress is viewed as not a structure failure, but a serious safety hazard to vehicles because hydroplaning can occur in the presence of rutting in rainy weather, resulting in serious traffic accidents. Moreover, vehicles tend to be pulled towards the rut path, making it difficult to drive. Many factors can contribute to the rutting distress of pavement, such as environment (high temperature), truck speed and tire contact pressure, the method to prevent the rutting are primarily though engineering an asphalt mixture with improved shear resistance to withstand problems posed by the environment and traffic loadings. However, the addition of warm mix additives into asphaltic mixture can complicate the engineering process; more knowledge is needed to assess the influence of the warm additives to the pavement rutting performances (Mallick et al, 2009).
  • 11. 11 1.2 PROBLEM STATEMENT Conventional hot-mix asphalt (HMA) has been the primary material used in asphaltic paving in past decades. However, compared to conventional HMA mixtures, warm-mix asphalt (WMA) mixtures have shown great potential, and offer benefits not given by HMA mixtures, since the WMA mixtures can produce asphaltic layers at lower Temperatures, without compromising pavement performance. WMA materials can reduce the viscosity of the binder by the addition of warm-mix additives; thus, the production and compaction temperatures can be lower, compared to those needed for conventional HMA. One of the primary benefits of WMA is the opportunity to reduce carbon dioxide emissions during the production and compaction of asphalt mixtures. This could support the objective of reducing greenhouse gas emissions set by the Kyoto Protocol, as well as allowing asphalt mixture plants to be located in some areas with strict air regulations. In addition, WMA technology presents other obvious advantages, such as less fuel usage, greater distances that asphalt mixtures can be hauled to paving sites, better working conditions, an extended paving season, and the potential use of more Reclaimed asphalt pavement (RAP) materials ( Mallick et al,2008). By heating and dry at lower temperature will lead moisture content incomplete dryness and will affect aggregate-bitumen bonding and potentially will reduce the durability of mixes. Also lower production temperature will cause rutting and reduce the asphalt binder oxidation, which results in a mixture with lower stiffness, lesser aggregate drying and possible create a mixture more sensitive to rutting. The decrease of mixing temperature results in increasing binder viscosity makes the asphalt mixture difficult to compact, which results in high air voids, which affects the aggregates and bitumen bonding and easily raise the problem ofrutting(Bennert 2012). Anti-stripping agent, namely hydrated lime is commonly used in asphalt mixes to increase physical-chemical bond between the bitumen and aggregate and improve wetting by lowering the surface tension of bitumen.
  • 12. 12 1.3 Objectives 1.3.1 Aim The aim of the research is to determine the effect of anti-stripping agents on the pavements under different loading and its resistance to rutting. 1.3.2 The objectives are as follows: (i)To evaluate and determine the rutting potential of compact mixture containing different types of anti-stripping additive using wheel tracking test. (ii)ToevaluateandcomparethecharacterizationofruttingPotentialofasphaltmixturesadded withSasobit®. (iii) TodeterminewhetherreducedcompactiontemperaturesdetrimentallyAffecttheruttingof warmmix asphalt. 1.4 Scope of research The study focus on the rutting resistance of warm asphalt mix by incorporating SasoBit®.The different behavior and properties will be study under the experimental results. the asphalt mixture used for the proposed study will be consist of granite aggregate and conventional bitumen grade 80/100,along with hydrated lime,PMD and ordinary Portland cement as a filler.
  • 13. 13 The different experiments on specimens such as aggregate properties, sieve analysis, and binder content determination tests will be conducted. Binders with stipulated SasoBit®. contents will be evaluated using the dynamic shear rheometer to investigate rheological behaviors after being conditioned in a rolling thin film oven (RTFO).The effectiveness of anti-stripping additives will be evaluated through the wheel tracking test, indirect tensile strength test to evaluate the effectiveness of anti- stripping agents. 1.5 Organization of the Thesis A general introduction to the research project is presented in chapter 1. Chapter 2 provides a literature review of recent WMA implementation and technologies globally. This chapter also describe in detailed the different technologies used for WMA production and the behavior of anti-stripping agent and their role in minimizing the binder viscosity. The methodology used to conduct the research is given in chapter 3.this chapter also discuss and evaluates the properties of the materials used in accordance to test standards. In addition, detailed explanations on additives used were included in this chapter. Moisture damage, temperature reduction effects, use of mineral fillers to improve rutting and stripping resistance were highlighted as well. the chapter 4 discuss the results analysis, and different tests auto comes for the rutting resistance of the asphalt mixes incorporating anti-stripping agents and pavement modifier in optimum quantity. Chapter 5 concludes the outcome of the research project and highlights some recommendations for future studies. The schematic diagram summarizing the overall experimental approach is shown in figure.
  • 14. 14 CHAPTER 2 LITERATURE REVIEW 2.1 Introduction The rapid construction of new asphalt pavements, the asphalt industry has been contributing to greenhouse gas emissions released into our atmosphere. Greenhouse gas emissions cause many environmental problems for our earth. Many gas emissions soak up infrared radiation from the atmosphere, trapping heat in our lower atmosphere.(EnergyInformation Administration, 2005).According to computer- stimulated models, the increase in gases will always result in Earth’s temperature rising. Although these are just computer models, the actual temperature of the Earth has increased 0.6ºC over the past 100 years (Energy Information Administration, 2005). The asphalt sector emitted 830,000 tones of CO2 (CO2) in 2007 from the manufacture of 26 million tons (Mt) of product in 350 plants (Mineral Products Association, 2007). On average 30-50% of the costs at an asphalt plant are for emission control (Energy InformationAdministration, 2005). The Hot Mix Asphalt Concrete Industry has produced around 1600 million metric tons of Hot Mix Asphalt (HMA) during 2007 all around the world (European Asphalt Pavement Association, 2007).Thus to produce one metric ton of HMA need Around 85 kWh of energy (European Asphalt Pavement Association, 2007). This means that the whole industry of HMA consumed 0.28% of the world’s crude oil
  • 15. 15 production. The aggregate moisture content is the main deciding factor for the level of energy consumption during the whole production process of HMA (ANG et al.1993). To reduce and avoid the huge amount of GHS gases and energy consumption the warm mix asphalt techniques are introduced. Warm Mix Asphalt (WMA) additives and technologies allow asphalt to be mixed and placed with mineral aggregates at relatively lower temperatures, 20 to 55°C (35 to 100°F) lower than typical HMA (Mallick et al., 2009).Recently, there have been products developed, such as Sasobit®, that decrease viscosity of asphalt at a lower than conventional mix temperature, which can in turn reduce greenhouse gas emissions and energy consumption. These technologies reduced asphalt binder viscosity and enabling the coating of aggregates particles completely at lower temperatures. The incorporation of WMA also tends to improve Compaction reducing the permeability and binder hardening caused by aging, improving the performance of the asphalt mix in terms of cracking resistance and susceptibility to moisture. 2.2 Warm-mix asphalt Warm asphalt mixtures is currently used throughout the world, aiming to save energy and reducing emission during production process, without decreasing the in-service properties and field performance of asphalt mixture. These properties can be achieved by incorporating the chemical additives, which works to reduce the moisture level without disturbing the physical properties of mixture. There is a lot of additive and anti- stripping agents are used nowadays to reduce the fuel and emission during preparation process.WMA are generally produced in a temperature range from 100 to140 C, while half-warm mix asphalt (HWMA) are fabricated between 70 and 100 C. The temperature decrease is around 30C for the first case and can attain up to 80 C for the second case (World Road Association, 2008).
  • 16. 16 The evaluations carried out in Europe, show it clear the decrease of different emission throughout the production process in plant, as follows: 30–40% for CO2(carbon dioxide) and SO2(sulfur dioxide), 50% for VOC (volatile organic compounds), 10–30% for CO (carbon monoxide), 60–70% for nitrous oxides, and 25– 55% for dust. Reductions from 30% to 50% for asphalt aerosols/fumes and polycyclic aromatic hydrocarbons (PAHs) have also been reported, which have a substantial influence on the exposure of the workers and the surrounding area of construction sites to those products (European Asphalt Pavement Association,2010). There are some concerns related to WMA cost in its whole lifecycle, as the technologies available for WMA generally increase the initial production cost. On the one hand, this can be connected to the additional equipment needed for plants, allowing the use of specific technologies or additives. On the other hand, the use of additives brings some supplementary cost, which could be only partially compensated by lowering the operating temperature. (Button, et al, 2007) There is some danger related to the WMA because the production of additives also emits carbon (Zaumanis, 2010). Warm-mix asphalt (WMA) is much like Hot-Mix Asphalt(HMA), but it is produced at lower plant temperatures than conventional HMA. The key benefits of the reduced production temperature of WMA include the reduction of fuel consumption and emissions (Hurley and Powell 2006) The WMA technology can be classified in three main groups’ organic additives, chemical additives and foaming technologies. Reediest™ WMX and Casabas RT are both chemical additives. Those types of products chemically enhance active adhesion and improve the wetting of aggregates by bitumen without changing considerably the binder performance (Silva and Almeida, 2009).
  • 17. 17 Table 2.1: Recommended amount of some available WMA additive (Oliveira, et al, 2010). 2.2.1 Benefits of utilizing WMA Warm-mix asphalt has a lot of benefits over the conventional HOT. These benefits depend upon which method and approach of WMA is used for production of WMA. There is a lot of approaches are used, which all have different perceptive benefits and concern. The most common and visible benefits of WMA are the following: (a) Environmental (b) Paving (c) Economic Additive Additive rate range Typical additive rate Organic additive Astec PER 0.5%-0.75 by total weight of RAP( only for high level of RAP --- Asphaltan- B 2-4% by weight of total binder 2.5% by weight of binder sasobit 0.8-4% by weight of total binder 1.5% by total weight of total binder Sonne warmix 0.5-1.5% by weight of total binder 0.75% -maximum recommender for unmodified virgin mixes Chemical additive Cesa base RT 0.3-0.5% by weight of binder --- Rediset WMX 1.5% -2.5% by weight of binder ------ Evotherm About 5% of diluted chemical packed by weight of binder ------
  • 18. 18 Environmental Benefit The idea of WMA arises as a challenge to the emissions during production and compaction which directly affects the health of workers and a key element for environmental degradation. The HMA plants emit a variety of particulate matters and gaseous pollutants. The gaseous emissions include sulfur dioxide, nitrogen oxides, carbon monoxide, and volatile organic compounds. The Environmental Protection Agency (EPA) has offered an example to illustrate the emissions estimates. If a natural gas-fired drum mixing dryer produced 200,000 tons per year, the estimated emissions during that period would be 13 tons of carbon Monoxide, 5 tons of volatile organic compounds, 2.9 tons of nitrogen oxides, 0.4 tons of sulfur oxides, and 0.65 tons of hazardous air pollutants (U.S. EPA Report 2000).One of main benefits of WMA is significant emission reduction during the mixing and Compacting.(Mallick et al. (2009) did the assessments on the WMA additives and concluded that temperature seems to be the main driving factor for carbon dioxide emissions. Hence reducing temperature during production and compaction of asphalt mixing can significantly reduce the carbon foot print. Gandhi (2008) did the field demonstration of WMA projects in India and compared to the HMA and concluded the following table. Table 2.2: Emission reduction Measured from WMA Projects (Gandi, 2008) 2.2 Ashpa -min Sasobit Evotherm WMA -foam Sulfur Dioxide 17.60% --- 81% N/A Carbon 3.20% 18% 46% 31% Carbon monoxides N/A N/A 63% 29%
  • 19. 19 Gandhi (2011) warm and conventional hot mix evaluation on two different projects on roads in India. The ambient air temperature was around 37 °C at the start of the day, rising to a maximum of 42°C.The field experimental data is presented in the following table. Table 2.3 Placement and compaction temperature,(Gandhi2011) The use of WMA has three benefits: air pollution, fossil fuel depletion, and smog formation. Further WMA could reduce 24% of impact of air pollution, and 18% in fossil fuel depletion caused by HMA.It can also reduce smog formation reduction of 10%. The use of WMA could provide a reduction of 15% to the environmental impacts induced by HMA.( Hassan 2009)At temperatures above the melting point, they reduce the viscosity of the binder to make it possible to reduce the production temperature whereas, below the melting point, they tend to increase the stiffness of the binder (Perkins, 2009). Nitrogen Oxide 6.10% 34% 58% 62% Total particular matter 35.30% N/A N/A N/A Volatile organic compounds N/A 8% 25% N/A 2.3 Conventional hot mix Warm mix Production temperature (C) 160 130 Mix delivery temperature (C) 140-150 125-130 Mix Temperature behind paver (C) 130-145 120-125 Break down compaction temperature (C) 130-145 110-115 Finished PTR compaction temperature (C) 90-100 70-80 Mix haul time 15-25 15-25 Core area voids after compaction (%) 5-7 3.99
  • 20. 20 Figure 2.1: Classification of Asphalt Mixture Types According to Production Temperature and Fuel Usage (D’ Angelo et al, 2008). Another notable benefit of WMA usage instead of HMA in road pavements is the reduced emissions produced from the asphalt producing plants Based on processing conditions and production temperature, WMA plant emissions were reported to represent 30 to 98% of HMA emissions (Hossain et al., 2009). A considerable reduction in fume emissions was reported between HMA produced at 165°C and WAM-Foam prepared at 115°C, from 0.2-0.5 mg/m3 range to below 0.05 mg/m3 . Button et al. reported that a production temperature reduction of 47°F using Aspha-Min resulted in a 75% reduction in fume emissions (Button et al., 2007) Table 2.4: Emission reduction in plants with WMA (%) (D’angelo et al., 2008) Emission Norway Italy Netherland France 2.4 CO2 31.5 30-40 15-30 23 SO2 N/A 35 N/A 18 VOC N/A 50 N/A 19 CO 28.5 10-30 N/A N/A NOX 61.5 60-70 N/A 18* Dust 54 N/A N/A N/A
  • 21. 21 Paving Benefit The basic mechanism that make suitable WMA to reduce the binder viscosity and in return it cover easily the aggregates as compare to conventional HMA where intensive heat required to reduce the binding viscosity, is the techniques of WMA. WMA can improve mixture compatibility in both the Super pave gyratory compactor and the vibratory compactor. There is many benefits of WMA including facilitating compaction,transportation,recycling at higher rates, placement of multiple lifts within a short time window and placement of Bituminous materials on crack-sealed substrates without the occurrence of bumps: (i) Compaction Warm mix technologies improve compaction. The WMA objectives include temperature/viscosity relationship modification in such manner that, suitable mixing and compaction viscosities are achieved at lower temperatures, while adequate viscosity is maintained at service temperatures.( Jean-Martin et al, 2008). (ii) Lower Viscosity WMA technologies have the ability to reduce the binder viscosity. Several advantages are gained from the lower viscosity as the workability of the asphalt mixture is improved. Better compaction can be achieved and a lower number of roller passes are needed to reach the targeted density .Hence, WMA can help extend the paving season
  • 22. 22 and enable hauling the asphalt mix for longer distances and preserve sufficient workability for placement and compaction (Hossain et al., 2009). Figure 2.2: Modification of binder Temperature/viscosity relationship (Jean-Martin et al, 2008) (iii) Oxidative Hardening Oxidation of the asphalt binder starts during its mixing with hot aggregates and continues throughout the pavement life. Age hardening takes place due to oxidation resulting in the stiffening and the hardening of the binder with the temperature of the asphalt oxidation reaction a significant factor that determines the rate of formation and the type of oxidized species formed (Hossain et al., 2009). Hence, theoretically, using WMA technologies can possibly reduce the susceptibility of an asphalt mixture to aging and cracking as the mix is not exposed to the elevated production and placement temperatures which can lead to a longer pavement service life.
  • 23. 23 Economic Benefit WMA can usually lower asphalt-mixing temperatures by 15 °C to 30 °C compared to Conventional HMA. This could reduce burner fuel costs by 20% to 35%. Fuel savings could be 50% or more when producing low-energy asphalt concrete and low-energy asphalt in which the aggregate is not heated above the boiling of water. However, Additional costs could be necessary for equipment and additives (D’Angelo et al. 2008). Based on the WMA technique used and conditions; the energy consumption range is 20 to 75% of HMA, and the burner fuel savings range from 20 to 35% (Hossain et al., 2009). For processes such as low-energy asphalt concrete, and low energy asphalt (LEA), fuel savings could reach more than 50%. Previous studies showed that the WAM-Foam WMA plant processing can be implemented with 40% lower energy consumption than HMA. Moreover, a 30% in energy consumption reduction was reported in measurements conducted for Eurovia when using Aspha-Min because of a 54 to 63°F decrease mix temperature (Button et al., 2007). The true economic gain from the reduced energy consumption relies on the type of energy and its cost at the time. With continuous surges in the prices of energy sources, the non-renewable sources specifically, WMA could turn into an economically attractive alternative to HMA in the near future (Hossain et al., 2009). 2.3 Warm Mix Asphalt Technologies There are many different products and processes that are used to achieve this reduction in temperature but the technologies can generally be grouped into four main categories.
  • 24. 24 2.3.1 Organic-based WMA Technologies Organic additives are waxes that are used to reduce the viscosity of asphalt binder at lower temperatures. Sasobit®, produced by Sasol Wax Americas, Inc. is an example of a wax based Organic additive and is the most often used organic additive in the United States.( Sasol Wax North America Corporation,2011). Figure 2.3: Temperature-viscosity relationship with addition of organic additive (Anderson, et al., 2008) 2.3.2 Chemical Additive-based Technologies Chemical additives, which are also known as surfactants, are an emerging group of additives for WMA. Surfactants help the asphalt binder coat the aggregate at a lower temperature. Evotherm™ Emulsion Technology (ET) which is produced by MeadWestvaco Asphalt Innovations is an example of a chemical additive. The process
  • 25. 25 consists of the additive being blended with asphalt that is mixed with the aggregates to produce asphalt mixtures with a 55⁰C (100⁰F) reduction in production temperature. Evotherm™ requires no plant modification and the majority of the water in the emulsion flashes off when the emulsion is mixed with hot aggregates (MeadWestvaco Asphalt Innovations ,2011). 2.3.3 Water-based WMA Technologies Small amounts of water are introduced into the heated asphalt binder to form a controlled foaming effect that results in a small increase in binder volume and a reduction in viscosity. Water-bearing additives such as synthetic zeolites are used to enhance aggregate coating by asphalt at lower temperatures. Zeolites have porous structures that include approximately 20% water. When heated to a specified temperature, the water is released and foamed asphalt is produced (5). Advera®, produced by the PQ Corporation, is an example of a water-bearing additive. Advera® is a hydrated zeolite powder that can be added to reduce the production temperature of asphalt mixtures by 10⁰C to 21⁰C (50⁰F to 70⁰F). Advera® can be added to asphalt mixtures without any mixture design changes. (PQ Corporation, 2011). 2.3.4 Water Bearing Additive Technologies Foamed asphalt is produced by adding a small amount of water to the heated asphalt through the means of a nozzle or damped aggregate. Introducing the moisture into a stream of hot asphalt causes spontaneous foaming of the asphalt which increases the surface area of the asphalt while lowering its viscosity. This technology is believed to be the most cost effective from among the WMA technologies since it does not require any costly additives to be added to the mixture(Ala, et al, 2011)
  • 26. 26 2.4 Basic Materials in Warm Mix Asphalt 2.4.1 Aggregate Aggregate is the main component of any asphalt pavement. American Society Testing Materials (ASTM) had define aggregates as a granular or coarse material in the form of mineral such as crushed stone, sand and gravel. Aggregates can be used with cementing medium to form mortars or concrete or alone as in base courses, in the presence of medium like water. Aggregate can generally be described as the rigid, static mineral material component of the mixture, which provides a stable, structural skeleton to the mixture. This mechanically stable skeleton/framework primarily contributes to the load-supporting capacity of the pavement mixture. Consequently, the performance of a mixture is heavily influenced by the aggregate. Aggregate is the main component of an asphalt mix, generally consists of 90-95% by Weight and 75-85% by volume. (Asphalt Institute, 2007). The aggregates have significant influence on the mixture performance since the mixture consists mostly of aggregates. Brown et al (1996) classify these different sized aggregates as coarse and fine aggregate as well as filler According to their size. The coarse aggregate is described as particles retained on a No. 4 sieve (4.75 mm), fine aggregate as particles passing the No. 4 sieve (4.75 mm) But retained on the No. 200 sieve (0.075 mm) and the mineral filler as at least 70% of The material passing the No. 200 sieve (0.075 mm).furthermore, aggregates are also used in sub-base layers for rigid and flexible pavements. The aggregates either will be natural or obtained by some mechanical process. The natural aggregates are obtained from open excavation of Rocky Mountains which have specific quality of rocks capable of engineering properties. Broadly the natural aggregates can be classified as 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 surface
  • 27. 27 resources. Gravel also can be crushed, since it has a large contribution in constructing asphalt pavement or bases. The formation of sand is either from the erosion of bedrock or mechanically crushed. 2.4.2 Binder The different names are used for binder in different countries like binder, bitumen, and asphalt. The Asphalt Institute (2007) describes binder as viscous Liquids or solids mainly consisting of hydrocarbons and their derivatives, which are soluble in carbon disulphide. At room temperature the binder is nonvolatile but with heating it’s become softens. The binder is also called visco-elastic material; it means the binder behavior changes with change in temperature or loading time. Modified binder such as polymer modified binder are recommended to improve resistance of asphalt binder against rutting and thermal cracking (Moghaddam, et al, 2011).This is class of black or dark-colored (solid, semi-solid or viscous) cementations substances, natural or manufactured, composed principally of high molecular weight hydrocarbons, of which asphalts, tars, pitches, and asphaltenes are typical. In other words, it acts as the glue that holds the road together ( Youtcheff,et al, 2000).Bitumen or asphalt is a constituent of petroleum with most crude petroleum containing some asphalt. Crude petroleum from oil wells is separated into its fractions in a refinery by a process called distillation. During the process, crude petroleum is fed into a tube still, where its temperature is quickly raised for initial distillation processes. It then enters a fractionating tower where the lighter or more volatile fractions vaporize and are drawn off for further refining. Residue from this fractionating process is the heavy component of crude petroleum, which includes asphalt. However, further refinement is necessary to produce bitumen cement.
  • 28. 28 Types and Grades of Bitumen The two main types of binders are conventional (or penetration grade) and modified (or polymer-modified) bitumen. According to Sabita, (2007) other types of bitumen included cutback bitumen, bitumen emulsions and bitumen rubber. Modified binders are typically used for (i) To increase the mixture’s resistance to rutting of mixture. (ii) To increase resistance to thermal cracking of mixture (iii) To increases durability of mixture Characteristics of Bitumen a) Adhesion: Bitumen has the ability to adhere to a solid surface in a fluid state depending on the nature of the surface. The presence of water on the surface will prevent adhesion. b) Resistance to Water: Bitumen is water resistant. Under some conditions water may be absorbed by minute quantities of inorganic salts in the bitumen or filler in it. c) Hardness: To measure the hardness of bitumen, the penetration test is conducted, which measures the depth of penetration in tenths of mm. of a weighted needle in
  • 29. 29 bitumen after a given time, at a known temperature. Commonly a weight of 100 gm is applied for 5 sec at a temperature of 77 °F. The penetration is a measure of hardness. Typical results are 10 for hard coating asphalt, 15 to 40 for roofing asphalt and up to 100 or more for water proofing bitumen. d) Viscosity and Flow The viscous or flow properties of bitumen are of importance both at high temperature during processing and application and at low temperature to which bitumen is subjected during service. The flow properties of bitumen vary considerably with temperature and stress conditions. Deterioration, or loss of the desirable properties of bitumen, takes the form of hardening. Resultantly, decrease in adhesive and flow properties and an increase in the softening point temperature and coefficient of thermal expansion. 2.5 Problems Related with Warm Mix Asphalt A large number of questions regarding the implementation of this technology, especially about the specifications and quality control need to be answered. Potential drawbacks should be considered in context with the specific technology as different methods have particular flaws, but to generalize, there are some concerns about the performance and implementation of WMA. They are listed below
  • 30. 30 2.5.1 Moisture Susceptibility of WMA The most major concern for WMA is the potential moisture susceptibility of the pavement since significantly reduced production and compaction temperatures might lead to incomplete drying of aggregates, and therefore presence of residual moisture, which could have negative influence on pavement performance, such as rutting, stripping and fatigue cracking. On one hand, given the limited drying time and relatively low temperatures, aggregates may not dried sufficiently, leading to certain amount of moisture trapped in the mixture; on the other hand, to reduce binder viscosity, additives or foaming technologies may be introduced into asphalt binder. Furthermore, these pavements could be subjected to moisture during rainy seasons. Any moisture remaining in or on the aggregates would affect aggregate coating and exacerbate the loss of bond between asphalt binder and aggregates, causing asphalt stripping and premature pavement failure. Typically the loss of bond begins at the bottom of the pavement layer and progresses upward ( Hossain., et al,2009). 2.5.2 Rutting Premature rutting has been reported for surface asphalt concrete in different studies. This has been mostly related to decreased ageing at lower production temperatures and increased moisture content for foaming technologies. 2.5.3 Insufficient data for evaluation Since the field test sections constructed in United States are less than seven years old and the sites in Europe (Germany and Norway) are somewhat over ten years old, it is
  • 31. 31 too early to comment on long term performance. To date, in US no notable negative long term performance has been reported (Arif and Button,2008). and in Europe the trial sections of WMA have performed the same or better than HMA overlays (John, et al,2008,). It must be noted that in the US there are number of government programmers’ for WMA evaluation, whereas in Europe examinations mostly depend on private companies which means significantly less independent review of different WMA technologies. 2.5.4 Long term performance Theoretically, because the better compaction possibilities may result in higher density for WMA, this could result in problems due to insufficient number of air voids in the mixture to ensure desirable bitumen content. This may lead to problems with moisture susceptibility, cracking and oxidative ageing. A similar problem is connected with lower mixing temperatures indicates less binder absorption into the aggregates, which may lead to the same faults as described above. 2.5.5 Water presence Foaming and some of the chemical WMA technologies are somewhat connected with the introduction of water in the initial mixing process. Because of possible incomplete vaporization of water during the mixing and laying process residual water in the mixtures may cause problems of premature rutting and stripping of pavements. Therefore special attention must be paid to the evaluation of potential moisture damage in the laboratory. This is especially important with any foaming technologies and although most of them use chemical anti -stripping additives to improve coating and
  • 32. 32 adhesion different initial material moisture content together with poor water resistant mix formula may cause some coating problems. 2.5.6 Economical There are some concerns about the implementation of WMA production technology because of its cost. It is necessary to prove the potency of WMA compared to HMA so that the use of this technology becomes widespread. It must be established whether reduced energy consumption will reduce the overall costs of WMA production. If no proof of lower production costs are established, it may be possible that contractors will not choose this technology for its other benefits alone, and if no stricter emission regulations are obligated, the WMA technology could not become widespread. Increase in costs may arise from: (i) The investment and the depreciation of plant modification; (ii) The costs of additives; (iii) Possible costs for technology licensing 2.5.7 Low temperature behavior The low temperature properties of bitumen used in organic WMA technologies can be slightly different than expected for conventional HMA. Through this attention should be given to change in low temperature behavior if it is relevant for the given climate conditions. This change in performance can be explained through the crystallization of waxes thattend to increase the viscosity and stiffness of the binder. Therefore low temperature binder properties should be evaluated to predict the possible changes of bitumen in WMA.
  • 33. 33 2.5.8 Life cycle assessment Good and easy to use life cycle assessment tool would be necessary to verify the statement of potential environmental benefits. There are concerns that some of the environmental benefits may be offset due to the carbon footprint embodied for producing additives and/or any additional equipment supporting the production of WMA. Since there are still some concerns about the WMA long term performance compared to Hot Mix Asphalt (HMA), life cycle assessment would require information on the longevity of WMA. 2.5.9 Use with SBS polymer modified bitumen Although WMA technologies are fully compatible with Styrene-Butadiene-Styrene (SBS) modified bitumen. ( Michael,et al,2008) states, that modification of bitumen with both SBS polymer and Fischer Tropsch (FT) wax might not be reasonable for performance improvement as the benefit from adding wax to SBS modified bitumen is less than when adding it to pure bitumen, but the results achieved in super-pave applicable temperature range Penetration Grade (PG) are almost the same, thus somewhat “overlapping” the benefits and increasing the costs. However it does not reduce the effects of lower temperature production and paving so it still might be beneficial to use FT-wax with modified binders.
  • 34. 34 2.6 Anti-stripping agents 2.6.1 Hydrated lime The use of hydrated lime for moisture reduction in HMA are well recognized and widely used in industry. The WMA also show the same results of reduction in moisture reduction by gradually increasing the amount of hydrated lime. The moisture content in WMA leads to the problem of stripping. The phenomenon of breaking of the bond between aggregate and bitumen is known as stripping (Amirkhanian, 2010). Moisture damage of asphalt pavement can lead to serious distress, reduced performance, and increased maintenance of asphalt pavements. Localized bleeding, particle degradation, disintegration, potholes, shoving, and structural failure of pavement due to permanent deformation and cracking are examples of moisture-induced damage.(Kennedy TW,2009)Detachment, displacement, emulsification, pour water pressure, hydraulic scoring, and bitumen–aggregate interfacial physical–chemical processes have been identified as the cause of moisture susceptibility problems.( Little DN, Epps JA,2011).the moisture susceptibility is one of the potential disadvantages of WMA mixtures (Roshani,2012).thus to prevent moisture susceptibility ,proper mix design and use of anti-stripping agent is required. one of the most commonly used anti-stripping agents in the world is aggregate coating with suitable agents such as hydrated lime and polymer.(Zhao W,2010).The Mixes containing hydrated lime and liquid anti-stripping agent are stiffer, less susceptible to rutting, moisture damage and cracking. (Tahmoressi, Sebaaly, 2005).the research carried out shows that apart from the sources of aggregates and bitumen, hydrated lime has the most effect on moisture resistance increase (Zhao W et al, 2005).Three forms of lime are used: hydrated lime (Ca (OH) 2), quick lime (CaO), and Dolomitic limes (both types S and N) (Roberts et al, 1996). Several methods exist for adding lime to mixtures.
  • 35. 35 Dry hydrated lime is added prior to the asphalt cement. Georgia DOT adds the dry hydrated lime immediately before the asphalt cement is added (Roberts et al. 1996). 2.6.2 Liquid Anti-Stripping Agents The most common liquid ASAs such as amines, demines, liquid polymers, and solids like Portland cement, fly ash, flue dust, etc. are currently used .Pavement contractors usually prefer liquid ASAs as they are relatively easy to use. (Lu and Harvey,2006). Most anti -stripping agents reduce surface tension between the asphalt and aggregate in a mixture (Tunnicliff et al. 1984).the liquid anti-stripping agents reduce surface tension, and increase the adhesion between aggregates and asphalt. Thus, most liquid anti - stripping agents are surface-active agents (Roberts et al. 1996). The liquid asphalt commonly is mixed with the liquid anti stripping agent prior to adding aggregate to the mix. (Roberts et al.1996). 2.7 Mineral Filler Mineral filler consists of very fine, inert mineral matter that is added to the mixtures to improve the density and strength of the mixture. 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. Filler defined as “finely divided mineral matters such as rock dust, slag dust, hydrated lime, hydraulic cement, fly ash, or other suitable mineral matters, such as carbon black and sulfur, have been used primarily to modify asphalt binder properties, but they do have a role as filler.(ASTM D 242,1995).This specification further requires that 100 percent of the particle shall be finer than 600-gm, 95-100 percent shall be finer than 300-gm, and 70-100 percent shall be finer than 75-gm.
  • 36. 36 Filler may be used for the following purposes. The use and the application of mineral filler in asphalt mixtures are intended to improve the properties of binder by reducing the binder’s inherent temperature susceptibility. (Ratnasamy, 2009). Two theories had been proposed regarding the functions of fillers. The" Filler Theory "presumed that particles coated with bitumen fill the voids in the aggregates."Mastic Theory" proposed that the filler and bitumen combined to form mastic which fills the voids and binds the aggregates.( Csanyi and Cox,1964). (i) Fill the voids (ii) Increase stability and strength (iii) Improve the bond between asphalt cement and aggregate (iv) They stiffen the mixture at the upper range of pavement temperatures with little stiffening at lower temperatures. At low temperatures they appear to toughen the asphalt binder increasing resistance to cracking. (v) Not all mineral fillers are the same or affect mixtures in the same manner. A given filler May extend the asphalt cement or may stiffen the asphalt cement. Gradation parameters alone are not reliable predictors of filler behavior in a mix. The mineral filler shall also be treated as an anti-stripping agent. (JKR, 2008) Table 2.5: physical Properties of the Mineral Fillers Filler Specific Gravity % passing sieve No.200 Portland Cement 3.15 96 Lime stone Powder 2.78 94 Glass Powder 2.65 92
  • 37. 37 2.8 Pavement modifier Asphalt cement requires modification to meet the specifications under certain circumstances. Asphalt cement modification has been in practiced from 50 years. Polymer-modified binders helped to improve the performance of HMA asphalt pavement, but a problem occurs when WMA was introduced. WMA is to be produced and compacted at lower temperatures than HMA but still perform comparably to the HMA. Simply modifying the binder with polymers will only improve the performance of the mixture at high temperatures and this alone will not be enough to lower the production and compaction temperatures and still achieve equal or better performance than HMA mixes. Thus WMA technologies were developed to create an additive or process which would reduce the production/compaction temperatures of the mix and still maintain the desired performance criteria required.WMA technologies generally reduce the binder viscosity and provide complete coating of the aggregate at lower temperatures. According to the European Roads Review 18 (ERR, 2011) these WMA technologies can reduce production temperatures by as much as 40%. WMA technologies are classified by type with regard to how they are implemented. Two main types of WMA technologies are classified, namely foaming technologies and additive technologies. Foamed asphalt is formed by combining hot asphalt binder with cold water. When the cold water comes in contact with the hot asphalt binder, it turns into tiny steam bubbles trapped inside the asphalt binder. This leads to an expansion in the volume of the binder and improves the coating potential of the binder. Warm asphalt mix using foamed asphalt technology (WAM-foam) is a patented process developed jointly by Shell Global Solutions and Kolo Veidekke in Norway. In the WAM-foam production process, two different bitumen grades, soft bitumen and hard bitumen, are combined with the mineral aggregate. The aggregate are first mixed with the softer binder, which is fluid enough at lower temperatures, and then the harder binder is foamed and mixed with the aggregates pre-mixes with the softer binder. However, selecting the right grades of the soft and hard binders is critical to this process. This
  • 38. 38 process makes it possible to produce the asphalt mixture at temperatures between 100°C and 120°C (212 and 250 °F) and compact it at 80 to 110°C (175 to 230 °F) (Koenders et al. 2000). Recently, Astec Inc. in Chattanooga, TN also developed a Double Barrel Green System, where a multi-nozzle device is fitted to a double barrel drum plant. The multi-nozzle device is used to produce microscopic bubbles in the asphalt binder by combining a small amount of water with the asphalt binder before it is introduced to the aggregate. The manufacture claims that this process can reduce the fuel consumption by as much as 11% (Astec Inc, 2007). Generally the asphalt cement is modified to achive the following(Roberts et al, 1996). (i) Lower stiffness (or viscosity) at the high temperatures associated with construction. (ii) Higher stiffness at high service temperatures. This will reduce rutting and shoving. (iii) Lower stiffness and faster relaxation properties at low service temperatures. This will reduce thermal cracking. (iv) Increased adhesion between the asphalt binder and the aggregate in the presence of moisture. 2.9 Stripping WMA mixtures are more prone to moisture damage then HMA mixtures, designed using the same aggregates and binder. The premise of employing WMA technology is to guarantee that WMA pavement must possess similar workability, durability and performance characteristics as HMA using substantially reduced temperature. (Bonaquist, 2011). The major problem with WMA is the potential moisture Susceptibilityof the pavement since the temperature for production and compaction is lower as compared to HMA and it might lead to incomplete drying of aggregates.The presence of residual moisture which could have negative influence on pavement Performance. Moisture content leads to rutting, stripping and fatigue cracking in the
  • 39. 39 WMA. On one hand, given the limited drying time and relatively low Temperatures, aggregates may not dried sufficiently, leading to certain amount of Moisture trapped in the mixture; on the other hand, to reduce binder viscosity, additives or foaming technologies may be introduced into asphalt binder. Stripping is one of the most occurring modes of pavement failure. Stripping is defined as bonding failure between aggregates particles and bitumen and either failure within bitumen structure (Xiao and Zhao,2010).the failure mechanisms of this phenomenon are very complicated.(khodaii, 2012). Figure 2.4 Stripping in pavement (pavement interactive, 2010) Stripping causes a reduction of materials strength over time, manifesting itself in terms of rutting, corrugation, shoving, raveling and cracking distresses (Juang, et al,2007). Some researchers believe that the low mixing and compaction temperatures can lead to increased stripping potential in mixes, as a result of retained moisture in aggregate particles (Kazemi and tehrani, 2012). Furthermore, these Pavements could be subjected to moisture during rainy seasons. Any moisture remaining in or on the aggregates would affect aggregate coating and exacerbate the loss of bond between asphalt binder and aggregates, causing asphalt stripping and premature pavement failure. Typically the loss of bond begins at the bottom of the pavement layer and progresses upward (Hossain, 2009).
  • 40. 40 2.10 Rutting The roads are mostly consists of flexible pavements. Road pavements are exposed to various traffic loads, changeable climatic cycles, and different soil characteristics of roadbed, which may result in distortion of pavement layers. These distortions either will be cracks, deformations, deterioration, and, failure and are located underneath the wheel tracks especially where the soil bearing capacity has been weakened during highly varied climatic temperatures. The most common pavement distress involved cracking, and rutting (permanent deformation). Rutting is known as longitudinal depression, which follow the line of wheel paths. The deterioration of pavements due to rutting is the result of heavily travelled flexible pavements. Rutting is the result of permanent deformation due to traffic loading in one or more layers of pavements. Rutting leads to decrease in riding quality. Rutting in pavements causes hydroplaning, severe physiological and safety concern for users. Rutting can be the result of permanent reduction in volume (consolidation/traffic densification), permanent movement of the materials at constant volume (plastic deformation/shear), or combination of both. (Christos and Drakos, 2004).Bituminous concrete plastic properties contribute to permanent deformation under repeated loading. Development of rutting is caused by a combination of densification and shear-related deformation with an increasing number of load applications and may occur in any layer of a pavement structure. (Wang, H., Zhang, Q., and Tan, J. (2009).The deterioration may occur due to lateral plastic deformations especially in high temperature in unstable wearing course or sub grade soil (O Flaherty,1988). Field studies indicated that the rutting is usually influenced by the use of excessive binder content and improper aggregate gradation (Brown and Mahrez, 2008). This excessive binder essentially results in low air void and causes a loss of mechanical friction in the mineral skeleton and eventually leads to a greater level of plastic flow in bituminous pavement matrix(Mahrez, 2008). Varied temperature, adhesion of bitumen with aggregate, speed of vehicle, amount and distribution of traffic, and surface contour are important factors to create rutting in pavements. Shear deformations resulting from high shear stresses in the upper portion of bituminous layer
  • 41. 41 appear to be the primary cause of rutting in flexible pavements. Repeated applications of these stresses under conditions of comparatively low mix stiffness lead to the accumulation of permanent deformations at the pavement surface (Katman, 2006).Rutting or channeling, could be classified in three types: 1) mechanical deformation (rutting in sub grade or base), 2) plastic flow (unstable asphalt layer), and 3) wheel path consolidation ( The Asphalt Institute, 2003). Figure 2.5: rutting pattern on road(Asphalt institute, 2007) Figure 2.6: Determination of rutting depth (highway association, 1999)
  • 42. 42 2.10.1 TYPES OF RUTTING Rutting can be divide into three types, based on the cause and layers in which rutting occurs, and it can be characterized by two components of the original (initial) Pavement profile change which are direct consequences of permanent deformation: uplift and downward deformation (Kandhal and Cooley,2003). Figure 2.7:Characterization of downward and total rutting, (Williams and Romero, 2009) (i) One-dimensional densification (vertical compression) A rut depth caused by material densification is a depression near the centre of the Wheel path without an accompanying hump on either side of the depression. Generally, The densification of material is caused by excessive air voids or inadequate compaction after placement of asphalt material, thereby allowing the material or underlying layers to Compact when subjected to traffic loads This type of rut depth usually results in a low-to moderately-severe level of rutting(Cooley, 2003).
  • 43. 43 (ii) Lateral flow or plastic movement Such longitudinal or lateral distortion of asphalt mixtures is caused by the localized shear failure resulting from overstressing the mixture with high tire pressure (NCHRP Report, 2003). Rutting depression occurs by the lateral flow of material near the centre of the wheel path with humps on either side of depression. This type of depression in pavement usually results in a moderate to highly severe level of rutting. Displacement of materials will occur in those mixtures with inadequate shear strength or an insufficient amount of total voids in the asphalt layer. Low voids after construction can make asphalt to act as a lubricant rather than a binder during hot weather. For visco-elastic materials, such as asphalt mixtures, the time of load affects the amount of deformation that occurs in the material, so distortions will be less on highways with higher speeds than on highways with lower speeds, given the same truckloads. Also this deformation at the constant load conditions will be higher at higher temperatures. Rutting caused by lateral flow is difficult to accurately predict with repeated load tri-axial testing equipment, especially when the asphalt mixture is highly anisotropic, i.e. properties vary with direction ( Transportation Research Board, Washington, DC, 2003). (iii) Mechanical deformation The mechanical deformation or rutting is the consolidation (compaction),or the lateral movement of the unbound materials below the asphalt surface. This type of rutting has been referred to as "mechanical deformation". Mechanical deformation is a result of subsistence in the base, sub base, and/or sub grade and is usually accompanied by a longitudinal cracking pattern at the pavement's surface when the asphalt mixture is too stiff (high elastic modulus). These longitudinal cracks generally occur in the centre and along the outside edges of the ruts(Asphalt Institute, Lexington,A. Cooley, KY, 2003).
  • 44. 44 2.10.2 Causes of rutting Rutting in asphalt pavements has become one of the major distress forms with the increase in traffic volume, tire pressure and axial load. It often happens within the first few years after opening to traffic. (Suo and Wong, 2008).according to the national cooperative Highway Research Program, permanent deformation was selected as the most serious problem for highways and runways in the united states among all the distresses in asphalt pavements.(Witezak,1998).fatigue cracking was rated the second serious problem and thermal cracking the third serious problem with asphalt pavement deterioration. Major rutting is attributed to the decrease in thickness of middle and lower layer, and the driving lane shows a severer rutting. Inadequate compaction is a major cause of the final depth of rutting. The aggregate gradation is also a major contribution to the rutting distress of pavement. The gradation Between 1.18 and 4.75 mm in sieve size becomes finer for the three layers. Show an increase in asphalt content, but the lower layer presents a decrease in asphalt content. The rutting principally occurs due to repetitive shear deformation under a variety of traffic loading. (SHRP, 1991).loading conditions in the form of magnitude, tire pressure, and traffic volume; environmental conditions in the form of temperature; and WMA properties in the form of aggregate characteristics (shape, texture, and structure), and binder type are among the major contributors to rutting resistance.
  • 45. 45 2.10.3 Factors Affecting Rutting Table2.6:(Kandahar, et al, 2003) 2.10.4 MECHANISM OF RUTTING Rutting in asphalt pavements develops because of the densification (compaction) and shear flow in asphalt concrete layers and due to permanent deformations in the aggregate base, sub base and soil sub-grade. Rutting in asphalt concrete pavement usually appears as a longitudinal Depression under the wheel paths of vehicles and a small bulging on the sides. The extent of rutting gradually accumulates with increasing numbers of wheel load applications on the pavement .Two major phenomena contributing to rutting of asphalt concrete pavements are densification (decrease in
  • 46. 46 volume and hence increase in density) and shear plastic Deformation (Collop et al., 1995). These two phenomena contribute in varying degrees to the permanent deformations in all pavement layers including asphalt concrete surface course, asphalt base course, aggregate base and sub base and sub-grade. Studies on asphalt mixtures indicated that shear deformation rather than densification was The primary rutting mechanism (Highway Research Board, 1962) and (Hofstra et al., 1972). (Eisenmann et al., 1987) also concluded that if the Pavement has been compacted to higher density during construction, their densification during the application of wheel loads is unlikely, and rutting is induced predominantly due To shear flow of the asphalt mixture. Thicker asphalt concrete layers exhibit more permanent deformation within the asphalt Concrete layer, but the amount of permanent deformation does not increase directly with the increasing layer thickness beyond a certain threshold thickness of the asphalt layer. Any increase in the depth of the asphalt layer beyond this threshold will not influence the Total rut depth within the asphalt layer.(Uge and Van de Loo,1974) demonstrated that the rut depth reaches a limiting value for An asphalt concrete layer thickness of 13 cm to 25 cm and any further increase in the depth Has a negligible effect on the total amount of rutting in the asphalt layer. Similar findings were made during the AASHO road test, Highway Research Board (1962). This is due to the decrease in shear stresses at greater depth in the asphalt layers.(Hofstra and Kiomp, 1972) observed during laboratory test track studies on asphalt Pavements that the permanent deformation within the asphalt layer increases relative to the thickness of the asphalt layer. However, by increasing the thickness of the asphalt layer beyond 10 cm. further increases in permanent deformation of the asphalt layer was insignificant. (Hofstra et al., 1972) shows that by increasing the thickness of the asphalt layer from 10 to 20 cm. the increase in permanent deformation is Negligible. However, a significant increase in permanent deformation within the asphalt Layer can be noticed when the layer thickness is increased from 5 to 10 cm. This also strengthens the belief that the larger portion of the total rut depth is contributed by the Asphalt layer near the surface due to high shear stresses under the wheel load. These Results reveal that if the supporting
  • 47. 47 material under the asphalt concrete layer is reasonably stiff, most of the total pavement rutting develops within the asphalt concrete layer(Ce’lard, 1977). Laboratory Test Related to Rutting Wheel Tracking Device Wheel Tracker typically measures the rut, created by repeated passage of a wheel over Prismatic asphalt concrete samples. It will be used to assess the resistance to rutting of theAsphaltic material, under standard defined conditions of load and temperatures. the wheel speed is maintained during the test. The rut resistance can be quantified as the rate of rutting during the test or the rut depth at the conclusion of the test, measured with Linear Variable Displacement Transformers (LVDT) 25mm (min). Slab specimens were prepared in the laboratory for research study. The susceptibility of an asphaltic material to deform is assessed by measuring the rut formed byrepeated passes of a loaded wheel at specified temperatures. The wheel tracking apparatusconsists of loaded wheel which bears on a sample held on a moving table. The moving table reciprocates with simple harmonic motion with a frequency of 26.5passes per minutes (European Standard- EN 13108/12697-22, 2002).
  • 48. 48 Figure 2.8: Wheel Tracker Solid Rubber Tire (After Cooper, 2006) The wheel is fitted with solid rubber tire of outside diameter 200 mm. The tire is a rectangularsection 50 ± 1 mm wide and 10mm to 13 mm thick. The wheel tracker is fitted with atemperature controlled cabinet with a maximum temperature up to 65Co ± 1Co . Square slabspecimens (305x305mm) of asphalt mixes with typical asphalt wearing course thickness of50mm thick, fitted with wheel tracker (WT) table, clamps for securing specimen holders. Mixes were evaluated under a loaded wheel (700 ± 20 N) tracked with simple harmonic motion through a distance of 305mm on specimens under specified conditions i.e. 53 passes perminute at temperatures 25Co , 40Co and 55Co (European Standard- EN 13108/12697-22,2002). The operational software run under Windows to start and stop the WT, control speed and acquire deformation and temperature data. An on-screen display provides a continuously updated graph of time versus deformation as shown in Figure 6.3. The test data are stored in a text file for subsequent analysis using a spreadsheet.
  • 49. 49 2.11 Other Test Related to Rutting 2.11.1 Hamburg Wheel-Tracking Device The HWTD, was developed by Helmut-Wind incorporated of Hamburg, Germany (Aschenbrener, 1995).it is used as a specification requirement for some of the most traveled roadways in Germany to evaluate rutting and stripping. Tests within the HWTD are conducted on a slab that is 260 mm wide,320 mm long, and typically 40 mm high( 10.2 in x 12.6 in x 1.6 in). Figure 2.9: Hamburg Wheel-Tracking device (Hans, 2006)
  • 50. 50 2.12 Summary (i) The warm mix asphalt is an alternative solution to the problem of global warming and preservation to the economy of the country. It has significant benefits to the working environment because it’s significantly reduced the emission and heat from the mix. (ii) As compare to HOT, WMA is largely adopted by many countries for their highway constructions. Many technologies and techniques are in-cooperated with WMA to improve its resistance to pavement distress. (iii) The problem with WMA as pointed out is moisture content, because of their preparation at lower temperature as compare to HOT. To overcome the problems of moisture Susceptibility, additives are used. Additives function is to reduce moisture and increase the binder viscosity. (iv) The common pavement distress is cracking, rutting, and stripping. (v) The rutting can be minimized by the use of anti-stripping agents and pavement modifiers. (vi) Hamburg Wheel Tracking Test and other laboratory tests will be used to assess and evaluate the rutting resistance under different loading conditions. (vii) The stripping will be assess and anti-stripping agents namely hydrated lime, Portland cement and PMD effects will be study and its effects on stripping will be evaluate. (viii) The purpose of the study is to enhance the rutting resistance of warm asphalt mixes, and study the effects of Sasobit® . on rutting resistance.
  • 51. 51 CHAPTER 3 METHODOLOGY 3.1 Introduction This research methodology was developed to achieve the aim and objectives of this research. The aim of this study is to evaluate the rutting resistance of warm Mix asphalt incorporating anti-stripping agents namely Sasobit® .The first step will be the background information and study of the proposed research, to explore in detail the information before going to the actual laboratory tests. After the primary data search the next step will be laboratory tests and data evaluation. 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 laborites’ tests are starting from selection of proper materials for warm asphalt mix design. After selection of materials the material test for bitumen, aggregates. Then the addition of additives and anti-stripping agents to improve the asphalt mix viscosity at lower temperature. The wheel tracking test will be conducted under different loading and temperature, and the rutting resistance will be noticed.
  • 52. 52 Figure 3.1: Research methodology flow chart Material Preparation (Aggregate, asphalt binder) Aggregate Properties Evaluation  Aggregate Impact Value  Flakiness and Elongation Index Test  Site analysis Material Evaluation (Aggregate and asphalt binder) Asphalt Binder Properties Evaluation  Softening Test  Penetration Test  Rational viscosity Test (RV)  Dynamic Shear Rheometer test (DSR) Sample Preparation Anti-Stripping Agents Use  Lime stone  Portland Cement  Pavement Modifier Data and Analysis Discussion and Conclusion. Rutting Evaluation  Wheel tracking test Moisture Sensitivity Test  Moisture sensitivity test (AASHTO T283)
  • 53. 53 3.2 Laboratory tests procedures The study will be conducted base on laboratory testing as the main testing procedure to obtain the required results and estimates. The entire test will be conducted in the highway laboratory. The laboratories tests are divided into several stags begin with the aggregates preparation. Crush aggregate granites will be washed, dried and sieved into a selected size range according to standard specifications (ACW 14) as requirements by the Public Works Department (JKR, 2008). 3.3 Materials selection 3.3.1 Asphalt binder The binder used in this research study is grade PEN 80/100 . Type of asphalt cement binders is classified based on their depth of penetration at Various temperatures. Thebinder classification tests performed include Penetration test (ASTM D5097) and Softening Point test (ASTM D-3461). The asphalt binder selection depends on temperature and traffic loading conditions in the project area. Penetration Grade Bitumen is commonly used in road surfacing, and some industrial applications. 3.3.2 Softening Point The objective of softening test is to determine the softening point of bitumen within the range 30 to 157 º C by means of the Ring-and-Ball apparatus. The procedure of this test is the specimen will be carried out according to ASTM D36 (ASTM, 2005b)
  • 54. 54 procedures, precisely. Dimensioned brass rings and will be maintained at a temperature of not less than 10’C below the expected softening point for at least 30 minutes before the test. Then, the rings and assembly and two ball bearings will be placed in a liquid bath filled to a depth of 105 ± 3mm and the temperature of 5 ± 1’C for 15 minutes will be maintained. 3.3.3 Penetration Test The objective of a penetration test is to examine the consistency of a sample of bitumen by determining the distance in tenths of a millimeter that a standard needle vertically penetrates the bitumen specimen under known conditions of loading, time and temperature. The procedure of this test is the specimen will be prepared in sample containers exactly as specified ASTM D5 (ASTM, 2005c) and placed in a water bath at the prescribed temperature of the test for 1 to 1.5 hours before the test. Next, for normal tests the precisely dimensioned needle, loaded with 100 ± 0.05 grams will be brought to the surface of the specimen at right angles, allowed to penetrate the bitumen for 5 ± 0.1s, while the temperature of the specimen is maintained at 25 ± 0.1’C. The penetration will be measured in tenths of a millimeter (deci-millimeter, dmm). .3.3.4 Rational viscosity test Viscosity is a fundamental characteristic of bitumen that describes the resistance of fluids to flow.The Rotational Viscometer (RV) is used to determine the viscosity of asphalt binders in the high temperature range of manufacturing and construction. The RV test can be conducted at various temperatures, but since manufacturing andconstruction temperatures are fairly similar regardless of the environment, the test is conducted in the range of 120 C to 160 C.
  • 55. 55 The characteristic of bitumen will be tested using a Brookfield Viscometer and will be conducted according to ASTM D4402 (ASTM, 2005d) procedures. According to Asphalt Institute (2007), the ideal laboratory mixing and compaction temperature of asphalt concrete and other hot-mix type using conventional binder are the temperature at which the binder achieves a viscosity of 0.17 ± 0.02 Pa.s and 0.28 ± 0.03 Pa.s, respectively. However,Yildrim et al. (2006) established the ideal mixing and compaction temperatures for asphalt mixes using modified binder at a viscosities equivalent to 0.275 ± 0.03 Pa.s and 0.550 ± 0.06 Pa.s, respectively. 3.4 Dynamic Shear Rheometer In order to resist rutting, an asphalt binder should be stiff and it should be elastic (it should be able to return to its original shape after load deformation).Therefore, the complex shear modulus elastic portion, G*/Sin δ. When rutting is of greatest concern, a minimum value for the elastic component of the complex shear modulus is specified. Intuitively, the higher the G* value, the stiffer the asphalt binder is, and the lower the δ value, the greater the elastic portion of G*. Rutting is basically a cyclic loading phenomenon. With each traffic cycle, work is being done to deform the pavement surface. Part of this work is recovered by the elastic rebound of the pavement surface, while part is dissipated in the form of permanent deformation, heat, cracking and crack propagation. Therefore, in order to minimize rutting, the amount of work dissipated per loading cycle should be minimized. The dynamic shear rheometer (DSR) is used to characterize the viscous and elastic behavior of asphalt binders at medium to high temperatures. The test will be conducted in accordance to super pave requirements (Asphalt institute, 2007) to characterize bitumen rheology, both viscosity and elastic behavior, by measuring the complex modulus (G*) and phase angle (δ) of the asphalt binders at different temperatures. G* is considered as the total resistance of the binder to deformation when repeatedly sheared, whereas δ is an indicator of the relative amounts of recoverable and
  • 56. 56 non-recoverable deformation (Roberts et al.,1996).The basic DSR test uses a thin asphalt binder sample sandwiched between two circular plates. The lower plate is fixed while the upper plate oscillates back and forth across the sample at 10 rad/sec (1.59 Hz) to create a shearing action. DSR tests are conducted on un-agedand aged asphalt binder samples. A frequency of oscillates that simulates the shearing stress corresponding to traffic speed about 100km/h. The test is largely software controlled. 3.5 Aggregates Aggregates are the main constituent of asphalt mixture. Aggregates used in the asphalt mixture include various particle sizes which arecoarse and fine aggregates. The selection of aggregates is necessary because it affects the performance of WMA mixes. The propose of this study is to identify and determine the properties of different types of aggregates, so aggregate have to be sieved to achieve a better gradation of coarse and fine aggregate. Several size of sieve is needed to be use in order to get the size of aggregate required such as size of 20mm, 14mm, 10mm, 5mm, 3.35mm, 1.18mm, 0.425mm, 0.15mm, 0.075mm,. Then aggregates are mixed together following the required total weight of each size of the aggregate to prepare sample of bituminous mixture. 3.5.1 Aggregates impact value test The aggregate impact value gives a relation measure of the resistance of an aggregate to sudden shock or impact, which in some aggregates differs from their resistance to a slowly applied compressive load refer to MS 30: Part 10 (MS, 1995).The objective to determine the aggregate impact value in the laboratory. Firstly, the aggregate will sieve
  • 57. 57 and will obtain in the portion passing 12.5mm and will be retained on 10mm sieve. The aggregate will be washed and dry at a constant temperature of 105’C to 110’C and then the aggregate will be cooled. The aggregate will be filled with the cylindrical measure in 3 layers, tapping each layer 25 times with the tamping rod. The surface tamping road will be level using the straight edge. The aggregate will be taking the weight and will be used for the duplicate test on the same material. The aggregate from the cylindrical will be transferred to the cup in 3 layers and will be compact each layer by tamping in 25 strokes with the tamping road. The hammer will be released in fall freely on the aggregate. The test sample is subjected to a total of 15 blows. The aggregate sample will be removed from the cup and sieve through a 2.36 mm sieve. The fraction passing the sieve will be taking the weight. 3.5.2 Sieve analysis test Sieve Analysis (ASTM C136) is a procedure to analyze the grading of a stock of aggregate. This is to ensure that the proportions of aggregate that are going to be used in the mixture are within or fulfill the limitation of the JKR/SPJ/2008 specification. The grading of the aggregate that used is ACW 14 (Asphaltic Concrete Wearing). Table below show the gradation limit for ACW 14 according to JKR/SPJ/2008. Table 3.1 Gradation limit for ACW 14 according to JKR/SPJ/2008 B.S.Sieve Size (mm) % Passing By Weight (gram) 20 100 14 90-100 10 76-86 5.0 50-62 3.35 40-54 1.18 18-34 0.425 12-24 0.150 6-14 0.075 4-8
  • 58. 58 3.5.3 Flakiness and Elongation Index Test The particles shape of aggregates is determined by the percentage of flakey and elongated particles contained in it. The presence of flakey and elongated particles is considered undesirable as they may cause inherent weakness with possibilities of breaking down under heavy loads. The angularity number is considered important for various types of mixes. The flakiness and elongation index test will carried out in accordance with procedures stated in MS 30:Part 5 (MS, 1995) and MS 30:Part 3 (MS, 1995), respectively. The particle shape of aggregates is determined by the percentages of flaky and elongation particles. Flaky and elongation particles are considered undesirable as they cause weakness of the pavement. The objective of this test is to determine the flakiness and elongation indices of the given aggregate sample. Generally, the sieve sample will take the weight every each of the individual size fractions that retained on these sieve, other than the 63.0 mm sieve and will be stored in separated trays marked with their size. Gauge each fraction from the respective slots in the thickness gauge will be the weight which pass through the slot. 3.6 Sample Preparation Crush aggregate granites will be washed, dried and sieved into a selected size range according to standard specification (ACW 14) as requirements by the Public Works Department (JKR, 2008). Conventional bitumen 80/100 penetration grade will be used for the whole specimen preparations as well as Ordinary Portland Cement and Pavement Modifier.The crush aggregate will be supplied by Quarry Minyak Beku, Sdn. Bhd. while Sasobit® will be supplied by Asa Infratech (M) Sdn. Bhd.
  • 59. 59 In this study, two asphalt mix designs will be evaluated consisting of 2% Ordinary Portland cement and 2% Pavement modifier, respectively. The different of Sasobit® contents will used by mass of bitumen.The effects of Sasobit® blended with bitumen at different temperature were evaluated. The bitumen will be heated at 1200 C and pour into the container. A propeller mixer will be used to blend the Sasobit® with binder at 150°C. The asphalt binders will be tested for viscosity. Each material will be through several tests to ensure conformity to the specifications. A sample of HMA mixtures is prepared as a control sample. 3.7 Warm Mix Asphalt addtive To characterize the rutting performance of warm mix asphaltic mixtures, 2 different samples are needed, which is with or without WMA additive for further inductive reasoning with respect to more general inference. The Sasobit® content will be used 1% and 2% respectively based on earlier studies conducted by Biro et al, (2009) and Lee et al, (2008). The additives are not involved in foaming technology/mechanism. The additives are in viscous liquid state at the room temperature. The warm additives were selected in such a way that the characterization of the products from these categories (chemical) could be possibly investigated. 3.8 Design of binder content In binder determination, the method that will be used is Marshall test. The Marshall method seeks to select the binder content at a desired density that satisfies minimum stability and range of flow values. The Marshall test was conducted in accordance with BS 598:1985 as shown in Table 3.3. The procedure to obtain the stability and flow were started with conditioning the specimen in a 60°C water bath for 30-40 minutes. The
  • 60. 60 Marshall stability and flow test provides the performance prediction measure for the Marshall mix design method. The testing was conducted using a Marshall testing Machine. Table 3.2Standard specification test for bituminous mixture Laboratory Test Standard Test Objective Marshall Test ASTM D1559 To determine the optimum bitumen content (OBC). The mix design conduct with the coarse aggregate, fine aggregate, and the filler material should be proportioned. The quantity of the mix is taken so as to produce compacted bituminous mix specimens of thickness 63.5 mm approximately. 1200 gm of aggregates and filler are required to produce the desired thickness. The aggregates will heated to a temperature of 175° to 190°C the compaction mold assembly and rammer are cleaned and kept pre-heated to a temperature of 100°C to 145°C. The bitumen are heated to a temperature of 121°C to 138°C and the required amount of the first trial of bitumen is added to the heated aggregate and thoroughly mixed. The mix is placed in a mold and compacted with 75 numbers of blows . The sample is taken out of the mold after a few minutes using sample extractor. According to ACW 14, the design of bitumen content ranged from 4.0% to 6.0%. 3.9 Moisture Susceptibility test Currently tensile strength Ratio method (TSR) is widely used and accepted or AASHTO T283 is used to determine moisture susceptibility of WMA mix. the asphalt institute (1987),reported that AASHTO T283 test method is better than the immersion- compression test (ASTM D1075) or Marshall-immersion method because these two methods failed to effectively predict the moisture susceptibility of the mixtures. Approximately 1200g batch weight was used to prepare specimen of 100 mm in Diameter and 71 ±3 mm in height. Initially, the trial and error method was practiced at
  • 61. 61 the beginning to determine the appropriate weight of specimens at the desired air voids level. The number of gyrations needed to prepare the specimens was also determined after several trials using the SGC. To determine moisture susceptibility, all WMA specimens were compacted to approximately 7±0.5% air voids at optimum binder content that allows for the air voids of the specimen to be measured according to AASHTO T166. Any specimens outside the specified air voids range were not considered. For each specimen, the bulk specific gravity was determined and percent air voids were calculated as follows: Air voids (%) = 100 x (1-A/B) Where, A = bulk specific gravity B= theoretical maximum specific gravity Compacted specimens were divided into two subsets each having the same average Air voids, the dry subset (control group) was placed in a plastic bag submerged in Water bath and conditioned for two hours at 25°C prior to testing. The saturated specimens that are within the specification were then placed in a freezer at -18 Co for 24 hours. Then placed in a water bath at 60°C for another 24 hours and finally at 25"C two hours before testing. 3.10 Rutting tests The tests used to determine the rutting potential of WMA is Wheel tracking test.Wheel tracking test is used to assess the resistance to rutting of asphaltic materials under conditions which stimulate the effect of traffic.A loaded wheel tracks a sample under specified conditions of load,speed and temperature while the developement of the rut profile is monitured continuosly during the test.
  • 62. 62 3.10.1 Wheel tracking test Laboratory scale test is normally conducted at the temperature of 45o C and 60o C, with the load of 300 N and 700N applied by the wheel to the surface of asphalt material.The performance of the material under wheel tracking test is assessed by measuuring the rut depth after a standard number of tracking.The wheel tracking machine was contrived for testing a cylindrical sample,150mm in diameter and 65mm of depth, manufactured using a gyratory compactor.A standard air voids content (5%) is used when comparing different mixes. The tyre have an outer diameter of 20mm and cross section of 50x10-13 mm.The tyre travel for distance of 230mm. The rate of tracking is 42 passes/minute. For the test duration,the test is continues until a rut depth of 15mm is achieved or for 45 minutes,whichever that comes first.Results obtained by plotted vertical displacement against time. 3.10.2 Compaction of specimen for wheel tracking test Sample dimension of 150mm in diameter and 65mm height compacted using Super pave Gyratory Compactor. Super pave Gyratory Compactor consists of these components such as reaction frame, rotating base, motor, loading system, loading ram pressure gauge, height measuring and recordation system, mold, base plate and specimen extruding device. A loading mechanism presses against the reaction frame and applies a load to the loading ram to produce a 600-kPa compaction pressure on the specimen. A pressure gauge measures the ram loading to maintain constant pressure during compaction. TheSuper pave Gyratory Compactor mold has an inside diameter of 150mm and a base plate in the bottom of the mold provides confinement during compaction. The Super pave Gyratory Compactor base rotates at constant rate of 30 revolutions per minute during compaction, with the mold positioned at a compaction
  • 63. 63 angle of 1.25 degrees. Specimens height measurement is an important function of the Super pave Gyratory Compactor Specimen density can be estimated during compaction by knowing the mass of material placed in the mold, the inside diameter of the mold, and the specimen height. Height is measured by recording the position of the ram throughout the test. 3.11 Analysis and discussion In this study, the performance of WMA by using anti-stripping agents will be analyzed. The performance graph and bar chart will be used to analyze the performance of each specimen under different concentration of pavement modifier in terms of rut depth. The actual test data will be summarized in result and discussion section. The result will be analyzed the effectiveness of rut potential of asphalt mixes between neat binder and modified binder.
  • 64. 64 CHAPTER 4 EXPECTED RESULTS 4.1 Expected Result. The two types of asphalt currently widely used are porous and dense asphalt, the dense asphalt structure provide less water penetration and high resistance to impact tire loading, andincreased road safety in wet weather. But the problem with asphalt is the production of greenhouse gases.In recent years, the asphalt industry has been exploring alternatives to reduce the greenhouse gases and environmental pollution. The WMA to a large extent improves the greenhouse emission from asphalt production. The problem with WMA is the rutting and other pavement related distress as extensive as compare to HMA. The use of anti-stripping agents has shown remarkable improvement in rutting resistance and lowers the emission of toxic and hazardous gases. The rutting and other pavement distress affects the service life of pavement and makes it undesirable for future adaptation. Therefore,this study aims to improve the resistance of warm mix
  • 65. 65 asphalt incorporating anti-stripping agents, and increase the service life of pavement to make it more economically attractiveand applicable. In this study detail tests will be carried out for aggregates and binder and their properties will be evaluate for rutting resistance. Next, the effect of anti-stripping agents will be investigated on rutting resistance of warm mix asphalt. Finally the results will be evaluated in statistical and graphical forms to enhance the rutting resistance with future improvements.
  • 66. 66 REFERENCES Add. (2011). doi:10.1007/SpringerReference_7709 additives. (n.d.). Ahmed, F., Kridan, M., Arshad, A. K., Yusof, M., & Rahman, A. (2011). THE EFFECT OF WARM MIX ASPHALT ADDITIVE ( SASOBIT ® ) ON DETERMINATION OF OPTIMUM BITUMEN CONTENT, 6(March), 400–406. Aksoy, A., ??Amlioglu, K., Tayfur, S., & ??Zen, H. (2005). Effects of various additives on the moisture damage sensitivity of asphalt mixtures. Construction and Building Materials, 19(1), 11–18. doi:10.1016/j.conbuildmat.2004.05.003 anti-stripping agents. (n.d.). Aragão, F. T. S., Lee, J., Kim, Y.-R., & Karki, P. (2010). Material-specific effects of hydrated lime on the properties and performance behavior of asphalt mixtures and asphaltic pavements. Construction and Building Materials, 24(4), 538–544. doi:10.1016/j.conbuildmat.2009.10.005 Broadsword, B. A. L., & Ap, L. (2011). Introducing Warm Mix Asphalt, (May), 1–2. Brockenbrough, R. L., Editor, P. E., York, N., San, C., Lisbon, F., Madrid, L., … Seoul, J. (n.d.). No Title. Capitão, S. D., Picado-Santos, L. G., & Martinho, F. (2012). Pavement engineering materials: Review on the use of warm-mix asphalt. Construction and Building Materials, 36, 1016–1024. doi:10.1016/j.conbuildmat.2012.06.038
  • 67. 67 Characterization of Warm Mix Asphalt (WMA) performance in differe.pdf. (n.d.). Chen, T. F. (2009). UNIVERSITI TEKNOLOGI MALAYSIA DECLARATION OF THESIS / UNDERGRADUATE PROJECT PAPER AND : EVALUATION OF RUTTING PERFORMANCE i ON HOT MIX ASPHALT MODIFIED WITH RESTRICTED “ I / We * hereby declare that I / we * have read this thesis and in quality for the award of the degree of Bachelor / Master / Engineering Doctorate / Doctor of Philosophy of Civil Engineering Signature Name of Supervisor Date, (April). Common definition about pavements and asphalt mixtures. (n.d.). EFFECTS OF WARM ASPHALT ADDITIVES ON ASPHALT BINDER AND. (2008), (May). Engineering, H. (n.d.). Highway engineering. Engineering, T., Group, D., & Institutions, O. F. (2013). Determination of aggregate crushing value 1., (1). Evaluation of Moisture Damage in Warm Mix Asphalt Containing Recy (1).pdf. (n.d.). Freitas, E., & Pereira, P. (n.d.). Assessment of Top-Down Cracking Causes in Asphalt Pavements. Garrison, M. (n.d.). No Title, 1–12. Glueckert, T. (2012). IMPACTS OF WMA ADDITIVES ON RUTTING RESISTANCE AND MOISTURE, (May). Golalipour, A., Jamshidi, E., Niazi, Y., Afsharikia, Z., & Khadem, M. (2012). Effect of Aggregate Gradation on Rutting of Asphalt Pavements. Procedia - Social and Behavioral Sciences, 53, 440–449. doi:10.1016/j.sbspro.2012.09.895 Highway_and_Traffic_Engineering.pdf. (n.d.). Hill, B. (2011). PERFORMANCE EVALUATION OF WARM MIX ASPHALT MIXTURES INCORPORATING RECLAIMED ASPHALT PAVEMENT BY. Importance of Asphalt Binder Properties on Rut Resistance of Asphalt Mixture by Amir Arshadi A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science ( CIVIL & ENVIRONMENTAL ENGINEERING ) at the UNIVERSITY OF WISCONSIN-MADISON. (2013). IRC-58-1988.pdf. (n.d.).
  • 68. 68 Jointed, P., Pavements, R., Irc, H., & Roads, C. C. (2008). roads for Rural Roads Types of Pavements. Jones, D., Wu, R., Tsai, B., & Harvey, J. T. (2011). Warm-Mix Asphalt Study: Test Track Construction and First-Level Analysis of Phase 3a HVS and Laboratory Testing (Rubberized Asphalt, Mix Design #1), 0003. Kavussi, a., Qorbani, M., Khodaii, a., & Haghshenas, H. F. (2014). Moisture susceptibility of warm mix asphalt: A statistical analysis of the laboratory testing results. Construction and Building Materials, 52, 511–517. doi:10.1016/j.conbuildmat.2013.10.073 Khan, S., Nagabhushana, M. N., Tiwari, D., & Jain, P. K. (2013). Rutting in Flexible Pavement: An Approach of Evaluation with Accelerated Pavement Testing Facility. Procedia - Social and Behavioral Sciences, 104(m), 149–157. doi:10.1016/j.sbspro.2013.11.107 Khodaii, a., Kazemi Tehrani, H., & Haghshenas, H. F. (2012). Hydrated lime effect on moisture susceptibility of warm mix asphalt. Construction and Building Materials, 36, 165–170. doi:10.1016/j.conbuildmat.2012.04.073 Mallick, R. B., Advisor, M., Tao, M., & El-korchi, T. (2011). Investigation of Effects of Moisture Susceptibility of Warm Mix Asphalt ( WMA ) Mixes on Dynamic Modulus and Field Performance by Submitted to the Faculty of the in partial fulfillment of the requirements for the Degree of Master of Science in. Manual, E. (n.d.). Flexible Pavements for Roads , Streets , Walks and Open Storage Areas Mobilization Construction DEPARTMENT OF THE ARMY. Mashaan, N. S., & Karim, M. R. (2013). Evaluation of Permanent Deformation of CRM-Reinforced SMA and Its Correlation with Dynamic Stiffness and Dynamic Creep, 2013. Miljkovic, M., & Radenberg, M. (2011). Rutting mechanisms and advanced laboratory testing of asphalt mixtures resistance against permanent deformation. Facta Universitatis - Series: Architecture and Civil Engineering, 9(3), 407–417. doi:10.2298/FUACE1103407M Ncat, T., & Three, E. G. (2004). 3.2.3 Field Trials, 18–85. No Title. (n.d.). No Title. (2011), 1–71. Of, I., Condition, S., Rutting, O. N., An, F. P.-, & Investigation, E. (2013). International journal of.
  • 69. 69 Paper, P. (2010). The use of Warm Mix Asphalt, (January), 1–13. Rashwan, M. H. (2012). Characterization of Warm Mix Asphalt ( WMA ) performance in different asphalt applications. Resistance, R., Filler, O. F., Bituminous, M., & Surfaces, C. (2013). Technology (ijciet ), 250–257. Sengul, C. E., Aksoy, A., Iskender, E., & Ozen, H. (2012). Hydrated lime treatment of asphalt concrete to increase permanent deformation resistance. Construction and Building Materials, 30, 139–148. doi:10.1016/j.conbuildmat.2011.12.031 Shami, E. H. I., & Hall, E. J. I. M. (n.d.). RUTTING OF ASPHALT CONCRETE PAVEMENTS, (226). Soleimani, A. (2009). USE OF DYNAMIC PHASE ANGLE AND COMPLEX MODULUS FOR THE LOW TEMPERATURE PERFORMANCE GRADING OF. Strong, V., Expensive, L., Strength, M., Material, N., & Sensitive, M. (2006). Geotechnical Aspects of Pavements, (132040). Tong-jiang, F. A. N. (2010). Rut Resistance Behavior of Pavement Structures Combined by the Different Asphalt Mixtures, (cm), 4–8. Tonias, D. E. (1999). Ighway ngineering, (C), 1–64. Tsai, J., & Lai, J. (2010). Evaluating Constructability and Properties of Warm Mix Asphalt Submitted to The Office of Materials and Research Prepared By, (June). WaterPenetratePic_1. (n.d.). Xiao, F., & Amirkhanian, S. N. (2010). Effects of liquid antistrip additives on rheology and moisture susceptibility of water bearing warm mixtures. Construction and Building Materials, 24(9), 1649–1655. doi:10.1016/j.conbuildmat.2010.02.027 Xiao, F., Ph, D., Zhao, W., Gandhi, T., Ph, D., Amirkhanian, S. N., … Asce, M. (2010). Influence of Antistripping Additives on Moisture Susceptibility of Warm Mix Asphalt Mixtures, (October), 1047–1055. Xiao, F., Punith, V. S., & Putman, B. J. (2012). Effect of Compaction Temperature on Rutting and Moisture Resistance of Foamed Warm Mix Asphalt Mixtures. Journal of Materials in Civil Engineering, 673(September), 120824030841004. doi:10.1061/(ASCE)MT.1943-5533.0000664.
  • 70. 70 Xu, T., & Huang, X. (2012). Investigation into causes of in-place rutting in asphalt pavement. Construction and Building Materials, 28(1), 525–530. doi:10.1016/j.conbuildmat.2011.09.007 Zaumanis, M. (n.d.). W m a i. Zhang, J. (2010). Effects of Warm-mix Asphalt Additives on Asphalt Mixture Characteristics and Pavement Performance.