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rutting resistance of warm mix asphalt incorporating sasobit
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1 EVALUATION OF RUTTING IN WARM MIX ASPHALT INCOPORATING ANTI-STRIPING AGENT AT UNIVERSITI TUN HUSSEIN ONN MALAYSIA AHMADZEB GF130152 DR. MUHAMMAD YUSRI Faculty of Civil and Environmental Engineering University Tun Hussein Onn Malaysia
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Page 1: Rutting resistance in warm mix asphalt

1

EVALUATION OF RUTTING IN WARM MIX ASPHALT INCOPORATING ANTI-STRIPING AGENT

AT UNIVERSITI TUN HUSSEIN ONN MALAYSIA

AHMADZEBGF130152

DR. MUHAMMAD YUSRI

Faculty of Civil and Environmental EngineeringUniversity Tun Hussein Onn Malaysia

JUN 2014

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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

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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

2.2.1.1 Environmental Benefit 19

2.2.1.2 Paving Benefit 22

2.2.1.3 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

2.4.2.1

2.4.2.2

Types and Grades of Bitumen

Characteristics of Bitumen

29

29

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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

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

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2.10.5.1 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

3.5.3 Flakiness and Elongation Index Test

57

58

58

59

3.6 Sample Preparation 60

3.7 Warm mix asphalt additive 60

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3.8

3.9

3.10

Design of binder content

Moisture Susceptibility test

Rutting Tests

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

LIST OF TABLES

2.1 Recommended amount of some available WMA 18

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additive (Oliveira j, et al, 2010).

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

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

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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

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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 0C has led to

the following temperature based classification of asphalt mixes: Hot Mix Asphalt or

HMA (190-150oC);Warm Mix Asphalt or WMA(100-140oC);Half-Warm Mix Asphalt

or HWMA (60-100OC)(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

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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 20-40oC 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).

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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.

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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

)ToevaluateandcomparethecharacterizationofruttingPotentialofasphaltmixturesaddedwit

hSasobit®.

(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.

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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.

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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

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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

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temperature decrease is around 30C for the first case and can attain

up to 80 C for the second case (World Road Association, 2008).

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

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the wetting of aggregates by bitumen without changing considerably

the binder performance (Silva and Almeida, 2009).

Table 2.1: Recommended amount of some available WMA additive (Oliveira, et al, 2010).

Additive Additive rate range Typical additive rateOrganic 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 binderSonne warmix 0.5-1.5% by weight of

total binder 0.75% -maximum recommender for

unmodified virgin mixesChemical 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------

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.

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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

2.2.1.1 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 -foamSulfur Dioxide 17.60% --- 81% N/A

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Carbon 3.20% 18% 46% 31%Carbon monoxides

N/A N/A 63% 29%

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

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)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

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).

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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 23SO2 N/A 35 N/A 18

VOC N/A 50 N/A 19

CO 28.5 10-30 N/A N/ANOX 61.5 60-70 N/A 18*

Dust 54 N/A N/A N/A

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2.2.1.2 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

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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

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.

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2.2.1.3 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

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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.

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

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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

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

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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)

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

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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

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

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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.

2.4.2.1 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

2.4.2.2 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:

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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

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

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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

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

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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 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.

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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

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

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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.

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

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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.

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-

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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. 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,

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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.

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).

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(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

2.8 Pavement modifier

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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

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

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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 WMA. On one hand, given the limited

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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

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failure. Typically the loss of bond begins at the bottom of the

pavement layer and progresses upward (Hossain, 2009).

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

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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 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)

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Figure 2.6: Determination of rutting depth (highway association, 1999)

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)

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(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).

(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).

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(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).

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.

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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.

2.10.3 Factors Affecting Rutting

Table2.6:(Kandahar, et al, 2003)

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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 volume and hence

increase in density) and shear plastic Deformation (Collop et al.,

1995).

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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

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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 material under the asphalt concrete layer is

reasonably stiff, most of the total pavement rutting develops within

the asphalt concrete layer(Ce’lard, 1977).

2.10.5.1 Laboratory Test Related to Rutting

2.10.5.2 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

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motion with a frequency of 26.5passes per minutes (European

Standard- EN 13108/12697-22, 2002).

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.

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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)

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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.

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(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.

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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.

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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)

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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)

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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.

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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

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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

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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 10014 90-10010 76-865.0 50-623.35 40-541.18 18-340.425 12-240.150 6-140.075 4-8

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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.

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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 120 0C

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

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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

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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 C o 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.

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3.10.1 Wheel tracking test

Laboratory scale test is normally conducted at the temperature of 45oC and 60oC, 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 -13mm.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

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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.

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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

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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.

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