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CHAPTER 1

INTRODUCTION

1.1 Background of study

The deterioration of surface roads is defined by the damage type of its condition of the

surface over time. The distress such as permanent deformation, cracking and

disintegration is classified as pavement surface defects. Flexible pavement distress modes

normally considered in the flexible pavement analysis and design is fatigue cracking,

rutting and low temperature cracking (Thompson and Nauman, n.d.). In this case study,

the focus is on rutting or permanent deformation because rutting is one of the common

pavement distresses happen in Malaysia which lead to lower riding quality for road users

and high maintenance costs. It describes that permanent deformation or rutting happens

as a consequence of continuous loading including heavy load which lead to progressive

accumulation of permanent deformation under continuous tire pressure. Rutting happened

in the form of longitudinal depression across the wheel path due to the continuous

application of axle loading.

The factors that contribute to the rutting are coming from the excessive traffic

consolidation in the upper layer of the pavement, plastic deformation due to the

inadequate mixture stability and also instability caused by stripping of asphalt binder

below the riding surface of the pavement (Ahmad et. al, 2011). It also stated that increase

in temperature will result in rutting increases even though the traffic loading is under

control and stability in HMA mixtures provided higher resistance against deformation

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process under repetitive loading ( Hafeez et.al, 2010). In order to limit the rut depth at

the acceptable levels, careful attention must be made in surface layers and the subgrade.

The polymer modified binder in asphalt has been shown in improving the strength and

performance of the HMA pavement. Hence, binders such as latex and polyacrylate have

been selected in this case study to be used with Hot Mix Asphalt as a binder. The

comparison between modified asphalt and conventional asphalt also been made to see

their rutting performance. There are four tests commonly used in monitoring rutting

resistance of asphalt mixture such as repeated-load creep test, wheel tracking test, static

creep test, indirect tensile test and Simple Performance Test (SPT).

Many methods could be used in designing HMA mix, and the old methods are Marshall

and Hveem methods where these methods are used in the early 1940s until mid-1990s.

Research done by the Strategic Highway Research Program (SHRP) on asphalt binder

and asphalt mixture has introduced the new method called Superpave (Superior

Performing Asphalt Pavement). The Superpave Mix Design Method consist of a method

for specifying mineral aggregates and asphalt binders, mixing design for asphalt and a

procedure for analyzing and predicting the performance of the pavement. A major

difference between Superpave mix design and other design methods, such as the Marshall

ad Hveem methods, is that the Superpave mix design method mainly uses performance-

based and performance-related characteristics as the selection criteria for the mix design

(Garber and Hoel, 2010)

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1.2 Problem statement

In recent years, the capacity on road increase since the increasing of vehicle ownership

and development of world transportation. This kind of situation may lead to higher traffic

volumes, traffic loads and tire pressure. These factors will increase pavement deformation

such as the rutting. In Malaysia, permanent deformation or rutting is a failure that usually

happens on flexible pavement. Rutting exists when the interlocking between aggregate

and bitumen not really strong and happen in the form of longitudinal depression in wheel

path. Another possible factor that causes rutting is improper mix design like the excessive

asphalt content and an insufficient amount of aggregate particles in mixtures. The

presence of rutting could reduce the serviceability life of the flexible HMA pavement and

lead to certain safety risks as well. Furthermore, rut can lead to car accidents because it

tends to pull a vehicle towards the rutted track as it is steered across the rut and it is also

may cause the hydroplaning of the vehicle during rainy day as water filled up the rut.

As road consumer, this study is significant in the sense of obtaining good quality of

pavement which provided long term road serviceability. It is necessary to provide

pavement which has good characteristics in term of durability, strength, moisture content

and air void that can resist the formation of surface deformation. There are two principle

solutions to construct a more durable pavement; first by applying a thicker asphalt

pavement which will increases the construction cost and secondly making an asphalt

mixture with modified characteristics (Moghaddam et.al., 2011). There are several

actions can be done in improving the HMA mixtures. One of action is using additives

such as polymer modified binder in hot mix asphalt to increase durability of pavement

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structures because additives have abilities to captivate amount of distress imposed by a

continuous heavy traffic load. The aim of this study is to evaluate the rutting performance

on the HMA mix design using latex and polyacrylate thus, to determine the most suitable

modified binder to be used in order to minimize the rutting resistance on HMA pavement.

This study shows comparisons between three types of polymer modified binder on Hot

Mix Asphalt by using Superpave Design Method and evaluation of rutting performance

on those mixes.

1.3 Objectives

The main objective of this study is to evaluate the rutting performance on hot mix

asphalt using polymer modified binder. To achieve this aim, the following secondary

objectives must be carried out:

i. To determine the rutting performance of Hot Mix Asphalt on Superpave mix

design using unmodified and polymer modified binder.

ii. To compare the rutting performance of Hot Mix Asphalt on Superpave Mixtures

on unmodified and polymer modified binder.

1.4 Significant of Study

The total volume of vehicles on the road keeps increasing every year which cause the

pavement deformation such as rutting also increases. The existence of rutting is

dangerous for road user since it accumulates water in the wheel path and this may lead to

accidents and hydroplaning. Thus, it is necessary to improve pavement quality that can

minimize pavement problems such as pavement deformation, cracking and surface

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defects. It is also important to extend the service life of the road pavement by minimizing

the rut depth and this can be done by improving the performance of asphalt mixture. The

usage of modified binder and non-modified binder in HMA mixture bring a huge impact

on performance of hot mix asphalt.So, the relationship between binder characteristics and

mix results were evaluated to see the binder performance in term of rutting.

From this study, the performance of rutting using control, latex and polyacrylate as a

binder on hot mix asphalt is observed through Asphalt Pavement Analyzer (APA)

machine.

1.5 Scope of Work

The focus of the study is to evaluate the rutting performance of polymer modified binder

in hot mix asphalt using Superpave Design Method through Asphalt Pavement Analyzer

machine. The comparison between modified asphalt and non-modified asphalt as binder

has been made to identify if the modified asphalt capable to strengthen the pavement

sample in term of rut resistance. In addition, the selection of suitable modified binder

against rutting can be done in this study. The specification used in preparing HMA

sample is Superpave mix design with NMAS 19mm. In this study there are 2 types of

polymer modified binder used which are latex and polyacrylate. The percentage of

polymer modified binder used in hot mix asphalt was 8% for latex and 6% for

polyacylates which these data are obtained from previous research work done by Atikah,

2013. The aggregates used in mix design is obtained from Blacktop Quarry in Jalan

Templer, Rawang, Selangor. The binder used is penetration grade 80/100 where it is

obtained from Port Klang. The performance of rutting on hot mix asphalt was monitor

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through Asphalt Pavement Analyzer machine. In addition, the scope of the study also

covers the following:

i. Desk study.

ii. Materials selection for aggregates and binders.

iii. To compact and test the HMA mixtures trial blends using the Superpave Gyrator

Compactor device.

iv. Evaluation of rutting performance based on the compiled final design HMA

mixtures using the Asphalt Pavement Analyzer machine.

v. Data analysis and result.

The general outline procedure of study was illustrated as shown in Figure 1.1.

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Figure 1.1: The Outline Procedure of the Research Study (HMA using Superpave method

and Asphalt Pavement Analyzer to evaluate the rutting performance)

Objective of the research

Literature review

Selection of material

(Aggregates and Asphalt Binder)

Preparation of HMA mix design sample at 7±0.5%

air void

Conclusion

Evaluation of Rutting Performance on the final compiled of Design Asphalt

Mixture using Asphalt Pavement Analyzer (APA) machine

Data Analysis and Result

Report Submission and Presentation

Achieved

7±0.5% air

void?

No

Yes

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CHAPTER 2

LITERATURE REVIEW

2.1 Introduction

In the late 1950’s, test on the rigid and flexible pavement in Ottawa, Illinois was

conducted by AASHO (American Association of State Highway Officials) to determine

and identify how traffic can contribute to the deterioration of highway pavements.

Through the information and data obtained, knowledge of designing pavement structure,

pavement performance, load equivalencies and climate effects could be improve and

expand. The results that obtained from the AASHO road test were used to develop design

guides of structural pavement including the AASHTO Guide for the Design of Pavement

Structures and develop empirical equations and calculations to be used for the design of

pavement structures.

Flexible pavement and rigid pavement are two types of pavement as shown in Figure 2.1.

The scope of this study is focusing on the flexible pavement. The surface of flexible

pavement must be high quality and strong enough in order to resist large axle loads and

high temperature. Thus, flexible pavement is constructed with layers of different

materials that the surface strength increase as move towards the surface (weakest layer on

the bottom and strongest layer at the surface). Traffic load distribution of flexible

pavement depends on the layered system over the subgrade. The layers of a flexible

pavement structure basically consist of hot mix asphalt (HMA) at the pavement surface,

with a stabilized base, base course gravel, and sub base course gravel. In Malaysia the

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common flexible pavement structure normally consists of bitumen pavement, granular

road base, drainage sub-base and the subgrade (Hassan and Sufian, 2008). The design of

pavement structure must according to the Arahan Teknik (Jalan) 5/85 which is derived

from the AASHO Road Test.

Figure 2.1 Flexible and Rigid Pavement Cross Section

2.2 Asphalt

Asphalt mixtures basically formed through the combination of asphalt cement, fine

aggregates, coarse aggregates and other materials, which depend on the type of the

mixtures. There are three types of asphalt mixtures that usually used in pavement

construction which are hot-mix hot-laid asphalt mixture, hot-mix cold-laid asphalt

mixture and cold-mix cold-laid asphalt mixture.

Asphalt is a thermoplastic viscoelastic adhesive which acts as a glue. It softens slowly

and change the physical state from solid to liquid when heated. It is characterized by its

consistency at certain temperatures. Its relevant properties are its workability, strength,

durability, imperviousness and adhesion. Generally, the asphalt properties in term of

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viscosity is should be in specified fluid in order to allow it easy to conduct during the

construction process and process of aggregates coat and wet. To avoid problem such as

fracture and crack the viscosity of asphalt must restrain high temperature exposure so that

it will not permanently deform through heavy traffic load and low pavement temperature.

Factors need to be considered during selection of asphalt penetration grade and types are

the climate of the construction area where the temperature of the atmosphere has to take

into account and type of construction to be applied. Asphalt can be classified into two;

unmodified asphalt and modified asphalt. It is not recommended to use unmodified

asphalt because it has a lower quality of resistance and formation of pavement distress

can be easily formed when repetitive and heavy load is passed through the pavement.

Chemical composition if asphalt also effecting the penetration grade of asphalt and it is

stated that the chemical percentage of pure asphalt is 80 to 88% of carbon (C), 0.5 to 10%

of oxygen (O2), 9 to 11% of hydrogen (H2) and 0 to 1% of Nitrogen (N2) .

2.3 Hot Mix Asphalt

Hot Mix Asphalt (HMA) is a common type of mix that broadly be used all over the

world. Basic materials in HMA are a combination of asphalt binder and aggregates which

is conducted through a specific design method such as Marshall, Hveem and Superpave.

In addition, criteria of selecting the HMA mixtures are based on the different coefficient

(Hafeez et. al, 2010). The special procedure of HMA is it must be heated first before

proceed to the next step. Besides that in HMA mix design asphalt binder and aggregates

are heated together in order to ensure that the asphalt in fluid form and the aggregates is

totally dry during coating the aggregates. The newest method in designing HMA is called

Superpave Mix design method.

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2.3.1 Basic Materials

2.3.1.1 Aggregate

Aggregate is one of the main materials in the industry of construction and

it contribute a large portion in the construction of an asphalt pavement.

American Society Testing Materials (ASTM) had describe aggregates as a

granular or coarse material in the composition of mineral such as crushed

stone, sand and gravel. It can form into compound materials such as

asphalt concrete and Portland cement concrete when it binds together with

a medium like water, bitumen, Portland cement and lime. Furthermore,

aggregate also used in constructing base and sub-base layers for rigid and

flexible pavements.

Aggregate is usually based from mineral composition and it can be either

natural or undergo mechanical process with the purpose of specific

applications. The natural aggregates are usually extracted or taking out

from the large formation of the rock by an open excavation. Basically, it is

categorized into three geologic classification of rock, which are igneous,

metamorphic and sedimentary.

Crushed stone, sand and gravel are three types of the aggregates. Crushed

stone also known as crushed rocks and mostly crushed stone is excavated

from the bedrock. The second type of rock is gravel, it is the result from

the erosion and destruction of bedrock and surficial resources. Gravel also

can be crushed, since it has a large contribution in constructing asphalt

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pavement or bases. The formation of sand is either from the erosion of

bedrock or mechanically crushed.

2.3.1.2 Asphalt Binder

Binder or binder courses describe as a medium which acting as an

intermediate paving courses in Hot Mixed Asphalt (HMA)

pavement.Modified binder such as polymer modified binder are

recommended to improve resistance of asphalt binder against rutting and

thermal cracking (Moghaddam, et al, 2011) Nowadays, the grading of

binder is base on the Performance Graded (PG) system in Superpave

research instead of previously method such as penetration and viscosity

test. Asphalt binders can have significant different characteristics within

the same grading category. Grading is more accurate and there is less

overlap between grades, tests and specifications are intended for asphalt

binders to include both modified and unmodified asphalt cements. Asphalt

binder tests for Superpave performance grading are as follows:

i. Rolling thin film oven;

ii. Pressure aging vessel

iii. Dynamic shear rheometer; and

iv. Bending beam rheometer.

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2.3.1.3 Mineral Filler

Mineral fillers have traditionally been used in asphalt mixtures to fill the

voids between the larger aggregate particles. Generally, the aggregate

material passing the No.200 sieve is referred to as filler. In ASTM D242,

mineral filler is defined as consisting of finely divided mineral matter,

such as rock dust, slag dust, hydrated lime, hydraulic binder, fly ash, loess,

or other suitable mineral matter. Other materials, such as carbon black and

sulfur, have been used primarily to modify asphalt binder properties, but

they do have a role as filler, also. Fillers may be used to:

i. Fill voids and, hence, decrease the optimum asphalt content

ii. Meet specifications for aggregate gradation

iii. Increase stability and strength

iv. Improve the bond between asphalt cement and aggregate

Mineral fillers have been used to largely fill in the voids between the

aggregate particles and to meet specified gradations for HMA.

2.4 Modes of Pavement Distress in Malaysia

2.4.1 Cracking

Through the research work done by Public Works Institute Malaysia (IKRAM)

has stated that the most common failed faces by asphaltic concrete is cracking as

shown in Figure 2.2. The asphaltic concrete road which is constructed for the first

time usually exposed to fatigue and top-down cracking while reflection cracks

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tend to exists on the road that has done resurfacing before on the top cracked

surface (Hassan and Sufian, 2008).

Figure 2.2 Cracking failures that exist on the asphaltic concrete road

2.4.2 Top-down Cracking

In Malaysia, the common grade of asphalt use for asphaltic surface is PEN 80/100

as a binder. The process of making asphaltic concrete acquire heat apply 150 –

170 ˚C during the mixing process between hot aggregates and PEN 80/ 100

asphalt (Hassan and Sufian, 2008). According to JKR, the asphalt tends to

strengthen and become hard at the primary stage of the procedure, in storage,

during the process of mixing and in service. Top-down cracking is referred as the

external (surface) crack downwards propagation which happen when the

hardening process go deeper in the surface crack. Figure 2.3 shows the existence

of top-down cracking on the road.

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Top-down cracking exists on the new constructed asphaltic concrete road due to

the thickness of the bitumen mix 5-10 micron which is thin. In addition, factors

such as improper design method and poor compaction causes higher void content

5 - 8 % during hardening process and lead to cracking existence (Hassan and

Sufian, 2008). Besides, ultra violet exposure and moisture content also contribute

to the distress of the asphaltic concrete road.

Figure 2.3 Top-down Cracking

2.4.3 Reflection Crack

The reflected crack shown in Figure 2.4 is a exist crack where had been reflected

toward the new layer of asphaltic concrete with 40mm overlay thickness in a

relatively short period. The rate of reflection crack depends on the sort of

magnitude and cracking of the surface road bonded to overlay, and the volume of

vehicle passes along the road after the construction (Hassan and Sufian, 2008).

Based on the research study, the 40 mm thickness overlays of asphaltic concrete

are unsuitable for rehabilitation of the asphaltic concrete road.

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Figure 2.4 Reflection Crack

2.5 Rutting

Rutting is dangerous surface distress for road user where it causes accumulation of

surface water; hence it increases the possibility of hydroplaning and skidding (Hassan

and Sufian, 2008). Water that accumulates on the pavement distress during rain will

increase the water infiltration rate into the pavement layer and the existence of

deformation will cause the vehicle to lost control especially during lane changes which

both of these factors is dangerous for road users. Rutting also defined as longitudinal

cracking in road pavement where the presence of rutting will bring uncomfortable in

driving comfort for road user and affects safety and health. Rehabilitation is one of the

ways to overcome the permanent deformation problem and it must continuously apply on

the road after the road reach its service life. Figure 2.5 shows pictures of permanent

deformation or rutting.

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Figure 2.5 Permanent deformations or rutting

2.5.1 Factors Affecting Rutting

Permanent deformation or rutting is categorized as a longitudinal depression

which is formed along the wheel paths. Figure 2.6 shows the rutting that happens

on the road. It happened due to the accumulation of minor deformations that

caused by high temperature and repetitive heavy loads. Factors that contribute to

deformations may be caused by too much continuous stress by tire being applied

to the subgrade or by an unstable asphalt mixture where shear strength of the

mixture is too low. In addition, rutting also considered as a structural problem. It

is generally the result happened because of wrong calculation during the

pavement design or of properties in the subgrade that has been weakened due to

the moisture intrusion. In the other research study, the presence of rutting is due to

the accumulated deformation happened in the asphalt surface layers rather than in

the subgrade layer. Incorrect procedure in preparing the asphalt mixture also

contributes to the permanent deformation. It is explained that when a layer of

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asphalt pavement has inadequate shear strength it will cause shear deformation to

occur every time a heavy load such as truck passes through the pavement. A rut

will then appear after the asphalt pavement achieves the maximum load where it

can resist. This type of road distress can reduce the serviceability of the asphalt

pavement and the road user was exposed to a safety hazard.

Figure 2.6 Rutting or permanent deformation on the pavement

2.5.2 Laboratory Test Related to Rutting

2.5.2.1 Hamburg Wheel Tracker

The Hamburg Wheel Tracker (HWT) was developed and established by

Helmut Wind in Hamburg Germany. The advantage of HWT is it can

conduct the test of HMA beam and cylindrical sample in water.

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The vertical load subjecting to the sample is 705 N and applied on a solid

rubber wheel. The diameter of loaded wheel is 194 mm and a width of 47

mm. The sample is compacted to an air void content of 7±1 percent, are

typically subjected to a maximum of 20,000 loading repetitive passes at a

rate of about 340 mm/s (Choubane et al, 1998). Figure 2.7 below shows

the Hamburg Wheel Tracker device.

Figure 2.7 Hamburg Wheel Tracking Device

2.5.2.2 Couch Wheel Tracker

The Couch Wheel Tracker (CWT) is modified version of Hamburg Wheel

Tracker. However in CWT tests only HMA beam samples being

submerged in the water (Choubane et al, 1998). Test samples are

subjected with a 705 N vertical load which is applied through a solid

rubber wheel. The rutting performance is determined by measuring the

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height position of the loading wheel at the center of the travel span after

the process of continuous loading finish The measurements are constantly

recorded on a provided chart during the testing.

2.5.2.3 Georgia Loaded Wheel Tester

The development of Georgia Loaded Wheel Tester (GLWT) is from the

Georgia Institute of Technology at the Georgia Department of

Transportation in the mid-1980's (Choubane et al, 1998). It was designed

and planned with the aim of developing a simplified method to

enhancement the method of Marshall in evaluate the rutting characteristics

of the asphalt mixes which is used in Georgia. Figure 2.8 shows a

schematic drawing of one version of the Georgia Loaded Wheel Tester

Figure 2.8 Schematic drawing of one version of the Georgia Loaded

Wheel Tester

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The advantages using GLWT is it capable of testing samples of the

confined asphalt concrete beam. It tests the samples of asphalt concrete

beam by using a stiff pressurized hose which is mounted at the top of the

specimens. The purpose of the hose was same as a tire which is to transfer

the load that is received from the loaded wheel directly to the beam

(Choubane et al, 1998). One complete loading cycle will involves back

and forth pass through of the loaded wheel. The rut depth is measured and

evaluated using a dial gauge that connected to the device and used a

reference template at set cycle intervals. The result then will be compared

to a pass or fail criteria.

2.5.2.4 LCPC (French) Wheel Tracker

The Laboratoire Central des Ponts et Chaussées (LCPC) wheel tracker

which is also known as Franch Wheel Tracker (FWT) majorly used in

France for more than a decade to determine rutting in HMA pavements

(Choubane et al, 1998). The function of LCPC is to carry out beam

sample test in the air. The samples will be subjected to 5,000 N loads

through a pneumatic tire which has been inflated to 600 kPa. The total

deformation depth of the slab is determined and recorded as the average of

a series of 15 measurements where three measurements is taken randomly

across the sample width at each of five points along the sample length.

The passing criterion for the sample is the average deformation depth must

less than 10 percent from the original sample thickness. Figure 2.9 shows

a France Wheel Tracker device

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Figure 2.9 France Wheel Tracker device

2.6 Polymer Modified Asphalt

2.6.1 The Purpose of Asphalt Modification

Polymer modified Asphalt is asphalt which has undergone modification by

addition of modified binder such as latex and polyacrylates into the mix. The

advantages of using polymer modified asphalt are it has better performance in

durability, resistance and strength. Besides the physical properties of the asphalt

when added modified binder does not change the chemical nature of the asphalt.

Research done also stated that modified asphalt binders make the texture of the

mixture become soft and smooth at lower temperature which resulting in

reduction of thermal cracking. In addition to fatigue resistance of the asphalt

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mixes is being improved with the polymer modified asphalt usage and since the

fatigue resistance of asphalt improves the pavement can resist more traffic load

and extreme climate temperature changes. Figure 2.10 shows the stress diagram of

unmodified asphalt and modified asphalt.

Shear stress ( ) Asphalt binders

Modified Asphalt

Large ‘c’ Unmodified Asphalt

Small ‘c’

Normal stress ( )

Figure 2.10 Stress Diagram of Modified and Unmodified Binder

2.6.2 Type of Asphalt Modifiers

Asphalt modifiers can be categorized in several ways which depends on the

mechanism where the modifier alters the asphalt properties, on the composition

and physical nature of the modifier itself, or on the properties of the target asphalt

that needs improvement or enhancement. A list of the types of modifiers

commonly used in the asphalt industry is given in Table 2.1. The modifiers are

classified based on the nature of the modifier and the generic types of asphalt

modifiers (National Cooperative Highway Research Program, 2001). The target

distress shown in the table corresponds to the main distress the additive is

expected, or claimed, to reduce. The information is based on an interpretation of

the published information for brands of modifiers that belong to the modifier

classes shown. The information in Table 2.1 indicates that asphalt modifiers vary

in many respects. They can be particulate matter or additives that will disperse

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completely or dissolve in the asphalt. They range from organic to inorganic

materials, some of which react with the asphalt, while others are added as inert

fillers. The modifiers generically vary in their specific gravity as well as other

physical characteristics. They are expected to react differently to environmental

conditions such as oxidation and moisture effects.

Table 2.1 Generic types of asphalt modifiers currently used for paving applications

Modifier type

Class

Effects on Distress PD FC LTC MD AG

Fillers Carbon black x x

Mineral: Hydarted lime x x

Fly ash x

Portland cement x

Baghouse fines x

Extenders Sulphur x x x

Wood lignin x

Polymers-Elastomers Styrene butadiene di-block SB x x x

Styrene butadiene triblock/ radial block (SBS) x x x

Styrene isoprene (SIS) x

Styrene ethylbutylene (SEBS)

Styrene butadiene rubber latex SBR x x

Polychloroprene latex x x

Natural rubber x

Acrylorite butadiene styrene (ABS) x

Polymers-Plastomers Ethylene vinyl acctate (EVA) x x

Ethylene propylene diene monomer (EDPM) x

Ethylene acrylate (EA) x

Polyisobutylene x

Polyethylene (low density and high density) x x

Polypropylene x

Crumb rubber Different sizes, treatment and process x x x

Oxidants Manganese compunds x

Hydrocarbons Aromatics x

Napthenics

Paraffinics/ wax x

Vacuum gas oil x

Asphaltenes: ROSE process resins x

SDA asphalteners x

Shale oil x x

Tall oil

Antistrips Polyamides x

Hydrated lime x

Organo-metallics x

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Fiber Polyropylene x x x

Polyster x x

Fiberglass

Steel x x x

Reinforcement x x x

Antioxidants Carbon black x x

Calcium Salts x

Hydarted lime x x

Phenols x

Amines x x

PD: Permament Deformation MD: Moisture Damage

FT: Fatigue Cracking OA: Oxidative Aging

LTC: Low Temperautre Cracking

( National Cooperative Highway Research Program, 2001)

2.6.3 The Ideal Modified Binder

The most important property of asphalt when it is used in pavement construction

is changing in its stiffness with temperature. The ideal binder is necessary to be

hard and stiff enough at changes temperatures so that it can resist against

deformation and it also must be flexible enough at a lower temperature so as to

inhibit cracking. An ideal binder must exhibit the following properties:

i. Adequate rigidity and inelasticity in order to minimize the rutting on a hot

day. In addition, it must have a progressive effect on the fatigue effect of

the bituminous hot mixture.

ii. Flexible enough even during the cold temperature to avoid cracks such as

thermal cracks.

iii. The binder must have light characteristics to allow the pumping process of

liquid binder smooth and fast and the binder is ideal when the viscosity

decreased to facilitate mixing and compaction of the hot bituminous

mixtures.

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2.7 Superior Performing Asphalt Pavement

Superior Performing Asphalt Pavement, better known as Superpave is a one of the

outcomes of the Strategic Highway Research Program (SHRP). SHRP target of

constructing the pavement requires less maintenance, provide a smooth ride, and is a

good value for tax payer’s money. The research was done in 1993, providing several new

elements in the system such as asphalt binder being graded by performance grade (PG),

consensus properties of aggregate, new mix design procedure, and mixture analysis

(National Cooperative Highway Research Program, 2001). Currently, the Superpave mix

design system has become the choice for the majority of transportation companies for

HMA mix design. The key equipment in Superpave method is the Superpave Gyratory

Compactor (SGC).

2.7.1 Background of Superpave

Through the development of asphalt mix design, there are now several different

types of laboratory compaction devices have been established in order to produce

specimens for volumetric and/or physical characterization (National Cooperative

Highway Research Program, 2001). Bruce Marshall and Francis Hveem are the

one whose developed mix design methods and by the late 1950s, these methods

were largely used in pavement construction. The Marshall mix design method

adopted the impact type of compaction while the Hveem mix design method uses

tampering blow and kneading compactor (Hafeez et. al, 2010).

The gyratory concept was credited to Phillipi, Raines, and Love of the Texas

Highway Department, which was a manual unit of gyratory pressing. In the

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1950’s, the concept was copied by John L. Macrae, with the U.S. Corps of

Engineers, developing a new device called gyratory kneading compactor, which

was named as the Gyratory Testing Machine (GTM) in 1993. Another important

contribution to the improvement of gyratory concept is through the Laboratory

Central des Ponts et Chausées (LCPC) in France, where it has a fixed external,

external mold wall angle of one degree with a compaction pressure to 600kPa.

2.8 Superpave Gyratory Compacter

The equipment used in the Superpave mix design method and which is the key piece is a

gyratory compactor as shown in Figure 2.11 which is the principle goals was to develop a

laboratory compaction method, which can consistently produce specimens representative

of in-service pavements. The Superpave Gyratory Compactor (SGC) compact HMA

sample to densities achieved under traffic loading conditions. Its ability to estimate

specimen density at any point during the compaction process is its key feature. Figure

2.11 shows Superpave Gyratory compactor.

Figure 2.11 Superpave Gyratory Compactor

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2.9 Asphalt Pavement Analyzer

The Asphalt Pavement Analyzer (APA) is the new version of the wheel tracker device

which is adapted from the Georgia Loaded Wheel Tester (Choubane et al, 1998). The

APA has implemented additional features which are installation of water storage tank and

is having the ability of testing both gyratory and beam samples. Generally, APA is a

wheel tracking device that applies a vertical load to a steel wheel (A Sholar and Page,

1999) Three beams or six gyratory of the samples can be performed and tested

simultaneously. The loaded wheels are applied to sample test of three pneumatic

cylinders, where each of it is equipped with standard aluminium wheels. The load from

each of the moving wheel is shifted and transferred to a test sample through a pressurized

rubber hose mounted along the top of the sample. The advantage of using APA is it can

evaluate not only the rutting performance of an HMA mixture, but it also can determine

the fatigue cracking and moisture susceptibility under certain condition of the service.

Figure 2.12 and Figure 2.13 shows an Asphalt Pavement Analyzer device and schematic

drawing of the device respectively.

Figure 2.12 Asphalt Pavement Analyzer Device

29

Figure 2.13 Schematic Drawing of the Asphalt Pavement Analyzer

30

2.10 Gap of Research Study

Based on the studied journals, there are more focusing on evaluation of rutting

performance using different types of machineries used and gradation of aggregates. The

journal that using different type of machineries to evaluate the rutting performance such

as Simple Performance Test (SPT), Uniaxial Repeated Creep and Wheel Tracker Tests

were focused on determining the correlation of rutting performance using those

machines.

Besides that, a journal that used different types of aggregate gradation is to identify how

the size of aggregates can affect the performance of rutting. The study of aggregate

physical properties such as elongation and flakiness on rutting impact also was the main

focus of this journal.

On my research work, I’m focusing into the performance of polymer modified binder

against permanent deformation by comparing them with unmodified binder. There were

two types of polymer binder use of this work which are latex and polayacrylates.

Furthermore these two polymer modified binders were also comparable to each other to

select the best used of polymer against rutting. The criteria needed to be compared are the

rut depth which this was obtained through an Asphalt Pavement Analyzer. The result was

shown in term of graph and bar chart for better understanding of their performance on the

pavement. The characteristics of the polymer were analyzed and discussed to understand

why the performance of each polymer modified binder was differ from others polymer

modified binder. Table 2.2 shows a gap of research study.

31

Table 2.2 Gap of research study

Year Title Authors Purpose Finding

2011 Rutting

Evaluation of

Dense Graded

Hot Mix Asphalt

Mixture

Juraidah Ahmad,

Mohd Yusof Abdul

Rahman, Mohd

Rosli Hainin

To investigate rutting

potential using SPT

dynamic modulus test

and how well this test

correlates with Wessex

wheel tracking test to

evaluate the rutting

potential of local HMA

The change in HMA

mixture behaviour

using SPT dynamic

modulus test was

effective to

determine the rutting

potential of the

HMA mix with

varying temperatures

and loading

frequencies.

2010 Evaluation of

Rutting in HMA

Mixtures Using

Uniaxial

Repeated Creep

& Wheel Tracker

Tests

Imran Hafeez,

Mumtaz Ahmed

Kamal and

Muhammad

Waseem Mirza

To predict the

permanent deformation

of HMA mixtures at

elevated temperature

with uniaxial repeated

creep and wheel tracker

test)

The specimen from

the wheel tracker

specimen test is

observed to produce

a less rate of

increase in rut depth

compared to

unconfined uniaxial

repeated creep test.

2011 A review of

fatigue and

rutting

performance of

asphalt mixes

Taher Baghaee

Moghaddam,

Mohamed Rehan

Karim and Mahrez

Abdelaziz

To review previous

studies carried on

fatigue and rutting

properties of asphalt

concrete (AC) and the

effects of additives to

slow the deterioration

of asphalt mixture.

It was determined

that mixtures with

larger aggregate

gradation and higher

asphalt content result

in lower the fatigue

life and slower the

presence of rutting

2012 Performance of

Polymer Modified

Bitumen For

Flexible Bitumen

Ashok Pareek,

Trilok Gupta and

Ravi K Sharma

To investigate the

performance using

polymer modified

bitumen and

unmodified bitumen in

term of rutting

performance.

Shows that the

performance of

polymer modified

bitumen is better

than conventional

bitumen PEN 60/70

32

CHAPTER 3

RESEARCH METHODOLOGY

3.1 Introduction

In this chapter, the detail of progress work and the procedure of how this study was

conducted is explained. Before proceeding to the procedure of laboratory test,

information searching were collected to explore the background of the study. The aim of

this study is to evaluate the rutting performance of polymer modified binder in Hot Mix

Asphalt mix design. Thus, method and process to be used in determining the rutting

performance is listed in detail to achieve the aim of the study. The test is conducted

according to the required specifications, laboratory test procedure and information on the

materials used and also based on the sample properties. The method used in the sample

preparation is the Superpave Mix Design method. The sample mix involves for rutting

performance basically have two types of polymer modified binder which is latex and

polyacrylate. The result of the rutting performance of latex and polyacrylate was

compared and analyzed. After all process are fulfilled, the evaluation of routing

performance on the final compiled HMA sample was conducted through Asphalt

Pavement Alyzer machine. Figure 3.1 shows an illustration design of research studies.

Figure 3.2 shows the Overall Evaluation of Rutting Performance of Polymer Modified

Binder in HMA Mix Design.

33

Stage 1 Stage 2 Stage 3

Figure 3.1 Design of Research Study

Materials Collection for

the Project

Superpave Mix

Design Method

Control

1. Asphalt binder PEN

80/100

2. Aggregate of 19 mm

nom. max size

3. Binder- latex &

polyacrlates

Desk

Study

1. Blending of Specimen:

-Unmodified Binder-Control

-Modified Binder- Latex at 160°C

and 1270 rpm

-Polyacrylate 140°C and 1650 rpm

Compacting and

Testing Samples with

Superpave Gyrator

Compactor

Mixing of HMA mixture

-automatic mixer

Rutting Performance

Evaluation on Polymer

Modifed Binder in

HMA ;

-the specimen was

7±0.5% air void

-Asphalt Pavement

Analyzer

Result and Data

Analysis

Conclusion

34

Figure 3.2 Overall Evaluation of Rutting Performance of Polymer Modified Binder

in HMA Mix Design

Mixture Design

Mathematical Calculation Compacting and testing with

Superpave Gyrator Compactor

Compiling and Establishing Final Blend Bituminous Paving Mixture

Evaluation Rutting on Compiled final Bituminous Paving

Mixture by Asphalt Pavement Analyzer

Conclusion

Superpave Method

Asphalt binder PEN

80/100

Material Collection

Aggregate of 19 mm

nom. max size

35

3.2 Materials Selection

3.2.1 Asphalt Binder

The binder used in this research study is grade PEN 80/100 and based on the

current study, it also stated that asphalt binder is obtained from Port Klang. Type

of asphalt cement binders is classified based on their depth of penetration at

various temperatures. In Superpave mix design the selection of asphalt binder is

totally depends on climate which changes of temperature must be recorded and

traffic-loading conditions of the selected project location.

3.2.1.1 Softening Point

Softening point which also known as ring and ball test is a method to

determine the softening point of asphalt binders, in the range of

temperature of 30 °C to 150 °C. Two horizontal discs of asphalt binder,

cast in shouldered brass rings, are heated at a controlled rate in a liquid

bath while each supports a steel ball. The softening point is reported as the

mean of the temperatures at which the two discs soften enough to allow

each ball, enveloped in a asphalt binder which were control, latex and

polyacrylates to fall a distance of (25,0 ± 0,4) mm.

3.2.1.2 Ductility Test

The ductility of a asphalt material is measured by the distance in cm to

which it will elongate before breaking when a standard briquette specimen

of the material is pulled apart at a specified speed and a specified

36

temperature. Ductility is the property of bitumen that permits it to undergo

great deformation or elongation. In addition, ductility is defined as the

distance in cm, to which a standard sample of the material will be

elongated without breaking. The procedure of the ductility start by the

asphalt (control, latex and polyacrylate) were heated and poured in the

mould assembly placed on a plate. These samples with moulds are cooled

in the air and then in water bath at 27 °C temperature. The excess asphalt

was cut and the surface was leveled using a hot knife. Then the mould with

assembly containing sample is kept in a water bath of the ductility machine

for about 90 minutes. The sides of the molds are removed, the clips are

hooked to the machine and the machine was operated. The distance up to

the point of breaking of thread was the ductility value which is reported in

cm. The ductility value gets affected by factors such as pouring

temperature, test temperature and rate of pulling. The ductility value of the

control, latex and polyacrylate were then compared to determine the binder

properties between modified binder and unmodified binder.

3.2.1.3 Penetration Test

In this test, the consistency of asphalt was examined by determining the

distance in tenths of a millimeter that a standard needle vertically

penetrates into the bitumen specimen under known conditions of loading,

time and temperature. This is the most common methods of measuring the

consistency of a asphalt material at a given temperature. The modified

asphalt (latex and polyacrylate) and unmodified asphalt (control) were

37

examined together to determine the penetration value between the three

specimens.

3.2.2 Aggregates

Aggregates used in the asphalt mixture include various particle sizes which are

coarse and fine aggregates. Figure 3.3 and Figure 3.4 show the aggregate was

obtained from the Blacktop Quarry at Rawang and filled in the sack. The selection

of aggregates is necessary because it affects the performance of HMA mixes. The

preparation of aggregates can be classified into two properties; consensus

properties and source properties as shown in Table 3.1

Figure 3.3 Sample is taken from Blacktop Quarry, Rawang

38

Figure 3.4 Sample Filled in Sack

Table 3.1 Properties of aggregates

Consensus Properties Source properties

a) Coarse aggregate angularity

b) Fine aggregate angularity

c) Flat and elongated criteria

a) Specify gravity

b) Soundness

c) Toughness

d) Gradation

3.2.2.1 Flat and Elongation

Flat and elongation particles defined as the percentage by mass of coarse

and granular aggregates that have a maximum to minimum measurement

ratio greater than five. This classification is used in the Superpave

requirement in purpose to identify aggregates that have a tendency to

obstruct compaction. Flat and elongated particles have a tendency to lock

up between particles more readily during compaction process which makes

the compaction more difficult.

39

3.2.2.2 Toughness

Abrasion test is carried out to check the toughness property of aggregates

and to select whether the aggregates are suitable for different pavement

construction works. The Los Angeles abrasion test is a suggested one for

carrying out the toughness property. The standard of Los Angeles

abrasion test is to determine the percentage wear due to relative rubbing

and crushing action between the aggregate and steel balls used as a

medium to abrasive charge.

The Los Angeles machine comprises of round drum of internal diameter

of 700 mm and length 520 mm mounted on a horizontal axis to make it

rotated. The steel spherical balls of 48 mm diameters and weight 340-445

g were placed inside the machine together with the aggregates. The

number of the abrasion varies depending on the grading of the sample.

The quantity of aggregates to be used usually ranges from 5-10 kg. The

speed of the cylinder to rotate was 30-33 RPM for a total of 500 -1000

revolutions subject to the gradation of aggregates. After the desired

revolution was achieved, the material is sieved and passed fraction is said

as the percentage total weight of the sample. This value is called a Los

Angeles abrasion value. Figure 3.5 shows the Los Angeles Abrasion

Machine.

40

Figure 3.5 LA Abrasion Machine

3.3 Superpave Hot Mix Asphalt Design

The Superpave procedure was used to design the HMA mix used for the performance test

evaluation for this study. The design procedure is based on the percentage of asphalt for

the aggregate blends using the volumetric properties of the mix as the primary criteria.

These include a 4% air voids and a set of minimum values for the voids in HMA sample,

however HMA sample at 7% air voids were prepared for rutting performance test.

41

3.3.1 Aggregates Preparation

The aggregates were oven-dried in oven in large quantity for at least 12 hours at a

temperature of 100° C as shown in Figure 3.6 and Figure 3.7, then the aggregates

are then left to cool at room temperature. The aggregates were then sieved and

separated into their individual particle sizes as shown in the table below. Table 3.2

shows the aggregate gradation for Superpave mixes.

Figure 3.6 Loose Aggregates Before Mixing

Figure 3.7 Oven

42

Table 3.2 Aggregates Gradation for Superpave Mixes

Sieve size

(mm)

Blending Passing % Retained

25 100 0.0

19 96 4.0

12.5 81.0 15.0

9.5 75.0 6.0

4.75 55.0 20.0

2.36 43.0 12.0

1.18 32.0 11.0

0.6 23.0 9.0

0.3 13.0 10.0

0.15 8.0 5.0

0.0075 4.0 4.0

Pan 4.0

Total 100.0

Dust Loss After Wet Sieving

3.3.2 Polymer Modified Binder

The device used to mix the binder with polymer is a hot plate mixer as shown in

Figure 3.8. For the research study, the selected mix method to be used is a wet

method is used to mix with asphalt grade PEN 80/100 where the polymer

modified binder were weight using an electronic scale as shown in Figure 3.9 and

Figure 3.10 respectively. The binder parameter in the research study is shown in

Table 3.3 which is obtained through previous project done by Atikah (2013).

43

Figure 3.8 Hot Plate Mixer for Modified Asphalt

Figure 3.9 Modified Asphalt Preparation (Latex and Polyacrylate)

44

Figure 3.10 Electronic Weighing Scale

Table 3.3 Binder Parameter of Polymer Modified Binder Mixes

Types of binder Optimum

Polymer Content

Blending

Temperature, °C

Blending

Velocity

Polyacrylate 6% 140 1650

Latex 8% 160 1270

45

3.3.3 Preparation Process of Polymer Modified Binder

The preparation of polymer modified binder is shown in Figure 3.11

Figure 3.11 Blending Procedure of Polymer Modified Binder

• The 500 g conventional binder is measure 1. Measure

• Heat the over at 120°C and put the binder inside oven 2. Heat

• Calculate the weight of polymer using following equation;

•𝑃

100 × 𝐴 = 500𝑔 … 1

• 𝑊𝑒𝑖𝑔𝑕𝑡 𝑜𝑓 𝑝𝑜𝑙𝑦𝑚𝑒𝑟 𝑚𝑜𝑑𝑖𝑓𝑖𝑒𝑑 𝑏𝑖𝑛𝑑𝑒𝑟 =𝐴 − 500𝑔 … (2)

• Which:

• P = 100% of mixture minus by percentage of polymer modified binder

• A = weight of conventional binder + polymer modified binder

• % of polymer modified binder is based on the previous research work

3. Calculate

• Mix the polymer modified binder using laboratory mixer based on the mixing parameter as shown in Table 2. 4. Mix

46

After finishing the mix process, the step was repeated with different percentage of

polymer modified binder which is 6% of Polyacrylate and 8%. Figure 3.12 shows

propeller mixer and the blade was used in mixing the binder and duration of

mixing was one hour and heated using an electric hot plate with temperature

control of laser temperature.

Figure 3.12 Mixing Process for Modified Asphalt

3.3.4 HMA Mixing Process

The aggregates and the modified asphalt were initially heated in the oven at a

temperature of 160ºC for about 2 hours as shown in Figure 3.13. The mixer also

switched on to heat up the mixer bucket. After 2 hours, the aggregates and the

47

modified asphalt were weighed according to their optimum binder content

percentage. Figure 3.14 shows the mixing process which took approximately 5 to

10 minutes to allow aggregates to be well coated with binder. Three samples of

aggregate weighing 2200g, 2300g and 2400g for each control sample with

modified asphalt were mixed and compacted in the first place in the Superpave

Gyratory Compactor. Another three samples of aggregates of weighing 1500g

were mixed to determine to maximum specific gravity (Gmm).Table 3.4 shows the

optimum binder content and mix design properties obtained from previous

research (Atikah, 2013).

Figure 3.13 Heating of Aggregates and Binder

48

Figure 3.14 Heating of Aggregates and Binder

Table 3.4 Mix Design Properties

DESIGN MIXTURE PROPERTIES

Mix property

19mm NMAS mixture types Criteria

control polyacrylate latex

Air voids% 4.0 4.0 4.0 4

VMA % 15.8 16.0 15.9 14 min

VFA % 74.7 75.0 74.8 65-75

Dust proportion% 0.8 0.8 0.9 0.6-1.2

%Gmm@ Nini=8 86.5 87.6 86.2 less than 89

Asphalt Binder content 5.5 5.4 5.3

(Source: Atikah,2013)

49

3.3.5 Short Term Oven Aging (STOA)

All HMA mixes were short term aged in the oven for 2 hours at temperature of

140ºC to induce a short term oven aging (STOA). However, loose mix to

determine the maximum specific gravity was left at room temperature to cool as

shown in Figure 3.15.

Figure 3.15 Loose HMA mixture after mixed process

3.3.6 Compaction

The HMA samples are compacted in the Superpave Gyrator Compactor Device

(Figure 3.17) after STOA for two hours. Figure 3.16 shows the 150mm diameter

mould used to compact HMA sample. After compaction the sample allowed to

cool for 24 hours in room. The Bulk Specific Gravity (Gmb

) was then determined

using buoyancy apparatus for each of the compacted HMA samples. From both

Gmm

and the Gmb

data, the percentage air voids for each control, latex and

50

polyacrylates samples are calculated. Figure 3.18 shows that the immersed

samples in water to determine the Gmb. A back-calculation formula was used to

identify the percentage of weight of sample needed for net performance test based

on 7% air void. The final HMA mixture aggregate is then mixed and compacted

and to the corresponding to Ndes

gyrations.

Figure 3.16 Compaction Mould

51

Figure 3.17 Superpave Gyratory Compactor

Figure 3.18 Sample immersed in water

52

3.4 Compacting and Testing HMA mixture of trial blend with Superpave Gyrator

Compactor Device

The Servopac Gyratory Compactor (SGC) is a device used to compact the HMA mixture

in mix design. It is capable to compact the HMA samples to a density which is required

in the field pavement. Basically, there are three main parameters that control the

compaction of the Superpave mix design which are vertical pressure, number of gyrations

and angle of gyration. For vertical stress it was set at 600-kPa, and the angle of gyration

was set at 1.25º, and lastly the number of gyrations, which is not being set up because it

may be various depending on condition of HMA samples. Three (3) samples for each

polymer modified binder and control were compacted at 1.25º in the Servopac Gyratory

Compactor to obtain the air void as shown in Figure 3.19.

Figure 3.19 Compacted HMA Sample

The procedure for sample preparation and testing in the Servopac started with weighing

the aggregates of 2200g, 2300g and 2400g respectively according to the required job mix

formula shown in Figure 3.20. The aggregate and asphalt binder for control, latex and

polyacrylates are preheated separately at 140ºC for about two hours then both are mixed

53

until the aggregates are fully coated with binder. The amount of binder used is based on

optimum binder content obtained from previous research conducted by Atikah, 2013.

The HMA mixture was then placed in the oven for two hours for short-term oven aging

(STOA). Prior to compaction in 150mm mold diameter and 65mm height. The three

samples were then compacted at 1.25º angle of the gyration.

Each specimen was left to cool at room temperature (approximately 25ºC) for at least 24

hours after the compaction process. The Bulk Specific Gravity of the specimen is then

determined using buoyancy balance apparatus. The maximum specific gravity of the

mixture was determined using Corelox machine and buoyancy balance apparatus. From

both Gmm and Gmb result obtained, the air void of the HMA samples was determined using

the following equation to achieve 7± 0.5% air void before proceeding with rutting

performance test.

𝐴𝑖𝑟 𝑜𝑖𝑑 = 100 × (1 − 𝐴

)

Where,

A = bulk specific gravity (gmb)

B = theoretical maximum specific gravity (gmm)

54

Figure 3.20 Preparation Sample of HMA mixes

Heat both binder and

aggregates

Gmb

Mix aggregates and binder

Heat cyclinder mould

a) Aggregates- put into oven

with150°C - 160°C for more than

4 hours

b) Binder- put into oven with 150°C

at one – two hours

The cynlinder mould is place into oven at

160°C for one – two hours

The binder and aggregates is mix together

at 160°C to ensured the aggregates fully

coated with binder

a) Place the mixes of aggregates and

binder into oven for two hours

(ageing process) at 160°C

b) Compact the HMA mixture using

SGC

c) Determine the specify gravity with

corelox

Gmm

a) Store at room temperature for 24

hours

b) Proceed with Corelok to get

specifc gravity

55

3.5 Evaluation of Rutting Performance on HMA Mixture

Rutting or permanent deformation of the laboratory designed mixtures was evaluated

using the Asphalt Pavement Analyzer (APA) as shown in Figure 3.21. This wheel

tracking machine operates under a pair of wheels apply moving loads above two rubber

hose to the specimen in order to simulate the rutting performance in an accelerated

manner. The depth of depression or rut formed on the sample is measured and analyzed

using computer software. The test measures the depth and number of wheel passes to

failure. Each moving steel wheel of APA machine was 8 inches (203.6 mm) in diameter

and 1.85 inches (47 mm) wide.

The aggregates and asphalt mixtures were heated to 150°C, blended together then

returned to the oven for 2 hours before compaction. The HMA samples after the

compaction, is placed in the laboratory with room temperature at least for 24 hours to

allow the aggregates to uniformlly bind with the asphalt mixture . All samples were

compacted to reach target air voids of 7 percent to simulate the typical initial density in

the field. Figure 3.22 shows the set up the specimen.

56

Figure 3.21 Asphalt Pavement Analyzer Machine

Figure 3.22 Sample is placed in APA machine

For APA testing, eight cylindrical samples of which four are control samples, two latex

and two poly were compacted using Superpave Gyratory Compactor. The desired density

57

of HMA mixture was obtained by adjusting the weight of the mixture. Prior to real

testing, the sample was first conditioned in the APA chamber machine for two hours.

Testing on the APA machine was performed at 60°C with the sample sides in full

confinement and the pressure of rubber hose and wheel load was respectively set up at

690 kPa (100psi). The analysis of rut measurements was collected at 0, 25, 4000 and

8000 loading cycles. Figure 3.23 and Figure 3.24 shows the condition of the specimens

after the performance test.

Figure 3.23 Specimen condition after the test

58

Figure 3.24 Rut depth on the HMA sample

3.6 Data Analysis

In this study, the performance of pavement by using a polymer modified binder was

analyzed. The performance graph and bar chart are used to analyze the performance of

each polymer modified binder in terms of rut depth. The APA rut depth measurements as

collected during the performance test are summarized in result and discussion section.

The result was analyzed the effectiveness of rut potential of asphalt mixes between

polymer modified binder and control mixes.

59

CHAPTER 4

RESULT AND DISCUSSION

4.1 Introduction

This chapter discusses the results of laboratory HMA mix rut performances NMAS

19.0mm Superpave mixtures. The cylindrical samples were examined with respect to

rutting at three different mixtures which are control, latex and polyacrylate. Performances

of laboratory mixes were evaluated in terms of rutting by using the Asphalt Pavement

Analyzer machine. From this study, it determines that the design of hot mix asphalt

mixture using Superpave mix design suitable to be developed based on Malaysian

standard. The major steps in testing and analyzing process lead to the outcome of this

study.

4.2 Aggregates Properties Test

Three types of aggregates which are sand, screening and quarry dust were used in order

to developed aggregates blends meeting the requirements of gradation. The standard for

the consensus aggregate test is based on the traffic level and position the pavement layer.

The importance of the source aggregate property test is to estimate the specific stockpile

fraction. The toughness test by LA Abrasion is used to evaluate the percentage change in

coarse particle size of aggregates while aggregate soundness test capabilities to assess

both coarse and fine aggregates. Table 4.1 and Table 4.2 show results of consensus

properties and source properties respectively.

60

Based on the achieved result, the value for both consensus and sound properties is

satisfied and fulfilled the standard of mix design. Thus, the aggregates sample from

Blacktop Quarry,Rawang can be used in Superpave mix design.

Table 4.1 Consensus Aggregates Properties Result Blacktop Quarry, Rawang

Consensus Properties

References Test Method Result Criteria

ASTM D 4791 Flat or Elongation in

Coarse Aggregates

Flakiness Index:

3.10%

Elongation Index:

16.6%

<10 %

<20%

Table 4.2 Source Aggregates Properties Result Blacktop Quarry, Rawang

Source Properties

References Test Method Result Criteria

AASTHO T 96 Los Angeles Abrasion

Test

Percentage of loss:

25.35

<45 %

4.3 Binder Properties Test

Three test have been carried out to test the physical properties of asphalt which are

penetration test, softening point ad ductility test as shown in Table 4.3.

Table 4.3 Physical Properties of Aphalt

Conventional

Bitumen

Polyacrylate

(Modified)

Latex

(Modified)

Penetration value (mm) 85 60 55

Softening Point (ºC) 58 65 70

Ductility Test (cm) 95 125 150

61

Penetration test is a commonly adopted test on bitumen to grade the material in terms of

its hardness and it was used to measure the consistency of bitumen, so that the bitumen

can be classified into standard grades. In this work the penetration grade used were

80/100 where it means that the penetration value lies between 80 and 100. The

penetration value of bitumen helps to assess its strength between modified and

unmodified asphalt. The greater value of penetration indicates softer consistency.

Generally higher penetration bitumen are preferred for use in cold climate and smaller

penetration bitumen are used in a hot climate area. In our climate we preferred lower

penetration grade to avoid softening due to the high temperature of the climate, and based

on the result it was said that modified asphalt has lower penetration value compared to

unmodified asphalt so the use of polymer modified binder in this work can be proceed to

the performance test.

Temperature is noted when the softened bitumen touches the metal plate

which is at a specified distance below. Based on the table 4.3, the lowest

temperature of softening point was 58 ºC using control sample. However the temperature

of softening point of where the ball fall was increased using latex and polyacrylates. The

difference of softening point may influenced by the properties of the asphalt binder.

Asphalt that consists latex has the highest softening point, where high temperature need

to soften the bitumen and same thing goes to polyacrylates specimen. Generally, the

higher softening point indicates lower temperature susceptibility and was

preferred in hot climates thus modified asphalt was showing positive results

in strengthening the HMA mixture for this work study.

62

Ductility is the property of bitumen that allows it to undergo elongation. In this work

asphalt binder are used in the HMA mixtures. It is important that bituminous material

forms ductile thin film around the aggregates that serves as a binder. From the table, the

modified binder has a longer ductility value which is 125 m and 150 cm for polyacrylates

and latex respectively compared to control. The binder material not of sufficient ductility

renders pervious pavement surface and leads to development of cracks. Therefore, the

longer the elongation of the bitumen can resist mean the better it can serve as a binder.

4.4 Evaluation of Rutting Performance using Asphalt Pavement Analyzer

The rut depth from APA at a number of wheel cycles was measured for control, latex and

polyacrylate sample to follow the rate of rutting for these samples. These are shown in

Figure 4.1 and Figure 4.2. It is observed that for all the samples, the APA rutting

accumulated at the end of 8000 cycles and it is measured within the first 25strokes whiles

about two-thirds of the rutting are mobilized at 4000 cycles. This may indicate that in

practice a greater portion cycles such as 4000 cycles of the entire rutting accumulated

within the pavement over its service period is likely to happen very quickly after the first

few months of traffic loading.

The higher the depth of rut indicates that the asphalt used in HMA mixture has lower

strength to against rutting in terms of the bonding with aggregates. This rut depth will be

in the form of densification rutting and it will not be dangerous enough to cause hazard,

but may be risky for motorist if it is deep enough and uneven across the pavement

surface. A very high rutting measured next the first few passes of cycles may seem to

have problem such as unstable mixture especially when the rutting does not begin to

stabilize during this level. This behavior of rutting was observed in the APA rutting for

63

the control sample, which explain that it has unstable mixtures. However, for the

purposes of comparison of the performance control sample and modified asphalt is to

determine the effect of rutting on polymer modified binder and also determined the best

modified asphalt (latex and polyacrylates) can be used to against rutting.

The HMA mixtures were tested with the Asphalt Pavement Analyzer (APA), which is

used as an indirect measure to predict rutting on the field. The mould diameter HMA

samples used were 150mm cylindrical and were compacted to approximately 7% air

voids. The sample was placed and maintained at a temperature of 60ºC in the APA

chamber for at three hours before the test started. Two replicates for each mixture were

tested for 8000 numbers of wheel cycles and the computer software will measure and

averages the rut depths. Figure 4.3 and Figure 4.4 shows the rut depths at the end of 8000

cycles, and other modified asphalt such as latex and polyacrylates.

The APA rut depths obtained from the rutting test show that polymer modified binder

which using latex is the most resistant to rutting with an average rut depths of 5.1mm.

The modified asphalt with polyacrylates average rut depth is 6.5mm while the control

sample is 8.00 mm. Therefore, polyacrylate was considered as more resistant to rutting

compared with control samples. This shows that the polymer modified binder with latex

is the most resistant to rutting followed by polymer modified binder with polyacrylate.

This could be concluded that the properties of unmodified binder was not strong enough

in binding with aggregates compared to the binding properties of modified asphalt with

aggregates. It is also said that hence its natural characteristics which is rubber, the latex

tends to glue itself more strongly to the aggregates and providing strong HMA mixtures.

This suggests that adding polymer into binder could enhance the performance of the

binder itself.

64

Figure 4.1 Asphalt Pavement Analyzer Graph (control and latex sample) for 19 mm

nominal size

0

2

4

6

8

10

12

14

0 401 801 1201 1601 2001 2401 2801 3201 3601 4001 4401 4801 5201 5601 6001 6401

Dep

th(M

M)

Cycles (60 Cycles Per Minute)

Rut Depth Control latex

65

Figure 4.2 Asphalt Pavement Analyzer Graph (control and polyacrlate sample) for 19 mm

nominal size

0

2

4

6

8

10

12

14

0 400 800 1200 1629 2029 2429 2829 3229 3629 4029 4429 4829 5229 5629 6029 6429

Dep

th(M

M)

Cycles (60 Cycles Per Minute)

Rut Depth Control Polyacrlate

66

Figure 4.3 Asphalt Pavement Analyzer Graph (control and latex sample) for 19 mm

nominal size

0

2

4

6

8

10

12

14

0 401 801120116012001240128013201360140014401480152015601600164016801720176018001

Dep

th(M

M)

Cycles (60 Cycles Per Minute)

Rut Depth Control Latex

67

Figure 4.4 Asphalt Pavement Analyzer Graph (control and polyacrlate sample) for 19 mm

nominal size

0

2

4

6

8

10

12

14

0 400 80012001629202924292829322936294029442948295229562960296429682972297629

Dep

th(M

M)

Cycles (60 Cycles Per Minute)

Rut Depth Control Polyacrylate

68

CHAPTER 5

CONCLUSION AND RECOMMENDATION

5.1. Conclusion

The Superpave method using HMA mixtures performances was used in this study to

evaluate the rutting performance between modified asphalt and unmodified asphalt of

Superpave mixtures. During the preparation of the samples it was noted that the mixes

with the polymer modified binder which are latex and poly were difficult to mix

compared to preparation of control sample. At lower temperature, it will increase the

cooling effects on the mix thus it increases the stiffness of the mix and viscosity of the

asphalt. For polymer modified binder the temperature of the pan and velocity of the blade

must be aware during mixing in order to stabilize the properties of the polymer modified

binder.

The compiled final sample was obtained through the calculation where the weight of

aggregates and asphalt were being adjusted and the preparation sample was based on the

Superpave mix design procedures. The HMA mixtures were tested in Servopac Gyratory

Compactor, and Asphalt Pavement Analyzer and their evaluation of ruting performance

were compared with modified (latex and poly) and unmodified (control) asphalt of HMA

mixtures.

Meeting the current rutting performance requirement appears to result in high rutting

depth for control samples; consequently these mixtures may have poor rutting resistances

even though these samples may meet the standard of the Superpave mix design. It

appears that at lower asphalt contents which the OBC is lower such as 5.3% for latex, the

69

aggregate may have greater impact on the mixture performance of rutting, overriding that

of the asphalt. The rut depths were measured and analyze for the sample tested in the

APA seems to have a correlation with rutting resistance of the sample. In this study, it

was determined that average rut depth of control, latex and polyacrylates at 6500 cycles

were 7.5mm, 4.9mm and 6.5mm respectively. It was obtained that latex has the least

depth of rut compared to control and polyacrylate hence it show that latex is highly

recommended as a polymer modified binder to use in road construction in purpose to

against rutting. The sample with high rut depth in the APA corresponds to have a low

rutting resistance of the sample, while a relatively low depth of the rut in the APA also

relates to a relatively higher rutting resistance of the sample.

5.2. Recommendation

The following recommendations are based on the above findings evolving from this study

and other related research efforts. Further study and more data are required to validate the

findings and conclusions as well as increase the level of confidence in these findings.

i. The rate of change of weight of aggregates and asphalt content, , measured from

compaction in the Servopac Gyratory Compactor may in terms of density will be

a potential parameter for assessing the rutting resistance of coarse mixtures in the

laboratory and, therefore, should be investigated further for this purpose. It must

also be investigated for fine mixtures.

ii. Rut depth measured from the APA has a potential relationship with the rutting

resistance of mixtures and could be used to predict the rutting performance of

mixtures in the laboratory.

70

iii. Study can be conducted by using all modified asphalt in three types of gradation

such as 9.5 mm NMAS and 12.5mm NMAS through an engineering test such as

APA to observed the correlation of rutting on different gradation.

iv. The study also recommended to be done by adding some additive such as

hydrated lime in a small percentage to the different types of hot mix asphalt

gradation. The outcomes of the research are to determine whether the additives

help to resist rutting and identify types of gradation with additives can resist

rutting better.

71

REFERENCES

A Scholar,G and Page, G.C (1999), Follow Up Evaluation of The Asphalt Pavement

Analyzer, Research Report,99-436

Ahmad, J. Abdul Rahman, M.Y and Hainin M.R (2011), Rutting Evaluation of Dense Graded

Hot Mix Asphalt Mixture. International Journal of Engineering and Technology, 11, 56-

60

Choubane, B, Page, G.C and Musselman, J.A (1998), Investigation of the Suitability Asphalt

Pavement Analyzer for Predicting Pavement Rutting, Research Report,88-427

Garber, N.J. and Hoel, L.A. (2010), Traffic and Highway Engineering, Cengage Learning,Usa,

Edition 4

Hassan, A. and Hj. Suffian, Z. (2008), Speciality Mixes in the New Malaysian Public Work

Department Road Specification, Highway Materials and Construction, 1,4-10

Hafeez, I., Kamal, M.A and Mirza, M.W (2010), Evaluation of Rutting in HMA Mixtures

Using Uniaxial Repeated Creep and Wheel Tracker Tests. Pak. J. Engg. & Appl. Sci.,

7, 55-64

Moghaddam, T.B., Karim, M.R. and Abdelaziz, M. (2011), A review on fatigue and rutting

performance of asphalt mixes. Scientific Research and Essay, 6(4)

Muzaffar Khan, K, Page, G.C and Ahmed Kamal, M (2012), Rutting Based Evaluation of

Asphalt Mixes, Pak. J. Engg. & Appl. Sci.,11, 60-65

Pareek, A, Gupta, T and K Sharma, R (2012), Performance Of Polymer Modified Bitumen

For Flexible Pavements Pak. J. Engg. & Appl. Sci.,1, 1-10

Thompson, M.R. and Nauman, D. (n.d.), Rutting Rate Analyses of the AASHO Road Test

Flexible Pavements. Transportation Research Record, 1384, 36- 48