UTILIZATION OF WASTE HIGH DENSITY POLYETHYLENE (HDPE) AS COARSE

AGGREGATE REPLACEMENT AND GLASSES AS FILLER IN HOT MIX ASPHALT

NURMAZIDAH BINTI ABDULLAH ZA WA WI

Thesis submitted in fulfillment of the requirements for the award of the degree of

B.Eng (Hons) Civil Engineering

Faculty of civil Engineering and Earth Resources

UNIVERSITI MALAYSIA PAHANG

JANUARY 2015

IIA

ABSTRACT

Flexible, rigid and composite are the three typical types of pavements. Commonly, flexible pavement is used especially in municipal, state and federal road in Malaysia. It consists five layers such as subgrade, subbase, base, base course and wearing course. In addition, the main structural function of pavement is to support the vehicles wheel load applied to the road 'and distribute to the . subgrade. High Density Polyethylene (HDPE) which is one of the polymers which is very familiar material used to produce many kind of product such as packing films, pipes and large blow and rotating moulding items while crushed glasses in non-metallic and inorganic material with 2.67 of specific gravity. Flexible pavement is commonly facing three major failures such as rutting, fatigue cracking and thermal cracking. The objective of this research is to investigate the optimum and effect usage of recycled HDPE as coarse aggregate replacement with crushed glasses as filler in modified asphalt mixture by determining the stiffness and permanent deformation. The modified asphalt mixture were produced from content concentrate of waste HDPE fillet range 2%, 4%, 6%, 8% and 10% of the weight of asphalt mixture with sieve size from 3.35 mm to 1.18mm and 4% to 6% is the range of the optimum bitumen content of hot mix asphalt wearing course 14 (ACWI4) with 80/100 of penetration grade of bitumen by referring Standard Specification for Road Works in Malaysia. The performance of the aggregate and bitumen is complying with Specification of Public Work Department 2008 in Malaysia. Therefore, these aggregates and bitumen can be used as asphalt for modified and unmodified sample. The Repeated Load Axial Test (RLAT), Indirect Tensile Stiffness Modulus Test (ITMS) were used to determine the permanent deformation and stiffness of asphalt, respectively. The density-void analysis indicates that the optimum bitumen content is 5.37% of weight of bitumen content. The result shows that the HDPE modified asphalt with crushed glass could enhance the stiffness of asphalt at 6% aggregate replacement at temperature 30°C. This modification also improves permanent deformation at 1800 cycles. Therefore the HDPE modified asphalt with crushed glasses is suitable to use for road pavement in term of economic and environmental aspects.

V

ABSTRAK

Lentur, tegar dan komposit adalah tiga jenis turapan jalan. Biasanya, turapan lentur digunakan terutama di kawasan bandar, negeri dan jalan persekutuan di Malaysia. la mengandungi lima lapisan seperti subgred, subtapak, asas, lapisan tapak dan lapisan kursus. Selainv, itu,, fungsi utama struktur turapan adalah untuk menyokong beban kenderaan yang dikenakan kepada jalan dan mengagihkan kepada subgred. Berketumpatan tinggi Polyethylene (HDPE) yang merupakan salah satu polimer yang sangat biasa digunakan untuk menghasilkan pelbagai jenis produk seperti pembungkusan filem, paip dan tamparan besar clan berputar item acuan manakala gelas dihancurkan ada!ah bukan logam dan bahan bukan organik dengan graviti tertentu iaitu 2.67. Turapan lentur biasanya menghadapi tiga kegagalan utama seperti aluran, keretakan kelelehan clan keretakan haba. Objektif kajian mi adalah untuk menyiasat penggunaan yang optimum dan kesan HDPE dikitar semula sebagai pengganti agregat kasar dengan kaca dihancurkan sebagai pengisi dalam campuran asfalt diubahsuai dengan menentukan kekukuhan dan ubah bentuk kekal. Campuran asfalt diubahsuai dihasilkan daripada pekatan kandungan sisa HDPE pelbagai dalam bentuk fillet dalam lingkungan 2%, 4%, 6%, 8% clan 10% daripada berat campuran asfalt dengan saiz ayak clan 3.35mm ke 1.18mm dan 4% hingga 6% adalah lingkungan kandungan optimum bitumen bagi campuran asfalt panas lapisan asphalt konkrit 14 (ACWI4) dengan 80/100 gred penetrasi bitumen dengan merujuk Standard Spesifikasi untuk Jalan Raya di Malaysia. Prestasi agregat dan bitumen telah mematuhi spesifikasi Jabatan Kerja Raya 2008 di Malaysia. Oleh itu, agregat dan bitumen boleh digunakan sebagai asfalt untuk sampel diubahsuai dan tidak diubah suai. Ujian Beban Paksi Berulang (RLAT), Ujian Modulus Tegangan Kekukuhan Secara Tidak Langsung (ITMS) telah digunakan untuk menentukan ubah bentuk kekal dan kekukuhan asfalt. Analisis rongga berkepadatan menunjukkan bahawa kandungan optimum bitumen adalah 5.37% daripada berat kandungan bitumen. Hasil kajian menunjukkan bahawa FIDPE asfalt diubahsuai dengan kaca dihancurkan boleh meningkatkan kekukuhan asfalt pada 6% penggantian agregat pada suhu 30 0 C. Pengubahsuaian mi juga meningkatkan ubah bentuk kekal di 1800 kitaran. Oleh itu HIDPE asfalt diubahsuai dengan kaca dihancurkan sesuai untuk digunakan untuk turapanjalan raya dari segi aspek ekonomi dan alam sekitar.

vi

TABLE OF CONTENTS

PAGE

SUPERVISOR'S DECLARATION

STUDENT'S DECLARATION

ACKNOWLEDGEMENT

ABSTRACT iv

ABSTRAK v

TABLE OF CONTENTS vi

LIST OF TABLES x

LIST OF FIGURES xi

LIST OF SYMBOLS xii

LIST OF ABBREVIATIONS xiii

CHAPTER 1 INTRODUCTION

1.1 Introduction

1.2 Problem Statement 4

1.3 Objective 5

1.4 Scope of Study 5

1.5 Significant of Study 7

CHAPTER 2 LITERATURE REVIEW

2.1 Introduction

2.2 Flexible Pavement

2.3 Flexible Pavement Failure

2.4 Asphalt Mixture Properties Evaluation

2.4.1 Indirect Tensile Strength Test 2.4.2 Static Creep Test 2.4.3 Repeated Load Axial Test (RLAT) 2.4.4 Hamburg Wheel Tracking Test

8

9

10

13

14 14 15 16

vii

2.5 Hot Mix Asphalt 17

2.5.1 Asphalt 17 2.5.2 Aggregate 19

2.5.2.1 Aggregate Gradation (ASTM C136) 22 2.5.2.2 Type of Aggregate Gradation 23

253 Mineral Filler 25

2.5.3.1 Types of Mineral Filler 25 2.5.3.2 Filler Gradation 26

2.6 Polymer 27

2.6.1 High Density Polyethylene (HDPE) 28 2.6.2 HDPE Modified Bitumen 29

2.7 Waste Glass 29

CHAPTER 3 METHODOLOGY

3.1 Introduction 31

3.2 Materials 32

3.2.1 Aggregates 33 3.2.2 Bitumen 34 3.2.3 Portland Cement 34 3.2.4 High Density Polyethylene (HDPE) 35 3.2.5 Crushed Glasses 36

3.3 Experimental Design 37

3.4 Asphalt Mix Design 39

3.4.1 Aggregate Gradation 39 3.4.2 Optimum Bitumen Content 39

3.5 Los Angeles Abrasion Test (LA) 40

3.6 Aggregate Crushing Value (ACV) 41

3.7 Aggregate Impact Value (AIV) 42

3.8 Ten Percent Fines (TPF) 44

3.9 Penetration Test 45

3.10 Softening Point Test 47

3.11 Density and Void Analysis 48

3.11.1 Bulk Density 48 3.11.2 Void In Total Mix (VTM) 49 3.11.3 Void In Mineral Aggregate (VMA) 50 3.11.4 Void Filled with Bitumen (VFB) 50

viii

3.12 Indirect Tensile Stiffness Modulus Test (ASTM D4123) 51

3.13 Repeated Load Axial Test 53

CHAPTER 4 RESULTS AND DISCUSSIONS

4.1 Introduction 55

4.2 Performance of Aggregate and Bitumen 56

4.3 Density and Void Analysis 56

4.3.1 Void in Total Mix (VTM) 57 4.3.2 Void In Mineral Aggregate (VMA) 58 4.3.3 Void Filled with Bitumen (VFB) 59 4.3.4 Bulk Density 60

4.4 Indirect Tensile Stiffness Modulus Test (ITSM) 61

4.4.1 Indirect Tensile Stiffness Modulus Test for 61 Unmodified Sample

4.4.2 Indirect Tensile Stiffness Modulus Test for 62 Modified Sample

4.5 Repeated Load Axial Test (RLAT) 63

4.5.1 Repeated Load Axial Test (RLAT) of modified sample 63 (HDPE with Portland cement)

4.5.2 Repeated Load Axial Test (RLAT) of modified sample 65 (I-IDPE with crushed glasses)

CHAPTER 5 CONCLUSIONS AND RECOMMENDATIONS

5.1 Conclusions 66

5.2 Recommendations 68

REFERENCES 69

APPENDICES 71

Al Performance of Aggregate and Bitumen 71

A2 Density and Void Analysis Result (Control or Unmodified Sample) 73

A3 Indirect Tensile Stiffness Modulus Test for Unmodified Sample 76

A4 Indirect Tensile Stiffness Modulus Test for Modified Sample 77

(HDPE with Portland Cement)

A5 Indirect Tensile Stiffness Modulus Test for Modified Sample 78

(HDPE with Crushed Glasses)

A6 Repeated Load Axial Test for Unmodified Sample 79

ix

A7 Repeated Load Axial Test for Modified Sample 84

(HDPE with Portland Cement)

A8 Repeated Load Axial Test for Modified Sample 85

(HDPE with Crushed Glasses)

x

LIST OF TABLES

Table No. Title Page

1.1 Gradation Limit of Asphaltic Concrete 6

1.2 Design Bitumen Content 6

2.1 Bitumen Properties 19

2.2 Typical aggregate requirement and for road awareness 21

2.3 Size of Aggregate 24

2.4 Example of dense graded aggregate 25

2.5 Physical Properties of Mineral Fillers 27

2.6 Mineral Filler for Bituminous Mix 27

3.1 Gradation Limit for ACWI4 for I 136g of asphalt mix design 32

3.2 Indirect Tensile Modulus Stiffness Parameter 51

3.3 Dynamic Creep Test Parameter 53

4.1 Performance Quality of Bitumen and Aggregate 56

4.2 Results of Density and Void Analysis with PWD requirement 57

xl

LIST OF FIGURES

Figure No. Title Page

1.1 Typical cross section of flexible pavement 2

1.2 Rutting along the wheel path 3

2.1 Fatigue cracking formation 12

2.2 Bottom up of fatigue cracking (i), Top down of fatigue cracking (ii) 13

2.3 Repeated Load Axial Test 40°C (mixture A/D) 16

2.4 Main Type of Aggregate in Malaysia 21

2.5 Typical Aggregate Gradation Plot 22

2.6 Stationary Polymer Bending System 29

3.1 Aggregates 33

3.2 Bitumen Penetration Grade 80/100 34

3.3 Ordinary Portland Cement 35

3.4 High Density Polyethylene (HDPE) 36

3.5 Crushed Waste Glass 37

3.6 Experimental Design Flow 38

3.7 Los Angeles Abrasion Machines 41

3.8 Aggregate Crushing Value 42

3.9 Aggregate Impact Value 44

3.10 Penetration Test 46

3.11 Softening Point 48

3.12 Indirect Tensile Modulus Stiffness Test 52

3.13 Repeated Load Axial Test 54

4.1 Relationship between air void and bitumen content 57

(VTM versus bitumen)

4.2 Relationship between void in mineral aggregate and bitumen content 58

(VMA versus bitumen content)

xii

4.3 Relationship between void filled and bitumen content 59

(VFB versus bitumen Content)

4.4 Relationship between bulk density and bitumen content 60

4.5 Relationship between resilient modulus and bitumen content of 61

unmodified sample

4.6 Relationship between resilient modulus and HDPE content of 62

modified samples

4.7 Relationship between Axial Strain and cycle of the samples between 64

unmodified and modified sample (HDPE with Portland Cement)

4.8 Relationship between Axial Strain and cycle of the samples between 65

unmodified and modified sample (T-IIJPE with crushed glasses)

LIST OF SYMBOLS

Micrometre

Pw Density of Water

% Percentage

Total Strain, Bandwidth Parameter

LIST OF ABBREVIATION

mm Millimetre

HDPE High Density Polyethylene

PET Polyethylene Terephthalate

HMA Hot Mix Asphalt

ACW Asphalt Concrete Wearing

JTSM Indirect Tensile Stiffness Modulus

ITS Indirect Tensile Strength

RLAT Repeated Load Axial Test

ACB Asphalt Concrete Binder

DMA Dynamic Mechanical Analysis

Pmax Maximum Applied Load

kPa Kilopascal

UTM Universal Testing Machine

LVDTs Linear Vertical Displacement Transducers

ASTM American Society for Testing and Materials

C Celcius

RPM Revolutions Per Minute

TPF Ten Percent Fines

kg Kilogram

cm Centimetre

BS British Srandard

Max Maximum

Min Minimum

AASHTO American Association of State Highway and Transportation Officials

OPC Ordinary Portland Cement

PE Polyolefins

PP Poly-Propylene

xl"

EVA Ethylene Vinly Acetate

SBS Styrene Butadiene Styrene

LDPE Low Density Polyethylene

TPs Thermoplastics

CaCO3 Calcium Carbonate

LA Los Angeles Abrasion

ACV Aggregate Crushing Value

AIV Aggregate Impact Value

VTM Voids in Total Mix

VMA Voids In Mineral Aggregate

VFA Voids Filled with Biumen

MS Malaysian Standard

PWD Public Work Department

xlv

CHAPTER 1

INTRODUCTION

1.1 BACKGROUND

Flexible, rigid and composite are the three typical types of pavements.

Commonly, flexible pavement is used especially in municipal, state and federal road in

Malaysia. Flexible pavement typically consists of asphalt mixture placed over granular

base or subbase layers which supported by the compacted soil referred to as the

subgrade (Papagiannakis et al., 2008). Flexible pavement structure consists of subgrade,

subbase, base, base course and wearing course. In addition, the main structural function

of pavement is to support the vehicles wheel load applied to the road and distribute to

the subgrade. The best design of wearing coarse by selection of materials, gradation and

bitumen content able to form good skid resistance, desirable stability, durability and

good workability which allow the rapid drainage of surface water, minimize traffic

noise, resistance cracking, withstand traffic turning and braking force, protect

underlying road structure, require nominal maintenance, be capable of being recycled or

overlaid and be durable and give the value or money (O'Flaherty,2002).

2

The sizes and materials of aggregate are different depend on the classification of

aggregate which is coarse aggregate and fine aggregate. Coarse aggregate should be

retained on 2.4mm sieve opening of crush rock or crushed gravel and free from foreign

materials. Meanwhile, fine, aggregate should be passing on 2.4mm sieve opening and

shall be clean, ';hard, durable and free from clay, mud and other foreign materials. The

typical cross section of a flexible pavement is shown in Figure 1 .1.

So I Cost Prime cost

Surface Coure(-5O in

I BIrgec courae(50—laO mm) t I

Base course (100-300 mm)

I Subbase Course (100-300 fun) I

MM)

?tural Subie

Figure 1.1:Typical cross section of a flexible pavement

Bitumen consists two types of penetration grades, the range is between 60 - 80

and 80 -100. Based on the specification of the JKR/SPJ/2008-S4, the bitumen of

penetration grade 60 -80 is recommended to be used for heavy traffic roads in order to

achieve higher stability of mixture and to lessen the possibility of bitumen bleeding or

flushing at high temperature.

Permanent deformation or rutting is one of the pavement failures due the stress

caused by the traffic load pressure. The results from many agencies in world had

showed that the failure of permanent deformation is related to the materials in asphalt

mixture use for the wearing coarse layer of the pavement (Tayfur et al., 2005).

Therefore, reconstruction the sub base or base to increase the strength or overlay rutted

area with bituminous surfacing is probable treatment for this 'condition of flexible

pavement.

3

Rutting from weak subgrade occur in the wheel paths of the vehicle travelling on

a flexible pavement as shown in Figure 1.2. The thickness of pavement layers does not

provide enough strength to reduce the applied stress to the tolerable level as well as it is

weakened by the intrusion of moisture.

Figure 1.2: Rutting along the wheel path

Nowadays, the pavement layer consists of recycled materials such as plastics

and crushed glass. High Density Polyethylene (HDPE) which is one of the types of

polymer is a very familiar material used to produce many kind of product such as

packing films, pipes and large blow and rotating molding items (Rosato, 2004). The

HDPE products are often flexible, corrosion and chemical resistance, lightweight while

being extremely tough and at the same time, it can be recycled and reused. In addition,

HDPE resins have high strength (Campo, 2008).

Meanwhile the waste glass is non-metallic and inorganic, it can neither be

incinerated nor decomposed, so it may difficult to reclaim. It had been used in highway

construction as an aggregate substitute in hot mix asphalt paving and most of countries

in the world incorporated glass into their road specification which encouraged greater

use of the materials. While the use of waste glass as filler in hot mixed asphalt is still

not widely experimented (Johy H. Et al.,201 1).

4

Recently, several experiments and testing had been done to improve the

properties of asphalt mixture. The properties of waste glass as a filler in hot mix asphalt

(HMA) is used to improve the engineering properties of asphalt mixture.

Meanwhile HDPE had proved by modified the bitumen or asphalt mixture using

polymers, several properties of asphalt mixture such as temperature susceptibility,

fatigue life, and resistance to permanent deformation can be improved (Jain et al., 1992;

Panda and Mazumdar, 2002; Tayfur et al., 2005; Yildirim, 2005; Hassani et al., 2005).

1.2 PROBLEM STATEMENT

Malaysia is the developing country where the roads and highways are an

important role to connect a place to the other destination or place. Flexible pavement is

commonly used in Malaysia and it facing three major failures such as rutting, fatigue

cracking and thermal cracking. In this case, I referred at Gambang road because the road

condition was very bad and unsatisfactory due to the failures of the road. The failure

occurs due to.traffic load and the materials use for the construction (Thom, 2008).

In addition, the condition of roads are affecting the safety of road users,

therefore the bad condition of road may make the hazard of the road and cause accident

frequently during raining day and monsoon season. In the other words, the government

and private agencies will spend a lot of money for maintenance works.

Recently, the amount of solid waste such as waste glasses and waste plastics, the

waste plastics majority comes from PET and HDPE in Malaysia increase due to human

needs. According to the Global Environment Centre, a non-government organization in

Malaysia in year 2008, 23 000 tonnes of waste was produced each day in Malaysia, with

less 5% of the waste being recycled. However, this amount is expected to rise to 30 000

tonnes by the year 2020 (Global Environment Centre, 2009). The amount of waste

generated continues to increase due to the increasing population and development. By

applying unsystematic process of extracting a proportion of recyclable items from the

main waste, it make all waste simply disposed of in landfills.

5

1.3 OBJECTIVE

The permanent deformation on asphalt pavement cause rutting, corrugation,

depression and shoving on the flexible pavement. Therefore, in the effort to produce

durable and long life service asphalt pavement, the study on the modification of asphalt

mixture using waste HDPE and crushed glasses as partial replacement aggregate on

asphalt concrete wearing 14 (ACW 14). This study is experimental work by using

Universal Technical Machine (UTM). The main objectives of the study are:-

1. To determine optimum bitumen content of the asphalt mixture

2. To investigate stiffness modulus by using Indirect Tensile Strength Test

(ITMS)

3. To determine permanent deformation behavior of HDPE as replacement

coarse aggregate in modified asphalt and crushed glasses as a filler

1.4 SCOPE OF STUDY

This study is mainly based on laboratory experiment. '1 he scope ottlie research is

mainly divided into two part; (i) control mixture and (ii) modified mixture of asphalt for

flexible pavement. The both sample, the ACW 14 of aggregate gradation size is used in

the design pavement. The modified asphalt is proposed to use in the wearing course. In

addition, construction of bituminous layer required a higher cost than the other layers.

Aggregate gradation ACW 14 is mixed with bitumen 80/100 grade of penetration

will be used for control asphalt and modified asphalt. The density and air void analysis

is made to determine the optimum bitumen content of the control mixture for modified

mixture of asphalt. In addition, some portion of coarse aggregate are replaced with the

waste HDPE in fillets in range 2% to 10% of modified HDPE with crushed glasses for

asphalt mixture modification purpose and to investigate the stiffness of ACW 14 by

Indirect Tensile Stiffness Modulus test (ITSM). The Repeated Load Axial Test (RLAT)

on the control and modified mixture of asphalt to determine the permanent deformation

behavior.

In order to achieve the objective of this research, there are several testing will be

conduct which are bitumen and aggregate test, void-density analysis, Indirect Tensile

Stiffness Modulus test (ITSM) and Repeated Load Axial test (RLAT). This study will

be conducted as follow which is hot mix asphalt wearing course 14 (ACW 14). The

gradation limits for asphaltic concrete is shown in Table 1.1 and the design bitumen

contents is shown in Table 1.2.

Table 1.1: Gradation Limit of Asphaltic Concrete

B.S Sieve Size ACW 10 ACW 14 ACB 28

(mm) % Passing by weight

37.5 - -

28 - - 100

20 - 100 72-90

14 100 90-100 58-76

10 90-100 76-86 48-64

5 58-73 50-62 30-46

3.35 48-64 40-54 24-40

1.18 22-40 18-34 14-48

0.425 12-26 12-24 8-20

0.15 6-14 6-14 4-10

0.075 4-8 4-8 3-7

Table 1.2: Design Bitumen Contents

ACW 10 (Wearing Coarse) 5.0%— 7.0%

ACW 14 (Wearing Coarse) 4.0%-6.0%

ACB 28 (Binder Coarse) 3.50/o— 5.5%

7

1.5 SIGNIFICANT OF STUDY

The permanent deformation is the structure damage will cause the accidents to

the users. Therefore, a solution for this problem has to be found out. The way to solve

this problem i by reduce the probability of the structure failure and increase the service

life of roads. Many researchers had proved that the modification of asphalt mixture with

the modifier such as polymer can improve the properties of asphalt mixture (Haasani et

al., 2005; Zoorob and Suparma, 2000). By improving the properties of permanent

deformation performance of asphalt concrete pavement, it will be increase the life

service of pavement.

The HDPE product is one of the most popular recyclable plastic solid wastes.

Due to mechanical and chemical characteristics of this plastic, it is suitable to be used as

modifier in asphalt mixture. This advantage of HDPE is used in this study to design the

asphalt mixture that can resist permanent deformation behavior. Besides, from this

research, it will help to investigate stiffness characteristics of the modified asphalt

compare with the control asphalt and able to determine the optimum effects of the

HDPE as an additive in asphalt. By contributing the plastic solid waste into the

pavement construction, it can be solve the landfill capacity problem and may reduce the

negative impact of the waste materials to the environment with reused it in asphalt

pavement.

CHAPTER 2

LITERATURE REVIEW

2.1 INTRODUCTION

This chapter is divided by four main parts: flexible pavement, asphalt mixture,

polymer and mineral filler (crushed glasses). First part of this chapter is the review on

flexible pavement. The flexible pavement consists of major component of flexible

pavement structure and types of flexible pavement failure. The levels of flexible

pavement structures are wearing course, base, subbase, and subgrade. Besides, the

flexible pavement failures are including the permanent deformation, fatigue cracking,

stiffness and thermal cracking.

The second part of this chapter is regarding to the asphalt mixture. There are

several experiments to evaluate the properties of asphalt mixture such as Indirect

Tensile Strength, Static Creep Test and Repeated Load Axial Test. In sub topic

aggregate, there are review on aggregate gradation, types of aggregate gradation and

aggregate properties.

The polymer part is described about the high density polyethylene (HDPE) and

the function of HDPE in modified asphalt. The waste glass or crushed glasses as

mineral filler are the last part in this literature review

2.2 FLEXIBLE PAVEMENT

The component of flexible pavement consists of surface course, base, subbase

and subgrade. The function of pavement structure is to distribute imposed wheel load

over a large area of the natural soil. Flexible pavement which include asphalt concrete,

stabilized or granular material, or bound granular material distribute the load over a

cone shape area under the wheel, by reducing the imposed unit stresses as depth

increases. The shear strength of the soil is usually not high enough to support the traffic

load. The shear failures would occur in the wheel path in soils and ruts would form if

the vehicles were travel on it. Therefore, the structure of the flexible pavement helps the

distribution of load to the lower layer and decreases the failure of the flexible pavement.

Surface course consist of asphalt concrete. The layer is directly contact with the

traffic load and provides several characteristics such as friction, smoothness, noise

control, rut resistance and drainage. In addition the safety of road users will be assured

by the availability of these characteristics and able to prevent the surface water from

entering into underlying base, subbase and subgrade. This upper structural layer of

material is sometimes is subdivided into two layers: wearinc' cmimp. nnd

intermediate/binder course. The wearing course is the upper layer of the road surface. It

must be capable of withstanding the wear and abrasive effects and must. possess

sufficient stability to prevent it from shoving and rutting under traffic loads. Otherwise,

it may improve the skid resistance, minimize the hydroplaning effects at high speeds

and improve the wet night visibility. In addition, it serve a useful propose in preventing

the entrance of excessive quantities of surface water into the base and subgrade from

directly above (John Wiley & Sons, 2004)

Base course located beneath the surface course with the high stability and

density. Its principal purpose is to distribute the stresses created by wheel loads acting

on sufficiently great to result in excessive deformation or displacement of that

foundation layer. The base courses are usually constructed out of aggregate or hot mix

asphalt (HMA). Thus layer receive load from upper layer and distribute to the subbase.

The rutting and shear failure does not occur in best design of base course (Lavin, 2003).

10

Subbase is located between the base course and subgrade. The subbase course is

composed of either solely granular materials (aggregate), soils or granular material

stabilized by an additive. The granular may contains aggregate from sand, deposit from

quarry, recycled concrete pavement, slag or other material. The subbase generally

consists of lower quality materials than the base course but better than the subgrade

soils. Subbase , course must have ability to distribute the load and functioning as

structural support and also can minimize the intrusion of fines from the subgrade into

the pavement structure, improve drainage and minimize frost action damage. In certain

case, the subbase course is not always needed or used in flexible pavement structure

(Lavin, 2003).

Subgrade is the native material which the pavement structure is placed. It is

consisted of natural ground, commonly from cut and fill process. In some cases,

subgrade were often been called as the formation level. Two most important

characteristic of subgrade are the loads bearing capacity and volume changes. The

subgrade must be able to support the loads transmitted from the upper pavement

structure. This load bearing capacity is affected by degree of compaction, moisture

content and soil type. For soil volume changes due to the exposed to excessive moisture

content, while soils with excessive fines may be susceptible to frost heave in freezing

areas, (Lavin, 2003)

2.3 FLEXIBLE PAVEMENT FAILURE

Asphalt pavement failure is a complicated phenomenon. It is a result of

cumulative damage in different pavement layer (Qudais, 2005). Nowadays, asphalt

pavement. Nowadays, asphalt pavement has to sustain increasingly large loads. When

these loads are combined with adverse environmental conditions, the distress modes in

pavements lead to the rapid deterioration of road structures (Vlachovocova,2005).

Flexible pavement is facing the risk of failure in form of rutting (permanent

deformation), fatigue cracking and thermal cracking. Indirect Tensile Strength test is to

evaluate the asphalt mixture performance.

I

The permanent deformation or rutting in the asphalt pavement is one of the

main reason cause the pavement damage. The permanent deformation in pavement has

long been recognized to include two different modes which is compactive deformation

(consolidation of layer) and plastic deformation (asphalt shear flow) (Huang, 1996;

Gokhale et al.1, 2005).

Thermal cracking is the cracking in flexible pavement due to cold temperature

cycling is commonly referred to as thermal cracks. Thermal cracks typically appear, as transverse cracks on the pavement surface roughly perpendicular to the pavement

centerline. In addition, these cracks can be caused by shrinkage of the HrvIA surface due

to low temperatures, hardening of the asphalt, and daily temperature cycles. Low

temperature cracking is associated with regions of extreme cold whereas thermal fatigue

cracking is associated with regions that experience large extremes in daily and seasonal

temperatures.

Besides, there are two types of non-load related thermal cracks which are

transverse cracking and block cracking. The transverse cracks usually occur first and are

followed by the occurrence of block cracking is the type that is predicted by models in

this design guide, while the block cracking is handled by material and construction

variables (Ara,2004).

Stiffness is the important mechanical characteristic of unbound materials in

pavements and the relative stiffness of the various layers dictate the distribution of

stresses and strains within the pavement system. Besides, the stiffness of the subgrade

and unbound base layer is influence the horizontal tensile strain at the bottom of the

asphalt and the compressive vertical strain at the top of the subgrade for a simple three-

layer flexible pavement system and those parameters are directly related to the

performance of the asphalt fatigue and subgrade rutting. The preferred method use for

characterizing the stiffness is the resilient modulus MR which is defined as the

unloading modulus in cyclic loading for unbound pavement. In 1986, the AASTHO

Design Guides have recommended the resilient modulus for characterizing subgrade

support for determining structural layer coefficients for flexible pavements.

12

Fatigue cracking of flexible pavement is due to horizontal tensile strain at the

bottom of the asphaltic concrete. It is commonly referred to as "bottom-up" or "classical" fatigue cracking. The cracks most likely initiate from the top in areas of high

localized tensile stresses resulting from tire-pavement interaction and asphalt binder

aging (top-dowri cracking) in thick pavement. Besides, the longitudinal cracks connect

forming many sided sharp-angled pieces that develop into a pattern resembling the back

of an alligator or crocodile after the repeated loading. The early stage of fatigue

cracking on the flexible pavement is shown in Figure 2.1 and types of fatigue in Figure

2.2.

Figure 2.1: Fatigue cracking formation,

Source: Halifax NS, October 29, 2013