binder characterization and performance of warm...

BINDER CHARACTERIZATION AND PERFORMANCE OF WARM STONE

MASTIC ASPHALT MIXTURE

SULEIMAN ARAFAT YERO

A thesis submitted in fulfilment of the

requirements for the award of the degree of

Doctor of Philosophy (Civil Engineering)

Faculty of Civil Engineering

Universiti Teknologi Malaysia

MARCH 2012

iii

“I dedicated this thesis to my late father, Amb. Suleiman Yero and late

mother, Hajia Fatima Babagana, and to my be loved family for their

awesome support and patience”

iv

ACKNOWLEDGEMENTS

Alhamdulillahirabbil’alamiin, Innalhamdalillah nahmaduhu wa nasta-’iynuhu.

In the course of this study, I wish to acknowledge the contribution and

understanding of my supervisor, Associate Professor Dr. Mohd. Rosli Hainin, for his

thoughts, guidance, criticism, encouragement, and friendship. I wish to express my

sincere appreciation to my co-supervisor late Associate Professor Dr. Abdul Aziz

Chik for his cooperation, advice and motivation which he gave even when on bed

and may ALLAH reward with him Aljannah Firdaus..

I wish to forward my great appreciation to the Ministry of Higher Education

Malaysia through the Malaysian Technical Cooperation Scholarship Scheme

(MTCP) that funded this research and made the study possible to me as an

international student.

I would also like to express my profound gratitude to all the technicians in

Transportation Laboratories of Civil Engineering Faculty of Universiti Teknologi

Malaysia and Universiti Tun Hussein Onn Malaysia for their help and cooperation.

Very special thanks are given to my beloved family for their patience, prayers and

understanding through the study period.

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ABSTRACT

The conventional stone mastic asphalt (SMA) is normally produced at high temperature (180oC) that consumes fuel, increases cost, and generates heat with emissions of green house gases. This study investigated the potential of producing stone mastic asphalt at lower temperature (130oC) termed as warm stone mastic asphalt (WSMA) against the normal high mixing temperature. Three grades of bitumen 80/100, 60/70 and PG 76-22 were investigated. A long chain aliphatic hydrocarbon Sasobit wax (SW) was used as an additive to reduce the mixing temperature. The Sasobit wax was incorporated at 0.5%, 1%, 1.5%, 2%, 2.5% and 3% of bitumen content. The empirical tests were conducted on 105 samples of the three binder types, which include penetration test at 10oC and 25oC. Softening point test, dynamic viscosity (DV) at 135oC and kinematic viscosity (KV) at 60oC were conducted to determine the penetration index (PI) and penetration viscosity number (PVN). The results indicate the modified bitumen has better resistance to temperature susceptibility with the additive and better resistance to rutting as it decreases the viscosity of the binder at high temperatures and produces high stiffness modulus as compared to the base bitumen. The study also investigated 126 samples for rheology test of the bitumen using the rolling thin film oven test (RTFOT), pressure aging vessel (PAV), and dynamic shear rheometer (DSR). The results from these tests at high test temperature indicate higher complex shear modulus (G*/sinδ) with low phase angle (increase stiffness) for aged modified binders indicating better resistance to rutting damage, while at low test temperature they exhibit low complex modulus with high phase angle (decrease stiffness) indicating better resistance to fatigue. The testing on the compatibility and morphology of the modified binders using the scanning electron microscopy test (SEM) were also conducted. The results show the homogeneity of the binder with Sasobit as is completely soluble in the binder with no agglomeration. The study investigated the effect of the warm asphalt additive on the binder aging using Fourier transformation infrared test (FTIR). The results show an insignificant impact on the binder aging. The study prepared and investigated 225 samples of SMA14 and WSMA14 mixtures using the Marshall mix design. The flow and stability tests conducted on the WSMA mixtures show values higher than the minimum JKR/SPJ/2008-S4 specification for SMA in Malaysia with less than 2.5% Sasobit in the three binder sourced investigated. The study recommends up to 2% Sasobit for PEN 80/100, up to 1.5% for PEN 60/70 and 1% for PG 76-22. Based on the penetration test conducted, the two modified PEN bitumen can be categorized as PG 76-22. Also the performance test on the asphalt mix with Sasobit that include rutting and resilient modulus test indicated resistance to rutting damage. Thus, it can be concluded that the Sasobit wax improves bitumen performance, decreases asphalt production temperatures and is feasible to be used in the production of WSMA.

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ABSTRAK

Stone mastic asphalt (SMA) konvensional dihasilkan pada suhu campuran yang tinggi iaitu 180oC. Ini akan mengakibatkan peningkatan penggunaan bahan api, penghasilan haba dan pelepasan gas rumah hijau. Kajian ini dijalankan untuk mengkaji potensi penghasilan stone mastic asphalt pada suhu campuran yang lebih rendah berbanding suhu campuran normal iaitu 130oC. Campuran ini dinamakan warm stone mastic asphalt (WSMA). Tiga gred bitumen digunakan dalam kajian ini iaitu gred 80/100, 60/70 dan PG 76-22. Rantaian panjang alifatik hidrokarbon lilin Sasobit wax (SW) digunakan sebagai bahan tambah untuk mengurangkan suhu campuran. Lilin Sasobit dicampukan pada kadar 0.5%, 1%, 1.5%, 2%, 2.5% dan 3% daripada kandungan bitumen. Ujian-ujian empirical telah dijalankan ke atas 105 sampel yang mewakili ketiga-tiga jenis bitumen tersebut. Ujian-ujian yang dijalankan adalah ujian penusukan pada suhu 10oC dan 25oC, ujian titik lembut, ujian kelikatan dinamik (DV) pada suhu 135 oC dan kelikatan kinematik (KV) pada suhu 60 oC yang bertujuan untuk mementukan indeks penusukan (PI) dan nombor kelikatan penusukan (PVN). Keputusan menunjukkan bitumen yang diubahsuai dengan bahan tambah mempunyai rintangan yang lebih baik terhadap suhu dan perpalohan. Ini disebabkan bahan tambah tesebut dapat mengurangkan kelikatan pengikat pada suhu tinggi dan menghasilkan modulus kekerasan yang tinggi berbanding bitumen asas. Ujian-ujian reologi turut dijalankan ke atas 126 sampel bitumen yang melibatkan ujian Rolling Thin Film Oven (RTFOT), Pressure Aging Vessel (PAV), dan Dynamic Shear Rheometer (DSR). Keputusan ujian bagi pengikat tua (aged binder) pada suhu tinggi menunjukkan modulus ricih kompleks (G*/sinδ) yang tinggi dengan sudut fasa yang rendah (kekerasan meningkat). Ini menunjukkan rintangan yang lebih baik terhadap perpalohan. Manakala, ujian pada suhu rendah mencatatkan modulus ricih kompleks yang rendah dengan sudut fasa yang tinggi (kekerasan menurun). Ini menunjukkan rintangan yang lebih baik terhadap kelesuan (fatigue). Ujian kesesuaian dan morfologi ke atas pengikat diubahsuai turut dijalankan dengan menggunakan ujian pengimbasan mikroskopi electron (SEM). Keputusan ujian menunjukkan keseragaman pengikat dan Sasobit di mana Sasobit larut di dalam pengikat tanpa ada penggumpalan. Selain itu, kajian kesan penuaan pengikat terhadap bahan tambah asfal sederhana panas (warm asphalt) dengan menggunakan ujian transformasi inframerah fourier (FTIR). Keputusan ujian menunjukkan kesan yang tidak ketara pada penuaan pengikat. Kajian terhadap 225 sampel SMA14 dan WSMA14 menggunakan rekabentuk Marshall turut dijalan. Keputusan ujian aliran dan kestabilan menunjukkan campuran WSMA diubahsuai bagi ketiga-tiga jenis bitumen dengan 2.5% Sasobit masing-masing mematuhi spesifikasi JKR/SPJ/2008-S4. Kajian ini mencadangkan 2% Sasobit untuk bitumen 80/100 PEN, 1.5% untuk bitumen 60/70 PEN dan 1% untuk bitumen PG 76-22. Ujian prestasi terhadap perpalohan dan resilient modulus bagi campuran diubahsuai ini menunjukkan campuran ini mematuhi spesifikasi yang telah ditetapkan. Kesimpulan dari kajian ini membuktikan lilin Sasobit dapat meningkatkan prestasi bitumen, mengurangkan suhu campuran asphalt dan boleh dipraktikkan dalam penghasilan WSMA.

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TABLE OF CONTENT

CHAPTER

TITLE PAGE

DECLARATION ii

DEDICATION iii

ACKNOWLEDGEMENT iv

ABSTRACT v

ABSTRAK vi

TABLE OF CONTENT vii

LIST OF TABLES xii

LIST OF FIGURES xiv

LIST OF SYMBOL AND ABBREVIATION xvii

LIST OF APPENDIX xx

1 INTRODUCTION 1

1.1 Background 1

1.2 Statement problem 5

1.3 The Objective of the research 5

1.4 Scope of the study 6

1.5 Significance of the study 7

2 LITERATURE REVIEW 8

2.1 Introduction 8

2.2 Bitumen 9

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2.3 Bitumen modification 11

2.4 Asphalt concrete technology 12

2.5 Warm mix asphalt 13

2.5.1 Warm mix asphalt additives 15

2.5.2 Organic additives 15

2.5.2.1 Commercial wax 16

2.5.3 Chemical additives 20

2.5.4 Foaming process 21

2.5.5 Advantages of WMA 23

2.5.6 Disadvantages of WMA 24

2.5.7 WMA studies 24

2.5.8 WMA field trials 27

2.6 Asphalt concrete mixtures 27

2.6.1 Open graded mix 28

2.6.2 Gap graded mix 30

2.6.3 Dense graded mix 32

2.7 History of SMA 33

2.7.1 SMA mixture 34

2.7.1.1 SMA aggregate characteristics 39

2.7.1.2 Advantages of SMA mixture 40

2.7.1.3 Disadvantages of SMA mixture 41

2.7.2 Mixtures overview 42

2.8 Mix design 43

2.8.1 Marshall mix design 43

2.8.2 Superpave mix design 44

2.8.3 Superpave binder tests 46

2.8.3.1 Rolling Thin Film Oven (RTFO) 47

2.8.3.2 Pressure Aging Vessels (PAV) 47

2.8.3.3 Dynamic shear rheometer (DSR) 47

2.8.3.4 Rotational Viscometer (RV) 50

2.9 Temperature Susceptibility 51

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2.9.1 Penetration Index (PI) 51

2.9.2 Penetration-viscosity Number (PVN) 53

2.9.3 Permanent deformation 56

2.9.4 Rutting damage 57

2.9.5 Fatigue cracking 58

2.10 Performance test for HMA Mixtures 59

2.10.1 Resilient Modulus (MR) 60

2.10.2 Wheel tracker 63

2.11 Summary of Chapter 2 63

3 RESEARCH DESIGN AND METHODOLOGY 65

3.1 Introduction

3.2 Test procedures

65

66

3.2.1 Aggregate characterization 72

3.2.1.1 Sieve analysis 72

3.2.1.2 Mineral filler 73

3.2.1.3 Aggregate gradation 73

3.2.1.4 Flakiness 74

3.2.1.5 Elongation 75

3.3 Bitumen characterization 75

3.3.1 Penetration test 75

3.3.2 Softening point test 76

3.3.3 Viscosity 76

3.3.4 Short-term Aging RTFO test 77

3.3.5 Long-term Aging PAV test 78

3.3.6 Dynamic shear rheometer (DSR) test 80

3.3.7 FTIR test 84

3.3.8 SEM test 85

3.3.9 Storage Stability test 86

x

3.4 Stone Mastic Asphalt (SMA14) mixture 87

3.5 Indirect tensile resilient modulus test 88

3.6 Wheel tracking test 91

3.7 Marshall stability and flow test 94

3.8 Volumetric calculations 97

3.9 Draindown test 100

4 RESULTS AND DISCUSSION 101

4.1 Introduction 101

4.2 Stage1:Materials characterization 102

4.2.1 Aggregate properties 102

4.3 Binder properties 103

4.3.1 Binder penetration test 103

4.3.2 Softening point test 106

4.3.3 Viscosity test 108

4.4 Rheological properties (DSR) test 111

4.4.1 Rutting factor 111

4.4.2 Fatigue factor 115

4.5 FTIR test 118

4.6 Storage stability test 120

4.7 SEM Test 122

4.8 Stage two: Marshall mix design 123

4.8.1 Determination of OBC 124

4.8.2 Marshall stability and flow 126

4.9 Stage three: Performance tests 127

4.9.1 Rutting resistance test 127

4.9.2 Resilient modulus test 130

4.9.3 Drain-down test 134

4.10 Summary of results 135

5 CONCLUSION AND RECOMMENDATION 136

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5.1 Introduction 136

5.2 Conclusion 139

5.3 Recommendation 140

REFERENCES 142

Appendices A-G 149 - 225

xii

LIST OF TABLES

TABLE NO. TITLE PAGE

2.1 Porous asphalt gradation specification 29

2.2 Typical SMA gradation specification 31

2.3 Typical dense gradation requirements for asphalt concrete 33

2.4 Gradation limits of combined aggregates for SMA 36

2.5 Malaysian specification for road works requirement for

SMA mix

38

2.6 Coarse aggregate quality requirements 39

2.7 Fine aggregate quality requirements 40

2.8 Superpave bitumen binder testing equipment and purpose 46

3.1 Gradation limits of combined aggregates for SMA14 74

3.2 Indirect tensile resilient modulus test parameter 90

3.3 Marshall mixture JKR criteria for SMA 95

4.1 Analyzed aggregate test results 102

4.2 Binder properties 103

4.3 Regression model for binders penetration 105

4.4 Regression model for binders softening point 107

4.5 Statistical regression model for viscosity 110

4.6 Regression model for binders rutting modulus- G*/sin δ 114

4.7 Statistical regression model for DSR G*sin δ 117

4.8 a.b.c Stability test 121

4.9 Regression model for Marshall stability 126

4.10 Rut depth test at 50oC 127

4.11 Rut depth test at 60oC 128

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4.12 Regression model for rutting at 50oC 129

4.13 Regression model for rutting at 60oC 130

4.14 Statistical regression model for resilient modulus test at

loading frequency 0.5 GHz

133

4.15 Statistical regression model for resilient modulus test at

loading frequency 1 GHz

134

4.16 Drain-down table 135

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LIST OF FIGURES

FIGURE NO. TITLE PAGE

2.1 Typical visco-elastic behaviour of bitumen 11

2.2 Typical mixing temperature range for asphalt 12

2.3 Sasobit pellets 19

2.4 Physical states of grading mixtures 28

2.5 Surface of open graded mix 29

2.6 Gap graded cross section 31

2.7 Gap graded sample 32

2.8 Comparison between SMA vs. conventional HMA 35

2.9 SMA aggregate skeleton 36

2.10 Typical composition of SMA 37

2.11 Rutting on pavement surface layer 38

2.12 Various grading curves 42

2.13 Viscous and elastic behavior of the bitumen 49

2.14 Components of complex modulus |G*| 50

2.15 Nomograph to determine penetration index 53

2.16 Chart for approximate values of PVN for bitumen 55

2.17 Fatigue cracking 59

2.18 a.b Indirect tensile test (ITT) during loading and ITT at failure 61

3.1 Stage one flow chart 68

3.2 Stage two flow chart 69

3.3 Stage two flow chart 71

3.4 Brookfield thermosel viscometer 77

3.5 RTFOT Machine 78

3.6 Dester PAV machine 79

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3.7 Configuration of PAV 80

3.8 HAAKE dynamic shear rheometer test device 81

3.9 Rheometer slice kit 81

3.10 Principle of dynamic shear rheometer test 82

3.11 Dynamic shear rheometer geometry 83

3.12 Perkin Elmer spectrometer 85

3.13 JEOL scaning electron microscopy 86

3.14 Automatic compactor hammer 88

3.15 Indirect tensile resilient modulus test 91

3.16 Schematic diagram of resilient 91

3.17 WESSEX wheel tracking testing machine 93

3.18 Schematic diagram of the wheel tracking device 93

3.19 Wheel track Sample 94

3.20 Water bath for submerging samples 96

3.21 Machine for flow and stability test 97

3.22 Volumetric properties of HMA 98

3.23 Drain down test apparatus 100

4.1 Bitumen penetration at 25°C 104

4.2 Softening point of B1, B2 and B3 106

4.3 Bitumen viscosity at 135°C 108

4.4 Temperature-viscosity relationship, graph 109

4.5 Rutting modulus- G*/sin δ, for binder B1 112



4.8 Fatigue modulus-G*sin δ, at 25 oC for binders B1, B2,and B3 115

4.9a

4.9b

FTIR absorbance of the binders at 680 cm-1 unaged

FTIR absorbance of the binders at 680 cm-1 aged

118

119

4.10a

4.10b

FTIR absorbance of the binders at 1600 cm-1 unaged

FTIR absorbance of the binders at 1600 cm-1 aged

119

120

4.11a.b.c SEM for base binder 122

4.11d.e.f SEM for binder + Sasobit 123

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4.12a.b.c.d Marshall stability, flow, specific gravity and voids 125

4.13 Rutting comparison at various temperatures 128

4.14 MR comparison at various temperatures with loading

frequency 0.5 GHz

131

4.15 MR comparison at various temperatures with loading

frequency 1 GHz

132

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LIST OF SYMBOLS AND ABBREVIATION

AAPA Australian Asphalt Pavement Association

AASHTO American Association of State Highway and Transport

Officials

AC Asphaltic concrete

ASTM American Society for Testing and Material

BBR Bending Beam Rheometer

BS British Standard oC Celsius, Centigrade

Cc Coeffient of confidence

cm centi metre

Cp centi poise

Cst centi stokes

dmm decimillimetre

DGA Dense graded asphalt mix

DSR Dynamic Shear Rheometer

G*.sin δ fatigue factor

g gram

HMA Hot-Mix Asphalt

GHz Giga hertz

Gmb

Gmm

Bulk specific gravity

Maximum theoretical specific gravity

G* Complex shear modulus

JKR Jabatan Kerja Raya (Public Works Department)

km kilometre

xviii

kN kilo Newton

kPa kilo Pascal

m meter

MRD Mean rut depth

MMS Mean Marshall stability

mg milligram

min minutes

ml millilitre

MPa Mega Pascal

mN milli-Newton

MR resilient modulus

ms milli seconds

NAASRA National Association of Australian State Road Authorities

NCAT National Center for Asphalt Technology

NAPA National Asphalt Paving Association

N Newton

OBC Optimum bitumen content

P Pressure

PA Porous Asphalt

PG Performance Grade

Pa.s Pascal seconds

δ Phase angle

PI Penetration Index

PVN Penetration-viscosity number

R Coefficient of correlation

R2 R-square = coefficient of determination

rad radian

rpm revolution per minute

G*/sin δ rut factor

s seconds

SW Sasobit wax

xix

SE Standard error

SSD Saturated-surface-dry

SMA14 Stone Mastic Asphalt with nominal maximum aggregate

size of 12.5mm

SGcoarse Bulk specific gravity of coarse aggregate

SGfiller Bulk specific gravity of mineral filler

SGfine Bulk specific gravity of fine aggregate

SG specific gravity

SMA Stone Mastic Asphalt

TMD Theoretical maximum density

UTM Universiti Teknologi Malaysia

UTHM Universiti Tun Hussein Onn Malaysia

VFB Voids filled with bitumen

VMA Voids in mineral aggregate

VTM (Va) Voids in total mix

WA Water absorption

WMA Warm mix aspalt

WSMA Warm stone mastic asphalt

xx

LIST OF APPENDIX APPENDIX TITLE PAGE

A1-1 Flaskiness and elongation test 149

A1-2 Flakiness and elongation index 150

A1-3 LA abrasion test 151

A1-4 Specific gravity for coarse aggregate 152

A1-5 Specific gravity for fine aggregate 153

B1-1 Penetration test 154

B1-2 Softening point test 154

B1-3 Viscosity test 154

B2-1 Combine average penetration, softening point

and viscosity

155

B3-1 Fatigue factor 156

B4-1-6 Rut factor 157

B5-1 FTIR 680 cm-1 163

B5-2 FTIR 1600 cm-1 164

C1-1 Aggregate size distribution 165

C1-2 Marshall OBC table 166

D1-1 Marshall flow and stability result 167

D2-1-2 Resilient modulus result 168

D3-1-12

E

Rut depth result

FTIR charts

169

181

F Summary of statistical data analysis 189

G MR graphs 208

CHAPTER I

INTRODUCTION

1.1 Background

The history of transportation, either by land, sea, or air is as old as the human

civilization. The road transportation has been the main means of transporting goods

and services over years all over the world and can be related to the history of

mankind. The Romans started the design and construction of the ancient roads that

transform to the current asphalt technology. The pavement transformation from

localize concept to the progressive roadway materials and construction procedures

practice in countries all over the world to provide travel path. In a developing nation

like Malaysia with over 91,620 km roads [1], these roads are the major means of

transportation, and they are constructed based on regulated procedures provided by

the Public Works Department of Malaysia (PWD). Some developed countries like the

United State of America with effective means of transportation, has highway

spanning over 4.02 million km of pavement [2].

Basically the road pavement can be divided into flexible and rigid, the flexible

pavement comprises layers of sub-base, road base and the wearing course, which are

made up of bitumen and aggregate. While the rigid pavement is mostly constructed

with reinforced concrete and not widely used in the road transportation system.

2

In a country like Malaysia only 3,651 km (3.99%) of the paved roads are

made of rigid pavement, while the flexible pavements make up to 87,626 km

(95.64%)[1]. These flexible pavements are mostly constructed using the conventional

hot mix asphalt (HMA) technology at high mixing (160oC) and compaction (140oC)

temperatures [3].

.

The HMA is mainly used as the paving material, it consists of aggregate and

bitumen (binder), which are heated and mixed together. The process of producing the

HMA involves heating the binder to a high temperature before mixing with the

aggregate, hot mix asphalt concrete composed of two components: binder and

aggregate. About 94 – 96% by weight of the mix consists of aggregate, and the

remaining 4 – 6% by weight consists of binder [3]. Although the percentage of the

binder is relatively small, the asphalt binder influences pavement performance more

than the aggregate as environmental factors, such as high temperature due to solar

radiation, affects the binder more than the aggregate.

In Malaysia the adoption of the stone mastic asphalt (SMA) is in its early

stage, and is considered to be a pavement with good resistance properties to rutting

damage. The SMA pavement is sometimes called Stone Matrix Asphalt in most

European countries. SMA is a design pavement developed in the 1980s in Europe as

an impervious wearing surface to provide resistance to rut and durable pavement

surface. Stone mastic asphalt was introduced to resist studded tires effects rather than

other type of hot mix asphalt in most European countries [4].

The design of the SMA surfacing is basically to resist deformation particularly

rutting and maximize durability by using a stone-on-stone skeleton. The SMA

consists of high stone content and the voids of the structural matrix filled with viscous

bitumen matrix. SMA has high stone content of at least 70%, with good stone-on-

stone contact after compaction. The required degree of matrix stiffness is achieved

through the addition of crushed sand [4]. The SMA stone-on-stone contact skeleton

significantly reduces rutting. The aggregate skeleton in SMA is all in contact, and

hence the resistance to rut damage by the pavement depends on the aggregate

3

interlock properties rather than the binder properties. Since under loading the bitumen

deform more than the aggregate [4].

There are several types of polymers used in asphalt binders today, currently,

the most commonly used polymer for bitumen modification is the styrene butadiene

styrene (SBS) followed by other polymers such as crumb rubber, styrene butadiene

rubber (SBR), ethylene vinyl acetate (EVA) and polyethylene [4]. SBS behaves like

elastic rubbers at ambient temperature and it can be processed like plastics when

heated (thermoplastic elastomer).

The various studies conducted on the use of polymer modification in bitumen

(PMB) used in paving indicated great improvement in the performance of the

modified binders, though possible problems can occur during paving operations. In

general, asphalt mixtures produced with PMB binders are normally mixed and

compacted at a higher temperature (1800C), because of their high viscosity properties,

than conventional mixtures. Furthermore, the polymers can be destroyed by the

temperature being too high during mixing or by being held at an elevated temperature

for a long period of time after mixing [5].

However, with lower mixing and compaction temperatures, the PMB

mixtures might result in several problems such as inadequate volumetric properties

(i.e., high air voids) and poor short-term and long-term performance. The high mixing

temperature could result to health problems described by some road crews in

Australia, presumably caused by the fumes, included vomiting, nausea, headaches,

sore throats and sore eyes. Most of the problems were observed to be experienced

when the SBS was used as a modifier [6].

The HMA mixture is classified into dense graded mixes such as asphalt

concrete wearing (ACW), gap graded stone mastic asphalt, and open graded mixes

include porous asphalt (PA). The SMA mixtures in Malaysia are produced using the

conventional HMA process but at a higher mixing and compaction temperatures of

1800C and 1500C respectively, based on the Public Works Department of Malaysia

(PWD).

4

The conventional process of producing SMA generates heat, emission and

the primary source of emission in asphalt process is the mixers, dryers and hot bins

that emit particulate matter such as dust, smoke, and exhaust vapour and other

gaseous pollutant. The emissions contain substances such as reactive organic gases

(ROGs) and particulate matter (PM). The ROGs emitted involve a wide cross section

of contaminants including volatile organic compounds (VOCs) and semi-volatile

organic compounds (SVOC's) including polynuclear aromatic hydrocarbons (PAHs),

aromatics and aliphatic. They (ROGs) also play a key role in smog formation and

visibility degradation [7]. Particulate matters (PM) often referred to as aerosols, are of

particle sizes fewer than 2.5 to 10 microns and are often adhered to by ROGs. These

particles affect air quality because they can be irreversibly trapped in the pulmonary

tract, and also a source of pollution.

The sustainability, of the environment is of major concern these days, and it

involves the creation and maintenance of conditions under which humans and nature

can exist harmoniously, while fulfilling social and economical requirements. These

requirements include the reduction of emissions and the alleviation of its effects on

human health and the environment. The modification of bitumen and different asphalt

mixing procedures has been studied and practiced for ages but the current

environmental policies renewed interest in proffering for green and sustainable

pavements [8], and this could be attributed to the following;

- Reduction of emission in green house gases

- Reduction in the release of particulate dust

- Increasing a better performance of pavement

- High cost of fuel globally

- Improve workability

- Longer haulage distance opportunities

- Conducive working environment

5

1.2 Problem Statement

The SMA mixtures are normally designed to provide pavement with good

resistance to rutting, with high coarse aggregate content, fines and modified binder.

The stone mastic asphalt is normally produced using the conventional HMA

procedure at high temperature (1800C) and also compacted at high temperature

(1500C). This generates heat, consumes fuel, emits greenhouse gases that affects the

environment and also makes the working environment very unfriendly. As the

production of SMA consist of the use of polymer modified binders such as PG 76-22

that arise from the high temperature demands and fume emissions during operations

(i.e., mixing and compaction). These issues involve possible effects on human health,

a negative environmental impact and the increased fuel costs. Recently, the new

warm mix asphalt (WMA) technology has been used to alleviate some of these

problems. Previous researches conducted reviewed SMA mixtures using the HMA

process. Hence there is a need to study and investigate a more sustainable process for

SMA using the WMA technology at a relatively low temperature with less heat, less

emissions and at a relatively low cost without compromising its quality.

1.3 Objective of the research

This study has the following objectives;

(a) To evaluate the rheological and mechanical properties of bitumen modified

with and without the additive Sasobit wax.

(b) To investigate the negative effect of aging on the modified binders during

mixing.

(c) To investigate stability of the additive with bitumen at storage and the

morphology of the mixture.

(d) To determine the performance of warm stone mastic asphalt (WSMA) with

respect to resistance to binder fatigue and plastic deformation.

6

1.4 Scope of the research

This study involved the use of a commercial additive Sasobit wax with

bitumen and extensive laboratory testing. The research included empirical tests for

the penetration and softening point for both neat and modified bitumen of 80/100

penetration grade, 60/70 penetration grade and PG 76–22. Determination of the effect

of temperature on the viscosity of the binder with and without the additive by

measuring the viscosity at varying temperatures. The study investigated the

rheological properties of the binder with and without the warm mixes additive, and

the effect of the increase and reduction of the complex modulus and phase angle. The

study also evaluated the effect of aging on the binder by using the rolling thin film

test (RTFOT) and pressure-aging vessel (PAV) tests were with, a total of 505 no.

binder samples investigated.

The study utilized Fourier transform infrared spectroscopy test (FTIR), to

evaluate the WMA binders and their aging properties. The study involved the

production of warm stone mastic asphalt (WSMA) at a lower temperature of 135oC

compared with the SMA at 180oC. The warm stone mastic asphalt samples with

nominal maximum aggregate size (NMAS) of 12.5 mm (designated as SMA14) were

studied.

In designing mixtures, the total of 225 specimens were prepared using

Marshall compaction method with three specimens for each of bitumen content of

5.0%, 5.5%, 6.0%, 6.5%, and 7.0% with Sasobit wax content of 0%, 0.5%, 1%, 1.5%,

2%, 2.5% and 3% by Marshall hammer at compaction efforts of 50 blows per face

including nine specimens designed for binder drain down test purpose. The indirect

tensile resilient modulus of the asphalt concrete was tested. The study investigated 12

SMA14 and WSMA14 samples using the WESSEX wheel tracker to determine the

rutting potential of the WMA at high temperatures. All the data obtained from the

study were analyzed and presented accordingly. All the testing was performed at the

UTM Transportation Laboratory except for the dynamic shear rheometer test, which

was conducted at the Highway Laboratory of Universiti Tun Hussein Malaysia

(UTHM).

7

1.5 Significance of the research

This research shall improve on the industrial process of SMA mixtures, laying

and compaction at a relatively lower temperature. The study is expected to improve

three areas of pavement performance, namely, controlling rutting, fatigue cracking

and aging. The study shall also provide a better environmental friendly method of

producing asphalt mixture, which complies with the 1997, Kyoto protocol on

stemming global warming and depletion of the Ozone layer. The study could provide

valuable information towards understanding the WMA technology to agencies that

desire to construct SMA pavements using the WMA technology in developing

countries like Malaysia.

143

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