the aggregate degradation characteristics of...

THE AGGREGATE DEGRADATION CHARACTERISTICS OF STONE MASTIC

ASPHALT (SMA) MIXTURES

NORLIZA BINTI MOHD AKHIR

A project report submitted in partial fulfillment of the

requirements for the award of the degree of

Master of Engineering (Civil - Transportation and Highway)

Faculty of Civil Engineering

Universiti Teknologi Malaysia

NOVEMBER 2006

iii

“Dedicated to my beloved father, Mohd Akhir and mother, Musalmiah,

my sisters, Mafizah, Fadilah, Sakinah and Norazalia,

my brothers, Mohd Shahizan and Mohd Saifuddin,

and to a special person…

for their love, support and patience are awesome”

“Also not forgotten to all my colleagues,

Elizabeth, Zanariah, Masyitah, Nordiana and Norhidayah,

for their assistance and encouragements towards the success of this study”

iv

ACKNOWLEDGEMENT

In the name of Allah S.W.T, I would like to express my gratefulness to Him

for giving me strength to finish my project. In preparing this project report, I was in

contact with many people who have contributed towards my understanding and

thoughts.

I wish to express my sincere appreciation to my main project supervisor, Dr.

Mohd Rosli bin Hainin, for encouragement, guidance and critics. I am also very

thankful to my co-supervisor, Tn. Hj. Che Ros bin Ismail, for his guidance, advices

and motivation. Without their continued support and interest, this project report

would not have been the same as presented here.

I am also indebted to all staffs of Highway and Transportation Laboratory of

UTM, Mr. Abdul Rahman, Mr. Suhaimi, Mr. Azman and Mr. Ahmad Adin, for their

assistance and helpfulness during my project laboratory work. Special thanks also to

Mr. Zaini, from Hanson Quarry Product for supplying me the project laboratory

materials.

My fellow postgraduate students should also be recognized for their support.

My sincere appreciation also extends to all my colleagues and others who have

provided assistance at various occasions. Their views and tips are useful indeed.

Unfortunately, it is not possible to list all of them in this limited space.

v

ABSTRACT

Stone Mastic Asphalt (SMA) mixtures are designed to have a high coarse

aggregate content and stone-on-stone contact which results in more stress on the

coarse aggregate particles during compaction and traffic loads. For that reason,

aggregates tend to break down more in SMA mixtures than in conventional dense-

graded mixtures. Aggregate degradation during compaction and traffic loading may

cause changes in the original gradation and thus may also affect the volumetric

parameters of SMA mixtures. The main objective of this study was to determine the

degree of aggregates degradation in SMA mixtures due to compaction process.

Aggregates with two Nominal Maximum Aggregates Size (NMAS) which

designated as SMA14 and SMA20 were compacted using the effort of 50 blows of

Marshall Hammer and 100 gyrations of Superpave Gyratory Compactor (SGC). The

verified samples were then prepared and extracted using Centrifuge Method. The

same procedure was also performed for the cored samples. The comparisons of

gradation of cored samples with the laboratory samples were evaluated to examine

the aggregate degradation with respect to different compaction efforts. The

relationship between aggregate degradation and influencing factor such as

compaction efforts, and volumetric properties were investigated. Aggregate

degradation by the Marshall Hammer was found to be significantly higher than

degradation by the SGC. Voids in mineral aggregate (VMA) of either compaction

methods decrease or almost the same when aggregate degradation is not significant.

SGC methods can be selected to represent the field roller that result in similar trend

of aggregate degradation.

vi

ABSTRAK

Campuran Stone Mastic Asphalt (SMA) direka bentuk untuk mempunyai

kandungan aggregat kasar yang tinggi serta daya ikatan antara aggregat (stone-on-

stone contact). Aktiviti pemadatan di tapak dan pembebanan lalu lintas akan

memberikan tekanan terhadap partikel aggregat kasar tersebut. Oleh yang demikian,

aggregat di dalam campuran SMA lebih cenderung untuk pecah berbanding

campuran panas bergred tumpat biasa. Kesan ini menyebabkan perubahan

penggredan asal aggregat dan akhirnya mempengaruhi parameter volumetrik

campuran SMA. Objektif utama kajian ini ialah untuk menentukan tahap pecahan

aggregat di dalam campuran SMA yang disebabkan oleh proses pemadatan di

makmal. Dua saiz aggregat maksimum nominal (NMAS) yang direka bentuk

sebagai SMA14 dan SMA20 telah dipadat dengan 50 hentakan menggunakan Tukul

Marshall dan 100 putaran oleh Superpave Gyratory Compactor (SGC). Sampel-

sampel yang telah direka bentuk pada kandungan bitumen optimum disediakan dan

kemudiannya diekstrak dengan Kaedah Emparan. Prosedur sama turut dilakukan ke

atas sampel tebukan dari tapak. Perbandingan penggredan di antara sampel tebukan

dan makmal dinilai untuk menentukan pecahan aggregat terhadap kaedah pemadatan

yang berlainan. Hubungan di antara tahap pecahan aggregat dan faktor-faktor yang

mempengaruhi seperti jenis pemadatan, dan ciri-ciri volumetrik aggregat dikaji.

Hentakan Tukul Marshall didapati memecahkan aggregat lebih banyak berbanding

putaran oleh SGC. VMA bagi setiap kaedah pemadatan berkurang atau sama apabila

pemecahan aggregat tidak ketara. Kaedah SGC dipilih untuk mewakili pemadat

tapak kerana mempunyai ciri-ciri pemadatan yang sama seperti pemadat tapak.

vii

TABLE OF CONTENTS

CHAPTER TITLE PAGE

DECLARATION OF THE STATUS OF THESIS

SUPERVISOR’S DECLARATION

TITLE PAGE

DECLARATION ii

DEDICATION iii

ACKNOWLEDGEMENT iv

ABSTRACT v

ABSTRAK vi

TABLE OF CONTENTS vii

LIST OF TABLES xi

LIST OF FIGURES xii

LIST OF ABBREVIATIONS/SYMBOLS xiv

LIST OF APPENDICES xv

1 INTRODUCTION 1

1.1 Introduction 1

1.2 Problem Statement 2

1.3 Objectives of the Study 3

1.4 Scope of the Study 3

1.5 Importance of the Study 4

2 LITERATURE REVIEW 5

2.1 Introduction 5

2.2 History of SMA 6

viii

2.3 Advantages of SMA 8

2.4 Disadvantages of SMA 9

2.5 Composition of SMA 10

2.6 Aggregate Characteristics 11

2.6.1 Relative Density 13

2.6.2 Aggregate Hardness 13

2.6.3 Flat and Elongated Particles 14

2.7 Mortar 14

2.7.1 Asphalt Binder 15

2.7.2 Mineral Filler 15

2.7.3 Stabilizing Additives 16

2.8 Mixture Design Overview 17

2.9 Mix Design Method 18

2.9.1 Marshall Method 18

2.9.2 Superpave Mix Design 19

2.9.2.1 Superpave Laboratory

Compaction 19

3 METHODOLOGY 21

3.1 Introduction 21

3.2 Laboratory Work Procedure 22

3.3 Sieve Analysis 23

3.3.1 Dry Sieve Analysis (For Fine and

Coarse Aggregate) 23

3.3.2 Washed Sieve Analysis (For Mineral

Filler) 25

3.3.3 Aggregate Gradation 27

3.4 Determination of Specific Gravity for

Aggregate 27

3.4.1 Coarse Aggregate 28

3.4.2 Fine Aggregate 29

3.5 Marshall Mix Design Method 31

3.5.1 Procedure 31

3.5.2 Apparatus 31

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3.5.3 Marshall Specimen Preparation 32

3.5.4 Marshall Stability and Flow Tests 34

3.5.5 Theoretical Maximum Density

(TMD) Test 36

3.5.6 Analysis of Data 39

3.5.6.1 Analysis of Bulk Specific

Gravity 39

3.5.6.2 Analysis of Void in Mineral

Aggregate (VMA) 41

3.5.6.3 Analysis of Air Void in the

Compacted Mix (VIM) 41

3.5.6.4 Analysis of Void Filled with

Bitumen (VFB) 42

3.5.7 Determination of Optimum Bitumen

Content 42

3.6 Superpave Mix Design 43

3.6.1 Apparatus 43

3.6.2 Procedures 43

3.6.3 Sample Preparation 44

3.6.4 Determination of Optimum Bitumen

Content 45

3.7 Binder Draindown Test 46

3.7.1 Apparatus 47

3.7.2 Test Procedure 48

3.7.3 Calculation 48

3.8 Bitumen Extraction Test 49

3.8.1 Apparatus 49

3.8.2 Test Procedure 50

3.8.3 Sieve Analysis of Extracted Aggregate 51

4 RESULTS AND DISCUSSIONS 52

4.1 Introduction 52

4.2 Sieve Analyses 52

4.2.1 Aggregate Gradation 53

x

4.2.2 Wet Sieve Analysis 55

4.3 Specific Gravity of Aggregate 55

4.3.1 Coarse Aggregate 56

4.3.2 Fine Aggregate 56

4.3.3 Filler 56

4.3.4 Specific Gravity of Blended Aggregate 56

4.4 Specific Gravity of Bitumen 57

4.5 Marshall and Superpave Results 57

4.6 Binder Draindown Test Results 58

4.7 Extraction and Sieve Analysis 59

4.8 Aggregate Degradation 59

4.8.1 Aggregate Degradation by Compaction 59

4.8.2 Effect on Volumetric Properties 62

5 CONCLUSIONS AND RECOMMENDATIONS 63

5.1 Conclusions 63

5.2 Recommendations 64

REFERENCES 65

APPENDICES A – J 68-87

xi

LIST OF TABLES

TABLE NO. TITLE PAGE

2.1 Coarse aggregate quality requirements 12

2.2 Fine aggregate quality requirements 12

3.1 SMA mix requirements 22

3.2 Gradation limit for SMA 27

3.3 Minimum sample size requirement for maximum

theoretical specific gravity (ASTM D 2041) 38

3.4 Superpave gyratory compactive effort 45

4.1(a) Percentage aggregate passing on each sieve size

for SMA14 mix design 54

4.1 (b) Percentage aggregate passing on each sieve size

for SMA20 mix design 55

4.2 Bulk specific gravity of aggregate 57

4.3 Mix design results 58

4.4 Degradation results 61

xii

LIST OF FIGURES

FIGURE NO. TITLE PAGE

2.1 Comparisons between SMA and conventional HMA 5

2.2 SMA aggregate skeleton 6

2.3 Fat spots 9

2.4 Major components of SMA mixtures 10

2.5 Rutting on pavement surface layer 11

2.6 Various grading curves 17

3.1 Flow chart for SMA laboratory process 24

3.2 Mechanical sieve shaker 25

3.3 Automatic compactor hammer 33

3.4 Marshall compression testing machine 34

3.5 Water bath for submerging sample 35

3.6 Apparatus for TMD test 37

xiii

3.7 Apparatus for determination of bulk specific gravity 40

3.8 Superpave gyratory compactor 44

3.9 Draindown test apparatus 46

3.10 Dimension of wire basket 47

3.11 Bitumen extraction apparatus 50

4.1 (a) Gradation limit and design curve for SMA14 53

4.1 (b) Gradation limit and design curve for SMA20 54

4.2 (a) Gradation changes for SMA14 60

4.2 (b) Gradation changes for SMA20 60

xiv

LIST OF ABBREVIATIONS/SYMBOLS

SMA Stone Mastic Asphalt

NAPA National Asphalt Pavement Association

SHRP Strategic Highway Research Program

SGC Superpave Gyratory Compactor

NMAS Nominal Maximum Aggregate Size

SMA14 Stone Mastic Asphalt with Nominal Maximum Aggregate Size of

12.5mm

SMA20 Stone Mastic Asphalt with Nominal Maximum Aggregate Size of

19mm

HMA Hot Mix Asphalt

FHWA Federal Highway Administration

ESAL Equivalent Standard Axle Load

LAAV Los Angeles Abrasion Value

ASTM American Society for Testing and Materials

JKR Jabatan Kerja Raya

VIM Voids in Mix

VMA Voids in Mineral Aggregate

OBC Optimum Bitumen Content

NCAT National Center for Asphalt Technology

AASHTO American Association of State Highway and Transportation Officials

SSD Saturated-surface-dry

TMD Theoretical Maximum Density

VFB Voids Filled with Bitumen

Gmb Bulk specififc gravity of compacted mix

Gsb Combined bulk specific gravity of total aggregate

Gmm Theoretical maximum density

xv

LIST OF APPENDICES

APPENDIX TITLE PAGE

A Aggregate size distribution and

determination of filler 68

B Specific gravity for coarse aggregate, fine

aggregate and blended aggregate 70

C Marshall test results 73

D Theoretical maximum density 75

E Determination of OBC at 4% air voids 77

F Superpave test results 78

G Determination of OBC at 4% air voids 79

H Results of sieve analysis on extracted

aggregate (after compaction) 80

I1 The t-test paired comparing both laboratory

compaction method 81

I2 The t-test paired comparing both laboratory

compactor and the field roller (for SMA20) 82

xvi

J Photo for Laboratory Work 83

CHAPTER 1

INTRODUCTION

1.1 Introduction

Stone Mastic Asphalt (SMA), sometimes called Stone Mastic Asphalt

especially in Europe, is a gap-graded hot mix asphalt surfacing material (Pierce,

2000). SMA is an asphalt mixture initially developed in the 1980s in Europe as an

impervious wearing surface to provide rut resistant and durable pavement surface

layer. When SMA is first introduced in Europe, it is used in resisting the studded

tires effects rather than other type of hot mix asphalt (Roberts, Kandhal and Brown,

1996).

SMA is designed to resist deformation particularly rutting and maximize

durability by using as structural basis of stone-on-stone contact. SMA is

characterized by its high stone content and the voids of the structural matrix are filled

with high viscosity bituminous matrix. The high stone content of at least 70%

ensures stone-on-stone contact after compaction. The required degree of matrix

stiffness is achieved through the addition of crushed sand (Roberts, Kandhal and

Brown, 1996).

Because the aggregates are all in contact, rut resistance depends on aggregate

properties rather than asphalt binder properties. Since aggregates do not deform as

much as asphalt binder under load, this stone-on-stone contact significantly reduces

rutting. The SMA pavement offers other side benefits due to its high content of

2

coarse aggregate. SMA pavement surfaces are porous, thus reducing the

tire/pavement noise level as well as water spray and glare (NAPA, 1999).

However, SMA is generally more expensive than a typical dense-graded

HMA (about 20 - 25 percent) because it necessitates more durable aggregates, higher

asphalt content and typically, a modified asphalt binder and fibers (NAPA, 1999).

Durability was to be defined primarily through rutting and cracking measurements,

but was also to include other types of pavement deterioration (Schimiedlin and

Bischoff, 2002). In the right situations, it should be cost-effective because of its

performing better than the standard asphaltic concrete pavements in some important

areas, i.e., crack and distress generation thus increase rut resistance and improve

durability.

The mixture also entails higher mixing temperatures to provide greater

workability and longer mixing times at the plant due to the presence of modified

binder or mineral fiber ensuring proper distribution of the mineral fiber or adequate

coating of aggregates, and more intensive quality control at plant and on job site

(Watson and Jared, 1995). Based on its performance in term of durability and long

life service, the use of SMA is currently keep increasing in popularity among the

road authorities and the asphalt industry.

1.2 Problem Statement

SMA mixtures are designed to have high coarse aggregate content and stone-

to-stone contact which results in more stress on the coarse aggregate particles during

compaction and heavy traffic loads. As a result, the aggregates tend to degrade in

SMA mixtures than in conventional dense graded mixtures. Aggregate degradation

during compaction and heavy traffic loading may cause changes in the original

aggregate gradation, and thus may also affect the volumetric properties of SMA

mixtures.

Most work to date on SMA has been with Marshall Compactor but some

works needs to be done with a Gyratory Machine since the new SHRP gyratory will

3

eventually be used on SMA mixes. With the introduction of the Superpave system, it

is now significant for the mix designer who endeavoring to design stiffer, more rut-

resistant asphalt concrete pavements having the alternative of using the Superpave

Gyratory Compactor (SGC) for SMA mixtures.

The application of SMA is still new in Malaysia therefore the contractors had

little experience with this mixture at the time of construction. Since this study has

been done previously, but there has been little research conducted to relate with

Malaysia’s condition. Thus there is a need to study and determine the aggregate

degradation of SMA particularly experienced in Malaysia.

1.3 Objectives of the Study

The objectives of this study were:

a) to determine the degree of aggregate degradation in SMA mixtures during

the compaction process produced by 100 gyrations of the SGC and 50-

blow Marshall Hammer;

b) to determine the effect of the gradation changes on volumetric properties

of compacted SMA mixtures; and

c) to compare the aggregate degradation of compacted samples experienced

at field and laboratory.

1.4 Scope of the Study

The scope of the study focused on the effects of compaction methods and

aggregate gradation affecting the aggregate degradation in SMA. The mixtures with

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

and 19mm (designated as SMA20) were studied. In designing mixtures, total of 36

specimens were prepared using Marshall Compaction Method with three specimens

4

for each of bitumen content of 5.0%, 5.5%, 6.0%, 6.5%, and 7.0% by Marshall

Hammer at compaction efforts of 50 blows per face.

The work done by NCAT (Brown and Mallick, 1994 and Brown et al., 1997)

indicated that 50 blows of the Marshall Hammer generated a density in SMA

mixtures approximately equal to 100 gyrations of the SGC. With the 100 gyrations

effort, total of 16 specimens were prepared using Superpave Compaction Method,

with two specimens gyrating by SGC at three bitumen contents of 6.0%, 6.5% and

7.0%. As a conclusion, the total of 64 specimens was prepared including the 12

specimens were designed for binder draindown test purpose.

The aggregate degradation afterward was determined by comparing the

changes in gradation of extracted aggregate with the original aggregate gradation.

To achieve the objectives, the scope started with literature search and review on the

information related to the aggregate degradation in Chapter 2 and extensive

laboratory testing according to specified procedure was explained detail in Chapter 3

respectively.

1.5 Importance of the Study

This study was carried out to quantify and compare the amount of aggregate

degradation for SMA mixtures produced by 100 gyrations of the SGC and 50-blow

Marshall Hammer. This study can be a reference to evaluate other studies according

to the two compactive effort performances in the pavement design. Contractors from

developing country such as Malaysia may have problem using SMA mix because of

lack of experience since this mix is considered as new mix for road pavement

compared to standard asphaltic concrete. This type of information would provide

valuable information to agencies who desire to construct SMA pavements.

65

REFERENCES

American Association of State Highway and Transportation Officials. (2001).

Practice for Superpave Volumetric Design for Hot Mix Asphalt (HMA).

Washington D.C. AASHTO PP28-1.

American Association of State Highway and Transportation Officials. (2000).

Determination of Draindown Characteristics in Uncompacted Asphalt Mixtures.

Washington D.C. AASHTO T305.

American Association of State Highway and Transportation Officials (2000).

Preparing and Determining the Density of Hot-Mix Asphalt (HMA) Specimens by

Means of the Superpave Gyratory Compactor. Washington, D. C., AASHTO T-

312.

American Society for Testing and Materials. (1992). Standard Method for Sieve

Analysis for Fine and Coarse Aggregate. Philadelphia, ASTM C 136.

American Society for Testing and Materials. (1992). Standard Test Method for

Materials Finer than 75-μm (No. 200) Sieve in Mineral Aggregates by Washing.

Philadelphia, ASTM C 117.


Specific Gravity and Absorption of Coarse Aggregate. Philadelphia, ASTM C

127.


Specific Gravity and Absorption of Fine Aggregate. Philadelphia, ASTM C 128.

American Society for Testing and Materials. (1992). Standard Test Method for Bulk

Specific Gravity and Density of Compacted Bituminous Mixtures Using Saturated

Surface-Dry Specimens. Philadelphia, ASTM D 2726.


Theoretical Maximum Specific Gravity and Density of Bituminous Paving

Mixtures. Philadelphia, ASTM D 2041.

66


Resistance to Plastic Flow of Bituminous Mixtures Using Marshall Apparatus.

Philadelphia, ASTM D 1559.


Quantitative Extraction of Bitumen from Bituminous Paving Mixtures.

Philadelphia, ASTM D 2172.

Atkins, H. N. (2003). Highway Materials, Soils and Concretes. Fourth Edition.

Upper Saddle River, New Jersey: Prentice Hall.

Balqis binti Abu Bakar (2006). Kajian Kebolehtelapan Campuran Poros di Makmal.

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Brown, E. R. and Haddock, J. E. (1997). A Method to Ensure Stone-on-stone

Contact in Stone Matrix Asphalt Paving Mixtures. NCAT Report No. 97-2.

National Center for Asphalt Technology, Auburn, Alabama.

Brown, E. R. and Mallick, R. B. (1994). Stone Matrix Asphalt Properties Related to

Mixture Design. NCAT Report No. 94-2. National Center for Asphalt Technology,

Auburn, Alabama.

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67

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