i
INFLUENCE OF FLAKY AGGREGATE TOWARDS CREEP AND
RESILIENT MODULUS ON ASPHALT CONCRETE 20
MOHD ZUL HANIF BIN MAHMUD
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
JANUARY 2013
Specially dedicated to my beloved father and mother,
Mahmud bin Doll and Begam binti Nebi
and my family,
Nur Faezah, Bibi Sygena, Bibita, Mohammed Gupta, Mohd Faisal and Nur Aliah
Bazilah
THANK YOU
ACKNOWLEDGEMENT
In the name of Allah, the Most Gracious and Most Merciful.
Alhamdulillah, praises to Allah for giving me the strength, patient, time and
wisdom to complete this thesis. This long awaited moment seems like a dream to me.
There have been many ups and downs while doing this project. Personally, I enjoyed
the moment doing the data collecting and experiments. It seems like a huge challenge
for me to choose the proper rock samples and doing the labs. I would give my sincere
appreciation to my beloved family for believing in me to be who I am today.
My deepest appreciation goes to my supervisors, Dr. Haryati bte Yaacob and
Dr. Ramadhansyah Putra Jaya for their guidance and help. Thank for all the
criticism and shared experiences to help me prepare this thesis. I would also want to
further my thanks to technicians of Highway and Transportation laboratories for their
assistance and cooperation.
Last but not least, I would like to thank my friends that gave their support and
ideas in this project and my time as a post-graduate student in UTM. May ALLAH
reward all of them for their kindness and sincerity. All the helps and sacrifices from
all parties are unforgettable and really appreciated. Hopefully one day, I may
continue to my study to a higher level. InsyaAllah.
ABSTRACT
The aim of this paper is to investigate and evaluate the characteristics of flaky
aggregate shapes that specifically towards creep and resilient modulus. The
maximum allowable aggregate size selected specifically for this study is size 20 mm.
In general, flakiness aggregates are being avoided in asphalt concrete mixture simply
because these types of properties have significant influence of towards gradation and
interlocking characteristic of the aggregate. Due to this significant influence of flaky
aggregate, it is recommended that the proportion of flaky aggregate should be
limited. Therefore, based on the Jabatan Kerja Raya (JKR) and Malaysian Standards
(MS), it specified that the maximum allowable flakiness should be less than 25% in
asphalt concrete mixture. This study is only focusing on asphalt concrete mixture that
consists of 10%, 20% and 30% proportion of flaky aggregate. The objective of this
study is to determine the relationship between resilient modulus against percentage
of flaky aggregates in the asphalt concrete mixture. This study also looks on the
influence different percentage of flaky aggregates towards dynamic creep properties
in a mixture. Hence, several tests like Marshall Tests, Resilient Modulus test and
dynamic creep test were conducted. Based on Marshall Tests, the optimum asphalt
content obtained for 10%, 20% and, 30% was 5.6%, 5.7% and 5.8% respectively.
The findings of this research are the value resilient modulus and stiffness modulus
decreases as the amount of flaky aggregate increases.
ABSTRAK
Tujuan kertas kerja ini adalah untuk mengkaji dan menilai ciri-ciri bentuk
batu baur yang berkeping khusus kepada daya tahan modulus dan rayapan. Saiz
agregat maksimum yang digunakan dalam projek ini dipilih secara khusus adalah
saiz 20 mm. Secara umum, batu baur perlulah dielakkan dalam campuran konkrit
asfalt kerana batu baur mempunyai pengaruh yang signifikan ke arah penggredan dan
sifat saling bertaut batu baur. Disebabkan oleh pengaruh ini, batu baur menjadi tidak
stabil. Oleh itu, nisbah batu baur tidak stabil harus dihadkan. Berdasarkan kepada
Jabatan Kerja Raya (JKR) dan Piawaian Malaysia (MS), penyerpihan maksimum
yang dibenarkan hendaklah kurang daripada 25% dalam campuran konkrit asfalt.
Kajian ini hanya memberi tumpuan kepada campuran konkrit asfalt yang terdiri
daripada 10%, 20% dan 30% perkadaran batu baur berkeping. Objektif kajian ini
adalah untuk menentukan hubungan antara daya tahan modulus terhadap peratusan
batu baur yang berkeping dalam campuran konkrit asfalt. Kajian ini juga mengkaji
pengaruh peratusan batu baur berkeping yang berbeza terhadap sifat dinamik rayap
dalam campuran. Oleh itu, beberapa ujikaji seperti Ujian Marshall, Ujian Daya
Tahan Modulus dan Ujian Rayapan Dinamik telah dijalankan. Berdasarkan Ujian
Marshall, kandungan optimum asfalt yang diperoleh untuk 10%, 20%, dan 30%
adalah masing-masing 5.6%, 5.7% dan 5.8%. Hasil kajian ini mendapati bahawa
nilai daya tahan modulus dan kekakuan modulus berkurangan apabila jumlah batu
baur yang berkeping bertambah.
TABLE OF CONTENTS
CHAPTER TITLE PAGE
TITLE
DECLARATION ii
DEDICATION iii
ACKNOWLEDGEMENT iv
ABSTRACT v
ABSTRAK vi
TABLE OF CONTENTS vii
LIST OF TABLES xi
LIST OF FIGURES xii
LIST OF ABREVATIONS xiii
LIST OF APPENDIX xiv
1 INTRODUCTION 1
1.1 General 1
1.2 Problem Statement 2
1.3 Objectives of the Study 3
1.4 Scope of the Study 3
1.5 Significance of the Study 4
2 LITERATURE REVIEW 5
2.1 Shapes of Aggregates 5
2.2 Influence of Aggregate Morphological Characteristics 6
2.3 Marshall Mix Design 7
2.3.1 Stability 8
2.3.2 Flow 9
2.3.3 Air Void 10
2.3.4 Voids in Mineral Aggregate 11
2.3.5 Void Filled with Asphalt 13
2.4 Resilient Modulus 14
2.4.1 Previous Research on Resilient Modulus 16
2.5 Creep 17
3 METHODOLOGY 18
3.1 Introduction 18
3.2 Methodology Flow Chart 19
3.3 Source and Type of Materials 20
3.3.1 Aggregate 20
3.3.2 Binder 20
3.4 Aggregate Properties Test 21
3.4.1 Sieve Analysis 21
3.4.1.1 Dry Sieve Aggregate 21
(For Fine and Coarse Aggregate)
3.4.1.2 Washed Sieve Analysis 22
3.4.1.3 Gradation limits 24
3.4.2 Specific Gravity 25
3.4.2.1 Specific Gravity for Coarse Aggregate 25
3.4.2.2 Specific Gravity for Fine Aggregate 26
3.4.3 Flakiness Index Test 28
3.4.4 Aggregate Impact Test 30
3.5 Asphalt Physical Properties Test 32
3.5.1 Penetration Test 32
3.5.2 Softening Point Test 33
3.6 Marshall Mix Design 35
3.6.1 Marshall Specimen 35
3.6.2 Theoretical Maximum Density (Loose Mix) 37
3.6.3 Determination of Optimum Asphalt Content 39
3.7 Mechanical Properties of Asphalt Concrete 40
3.7.1 Resilient Modulus Test 41
3.7.2 Dynamic Creep Test 43
4 RESULTS AND DATA ANALYSIS 46
4.1 Introduction 46
4.2 Material Preparation 46
4.2.1 Aggregate Gradation 47
4.2.2 Specific Gravity and Water Absorption 48
4.2.3 Aggregate Impact Value 49
4.3 Determination of Marshall Properties 50
4.3.1 Theoretical Maximum Density 50
4.3.2 Optimum Asphalt Content 50
4.4 Mechanical Properties Analysis 52
4.4.1 Resilient Modulus 53
4.4.2 Dynamic Creep 55
5 CONCLUSION AND RECOMMENDATION 57
5.1 Introduction 57
5.2 Conclusion 57
5.3 Recommendations 58
REFERENCES 59
APPENDIX 63
LIST OF TABLES
TABLE NO. TITLE PAGES
Table 2.0 Test and Analysis Parameters for Asphalt Concrete 7
Table 2.1 Factors Affecting VMA on Hot Mix Asphalt (HMA) 12
Table 3.1 Gradation limits for Asphalt Concrete 20 24
Table 3.2 Maximum Difference Allowable In a Penetration 33
Table 3.3 Design Asphalt Contents 35
Table 3.4 Test and Analysis Parameters for Asphalt Concrete 40
Table 4.1 Flaky Aggregate Gradation 48
Table 4.2 Specific Gravity and Water Absorption for Each 49
Material
Table 4.3 Aggregate Impact Value 49
Table 4.4 Effective Specific Gravity for different 50
Percentage Flaky Aggregate
Table 4.5 Optimum Asphalt Content for Different 51
Portion of Flaky Aggregate
Table 4.6 Verification Sample for Different Percentage 52
of Flaky Aggregate
Table 4.7 Resilient Modulus Values with Different Percentage 53
of Flaky Aggregates
LIST OF FIGURES
NO.OF FIGURE TITLE PAGES
Figure 2.0 Aggregate Shape 6
Figure 2.1 Variation of Stability for Flakiness Indices 8
Figure 2.2 Variation of Flow for Flakiness Indices 9
Figure 2.3 Variation of Air Void for Flakiness Indices 11
Figure 2.4 Variation of Void in Mineral Aggregate for 13
Flakiness Indices
Figure 2.5 Variation of Void Filled with Bitumen for 13
Flakiness Indices
Figure 2.6 The relationship between Resilient Modulus 16
and Flaky Aggregate Content
Figure 3.0 Research Methodology Flow Chart 19
Figure 3.1 Thickness Gauge 29
Figure 3.2 Impact Testing Machine 31
Figure 3.3 Softening Point Test 34
Figure 3.4 Motorized Sieve Shaker 38
Figure 3.5 Resilient Modulus Test 42
Figure 3.6 Dynamic Creep Test 44
Figure 4.1 Aggregate Gradation Curve for AC 20 47
Figure 4.2 Resilient Modulus at 25oC with different 54
percentage of Flaky Aggregate
Figure 4.3 Resilient Modulus at 40oC with different 55
percentage of Flaky Aggregate
Figure 4.4 Stiffness Modulus values with different 56
percentage of Flaky Aggregate
LIST OF ABREVIATIONS
AASHTO - American Association of State Highway and
Transportation Officials
AC20 - Asphalt Concrete Wearing With 20 mm Nominal
Maximum Aggregate Size
ASTM - American Society for Testing and Materials
AASHTO - American Association of State Highway and
Transportation Officials
BS - British Standard
HMA - Hot Mix Asphalt
JKR - Jabatan Kerja Raya
MS - Malaysian Standard
TMD - Theoretical Maximum Density
VTM - Void Ratio in Mix
VFA - Void Filled Asphalt
VFB - Void Filled Bitumen
OAC - Optimum Asphalt Content
OBC - Optimum Bitumen Content
g - gram
mm - millimetre
KPa - KiloPascal
MPa - MegaPascal
N - Newton
ºC - degree celcius
% - percent
LIST OF APPENDIX
APPENDIX NO. TITLE PAGES
Appendix A Aggregate Size Distribution and Determination 64
of Filler
Appendix B Aggregate Proportion Distribution for Flaky 65
Aggregate
Appendix C Specific Gravity and Water Absorption of 66
Coarse and Fine Aggregate
Appendix D Aggregate Impact Value for Asphalt Concrete 20 67
Appendix E Softening Point of Asphalt Cement 67
Appendix F Penetration of Bituminious Materials 67
Appendix G Theoretical Maximum Density 68
Appendix H Marshall Properties Test 70
Appendix I Resilient Modulus 76
Appendix J Marshall Properties Test 91
CHAPTER 1
INTRODUCTION
1.1 General
Aggregates are one of the major materials that are used in any road
constructions. Generally, testing the properties of aggregates is one of the major
concerns in asphalt industry because aggregates testing will give information about
that particular research, design or mixture in order to implement quality control in
any constructions projects. The aggregates samples that are tested will represent and
reflects the average quality of the entire mass of the materials. For this paper, the
major focus is to evaluate on the influence of flaky aggregate in an asphalt concrete
mixture in terms of mechanical properties.
The shapes of the aggregates play a significant influence towards the
performance of asphalt pavements. There are many shapes of aggregates. It can be
classified as round, cubical, flaky, elongated, irregular and etc. For road construction,
the shapes of flaky aggregates are commonly undesirable and therefore the amount
flaky aggregate should be limited. Research have indicates that aggregate testing
towards the characteristic like particle size, shapes and texture will influence the
performance and life span of the asphalt pavement (Brown et al. 1989). According
to the Malaysian Standards (MS 30) manuals, the amount of maximum flakiness
allowed can be varies from 25 % to 30 % depending on the type of road layers. For
asphalt concrete, the maximum amount of flaky aggregate allowed is 25%.
1.2 Problem Statement
Aggregate shapes play a significant role influencing the performance of
asphalt concrete mixture since 95% of the composition of hot mix asphalt is consist
by mineral aggregate. The shapes of the aggregates that are used in many
constructions can be rounded, irregular, angular, flaky, elongated and also a
combination of flaky and elongated. In most road construction, flaky and elongated
aggregates are undesired shaped since these types of aggregate have higher chances
to be broken once the road constructed and opened to public. Oduroh et al. (2000)
described the orientation of the flaky and elongation shape of the aggregate in an
asphaltic mixture creates lower resistance towards shear deformation and thus,
creates problems like premature failure and decreasing the performance of the
pavement.
It is understood that flexible pavement is the most common type of pavement
used in the world. According to Satyakumar & Wilson (2009), most of the authorities
used Marshall Tests to judge the mechanical properties asphalt mixture which is used
in pavement design. They continue to explain that the value of Marshall Tests cannot
be directly used in pavement design calculation due to the increase traffic demand
and load. It is important to understand the mechanical properties to measure
resistance to deformation and failure. One of the tests to measure flexibility of
asphalt mixture is through Resilient Modulus (MR) test. This test is being carried out
using universal testing machine to understand the effectiveness of the elastic
properties of the mixture of asphalt under repeated loading. Erol et. al. (2005)
discussed in his study that by using a more irregular morphologies can improve the
resilient modulus of the bituminous mixture. For this study, the second type of
mechanical testing for asphalt pavement is creep test. This test is to measure time
dependent deformation under constant compressive stress for the asphalt concrete
mixture.
1.3 Objective of Research
The main aim of this research is to investigate the influence of different
proportion of flaky shape aggregates in terms of mechanical properties for an asphalt
concrete mixture for size 20 mm (AC 20). The objectives of this study are also listed
below;
(i) To determine the relationship of different percentage of flaky aggregates
towards the resilient modulus properties in an asphalt concrete mixture;
(ii) To investigate the influence different percentage of flaky aggregates towards
dynamic creep properties in an asphalt concrete mixture.
1.4 Scope of Study
The scopes of study on this research are focusing on the influence flaky shape
aggregates towards creep and resilient modulus for an asphalt concrete mixture. The
scope of study is listed as follow;
i. This study is focused on asphalt concrete size 20 mm (AC 20);
ii. This research involved different proportion of 10%, 20% and 30 % flaky
shapes aggregate in an asphalt concrete mixture;
iii. The scope of this study for this project are involved with the influence of
exceeding the maximum allowable proportion of 25% of flaky shapes
aggregate in an asphalt concrete mixture;
iv. For this study, the laboratory tests that are conducted to obtain the objective
of this research i.e. Marshall Tests, indirect tensile test and dynamic creep
test.
1.5 Significance of Research
This study will help to develop an understanding toward the influence
different shapes aggregates in an asphalt concrete mixture in Malaysia. Below are the
other significant influences towards this research:
(i) To understand the behaviour of different proportion flaky shapes aggregate
based on resilient modulus and stiffness modulus in an asphalt concrete mixture;
(ii) To assist in improving better understanding of proper shapes of aggregates in
order to provide a more sustainable pavement development in Malaysia.
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