Transportation research congress 2016 innovations in transportation research infrastructure

Contents Materials Research on Moisture Susceptibility of Asphalt Mixture Based on Surface Energy Theory ...1 Yu Sun and Lihan Li Analysis on Moisture Susceptibility of Warm Mix Aspha

Beijing, China June 6–8, 2016

Innovations in Transportation Research Infrastructure

Transportation

Research Congress

2016

EDITED BY Linbing Wang, Ph.D.; Jianming Ling, Ph.D.;

SPONSORED BY

China Research Institute of Highway

Tongji University Southeast University Harbin Institute of Technology Chang’An University University of Science and Technology Beijing Construction Institute of the American Society of Civil Engineers

Published by the American Society of Civil Engineers

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Preface

Transportation infrastructure plays a critical role in the economic development of a country and the daily life of everybody Transportation researchers and engineers have always been making efforts towards the ambition of sustainable, smart and resilient transportation The recent years have seen numerous innovations in transportation materials, design, testing and characterization, construction, operation, maintenance and rehabilitation

This ASCE Special Technical Publication contains sixty-eight fully-reviewed papers, covering the topics of pavement materials, pavement structures, geotechnical engineering, and bridge engineering These papers were presented at the inaugural meeting of the Transportation Research Congress (TRC) held at the National Convention Center, Beijing, China, June 6-8, 2016

The TRC is jointly organized by universities, research institutes, industries, and China Highway and Transportation Society TRC is intended to serve as an international platform for researchers, educators, practicing engineers, investors, entrepreneurs, and government officials in transportation infrastructure from all over the world At TRC, experts will present the latest research findings, exchange research ideas, share experiences and lessons learned, showcase successful innovations and practice, identify research and educational needs and provide consultations to transportation community on a regular basis

Section 2 Pavement Structure

Seventeen papers cover the response and long-term performance of asphalt and concrete pavements under traffic and different climatic conditions Different preventive maintenance and rehabilitation strategies are also provided

Section 3 Geotechnical Engineering

Twenty-three papers offer the latest research on the construction and behavior of tunnels, deep foundations, deep excavations, special foundations and geologies

Section 4 Bridge Engineering

Two papers provides the advances in the technologies of energy harvest from bridges and health monitoring system of bridges

All papers published in this ASCE Special Technical Publication were evaluated by at least two reviewers as well as the editors All comments were adequately addressed by the authors of these accepted papers In addition, all published papers are eligible for discussion in the Journal of Materials in Civil Engineering or Journal of Transportation Engineering and can also be considered and recommended for ASCE paper awards

The editors would like to thank all the authors who have submitted their papers to the inaugural meeting of TRC Thanks also go to many reviewers for their time and efforts

The editors are appreciative to Laura Ciampa and Katerina Lachinova from the ASCE Construction Institute (CI), and Donna Dickert from the ASCE Publications for their great support in approving and scheduling the publication of this proceeding

Editors

Linbing Wang, Virginia Polytechnic University

Jianming Ling, Tongji University Pan Liu, Southeast University Hehua Zhu, Tongji University Hongren Gong, University of Tennessee Baoshan Huang, University of Tennessee

Contents

Materials

Research on Moisture Susceptibility of Asphalt Mixture Based on Surface

Energy Theory 1

Yu Sun and Lihan Li

Analysis on Moisture Susceptibility of Warm Mix Asphalt Affected by Moist

Aggregate and Multiple Freeze-Thaw Cycles 12

Jie Ji, Peng Zhai, Zhi Suo, Ying Xu, and Shi-Fa Xu

Properties and Performance Evaluation Index of Lateritic Gravel from Mali

in West Africa 22

Gengzhan Ji, Jinsong Qian, and Guoxi Liang

The Effect of Material Composition on Abrasive Resistance of Pavement

Concrete 31

Ping Li, Ying Li, Lingyi Kong, Feili Pan, and Qiumin Wang

Investigation on Inherent Anisotropy of Asphalt Concrete Due to Internal

Aggregate Particles 39

J Chen, Y Kong, H Wang, Y Chen, and J Liu

Evaluation of Rejuvenator on Softening, Toughness, and Diffusion Ability

for Lab-Aged SBS Modified Asphalt 49

Zhen Wang, Zhen Li, Gen Li, Hao Liu, and Liying Yang

Research of Marshall Test Evaluation Method Based on Anti-Cracking

Material 61

Li Liu, Zhaohui Liu, Sheng Li, and Yu Xiang

Preliminary Study of Using Spent Fluid Catalytic Cracking (FCC) Catalyst

in Asphalt 69

Jianming Wei, Yanan Li, Meng Xu, Xingong Zhang, and Yuzhen Zhang

Law and Corresponding Relationship between TFOT and PAV of Asphalt 82

Guizhao Li, Yelong Feng, Yuzhen Zhang, Cheng Liu, Fuqiang Dong,

and Yuchao Lv

Nanomaterials in Civil Engineering: A State-of-the-Art Review 88

Lei Gao, Ren Zhen, Xiangjuan Yu, and Keyi Ren

The Influence of Foaming Water Content on the Aging Characteristic of

Foamed Warm-Mix Asphalt 98

Fuqiang Dong, Xin Yu, Xingmin Liang, Shengjie Liu, Gongying Ding, and Bo Xu

Cement Asphalt Mastic Dynamic Mechanical Properties and Microstructure

Research 106

Yunliang Li, Menglong He, Jiuye Zhao, Shanshan Wang, Lun Ji, Ouyang Jian,

and Yiqiu Tan

Laboratory Test of Expansive Soil Improved by Lime–Basalt Fiber

Reinforcement 120

Yuehua Wang, Shu Sun, Wei Ye, Fulin Li, and Hanfei Ding

Laboratory Research on Fatty Acid Based Biobinder as an Addition for

Crumb Rubber Modified Asphalt 127

Jiayun Zhang, Gang Xu, Minghui Gong, and Jun Yang

Dynamic Shear Modulus Prediction of Asphalt Mastic Based on

Micromechanics 141

Naisheng Guo, Zhichen Wang, Zhanping You, and Yinghua Zhao

Creep Instability Rules of Asphalt Mixture Based on Compression-Shear

Fatigue Test 156

Junxiu Lv, Xingyu Gu, Xiaoyuan Zhang, and Yiqing Dai

Concrete Strength Monitoring Based on Piezoelectric Smart Aggregates 165

S Yan, J Chen, and W Sun

The Influence of Mixing Temperature on the Performance of Hot In-Plant

Recycled Asphalt Mixture 173

Xuchang Ying and Songlin Ma

Asphalt-Aggregate Interface Failure Mechanism and Its Characterization

Methods 182

Xin Qiu, Shanglin Xiao, Qing Yang, and Xiaohua Luo

Experimental Study on the Effect of Steel Slag Powder and Fine Steel Slag

on the Performance of Asphalt Mixture 195

Bangwei Wu, Liping Liu, Guowei Liu, and Yanjin Feng

Study on the Properties of Waterborne Polyurethane Modified Emulsified

Asphalt 207

Dongwei Cao, Yanjun Zhang, Lei Xia, Yingfu Li, and Haiyan Zhang

Influence of CWCPM on the Mechanical Property of Cement Stabilized

Aggregate 216

Cuizhen Xue, Aiqin Shen, Tianqin He, and Zhenghua Lv

Application of 3D Fractal Dimension in Describing Surface Morphology

of Aggregates 225

Lingjian Meng, Yue Hou, Zhenyu Qian, Linbing Wang, and Meng Guo

Experimental Research on Mix Design and Pavement Performance for

Special Basalt Fiber Reinforced OGFC Asphalt Mixture 233

Xudong Zha, Jieyuan Deng, and Chengjian Zhang

Design and Text Method of Indoor Noise for Micro-Surfacing Mixture 242

Zhen Li, Hao Liu, Yuming Dong, and Zhen Wang

The State-of-the-Art of Multiscale Mechanical Modeling Methods for

Hydrated Cement Concrete 251

Wenjuan Sun, Yue Hou, and Linbing Wang

Effect of Aggregate Mineral Composition on Polish Resistance Performance 263

Zhenyu Qian, Jiangfeng Wu, Fengyan Sun, and Linbing Wang

Pavement Structure

Preventive Maintenance Decision Making of Asphalt Pavement Based on

Fuzzy Comprehensive Evaluation Method 272

Xiaoshan Liu, Haichen Yu, and Haiyao Miao

Public Transport Choice Behavior Model of Short Trip under the

Subtropical Climate 280

Jianmin Xu, Xiaoran Qin, and Yingying Ma

The Long Term Service Performance of Non-Slip and Noise Reduction

Asphalt Pavement Followed Up and Observed in the Southern Climates 291

Xian-Ping Tang, Wen Yi, Xian-Feng He, and Bo Yao

Research on Pavement Materials and Innovations in Intelligent

Transportation Systems 299

Shanglin Song, Linbing Wang, Meng Guo, Yue Hou, Zhoujing Ye,

and Qian Zhao

A Brief Review for SMA Pavements in China 305

Meng Guo, Yiqiu Tan, Xuesong Du, Rui Wen, and Ming Zhang

Environmental Impacts of Different Maintenance and Rehabilitation

Strategies for Asphalt Pavement 312

Bingye Han, Jianming Ling, and Hongduo Zhao

Numeric Analysis of Basalt Fiber Reinforced Concrete Pavement 323

Yiqing Dai, Zhenyi Wang, Junxiu Lv, and Xingyu Gu

Mechanical Response Analysis of Asphalt Concrete Overlay Placed on

Asphalt Pavement Considering Cross-Anisotropic Pavement Materials 333

Yingbin Hu, Kezhen Yan, and Lingyun You

Incorporating Life Cycle Science into Asphalt Pavement Maintenance

Decision Making 341

Haoran Zhu, Haiquan Cai, Jinhai Yan, Hao Li, and Hui Li

Long-Term Performance Study of Long Life Pavement Pilot Section

in Jiangsu, China 353

Aihua Liu, Hao Li, and Peng Zhang

Research on Influencing Factors for Permanent Deformation of Soil

Base of Low Embankment Highway 364

Wei-Zhi Dong and Fu Zhu

Prototype Modeling of Pile-Type Piezoelectric Transducer for Harvesting

Energy from Vehicle Load 374

Yanliang Niu, Hongduo Zhao, Xueqian Fang, and Yujie Tao

Real-Time Monitoring System and Evaluation Method of Asphalt

Pavement Paving Temperature Segregation 383

Lili Zhang, Yan Shi, Zhiqiang Zhao, and Peng Zhang

Study on the Long-Term Performance of Subgrade Structure Considering

Environmental and Climatic Factors 396

Yanbin Ruan, Bin He, and Wanping Wu

Research on RLWT and APA Rutting Loading Mode Based on Digital

Image Technology 400

Cheng Wan, Qiang Yi, Bin Yang, Ke Xu, Yongjun Meng, and Hongliu Rong

Self-Powered Intelligent Monitoring System for Transportation Infrastructures 409

Linbing Wang, Zhoujing Ye, Yue Hou, Hailu Yang, and Xinlong Tong

Highway Geometric Design for Mountainous Regions Considering the

Vehicle-Road Coupling Factors 420

Lei Yue, Yuchuan Du, and Hongyun Yao

Geotechnical

Experiment Study on Tunnel Crown Collapse and the Bolt Anchoring

Effect in Weak and Broken Rock Mass 430

Q W Xu, W T Wang, P P Cheng, H H Zhu, and W Q Ding

Study on the Optimization of Underground Continuous Wall Embedded

Depth of the Super Large Pit 438

Jiabing Yao, Jiangshan Fu, Xin Xu, and Shimin Wang

Studies of the Effect of Seasonal Temperature Change on a Circle Beam

Supporting Excavation 446

Chang Liu, Yan-Po Liu, Gang Zheng, and Ya-Long Zhang

Finite Element Analysis on the Influence of Unloading Effect and Rebound

Effect on Load and Settlement of Single Pile 463

Chang Liu and Deqiang Guo

Research of Prediction Method on Geology Faults of Karst Area in Southwest

of Guangxi Province 472

Haibo Yao, Weidong Lv, Yansheng Geng, and Fan Wang

Centrifuge Modeling of Geosynthetic-Encased Stone Columns in Soft Clay

under Embankment 486

Liangyong Li, Jianfeng Chen, Cao Xu, and Shouzhong Feng

The Preparation and Properties of New Subgrade Replacement Material

in Discontinuous Permafrost Zone 496

Dongfeng Chen, Chunyu Zheng, Jinsong Qian, and Dongxue Li

Influence on High-Speed Railway Bridge Caused by Shield Tunneling in

Sandy Pebble Stratum and Its Controlling Technologies 507

Panpan Cheng, Qianwei Xu, Guyang Li, and Xiaoliang Li

Effect of Subway Tunnel Excavation by Drill-Blasting Method on Pipeline 521

Yongyan Yu, Yongtao Gao, and Zijian Du

Experimental Study on Dynamic Characteristics and Associated

Influencing Factors of Saturated Sand 530

Xiangjuan Yu, Zhen Ren, and Lei Gao

Research on Mechanical Properties of Existing Station Structure While

Diaphragm Wall Is Demolished during Construction 537

Xingzhu Shen, Qiang Qi, Quanxia Yang, and Shimin Wang

Research about Effect of Defects of Filled Layer in Inverted Arch on the

Deep-Buried and Heavy-Haul Railway Tunnel Structures and Its

Reinforcement Measures 545

Shimin Wang, Qingyang Yu, Xingzhu Shen, Xiangfan He, and Jiabing Yao

Three-Dimensional Calculation on Vertical Soil Displacement of Shield

Tunnel Induced by Ground Loss Considering Consolidation 553

Wenjun Zhang, Mingming Jin, Huayang Lei, Heng Kong, and Caixia Guo

Research on Optimization of the Stratum Reinforcement Scheme When

Shield Tunnel Crossing the Fault Fracture Zone 569

Xiangfan He, Hongzhao Feng, Feng Gao, and Shimin Wang

Stratigraphic Classification Based on the Evaluated Difficulty of the

Construction by Using Shield Tunneling Machine 577

Mengbo Liu, Shaoming Liao, Longge Xiao, and Chihao Cheng

Comparative Study on Suitability of EPB Machine in Typical Sandy Cobble

Ground in China 590

Chihao Cheng, Shaoming Liao, Lisheng Chen, and Zhe Zhou

Numerical Analysis of Highway Tunnel Fire under Semi-Transverse and

Transverse Ventilation Systems 604

Bin Xue, Jianzhong Pei, Jiupeng Zhang, Yanwei Li, Rui Li, and Linghao Zhou

Mechanical Behavior of SSPC Segment Used in Launching and Arrival of

Shield Machine in Soft Ground 614

Wenjun Zhang, Gaole Zhang, Huayang Lei, Mingming Jin,

and Atsushi Koizumi

Research on Settlement in Full-Face Excavation Model Test of Shallow

Buried Tunnel Based on ADECO-RS 627

Shi Tan, Wenqi Ding, Cheng Liu, and Chao Duan

Brief Introduction of Synchronous Grouting Model Test Based on

Quasi-Rectangular Shield Tunnel 640

Chao Duan, Wenqi Ding, Tianchi Zhao, Tao Tang, and Peinan Li

Study of the Formation and Supporting Principle of Filter Cake in Slurry

Shield Tunneling by Particle Flow Code 648

R Jia, F L Min, W Zhu, and W J Zhang

Chamber Pressure Optimization for Shield Tunneling 662

Zhouxiang Ding, Peng Wang, and Siyuan Wang

Bridge Engineering

Theoretical Modeling on Piezoelectric Energy Harvesting from Bridges

Considering Roadway Surface Irregularities 673

Z W Zhang, H J Xiang, and Z F Shi

The Health Monitoring System Design for Bridge Based on Internet

of Things 685

Xinlong Tong, Zhoujing Ye, Yinan Liu, Hailu Yang, Yue Hou,

and Linbing Wang

Research on Moisture Susceptibility of Asphalt Mixture Based on Surface Energy Theory

Yu Sun1 and Lihan Li2

1Key Laboratory of Road and Traffic Engineering of Ministry of Education, School of

Transportation Engineering, Tongji Univ., Shanghai, China, P.O Box 201804 (corresponding

author) E-mail: 1210698@tongji.edu.com

2Key Laboratory of Road and Traffic Engineering of Ministry of Education, School of

Transportation Engineering, Tongji Univ., Shanghai, China, P.O Box 201804 E-mail:

lhli@tongji.edu.com

ABSTRACT

According to surface energy theory and adhesion-peeling model, Wilhelmy plate method and sessile drop method are respectively used to test the surface free energy parameters of asphalt

and aggregates so that adhesion work and peeling work can be calculated ER is an evaluation

product based on adhesion work and peeling work, which can reflect the moisture susceptibility

of asphalt mixture because of its good correlation with macroscopic index The higher ER is, the

better the mixture performs Results show that short-term aging, contrary to long-term aging,

improves the moisture susceptibility of asphalt mixture; soaking will decrease the anti-stripping

ability; freezing has no effect on moisture susceptibility, but additional high temperature thawing

process will reduce the resistance to water damage Anti-stripping ability of asphalt mixture is

improved with the increasing of surface roughness; an increase in surface water and clay content

is detrimental to moisture susceptibility

1 INTRODUCTION

Because of its short construction period, improved driving comfort and safety, asphalt pavement has become more and more popular However, moisture induced damage (Huang,

2006; Wang, 2010) of asphalt pavement can seriously lower its service performance Water

comes into the interface of asphalt and aggregates, which makes asphalt fall off from aggregates,

and then asphalt mixture becomes loose, resulting in pit and groove under the traffic loads

Besides the external factors including load and water, moisture induced damage also depends on

the moisture susceptibility of asphalt mixture

At present, many methods and indexes (Hansen, 1991; Brown, et al 1972; Lynn, et al 1993;

Ronald, et al 1994; James, 1991) have been put forward, such as water-boiling method, soaking

method, and freeze thaw split test However, these methods and indexes all evaluate the

performance from the macroscopic aspect, ignoring the process and mechanism of moisture

damage Some researchers found that surface energy theory (Cheng, 2002) and its test methods

can well explain the moisture susceptibility of asphalt mixture According to the surface energy

theory, the adhesion between asphalt and aggregates mainly depends on their wetting function

When the asphalt diffuses and wets the surface of aggregates, some energy will be released,

which depends on the intimate contact and mutual attraction of asphalt and aggregates It is

easier for water to intrude into the asphalt-aggregate interface because the adhesion between

water and aggregates is lager, which will lead to the water damage of asphalt pavement

Therefore, surface energy theory and its test methods are used in this paper to evaluate the adhesion and peeling characteristics of asphalt mixture Furthermore, moisture susceptibility and

its influence factors can be explored according to the parameters of surface energy

Although the cohesiveness is not as large as the interlocking and the adhesion, it still plays an

important role in the moisture susceptibility Research shows that the larger the viscosity is, the

higher the cohesiveness is, accompanied with improved moisture susceptibility (Lai, 2004; Yan,

Where G is cohesiveness work, mJ/m2;  is surface energy of asphalt, mJ/m2

2.1.2 Adhesion between asphalt and aggregates

According to surface energy theory, adhesion between asphalt and aggregates mainly comes from energy interaction, which is formed by asphalt wetting aggregates When the asphalt

diffuses and wets the surface of aggregates, some energy will be released, which depends on the

intimate contact and mutual attraction of asphalt and aggregates According to thermodynamics,

the energy can indicate the stability of the whole system The more energy is released, the stabler

the system is, which means the adhesion and thus the water stabilty are better When asphalt

mixture is immersed into water, it is easier for water to intrude into the asphalt-aggregate

interface because the adhesion between water and aggregates is lager, forming asphalt-water

interface and water-aggregate interface, which results in the peeling of asphalt

Dr Lytton et al from Texas A&M University show that surface energy can characterize the adhesion of asphalt mixture, and it is also feasible to predict the anti-stripping ability of asphalt

(Lytton, 2002)

2.2 Parameters of surface energy

According to surface physical chemistry (Teng, 2009), the surface energy  of liquid or solid can be calculated with Van der Waals parameter LW and acid-base interaction parameter AB,

while AB consists of acid parameter 

and base parameter 

, and their relationship is shown

are electron acceptor and electron donor, respectively

2.3 Adhesion and peeling model

2.3.1 Adhesion model of asphalt and aggregates

Adhesion work refers to the decrease of interfacial free energy caused by adhesion of asphalt

to aggregates Fowkes thinks that the adhesion work of an interface is the sum of all adhesion

work cause by interaction among molecules Combined with Van der Waals theory and Lewis

acid-base theory mentioned in surface physical chemistry, adhesion work can be expressed by

Eq (3) when minor force is ignored (Xiao, 2007)

adhesion work caused by Lewis acid-base force

By substituting the surface energy parameters into Eq (3) combining with the adhesion process, the adhesion work can be calculated by Eq (4) The larger it is, the better adhesion

performance is

2.3.2 Peeling model of asphalt and aggregates

Water intrudes into the interface of asphalt and aggregates instead of asphalt film with the repeated action of wheel load Peeling means that asphalt is separated from aggregates and two

new interfaces are formed, that is asphalt-water and water-aggregate The energy released in this

process is defined as peeling work It includes the part of Van der Waals force and the part of

Lewis acid-base force, which can be expressed by Eq (5)

LW AB asw asw asw

Where W asw is peeling work; asw means the process of peeling

By substituting the surface energy parameters into Eq (5) combining with the peeling process, the peeling work can be calculated by Eq (6) The larger it is, the worse ability of anti-

Index of moisture susceptibility based on adhesion-peeling model

According to adhesion-peeling model, adhesion work and peeling work will both increase with the increasing of surface energy parameters and the moisture susceptibility depends on both

of them Bhasin (Bhasin, 2006) from Texas A&M University has put forward the indexes to

evaluate the moisture susceptibility of asphalt mixture based on adhesion and peeling work

through comprehensive experiments, which are shown in Eq (7)~(8)

Where W is adhesion work; as W asw is peeling work; G is cohesiveness work

ER2 (ER for short) is used in this paper because of its consideration for cohesiveness work

3 TEST MATERIALS AND SCHEME

15°C Ductility (cm)

135°C Viscosity (Pa.s)

Table 2 Properties of Aggregates

Aggregates Apparent density (g/cm3) Water absorption (%)

substitution of the parameters into Eq.(4) and Eq.(6), the adhesion and peeling work can be

calculated, and then ER can be obtained to evaluate the moisture susceptibility of asphalt

mixture The influence factors are also analyzed and the simulation conditions are explained as

Thawing: the frozen samples are soaked in the water for 0.5h at 60°C, and soaked in the water at 25°C, and then dried

Surface roughness: the basalt is polished with waterproof abrasive papers of 180#, 240#, 320#, and then cleaned and dried

Surface clay content: the aggregate is buried for some days in the dust particles whose diameter is less than 0.075mm, and then brushed until its clay content meets the requirement

Surface water content: the clean aggregate is soaked in the distilled water for 1d, dried at 25°C, weighed every minute, and tested immediately after its water content meets the

mixture is AC-13 and the results are shown in Figure 1

Figure 1 Relationship of ER and TSR

There is good correlation between ER and macroscopic index (Figure 1) ER is incrased with higher TSR Thus it is feasible to use ER to evaluate the moisture susceptibility of asphalt

asphalt When the aggregate is determined, the larger  is, the better moisture susceptibility is

Table 3 Parameters of Different Asphalt and Basalt Mixture

Types of asphalt γ

(mJ/m2)

Adhesion work (mJ/m2)

Peeling work (mJ/m2)

Table 4 Parameters after Short-term Aging

Types of asphalt Adhesion work

(mJ/m2)

Peeling work (mJ/m2)

Cohesiveness work (mJ/m2)

ER after short-term aging

Table 5 Parameters after Long-term Aging

Types of asphalt Adhesion work

(mJ/m2)

Peeling work (mJ/m2)

Cohesiveness work (mJ/m2)

ER after long-term aging

ER after short-term aging is generally larger than that of the original samples, which means the moisture susceptibility after short-term aging is better However, the changing trend of ER

after long-term aging is not the same The moisture susceptibility of 70#+PR.S is better than the

original one, while the others are worse In summary, short-term aging improves moisture

susceptibility and long-term aging is the opposite

4.2.3 Soaking

Parameters of 70# and basalt after different soaking time are shown in Table 6 During water immersion, the cohesiveness work of asphalt and the adhesion work of asphalt-aggregate are

kept constant at 29.46 mJ/m2 and -44.83 mJ/m2, respectively

Table 6 Parameters of 70# and Basalt after Soaking

The peeling work is increased after soaking, while ER is reduced with longer soaking time

This means the anti-stripping ability will get worse after longer water immersion, and moisture

damage is more prone to happen So it is important to reduce the contact time of asphalt mixture

with water

4.2.4 Freezing and thawing

The peeling work and ER of 70# and basalt under freezing and thawing condition are shown

in Table 7 During freezing and thawing, the cohesiveness work of asphalt and the adhesion

work of asphalt-aggregate are kept constant at 29.46 mJ/m2 and -44.83 mJ/m2, respectively

Table 7 Parameters under Different Conditions

Simulated condition Peeling work (mJ/m2) ER after simulation

There is insignificant variation in ER after freezing, which means freezing has little influence

on the moisture susceptibility However, ER after freezing and thawing decreases substantially,

and is even worse than the soaking effect

4.3 Influence factors based on surface energy of aggregates

4.3.1 Types of aggregates

The parameters of different aggregates and SBS are shown in Table 8 The cohesiveness work of SBS is still 31.34 mJ/m2

Table 8 Parameters of Different Aggregates and SBS

Types of aggregates γ (mJ/m2) Adhesion work (mJ/m2) Peeling work (mJ/m2) ER

surface energy and the base parameter of limestone and sandstone are larger, resulting in the

better adhesion and anti-stripping ability

4.3.2 Surface roughness

The adhesion work, peeling work and ER of SBS and basalt with different surface roughness are shown in Table 9 The cohesiveness work of SBS is 31.34 mJ/m2

Table 9 Parameters of SBS and Basalt with Different Surface Roughness

Types of water-sand Adhesion work (mJ/m2) Peeling work (mJ/m2) ER

With the increase in water-sand number, the surface roughness and ER become smaller

That’s because the adhesion work and the peeling work both increases, but the adhesion work

increases more sharply

When the number of water-sand is larger than 240#, ER will stay invariant Therefore, to some extent, larger surface roughness and surface area can improve the moisture susceptibility of

asphalt mixture

4.3.3 Surface clay content

The adhesion work, peeling work and ER of SBS and basalt with different surface clay content are shown in Table 10 The cohesiveness work of SBS is 31.34 mJ/m2

With the increase in surface clay content, ER is reduced, which means the mud around the aggregates can decrease moisture susceptibility because the adhesion work is decreased while the

peeling work is increased So it is very important to reduce the surface clay content of aggregates

in engineering practice

Table 10 Parameters of SBS and Basalt with Different Surface Clay Content

Clay content (%) Adhesion work (mJ/m2) Peeling work (mJ/m2) ER

4.3.4 Surface water content

The adhesion work, peeling work and ER of SBS and basalt with different surface water content are shown in Table 11 The cohesiveness work of SBS is 31.34 mJ/m2

Table 11 Parameters of SBS and Basalt with Different Surface Water Content

Water content (%) Adhesion work (mJ/m2) Peeling work (mJ/m2) ER

molecules and aggregates, the adhesion work and the peeling work both decrease However, the

adhesion work decreases more sharply, leading to the reduction of anti-stripping ability Thus,

aggregates must be dried in construction practice

4.4 Comparison of influence factors

The summary of ER under different conditions is shown in Table 12 and Table 13

Table 12 ER of 70# under Different Conditions

Table 13 ER of Basalt under Different Conditions

but additional high temperature thawing process will reduce its resistance to water damage In

summary, freezing and thawing is the most influential factor of moisture susceptibility

Additionally, moisture susceptibility of mixture is the best when the water-sand number is 120# while it is the worst when surface clay content is 1.0% In summary, surface clay content is

the most detrimental to moisture susceptibility, followed by surface roughness, while surface

water content has little effect

macroscopic index The larger ER is, the better the moisture susceptibility is

Short-term aging can increase the cohesiveness work and the adhesion work, resulting in the improvement of moisture susceptibility On the contrary, long-term aging will decrease the performance of asphalt mixture

Soaking will increase the peeling work between asphalt and aggregates, which is adverse

to the anti-stripping ability of asphalt mixture

Freezing has no effect on the performance of asphalt mixture, but additional high temperature thawing process will increase the peeling work and reduce the resistance to water damage

With the increasing of surface roughness, adhesion work and peeling work are both increased However, adhesion work increases more sharply, making the moisture susceptibility better

With the increasing of surface clay content, moisture susceptibility of asphalt mixture gets worse because the adhesion work decreases and the peeling work increases As a result, surface clay content is the most adverse factor

With the increasing of surface water content, moisture susceptibility decreases because the adhesion work and the peeling work both decrease and the adhesion work decreases more sharply

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for Asphalt Pavement.” National Cooperative Highway Research Program, Washington,

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on Surface and Interface Theory.” Journal of Wuhan University of Technology, Vol 29, No

Analysis on Moisture Susceptibility of Warm Mix Asphalt Affected by Moist Aggregate

and Multiple Freeze-Thaw Cycles

Jie Ji1; Peng Zhai2; Zhi Suo3; Ying Xu4; and Shi-Fa Xu5

1School of Civil Engineering and Transportation, Beijing Univ of Civil Engineering and

Architecture; Beijing Urban Transportation Infrastructure Engineering Technology Research

Center, Beijing 100044

2School of Civil Engineering and Transportation, Beijing Univ of Civil Engineering and

Architecture; Beijing Urban Transportation Infrastructure Engineering Technology Research

Center, Beijing 100044

3Beijing Urban Transportation Infrastructure Engineering Technology Research Center; Beijing

Collaborative Innovation Center for Metropolitan Transportation, Beijing 100044

4Beijing Urban Transportation Infrastructure Engineering Technology Research Center; Beijing

Collaborative Innovation Center for Metropolitan Transportation, Beijing 100044

5Beijing Urban Transportation Infrastructure Engineering Technology Research Center; Beijing

Collaborative Innovation Center for Metropolitan Transportation, Beijing 100044

ABSTRACT

To analyze the effect of moist aggregate and multiple freeze-thaw cycles on moisture susceptibility of warm mix asphalt (WMA) containing organic wax additive (Sasobit), different

target moisture contents (1%, 2%, 3%) of aggregates (limestone and basalt) are simulated using

the bucket-mixer heating method in lab The moisture susceptibility of WMA that composed of

3% Sasobit modified asphalt binder (by weight of SK-90 asphalt binder) and different types of

dry/moist aggregates in one/two freeze-thaw cycles are test using the modified Lottman test The

test results show the moisture susceptibility of WMA linearly decreases significantly with the

increase of moisture content and freeze-thaw cycle number The moisture susceptibility of WMA

made with moist aggregate cannot meet the current specification in China However, under

identical conditions (same moisture content and freeze-thaw cycle number), the moisture

susceptibility of WMA made with basalt is better than that of WMA made with limestone

KEYWORDS: moisture susceptibility; warm mix asphalt (WMA); moist aggregate; organic

wax additive; modified Lottman test; multiple freeze-thaw cycle

1 INTRODUCTION

In recent years, construction of resource-conserving and environmental-friendly society is had been devoting greater efforts in our country As a new road technology, warm mix asphalt

(WMA) is being widely promoted because of the good performance as hot asphalt mixture

(HMA) On the other hand, WMA overcome high energy consumption, high emission and other

technical defects(Gandhi 2008; Ayman et.al 2013; Kristjansdottir et.al 2007) But in the process

of production of WMA, moist aggregate is not completely dried because of lower drying and

production temperature which increases the potential for moisture damage(Mohd Hasan et.al

2015; Bhasin et.al 2006) Moisture of aggregate will lead to the decline of adhesiveness between

asphalt binder and aggregate and separate asphalt binder from aggregate surface that lead to

stripping in the asphalt mixture, therefore declining the moisture susceptibility of WMA During

the service life, penetration of moisture through the asphalt mixture may increase the

vulnerability of the pavement to stripping failure (Hunt 2007; Prowell et.al 2007) Moisture

damage can result in a decrease of strength and durability in the asphalt mixture and ultimately

affects its long-term performance

Currently, even though some countries have specifications that require a completely dry aggregate in WMA, not many research projects are conducted to determine the effects of the

moist aggregates with WMA (Wasiuddin et.al 2007; Curtis et.al 1992; Prowell 2007), which may

result in moisture damage and further lead to the failure of pavement Xie et.al (2011) found that

the moist aggregate affects the moisture susceptibility of WMA, and studied the relationship

between mixing temperature, drying time of aggregate with the moisture susceptibility of WMA,

suggested that prolong the drying time to ensure the aggregate thoroughly dried to avoid

moisture damage Xiao et.al (2009; 2010) evaluated the moisture susceptibility of WMA

containing organic wax additive which has different moisture content and different content of

hydrated lime using freeze-thaw splitting strength test, found that the TSR of WMA made with

moist aggregate was much lower than that of WMA containing dried aggregate, but by adding a

certain content of hydrated lime could improve the moisture susceptibility of WMA Hasan et.al

(2015) studied on the effect of adding hydrated lime to the moisture susceptibility of WMA

containing saturated surface dried (SSD) aggregate and the influence of multiple freeze-thaw

cycles to moisture susceptibility of WMA, found that the TSR of WMA made with moist

aggregate cannot meet the current specification, but it could be improved after adding hydrated

lime, and the TSR of WMA appeared a downward trend undergoing multiple freeze-thaw cycles

As mentioned above, research scholars began to recognize the moisture damage of WMA could be attributed to moisture in aggregate due to the drying temperature of aggregate was

lower But the moist aggregate was referred to SSD aggregate in these papers and how to

simulate the different moisture content of aggregate and analyze the effect of different moisture

content of aggregate on the moisture susceptibility of WMA is little few

2 OBJECTIVES

The objective of this paper is to evaluate the moisture susceptibility of WMA affected by moist aggregate and multiple freeze-thaw cycles The specific objectives of this study were to:

Determine properties of modified asphalt binder containing 3% Sasobit additive

Simulate 1%, 2% and 3% target moisture content of two aggregate sources (limestone and basalt) using the bucket-mixer heating method in Lab

Prepare WMA made with Sasobit modified asphalt binder and dry/moist aggregates

Evaluate the moisture susceptibility of WMA in one/two freeze-thaw cycles using the modified Lottman test

3 MATERIALS AND EXPERIMENTAL PROGRAM

hydrocarbons, produced by means of Fischer-tropsch (F-T) synthesis It is long chain composed

from 40 to 115 carbon atoms Physical properties of Sasobit are tested and shown in Table 1

Table 1 Physical Properties of Sasobit

Items Density/（g/cm3） Melting point/°C 25°C Penetration/0.1

binder using simply stirring 10–15 min, because the melting point of Sasobit is above 100°C and

it's completely dissolves in SK-90 asphalt binder at temperature above 115°C According to

Standard Test Methods of Bitumen and Bituminous Mixtures for Highway Engineering

(JTGE20-2011) in China ((JTGE20-2011), physical properties of SK-90 asphalt binder and Sasobit modified asphalt

binder were tested, as presented in Table 2

Table 2 Physical properties of SK-90 asphalt binder and Sasobit modified asphalt binder

Asphalt binders SK-90 asphalt

Residue after RTFOT

3.4 Aggregates

Two local types of aggregates, limestone and basalt, produced by Beijing municipal Luqiao

Building Materials Group Co., LTD, were used in this paper According to the Test Methods of

Aggregate for Highway Engineering (E42-2005 JTG) in China (2005), the sievingof aggregates

are shown in Table 3

3.5 Mix design methodology

The nominal maximum size of mix was 16.0 mm, and seen in Table 4 The mix design was used Marshall method procedure The combined aggregate included a coarse, fine and the

limestone powder as mineral filler according to specification set by Technical specification for

construction of highway asphalt pavement (JTGF40-2004) in China (2004) All the produced

samples mixed by combination of the aggregate proportion and Sasobit modified asphalt binder

Table 3 Sieving of aggregate

0 100 97.8 25.8 6.7 4.8 4.0 3.7 3.4 2.9 10-15

The optimum asphalt content of mix was 4.3% and the performances of mix are shown in

Table 5 All performances of samples should meet the specification set by Technical

specification for construction of highway asphalt pavement (JTGF40-2004) in China (2004)

Table 5 Performances of asphalt mixture

Items Dynamic stability/

(passes/mm)

Maximum bending strain/



Residual stability/% TSR/%

Asphalt

3.6 Simulate moist aggregates

Based on the literature reviews (Xiao et.al 2009; Xiao, Amirkhanian et.al 2010; Hasan et.al 2015), oven-heating method is the simplest approach that is widely used to simulate the moist

aggregate In this paper, the bucket-mixer heating method was used to simulate the moist

aggregate

3.7 Modified Lottman Test

The Lottman test is produced by the combination of the Lottman test and the Tunniclif&Root test Three subsets (9 samples) of 101.6 mm in diameter and 63.6 mm high sample are

compacted to 7 ± 1% air voids when using the Marshall apparatus One subset (3 samples) is to

be tested dry (considered as a control subset) , the other two subsets (6 samples) is to be tested

after partial saturation and moisture conditioning (considered as a treated subset) The control set

(3 samples) is just submerged in a 25o C water bath for 2 hours and they are ready to be tested

The treated set (6 samples) is saturated until their air void volume is (70~80)% filled with water

Then, the 6 samples are put in freezer for at 
least 16 hours at -18°C and placed in a 60 oC water

bath for 24 hours Furthermore, the three samples are put in freezer for at 
least 16 hours at

-18°C and placed in a 60 oC water bath for 24 hours again Afterwards, the samples are placed in

the 25o C water bath for 2 hours and then they are ready to be tested Finally, the indirect tensile

strength is conducted on the control and treated subset at 25o C In partially, in the untreated

subset, three samples are undergo one freeze-thaw cycle and the other three samples are treated

two freeze-thaw cycles (AASHTO 2003; Chapuis et.al1995;2000; Solaimanian et.al 2000)

So the dry indirect splitting strength (dry ITS1) and wet indirect splitting strength which are denoted as wet ITS1 and wet ITS2 respectively are measured The tensile strength ratio TSR1 and

TSR2 are calculated as followed Eqs (1) ~ (2) Therefore, modified Lottman test is a more

scientific method that can correctly reflect the effects on moisture susceptibility of asphalt

mixture

1 1

1100%

wetITS TSR

dryITS

2 2

ITS1 is wet indirect splitting strength undergoing one freeze-thaw cycle wet ITS2 is wet indirect

splitting strength undergoing two freeze-thaw cycles

4 TEST RESULTS AND DISCUSSION

4.1 Simulate moist aggregate

In Lab, the bucker-mixer heating method was adopted to simulate the target moisture content (1%, 2% and 3%) aggregates and the moisture content aggregates were test and calculated The

relationship between the moisture content aggregate with the target moisture content aggregate is

shown in Table 6

Table 6 Residual Moisture Contents of Aggregates

As presented in Table 6, under the identical target moisture content, the residual moisture content of limestone is large than that of basalt The target moisture content of aggregate is

higher, the residual moisture content of aggregate is larger

Table 7 Moisture susceptibility of WMA after one freeze-thaw cycle

Dry ITS1 (Mpa) 0.94 0.78 0.66 0.48 0.84 0.75 0.67 0.60 Wet ITS1(Mpa) 0.76 0.54 0.40 0.26 0.69 0.56 0.44 0.35 TSR1(%) 80.85 69.23 60.60 54.17 82.14 74.67 65.67 58.33

As presented in Table 7, WMA made with dried limestone/basalt passes the TSR1 test with a

ratio of 0.75 technical requirements set by Technical specification for construction of highway

asphalt pavement (JTGF40-2004) in China (2004) Whereas the moisture susceptibility of WMA

made with moist limestone/basalt is diminished, lower than 0.75, and cannot meet the

specification The WMA made with 3% moist limestone/basalt has the lowest dry ITS1, wet ITS1

and TSR1 value that reduced approximately 40%, 60% and 30% respectively in comparison with

dried aggregate This shows that the moisture in aggregate is more likely to strip and diminish

adhesion bond between asphalt binder and aggregate due to moisture damage A similar trend in

the results was also observed from studies conducted by Hasan et.al (2015) and Xiao et.al

(2009)

4.3 Moisture susceptibility of WMA in moist aggregate

To study the influence of moist aggregate on the moisture susceptibility of WMA, the indirect tensile strength of wet conditioned samples was test using the modified Lottman test,

and compared to that of the dry samples The dry ITS1, wet ITS1 and TSR1 value of WMA made

with limestone/basalt is graphically shown in Fig 1

Fig 1 shows the dry ITS1, wet ITS1 and TSR1 value of WMA made with moist limestone/basalt are linearly declined with the moisture content increases, and lower than that of

WMA made with dried limestone/basalt, which is thought to be due to the ability of the lower

production temperatures not to expel a greater amount of moist from the asphalt binder before

coating the aggregates, therefore declining adhesion between asphalt binder and aggregate and

accelerating moisture damage The relationships between dry ITS1, wet ITS1 and TSR1 value of

WMA and moisture content of aggregate is linear, and the correlation coefficients are above

0.95 Meanwhile, the dry ITS1, wet ITS1 and TSR1 of WMA made with basalt decreases further

slowly than that of WMA made with limestone, which indicates that the properties of aggregate

is critical to the moisture susceptibility of WMA Due to the surface texture of basalt is more

abundant and the moisture content of basalt is little, which is beneficial to strength adhesion

bond between aggregate and asphalt binder So the adhesion between limestone and asphalt

binder is weaker than that of basalt and asphalt binder

Figure 1 Moist aggregate impacted on TSR1 and ITS1 of WMA 4.4 Comparison of moisture susceptibility of WMA after one/two freeze-thaw cycles

To understand the effect of multiple freeze-thaw cycles on WMA, samples were undergo two separate freeze-thaw cycles as per AASHTO T-283 The indirect tensile strength of wet

conditioned samples undergoing two freeze-thaw cycles was test using the modified Lottman test

and compared to that of the dry samples, and the samples of the one freeze-thaw cycle The

moisture susceptibility of WMA made with dried/moist limestone/ basalt undergoing two

freeze-thaw cycles is seen in Table 8

Table 8 Moisture susceptibility of WMA after two freeze-thaw cycles

Dry ITS1 (Mpa) 0.94 0.78 0.66 0.48 0.84 0.75 0.67 0.60 Wet ITS1(Mpa) 0.64 0.47 0.35 0.21 0.61 0.52 0.43 0.31 TSR1(%) 68.09 60.26 53.03 43.75 72.62 69.33 64.18 51.67

As presented in Fig 2, the moisture susceptibility of WMA made with limestone/basalt did not perform well after two freeze-thaw cycles compares to one freeze-thaw cycle The poor

performance could be related to excess freeze-thaw cycle that causes poor aggregate and asphalt

binder adhesion Meanwhile, the wet ITS2 and TSR2 value of WMA made with moist

limestone/basalt are further declined with freeze–thaw cycle number increases, and reduced

approximately 70% and 80% respectively in comparison with one freeze-thaw cycle This shows

that the number of freeze-thaw cycle will significantly reduce the adhesion bond between the

aggregate and asphalt binder and strip the asphalt binder from the aggregate

Due to the freeze-thaw cycle number increases, the form and volume of moisture of aggregate can be changed repeatedly Normally, the liquid moisture has a stronger wetting ability

to the aggregate, it will gradually peel the asphalt adhered to the surface of aggregate Once

liquid moisture changes to solid one, the volume of moisture will be expanded by approximately

4%, therefore the extra force will be occurred inside the aggregate, this force will induce the

aggregate to be broken and reduce the adhesion strength of aggregate and asphalt binder So

increasing freeze-thaw cycle number will aggravate the diverse effects This similar trend can be

observed from all of samples

Figure 2 Comparison of moisture susceptibility of WMA after one/two freeze-thaw cycles

decreased with the increase of moisture content of aggregate This shows that the moisture in

aggregate is more likely to strip and fail due to moisture damage

The moisture susceptibility of WMA samples do not perform well after two freeze-thaw cycles compares to one freeze-thaw cycle Therefore increasing freeze-thaw cycle number will

significantly change the form and volume of moisture in aggregate repeatedly and debond the

adhesion between aggregate and asphalt binder

Comparing with WMA made with limestone, the dry ITS, wet ITS and TSR value of WMA made with basalt is higher It is mainly because the porous characteristics of basalt will

accelerate moisture evaporation and strength the adhesion bond between asphalt binder and

aggregate Therefore, the moisture susceptibility of WMA made with basalt is better than that of

WMA made with limestone

ACKNOWLEDGMENT

The paper is supported by the Importation and Development of High-Caliber Talents Project

of Beijing Municipal Institutions (Grant No PXM2013-014210-000165) and National Natural

Science Foundation of China (51478028) The authors wish to express their gratitude to Mr

Jin-qi GAO for his assistance in some of the preliminary laboratory work

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Properties and Performance Evaluation Index of Lateritic Gravel from Mali in West

Africa

Gengzhan Ji1; Jinsong Qian2; and Guoxi Liang3

1Postgraduate, Key Laboratory of Road and Traffic Engineering of the Ministry of Education,

Tongji Univ., 4800 Cao'an Rd., Shanghai, China, 201804 (corresponding author) E-mail:

964836770@qq.com

2Associate Professor, Key Laboratory of Road and Traffic Engineering of the Ministry of

Education, Tongji Univ., 4800 Cao'an Rd., Shanghai, China, 201804 E-mail:

qianjs@tongji.edu.cn

3Guangdong Provincial Changda Highway Engineering Co., Ltd., Guangzhou, Guangdong

Province, China E-mail: lguoxi89@126.com

ABSTRACT

The gradation of 100 groups of lateritic gravel along the Barcelona Highway in The Republic

of Mali is studied by the means of grain size analysis and the typical grading was determined

The compaction property is studied by heavy compaction test and vibration platform method and

the mechanical property is evaluated through California bearing ratio (CBR) test The results

showed that: 1) the gradation of natural lateritic gravel is generally poor It holds a high

percentage of coarse grain soils and lacks sandy soils The proportion of fine grained soil is also

high 2) The fine grained soil belongs to low liquid-limit clay, which cannot meet the domestic

requirements of natural gravel material used as base and subbase filling 3) The heavy

compaction method can achieve more desirable compactness 4) The CBR values are closed to

80% in the degree of compaction of 96% or more, which can be used as bottom subbase of all

highways in the West Africa Lastly, the performance evaluation indices of lateritic gravel

subbase are given through domestic and foreign regulatory requirements and existing experience

in engineering practice

KEYWORDS: Lateritic gravel; base material; CBR; Liquid and Plastic Limits; gradation;

performance evaluation index

1 INTRODUCTION

Lateritic gravel is a widespread material in tropical and subtropical African countries, and their geotechnical properties are influenced by climate, hydrological and geological conditions,

which has been widely used as the packing of road base and subbase(Wang, 1985; Guo, 1990;

.Qu, 2013) However, the properties of lateritic gravel in Mali are lack of research and the

traditional specification developed in the United Kingdom and North America has been used in

many tropical countries (Umarany and David, 1996) The specification is not entirely applicable

to the West African The performance of lateritic gravel road pavement is not only related to the

propertied of the lateritic gravel, but also depends on the climate and drainage conditions In

West Africa, some roads have serious disease such as Bamako-Segou highway engineering in

Bamako in Republic of Mali, as shown in Figure 1 The reason is that the subgrade is low

embankment and some flooded easily in the rainy day Besides, with the effect of traffic load, the

diseases on base and subbase were easily casued The performance of road structure is almost

lost

In order to use lateritic gravel reasonably and prevent the disease of the new road which is

built by lateritic gravel, guarantee long-term performance of highway, the basic performance of

lateritic gravel is analyzed and summarized, based on the spot investigation and taking related

experiments on different tendering stages and different material sources, Based on the properties

of the lateritic gravel and the practical experience of existing highways, a criterion suitable for

the selection of lateritic gravel used as paving material, under similar climatic conditions to Mali

in the West Africa, has been proposed

Figure 1 The current situation of Bamako-Segou highway

2 MATERIALS AND METHODS

2.1 Materials

A kind of representative soil sample was collected from Bamako-Segou highway engineering

in Bamako in Republic of Mali Some basic properties were tested based on the specification of

JTG E42-2005 and gathered in Table 1 It was shown that the lateritic-gravel had a high water

absorption ratio, a high crushing index value and a high plasticity index, which meant that the

substance might not be appropriated for the current specification

Table 1 Basic properties (by mass) of the concerned soils compared with China standards

Water absorption ratio (%) <3.0 <3.0 8.87 Apparent density (g·cm-3) >2.45 >2.45 2.85 Crushing index value (%) <35 <40 51.4 Flaky and elongated aggregate

100 groups of lateritic gravel were collected and realized by wet sieving according to

T115-1993 The plasticity index(PI) was evaluated according to the ASTM D4318-10ε1 The

Moisture-density was studied by heavy compaction test according to T0131-2007 and Vibration

platform method The compaction property was investigated on the same compaction work

Samples had been prepared for heavy compaction tests with 98 numbers of blows for 3 layers

using 15.2 cm ×17 cm mould and 4.5 kg hammer The same cylinder was used in the vibration

platform test with counterweight of 1.5 kg and vibration time of 8.6 min to get the same

compaction work of the samples in heavy compaction tests CBR tests were performed on

cylinder specimens(Φ15 cm×h15 cm) according to T 0134-1993 The specimens were moulded

at the optimum moisture and the degree of compaction was controlled of 90%, 95% and 98%

with 30, 50 and 98 numbers of blows for 3 layers Three parallel specimens were used for each

degree of compaction

Some specifications of different countries about lateritic gravel used as the packing material were analyzed and summarized A criterion suitable for the selection of lateritic gravel used as a

paving material, was put forward The specification mainly contains three parts: CBR, liquid and

plastic limit and gradation

3 RESULTS AND DISCUSSION

3.1 Degrading characterization

The gradations of 100 groups of lateritic gravel were realized and the uniformity coefficient(Cu) and the curvature coefficient (Cc) were calculated to classify The results were

shown in Table 1 It was seen that the gradation of natural lateritic gravel is generally poor and

only 5 samples had good gradation The uniformity coefficient and curvature coefficient are both

relatively large which shows that the distribution of the particle size is extensive and the

intermediate grain diameter is short The missing grain diameter is less than d30 which is mainly

between 1.5~5.5 It belongs to discontinuous gradation

Table 2 The investigation results of lateritic gravel gradation

Figure 2 The statistical histogram of the material retained ratio of 2 mm~0.075 mm sieve

0~5 5~10 10~15 15~20 20~25 0

5 10 15 20 25 30 35 40 45 50

Figure 3 The statistical histogram of the pass ratio through 0.075 mm sieve

The material retained ratio statistical of 2 mm~0.075 mm sieve and the pass ratio through 0.075 sieve are respectively shown in Figure 2 and Figure 3 Three typical gradation curves of

lateritic gravel were determined and shown in Figure 4 with the upper and lower limit gradation

of non-screening macadam used as subbase filling of the highway and first class highway in the

JTG 034-2000 specification The proportion of fine soil is generally large and 67% of samples

has the fine grained soil whose content of fine grained soil is more than 10% The proportion of

the material retained ratio of 2 mm~0.075 mm sieve whose content is less than 17% is 52% It

does not comply with the specification JTG 034-2000 requirements for particle size distribution

that the content of 0.075~2.36 mm particles used in the base of highway or first class highway

should be at 17%~30% It was noted that the natural lateritic gravel has a poor gradation and

was lack of intermediate grain diameter The result that the natural lateritic gravel without the

treatment is not an ideal road base material is similar to Ashworth (1966) and Yusuf (1984)

3.2 Liquid and Plastic limit

The liquid and plastic limits of 100 samples of the fine soil were tested The results showed that the plastic limit of samples is between 10%~30%, the liquid limit is between 20%~40% and

the plasticity index is between 5~20% The plasticity chart which is plotted by the plasticity

index and liquid limit of all samples is shown in Figure 5 Almost all samples are concentrated in

the A line above, B line to the left and the Ip=9 line above The fine grained soil of lateritic

gravel should be low liquid-limit clay according to the classification of fine grained soil in JTG

E40-2007 It cannot comply with the specification JTG 034-2000 requirements for the crucial

water content coefficient that the liquid limit should be less than 28 and the plasticity index

should be less than 9 (6 in rainy and moist region) for non-screening macadam used as base

(subbase) material

3.3 Compaction Property

As was shown in Figure 6, the vibration platform method and the heavy compaction test were separately carried out in the laboratory, but the results are different It was noted that the

optimum moisture content (OMC) of the lateritic gravel was separately 9.15% and 9.12% and the

maximum dry density was separately 2.215 g/cm3 and 2.251 g/cm3 The maximum dry density

obtained by the vibration platform method is lower 1.5~3% than the results obtained by the

heavy compaction test and the optimum water content is a difference of 0~1.5% The compaction

effect used by the vibration platform method is not ideal The reason is that the fine grained soil

of lateritic gravel accounted for a large proportion The effect of vibration compaction on fine

soil is not obvious and the large particle of lateritic gravel cannot be fully broken So the heavy

compaction test to determine the maximum dry density and the optimum water content is more

appropriate

40 30 20 10 5 2 1 0.5 0.1 0

15 30 45 60 75 90 105

Figure 4 The typical gradation curve of lateritic gravel

1020

Figure 6 The compaction results under different compaction methods

3.4 CBR

The CBR test is widely used to evaluate the strength of lateritic gravel in the pavement design in the tropical area (Manasseh and Agbede, 2011) The specimens were moulded with the

gradation of sample B As was shown in Table 3, it was noted that the CBR value of the lateritic

gravel increased as the compactness increased The CBR value is close to 80 when the degree of

Code of the practice for the design of flexible pavement structures for urban and rural roads

Ivory Coast

Specifications for design of highway pavement

Ghana

The specification for natural materials used as base or subbase

≥80（M）

Note: L: Light traffic; M: Medium traffic

4 PERFORMANCE EVALUATION INDEX

4.1 Performance Evaluation Index of Strength

The technical requirements of the CBR value of the base materials are quoted in some countries, as shown in Table 4 It was noted that the requirement of the CBR value for aggregate

used as the filling of roadbed is 80% and the subbase filling is generally 20~30% According to

the test results, the CBR of natural lateritic gravel used as subbase course complies with most

countries specification requirements for the strength, but the strength of the lateritic gravel is

insufficient when used as the highway base filling, so it needs to be treated On the base of the

strength requirements for CBR of some countries and the test results, the application standard of

the strength properties for the lateritic gravel was determined Natural lateritic gravel can be used

as bottom course of all highway, and the 4-days soaking CBR should be more than 40% for light

traffic road, 60% for medium traffic road and 80% for heavy traffic road or above It cannot be

directly used as the filling of highway road base without treatment

Table 6 The requirements for the crucial water content coefficient of lateritic gravel in

some trunk highways

1 2012 Ivory Coast (Huang,

2014)

“Boundiali Tengrela-Mali Border” highway

-organic matter content

≤0.5%，IP＜20

2 2010 Congo(Brazzaville)

(Qu, 2013)

No 1 Highway in Congo

Without organic matter，IP≤20

(Dong, 2007) GirGir-Karge Road WL≤35，IP≤23

4 1994 The Republic of Mali

(Yu, 1994) Bamako City Road

WL＜50，organic matter content＜0.5%

Middle wet segment IP≤15

4.2 Performance Evaluation Index of Liquid and Plastic Limits

According to the results of the representative gradation lateritic gravel CBR tests, despite the crucial water content coefficient of the lateritic gravel cannot comply with the requirements of

the specification, the lateritic gravel still has good strength properties Therefore, the

requirements of domestic specification on lateritic gravel used as base or subbase filling are too

strict So we summarized the technology requirements of lateritic gravel used as subbase filling

in some trunk highways which were built in recent years in African, as was shown in Table 5 It

was noted that our country began to build lateritic gravel base in Africa since the 20th century,

mid and late 80s The requirement for plasticity index (IP) of the lateritic gravel is 15~18 In

recent years, with the development of project technology and the understanding of lateritic

gravel, the requirements for liquid and plastic limits gradually changed The plasticity index

gradually relaxed to 20, even reached 23, but the liquid limit modified from 50 to 35

Considering the particularity of the hydrological and climatic conditions in Africa, the

requirements for the liquid and plastic limit of the lateritic gravel used as base filling should be

improved: (1) without organic matter; (2) the plasticity index is greater than or equal to 20 and

the liquid limit is greater than equal to 40 in Semi-arid Area; (3) the plasticity index is greater

than or equal to 18 and the liquid limit is greater than equal to 35 in other climatic regions

4.3 Evaluation Index of gradation

The strength and stability of the base are not only affected by the type and performance of aggregate, but also related to the passing rate of the maximum grain size, 4.75 mm, 0.425 mm

and 0.075 mm.(Li and Yan, 2009) The five main control indicators are investigated by citing the

requirements for gradation of lateritic gravel used as subbase filling in the highway of Africa,

shown in Table 6 and the number corresponded to Table 5 Therefore the requirements for

gradation in specification that the content of the particle diameter less than 0.075 mm should be

3~5% are too strict for lateritic gravel For lateritic gravel, if the content of the particle diameter

less than 0.075 mm increased to 5~18%, the plasticity index and CBR comply with the design

requirements, the cushion and base built by lateritic gravel can also be excellent According to

the test results, the friability of lateritic gravel and the experience of engineering projects, the

requirements for gradation of lateritic gravel used as base filling were proposed, as shown in

Table 7 Considering the particularity of the African climate and the geographic span of the road,

the upper passing rate of 0.075 mm sieve relaxed to 20 in Semi-arid Area and is less than 35 in

other climatic regions

Table 7 The gradation controlled index of lateritic gravel used as subbase filling in some

5 CONCLUSIONS

The content of large particle and fine grained soil of the natural lateritic gravel along Bamako-Segou highway cannot comply with the specification requirements for particle size distribution The middle particle size is generally absent and the main missing particle size is 2.36~0.075 mm

Under the same compaction work between the heavy compaction and vibration compaction, the lateritic gravel can be compacted more ideal using heavy compaction method The heavy compaction was recommended to determine the maximum dry density and optimum moisture content

The CBR values of lateritic gravel are closed to 80% in the degree of compaction of 96%

or more, the lateritic gravel can be used as subbase filling of all highway in the West Africa

Based on the properties of the lateritic gravel and the existing engineering projects, the strength, the liquid and plastic limit and gradation performance evaluation indexes were put forward