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In the general Mechanistic-Empirical pavement design guideline, the design parameter normally used in representing the response of stabilised pavement material is the elastic modulus measured from a statically-monotonic compression test. Nevertheless, this elastic modulus may not respond to actual behaviour of real pavement which is subjected to cyclic loading from moving vehicles. Using the elastic modulus in pavement analysis could lead to an inaccurate estimation of the stress-strain relationship which is relevant to a pavement response prediction under traffic loading conditions. In this research, the dynamic modulus of cement-stabilised material measured from Asphalt Mixture Performance Tester was examined to be used as a pavement design parameter with consideration of cyclic (traffic) loading conditions. The laboratory results from this research reveal that the cyclic response of cement-stabilised material in term of the dynamic modulus is not much affected by a variation on temperatures and loading frequencies.However, the dynamic modulus is greatly influenced by cement contents and curing periods. Moreover, the elastic moduli measured based on different strain rates was also examined. In order to compare the effects of modulus to the pavement response, finite element analysis was performed in this research by altering the modulus of base course layer. Flexural modulus of cement-stabilised base material determined by Chummuneerat et al. (2013) was also included in the finite element analysis. The results of the finite element analysis show that a tensile strain at a critical location can be reduced by 20% if the elastic modulus of a base course layer were replaced by the dynamic modulus and the flexural modulus. In addition, stress induced by the traffic load can be evenly transferred to the subgrade layer by applying the dynamic modulus and the flexural modulus in the analysis.

This paper examines the self-cementing phenomenon of the road construction material known as recycled concrete aggregate (RCA). Two RCA types were selected as study materials: (1) high-grade RCA (HRCA), a quality RCA manufactured from relatively high-strength concrete structures; and (2) road base RCA (RBRCA), a high-grade RCA blend combined with brick and general clean rubble (road base material). Laboratory tests were performed to obtain the unconfined compressive strength, indirect tension dynamic modulus, and resilient modulus of the test samples to examine their hardening characteristics when subjected to varying curing periods. These tests were performed in conjunction with microstructure analyses from X-ray diffractometry (XRD) and scanning electron microscope (SEM) techniques. The HRCA samples, which were prepared and subjected to varying curing conditions, transformed from an initially unbound material into a bound (fully stabilized) material. The results of XRD and SEM analyses clearly demonstrate that secondary hydration occurred. The RBRCA samples were able to maintain their unbound granular properties, with nonsignificant self-cementing, thus supporting the hypothesis that the mixing of nonactive materials such as bricks and clean rubble into RCA will lessen the tendency of RCA toward self-cementing.

Hydrated Cement Treated Crushed Rock Base (HCTCRB) is a cement modified basecourse material which the mixture of a standard crushed rock base and cement is disturbed after hydration. The unique production process for HCTCRB is different from that of a common cement-treated base to prevent cementitious bonding in order to maintain the unbound material characteristics with an improvement in material engineering properties. This paper presents the mechanistic-empirical pavement analysis and design for flexible pavements containing HCTCRB basecourse. The resilient modulus presenting the stress dependency behaviour of HCTCRB derived from the repeated load triaxial tests were used as one of the input for the analysis and design. Pavement analyses in this study covered various states of materials i.e., linearity or non-linearity, and isotropy or anisotropy of pavement materials. A three - dimensional finite element analysis of pavement structure was also carried out. The conventional pavement analysis in Australia by Circly software, using the anisotropic and quasi-non-linearity technique, is still deemed reliable in comparison with the various approaches examined in this study. However, there remains a concern regarding the reliability of the single input value of the resilient modulus derived from the resilient modulus tests. The average resilient modulus from the test results appeared to be too high for an effective analysis to be undertaken. Based on the stress-dependent analyses conducted and concerned with the thickness range of the basecourse layer, a typical value for the resilient modulus of HCTCRB was determined.

One of the most common methods used in road-pavement construction is the stabilizing of the conventional pavement base course layer. This is achieved by adding cement or lime to gain better material performance. However, obtaining modulus input parameters from a cement-stabilized base course layer for pavement-response analysis under real traffic conditions has proven difficult in that, to date, only ambiguous results have been produced. Using the flexural modulus or elastic modulus in the response analysis has certain limitations in embracing real pavement behavior under traffic and temperature conditions. Accordingly, a more reliable modulus input parameter for pavement analysis under traffic (cyclic) loads is required to obtain more precise and reliable outputs. Moreover, there is, at present, no test protocol to determine a suitable modulus for a cement-stabilized base material under the cyclic loading regime. This study aims to examine the real dynamic responses of cement-stabilized base course materials with a view to adapting the asphalt mixture performance tester (AMPT), a specifically designed dynamic modulus test machine used on asphalt concrete material. The AMPT dynamic modulus test has as an advantage in that loading and temperature regimes based on real pavement conditions can be rationally simulated and directly applied to the test samples. As such, the dynamic moduli of a cement-stabilized base course material can be obtained under different temperature and loading rates. Moreover, the effects of the dynamic strain range, cement content, and curing duration on the dynamic responses of a cement-stabilized base course material may also be examined. Cement-stabilized base course materials of 4 %, 5 %, and 6 % cement contents (by mass) were used as the study materials.The findings of this study indicate that curing durations and cement contents significantly influence the dynamic modulus values of cement-stabilized base course materials. However, the dyn

The modulus of asphalt concrete material is one of the major input parameters in mechanical-empirical pavement design and analysis. In Australia, current pavement design approaches rely on the resilient modulus of the asphalt material, and visco-elastic behaviour cannot be incorporated into this pavement analysis and design. However, in the USA, the NCHRP 1-37A design guide for Mechanistic-Empirical pavement design (ME design) uses the dynamic modulus to express the intrinsic behaviour of this important input parameter, i.e., the visco-elasticity of an asphalt material, over a range of temperatures and loading frequencies. This study aims to examine whether the dynamic modulus which is converted from a resilient modulus test is different to the resilient modulus when considering as a modulus input for pavement design. Three different asphalt concrete mixes, with varying maximum aggregate sizes of 7, 10, and 14 mm were selected as mix representatives. All test specimens were controlled using a - gyratory compactor to produce a 5% air void. To determine the resilient modulus and the dynamic modulus respectively, a UTM-25P and an Asphalt Mixture Performance Tester (AMPT) were used. In addition, pavement design exercises were performed on pavement structures typical to Western Australia. The exercises evaluated the difference of tensile strains at the bottom of asphalt layer derived from the different input parameters of the resilient and dynamic moduli.

Cement-treated base is a conveniently and effectively stabilised pavement material consisting of a mixture of standard base course materials blended with a prescribed amount of Portland cement and water. The cement-treated base material is suitable for use in high-traffic roads and airfield pavements, and usually provides superior engineering properties compared to standard road base material. However, fully bound or stabilised cement-treated base is a relatively stiff pavement base material which is prone to fatigue failure under repeated loading. In pavement design, current fatigue models for cement-treated base material remain empirical, and there exists a lack in scientific linkage between the models themselves and real fatigue perfor-mance. Consequently, a more reliable fatigue deterioration model for cement-treated base is required in order to maximise the usage of such material in pavements. The provision of ‘bottom-up’ constitutive equations is preferable when seeking a deeper understanding of cement-treated base course behaviour under repeated loading. This study focuses on evaluating the dynamic moduli (i.e., the moduli under cyclic loading conditions), of cement-treated base under traffic loads. The same testing basis used for asphalt concrete was adopted in this research. As such, the dynamic moduli were measured under different temperatures and loading frequencies, based on the dynamic modulus testing protocol for asphalt concrete. Test results revealed that cement content and curing time significantly influence the dynamic modulus of bound cement-treated base course. However, the dynamic modulus property was slightly affected by the changes in temperature and loading frequency within a specific range of testing conditions of the test protocol. At the end of this research, a predictive equation for the dynamic modulus was tentatively put forward. This equation was developed from the relationship of the modulus to the unconfined compressive strength. It

Most road networks in Western Australia (WA) are made of flexible pavement with a relatively thin asphalt wearing course and Dense Graded Asphalt (DGA), a commonly used asphalt mix with a continuous size distribution and a low design air-void of around 3% to 7%. Currently, the input parameters for asphalt material for pavement design in Australia still rely entirely on the resilient modulus which cannot incorporate the visco-elastic behaviour of such material into pavement analysis and design. Unlike the resilient modulus, the recently introduced parameter of the dynamic modulus can express the intrinsic behaviour of the visco-elasticity of an asphalt material. The dynamic modulus can describe the stress-strain relationship of viscoelastic material across a wide range of temperatures and frequencies in the form of the Master Curve. The Master Curve is constructed from a sigmoidal function and the Time-Temperature Superposition principle (TTS) with a second-order polynomial shift factor function, according to AASHTO PP62-09. This study aims to investigate the dynamic modulus of Western Australian asphalt mixes, considering three different mixes with varying maximum aggregate sizes of 7 mm, 10 mm, and 14 mm. For this study, all test specimens were controlled to reach a 5% air-void with a Survopac gyratory compactor. Specimens were then tested with an Asphalt Mixture Performance Tester (AMPT) with a testing range of four temperatures: 4°C, 21°C, 37°C and 54°C, and six frequencies; 0.1 Hz, 0.5 Hz, 1 Hz, 5 Hz, 10 Hz, and 25 Hz, according to AASHTO TP62-07. Moreover, the dynamic modulus predictive equation proposed by NCHRP 1-37A MEPDG was modified and introduced to suit WA asphalt mixes.

This research aims to produce a new predictive model of skid resistance in asphalt concrete, with a particular focus on Thailand. Skid resistance in road pavements is an inherent safety factor affecting vehicle users. Thus improvements in this area will greatly enhance road network safety in Thailand. A skid resistance predictive model, based upon the essential aggregate and mixture characteristics that significantly relate to the skid resistance values of asphalt concrete was developed. In this study, three types of aggregate (limestone, granite and basalt) were collected. These aggregates, obtained from 14 provinces in Thailand were representative of all of Thailand’s aggregates. Petrographic Analysis, Gradation tests, Aggregate Impact tests (AIV), Aggregate Crushing tests (ACV), the Los Angeles Abrasion (LA) test, Soundness tests, Polishing Stone tests (PSV) and the British Pendulum Test (BPT), along with the standard mix design were performed. These procedures determined all the essential characteristics in the mixtures and aggregates of asphalt concrete. The results of the research demonstrate that some aggregate characteristics are statistically significant in their relationship to the skid resistance values of asphalt concrete mixtures. These findings will be embraced in the preventive scheme under the strategic road safety management of the Department of Rural Roads, Thailand.

Shrinkage cracking is a significant problem when using cement stabilised materials in the construction of road pavements. Reflective (upward) cracks travel from the cement stabilised base layer to the top of the asphalt surface can cause water ingress through the underlying pavement layers. This paper examines the shrinkage behaviour of cement-treated crushed rock base as applied to pavement conditions in Western Australia. The testing protocol to examine the shrinkage behaviour of the material was adapted from the cement shrinkage test in Australian Standards, AS 1012.13. The test results showed that the amount of shrinkage in the cement-treated material did not increase with additional amounts of cement. The highest shrinkage values were found for the 2% and 6% cement specimens, where shrinkage was approximately 17% greater than the lowest shrinkage value found for the 4% cement sample. Based on the results of this study, it seems that shrinkage in the samples with relatively higher cement content of 5% and 6% mainly results from loss of water during the hydration reaction process between cement and water. Shrinkage in the low cement content samples of 2% and 3% is governed by the evaporation of excess water after the hydration reaction. The 4% cement content sample demonstrated the optimum cement content when considering the lowest shrinkage values among other cement content samples and an appropriate unconfined compressive strength value.

Hydrated Cement Treated Crushed Rock Base (HCTCRB) is produced by adding 2% Portland cement (by mass) to a standard crushed rock base (CRB) at an optimum moisture condition. The unique production process for HCTCRB is different from that of a common cement-treated base in that a re-mixing process is performed after the hydration of cement, preventing cementitious bonding to maintain the unbound material characteristics with an improvement in material engineering properties. This paper presents the resilient modulus (MR) and permanent deformation (PD) characteristics of HCTCRB after variable hydration periods, water addition during compaction and dryback. The difference in material hydration periods affected the performance of HCTCRB. However, in this study, a consistent performance trend with various hydration periods could not be found. Moisture contents have major influence on the properties of HCTCRB. The results indicate that a higher moisture content gives a more increase in PD and a more decrease in MR of this material. Addition of more water during compaction caused inferior PD and MR performance even though the samples achieved a higher dry density. A dryback process to achieve a dryer condition can improve material performance. After samples were subjected to a dryback process, it was found that samples prepared by adding water during compaction showed a decrease in material performance comparing to samples that were compacted without additional water. Thus, the amount of water addition to mixes during compaction must be controlled.

For road pavements in Western Australia, base layers are usually constructed using hydrated cement treated crushed rock base (HCTCRB) of which the mechanistic properties with the reliable material model are necessary for rational pavement analysis and design. The purpose of this study is to present the experimental results produced from the assessment of the mechanical behaviour of HCTCRB and the material modelling based on the Disturbed State Concept theory-based process. The results reveal that HCTCRB can be treated as cohesive granular material where its internal friction angle (ø) is 43° and its cohesion (c) is 168 kPa. The Disturbed State Concept (DSC) and K-θ model can be used for establishing the relationship between the resilient moduli and the applied stresses. The permanent deformation of HCTCRB can be predicted by using models such as the DSC model and G.T.H. Sweere,’s model, which are presented in this paper. The use of the DSC model shows the advantage of showing the relationship between permanent deformations and applied stresses (σ1, σ3), and these are derived from the resilient modulus equation.

In order to increase the applied efficiency of crushed rock base (CRB) in pavement structure design for Western Australia roads, the material modelling based on the experimental results was investigated, and the disturbed state concept (DSC) was used to predict the resilient modulus of CRB because of its simplicity and strong ability in capturing the elastic and inelastic responses of materials to loads. The actual deformation of DSC, at any loading state, was determined from its assumed relative intact (RI) state. The DSC equation of CRB was constructed by using a set of experimental results of resilient modulus tests, and an idealized material model, namely the linear elastic model, of relative intact (RI) part was considered. Analysis results reveal that the resilient modulus-applied stress relationships back-predicted by using the DSC modelling are consistent with the experimental results, so, the DSC equation is suited for predicting the resilient modulus of CRB specimen. However, the model and the equation coming from the test results are conducted in accordance with the Austroads standard, so further investigation and validation with respect to the field behaviours of pavement structure should be performed.

In North America, cement-modified soil (CMS) is described as a soil that has been treated with a relatively small amount of cement in order to improve its engineering properties and make it suitable for construction purposes. CMS leads to a typical soil stabilisation technique employed in Western Australian base course material: hydrated cement treated crushed rock base (HCTCRB), which incorporates an additional hydration process which differs from the original CMS technique. However, because the HCTCRB technique was developed mainly by an empirical approach based on pavement trials, it is posited that HCTCRB itself may be inconsistent with regard to fundamentals such as quality control and uniformity of elements. This then causes uncertainty during the application of HCTCRB with regard to its essential qualities, mix proportion, mixing and curing processes, and construction processes. The effects of these ambiguities need to be better understood in order to maximise the application of this material to new pavement design methods where reliability and consistency is crucial.This study aimed to comprehensively investigate the effects on HCTRB of the amounts of mixing water added, hydration period, and compaction effort on physical properties (ie. gradation and surface properties), and mechanical properties (ie. shear strength parameters, resilient modulus and permanent deformation) using scanning electron microscopy (SEM), conventional triaxial tests and repeated load triaxial tests. HCTCRB demonstrates superior performance to the original material in terms of resilient modulus and permanent deformation. SEM and static triaxial tests revealed that crushed rock base shows higher internal friction angles but less cohesion than HCTCRB. The hydration period of HCTCRB during the manufacturing process was found to have an insignificant effect on particle size distribution. However, hydration period does affect the permanent deformation and resilient modulus characteristics

About 25 million tonnes of bauxite residue from alumina refining are generated in Australia each year. Managing this residue is costly, and the reuse of coarse bauxite residues is becoming an increasingly attractive and sustainable solution to the problem. Using coarse bauxite residue in road construction has the potential for large volume reuse. This study investigated whether coarse bauxite residue is a viable road base material in Western Australia. A pozzolanic stabilised mixture was created to improve the properties of the residue, to satisfy the minimum requirements for road base. Laboratory tests for resilient modulus and permanent deformation were then performed. Comparisons were made between the stabilised residue and conventional road base material used in Western Australia. The performance of the stabilised residue was superior to that of the conventional material, and can provide improved performance when used as road base material in Western Australia.

Conventional laboratory CBR test has been widely used for predicting bearing capacity of subgrade layer for pavement design. In unsaturated soil, suction is one of the key parameters for understanding the soil behavior. The analysis of CBR is commonly presented in CBR-water content relation. The information of CBR based on soil suction is very rare and more study is still required. This paper presents a laboratory experiment of CBR test with direct suction measurement. Suction-monitored CBR test is introduced by attaching tensiometers on CBR mold and its surcharge. The standard compacted test on various proportions of sand-kaolin clay mixtures starting from 0% (pure sand), 5%, 10%, and 20% of clay were used. The tests were performed with different value of water content in both soaked and unsoaked conditions. The results indicated that the CBR versus matric suction forms a bi-linear curve. The discussion is presented in term of CBR-water content and CBR-matric suction relation.

Fatigue cracking is considered to be one of the most important types of distress affecting the performance of flexible pavements on major highways. This report analyses the results of a laboratory study of the static and fatigue response of a typical Western Australia Cement Treated Base (CTB) to evaluates its mechanical parameters i.e. flexural strength, flexural stiffness and tensile strains. Five different series of cement content were evaluated in the mix of 1%, 2%, 3%, 4% and 5%. Two major types of testing were conducted for the purpose of this study, i.e. Flexural Fatigue Tests (dynamic loading) and Flexural Beam Tests (static loading). The flexural fatigue tests were carried out with strain control mode. From the tests, the flexural stiffness for each specimen was calculated. The flexural stiffness was obtained from maximum tensile strains on the bottom of the specimens. The outcomes of the paper are as summarized as follow: First, 1% to 3% CTB was found out to be classified as modified material while 4% and 5% CTB are categorized as stabilized materials. Second, fatigue cracking phenomenon can be seen in stabilized materials (4% and 5% CTB) while other types of distress may affect the behavior of modified materials (1 to 3% CTB). Third, 4% cemented material is observed to be the most suitable material to perform under fatigue loading conditions. Fourth, a series of recommendations are presented for further research i.e. the Flexural Fatigue Test be conducted at a suitable (lower) strain value instead of the 400 µe magnitude used in this research. © 2012 Taylor & Francis Group.

This study aims to introduce an alternative design model of unbound granular base course materials by utilising laboratory test results such as resilient modulus, permanent deformation and bearing capacity of base course materials. Current pavement designs mostly overlook all problematical behaviours of unbound granular base layers and consider only as a layer transferring traffic loads to underneath layers regardless on the unbound granular base course deteriorations. Based on the existing design protocols in Australia, there are only the design criteria of the horizontal tensile strains at the bottom of the asphalt layer and the vertical deformations occurring at the top of the subgrade. The actual performances of granular base course materials under traffic loads have been rarely accounted into the pavement design protocol. Currently, road activities are growing in terms of magnitude and frequency far beyond the past and causing the early road damages leading to major road maintenances. The study presents hypothetically the more ratiotial approach of the stress and strain distribution in a flexible pavement using the finite element method with sophisticated laboratory results. In this study, the effects of a traffic load and material attributes which they were generated when vehicle travels, hence stress and strain contributing between tires and characteristics of unbound granular pavement materials were investigated. Moreover, the alternative design model for unbound granular layers was defined in order to draw up the guideline and recommendation on the current pavement analysis and design. © Institution of Engineers Australia, 2012.

Hydrated Cement Treated Crushed Rock Base (HCTCRB) is a cement stabilized base course produced by adding 2% Portland cement to standard crushed rock base. The mix is stockpiled for specified hydration period and then retreated to retain unbound property. HCTCRB has been used based on empirical approach and experiences causing uncertainty during production and construction processes. Consequently, the material characterisation of HCTCRB in accordance with the pavement mechanistic approach is strongly required to understand the material behavior to maximize its uses. This paper aims to present the mechanical characteristics of HCTCRB in terms of resilient modulus using repeated load triaxial tests. The experiments were conducted to study the influences of various factors during production process (i.e. cement content, mixing moisture content and hydration period) on HCTCRB properties. HCTCRB were also examined its conformity to the definition of modified granular materials, according to Austroads standard.

Increased popularity of foamed bitumen as a stabilising agent in recent years has resulted in a necessity for research into the material properties of foamed bitumen stabilised pavements, and the effects of varied design parameters on these properties. The objective of this project is to assess the effects of aggregate gradation in foamed bitumen mixes on material properties characteristics and mechanical performance. The focus was given into the fines particle percentage: that is, particles with a nominal diameter of 75µm or less, as it is recognised that this range of particle sizes has a significant effect on binding capabilities of foamed bitumen. The results were obtained by comparing a number of samples of ranging from 0% to 25% fines at 5% increments, and with 0%, 2% and 4% foamed bitumen contents. Comparisons were drawn by testing typical material properties of unconfined compressive strength, indirect tensile strength and indirect tensile resilient modulus. Test results indicated that deficient productions were yielded and nubby bitumen was easily to be observed with a lower amount of fines content. However, the higher fines content was detrimental to the mechanical strength which was mainly relied on the interlock between coarse particles.

Crushed concrete waste is a by-product from building demolition and constitutes a principal component of municipal solid waste consisting of concrete, sand, brick, rock, metals and timber. Over 50% of this waste is commonly sent to land-filled sites, resulting in the impact on the limited capacity of land-filled sites. Nowadays, the sources of virgin natural aggregates are depleted by increasing in demand of using a virgin material in building and infrastructure construction and maintenance facilities. This depletion leads to the utilisation of crushed concrete waste to replace natural aggregates in road and highway construction. Of key significance of this study is to present alternative materials for road and highway construction on the production of the proper guideline for road base by using crushed concrete waste. Sophisticated tests were conducted to investigate the mechanical responses of compacted crushed concrete subjected to applied loads simulated from traffic loads. Unconfined compressive strength, shear strength parameters, resilient modulus and permanent deformation of such material were determined. Our findings showed that crushed concrete waste is able to utilise as a road base material. The results of this study will enhance increased use of crushed concrete waste in road and highway construction and will, therefore, alternatively reduce consumption and costs in manufacturing virgin aggregates.

Hydrated Cement Treated Crushed Rock Base (HCTCRB) is produced by adding 2%-Portland cement with standard crushed rock base. The mixture is disturbed after the specific hydration period to prevent setting up and retain its unbound property. HCTCRB has been commonly adopted for Western Australian roads, however based on empirical method and experiences. Thus, the characterisation of HCTCRB following the pavement mechanistic approach is needed. This paper aims to presents the performances of HCTCRB in terms of permanent deformation and resilient modulus. The repeated load triaxial tests were performed to study the performances of HCTCRB that affected by manufacturing (hydration period) and construction procedures (amount of water added during compaction and dry back). This study has found that HCTCRB exhibited the stress dependent behaviour. All these studied factors significantly affect the resilient performances of HCTCRB in dissimilar trends. The certain impact on the material performances related to the hydration periods still could not be concluded. The higher water addition even at the optimum moisture content of HCTCRB resulted in the poorer performances, although it induced the higher dry density, which indicated that the HCTCRB is still susceptibility to moisture content. The dryback process has potential to improve the material performances of the material in different level which depends on amount of additional water. All the tested results indicated the significant influence of moisture content to the performances of HCTCRB with regardless of the dry density.

To design road pavement in Western Australia, Hydrated Cement Treated Crushed Rock Base (HCTCRB) is normally used as base course material. HCTCRB has been used and designed based on practical experience and empirical approach but these cannot explain the behaviour of HCTCRB base course. Currently, analysis and design and behaviour of structural pavement can be more reliable and more understood by the use of a mechanistic approach, one of which is the Disturbed State Concept (DSC). The purpose of this study is to assess the mechanical characteristics of HCTCRB by modelling the results of laboratory tests using DSC. Conventional triaxial tests and Repeated Load Triaxial (RLT) tests, following the Austroads-APRG 00/33 test standard, were performed and the experimental results were used to construct the DSC equation for HCTCRB. Also, the effect of moisture content on the behaviour of HCTCRB was investigated. The results reveal that the resilient modulus characteristics of HCTCRB can be modelled by the use of the proposed DSC equation.

Current road design and analysis approaches lack an appropriate model to fill the gap between past empirical and mechanistic empirical methods. The current approaches also lack current developments in pavement materials, traffic loading and importantly the rate at which traffic loading develops in thedesign period. This causes road disruptions well before the design life reach. Early road damage can lead to other road issues including serious accidents. In this paper, we aim to visualise road segment to allow for all the important analysis and design factors affecting actual pavement performance. As a result, all sectors of the road system are analysed and designed to simulate the road system.

Foamed bitumen stabilisation is a road construction technique where hot bitumen is converted to bitumen foam by injecting a small quantity of cold water into it. It is mixed into the road pavement to bind existing or imported granular materials to produce a bound but flexible pavement with superior structural properties to the original pavement. There have been trials and research projects undertaken in Australia by Queensland Main Roads, some regional road networks in New South Wales, and City of Canning, Perth, where the process has been adopted as a preferred rehabilitation method, but these projects did not develop a complete understanding of the characteristics and performance of in-situ foamed bitumen stabilised pavements for Australian conditions. This paper reviews the results of research undertaken into the stiffness and fatigue performance of insitu foamed bitumen stabilised pavement materials at various sites in the Cities of Canning and Gosnells in Western Australia. The aim of the research was to determine if a design relationship could be developed to predict the fatigue life of insitu foamed bitumen stabilised pavements, and if the visco-elastic properties of the bitumen binder were reflected in the stiffness and fatigue performance.

Hydrated Cement Treated Crushed Rock Base (HCTCRB) is widely used as a base course in Western Australian pavements. HCTCRB has been designed and used as a basis for empirical approaches and in empirical practices. These methods are not all-encompassing enough to adequately explain the behaviour of HCTCRB in the field. Recent developments in mechanistic approaches have proven more reliable in the design and analysis of pavement, making it possible to more effectively document the characteristics of HCTCRB. The aim of this study was to carry out laboratory testing to assess the mechanical characteristics of HCTCRB. Conventional triaxial tests and repeated load triaxial tests (RLT tests) were performed. Factors affecting the performance of HCTCRB, namely hydration periods and the amount of added water were also investigated. It was found that the shear strength parameters of HCTCRB were 177 kPa for cohesion (c) and 42° for the internal friction angle (f). The hydration period, and the water added in this investigation affected the performance of HCTCRB. However, the related trends associated with such factors could not be assessed. All HCTCRB samples showed stress-dependency behaviour. Based on the stress stages of this experiment, the resilient modulus values of HCTCRB ranged from 300 MPa to 1100 MPa. CIRCLY, a computer program based on the multi-layer elastic theory was used in the mechanistic approach to pavement design and analysis, to determine the performance of a typical pavement model using HCTCRB as a base course layer. The mechanistic pavement design parameters for HCTCRB as a base course material were then introduced. The analysis suggests that the suitable depth for HCTCRB as a base layer for WA roads is at least 185 mm for the design equivalent standard axle (ESA) of 10 million.

Soil stabilisation is the alteration of one or more soil properties, by mechanical or chemical means, to create an improved soil material possessing the desired engineering properties. In pavement engineering, soils as a main pavement construction material may be stabilised or/and modified to increase strength and durability or to prevent erosion and dust generation. This paper will report the relevant design and the practical viewpoints of soil stabilisation in Western Australia pavements. The Hydrated Cement Treated Crush Rock Base (HCTCRB) material and the foamed bitumen stabilised material will be demonstrated through their mix design philosophy, laboratory and field investigation, and performance.

Recycled crushed concrete and demolition materials have been trailed successfully as a road construction material in a number of locations in Western Australia, but industry acceptance of the material has been minimal. Specifications of such materials currently in use have been modified from commonly used specifications for new quarried products, and remarkably, there have been some doubts about the long term performance and quality control of such recycled products. This paper analyses the performance of recycled concrete pavements that have been constructed in Western Australia, and details the extensive laboratory testing program undertaken to model the product and compare its performance to conventional quarry products. Field testing demonstrates good quality control and performance of recycled crushed concrete and demolition materials superior to conventional quarry products and the laboratory results shows very close characteristics between both materials. © 2012 Taylor & Francis Group.

Fatigue cracking is considered to be one of the most important types of distress affecting the performance of flexible pavements on major highways. This report analyses the results of a laboratory study of the static and fatigue response of a typical Western Australia cement treated base (CTB) to evaluates its mechanical parameters i.e. flexural strength, flexural stiffness and tensile strains. Five different series of cement content were evaluated in the mix of 1%, 2%, 3%, 4% and 5%. Two major types of testing were conducted for the purpose of this study, i.e. Flexural Fatigue Tests (dynamic loading) and Flexural Beam Tests (static loading). The flexural fatigue tests were carried out with strain control mode. From the tests, the flexural stiffness for each specimen was calculated. The flexural stiffness was obtained from maximum tensile strains on the bottom of the specimens. The outcomes of the paper are as summarised as follow: First, 1% to 3% CTB was found out to be classified as modified material while 4% and 5% CTB are categorized as stabilised materials. Second, fatigue cracking phenomenon can be seen in stabilised materials (4% and 5% CTB) while other types of distress may affect the behaviour of modified materials (1 to 3% CTB). Third, 4% cemented material is observed to be the most suitable material to perform under fatigue loading conditions. Fourth, a series of recommendations are presented for further research i.e. the Flexural Fatigue Test be conducted at a suitable (lower) strain value instead of the 400 µe magnitude used in this research.

Hydrated cement treated crushed rock base (HCTCRB) is generally used as base course material for road pavement in Western Australia. Most of road pavement in Western Australia is normally designed using thin asphaltic concrete layer, therefore base layer must behave as a main flexural member that resisting the bending stress from traffic loads and pavement engineer have to design this layer carefully. Although the mechanistic approach for analysis and design of road pavement has been introduced in Australia for several decades, most of road and highway agencies in Western Australia still rely on the empirical method. However, behaviour of pavement structure can be clearly understood by using the mechanistic approach, better than using the empirical approach. Due to the mechanistic approach commonly uses the resilient modulus for analysis of structural pavement, therefore the aim of this paper is to develop a mechanistic model for predicting the resilient modulus of HCTCRB by the use of the disturbed state concept (DSC). The model was derived based on the experimental results of HCTCRB specimens which were tested by adhering the standard test method of the Austroads – APRG00/33. Then the DSC equation for predicting the resilient modulus of HCTCRB specimen, including the effect of hydration period, will be introduced. The results indicate that the use of the proposed DSC equation to back-predict the resilient modulus of HCTCRB specimens gives consistent value with the experimental results.

Currently, the introduction of the gyratory compactor replicating the kneading action of the field compaction raises a though that the conventional 75 blows of Marshall compaction effort would be insufficient to simulate field compaction of the foamed bitumen stabilisation material. Furthermore, the strong laboratory specification of a particular compaction method for the foamed bitumen mixture has not yet been established, therefore the future study in the compaction of the foamed bitumen mixture is needed. This laboratory based study aims to verify the reliable compaction effort for the foamed bitumen mixture. In this study, virgin materials treated with different foamed bitumen contents were compacted by Marshall Compactor and Gyratory Compactor at various blows/cycles, respectively. Upon completion of compaction and curing, density, indirect tensile strength and indirect tensile resilient modulus were performed to determine the suitable compaction technique for such materials. It is expected that the compaction effort achieved the highest density and tensile strength would be selected to compare with field compaction further.

Many factors affect the strength and durability of foamed bitumen treated materials, such as binder content, active filler type and content, aggregate composition and gradation, moisture content, compaction effort, and curing regime. This preliminary study investigates the effects of bitumen and active filler on standard mechanical test results. The results failed to demonstrate any consistent trend with bitumen content variation; however, four percent foamed bitumen appears an optimum value in some cases. The addition of cement always resulted in the highest mechanical performance, compared with the addition of hydrated lime and quicklime.

About 25 million tonnes of bauxite residue (BR) from alumina refining are generated in Australia each year. Managing this residue is costly, and the reuse of coarse BRs is becoming an increasingly attractive and sustainable solution to the problem. Using coarse BR in road construction has the potential for large volume reuse. This study investigated whether coarse BR is a viable road base material in Western Australia. A pozzolanic-stabilised mixture was created to improve the properties ofthe residue to satisfy the minimum requirements for road base. Laboratory tests for resilient modulus and permanent deformation were then carried out. Comparisons were made between the stabilised residue and conventional road base material used in Western Australia. The performance of the stabilised residue was superior to that of the conventional material, which can provide improved performance when used as road base material in Western Australia.

A high quality of natural aggregates is demanded for use in pavement construction and the sources, which are becoming scarce. The search for alternative materials to minimize the utilization of natural aggregates and provide a significant substitute has led to the utilization of Construction and Demolition (C&D) waste. This paper describes a preliminary examination of the engineering issues relating to the utilization of C&D waste as a base course material for Western Australia roads. A series of laboratory tests were performed during which Repeated Load Triaxial (RLT) tests were conducted to determinethe resilient modulus and permanent deformation characteristics of C&D waste and the commonly used base course material, Crushed Rock Base (CRB), as a reference material. A comparison of test results of both materials then was made. CIRCLY, a computer program based on the multi-layer elastic theory was used in the mechanistic approach of pavement design and analysis to determine the performance of a typical pavement model using C&D as a base course layer. Based on the study’s findings, C&D waste should be considered an adequate substitute for traditional aggregate in Western Australia road construction.

Increased popularity of foamed bitumen as a stabilizing agent in recent years has resulted in a necessity of research into the mechanical characteristics of foamed bitumen mixture rather than material itself. The objective of this project is to assess these mechanical properties of foamed bitumen mixtures in terms of variants on bitumen contents and active filler contents. Specifically, a laboratory blend host material was mixed with 0%, 2%, 4% of foamed bitumen and 0%, 1%, 2% of hydrated lime, respectively, by mass of aggregate. Comparisons were drawn by testing typical mechanical properties of Static tri-axial test, Resilient Modulus test and Permanent Deformation test. Test results indicated the basic mechanical properties of foamed bitumen mixtures under Western Australian laboratory conditions. © 2012 Taylor & Francis Group.

This paper presents the resilient modulus (MR) of Hydrated Cement Treated Crushed Rock Base (HCTCRB) affected by amount of hydration periods, compaction processes and dryback using the repeated load triaxial tests. The related trends of MR correspond to the different hydration periods still cannot be concluded. Instead, It was found that the moisture content play more major influence on the MR performance. Higher additional water during compaction of HCTCRB, even at its OMC and induced higher dry density, led to the inferior MR performance compared to the sample without water addition. The MR of damper samples could be improved through dryback process and superior to that of the sample without water addition at the same moisture content. However, the samples without water addition during compaction delivered the comparable MR values even its dry density was lower than the other two types. These results indicated the significant influence of moisture content to the performances of HCTCRB with regardless of the dry density. Finally, the experimental results of HCTCRB and parent material were evaluated with the K-? model and the model recommended by Austroads. These two models provided the excellent fit of the tested results with high degree of determination (R2).

Moisture ingress is a primary catalyst for pavement damage and plays a key role in the performance of pavement materials in service. Moisture intrusion eventuates to early development of deficiencies (potholes) due to “pumping” effects and reduced effective strength of the pavement. Cement stabilisation is one of the preventive measures that are applied to minimise moisture ingress into pavements. This study utilises the Tube Suction Test (TST), developed by Texas Department of Transportation (TxDOT), to assess its robustness as an engineering tool to measure moisture ingress and to determine the relationship between water ingress and cement content. The TST is a non-destructive testing method that measures the dielectric value (DV) of materials which is a measure of the moisture content. Mixes ranging from 1% to 6% cement content by mass are tested. The results allow the determination of a DV tangent which potentially characterises the moisture susceptibility of stabilised material. Results also show that a marked improvement in moisture susceptibility is achieved with 3% cement content. Preliminary results obtained from this study shows that TST may have the potential for industrial application but will require further investigations.

Hydrated Cement Treated Crushed Rock Base (HCTCRB) is a modified base course material, with anadditional of 2% Portland cement (by mass) to a standard crushed rock base. Based on the HCTCRB application protocol, the mix is retreated after hydration to avoid producing the base course material as a bound material. HCTCRB has been usually implemented to the Western Australian road networks based on empirical design and application with experiences. Accordingly, the material characterisation of HCTCRB in accordance with the pavement mechanistic approach is strongly required to understand its behaviours and performances under the service stage. This paper aims to present the mechanical behaviour of HCTCRB resulting from the repeated load triaxial tests. Testing results of HCTCRB in terms of resilient modulus (MR) were investigated and compared to that of standard crushed rock. It wasfound that HCTCRB technique greatly improved the performance of the parent materials about triple. The results also indicated that the hydration periods significantly affected the performances of HCTCRB. CRB and HCTCRB samples exhibited the stress dependences. Generally, the deviator and confining stresses considerable affected the resilient responses of the materials as the increase of the applied stresses resulted in the higher MR values but lower incremental rates of MR. At constant confining pressure, the MR increased with increasing deviator stresses. However, the incremental rates decreased at higher levels of confinements. Similarly, at constant deviator stress, the MR climbed upwith higher confining stresses and the rates of increase were less pronounced at higher deviator stress levels. Several constitutive models for determining the MR were examined based on the laboratory results. These evaluations suggest that the K-model is still useful for modelling of these materials due to its simplicity and high degree of determination.

Crush Rock Base (CRB) is a commonly used road base material for Western Australia Roads. In order to increase the efficiency of using this material in pavement structure design, material modelling for analysis which is based on experimental results needs to be investigated. This paper is a preliminary study of the use of the Disturbed State Concept (DSC) to predict the resilient modulus for CRB. DSC was adopted as the modelling approach because of its simplicity and yet is powerful in capturing the elastic and inelastic responses of materials to loading. The main assumption of DSC is that the actual material deformation, at any loading state, can be determined from its assumed relative intact (RI) state. The DSC equation of CRB has been constructed by using a set of the experimental results of the resilient modulus tests and an idealised material model, namely the linear elastic model, of the relative intact (RI) part was considered. The results reveal that the resilient modulus-applied stress relationships, which were back-predicted using the DSC modelling, were consistent with the experimental results. The DSC equation, which is suited for predicting the resilient modulus of CRB specimens, will then be introduced.

Hydrated Cement Treated Crushed Rock Base (HCTCRB) is produced by adding 2% Portland cement (by mass) to a standard crushed rock at an optimum moisture condition. The unique production process of HCTCRB different from that of a common cement treated base is the remixing process which is performed after the hydration of cement. This prevents cementitious bonding and maintains unbound material characteristics with an improvement in material engineering properties. This study aims to examine the resilient modulus (MR) and permanent deformation (PD) of HCTCRB under various conditions of water addition during compaction and dryback. The results indicate that the higher the moisture content of HCTCRB, the poorer the PD and MR performance. Higher addition of water during compaction causes the inferior PD and MR performance even though the samples achieved the higher dry density. The dryback process to achieve the dryer condition can improve the material performance. After the test specimens were subjected to the dryback process, it was found that the samples prepared by adding water during compaction resulted in poorer material performance in comparison to that of the samples that were compacted without additional water. Thus, the amounts of water added to mixes during compaction must be closely monitored.

This paper aims to report the mechanical behavior of crushed rock base (CRB) and hydrated cement treated crushed rock base (HCTCRB) as granular road base materials subjected to repeated cyclic loads from Repeated Loads Triaxial (RLT) tests with various stress paths in order to improve more understanding of such Western Australian roads based materials on mechanistic-empirical pavement design and analysis. As is well known, pavement surface rutting, longitudinal and alligator cracks are normally the main cause of damage in flexible pavements. The factors contributing to such damage are the excessive irreversible deformation of base layers and the behavior of a mechanical response of unbound granular materials (UGMs) under traffic loads which at the moment are not well understood. In this study, the shakedown concept was utilized to describe and determine limited use of CRB and HCTCRB subjected to different stress conditions. This concept is a theoretical approach used to describe the behavior under RLT tests. It utilizes macro-mechanical observations of the UGM's response and the distribution of the vertical plastic strain in the tested material. When the shakedown limit of an UGM is known, the limitations of the accumulated plastic strain in an unbound granular layer which causes rutting can be predictable. In this paper, compacted CRB and HCTCRB samples were subjected to the various stress condition defined by the stress ratio (the ratio of a vertical major stress, σ1 and a horizontal minor stress, σ3) in order to simulate the real condition of pavement. The study revealed that road base defined the working stress ratio of a pavement structure and that after a large number of traffic loads, deterioration will occur. Moreover, the mechanical responses were investigated and the limit ranges of using UGMs in pavements were determined.

This study aims to report the possible use of fibre to improve the tensile strength of crushed rock base in a pavement in order to reduce the cracking of cemented material. As well is known, stabilized materials always present brittle responses under applied loads and suddenly collapse after peak loading. From this point, it means that cemented material only advances compressive behaviour and will never enhance long term performances such as fatigue and durability. Cemented crushed rock with fibre was selected to represent the tensile strength of pavement base material. Sophisticated tests were conducted to observe mechanical responses under applied loads such as indirect tensile and unconfined compressive strength, and the resilient modulus. The test results showed that fibre reinforcement improved the tensile strength and ductility of stabilized materials.