Abstract: Nanotechnology application to concrete presents an innovative approach to improve concrete properties based on the ability to manipulate the cementitious material at an atomic scale. This paper presents a review of the nano-materials that have been used in concrete. The literature survey revealed that four nano-materials are most often used to modify concrete properties; these include nano-silica (nano-SiO2), nano-titanium dioxide (nano-TiO2), carbon nano-tubes (CNTs) and carbon nano-fibres (CNFs). All of these four nano-materials have shown improvement in many concrete properties. Both nano-TiO2 and nano-SiO2 reduce bleeding and segregation, and improve mechanical and transport properties. CNFs and CNTs tend to adversely affect the fresh properties due to agglomerations, which are overcome when a surfactant or ultrasonic mixer is used. However, both CNFs and CNTs significantly improve the mechanical properties of concrete. This paper also discusses how concrete durability is improved when nano-materials ...

Abstract: The objectives of this research are to evaluate the susceptibility of aggregates and asphalt binder with and without liquid antistrip (LAA) additives to moisture damage based on the properties that affect the adhesion bond between the aggregate and asphalt binder and the cohesion strength of the asphalt binder using the surface free energy (SFE) concept and laboratory testing. The percentage of the aggregate surface area that was exposed to water (P) due to each cycle was used as a screening parameter for evaluating the compatibility of the asphalt binder and aggregates in terms of the resistance to moisture damage. The results show that adding LAA causes the total SFE of the asphalt binder to increase, which results in a decrease in stripping between the aggregate and asphalt binder in the presence of water. Similar results were obtained from a dynamic modulus test. From the data obtained, we conclude that LAA caused a reduction of the magnitude of P that improves its resistance to moisture damage.

Abstract: This study evaluated the effect of the pavement design parameters on the behaviour of orthotropic steel bridge deck pavements under traffic loading using a three-dimensional finite element model. Four types of paving materials were considered in this analysis: polymer concrete, epoxy asphalt concrete, polymer-modified stone mastic asphalt concrete and mastic asphalt concrete. The maximum transverse tensile strain was developed at the bottom of the pavement under a tyre of dual tyres or on top of the pavement between two tyres. From the sensitivity analysis, better interface bonding between the deck plate and pavement led to a significant enhancement of bottom-up fatigue cracking resistance, especially for 40-mm-thick pavements. As pavement temperature increased from − 20 to 60°C, critical tensile strain increased significantly, and corresponding locations moved from the bottom to the top of the deck pavement.

Abstract: The construction, maintenance and disposal of asphalt pavements may lead to considerable environmental impacts, in terms of energy use and emissions during the life of the pavement. In order to ena ...

Abstract: This paper presents an experimental study in which field survey and laboratory tests were conducted to evaluate the performance of asphalt patching mixtures designed for winter season pothole repairs. Special laboratory procedures, including adhesiveness, cohesion, moisture susceptibility and loaded wheel tests, were investigated and modified to evaluate the bonding, freeze–thaw resistance and rutting potentials of the patching materials. The influence of different factors, including freeze condition, traffic level, speed limit, patch size and depth, on patching performance was analysed based on a statistical analysis of 6-month field survey. Effects of testing conditions were investigated for testing pothole patching materials with cohesion, freeze–thaw and loaded wheel tests. It was found that testing temperatures, laboratory sample compaction efforts as well as wheel loading in loaded wheel test significantly affected the testing results of pothole patching materials. Proper modifications were recommen...

Abstract: A finite-element response model was developed using ABAQUS software package to investigate the effect of geogrid base reinforcement on the response of a flexible pavement structure. Finite-element analyses were then conducted on different unreinforced and geogrid-reinforced flexible pavement sections. In this analysis, the base course (BC) layer was modelled using an elasto-plastic bounding surface model. The results of the finite-element analyses showed that the geogrid reinforcement reduced the lateral strains within the BC and subgrade layers, the vertical strain and shear strain at top of subgrade, and the surface permanent deformation. The higher tensile modulus geogrid resulted in larger reduction of surface permanent deformation. Based on the response parameters computed from the finite element analysis, the improvement of using geogrid for BC reinforcement was then evaluated using the damage models for rutting in the mechanistic–empirical method developed through NCHRP Project 1-37a. The results o...

Abstract: The presence of water flow on road surfaces may lead to early deterioration of bituminous pavements. The adverse impacts of various anti-freezing materials on road surface performance have drawn the attention of many researchers. However, the simultaneous effects of salted water and water flow on the deterioration of road surfaces, particularly under freeze–thaw conditions, have not been adequately addressed. This research aims to study the combined effects of water flow and anti-freezing materials, which are usually present in the vicinity of asphaltic pavements during freeze–thaw cycles, on asphalt concrete deterioration. Two sets of asphalt concrete samples were prepared and subjected to six exposure states. The samples were also tested in an abrasion test apparatus and subjected to normal and frictional forces. Marshall strength loss and weight loss of the samples were measured and the results were analysed. The results indicated that the combined effects of water flow and de-icers under freeze–thaw c...

Abstract: The forward models frequently adopted for use in the dynamic backcalculation of the falling weight deflectometer (FWD) data are based on the solutions that utilise discrete transforms In this paper, a new computational algorithm, namely ViscoWave, has been developed and implemented for modelling the pavement dynamics under the FWD impact load The primary advantage of the proposed solution over some of the existing solutions is that it uses continuous integral transforms (Laplace and Hankel transforms) that are more appropriate for the FWD time histories whose signal characteristics are transient, non-periodic and truncated Sample runs of the ViscoWave and the validation efforts presented in this paper showed that the proposed algorithm is capable of modelling the dynamics of a layered structure with elastic or viscoelastic material with or without a halfspace, indicating the potential of ViscoWave as a forward model for dynamic backcalculation of flexible pavement properties

Abstract: This paper investigates the effect of including randomly spaced palm fibres in a soil matrix. The fibres in date palm have special properties such as low costs, plenitude in the region, durability, lightweight, high tension capacity and relative strength against deterioration. Thus, it is possible to use the palm fibres as an alternative low-cost natural material for soil reinforcement. As the objective of this research was to mix the soil and date palm fibres to use in the construction of soil roads, especially village road, we discuss the influence of date palm fibres on CBR (California Bearing Ratio) strength of fine sand. CBR tests were conducted under dry and submerged conditions. The durability of fibres was also investigated using the plain fibres and fibres coated with bitumen. Some samples were soaked for several months before being loaded. The results show that the addition of palm fibres increases the CBR strength of the sand specimens significantly. It is also seen that the sliding strength co...

Abstract: Full-depth reclamation (FDR) techniques for pavement construction and rehabilitation have gained general recognition because of their technical, economical and environmental advantages. The use of cement–bitumen-treated material (CBTM) has rapidly increased over the last 10 years mainly in motorways. Public administrations have recognised the advantages of FDR, and this technique has also begun to be applied for the rehabilitation of local and/or rural roads. This paper shows the results from a trial section built to verify the suitability of FDR for the rehabilitation of local roads. The design planned the in situ stabilisation with styrene-butadiene-styrene (SBS)-modified bituminous emulsion and cement of hot mix asphalt and foundation course. The mechanical characteristics of CBTM were evaluated by means of stiffness modulus tests at different temperatures and fatigue tests. The obtained results offer good prospects for the application of FDR in the maintenance project of local roads.

Abstract: Timely rehabilitation and preservation of pavement systems are imperative to minimising agency's costs and maximising benefits. Reasonable estimates of treatment life and pavement life extension can be made possible by developing reliable treatment performance models. Louisiana Department of Transportation and Development initiated a three-phased study to develop pavement treatment performance models in support of cost-effective selection of pavement treatment type and the time of treatment. As a result of the study, international roughness index (IRI) models for overlay treatment of composite and flexible pavements were developed. Various factors affecting the IRI of overlay treatment were identified. Climatic indices pertaining to Louisiana were developed which exhibited strong statistical significance along with the other variables as used in the IRI models. The developed IRI models provided good agreement between the measured and predicted IRI values with the majority of data within 5% of prediction e...

Abstract: Enhancing the quality of granular layers is fundamental to optimise the structural performance of the pavements. The objective of this study is to investigate whether previously developed packing theory-based aggregate parameters can evaluate the resilient modulus of unbound granular materials. In this study, 19 differently graded unbound granular materials from two countries (USA and Sweden) were evaluated. This study validated both porosity of primary structure (PS) and contact points per particle (coordination number) as key parameters for evaluating the resilient modulus of unbound granular materials. This study showed that decreasing the PS porosity – higher coordination number – calculated based on the proposed gradation model, yields higher resilient modulus. Good correlation was observed between the proposed packing parameters and resilient modulus of several types of aggregates. The packing theory-based framework successfully recognised granular materials that exhibited poor performance in terms of resilient modulus.

Abstract: This paper presents a backcalculation method for pavement layer elastic modulus and thickness The effect of deflection measurement errors on the backcalculated results is also considered The falling weight deflectometer (FWD) data are generated by applying a load to the pavement while calculating deflection at various fixed distances from the load centre The measurement errors in FWD data are simulated by perturbing the theoretical deflections Using these data, a backcalculation technique based on the improved genetic algorithm is proposed In order to deal with the measurement errors, besides the common root mean square, a new objective function called area value with correction factor is introduced to the backcalculation algorithm Numerical examples for two- and four-layer pavement structures are presented, which show the capability of the proposed method in backcalculation of pavement layer modulus and thickness

Abstract: The road surface is one of the most important factors that have influence on the current traffic noise. Usually, for dense surfaces, impacts of the tyre on the pavement generate vibrations which are the dominant mechanisms in the tyre–road noise. In this study, the effect of muffling these vibrations, by the incorporation of crumb rubber (CR) from wasted tyres into asphalt pavements, has been evaluated acoustically. Close proximity measurements have been carried out to register the sound emission generated in the contact zone between a reference tyre and an experimental asphalt pavement with CR. The analysis of the measurements indicates that the incorporation of CR as well as the air voids content has less influence than the macrotexture of the road surface on the acoustical behaviour of this experimental asphalt pavement.

Abstract: It is clear that the purpose of mixture design is to select optimum asphalt content for a desired aggregate structure to meet the prescribed criteria. Aggregate makes up high proportion of volume and mass of mixtures; hence, it is considered as an important constituent of asphalt concrete. This study postulates that the gradation is an important characteristic of the aggregate in adoption of the optimum mixture. One aggregate source, three gradations and different percentages of Sasobit® was used to manufacture hot mix asphalt and warm mix asphalt. The test results indicated that the aggregate gradation affects the rutting resistance and especially the moisture susceptibility of the introduced mixtures, differently. Rutting resistance was evaluated using the flow number parameter, and in order to determine the moisture sensitivity mechanism, a mechanical and visual inspection tests were carried out. At the end, it is concluded that the optimum aggregate gradation for these two types of mixtures is different.

Abstract: This paper presents a laboratory and field study to evaluate the mean profile depth (MPD) parameter that represents the surface texture of chip seal pavements. A three-dimensional laser profiler is used to determine the MPD values from both field pavement sections and field samples that have been tested in the laboratory using the third-scale model mobile loading simulator (MMLS3). Data obtained from five different field-constructed chip seal sections are used to evaluate the effects of different factors on the MPD of chip seal pavements. These factors include aggregate type, emulsion application rate, field versus MMLS3 traffic loading and traffic volume. The results presented in this paper suggest that: (1) chip seal pavements constructed using lightweight aggregate have larger initial MPD values and faster reduction in MPD as a function of the number of wheel passes than those constructed using granite 78M aggregate; (2) MPD values obtained from a drier section (with drier indicating a lower emulsion-t...

Abstract: This study aims to investigate the quality of the recently developed Canadian climatic database and the effect of climatic factors on flexible pavement performance using the mechanistic-empirical pavement design guide (MEPDG). Two hundred and six Canadian climatic files were used to carry out the analysis. Freezing index and frost depth from the MEPDG were compared with the data available in Canadian databases. The sensitivity of pavement performance to climate conditions, predicted using the MEPDG, was also studied. The pavement performance predicted using the virtual weather station and existing weather station data was compared. From the pavement performance sensitivity study, it was found that the asphalt concrete, total pavement rutting and international roughness index show sensitivity to climate changes. It was also found that differences in the quality and duration of data for close-by stations can result in variation in the predicted performance. Overall, the study assists with facilitating the i...

Abstract: In the present study, clay soil collected from new Banda, Uttar Pradesh, India has been treated with rice husk ash (RHA) and Portland slag cement (PSC). Based on unconfined compressive strength test results, the optimum mix obtained is of 82.5%Soil+7.5%PSC+10%RHA. The increase in strength of the optimum mix is about 29.8%, 37.2% and 48.55% for a curing period of 7, 14 and 30 days, respectively. The soaked California bearing ratio (CBR) test gives about 91.75% higher values as compared to unsoaked CBR test for a curing period of 30 days. Strain-controlled cyclic triaxial tests were conducted to study the variation of degradation index, shear modulus and damping ratio of the optimum mix with number of cycles for strain amplitudes of 0.4%, 0.6%, 0.8% and 1% and for frequencies of 0.2 and 1 Hz at an effective confining pressure of 100 kPa. It is observed that the degradation index decreases at a fast rate for the first 25–50 cycles. From the study, it is concluded that the aforementioned mix may be suitable f...

Abstract: This article investigates the strength behaviour of oil-contaminated sand stabilised with cement kiln dust (CKD) in order to assess the engineering properties of the stabilised soil for its application in the construction of rural road. Tests including pH measurement, compaction, unconfined compressive strength (UCS) and California bearing ratio (CBR) were conducted. The investigations were carried out by varying the percentage of CKD, the percentage of oil content, the type of oil, the ageing of stabilised samples and the ambient temperature. Depending on the pH response, the CKD content from 5% to 15% represents a practical limit for cost-effective stabilisation. Results revealed that an increase in the UCS and CBR values of oil-contaminated sand occurred with the addition of CKD. The strength of stabilised contaminated sand decreases as the percentage of oil increases. The addition of 10% CKD to the sand contaminated with 6% oil content is found to give the optimum UCS and CBR values. Furthermore, a se...

Abstract: This study quantifies moisture damage at the asphalt mastic–aggregate interfaces using finite element method modelling technique in ABAQUS. A model aggregate surrounded by a layer of mastic is subjected to static loads of varying magnitudes and patterns. Using dynamic shear and elastic moduli of wet and dry mastic and aggregate as model inputs, moisture-induced damage is quantified through parameters such as contact stresses at interface, load to initiate damage and de-bonding at the interface. Results show that contact stresses are significantly higher in dry samples than wet samples. It is revealed that damage initiates at a smaller magnitude of deformation (0.0508 mm) in the wet sample than that (0.508 mm) in the dry sample. That is, a stiffer dry sample carries more loads and deforms less before damage initiation than a softer wet sample. In addition, approximately 6.8% interface de-bonding occurs in the dry sample, whereas 49.1% de-bonding occurs in the wet sample.

Abstract: Excess water in pavement foundations is one of the major factors contributing to pavements deterioration. In recent years, a number of research studies have been carried out to understand the water movement into pavements and to assess its detrimental effects on the mechanical response of the foundations. However, these studies do not quantify the impact of suction reduction or pore pressure buildup in the foundations on the pavement response. In this paper, coupled finite element analyses are carried out to investigate the effect of the excess water in the granular foundations on the structural performance of flexible pavements. The coupled analyses simulate critical features governing the foundations' hydromechanical response including the transient unsaturated flow and porous nonlinear behaviour of the foundations under moving wheel loads. Furthermore, a parametric study that examines the influences of various loading and foundation parameters on the performance of pavements subjected to excessive mois...

Abstract: Vehicle speed–roughness relationship has a significant research gap in life cycle assessment model. The current available models describing the roughness effect on vehicle speed are very limited and outdated. In this paper, 32 individual pavement sections, each of which has roughness data of up to 8 years, were selected to develop the model. The roughness data cover a wide range, and the selected pavement sections contain both flexible and rigid pavement types and various numbers of lanes. Involved regression variables include the following: vehicle speed, roughness, volume–capacity ratio, pavement type, number of lanes and speed limit. Analysis of variance was first performed, indicating that pavement type and speed limit are not significant factors influencing the average vehicle speed. Following, strict statistical technique was used to correct the unobserved heterogeneity during the regression using a one-way fixed random model. The obtained regression model reveals that the average vehicle speed decr...

Abstract: Qatar National Research Fund (QNRF) through the National Priority Research Program project [NPRP 08-310-2-110].

Abstract: Mixture properties (aggregate gradation and volumetric quantities), rate of loading and environmental conditions are the most important factors that affect the |E*| values. The main objective of this study was to develop a rational approach to investigate and model the effect of air voids and asphalt content on the |E*| master curves and consequently predict pavement performance. In this study, |E*| tests were conducted on three asphalt concrete mixtures with the same aggregate gradation, but different binder grades. For each of these mixtures, the air void and asphalt contents were varied at three levels. It is found that the developed method provides a more accurate estimate of the effects of volumetric changes in hot mix asphalt. The application of the proposed approach would be most beneficial for quality control/quality assurance purposes, performance-related specifications and for estimating contractors' incentives and penalties, where |E*| is utilised to predict the pavement performance.

Abstract: The aggregate gradation is one of the most important parameters in the mechanical properties of hot mix asphalt (HMA). Thus, determining the aggregate gradation is a very significant subject in civil engineering. Usually, to estimate the aggregate gradation, it is required to separate the aggregate from the bitumen, and this operation can be time-consuming and even dangerous related to chemical solvents. Moreover, several computer-based methods have been established to model the internal structure of HMA in two- and three-dimensional methods and can be applied to determine the aggregate gradation, but these methods need special and expensive equipment. Therefore, in this study, a simple approach is introduced to quickly and easily determine the aggregate gradation of HMA from the prepared cross-section images of cylindrical samples using numerical and image-processing techniques such as fitting equation and colour space system. The obtained results indicate that the introduced method can detect the aggreg...

Abstract: This study proposes a spectral approach to the evaluation of variations in dynamic vehicle load on road pavement associated with a vehicle moving at constant speed along a road with a rough surface. The influence of vehicle speed and road roughness on variations in dynamic vehicle load was investigated. The results show that the standard deviation of dynamic vehicle load increases twofold, with a fourfold increase in the road roughness coefficient, and increases approximately linearly with the increase in vehicle speed.

Abstract: Pavement stresses and strain responses due to tyre loading are essential data for design and performance analysis. The magnitude and distribution of these responses are primarily affected by the tyres configuration geometry. This study investigates the longitudinal strain responses at the bottom of a hot-mix asphalt layer for full-depth medium-volume flexible pavement under different truck tyres design. Pavement testing was carried out with a user-control accelerated pavement facility at various speeds and tyre inflation pressures and loading. Three truck tyre configurations: dual-tyre (11R22.5) and two wide-base tyres (425/65R22.5 and 455/55R22.5) widely used in the truck industry were examined. A 3D finite element model was developed to quantify surface stresses to loading at various critical locations in the pavement after being calibrated with the field-measured strains. Field measurements showed that the 455 wide-base tyres yield 7% more longitudinal strain than a dual-tyre assembly at the same tyre ...

Abstract: Deterioration of track causes variations in different mechanical parameters such as value and distribution of track vertical stiffness, which would change the way track mechanical components behave in service condition or maintenance operations As a result, studying deterioration effects and that of maintenance operations such as tamping and dynamic stabilisation on the mechanical behaviour of both standard and deteriorated tracks could give a better picture of track condition and effectiveness of maintenance operations In this paper, by carrying out static and dynamic tests and using 89 measurement sensors, the influence of mechanised maintenance operations on mechanical behaviours (strain, acceleration and displacement of rail and sleeper) of a high-deteriorated track and a low-deteriorated track is investigated The tests were carried out in three different stages (before tamping, after tamping and after track dynamic stabilisation) under a passing train (a 6-axle locomotive and a 4-axle wagon) with

Abstract: The mixing temperature for binders is normally chosen by the pavement engineer based on a specific ‘viscosity’ required during hot mix asphalt production. Majority of the unmodified binders exhibit Newtonian behaviour at the mixing temperature and hence the determination of the same is straight-forward. However, when modified binders are used, experiments using a rotational viscometer indicate that the binder exhibits viscoelastic non-Newtonian fluid characteristic even at very high temperature. Consequently, the ‘viscosity’ varies with time and the location where it is measured, and hence is not a unique property of the material. In this work, a thermodynamically consistent, frame-invariant viscoelastic non-Newtonian fluid model was developed to characterise the rheological properties of the binders tested in a rotational viscometer. In the investigation reported here, two types of modified binders, polymer and crumb rubber, and one unmodified binder were used. These binders were subjected to steady and ...