Showing papers in "International Journal of Pavement Engineering in 2009"
TL;DR: In this paper, the effects of moisture damage for rubberised asphalt concrete (RAC) mixtures containing RAP were investigated, and the results indicated that the additional of RAP was beneficial in improving the indirect tensile strength (ITS) values and reducing the moisture susceptibility of the mixture.
Abstract: In many parts of the world, highway officials are utilising crumb rubber and reclaimed asphalt pavement (RAP) in order to save money, protect the environment, and improve the life of asphalt pavement However, due to the use of these materials, the effects of moisture damage should be investigated for rubberised asphalt concrete (RAC) mixtures containing RAP The objective of this research involved investigating the moisture susceptibility of RAC containing RAP The testing conducted included the determination of binder viscosity, toughness and indirect tensile strength (ITS) analysis Several mixtures containing different crumb rubber types, two different RAP sources and various percentages of rubber and RAP were evaluated The results indicated that, in general, the additional of RAP was beneficial in improving the ITS values and reducing the moisture susceptibility of the mixture although the addition of crumb rubber had a slightly negative effect
102 citations
TL;DR: In this article, the performance of 20 pavement contracts in eastern and northeastern Ontario, Canada was investigated using an extended bending beam rheometer protocol, which revealed that the long-life pavements were made with materials that suffered little from reversible ageing mechanisms during cold conditioning.
Abstract: This paper documents an investigation of the performance of 20 pavement contracts in eastern and northeastern Ontario, Canada. Eleven of these pavements showed little or no distress after 7–15 years in service. The remaining nine, aged between 7 and 13 years, all cracked prematurely and excessively. Creep testing of the recovered asphalt cements, according to an extended bending beam rheometer protocol, revealed that the long-life pavements were made with materials that suffered little from reversible ageing mechanisms during cold conditioning. Ductile failure testing in a double-edge notched tension test at 15°C revealed equally significant differentiation, with the superior performing materials possessing considerably higher strain tolerances. The newly developed methods were able to explain vast performance differences with 95% accuracy. This study further validates Ontario's interest in an improved asphalt cement grading approach and provides evidence that thin pavements can have long lives, provided ...
102 citations
TL;DR: In this paper, a rubber-modified hot-mix asphalt (RMHMA) was used for traffic pavements fabricated by dry process, where fine granulated crumbed rubber from discarded tyres was mixed with heat aggregates and after a short delay time, an ordinary bitumen binder was added to the mixture in the plug mill.
Abstract: This paper focuses on tyre rubber-modified hot-mix asphalt for traffic pavements fabricated by dry process. Fine granulated crumbed rubber from discarded tyres was mixed with heat aggregates and after a short delay time, an ordinary bitumen binder was added to the mixture in the plug mill. The research was partially carried out in the laboratory (designing the optimum mixture composition) and on site, constructing an experimental road segment, 2.5 km length, in a secondary traffic road located between Salamanca and Ciudad Rodrigo (Spain). The rubber-modified hot-mix asphalt (RMHMA) was placed on site and compacted after a controlled time of maturation (ageing) of the warm rubber-modified hot-mix asphalt, which promotes a close interaction between the rubber particles and the binder.
75 citations
TL;DR: In this article, the Huet-Sayegh model was used to describe the complex modulus and characterise the linear viscoelastic property of asphalt concrete, and the results indicated that the Huat-Sayeh model can describe complex moduli more accurately using fewer numbers of parameters compared with other mechanical models.
Abstract: In order to seek an appropriate mechanical model to describe the complex modulus and characterise the linear viscoelastic property of asphalt concrete, the Huet–Sayegh model was studied in this research. Laboratory tests of complex modulus were conducted on 20 different mixtures. Several mechanical models (Maxwell, Kelvin, generalised Maxwell, generalised Kelvin and Huet–Sayegh) and the mathematical model of sigmoidal function were applied to establish master curves of dynamic moduli. Results indicate that the Huet–Sayegh model can describe complex modulus more accurately using fewer numbers of parameters compared with other mechanical models.
74 citations
TL;DR: In this paper, the authors re-examine the asphalt-rubber interaction mechanism and focus on controlling the swelling of crumb rubber particles through varying the interaction conditions, such as time, temperature, shearing speed and the addition of polymer modifiers to enhance the binder performance properties.
Abstract: Traditional crumb rubber-modified (CRM) binders produced with coarse particles according to the McDonald method, the wet process, raise engineering as well as environmental concerns for their suitability in Superpave applications. This paper investigates the possibility of producing high-performance terminal blending CRM binders suitable for Superpave applications through the wet process. This paper re-examines the asphalt–rubber interaction mechanism and focuses on controlling the swelling of crumb rubber particles through varying the interaction conditions. This study considers parameters such as time, temperature, shearing speed and the addition of polymer modifiers to enhance the binder performance properties to meet the requirements of Superpave mixes. Rubber-modified terminal blends are very different from the McDonald-type binders and so are the conditions required for each binder type. The binder properties of interest are those related to performance and compatibility.
73 citations
TL;DR: In this article, the contributions of aggregate structure and asphalt binder to the rutting characteristics of a dense-graded surface HMA mixture were identified, and three different asphalt binders (PG 64-22, PG 76-22 and PG 82-22) were used to make mixtures for laboratory rut evaluations.
Abstract: Rutting has been identified as one of the primary distresses in asphalt pavements. Rutting in hot-mix asphalt (HMA) mixtures can be attributed to either the lack of interlocking of aggregate structure or insufficient bonding between aggregate and asphalt binder, or both. In the present study, efforts have been made to identify the contributions of aggregate structure and asphalt binder to the rutting characteristics of a dense-graded surface HMA mixture. Coarse gravels at five different angularity levels (100, 85, 70, 50 and 35% of aggregate with two or more fractured surfaces) were used to produce mixtures with similar aggregate gradations. Three different asphalt binders (PG 64-22, PG 76-22 and PG 82-22) were used to make mixtures for laboratory rut evaluations. The aggregate imaging system (AIMS), uncompacted voids in coarse aggregate (VCA) and tri-axial shear tests were conducted to evaluate the coarse aggregate angularity (CAA). The US Army Corps of Engineers' gyratory testing machine (GTM), creep an...
63 citations
TL;DR: In this article, the aging characteristics of warm-mix asphalt (WMA) binders were evaluated in the rolling thin film oven (RTFO) and the pressure aging vessel.
Abstract: As warm asphalt has been gaining increasing popularity in recent years, there are still several characteristics of warm asphalt, which are unknown. While several studies have been conducted to analyse the performance of warm asphalt mixtures, aging characteristics of warm-mix asphalt (WMA) binders are not known in great detail. This paper presents the results of a study to evaluate the aging characteristics of WMA binders artificially aged in the rolling thin film oven (RTFO) and the pressure aging vessel. RTFO aging was performed at 163°C and a lower temperature to simulate warm asphalt aging. The results of this study indicated that reducing the aging temperature reduced the aging index and increased the m-values, but had no significant effects on G*/sin δ, G*sin δ and stiffness of the binders. Also, the addition of warm asphalt additives significantly increased the G*/sin δ values and lowered the m-values of the binders.
52 citations
TL;DR: In this article, the authors investigate laboratory performance of crumb rubber concrete block pavement (CBP) and find that CBP exhibits inferior performance than the conventional CBP in rut, deformation, skid resistance and shear resistance but showed a great improvement in toughness.
Abstract: The aim of this study was to investigate laboratory performance of crumb rubber concrete block pavement (CBP). Four different paving blocks containing 0 (control), 10, 20 and 30% rubber by total sand volume with compressive strength ranging between 23 and 64 MPa were used. The test pavement was subjected to 10,000 cycles of load repetition under a single truck wheel via a tyre inflated to 600 kPa. Nine measurements of pavement deformation and joint width were made at various stages of trafficking. Additional tests, including pull-out, skid resistances and falling weight test, were then carried out. Overall, crumb rubber CBP is observed to show inferior performance than the conventional CBP in rut, deformation, skid resistance and shear resistance but showed a great improvement in toughness. Thus, all paving blocks studied in this project have a great potential to be used according to traffic volume and types of applications.
51 citations
TL;DR: In this paper, a study of the effects of moisture ingress on the mechanical properties of a cold-laid grave emulsion asphalt mixture was presented, where a vacuum moisture saturation technique was developed to induce different moisture levels in laboratory-prepared specimens, which simulate site conditions deduced from a field trial.
Abstract: This paper presents a study of the effects of moisture ingress on the mechanical properties of a cold-laid grave emulsion asphalt mixture. A vacuum moisture saturation technique has been developed to induce different moisture levels in laboratory-prepared specimens, which simulate site conditions deduced from a field trial. For comparison purposes, a hot mix with the same aggregates and base binder was also used in the study. The stiffness of both materials was monitored under different curing conditions for an extended duration. Semi-circular specimens loaded in a three-point bending test were used to determine fracture properties: fracture toughness and fracture energy. Results showed that, although the hot mixture had good fracture properties, the cold mixture's results were only marginally lower. The vacuum saturation treatment led to enhanced yield performance at low temperatures of both mixtures in the fracture test. The high level of moisture treatment given to the cold mixture made it behave like ...
49 citations
TL;DR: In this article, an experimental protocol was developed for determining the moisture diffusion coefficient of asphalt mixtures based on measuring suction over time in test specimens using thermocouple psychrometers.
Abstract: The presence of moisture in asphalt pavements detrimentally affects the bond between the aggregate and binder and the bond within the binder. The loss of these bonds leads to the deterioration of asphalt pavements. In regions with low rainfall, moisture diffusion is an important source of moisture transport in asphalt mixtures. The diffusion coefficient is a necessary input for models simulating moisture transport and, consequently, moisture damage in asphalt pavements. In this study, an experimental protocol was developed for determining the moisture diffusion coefficient of asphalt mixtures. The experimental set-up relies on measuring suction over time in test specimens using thermocouple psychrometers. The proposed protocol successfully determined a wide range of diffusion coefficients (i.e. from 5.67 × 10− 5 to 2.92 × 10− 6 cm2/s) of different asphalt mixtures. X-ray computed tomography was used to characterise the air void structure of test specimens. The results revealed good correlation between the...
49 citations
TL;DR: In this article, an approach related to the development of a new hot mix asphalt (HMA) dynamic modulus (|E *|) prediction model by employing the artificial neural networks (ANNs) methodology was described.
Abstract: This paper describes an innovative approach related to the development of a new hot mix asphalt (HMA) dynamic modulus (|E *|) prediction model by employing the artificial neural networks (ANNs) methodology. Many studies have been conducted over the last 50 years related to the development of HMA |E *| prediction models based on the regression analysis of laboratory measurements. The current study is an attempt to replace the regression analysis with the ANNs that have proved useful for solving certain types of problems that are too complex, poorly understood or resource intensive to tackle using more traditional numerical and statistical methods. The ANN |E *| prediction models were developed using the latest comprehensive |E *| database that is available to the researchers (from the NCHRP Report 547) containing 7400 data points from 346 HMA mixtures. The ANN model predictions were compared with the 1999 version of the Witczak |E *| prediction model, which is included in the mechanistic–empirical pavement...
TL;DR: In this article, the results of implement laboratory testing were carried out to assess the mechanical characteristics of hydrated cement treated crushed rock base (HCTCRB), which is widely used as a base course material for Western Australian roads.
Abstract: Hydrated cement treated crushed rock base (HCTCRB) is widely used as a base course material for Western Australian roads. In order to be able to use this material effectively, its shear strength, resilient modulus and permanent deformation characteristics should be investigated and clearly understood. This study aimed to carry out the results of implement laboratory testing, which was to assess the mechanical characteristics of HCTCRB. Our findings show that HCTCRB can be characterised as the cohesive granular material that has a cohesion (c) of 177 kPa and an internal friction angle (φ) of 42°. The resilient modulus characteristics can be modelled using the Uzan model. The permanent deformation characteristics can be modelled using the Sweere, G.T.H.'s model. These models are based on the test results following the Austroads – APRG 00/33 test standard.
TL;DR: In this article, the use of portable falling weight deflectometers (PFWDs) has gained popularity in recent years, mainly because of the inherent capability of PFWDs in obtaining quick estimates of the modulus of subgrade in addition to their simplicity in design and portability.
Abstract: The evaluation of subgrade strength plays a major role in pavement design. An understanding of subgrade properties enables the selection of road materials for sub-base and base courses. In developing countries like India, apart from the use of well-established traditional pavement evaluation techniques such as the California bearing ratio (CBR) test and the dynamic cone penetrometer (DCP) test, the use of non-destructive testing devices such as the portable falling weight deflectometers (PFWDs) has gained popularity in recent years. This is mainly because of the inherent capability of PFWDs in obtaining quick estimates of the modulus of subgrade in addition to their simplicity in design and portability. Thus, there exists a need to correlate the results obtained using PFWDs with those obtained using traditional approaches such as the CBR and the DCP for the benefit of road engineers. This work focuses on exploring the correlations between these approaches for lateritic soils in Dakshina Kannada district, ...
TL;DR: In this paper, an investigation into the time-temperature superposition principle as it relates to ductile failure in asphalt is presented. But, the authors suggest that this substitution is not generally accurate.
Abstract: This paper documents and discusses an investigation into the time–temperature superposition principle as it relates to ductile failure in asphalt. Seven binders of approximately the same low and intermediate temperature and varying high temperature Superpave® grades were tested in a dynamic shear rheometer (DSR) and double-edge-notched tension test to determine their rheological and failure energy master curves. Master curves typically permit the prediction of rheological properties at very long or short timescales from measurements at higher or lower test temperatures over more accessible testing timescales. It has been suggested in the Strategic Highway Research Program final report A-369 that rheological shift factors obtained from a DSR experiment can be used to predict failure master curves from experimentally accessible data at various temperatures. The findings of this study suggest that this substitution is not generally accurate. For straight asphalt binders the difference can be relatively small...
TL;DR: In this paper, an improved solution algorithm based on the finite-element method to analyse rigid pavements under moving vehicular or aircraft loads is presented, where the concrete pavement is discretised by thick plate elements that account for the transverse shear deformation and bending.
Abstract: Study of the dynamic response of pavements due to moving loads such as vehicles and aircraft has received significant attention in recent years because of its relevance to the design of pavements and airport runways. This paper presents an improved solution algorithm based on the finite-element method to analyse rigid pavements under moving vehicular or aircraft loads. The concrete pavement is discretised by thick plate elements that account for the transverse shear deformation and bending. The underlying soil medium is modelled by elastic spring and dashpot systems. The dynamic interaction between the moving load and the pavement is considered by modelling the vehicle by spring–dashpot unit. Graphical results are presented to demonstrate the significance of the dynamic interaction between the pavement and the vehicle on pavement response. Results indicated that slab thickness, soil modulus and velocity of aircraft had a significant effect on the response of the pavement.
TL;DR: In this paper, the surface areas of CRM were measured using the Brunauer, Emmett and Teller (BET) tester and 108 CRM binders were tested for their viscosity at 135°C.
Abstract: In general, crumb rubber modifier-modified binders (CRM binders) have better performance properties than base binders and thus, are becoming more widely used in pavements in a few states. However, the mechanism by which the interaction between the asphalt base binder and the CRM blends added takes place has not been fully characterised. In this study, the surface areas of CRM were at first measured using the Brunauer, Emmett and Teller (BET) tester. Second, 108 CRM binders were produced using different combinations of CRM blend variables and mixing conditions and consequently tested for their viscosity at 135°C. The influence of the surface area and the average size of the CRM blends on the viscosity of the CRM binders was statistically investigated. Results from this study indicated that: (1) the surface area of the ambient CRM is almost twice as large as that of the cryogenic CRM, leading to an increase in the viscosity up to 16–58% over cryogenic CRM binders and (2) the viscosity of the CRM binders has...
TL;DR: In this article, a PG 64-22 binder was modified with four different crumb rubber sources at concentration of 15% by weight of binder by using hot water activation.
Abstract: Hot water activation of crumb rubber has been suggested as a method of improving compatibility between crumb rubber and asphalt binder This procedure removes light oil fractions present in the crumb rubber particles, thus decreasing segregation occurring between rubber particles and binder For this research, a PG 64-22 binder was modified with four different crumb rubber sources at concentration of 15% by weight of binder Binder properties were evaluated for virgin binders, water-activated crumb rubber-modified (CRM) binders, and for non-activated CRM binders CRM surface morphologies were studied using a scanning electron microscope, molecular size distributions of modified binders were determined using gel permeation chromatography, while storage stability was evaluated by cigar tube testing Rheological properties of the CRM binder were investigated; improved phase separation properties were observed following water activation, however, these improvements did not result in improved rheological prope
TL;DR: In this article, a mechanistic-empirical model for geosynthetic base-reinforced flexible pavements is proposed, which uses traditional components of an existing unreinforced mechanistic empirical model developed in the USA through NCHRP Project 1-37A, including finite element response model, material models for the asphalt concrete, unbound aggregate base and subgrade and damage models for asphalt concrete fatigue cracking and permanent deformation in the pavement cross-section layers.
Abstract: A mechanistic–empirical model for geosynthetic base-reinforced flexible pavements is proposed. The model uses traditional components of an existing unreinforced mechanistic–empirical model developed in the USA through NCHRP Project 1-37A. These components include a finite element response model, material models for the asphalt concrete, unbound aggregate base and subgrade and damage models for asphalt concrete fatigue cracking and permanent deformation in the pavement cross-section layers. New components for the reinforcement are introduced and include structural elements for the reinforcement, a material model for the reinforcement, a model for reinforcement–aggregate shear interaction, additional response modelling steps that account for the influence of the reinforcement on lateral confinement of the base aggregate during construction and subsequent traffic loading, and a modified permanent deformation damage model used for aggregate within the influence zone of the reinforcement. This paper describes ...
TL;DR: In this article, a maintenance decision model for flexible pavements using data extracted from the long-term pavement performance-DataPave3.0 programme was developed through research conducted at Cairo University, Egypt.
Abstract: Selection of an appropriate pavement maintenance and rehabilitation (M&R) treatment is often a complex process. Some researchers have suggested a ‘decision tree’ approach to select the most feasible repair strategy based on the existing pavement condition. A decision system, maintenance unit (MU), was developed through research conducted at Cairo University, Egypt. The MU system determines M&R activities based on the density of distress repair methods (not the density of individual distresses). In addition, it addresses the complex combinations between distress levels and maintenance alternatives. Identifying future maintenance needs is an important component for a multi-year analysis. The objective of this study is to develop a maintenance decision model for flexible pavements using data extracted from the long-term pavement performance-DataPave3.0 programme. The proposed model, predicts future MU values with which future maintenance needs are determined. The validation process was performed using differ...
TL;DR: In this article, the authors applied a series of discrete test and analysis methods as an integrated approach for the estimation of time and position-dependent humidity changes and shrinkage in early-age concrete.
Abstract: This paper describes the effort placed to apply a series of discrete test and analysis methods as an integrated approach for the estimation of time- and position-dependent humidity changes and shrinkage in early-age concrete. The total moisture loss in concrete is assumed to be a result of autogenous drying and conventional external drying. Autogenous drying or self-desiccation is expressed as a function of the degree of hydration in terms of strength ratio, which can be determined by the maturity and strength relationship. Moisture loss due to external drying is estimated by finite element analysis based on the nonlinear diffusion theory. Estimated humidity reduction is then used to estimate shrinkage potential in the concrete by applying a linear shrinkage coefficient, which may be determined by tests. Time- and position-dependent shrinkage potential will be useful for further stress analysis. Application of the analysis approach is introduced with an example analysis for a 300 mm × 300 mm cylinder spec...
TL;DR: In this paper, the effects of hot mix asphalt (HMA) surface layer thickness, base type, base thickness and drainage on the performance of new flexible pavements constructed in different site conditions (subgrade type and climate).
Abstract: This paper presents the results of a study on the relative influence of design features and site factors on the fatigue performance of in-service flexible pavements. The data used in this study were from the SPS-1 experiment of the long-term performance pavement (LTPP) programme. This experiment was designed to investigate the effects of hot mix asphalt (HMA) surface layer thickness, base type, base thickness and drainage on the performance of new flexible pavements constructed in different site conditions (subgrade type and climate). Various statistical analyses (ANOVA, logistic regression, discriminant analysis) were adopted for data analyses. Among the design factors, base type was found to be the most critical factor affecting fatigue cracking. The best performance was shown by pavement sections with asphalt treated base (ATB). This effect should be interpreted in light of the fact that an ATB effectively means a thicker HMA layer. The combination of drainage and base type also played an important rol...
TL;DR: In this paper, the effects of dowel misalignment on the joint opening behavior and associated distresses in concrete pavement joints were evaluated and the results included pull-out force-joint opening responses and the observations of damage (spalling, cracking, etc.).
Abstract: Experimental and analytical investigations were conducted to evaluate the effects of dowel misalignment on the joint opening behaviour and associated distresses in concrete pavement joints. The experimental investigations focused on pavement specimens with one or two misaligned dowel bars at the joints, and the results included the pull-out force-joint opening responses and the observations of damage (spalling, cracking, etc.). Numerical models of the pavement specimens were developed to gain additional insight into the behaviour, 3D stresses and strains, and localised damage associated with the misaligned dowel bars. These models accounted for (a) concrete inelasticity in compression and cracking in tension and (b) the longitudinal bond and the transverse interaction between the dowel and the concrete pavement. The models were verified using experimental results and used to identify the occurrence of various material damage limit states (debonding, concrete cracking, etc.) on the joint opening behaviour....
TL;DR: In this article, the authors presented an adaptation of these methods, for Israeli traffic and environmental conditions, calculating the total perpetual pavement thickness using the Israeli design method, which can handle a wide variety of load levels, and determined the minimum thickness at which the tensile strain at the bottom of the asphalt layer meets one of the following two criteria: (1) crack initiation at the end of the 30 years design period or (2) an ‘endurance limit of 70μS).
Abstract: A perpetual flexible pavement is defined as hot mix asphalt (HMA) pavement, designed and built to last longer than 50 years without requiring major structural rehabilitation or reconstruction. It may only need periodic surface renewal when the distresses have reached unacceptable levels. The design methods currently used in the USA and other countries are not adequate for the traffic and climatic conditions in Israel. An adaptation of these methods, for Israeli traffic and environmental conditions is presented. The total perpetual pavement thickness is calculating using the Israeli design method, which can handle a wide variety of load levels. The HMA layers thickness is determined as the minimum thickness at which the tensile strain at the bottom of the HMA layer meets one of the following two criteria: (1) crack initiation at the end of the 30 years design period or (2) an ‘endurance’ limit of 70 μS. The strain is computed for a single axle load of 130 kN, effective temperature corresponding to Israeli ...
TL;DR: In this article, it is suggested that restrained expansion and contraction during alternations in heating and cooling often result in forms of cracking which are not fully recovered at the end of each thermal cycle.
Abstract: Although recognised as contributing to certain forms of crack development in asphalt, thermal effects are rarely seen as the primary cause of perhaps the most prevalent forms of crack pattern. This technical note will argue that far from just contributing, thermal effects might often provide the initiating and propagation mechanism for the evolution of many classes of crack pattern. It will suggest that restrained expansion and contraction during alternations in heating and cooling often result in forms of cracking which are not fully recovered at the end of each thermal cycle. It is argued that this could provide an alternative explanation for certain forms of top-down cracking and especially those referred to as ‘alligator cracking’. It is further suggested that greater recognition of the thermo-mechanical processes, thought to be responsible for various types of pavement cracking, might have important implications for improving future pavement design and maintenance strategies.
TL;DR: In this paper, a parametric experimental study has been conducted to investigate the effect of polypropylene fiber on the mechanical and shrinkage properties of cement-stabilised macadam.
Abstract: A parametric experimental study has been conducted to investigate the effect of polypropylene fibre on the mechanical (compressive strength, splitting tensile strength, compressive modulus of resilience, flexural strength, flexural modulus of elasticity) and shrinkage properties (dry and thermal shrinkage coefficients) of cement-stabilised macadam. Four different fibre volume fractions were used: 0.04, 0.06, 0.08 and 0.1%. Tests without mixing fibres were also carried out. The results indicate that the mechanical and shrinkage properties of cement-stabilised macadam can be improved by mixing polypropylene fibre with it. Polypropylene fibre distinctly reinforces the strength of cement-stabilised macadam; however, it can effectively decrease the compressive modulus of resilience, flexural modulus of elasticity and shrinkage coefficients of cement-stabilised macadam. As a result, it increases the resistance to deformation of cement-stabilised macadam. When the fibre volume fraction is not beyond 0.1%, there ...
TL;DR: In this article, the effect of skewing the transverse joints in concrete rigid pavements is studied through 3D finite element modeling, and it is shown that skewing joints did not reduce the level of stresses and strains in critical locations in the concrete slab.
Abstract: The effect of skewing the transverse joints in concrete rigid pavements is studied through 3D finite element modelling. Models of multi-layered systems consisting of Portland cement concrete slabs, base and subgrade were developed. These consisted of slabs having straight as well as skewed joints. In order to study the state of stresses and strains in both straight and skewed slabs, the models were subjected to moving axle loads as well as non-linear temperature gradients. More refined models were developed and subjected to falling weight deflectometer dynamic loads to study the state of stresses at the dowels–concrete interfaces. The study, shows that skewing the joints did not reduce the level of stresses and strains in critical locations in the concrete slab. Also a close study of the induced stresses and strains showed that fatigue relations adapted for concrete pavements needed to be refined. The distribution of stresses around the dowel sockets indicates the formation of a tensile stress component, ...
TL;DR: In this paper, a pavement management model is developed using a microscopic approach to yield optimum pavement conditions for a given pavement system, which is formulated as a constrained integer linear programming model subjected to budget and improvement requirement constraints.
Abstract: A pavement management model has been developed using a microscopic approach to yield optimum pavement conditions for a given pavement system. The microscopic pavement management problem is formulated as a constrained integer linear programming model subjected to budget and improvement requirement constraints. The developed optimum microscopic model incorporates integer variables representing the number of pavement sections to be treated by the applicable maintenance and rehabilitation actions. The objective of yielding optimum pavement conditions is achieved by either considering the net pavement condition rating gain or age – gain applied to a given pavement system. In either approach, the optimisation model can be formulated to maximise pavement conditions or minimise maintenance and rehabilitation costs. Data requirements for the microscopic model include identification of each pavement section and rating its distress condition, providing cost rates and performance parameters for the deployed maintenance and rehabilitation actions and specifying anticipated budget and pavement improvement requirements. Sample results from a case study have indicated that the developed model is very effective in yielding optimum pavement conditions.
TL;DR: In this article, an anisotropic model is used to describe the nonlinear behavior of sand-asphalt mixtures, which allows for the material to have multiple natural configurations corresponding to its underlying structure.
Abstract: Sand–asphalt mixtures are difficult to model, partly due to their composition and partly due to the complex interplay among their constituents. This work is concerned with the development of an anisotropic model to describe the nonlinear behaviour of sand–asphalt mixtures. A general thermodynamic framework is used, which allows for the material to have multiple natural configurations corresponding to its underlying structure. The evolution of the natural configuration takes place in a thermodynamically consistent manner. The model developed is corroborated using experimental results published by Ravindran et al. (2007a,b) on torsion tests of sand–asphalt specimens over a range of conditions.
TL;DR: In this article, an alternative method to that of the mechanistic-empirical pavement design guide (MEPDG) is proposed for determining the appropriate representative elastic modulus of asphalt concrete.
Abstract: The National Cooperative Highway Research Program (NCHRP) 1-37A mechanistic-empirical pavement design guide (MEPDG) utilises the dynamic modulus of asphalt concrete in a multilayered elastic analysis to determine the primary responses in asphalt pavements. The dynamic modulus depends on temperature and loading frequency. In the MEPDG, the pulse time is used to determine the loading frequency. This methodology has been under scrutiny due to the large modulus it estimates. This paper evaluates several approximation methods, including the current MEPDG analysis, for the calculation of stresses and strains in linear viscoelastic materials by comparing analysis results with the solutions from the exact linear viscoelastic analysis. Sources of the errors that result from various approximation methods are discussed. Also, an alternative method to that of the MEPDG is proposed for determining the appropriate representative elastic modulus of asphalt concrete.
TL;DR: In this article, the authors evaluated the surface roughness of pavement sections rehabilitated using the crack, seat and overlay (CS&O) technique and developed prediction models for pavement sections in California.
Abstract: Crack, seat and overlay (CS&O) is a rehabilitation technique that has been used on jointed plain concrete pavements. Only a few studies have evaluated the surface roughness of pavement sections rehabilitated using this technique. The purpose of this paper was to evaluate the roughness of roadway sections rehabilitated employing the CS&O technique. The data extracted from the long-term pavement performance database were separated based on the weather region and analysed. Then, international roughness index (IRI) prediction models were developed. A separate model was developed for pavement sections in California. For sections with bound bases, thick overlays provide a smoother surface (lower IRI). However, the effect of the overlay thickness on the IRI for sections with unbound bases does not appear to be considerable. Prediction models developed in this study are shown to provide adequate predictive capabilities. Sections in California have initial IRI values that are lower than those found for sections in...