Behavior Of Pavement Materials Research Articles

Predicting resilient modulus for pavement design: a comprehensive review of artificial neural network applications

ABSTRACT The Resilient Modulus (M R) is an essential parameter describing the mechanical behaviour of pavement materials, but the tests to obtain it are time-consuming and costly. Therefore, machine learning, especially Artificial Neural Networks (ANN), has recently been an effective alternative for predicting M R. Although there has been an increase in articles on ANN for predicting M R, no systematic review has yet categorised the publications, algorithm structures, predictive parameters, and model accuracy. This review provides a comprehensive overview of studies using ANN to predict M R for pavement materials. It examines various ANN subtypes and model structures, addressing a gap in understanding these models and identifying prevalent predictive parameters. Twenty-five peer-reviewed articles published in English-language journals were identified using keywords related to neural networks and M R. For fine soils, all models reviewed use moisture content as a predictive parameter. In contrast, granular soils models typically include stress state and physical characteristics of the materials. For recycled or stabilised materials, there is significant variability in model inputs. This review underscores the potential of ANN in enhancing predictive models for M R in pavement engineering, pointing towards future research and application refinement in this area of study.

Modelling the response of large-size subbase materials tested under varying moisture conditions in a heavy vehicle simulator

Pavement design methods must be able to predict the behaviour of pavement materials at increased moisture levels due to climate changes causing increased precipitation and more intense rainfall events. This paper intends to examine the influence of moisture and gradation on pavement response. An instrumented accelerated pavement test (APT) has been conducted on two thin flexible pavement structures with unbound base course and subbase materials using a heavy vehicle simulator (HVS). The two pavement structures were identical except for the gradation of the subbase material, where one had a 0/90 mm curve with a controlled fines content, and the other had an open-graded 22/90 mm curve. The APT was conducted using constant dual-wheel loading, and three different groundwater (GW) levels were induced in order to change the moisture content in the structures. The HVS was stopped regularly for carrying out response measurements from the instrumentation. The analysis is focussed on the response of the unbound aggregate layers to varying moisture levels in the pavement structure. The increased GW level causes a substantial increase in rutting. Conflicting results are found regarding the development of stresses and strains throughout the APT. Two models, linear elastic and non-linear elastic, is employed to model the responses from the pavement structures.

Permanent deformation modelling of large-size unbound pavement materials tested in a heavy vehicle simulator under different moisture conditions

ABSTRACT Climate changes alter the environmental conditions which pavement design is based on, invalidating empirical design methods. Transition to mechanistic design requires the ability to model the behaviour of pavement materials under relevant environmental conditions. An accelerated pavement test (APT) is designed to test two instrumented pavement structures under moisture conditions which are altered by raising the groundwater table (GWT). Open-graded and well-graded subbase materials are used to investigate the effect of gradation on moisture dependency. Pavement response behaviour is modelled using a non-linear elastic (NLE) approach. Accumulation of permanent deformation under different moisture conditions is calculated by two models and compared to measured surface rutting. Moisture transport through the structures differs due to the subbase gradation. Increased GWT accelerates the accumulation of permanent deformations in both structures, identified by both models. One model provides a significantly better fit to the subgrade deformations and the width of the rutting profile.

Development of cohesive-zone-based prediction model for reflective cracking in asphalt overlay

ABSTRACT Reflective crack has been a major problem of asphalt overlay on existing concrete pavements. Joint or crack movements of concrete slab induce the concentrated stress in asphalt layer; thus producing this distress. Rainwater can then infiltrate into subgrade through this crack opening and the loss support is expected. In addition, the cohesive zone model has been steadily utilised to investigate the fracture behaviour of pavement materials. This method can characterise the crack propagation to the real-life phenomenon. Further, current prediction models of reflective crack have adopted the concept of uniform crack propagation to simplify their analysis. This assumption may misinterpret the crack estimation since nonuniformly propagation occurs over the cross-sectional area of asphalt overlay. Therefore, this study aimed to develop a cohesive-zone-based prediction model that can reasonably compute the amount of reflective cracks with the consideration of nonuniform crack propagation. Available data from LTPP database were also collected for reflective crack modelling and calibration. In addition, traffic- and thermal-induced reflective crack was evaluated by 3D finite element method and cohesive zone model. The mechanistic results were afterward correlated with measured the amount of reflective crack to form the prediction formulation. This model consequently generated the acceptable results with measured reflective crack.

Effect of Asphalt Mixture Components on the Uncertainty in Dynamic Modulus Mastercurves

Practitioners and researchers in the paving industry have highlighted the importance of the adoption of reliability-based pavement design. The goal of developing reliable pavements with optimum performance over their design life has become a key factor to be considered during both pavement design and construction processes. This requires the adoption of statistical and probabilistic-based analyses for the formulation of the properties and behavior of pavement materials. Thus, many researchers worked on the quantification and modeling of the uncertainty caused by the inherent variability in pavement materials in general and that of asphalt concrete (AC) in particular. The dynamic modulus (| E*|), a fundamental property for mechanistic-empirical and purely mechanistic pavement designs, has been proven to have a significant level of uncertainty that is dependent on climatic and traffic loading conditions. The main objective of this study is to investigate the effect of the AC mixture properties and components on the uncertainty in the | E*| mastercurve. This objective is achieved by conducting an experimental program incorporating four different mixtures having the same material sources but different binder types and gradations. Monte Carlo simulations are used to model the uncertainty of | E*| for each of these mixtures. The paper shows that the uncertainty is dependent on mixture type, as the presence of larger nominal maximum aggregate size, modified binder, or additive can increase the uncertainty in the | E*| mastercurve, especially at high temperatures or slow loading rates. The uncertainty is proven to be material related and not imposed by the testing instrumentation.

Assessment of the Deterioration Model for Asphalt Concrete Pavement

Rutting is one type of major distress, it exhibits a negative impact to the serviceability characteristics of the flexible pavement, to the residual life of pavement structure and to the safety and ride quality for traffic. Monitoring the accumulation of pavement distress is beneficial in obtaining the deterioration model which can be implemented in the decision of maintenance. Moreover, such model can focus on the properties of materials with sustainable behavior. Simple empirical relationship between the elastic strain and the long-term plastic behavior of pavement materials was established. The aim of this work is to study the in-service behavior of pavement material and relates the pavement layers composition to pavement age. The -expired life since construction- of Asphalt concrete pavement of Mosul-Baji highway was related to gradation variables, Asphalt and voids content and structural properties variables (Marshall properties, and Stiffness). An Asphalt Concrete deterioration model was developed by combining the data from laboratory testing on core and slab specimens obtained from the various layers of the pavement and performing a regression analysis. The model describes the structural deterioration of Asphalt Concrete pavement. It was concluded that such modeling may give a correct basis for treatment planning, project evaluation, management and funding.

Reliability study on fracture and fatigue behavior of pavement materials using SCB specimen

ABSTRACT Reliability of semi-circular bending (SCB) specimen for measuring the fracture behaviour of pavement materials under static and cyclic loadings has been examined. This study is divided into three phases. In the first phase a comparison between different equations suggested by several specifications and by researchers has been made. Three different SCB specimen types used for predicting mixed mode fracture behaviour of pavement materials have been evaluated in the second phase. In the third phase the applicability of using SCB specimen in predicting fatigue crack growth rate in pavement materials under mode I has been examined. 3-D finite element analysis (FEA) has been adopted. Although there is conformity of the specimen dimensions there is no unique equation to measure the fracture parameters. The prediction of the fracture behaviour of pavement materials obtained by the present FEA is acceptable. The value of KIC predicted from each specimen type has been examined for its reliability by using the concept of maximum size of non-damaged defect (d max). Mode I fracture toughness predicted by SCB-1 (standard specimen) is the only consistent value, while SCB-2 and SCB-3 (specimens with shifted crack) failed in this reliability test. To check the reliability of SCB specimen for measuring the fatigue behaviour of pavement materials, the relation between the stress intensity factor range (ΔK) and the crack mouth opening displacement (CMOD) through the whole life of the specimen has been examined. A good relation is found between the CMOD and the ΔK through the whole life of SCB specimen.

Nonlinear Mechanical Behavior Analysis of Flexible Lateritic Pavements of Senegal (West Africa) by FEM for M.-E. Pavement Design

Pavement design in Senegal is based on a linear elastic behavior of pavement materials and the hypothesis of a static loading. However, previous works on the mechanical behavior of road materials showed that this one is reversible after several loading cycles and depends on the applied stress. The described behavior is from then on, purely nonlinear. One of the objectives of this research is to determine the parameters of response of lateritic pavement materials submitted to road traffic by using FEM. Therefore, experiments were made on gravel lateritic soils from Dougar, Sebikotane, Mont-Rolland, Pâ Lo and Ngoundiane. The Young’s modulus of the materials was defined in unconfined compression test while repeated load triaxial test was performed to determine the resilient modulus of the gravels and the appropriate model (Uzan model). An implementation was realized with Cast3M©. The importance of the nonlinearity was revealed in a very clear way and was crucial in the construction of the calculation algorithm. The observations for certain conditions showed that the values of the critical responses are more important for the linear model than for the nonlinear model. However, this trend should be validated by further studies.

The influence of stone crushing processes on aggregate shape properties

Aggregate shape properties have a direct influence on the behaviour of pavement materials. The crushing process is the main factor responsible for generating these shape properties; however, there has hardly been any effort directed toward optimising the performance of pavement materials by altering the crushing techniques to produce aggregate particles with desired shape properties. The aim of this research is to analyse how the crushing process influences aggregate shape properties. Form, angularity and surface texture of five coarse and five fine aggregates, from three different quarries, were evaluated by means of digital image processing and were categorised by two different classification systems. The jaw crusher produced coarse aggregates with a better combination of sphericity and angularity during the first crushing stage. Fine aggregates produced by cone crushers in the final crushing stages were more elongated, but had a greater angularity than fine aggregates produced by the primary jaw crusher.

Impact of compaction method on mechanical characteristics of unbound granular recycled materials

Laboratory testing methods are constantly being developed to simulate true field conditions in controlled laboratory environment. The aim of laboratory testing methods is to reproduce specimens which accurately replicate field performance in terms of mechanical behaviour of pavement materials under applied loads. Compaction is the most common soil stabilisation technique in ground improvement and pavement construction works. Among the available laboratory compaction methods, the impact method followed by the static method are the most commonly used procedures. Since the nature and approach of these two compaction methods are fundamentally different, an investigation on the effect of using these techniques on the mechanical performance of pavement materials prepared by each of these methods is essential, so as to better understand both these compaction methods. In this regard, two types of recycled construction and demolition (C&D) materials suitable for pavement applications, namely crushed brick (CB) and recycled concrete aggregate (RCA) were selected. Laboratory specimens were prepared using the above-mentioned procedures. Different aspects of geotechnical characteristics of the specimens, including aggregate breakage, changes in soil–water characteristics, stiffness, and resilient characteristics, were investigated. The outcomes of this research indicate that the influence of method of compaction must be considered when interpreting the laboratory test results for field design purposes.

Impact of Compaction Methods on Resilient Response of Unsaturated Granular Pavement Material

Compaction of aggregates is an important part of the design, construction and research of pavement geotechnics projects. An important application of compaction is sample preparation for pavement design studies. Conventionally, the impact method of compaction is used for studies on pavement materials. However, recently, some researchers have been using other methods of compaction, such as static compaction, specifically for studying the unsaturated behavior of pavement materials. The objective of this study is to investigate the effect of compaction techniques on resilient behavior of compacted laboratory specimens. Studies show that the resilient behavior of unsaturated compacted road pavement materials is influenced by suction. In this regard, two types of recycled Construction and Demolition (C&D) material were selected and static and impact compaction methods were utilized for sample preparation. Further, accuracy of four predictive resilient modulus models with or without incorporation of suction was investigated. Test results show the impact of compaction method on particle breakage, matric suction and accordingly resilient behavior of C&D granular material.

목재칩을 활용한 포장재의 현장 적용성 평가

Construction materials using soil which is the most common material around us have many advantages, but their long-term durability and sensation of walking as pavements have problems. Therefore, they are used after compaction or mixed with various hardening agents such as lime and cement for strength enhancement. However, studies on the behavior of pavement materials mixed with environment-friendly hardening agents or admixtures to improve walking property are still insufficient. In this study, therefore, in order to evaluate the appropriate mixing ratio and field application characteristics of pavement materials using mixed soils with environment-friendly hardening agents and natural materials such as wood chips, mechanical tests were performed to evaluate the rational mixing ratios and the ball test was performed as an elasticity test to evaluate the field applicability. The results suggest that the content of wood chips should be selected at 1.5% or lower according to the purpose of the structure, and the hardening agent at 10~15%. The evaluation results for GB/SB coefficient ratio which indicates the walking property show that the appropriate mixing ratio of the hardening agent in terms of the sensation of walking is 15% of lower, but different mixing ratios should be chosen according to the proportion of wood chips.

Possible estimation of resilient modulus of fine-grained soils using a dynamic lightweight cone penetrometer

Resilient modulus is an important parameter to characterise the resilient behaviour of pavement materials. Resilient modulus can be determined in the laboratory from repeated load triaxial test and is defined as the ratio of deviator stress to recoverable strain. Inherently, it is a challenge to perform repeated load triaxial tests as a routine basic test due to its complicated, time-consuming and expensive procedure; hence, several empirical approaches to estimate the resilient modulus from other soil mechanical properties – California bearing ratio, unconfined compressive strength or physical properties – have been proposed. This study has investigated the application of a dynamic lightweight cone penetrometer for the estimation of the resilient modulus in the laboratory and field conditions for some Victorian fine-grained subgrade soils. The results show the possibility to estimate the resilient modulus of fine-grained soils using the dynamic lightweight penetration index at any moisture content (MC) from optimum MC to soaked conditions.

Development Of A Pavement Rutting Model Using Shakedown Theory

Abstract The rutting of flexible pavements during their exploitation is considered to be one of the main problems in UK as well as worldwide. It is a serious mode of distress alongside fatigue in bituminous pavements that may lead to premature failure, as indicated by permanent deformation or rut depth along the wheel load path, and results in early and costly rehabilitation. This kind of pavement distress makes a negative impact to the serviceability characteristics of the flexible pavement, to the residual life of pavement structure and also to the safety and ride quality for traffic. Two design methods have been used to control rutting: one to limit the vertical compressive strain on the top of subgrade and the other to limit rutting to a tolerable amount usually around “12 mm”. Although experimental data and practical experience have been introduced into these design methods through empirical parameters, there is not a simple relationship between the elastic strain and the long-term plastic behaviour of pavement materials. This paper describes a method based on the kinematic shakedown theorem for constructing a mathematical model to predict the long-term behaviour of pavement structures under the action of repeated and cyclic loadings imposed by moving traffic. This method seeks the mechanism from within a class of mechanisms that minimises the shakedown limit load for pavement structures consisting of layers of Mohr-Coulomb materials. The model differs from extant models, in that the cyclic nature of the loading on a pavement is recognised from the outset, and the current method which is based upon foundation analysis, is replaced by a procedure employing shakedown theory that features the capabilities and applications of the developed technique for assessing rutting in flexible pavements. The basic concepts are outlined together with the most recent calculations of the critical design shakedown load. The influence of the design parameters such as, the strength, stiffness and depth of the granular base-course material as well as the consequences of traffic loading (number of equivalent standard axel loads – ESAL’s) are discussed.

Bituminous Materials with a High Resistance to Flow Rutting

The importance of developing an analysis of the flexural behavior of beams is related firstly to the use of beams as a basic element in the realization of structures, and also to characterize the mechanical properties of laminates and sandwich materials from bending test performed on specimens shaped beams. Determining the mechanical behavior of pavement materials is used to calculate the distribution of stresses and strains in the pavement as the rigidity of the materials to determine the thickness to set up according to the resistance of these materials to different damage mechanisms, depending on climate and traffic. Comparison of the mechanical behavior of materials used to make a selection of the type of materials and interventions based on their performance. In addition, knowledge of the mechanical behavior of materials used to develop specifications based on the on the physical properties of these materials and selection criteria for the type of intervention based on a cost analysis of the life cycle. This study examines the mechanical behavior of a bituminous material quasi-compact. It aims to develop a pattern of behavior meets the requirements for industrial exploitation. Experimental responses show a behavior similar to that of concrete, namely the asymmetry. Only the normal stress is taken into account. Although for different layers, the normal distribution of the stress is linear and is based only on the depth of the beam. However, the stress distribution in the beam is not perfectly linear but piecewise linear.

Sensitivity analysis of crack propagation in pavement bituminous layered structures using a hybrid system integrating Artificial Neural Networks and Finite Element Method

The paper presents results of sensitivity analysis to crack propagation of a pavement bituminous layered structure using the Finite Element Method (FEM) and Artificial Neural Networks (ANN).The performed preliminary study determined stresses and displacements in the pavement layer system. The pavement structure consisting of asphalt layers, a base layer, subbase and subgrade layers was analyzed as a 2D finite element model using the ABAQUS computer software. The second method, i.e. the extend Finite Element Method was applied, to simulate cracking process of the bituminous layer of a road surface. The pavement model was subjected to static load. Both linear and non-linear material properties of the pavement layers were considered to discuss crack propagation sensitivity in the pavement layers.A hybrid system integrating Artificial Neural Networks (ANN) and FEM was considered to model the material of asphalt layers in flexible pavements. The tests for Radial Basis Function (RBF) and Multi-Layer Perceptron (MLP) networks were carried out. In the formulated model the ANN requires inputs such as: layers thickness, load value and the Young’s moduli of each layer creating the pavement. The data for the ANN were obtained from Finite Element Method analysis. The aim of the network learning process as non-destructive testing was to evaluate the pavement material behavior and estimation of the crack propagation sensitivity. The main conclusion is that cracking considerably increases with a decrease in the thickness of bituminous layer B2. The thickness of the asphalt layer B1 has much less considerable effect on the cracking of the subgrade layer.

Shakedown Approaches to Rut Depth Prediction in Low-Volume Roads

Rutting, due to permanent deformations of unbound materials, is one of the principal damage modes of low traffic pavements. Flexible pavement design methods remain empirical; they do not take into account the inelastic behavior of pavement materials and do not predict the rutting under cyclic loading. A finite-element program, based on the concept of the shakedown theory developed by Zarka for metallic structures under cyclic loadings, has been used to estimate the permanent deformations of unbound granular materials subjected to traffic loading. Based on repeated load triaxial tests, a general procedure has been developed for the determination of the material parameters of the constitutive model. Finally, the results of a finite-element modeling of the long-term behavior of a flexible pavement with the simplified method are presented and compared to the results of a full-scale flexible pavement experiment performed by Laboratoire Central des Ponts et Chaussees. Finally, the calculation of the rut depth evolution with time is carried out.

Runway Instrumentation and Response Measurements

This paper presents ongoing research to measure the in situ response to airplane traffic of flexible pavement on a runway at Cagliari-Elmas Airport in Italy. Understanding how pavement materials respond to traffic and environmental loading is fundamental to designing pavements and assessing their performance. The pavement material behavior is affected by many factors (i.e., load magnitude, material properties, and environmental conditions). The influence of these factors can be simultaneously taken into account by measuring in situ stresses and strains using embedded instruments. The pavement layers of the Cagliari-Elmas runway were equipped with 149 instruments: 36 linear variable differential transformers, 36 pressure cells, four time domain reflectometers, 28 T-thermocouples, and 45 hot-mix asphalt strain gauges. The instrumented area, 55 m2, allows measuring the responses during three main loading maneuvers: taking off, landing, and taxiing. The preliminary data acquired during and after the runway's construction and before its opening to airplane traffic and its analysis show that the instrumentation process was a success. The instrument response testing includes falling weight deflectometer, truck, and airplane loading of various types, magnitudes, and speeds. The collected data were successfully compared with preliminary numerical simulations. Further data collection and research will be performed, particularly involving airplane traffic data. Data analysis will include the effect of the environmental data (i.e., moisture and temperature) and airplane configuration and speed. The collected data will be used to validate advanced pavement modeling and predict pavement runway performance. In addition, data resulting from this research have the potential to support and improve runway pavement design and to improve the evaluation process for new and existing runway pavement performance and damage prediction.

Finite elements modelling of the long‐term behaviour of a full‐scale flexible pavement with the shakedown theory

AbstractRutting, due to permanent deformations of unbound materials, is one of the principal damage modes of low‐traffic pavements. Flexible pavement design methods remain empirical; they do not take into account the inelastic behaviour of pavement materials and do not predict the rutting under cyclic loading. A simplified method, based on the concept of the shakedown theory developed by Zarka for metallic structures under cyclic loadings, has been used to estimate the permanent deformations of unbound granular materials subjected to traffic loading. Based on repeated load triaxial tests, a general procedure has been developed for the determination of the material parameters of the constitutive model. Finally, the results of a finite elements modelling of the long‐term behaviour of a flexible pavement with the simplified method are presented and compared with the results of a full‐scale flexible pavement experiment performed by Laboratoire Central des Ponts et Chaussées. Finally, the calculation of the rut depth evolution with time is carried out. Copyright © 2008 John Wiley & Sons, Ltd.

Effects of Moisture and Time on Stiffness of Unbound Aggregate Base Coarse Materials

Resilient modulus and Young's modulus are parameters increasingly used to characterize the behavior of pavement materials, both in the laboratory and in the field. The small-strain modulus response of unbound aggregate base coarse materials to various moisture environments was documented. Modulus is not constant, even when held at constant moisture, and significant changes in modulus occur with drying and wetting of the material. The response to drying and wetting cycles appears to be repeatable and suggests that the underlying mechanism that controls the response is reversible. This behavior can have a significant effect on the use of modulus for pavement design and quality acceptance.