Design Of Pavement Structures Research Articles

Normalized comparative study on fatigue characteristics of different pavement materials

At present, many test methods and models have been used to evaluate the fatigue performance of pavement materials. However, different test methods and material types have a significant impact on the fatigue result evaluation. Thus, to evaluate the fatigue characteristics of different pavement materials under diverse test methods, the strength and fatigue performance of three pavement materials were characterized through direct tension, uniaxial compression, and indirect tensile tests at multiple loading rates and stress levels. In this paper, three pavement materials, such as SBS-modified asphalt mixture (SBS-MAM), crumb rubber asphalt mixtures (CRAM), and cement-stabilized macadam (CSM), were tested. On this basis, the strength yield surface models related to loading rates and the fatigue normalized unified model of three pavement materials under various stress states were established. Comparing the differences among the three pavement materials' fatigue performance, the results show that the fatigue results of the three pavement materials were completely different under dissimilar test methods. The conventional fatigue equation cannot evaluate the influence of specimen size and stress state on fatigue performance. However, the fatigue normalization model established in this paper can settle these problems. It is also clear that the fatigue performance of CSM is superior to those of the other two mixtures when the stress level is small. However, the fatigue life of CSM is significantly more sensitive to the stress level than those of the other two mixtures. Based on the establishment and comparative analysis of the normalized models of fatigue characteristics of different pavement materials, the scientific conversion of pavement material fatigue to structural fatigue is realized, which provides sights into the anti-fatigue design of pavement structures.

Key Points of RIOHTRACK Testing Road Design and Construction

The technical orientation, pavement structure and material design scheme of the first full-scale test track (RIOHTRACK) in China, and the composition of the testing platform, including vehicle loading and data collection, etc., are introduced. RIOHTRACK has 19 kinds of designed pavement structure putting on the straight and transition curve, these pavement structures cover domestic and foreign engineering application cases, including flexible base course, semi-rigid base course and rigid base course, and different asphalt structural layers and material combination modes. The 19 kinds of pavement are classified according to the design idea and evaluation objective, and the design standard, verification objective, structure character and material technique requirement, etc. of each pavement structure are discussed separately. Using the multi-axle loading vehicle with a total weight of 100 t, the all-weather accelerated loading on the above typical pavement structures is conducted, and the performance of these pavement structures is quantified and compared. The result can be used for research of equivalent load conversion method, pavement damage prediction model, the method of structure and material optimal design, and maintenance technical standard.

Dynamic simulation of FWD tests on flexible transversely isotropic pavements with imperfect interfaces

Developing an accurate and efficient forward model of the dynamic response of pavement structure is of great significance for obtaining the design parameters of the layered pavement structure through an inverse calculation based on the measured pavement data. However, the existing algorithms rarely consider the interlayer contact. Based on the traditional spectral element method (SEM), this study proposes a new forward model to simulate the falling weight deflectometer (FWD) dynamic tests for the transversely isotropic layered pavement structure. The interfaces between the pavement layers can be imperfect, and the displacement boundary conditions are discontinuous. Moreover, the developed model considerably enhances the efficiency of the model in solving the dynamic response of transversely isotropic layered media by avoiding the infinite integration in integral transformation. Numerical examples verify the accuracy and efficiency of the model developed in this study. At the same time, an extensive parameter analysis is conducted on the interlayer contact of the pavement structure and inhomogeneity of the layered soil, which provides a reliable, numerical, theoretical basis for the design of pavement structure.

Evaluation of the cracking and aging susceptibility of asphalt mixtures using viscoelastic properties and master curve parameters

Aging can significantly affect the performance of asphalt mixtures, causing increase in stiffness, reduction in relaxation capability and increase in cracking susceptibility. It is also well known that fundamental viscoelastic properties are used for design and modelling of asphalt mixtures and pavement structures to addressing rutting, fatigue and thermal cracking concerns. The objective of this paper is to study how the viscoelastic properties of asphalt mixture change over time, and evaluate and identify the cracking and aging susceptibility of asphalt mixtures with different mix variables during material selection and mixture design. Ten mixtures are evaluated using different laboratory conditioning protocols to simulate a range of aging levels in the field. The complex modulus test is then conducted on the lab aged mixtures to measure the viscoelastic properties in order to construct the dynamic modulus and phase angle master curves. The mixture Glover-Rowe (G-Rm) parameter and the shape parameters of the dynamic modulus and phase angle master curves, including inflection point frequency (−β/γ), difference between the glassy modulus and the inflection point modulus (γ), peak value of phase angle (a) and the horizontal position (frequency) of the peak phase angle value (c), are determined and evaluated for the mixtures with different aging conditions and mix variables. The study indicates the ability of the G-Rm parameter and all the master curve shape parameters to capture the effect of different aging conditions on linear viscoelastic mixture properties, as well as the cracking and aging susceptibility of asphalt mixtures.

Shakedown of asphalt pavements considering temperature effect

ABSTRACT Shakedown limit has been perceived as a useful guidance in pavement structure design against rutting. However, temperature, as one key factor influencing the shakedown limit of asphalt pavements, has barely been considered. In this paper, the shakedown phenomenon was first identified from wheel tracking tests for a pavement structure consisting of a dense bituminous macadam layer and a granular layer at 40°C. Based on a previously developed shakedown approach and the material elastic and plastic properties obtained through a series of tests, lower-bound shakedown limits of the layered system were determined and compared with the wheel tracking test results. Following that, an empirical relation between temperature and cohesion of asphalt mixture was suggested. A temperature-dependent shakedown approach was then proposed which can quickly obtain the shakedown limits of asphalt pavements over a range of temperatures. Results show that the shakedown limits decrease markedly with increasing temperature, accompanied by a shift of the failure mode from a granular layer failure to an asphaltic layer failure. One effective and economic way to enhance the pavement performance under high temperature is improving shear strength properties of asphalt mixtures. By using this method, pavement stability against rutting can be evaluated efficiently at any temperature.

Dynamic simulation of falling weight deflectometer tests on flexible transversely isotropic layered pavements

Developing an accurate and efficient forward model of the dynamic response of pavement structure is of great significance for obtaining the design parameters of the layered pavement structure through inverse calculation based on the measured pavement data. Based on the spectral element method, this study proposes an accurate and efficient numerical dynamic model of falling weight deflectometer tests for the transversely isotropic layered pavement structure. The developed algorithm considerably enhances the efficiency of the model in solving the dynamic response of transversely isotropic layered media by avoiding the infinite integration in integral transformation. Moreover, numerical examples verify the accuracy and efficiency of the algorithm developed in this study. At the same time, an extensive parametric studies have been carried out to clarify the effects of the Young's modulus in the vertical direction and thickness of the layered pavement structure as well as the elastic modulus of the thin interlayer on the dynamic response of the pavement, which provides a reliable, numerical, theoretical basis for the design of pavement structure.

Investigation of Strength and Fatigue Life of Rubber Asphalt Mixture.

Strength and fatigue life are essential parameters of pavement structure design. To accurately determine the pavement structure resistance of rubber asphalt mixture, the strength tests at various temperatures, loading rate, and fatigue tests at different stress levels were conducted in this research. Based on the proposed experiments, the change law of rubber asphalt mixture strength with different temperatures and loading rates was revealed. The phenomenological fatigue equation of rubber asphalt mixture was established. The genetic algorithm optimized backpropagation neural network (GA-BPNN) is highly reliable for optimizing production processes in civil engineering, and it has a remarkable application effect. A GA-BPNN strength and fatigue life prediction model was created in this study. The reliability of the prediction model was verified through experiments. The results showed that the rubber asphalt mixture strength decreases and increases with the increase of temperature and loading rate, respectively. The goodness of fit of the rubber asphalt mixture strength and fatigue life prediction model based on the GA-BPNN could reach 0.989 and 0.998, respectively. The indicators of the fatigue life prediction model are superior to the conventional phenomenological fatigue equation model. The GA-BPNN provides an effective method for predicting the rubber asphalt mixture strength and fatigue life, which significantly improves the accuracy of the resistance design of the rubber asphalt pavement structure.

Laboratory Evaluation of Gradation Improvement of Marginal Materials for Foamed Bitumen Stabilisation

Foamed bitumen stabilisation is an attractive technology for increasing the use of marginal materials in pavement construction and rehabilitation. However, by their very nature, marginal materials do not meet the prescriptive requirements of many standard specifications. Consequently, performance-related evaluation is required. For foamed bitumen stabilised marginal materials, the cured and saturated moduli are common performance-related parameters that are also used for characterisation during structural pavement design. In this research, the indirect tensile moduli of three foamed bitumen stabilised marginal granular materials were compared to the modulus of a standard or premium material, in both cured and saturated conditions, after 3, 7 and 14 days of accelerated laboratory curing. The results indicated that the magnitude of granular material marginality was not related to the stabilised material modulus. Furthermore, the gradations of the two most marginal materials were improved by blending with another granular material and the improved marginal materials were also stabilised and tested. The gradation improvement had a variable effect on the stabilised material modulus, with the average modulus increasing by more than 20%. The modulus increase associated with the gradation improvement was related to the basis and magnitude of granular material marginality, with the saturated modulus of the most plastic marginal material increasing by the greater amount after improvement. It was concluded that foamed bitumen stabilisation is a particularly effective treatment for marginal granular materials. Furthermore, when used in combination with gradation improvement, the resulting foamed bitumen stabilised material can perform similarly to standard materials, based on cured and soaked modulus values. However, to allow the use of foamed bitumen stabilised marginal materials in pavement construction, specifications must be more performance-related and the current limits on plasticity and gradation must be relaxed.

Analysis on Three-Dimensional Strength Influencing Factors and Control Measures of Asphalt Mixtures.

Strength is an important parameter for the design of asphalt pavement materials and structures. To study the influence of various factors on the three-dimensional strength of asphalt mixtures, three aggregate gradations (dense-graded bituminous mixture AC-13, stone mastic asphalt SMA-13 and bituminous stabilization aggregate paving mixture OGFC-13) and two binders (SBS modified bitumen and 70# base bitumen) were used to prepare the asphalt mixture specimens. Among them, SBS+SMA-13 asphalt mixture has the best performance. On this basis, the uniaxial compressive test, uniaxial tensile test and confining triaxial test were conducted on the SBS+SMA-13 asphalt mixture under six oil-stone ratios conditions (5.5%, 5.7%, 5.9%, 6.1%, 6.3%, and 6.5%), six temperatures conditions (5 °C, 10 °C, 15 °C, 20 °C, 25 °C, and 30 °C), and five loading rates conditions (1 mm/min, 2 mm/min, 3 mm/min, 4 mm/min, and 5 mm/min). In addition, a unified three-dimensional strength calculation model considering the influence of temperature, loading rate, and oil-stone ratio was proposed, and the change law of the three-dimensional strength with these above factors was revealed. Furthermore, two sets of three-factor three-level orthogonal tests were carried out on the SMA-13 asphalt mixture. The sensitivity analysis and strength regulation research between three-dimensional strength and each factor were carried out. The results show that the type of asphalt has the greatest influence on the strength of the mixture, the temperature has the second most influence, the loading rate has less influence, and the oil-stone ratio has the least influence. The strength regulations proposed to improve the strength of the asphalt mixture include the use of modified asphalt, high-temperature stability high-quality asphalt, and the lower oil-stone ratio than the Marshall optimal oil-stone ratio. The strength control measures proposed from the perspective of the three-dimensional stress state, the joint failure of each stress components and real stress states are taken into consideration.

Characterizing Influence of Water Access Condition during Freezing on Resilient Behavior of Alaskan Base Course Materials

Accurate characterization of the resilient behavior of the base course materials under different climatic conditions is critical for the design of reliable and cost-effective pavement structures. In Alaska, the resilient behavior of base course materials usually undergoes significant variation due to seasonal change and extreme climatic conditions. Previous studies have revealed that the resilient behavior of base course materials could be significantly influenced by the freezing process. In this study, the freezing process under two extreme conditions (i.e., free and no water access conditions) that base course materials could possibly experience in the field was simulated using a one-dimensional frost heave cell. The influences of the water access condition during freezing on the frost heave and resilient modulus (MR) of the base course materials with different fines and initial water contents was assessed based on the results from the freezing process and repeated load triaxial tests. A pressure plate test was also performed to build the relationship between suction and water content of soils with different fines content. Suction was then introduced to model MR of the materials tested under unfrozen conditions before and after a freeze–thaw cycle. The adoption of suction significantly simplified the equation for MR prediction. Finally, structural analyses were conducted using BISAR and Alaska Flexible Pavement Design (AKFPD) software and the results revealed that free water access during freezing can significantly accelerate cracking and reduce pavement service life.

Analisis Perencanaan Tebal Perkerasan Kaku Lajur Pengganti pada Proyek Pembangunan Jalan Tol Jakarta-Cikampek II Elevated

Road widening is a construction phase of Jakarta-Cikampek II elevated Toll Road construction project. Improving the effectiveness and road service capability influence the traffic activity. This study aimed to analyze alternative rigid pavement design and thickness based on the Road Pavement Design Manual (MDPJ) 2017 and American Association of State High-way and Transportation Officials Guide for Design of Pavement Structures (AASTHO) 1993. This research was conducted on March – May 2019. Based on the obtained data, a rigid pavement design alternative using the MDPJ 2017 method showed concrete plate thickness of 305 mm and using the AASHTO 1993 concrete plate thickness was 320 mm. In actual condition the concrete plate thickness was 300 mm.

Structural performance of jointed reinforced concrete pavement slab with subbase erosion

Structural behavior of jointed reinforced concrete pavement (JRCP) slab is sensitive to the subbase erosion which is considered in pavement design as a potential failure mode. However, erosion of subbase has not been clearly addressed in the JRCP design specifications. The most widely used procedures for the design of pavement slabs is specified in the Guide for Design of Pavement Structures (AASHTO 1986, 1993, and 2008). In this study a simple but effective 2D finite element (FE) structural response model is proposed and utilized to examine the effect of subbase erosion on the JRCP slab performance. The FE model considers different JRCP slab thicknesses and dimensions and different subbase erosion scenarios. The results of the proposed FE model indicate that considering the subbase erosion in JRCP slab design may require a substantial increase in slab reinforcement; however, it can lead to less damage and longer lifespan of the pavement slab.

Prediction of permanent deformation for subgrade soils under traffic loading in Southern China

ABSTRACT The cumulative permanent strain of subgrade soils plays an important role in the pavement structure design and long-term pavement performance maintenance. In Southern China, the hot and humid climate increases the risk of becoming a saturated condition for subgrade soils. The saturated subgrade soils will generate significant cumulative permanent strain under long-term cyclic loading compared with unsaturated soils. This study investigated the impact of the moisture content, number of cyclic loading, deviatoric stress and confining pressure on the evolution of the cumulative permanent strain for subgrade soils by using long-term cyclic (10,000 cycles) triaxial tests. The test results indicated that the cumulative axial permanent strain increase with the increasing moisture content, as well as the increasing number of cyclic loading and deviatoric stress but decreases with the increasing confining pressure. In order to predict the permanent deformation of subgrade soils in Southern China, a new model for predicting the permanent deformation of subgrade soil, which contains number of cyclic loading, initial bulk stress, octahedral shear stress and saturation, was proposed and validated.

Advanced characterization of unbound granular materials for pavement structural design in Egypt

ABSTRACT Currently, Egypt is using the [AASHTO, 1993. Guide for design of pavement structures. Washington, DC: American Association of State Highway and Transportation Officials] guide for the flexible pavement structural design. In this method the resilient modulus (MR) of the unbound granular base/subbase materials and subgrade soils is a measure of material stiffness used for characterisation. It is considered one of the major factors affecting the pavement layerthicknesses. However, in Egypt, California Bearing Ratio (CBR) is the main strength parameter used for characterisation of the unbound materials and subgrade soils due to its availability and simplicity. In this research, a comprehensive experimental testing programme was conducted on different unbound granular base/subbase materials typically used in pavement construction projects in Egypt. The testing programme includes MR, CBR, and basic material properties. The effect of aggregate gradation on MR is investigated. A model predicting MR as a function of the basic material properties is proposed. The MR–CBR relationship adopted in the current Egyptian Code of Practice is verified based on the testing results. The experimental data warranted the calibration of the current model. The calibrated model has reasonable goodness of fit statistics and yields rational MR estimates for the local materials.

Evaluation of the Coordination of Structural Layers in the Design of Asphalt Pavement

The purpose of asphalt pavement structural design is to get a materially-coordinated and structurally-durable product, and a pavement structure with good road performance by combining the structural layer materials reasonably. However, due to lack of a rational evaluation index on the parameter combinations of structural layer materials, the structural layer materials are poor in terms of coordination, have low efficiency, and the actual use period is much lower than the designed working life. Therefore, it is very important to conduct research evaluating the coordination of the structural layer materials. In this study, the sensitivity of mechanical parameters and equivalent envelope area are proposed as new indexes to evaluate the coordination of material design of asphalt pavement structure layers. Software is developed to calculate the equivalent envelope area that can quantitatively evaluate the coordination among different layers and visualize the mechanical transfer behavior of each structural layer. Based on the equivalent envelope area index, this study incorporates two new steps in the design of pavements, namely the structural form comparison and optimization, and proposes a new structural design process. Finally, the rationality and reliability of the equivalent envelope area index are verified by presenting fatigue life calculation and field verification in a test road. The results propose a clear evaluation index of the coordination of material design of each structural layer, which makes the structural design of the asphalt pavement more scientific and reasonable.

Mechanistic-Empirical Compatible Traffic Data Generation: Portable Weigh-in-Motion versus Cluster Analysis

Abstract Axle load distribution factors (ALDFs) are used as one of the primary traffic data inputs for mechanistic-empirical (ME) pavement design methods for predicting the impact of varying traffic loads on pavement performance with a higher degree of accuracy than empirical methods that are solely based on equivalent single axle load (ESAL) concept. Ideally, to ensure optimal pavement structural design, site-specific traffic load spectra data—generated from weigh-in-motion (WIM) systems—should be used during the pavement design process. However, because of the limited number of available permanent WIM stations (in Texas, for example), it is not feasible to generate a statewide ALDFs database for each highway or project from permanent WIM data. In this study, two possible alternative methods, namely, the direct measurement using a portable WIM system and the cluster analysis technique, were explored for generating site-specific ME-compatible traffic data for a highway test section, namely, state highway (SH) 7 in Bryan District (Texas). The traffic data were then used for estimating pavement performance using a ME pavement design software, namely, the Texas Mechanistic-Empirical Thickness Design System (TxME). The TxME-predicted pavement performance (e.g., rutting) using the portable WIM-generated traffic input parameters closely matched with the actual field performance. Overall, the study findings indicated that the portable WIM (with proper installation and calibration) constitutes an effective means for rapidly collecting reliable site-specific ME-compatible traffic data.

Long-Term Field Performance of Flexible Pavements Using Warm Mix Asphalt Technologies

An increased awareness of sustainability in the pavement industry has encouraged the use of warm mix asphalt (WMA) technologies. Compared to conventional hot mix asphalt (HMA) that requires a high production temperature, WMA has several benefits, such as saving fuel and energy, reducing greenhouse gas emissions, and improving the work environment. However, systematic analysis of long-term field performance for pavements containing WMA mixtures has been scarce. Therefore, the objectives of this paper are to evaluate the field performance of flexible pavements using WMA technologies (referred as WMA pavements in this paper) and compare the general trend of the longer-term performance between WMA and HMA pavements across the United States. Specifically, 28 WMA pavement projects along with their companion HMA pavements were evaluated for an extended performance period in terms of transverse cracking, longitudinal cracking, rutting, and moisture damage. A companion HMA pavement refers to the an pavement that shares similar pavement structure, climate, traffic conditions and mixture design with the WMA pavement; the main differences are the usage of WMA technologies in the surface layer and the reduced production temperature for WMA mixtures. The selected projects include five projects constructed during the course of the study, and 23 in-service projects covering different service ages, traffic volumes, pavement structures, WMA technologies, and four climatic zones across the United States. It was found that pavements containing various WMA technologies exhibited comparable long-term field performance as compared to that of the companion HMA pavement in terms of transverse cracking, wheel path longitudinal cracking, and rutting. No moisture-related distress was found in the field for either HMA or WMA pavements. Overall, cracking and rutting performance show a clear pattern of climate influence. Cracking distress appears to be more of a concern within wet climatic zones while less typical in dry climatic zones, which suggests that moisture should be considered in evaluating the cracking potential of asphalt mixtures. Results presented herein were part of NCHRP Project 9-49A on the Performance of WMA Technologies: Stage II—Long-Term Field Performance.

Combined Fourier-wavelet transforms for studying dynamic response of anisotropic multi-layered flexible pavement with linear-gradual interlayers

The objective of this study is to develop an analytical solution for studying dynamic response of anisotropic multi-layered flexible pavement with linear-gradual interlayers under a harmonic moving load. In this study, the flexible pavement structure is simplified as one multi-layered flexible system, which is assumed to be a semi-infinite medium. A new approach combining the Fourier transform with the wavelet transform for solving the dynamic analytical solution. The wavelet transforms for solving inverse Fourier transform, in solving the solution in the physical domain, is superior to the conventional inverse Fourier transform. The linear-gradual interlayer between the adjacent layers is defined using the shear spring model, and the anisotropic property is simplified as transverse isotropy. Also, in the dynamic analytical solving processes, the motion in the transversely isotropic medium is decoupled into in-plane motion and out-of-plane motion because of the propagation of the waves in a transversely isotropic medium with coupling phenomena. The corresponding analytical solution is entered into a MATLAB-based computer program, which can compute the dynamic responses of an anisotropic multi-layered medium at different interlayer conditions. The accuracy of this program is confirmed through comparison with the results from the examples from the references. The influence analyses of linear-gradual interlayers and anisotropic properties of structural layers are illustrated. It is concluded that the proposed analytical solution-based computer program could be used in the multi-layered flexible pavement structural design and risk management in civil engineering.

Finite-Element Simulation of Instrumented Asphalt Pavement Response under Moving Vehicular Load

AbstractUnderstanding the structural behavior of layered asphalt pavements subjected to dynamic moving wheel loads is a crucial requirement for the future design of more-durable pavement structures...

Technical system, key scientific problems and technical frontier of long-life pavement

The development of long-life pavement is the most effective means to reduce the resource consumption of road construction and maintenance. It can also relieve the traffic congestion which is caused by large and medium scale maintenance of pavement, and improve the road capacity and road network transportation efficiency. In this paper, the basic characteristics of long-life pavement were illustrated, and the current technology system of long-life pavement was introduced. The key technical problems and main scientific problems of the long-life pavement structure design, the design and development of durable pavement materials, and the pavement maintenance management and large and medium scale maintenance were analyzed. The results indicated that the pavement structure is a large scale spatial three-dimensional structure although it is simple in geometry. It is necessary to select three-dimensional elastic mechanics theory or even more complicated mechanical theory to analyze its mechanical response. The pavement materials exhibit the viscoelastic plastic characteristics, because most of the pavement materials use asphalt as binder. Therefore, only the visco-elastic- plastic mechanics theory can accurately describe the mechanical behavior of the pavement. Moreover, under the multi- physics coupling effects of temperature, humidity, ultraviolet rays and ice, snow, water, steam, the scientific problems inherent in the pavement structure are very complex. The material used for pavement is a kind of mixture with multi-phase, multi-scale, multi-component features. The micro-structure characteristics inside material, the micro-mechanism of load and load transfer, the damage evolution occurred and developed inside material, along with the corresponding relationship between them and the structural macro-performance parameters are extremely complicated. The performance characteristics of pavement material should be scientifically described as the guidance for the scientific design of the pavement material and the scientific analysis of the pavement structure. For this regard, some suggestions were proposed for the method of mechanical analysis, pavement structure design, the development of durability of road materials, and long-life pavement maintenance. For mechanical analysis and pavement structure design, the following researches could be conducted in future: (1) Constitutive theory of the multi-phase, multi-scale, multi-component materials; (2) strength theory and failure criterion of pavement materials under three-dimensional stress state; (3) fatigue failure criterion of pavement materials in three dimensional state; (4) spatiotemporal response characteristics and its evolution patterns of pavement structure performance under the coupling action of multiple physical fields; (5) robustness of sub-grade stiffness field and its relation to the mechanical behavior of pavement structure; (6) real time perception and information analysis of mechanical response characteristics of pavement structure during full scale test. As to the development of durability of road materials, the most efforts should be put into the modification of mix proportion design method of mixture, improvement of the durability of binder, and the study and development functional pavement materials. As to the long-life pavement maintenance, the most efforts should be put into theory and method about the timely perception, reflection and inversion of pavement structure performance, theory and technology about the fast perception of pavement performance, long term performance of pavement and the evolution model of the long term performance of pavement, the evaluation, prediction and intelligent decision-making of pavement performance, and technical principle and method of efficient utilization of reclaimed asphalt pavement. These researches provided direction for the development of perpetual pavements.