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This thesis presents a continuum model for asphalt concrete incorporating non- linear viscoelasticity, viscoplasticity, mechanically-induced damage and moisture- induced damage. The Schapery single-integral viscoelastic model describes the nonlinear viscoelastic response. The viscoplastic model of Perzyna models the time- dependent permanent deformations, using a Drucker-Prager yield surface which is modified to depend on the third deviatoric stress invariant to include more complex dependence on state of stress. Mechanically-induced damage is modeled using continuum damage mechanics, using the same modified Drucker-Prager law to determine damage onset and growth. A novel moisture damage model is proposed, modeling moisture-induced damage using continuum damage mechanics; adhesive moisture- induced damage to the asphalt mastic-aggregate bond and moisture-induced cohesive damage to the asphalt mastic itself are treated separately. The analytical model is implemented numerically for three-dimensional and plane strain finite element analyses, and a series of simulations is presented to show the performance of the model and its implementation. Sensitivity studies are conducted for all model parameters and results due to various simulations corresponding to laboratory tests are presented. In addition to the continuum model, results are presented for a micromechanical model using the nonlinear-viscoelastic-viscoplastic-damage model for asphalt mastic and a linear elastic model for aggregates. Initial results are encouraging, showing the strength and stiffness of the mix as well as the failure mode varying with moisture loading. These initial results are provided as a an example of the model's robustness and suitability for modeling asphalt concrete at the mix scale.
A comprehensive material identification experimental program is developed in this study. The experimental program is designed such that the quantification and decomposition of the response into viscoelastic and viscoplastic components can be achieved. The developed experimental program and theoretical framework are used to analyze repeated creep tests conducted on three mixes that include aggregates with different characteristics.
The objective of this research is to develop an accurate and advanced material characterization model for predicting response of asphalt mixtures subjected to compression loading. The first step of the modeling is to check the validity of the time-temperature superposition principle for asphalt concrete with growing damage and viscoplastic strain in the compression state. Constant crosshead rate compression test results are used to construct the stress-log reduced time master curves for various strain levels. Research results indicate that asphalt concrete with growing damage remains thermorheologically simple (TRS), and that the time-temperature shift factor is only a function of temperature and is independent of the strain level. The model encompasses the elastic, plastic, viscoelastic, and viscoplastic strain components of asphalt concrete behavior and the effects of test conditions such as temperature and loading rate on the major strain components. The modeling approach is to model each response component separately and then integrate the submodels to obtain the final viscoelastoplastic model. The viscoelastic component, including elastic strain, is modeled based on Schapery's continuum damage theory and work potential theory, whereas Uzan's strain hardening model forms the basis of the viscoplastic model that also includes the plastic strain component. The testing program required for calibrating the viscoelastoplastic model is composed of small-strain complex modulus testing at various temperatures and frequencies to determine linear viscoelastic properties, constant crosshead rate testing at low temperatures/fast loading rates for viscoelastic modeling, and repeated creep and recovery testing at high temperatures for viscoplastic modeling. The developed viscoelastoplastic model performs well in predicting material responses up to peak stress.
Premature cracking in asphalt pavements and overlays continues to shorten pavement lifecycles and creates significant economic and environmental burden. In response, RILEM Technical Committee TC 241-MCD on Mechanisms of Cracking and Debonding in Asphalt and Composite Pavements has conducted a State-of-the-Art Review (STAR), as detailed in this comprehensive book. Cutting-edge research performed by RILEM members and their international partners is presented, along with summaries of open research questions and recommendations for future research. This book is organized according to the theme areas of TC 241-MCD - i.e., fracture in the asphalt bulk material, interface debonding behaviour, and advanced measurement systems. This STAR is expected to serve as a long term reference for researchers and practitioners, as it contributes to a deeper fundamental understanding of the mechanisms behind cracking and debonding in asphalt concrete and composite pavement systems.
This book presents the latest advances in research to analyze mechanical damage and its detection in multilayer systems. The contents are linked to the Rilem TC241 - MCD scientific activities and the proceedings of the 8th RILEM International Conference on Mechanisms of Cracking and Debonding in Pavements (MCD2016). MCD2016 was hosted by Ifsttar and took place in Nantes, France, on June 7-9, 2016. In their lifetime, pavements undergo degradation due to different mechanisms of which cracking is among the most important ones. The damage and the fracture behavior of all its material layers as well as interfaces must be understood. In that field, the research activities aims to develop a deeper fundamental understanding of the mechanisms responsible for cracking and debonding in asphalt concrete and composite (e.g. asphalt overlays placed on PCC or thin cement concrete overlay placed on asphalt layer) pavement systems.
The urgent need for infrastructure rehabilitation and maintenance has led to a rise in the levels of research into bituminous materials. Breakthroughs in sustainable and environmentally friendly bituminous materials are certain to have a significant impact on national economies and energy sustainability. This book will provide a comprehensive review on recent advances in research and technological developments in bituminous materials. Opening with an introductory chapter on asphalt materials and a section on the perspective of bituminous binder specifications, Part One covers the physiochemical characterisation and analysis of asphalt materials. Part Two reviews the range of distress (damage) mechanisms in asphalt materials, with chapters covering cracking, deformation, fatigue cracking and healing of asphalt mixtures, as well as moisture damage and the multiscale oxidative aging modelling approach for asphalt concrete. The final section of this book investigates alternative asphalt materials. Chapters within this section review such aspects as alternative binders for asphalt pavements such as bio binders and RAP, paving with asphalt emulsions and aggregate grading optimization. - Provides an insight into advances and techniques for bituminous materials - Comprehensively reviews the physicochemical characteristics of bituminous materials - Investigate asphalt materials on the nano-scale, including how RAP/RAS materials can be recycled and how asphalt materials can self-heal and rejuvenator selection
Functional Pavement Design is a collections of 186 papers from 27 different countries, which were presented at the 4th Chinese-European Workshops (CEW) on Functional Pavement Design (Delft, the Netherlands, 29 June-1 July 2016). The focus of the CEW series is on field tests, laboratory test methods and advanced analysis techniques, and cover analysis, material development and production, experimental characterization, design and construction of pavements. The main areas covered by the book include: - Flexible pavements - Pavement and bitumen - Pavement performance and LCCA - Pavement structures - Pavements and environment - Pavements and innovation - Rigid pavements - Safety - Traffic engineering Functional Pavement Design is for contributing to the establishment of a new generation of pavement design methodologies in which rational mechanics principles, advanced constitutive models and advanced material characterization techniques shall constitute the backbone of the design process. The book will be much of interest to professionals and academics in pavement engineering and related disciplines.
The objective of the research presented is to develop an accurate and advanced material characterization procedure to be incorporated in the Superpave performance models system. The procedure includes the theoretical models and its supporting experimental testing protocols necessary for predicting responses of asphalt mixtures subjected to tension loading. The model encompasses the elastic, viscoelastic, plastic and viscoplastic components of asphalt concrete behavior. Addressed are the major factors affecting asphalt concrete response such as: rate of loading, temperature, stress state in addition to damage and healing. Modeling strategy is based on modeling strain components separately and then adding the resulting models to attain a final integrated ViscoElastoPlastic model. Viscoelastic response, including elastic component, is modeled based on Schapery's continuum damage theory comprising of an elastic-viscoelastic correspondence principle and work potential theory. As for the viscoplastic response, which includes the plastic component, its characterization stems from Uzan's strain hardening model. The testing program required for developing the models consists of complex modulus testing for determination of material response functions, constant crosshead rate testing at low temperatures for viscoelastic modeling, and repetitive creep and recovery testing for viscoplastic modeling. The developed model is successful in predicting responses up to localization when microcracks start to coalesce. After that, fracture process zone strains detected using Digital Image Correlation are used to extend the model's ability in predicting responses in the post-localization stage. However, once major macrocracks develop, the currently developed model ceases to accurately predict responses. At that state, the theory of fracture mechanics needs to be integrated with the current continuum damage-based model.
Analysis of Pavement Structures brings together current research and existing knowledge on the analysis and design of pavements and introduces load and thermal stress analyses of asphalt and concrete pavement structures in a simple and step-by-step manner. For the second edition of this book, a new chapter on numerical implementation (using FEM) of pavement analysis is added along with topics such as mechanical modeling of granular materials, applications of convolution theorems in visco-elasticity, visco-elastic Poisson’s ratio, concepts of fracture mechanics in relation to fatigue of asphalt mix, solution of semi-infinite and so forth. New solved examples and schematic diagrams are also added. Features: Presents a simple, step-by-step approach for pavement analysis including systematic compilation of research work in the area Discusses further elaborations in terms of extended analytical formulations on some selected topics Includes new chapter on finite element analysis for pavement structures Contains more solved examples to understand the concepts better Explores primary application of pavement analysis in pavement thickness design This book is aimed at graduate students, structural mechanics researchers, and senior undergraduate students in civil/pavement/highway/transport engineering.