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asphalt-concrete
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Discrete Element Simulation of Creep Behavior in Asphalt Mixtures
,
M.Sc. Thesis
Sharif University of Technology
;
Tabatabaei, Nader
(Supervisor)
Abstract
Composite nature of asphalt mixtures necessitates a micromechanical scheme which depends on distinctive characteristics of various constitutive phases. In this regard, discrete element method was utilized to predict the creep behavior of asphalt mixtures and strain response in primary, secondary and tertiary stages. In this research, a modified mixture modeling procedure was considered to better simulate permanent deformation response of asphalt mixtures under creep loading. A random distribution of mastic and aggregate particles with respect to a typical dense gradation was implemented to reconstruct cylindrical specimens. A bonding model represented the cohesion effect in mastic...
Experimental investigation of rest time effect on permanent deformation of asphalt concrete
, Article Journal of Materials in Civil Engineering ; Volume 28, Issue 5 , 2016 ; 08991561 (ISSN) ; Sorkhabi, H ; Karimi, M. M ; Sharif University of Technology
American Society of Civil Engineers (ASCE)
Abstract
Asphalt concrete is a complex mixture, the behavior of which is dependent on its components while showing different nonlinear behaviors under various conditions. Application of rest time between compressive loading cycles causes hardening-relaxation (H-R) behavior in the sample and increases the deformation potential of the sample. This process might induce changes in the microstructure and the pattern of the placement and rotation of the aggregates. These changes cause a relaxation in the hardening of the material, pose a higher potential of reception of viscoplastic strain in the following cycles, and increase the rate of accumulation of the permanent deformation in contrast with creep...
Microstructure-Based Visco-Elastoplastic Continuum Model of Asphalt Concrete
, M.Sc. Thesis Sharif University of Technology ; Tabatabaei, Nader (Supervisor)
Abstract
Asphalt concrete is a heterogeneous and multi-phase material that consists of aggregates, asphalt binder, and pores. These components create a complex microstructure. There is no consensus on how to quantify the microstructure and the required parameters from two-dimensional images. The load transfer can be managed by aggregate-aggregate or aggregate-mastic interactions that depend on the gradation, aggregate internal structure, and asphalt binder viscoelastic properties. The most important internal structure indices affecting the behavior of HMA are aggregate orientation, contact orientation, contact length, and number of contact points. In this research, the influence of aggregate...
Investigating the Effect of Softening Agent on the Performance Characterization of Asphalt Concrete Mixture with High RAP Content
, M.Sc. Thesis Sharif University of Technology ; Tabatatabee, Nader (Supervisor)
Abstract
Recycling of asphalt pavements has received much attention in recent years for its environmental and economical benefits. Because of increase in costs of raw materials and energy carriers, reuse of a high portion of reclaimed asphalt pavements (RAP) eliminates an enormous amount of waste and reduces the cost of hot-mix asphalt (HMA) mixtures. There are some problems in high-RAP mixtures such as high content of fine aggregate and filler, low temperature cracking potential because of higher stiffness of RAP binder, and low mixture workability. In this research, RAP fractionation was used to sort out and eliminate fine aggregate and filler. An organic-based softening agent was used to improve...
Micromechanical Modeling the Viscoelastic Performance of the Asphalt Concrete with Finite Element
, M.Sc. Thesis Sharif University of Technology ; Tabatabaee, Nader (Supervisor)
Abstract
Asphalt concrete is a composite mixture of three phases; aggregate, bitumen and air void. Stress and strain distributions obtained from macroscopic modeling yield different results due to distinctly different mechanical properties of the above-mentioned phases. In this study a more exact analysis of the stress and strain, were carried out by considering the mixture as a two-phase composite; aggregate and mastic phases. Asphalt concrete was considered a composite material consisted of sand mastic and aggregate. Aggregate and mastic phases were separated and response of the loaded asphalt mixture was investigated. Aggregates finer than 2.36 mm in diameter, filler and bitumen consist the...
A thermodynamic-based large deformation viscoplastic constitutive relationship for asphalt concrete compaction
, Article International Journal of Solids and Structures ; Volume 165 , 2019 , Pages 192-216 ; 00207683 (ISSN) ; Darabi, M. K ; Tabatabaee, N ; Sharif University of Technology
Elsevier Ltd
2019
Abstract
This research proposes a large deformation, time-dependent viscoplastic constitutive relationship to enhance the prediction of the compaction degree of asphalt concrete materials under laboratory and field conditions. A large-deformation thermodynamic-based framework is presented. The Helmholtz free energy and rate of energy dissipation functions were assumed to derive rate-dependent constitutive relationships to relate multi-axial state of stresses to the recoverable and non-recoverable deformation response of asphalt concrete during compaction. A straightforward method that allows the calibration of the proposed model against laboratory compaction data (e.g., data from Superpave Gyratory...
Empirical and Numerical Modeling of Viscoelastic-Viscoplastic Constitutive Equation for Asphalt Mixture Compaction
, Ph.D. Dissertation Sharif University of Technology ; Tabatabaee, Nader (Supervisor)
Abstract
The numerical simulation of asphalt concrete and pavement has gained considerable attention in recent decades. Information about the response of asphalt pavements during construction and in-service traffic loading is required by pavement specialists for improvement of pavement analysis and design methods. The goal of this study was to propose a constitutive relationship and a numerical modeling method for asphalt concrete compaction in the laboratory and in situ. Asphalt binders exhibit rate-dependent viscoelastic and viscoplastic mechanical behavior in asphalt concrete. The current study examined the viscoelastic and viscoplastic mechanical behavior of asphalt concrete under various loading...
Strength parameters of asphalt concrete used in core zone of earth dams
, Article Proceedings of the 17th International Conference on Soil Mechanics and Geotechnical Engineering: The Academia and Practice of Geotechnical Engineering ; Volume 2 , 2009 , Pages 1558-1561 ; 9781607500315 (ISBN) ; Yousefpour, N ; Sharif University of Technology
Abstract
Strength parameters of asphalt concrete used in earth fill dams' core were studied by conducting cyclic and monotonic triaxial tests on asphalt concrete samples. Results obtained from more than 120 cyclic tests showed that asphalt concrete behaves properly under cyclic loading and specimens stay intact after applying 5000 cycles. Results of monotonic and post-cyclic loading proved that strength parameters of asphalt concrete samples does not change significantly after being subjected to seismic loads. © 2009 IOS Press
Development of a stress-mode sensitive viscoelastic constitutive relationship for asphalt concrete: experimental and numerical modeling
, Article Mechanics of Time-Dependent Materials ; 2016 , Pages 1-35 ; 13852000 (ISSN) ; Tabatabaee, N ; Jahanbakhsh, H ; Jahangiri, B ; Sharif University of Technology
Springer Netherlands
Abstract
Asphalt binder is responsible for the thermo-viscoelastic mechanical behavior of asphalt concrete. Upon application of pure compressive stress to an asphalt concrete specimen, the stress is transferred by mechanisms such as aggregate interlock and the adhesion/cohesion properties of asphalt mastic. In the pure tensile stress mode, aggregate interlock plays a limited role in stress transfer, and the mastic phase plays the dominant role through its adhesive/cohesive and viscoelastic properties. Under actual combined loading patterns, any coordinate direction may experience different stress modes; therefore, the mechanical behavior is not the same in the different directions and the asphalt...
Interface between tire and pavement
, Article Journal of Materials in Civil Engineering ; Volume 29, Issue 9 , 2017 ; 08991561 (ISSN) ; Toufigh, V ; Sharif University of Technology
Abstract
Sliding friction between a pavement and tire is an important concern in traffic safety. The British pendulum test has been used worldwide to evaluate friction characteristics of pavement surfaces. However, because of considerable differences in apparatus, procedures, and operation, significant variability can occur for evaluations of British pendulum number (BPN). In this investigation, a direct shear test (DST) device is modified and proposed to determine the sliding friction coefficient between tire and pavement surface under dry and wet conditions. Dissipated energy values obtained from DST were compared with evaluations of BPN, and a high correlation was obtained. Tests were done using...
Development of a stress-mode sensitive viscoelastic constitutive relationship for asphalt concrete: experimental and numerical modeling
, Article Mechanics of Time-Dependent Materials ; Volume 21, Issue 3 , 2017 , Pages 383-417 ; 13852000 (ISSN) ; Tabatabaee, N ; Jahanbakhsh, H ; Jahangiri, B ; Sharif University of Technology
Springer Netherlands
2017
Abstract
Asphalt binder is responsible for the thermo-viscoelastic mechanical behavior of asphalt concrete. Upon application of pure compressive stress to an asphalt concrete specimen, the stress is transferred by mechanisms such as aggregate interlock and the adhesion/cohesion properties of asphalt mastic. In the pure tensile stress mode, aggregate interlock plays a limited role in stress transfer, and the mastic phase plays the dominant role through its adhesive/cohesive and viscoelastic properties. Under actual combined loading patterns, any coordinate direction may experience different stress modes; therefore, the mechanical behavior is not the same in the different directions and the asphalt...
Constitutive modeling of hardening-relaxation response of asphalt concrete in cyclic compressive loading
, Article Construction and Building Materials ; Volume 137 , 2017 , Pages 169-184 ; 09500618 (ISSN) ; Tabatabaee, N ; Jahangiri, B ; Darabi, M. K ; Sharif University of Technology
Abstract
Cyclic loading on asphalt concrete materials with a longer relaxation time and lower remaining stress lead to higher viscoelastic strain recovery. Consequently, more aggregate reorientation occurs and the rate of viscoplastic strain increases in subsequent cycles. The present study proposes a hardening relaxation constitutive relationship (fHR) as a function of accumulated recovered viscoelastic strain εrve based on experimental observation. This model captures the initiation and evolution of hardening-relaxation during the relaxation time and/or stress reduction under cyclic loading. The model was then coupled with viscoelastic, viscoplastic and viscodamage constitutive relationships. The...
Evaluation of the geo-mechanical parameters of the interface between asphalt concrete and sand with applying direct shear test and numerical modeling
, Article Advanced Materials Research ; Volume 587 , 2012 , Pages 116-121 ; 10226680 (ISSN) ; 9783037855133 (ISBN) ; Rostami, A ; Karimi, M. M ; Taherkhani, H
2012
Abstract
Asphaltic concrete has been used as waterproofing core in embankment dams, since 1948. In this application, the asphaltic core is surrounded by granular filter materials. The interaction of the asphaltic concrete and the granular materials has not been sufficiently investigated. In this paper the mechanical behavior of the interface between a natural smooth sand filter and asphaltic concrete at different levels of normal stresses and a constant shear strain rate has been studied. Small scale direct shear test has been conducted in this study, in which the shear surface is considered as the interface. Asphalt concrete specimens used in the shear test were cut in square shape (10×10×2.5 cm)...
Network-level pavement roughness prediction model for rehabilitation recommendations
, Article Transportation Research Record ; Issue 2155 , 2010 , Pages 124-133 ; 03611981 (ISSN) ; Stoffels, S. M ; Tabatabaee, N ; Sharif University of Technology
Abstract
Pavement performance models are key components of any pavement management system (PMS). These models are used in a network-level PMS to predict future performance of a pavement section and identify the maintenance and rehabilitation needs. They are also used to estimate the network conditions after the application of various maintenance and rehabilitation alternatives and to determine the relative cost effectiveness of each maintenance and rehabilitation alternative. Change in pavement surface roughness over time is one of the most important performance indicators in this regard. A model for changes in the international roughness index (IRI) over time was developed through artificial neural...