The Experts below are selected from a list of 10815 Experts worldwide ranked by ideXlab platform
Hao Wang - One of the best experts on this subject based on the ideXlab platform.
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Moisture effect on nanostructure and adhesion energy of asphalt on Aggregate surface: A molecular dynamics study
Applied Surface Science, 2020Co-Authors: Wei Sun, Hao WangAbstract:Abstract This study aims at investigating the moisture effect on nanostructure and adhesive energy of asphalt-Aggregate Interface in asphalt mixture at atomistic scale. Molecular Dynamics (MD) simulations were conducted to study the molecular interaction between virgin and aged asphalt binder with silica and calcite. The MD simulation results were used to investigate the effect of water intrusion on the nanostructure of virgin and aged asphalt binder on Aggregate surface. The adhesion energy and debonding energy of asphalt-Aggregate Interface were compared at dry and wet conditions. In particular, the contributions of saturate, aromatic, resin, and asphaltene (SARA) components of asphalt binder to total adhesion energy were decomposed and analyzed. It was found that the existence of interfacial water changed the nanostructure of asphalt binder, including the self-aggregation of asphaltene and the distribution characteristics of SARA components. Although oxidative aging had different influences on adhesion energy of asphalt binder with silica and calcite, the interfacial water reduced adhesion energy regardless of Aggregate type. The SARA components of asphalt binder exhibited different bonding ability with Aggregate. The moisture effect on adhesion energy of SARA components varied in different trends, different from the overall adhesion energy.
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molecular dynamics simulation of asphalt Aggregate Interface adhesion strength with moisture effect
International Journal of Pavement Engineering, 2017Co-Authors: Hao Wang, Guangji XuAbstract:AbstractThis study developed an atomistic simulation framework based on the classical molecular dynamics (MD) method to study the moisture-induced damage at the asphalt-Aggregate Interface. The Interface adhesion strength of the asphalt–quartz system was predicted using MD simulation for the first time. The Interface stress-separation curve under tension that was obtained from MD simulation resembles the failure behaviour measured from the pull-off strength conducted at the macroscopic scale. The results show that the presence of moisture at the asphalt–quartz Interface significantly reduces the Interface adhesion strength. The Interface failure process is affected by the chemical compositions of asphalt. The Interface adhesion strength decreases as the moisture content increases or the temperature increases. It was found that the atomistic model size (number of atoms) and the loading rate in MD simulation have considerable effects on the predicted Interface adhesion strength. The findings from MD simulat...
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molecular dynamics study of interfacial mechanical behavior between asphalt binder and mineral Aggregate
Construction and Building Materials, 2016Co-Authors: Guangji Xu, Hao WangAbstract:Abstract This study aims to study the deformation and failure behavior of the asphalt-Aggregate Interface using molecular dynamics (MD) simulations. The 12-component asphalt molecular models and the hydrated silica substrate were employed to form a bi-material Interface system. Physical properties of asphalt binder were predicted from MD simulations including density and glass transition temperature for model validation with experimental data. Tensile simulations were performed and the stress-separation responses were obtained to analyze the interfacial mechanical behavior. It was found that the Interface failure was mainly adhesive failure although large air voids were formed in the bulk asphalt as the loading rate decreases to a certain level. The Interface failure strength and post-peak deformation are affected by loading rate and temperature that is consistent the viscoelastic behavior of asphalt binder. The stress-separation responses match the cohesive zone model (CZM) model that is usually observed in the pull-off strength test at the macroscopic scale. The relationship between chemical compositions of asphalt binder and the Interface failure parameters was investigated. The MD simulation shows promising results to understand mechanical failure of asphalt-Aggregate Interface at the atomistic scale.
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study of cohesion and adhesion properties of asphalt concrete with molecular dynamics simulation
Computational Materials Science, 2016Co-Authors: Guangji Xu, Hao WangAbstract:Abstract The objectives of this study is to develop a molecular modeling approach for studying cohesive and adhesive properties of asphalt concrete and evaluate the accuracy of modeling through comparisons with experimental data. Fully atomistic models were built for molecular dynamics (MD) simulation considering two representative asphalt models and two types of Aggregate mineral. MD simulations were performed to study thermodynamic and cohesive properties of asphalt binder, such as density, solubility parameter, cohesive energy density, and surface free energy. The adhesion properties were investigated by calculating the interaction energy and the work of adhesion at asphalt–Aggregate Interface for the first time. The bond energy parameters in dry and wet conditions were used to evaluate moisture sensitivity of Interface adhesion. The results show that van der Waals force plays critical role for cohesive properties of asphalt binder; while the adhesion bonding between asphalt to Aggregate is largely dependent on the type of Aggregate mineral (silica or calcite) in both dry and wet surface conditions. The effect of asphalt type was found significant for the adhesion between asphalt and silica at the relatively small moisture content. The simulation results agree well with experimental measurements reported in the literature. This work illustrates MD can help in understanding fundamental chemo-mechanics relationship of asphalt concrete at an atomistic scale, which can be used as a useful tool for material design and performance prediction.
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micromechanical analysis of asphalt mixture fracture with adhesive and cohesive failure
Engineering Fracture Mechanics, 2014Co-Authors: Hao Wang, Jian Wang, Jiaqi ChenAbstract:Abstract This paper investigated the fracture behavior of asphalt mixture using randomly generated two-dimensional (2-D) microstructure models. Asphalt mixture was modeled as a multi-phase heterogeneous material with both adhesive and cohesive failure potential. Viscoelastic properties were assigned to asphalt binder. Two different fracture models, cohesive zone model (CZM) and extended finite element model (XFEM), were adopted to simulate the fracture damage within the Fine Aggregate Matrix (FAM) (cohesive failure) and at the FAM–Aggregate Interface (adhesive failure), respectively. The numerical simulation offers both qualitative and quantitative results to understand the fracture behavior of asphalt mixture considering the interaction between cohesive and adhesive failure. Parametric studies were conducted to evaluate the effect of loading rate, FAM modulus, and fracture parameters on fracture potential of asphalt mixture. This study provides an effective method to study the fracture mechanism of heterogeneous material by considering different fracture mechanisms for matrix material and bi-material Interface.
Hussain U. Bahia - One of the best experts on this subject based on the ideXlab platform.
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evaluating adhesion properties and moisture damage susceptibility of warm mix asphalts bitumen bond strength and dynamic modulus ratio tests
Transportation Research Record, 2012Co-Authors: Mohammad Zia Alavi, Elie Y Hajj, Andrew Hanz, Hussain U. BahiaAbstract:Through development and evaluation of the warm-mix asphalt (WMA) mixture design process, increased moisture susceptibility has been cited as one of the potential critical failure modes for WMA. Reduced production temperatures can affect the drying of the Aggregate before mixing, the development of adhesion at the asphalt-Aggregate Interface, and binder stiffness. The objective of this research is to identify the significance of these factors and to define their relative contribution to mixture resistance to moisture damage. To evaluate the contribution of asphalt binder-Aggregate adhesion, the bitumen bond strength (BBS) test was implemented on dry and moisture-conditioned samples. The effect of production temperature was simulated by heating Aggregate substrates to hot-mix asphalt (HMA) and WMA temperatures before applying the asphalt binder. Furthermore, the effect of reduced binder stiffness resulting from lower production temperatures was considered through establishing two controls for mixture perfor...
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measuring the effect of moisture on asphalt Aggregate bond with the bitumen bond strength test
Transportation Research Record, 2011Co-Authors: Raquel Moraes, Raul Velasquez, Hussain U. BahiaAbstract:Understanding moisture damage mechanisms in asphalt pavements and evaluating the right combination of materials that are resistant to moisture damage are important. Moisture damage is the loss of strength or stiffness in asphalt mixtures caused by a combination of mechanical loading and moisture. Many test methods have been developed to evaluate loss of adhesion and cohesion in binders. However, a simple procedure to address moisture damage in the asphalt-Aggregate Interface is not available. The feasibility of the newly developed bitumen bond strength (BBS) test for moisture damage characterization was investigated. An experimental matrix that included various binders, modifications, and Aggregates to account for the chemical and physical conditions in the Aggregate-asphalt Interface was completed. A statistical analysis was performed to verify reproducibility of the BBS test. The results indicated that the bond strength of asphalt-Aggregate systems was highly dependent on modification and moisture expos...
Guangji Xu - One of the best experts on this subject based on the ideXlab platform.
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molecular dynamics simulation of asphalt Aggregate Interface adhesion strength with moisture effect
International Journal of Pavement Engineering, 2017Co-Authors: Hao Wang, Guangji XuAbstract:AbstractThis study developed an atomistic simulation framework based on the classical molecular dynamics (MD) method to study the moisture-induced damage at the asphalt-Aggregate Interface. The Interface adhesion strength of the asphalt–quartz system was predicted using MD simulation for the first time. The Interface stress-separation curve under tension that was obtained from MD simulation resembles the failure behaviour measured from the pull-off strength conducted at the macroscopic scale. The results show that the presence of moisture at the asphalt–quartz Interface significantly reduces the Interface adhesion strength. The Interface failure process is affected by the chemical compositions of asphalt. The Interface adhesion strength decreases as the moisture content increases or the temperature increases. It was found that the atomistic model size (number of atoms) and the loading rate in MD simulation have considerable effects on the predicted Interface adhesion strength. The findings from MD simulat...
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molecular dynamics study of interfacial mechanical behavior between asphalt binder and mineral Aggregate
Construction and Building Materials, 2016Co-Authors: Guangji Xu, Hao WangAbstract:Abstract This study aims to study the deformation and failure behavior of the asphalt-Aggregate Interface using molecular dynamics (MD) simulations. The 12-component asphalt molecular models and the hydrated silica substrate were employed to form a bi-material Interface system. Physical properties of asphalt binder were predicted from MD simulations including density and glass transition temperature for model validation with experimental data. Tensile simulations were performed and the stress-separation responses were obtained to analyze the interfacial mechanical behavior. It was found that the Interface failure was mainly adhesive failure although large air voids were formed in the bulk asphalt as the loading rate decreases to a certain level. The Interface failure strength and post-peak deformation are affected by loading rate and temperature that is consistent the viscoelastic behavior of asphalt binder. The stress-separation responses match the cohesive zone model (CZM) model that is usually observed in the pull-off strength test at the macroscopic scale. The relationship between chemical compositions of asphalt binder and the Interface failure parameters was investigated. The MD simulation shows promising results to understand mechanical failure of asphalt-Aggregate Interface at the atomistic scale.
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study of cohesion and adhesion properties of asphalt concrete with molecular dynamics simulation
Computational Materials Science, 2016Co-Authors: Guangji Xu, Hao WangAbstract:Abstract The objectives of this study is to develop a molecular modeling approach for studying cohesive and adhesive properties of asphalt concrete and evaluate the accuracy of modeling through comparisons with experimental data. Fully atomistic models were built for molecular dynamics (MD) simulation considering two representative asphalt models and two types of Aggregate mineral. MD simulations were performed to study thermodynamic and cohesive properties of asphalt binder, such as density, solubility parameter, cohesive energy density, and surface free energy. The adhesion properties were investigated by calculating the interaction energy and the work of adhesion at asphalt–Aggregate Interface for the first time. The bond energy parameters in dry and wet conditions were used to evaluate moisture sensitivity of Interface adhesion. The results show that van der Waals force plays critical role for cohesive properties of asphalt binder; while the adhesion bonding between asphalt to Aggregate is largely dependent on the type of Aggregate mineral (silica or calcite) in both dry and wet surface conditions. The effect of asphalt type was found significant for the adhesion between asphalt and silica at the relatively small moisture content. The simulation results agree well with experimental measurements reported in the literature. This work illustrates MD can help in understanding fundamental chemo-mechanics relationship of asphalt concrete at an atomistic scale, which can be used as a useful tool for material design and performance prediction.
B. I. G. Barr - One of the best experts on this subject based on the ideXlab platform.
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combined effects of silica fume Aggregate type and size on post peak response of concrete in bending
Materials, 1999Co-Authors: Canan Tasdemir, Mehmet Ali Tasdemir, B. I. G. Barr, Nicholas Mills, F.d. LydonAbstract:The influences of silica fume, type, and size of Aggregate on the prepeak and postpeak response of high-strength concretes in bending were investigated by measuring the fracture energy, the characteristic length, and brittleness index. Degradation of stiffness and strength were also measured, and a unique focal point was determined using unloading-reloading cycles during the tests. The degradation of stiffness was correlated to the local fracture energy, strength degradation, permanent crack mouth opening displacement (CMOD), and permanent displacement at midspan. It was shown that relations between normalized stiffness, load, local energy, CMOD, and permanent displacement at midspan were independent of the partial replacement of cement by silica fume and of the type and size of Aggregate. Based on the fracture tests and microscopic studies at the matrix-Aggregate Interface, it was concluded that, in both limestone and gravel concretes without silica fume, the cement-Aggregate Interface had a large amount of calcium hydroxide and also much less dense calcium silicate hydrate; however, in concretes with silica fume, the interfacial zone became stronger, more homogeneous, and dense. In the latter concretes, the fracture energy decreased dramatically, especially when they contained 20-mm maximum size Aggregate, and in these concretes, the brittleness index was substantially high. In gravel Aggregate concretes with and without silica fume, cracks developed around the Aggregates and generally did not traverse them, because of the particle shape and smooth surface; however, in concretes with silica fume, crack surfaces were less tortuous and fracture was in a more brittle manner. In limestone concretes with silica fume, the cracks usually traversed the Aggregates and a transgranular type of fracture was observed.
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Effects of silica fume and Aggregate size on the brittleness of concrete
Cement and Concrete Research, 1996Co-Authors: Canan Tasdemir, Mehmet Ali Tasdemir, F.d. Lydon, B. I. G. BarrAbstract:Abstract The effects of silica fume and Aggregate size on the softening response and brittleness of high strength concretes were investigated by measuring the fracture energy GF, the characteristic length lch and brittleness index B. Based on the fracture tests and microscopic studies at the Aggregate-matrix Interface, it was concluded that, in concretes without silica fume, the cement-Aggregate Interface had a profusion of calcium hydroxide and also much less dense calcium silicate hydrate, hence, the cracks usually developed at this weak Interface, i.e. around coarse Aggregate. However, in concretes with silica fume, the interfacial zone became stronger, more homogeneous and dense, hence, the cracks usually traversed the Aggregates; transgranular type of fracture was observed. In these concretes, the fracture energy decreased dramatically especially for large size of Aggregate case and as a result the brittleness index increased significantly.
F.d. Lydon - One of the best experts on this subject based on the ideXlab platform.
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combined effects of silica fume Aggregate type and size on post peak response of concrete in bending
Materials, 1999Co-Authors: Canan Tasdemir, Mehmet Ali Tasdemir, B. I. G. Barr, Nicholas Mills, F.d. LydonAbstract:The influences of silica fume, type, and size of Aggregate on the prepeak and postpeak response of high-strength concretes in bending were investigated by measuring the fracture energy, the characteristic length, and brittleness index. Degradation of stiffness and strength were also measured, and a unique focal point was determined using unloading-reloading cycles during the tests. The degradation of stiffness was correlated to the local fracture energy, strength degradation, permanent crack mouth opening displacement (CMOD), and permanent displacement at midspan. It was shown that relations between normalized stiffness, load, local energy, CMOD, and permanent displacement at midspan were independent of the partial replacement of cement by silica fume and of the type and size of Aggregate. Based on the fracture tests and microscopic studies at the matrix-Aggregate Interface, it was concluded that, in both limestone and gravel concretes without silica fume, the cement-Aggregate Interface had a large amount of calcium hydroxide and also much less dense calcium silicate hydrate; however, in concretes with silica fume, the interfacial zone became stronger, more homogeneous, and dense. In the latter concretes, the fracture energy decreased dramatically, especially when they contained 20-mm maximum size Aggregate, and in these concretes, the brittleness index was substantially high. In gravel Aggregate concretes with and without silica fume, cracks developed around the Aggregates and generally did not traverse them, because of the particle shape and smooth surface; however, in concretes with silica fume, crack surfaces were less tortuous and fracture was in a more brittle manner. In limestone concretes with silica fume, the cracks usually traversed the Aggregates and a transgranular type of fracture was observed.
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Effects of silica fume and Aggregate size on the brittleness of concrete
Cement and Concrete Research, 1996Co-Authors: Canan Tasdemir, Mehmet Ali Tasdemir, F.d. Lydon, B. I. G. BarrAbstract:Abstract The effects of silica fume and Aggregate size on the softening response and brittleness of high strength concretes were investigated by measuring the fracture energy GF, the characteristic length lch and brittleness index B. Based on the fracture tests and microscopic studies at the Aggregate-matrix Interface, it was concluded that, in concretes without silica fume, the cement-Aggregate Interface had a profusion of calcium hydroxide and also much less dense calcium silicate hydrate, hence, the cracks usually developed at this weak Interface, i.e. around coarse Aggregate. However, in concretes with silica fume, the interfacial zone became stronger, more homogeneous and dense, hence, the cracks usually traversed the Aggregates; transgranular type of fracture was observed. In these concretes, the fracture energy decreased dramatically especially for large size of Aggregate case and as a result the brittleness index increased significantly.