Modeling And Analysis Of Molecular Dynamics For Characterizing Asphalt-aggregate Interaction

The paper reveals the asphalt-aggregate interfacial mechanism from the micro level based on moleculardynamics simulation and supplemented by contrast verification test, the studies are as follows:Firstly, by means of molecular dynamics which is based on Material Studio software, theasphalt/aggregate interfacial microscopic characteristics is simulated. The asphaltene/oxide interface modelis established and the effect of aggregate composition on asphalt-aggregate interfacial bonding strength isanalyzed. The results show that in addition to the asphaltene/K₂O interface, the interfacial energy of the restcan all achieve maximum value in25℃or80℃, bonding strength reaches the maximum. Six kinds ofinterface can reach the minimum value in40℃, bonding strength reaches the minimum. From10℃to100℃, the interfacial energy of six interfaces can not be sorted clearly at the same temperature. However, if weexclude the two oxides of Na₂O and K₂O, the interaction of asphaltene and four oxides are as follows:MgO>CaO>Al₂O₃>SiO₂. From10℃to100℃, the interfacial energy range of asphaltene/asphaltene is-10.464178³.792104KJ/mol, the maximum is reached in25℃or80℃while the minimum in60℃.Secondly, the composition of asphalt/aggregate is studied from micro level, which is constituted bymuch microscopic asphalt/oxide interface. Otherwise the asphalt/aggregate interfacial failure modes andestimation method based on molecular dynamics is proposed. The results show that the asphalt/aggregateinterfacial damage is mainly cohesive failure when the surface of aggregate contains CaO and MgO; thedamage is mainly adhesive failure when the surface of aggregate contains Al₂O₃, but maybe cohesivefailure in40℃; the damage is the mixed failure of adhesive and cohesive when the surface of aggregatecontains SiO₂、Na₂O and K₂O.Thirdly, the water-temperature coupling effect on the asphalt/aggregate interface by thermodynamicanalysis is studied and the asphalt film peeling mechanism of water damage is explained from micro level.The rain is acid or weak acid, as the surface water evaporates, water acidity reduces and environmentaltemperature increases. When water reaches the asphalt/aggregate, CaO and MgO are eroded which the twokinds of oxide are bonded with asphalt strongly. So the interfacial bonding strength of asphalt/aggregate isweakened, asphalt film fall off and water damage occur. Lastly, in the road engineering, especially the water damage of Asphalt Pavement, the content of SiO₂as the classification index of aggregate cannot adequately instruct the engineering practice. Consequently,the paper presents a new aggregate index: the content of CaO and MgO.