Interfacial Performance of Asphalt-Aggregate System under Different Conditions Based on Molecular Dynamics Simulation

Abstract

The interface between asphalt and aggregate directly determines the performance of asphalt mixtures but unavoidable weaknesses can be easily found at the interfacial bonding region. In order to evaluate the interfacial adhesion behavior between asphalt and aggregate at the atomic scale, asphalt binders and two mineral aggregates (quartz and calcite) were selected to build molecular models and molecular dynamics (MD) simulations were conducted. The interfacial energy between asphalt and aggregate was calculated and the mineral aggregate has a more significant influence on the energy compared to the binder types. Also, the simulation result indicates that saturate, aromatic, resin, and asphaltene (SARA) components have different interfacial energies with respect to the aggregates. This result can also be derived from the relative concentration of SARA components on the aggregate surface. Additionally, oxidation of the asphalt binder results in increased interfacial energy due to the enhanced intermolecular bonding generated by oxidized functional groups. The intrusion of water greatly reduces the interfacial energy, but the energy increases under the coupling effect of oxidation and moisture, especially for calcite. The grey relational grade theory was conducted to evaluate the factors affecting the adhesive energy, and the results show that the energy of the asphalt-aggregate is more sensitive to the asphaltene index than other factors.