Molecular dynamics simulation of the bitumen-aggregate system and the effect of simulation details

摘要

The bitumen-aggregate interface is regarded as a significant weak link in asphalt mixtures. Therefore, the fundamental understanding of adhesion between bitumen and aggregate is crucial for designing and preserving asphalt pavement. By far, the molecular dynamics simulation method has notably attracted interest in the characterization of the bitumen-aggregate system. However, the effort towards a reasonable simulation is still ongoing. This study investigated nine cases of bitumen-aggregate systems using molecular dynamic simulations. Specifically, three bitumen binders and three mineral types were considered, respectively. In addition, mineral surface properties and some simulation details were discussed, aiming to obtain a reasonable simulation. The results indicated that polar molecules in bitumen played a vital role in the adhesion between bitumen and aggregates. The mineral surface properties in terms of mineral cleavage surface, surface atomic charge, and surface hydroxylation significantly influenced the simulation results. Accordingly, some simulation tricks were recommended for molecular dynamic simulation of bitumen-aggregate systems: (1) Geometry optimization for the mineral model is not necessary; (2) A vacuum slab with 0 angstrom should be added on the cleaved surface; (3) Chemical bonds should be deleted after the construction of the bitumen-aggregate system; (4) The Ewald and Atom-based methods are recommended for the energy summation of electrostatic energy and Van der Waals energy, respectively. (C) 2021 Elsevier Ltd. All rights reserved.