Investigation of the solution effects on asphalt binder and mastic through molecular dynamics simulations

The asphalt mixture is easily affected by water erosion with different solutes. The molecular dynamics (MD) simulation method was adopted to explore the influence of solute on the nanostructure and interface interaction of both virgin/SBS asphalt binder and mastic. The changes of potential energy of asphalt solution erosion model (ASEM), as well as fractions aggregation caused by water molecules were observed. Moreover, differences on diffusion of water molecules caused by the studied solutes were explained. On this basis, the analysis of hydrogen bonds is also carried out. The results showed that saline/alkali solutes hindered the diffusion of water molecules, where water molecules in saline environment behaved the slowest diffusion rate. Meanwhile, salt maximized the hydrogen bond adsorption of water molecules on the surface of filler (silica). The mastic with a filler/binder ratio of 1.2 had the highest diffusion coefficient. From the interface perspective, an obvious interaction between calcite and solution was detected, and the salt and alkali proceeded the debonding effect of original water condition. The alkali solution led to the greatest moisture damage to the asphalt-solution-aggregate model (ASAM), followed by the saline solution. In this case, the SBS asphalt binder/mastic exhibited a higher water stability than the virgin. This study contributed to a basic reference for understanding the moisture-induced damage of asphalt mixtures under various solution conditions.