Analyzing moisture diffusion in the interface between rubber-modified asphalt and aggregate: A 3D study considering multiple influencing factors

Abstract

Moisture erosion is inevitable at the interface between rubber-modified asphalt and aggregate. When moisture penetrates the interface through diffusion, it causes varying degrees of damage. In this study, molecular simulation technology was used to simulate the moisture diffusion interface considering multiple influencing factors. The radial distribution function (RDF), mean square displacement (MSD), and relative concentration profile (RCP) were calculated to evaluate the moisture diffusion direction. Density functional theory was employed to measure the interaction between rubber-modified asphalt components and H2O molecules, and the moisture-damaged areas were analyzed using crystal orbital populations, which can obtain three-dimensional (3D) diffusion mechanism. The results demonstrated that the remaining free H+ ions interacted with the aromatic ring and CC (double bond) in the rubber. Under the effects of multiple factors such as loading and temperature conditions, moisture permeates the rubber-modified asphalt and aggregate interface, resulting in overall degradation of the composition. Furthermore, the hydrogen atoms in the free OH- groups attract the more polar heteroatoms surrounding them.