Static fracture self-healing of water-damaged asphalt at molecular scale

Abstract

In order to explore the mechanism of water on self-healing of asphalt, the self-healing process of ordinary asphalt and water-damage asphalt was compared and analyzed from the molecular point of view by molecular dynamics, and was verified by macroscopic experiments. Firstly, the healing state was divided into three stages in combination with the energy change of the asphalt system: the low density stage of molecular migration, the stage of crack healing and repair, and the stage of free movement of molecules; Secondly, the radial distribution function and the mean square displacement function were used to analyze the diffusion mechanism and aggregation state of the two kinds of asphalt in crack width, moisture content and asphalt component, to explain the self-healing mechanism of asphalt and the influence mechanism of water on asphalt self-healing; Finally, macroscopic experiment verification was conducted. The results show that in the process of crack self-healing, water will hinder the intermolecular force of asphalt, weaken the energy of the asphalt system, resulting in a decrease in the diffusion force of the asphalt, and the more water content, the more obvious the decrease of diffusion force; Cracks weaken the correlation of asphalt components, destabilize asphaltene clusters and colloidal transition phases, and the number of molecules at the crack decreases as the crack size increases, which contributes to a reduction in self-healing ability. Using molecular dynamics to explain the fracture self-healing mechanism of water-damaged asphalt from the molecular scale is useful to understand the change characteristics of structural morphology and diffusion behavior of asphalt molecules during water loss, and provides a reference for the future research on self-healing of water-damaged asphalt.

Keywords

• chemical kinetics; asphalt water damage; molecular dynamics; mean square displacement; radial distribution function; self healing