An Investigation of the Interfacial Healing Behavior of Graphene-Modified Asphalt Binders Simulated Using Molecular Dynamics and the Two-Piece Healing Test

Microscopic tests, molecular dynamics (MD) simulation, and two-piece healing (TPH) approaches were employed to investigate the interfacial intrinsic healing behavior and mechanisms of graphene-modified asphalt (GMA) binders at different aging levels. A vacuum layer 10-Å thick was injected between two molecules of asphalt binder to resemble a pattern of cracks. The mean squared displacement (MSD), molecular diffusion coefficient (D), and surface free energy (SFE) of asphalt molecules were utilized to evaluate the micro intrinsic healing behavior of asphalt binders. The macro intrinsic healing capacity of asphalt binders was determined using the intrinsic healing function [Rh(t)] developed from the TPH test. The GMA binder had a higher healing efficiency than the base binder in the short-term healing condition according to the density of the MD simulations, the SFE of the sessile drop method, and the initial healing rate (R0) of the TPH experiment. GMA binder had higher potential for instantaneous healing than the base binder because of its greater SFE in general. According to an analysis of parameters MSD, D, and Rh(t) quantified by MD simulations and TPH tests, the GMA binder had a greater capacity for long-term healing than the base binder after a long-term aging process. An R2 of 0.87 was obtained from the regression analysis of R0 against SFE, and an R2 of 0.93 was obtained from the regression analysis of Rh(3,600)−R0 against D. The experimental findings at the macroscopic scale and the simulation outcomes at the microscopic level were mutually supportive.