Microscopic Analysis of the Miscible Process of Original and Aged Asphalt in Wood-Tar-Rejuvenated Asphalt Based on Molecular Dynamics Simulation

The miscible process of virgin and aged asphalt in rejuvenated asphalt was studied by molecular dynamics (MD) simulation. In this paper, we used MD software to establish a molecular model of asphalt, and the model of aged asphalt was established by adding ketone and sulfoxide functional groups to the original asphalt. Wood tar rejuvenator (WTR) was selected for rejuvenation of aged asphalt, and parameters such as density, surface free energy, cohesion energy density, and Young’s modulus were used to verify the molecular model. The density, relative concentration, interaction energy, mean square displacement of molecules, diffusion coefficient, mixing free energy, and radial distribution function were used to analyze the action mechanism of the rejuvenator in the rejuvenation process and the suitable service temperature and optimal amount of WTR. The results demonstrated that the WTR with 373 K and 15% mass ratio has the best rejuvenation effect on aged asphalt. The addition of WTR can increase the interaction energy between original and aged asphalt by 12.9%, reduce the Van der Waals potential energy of aged asphalt by 13.85%, and thus ensure the uniform distribution of internal molecules in rejuvenated asphalt. A 15 wt% WTR can reduce the intermolecular distance of asphaltenes from 9.4 Å to 5.2 Å, thereby alleviating the displacement effect during the asphalt aging process. The diffusion coefficients of WT-rejuvenated asphalt at 298 K and 373 K are 28.6% and 44.6% higher than those of extracted oil-rejuvenated asphalt, respectively; thus, WT-rejuvenated asphalt has better crack resistance.