Analysis of the self-healing mechanism of TB compound-modified asphalt based on molecular dynamics

Abstract

To investigate the intrinsic self-healing behavior of terminal blend (TB)-modified asphalt (TBMA), this study establishes four models of matrix asphalt, TBMA, TBMA containing styrene-butadiene-styrene (TB_SBS), and TBMA containing ethylene vinyl acetate (TB_EVA) based on molecular dynamics, and the self-healing ability of the four types of asphalt was evaluated by means of the diffusion coefficient, diffusion activation energy, and pre-exponential factor. Finally, the study analyzes and validates the self-healing performance of the asphalt through fatigue shear-healing tests. The results showed that the self-healing potentials of the four types of asphalt, as determined by the diffusion coefficient, diffusion activation energy, and pre-exponential factor, were (in descending order) TB_SBS, TBMA, TB_EVA, and matrix asphalt. In addition, the diffusion coefficient of the TBMA was increased relative to the matrix asphalt, SBS polymer further increased the diffusion coefficient, and EVA modifier had an inhibitory effect, which was related to the viscoelasticity and mechanical performance of the material. Besides, the diffusion coefficient enhancement effect of the SBS modifier on the TBMA was greater than the inhibition effect, which mainly derived from the enhancement of the diffusion coefficient of lightweight components in significantly enhancing the self-healing ability the TBMA. From microscopic and macroscopic scales, the shear-fatigue healing tests showed excellent correlation with the simulation results, demonstrating that molecular dynamics can be used to model the self-healing process of asphalt.