Microscopic self-healing of multi-walled carbon nanotube-modified asphalt based on the dual diffusion-energy theory

To investigate the self-healing performance of multi-walled carbon nanotube-modified asphalt and its influencing mechanism, the asphalt molecular self-healing models were established by the molecular dynamics method. The results were analyzed based on molecular diffusion theory and surface energy repair theory. Based on the Arrhenius model, two theories were combined, and a new index healing factor was proposed to evaluate the self-healing performance by considering the diffusion characteristics and energy changes of asphalt molecules. The results show that multi-walled carbon nanotubes can accelerate the diffusion behavior of molecules in the temperature of 278--318 K to improve the self-healing properties of asphalt. Based on the proposed surface free energy equation, the self-healing properties are reasonably evaluated; the enthalpy change can be used as an index for judging the self-healing performance. The transformation model of the diffusion coefficient and cohesive work and the new index can reflect the self-healing performance more comprehensively.