Investigation of the Asphalt Self-Healing Mechanism Using a Phase-Field Model

The self-healing mechanism of asphalt has always been a challenging issue for pavement engineers; up to now there is no general agreement on the fundamental mechanism. In this paper, combined with atomic force microscopy (AFM) technology, the self-healing mechanism of asphalt is simulated by using the phase-field model in two ways: thermodynamic approach and mechanical approach. In the thermodynamic approach, self-healing is considered as a material-phase-rearrangement process. Microcracks will form and disappear in the stress concentration zone near the phase interfaces because of phase separation, which is demonstrated by AFM results. In the mechanical approach, the microstructure is described using a phase-field variable that assumes a positive field in the intact solid and negative one in the existing crack void. Allen-Cahn dynamics are adopted to evolve the phase-field variable that the surface energy will result in the wetting of two surfaces and finally leads to self-healing. By using both approaches, one can better understand the asphalt self-healing mechanism.