Coupled Navier–Stokes Phase-Field Model to Evaluate the Microscopic Phase Separation in Asphalt Binder under Thermal Loading

The evolution of asphalt microstructures under thermal loading has always been a critical issue for pavement engineers. Previous researches show that phase separation will greatly affect the mechanical performance of asphalt at microscale. To analyze this important phenomenon, the conserved phase-field model is coupled with the Navier–Stokes equation to simulate the phase kinetics in this paper. The asphalt is chemically simplified to a quaternary system consisting of four chemical components: asphaltene, resin, oil, and wax. The coupled Navier–Stokes phase-field system is solved in a unified finite element framework in COMSOL software. It is observed that phase separation has a significant influence on the thermal stress distribution. Moreover, stress concentration is observed at the interfaces between different phases, which may result in microcracks. This conclusion is validated by atomic-force microscopy (AFM) experiment results.