Low-temperature cracking mechanism of hydraulic asphalt concrete: Insights from fracture phase-field modeling

To elucidate the low-temperature cracking mechanism of hydraulic asphalt concrete (HAC), this study, for the first time, employed the phase-field method to investigate its thermal cracking behavior at the mesoscale. Initially, thermal stress restrained specimen tests (TSRST) were conducted on HAC specimens, followed by numerical simulations of the thermal cracking behavior using a thermo-mechanical coupled phase-field model. The results indicated that micro-damage initiated near the critical temperature (-25℃), mainly concentrated at sharp corners of coarse aggregates and within interfacial transition zones (ITZs). The phase-field variable ϕ exhibited a sharp increase from 0.43 to 1.0, and the displacement jumps from 0.07 mm to 0.29 mm, resulting in instantaneous fracture of the specimen. The findings demonstrated that the ITZ significantly influences the low-temperature cracking resistance of HAC, and that the transition temperature (-25℃) can serve as a threshold indicator for crack initiation. Furthermore, the critical temperature, transition temperature, and the slope at the terminal phase of the temperature–stress curve are proposed as key indicators for evaluating HAC's resistance to low-temperature cracking. This study provides novel mechanistic insights and offers both theoretical and numerical foundations for enhancing the macroscopic performance and durability of asphalt concrete facing dams.