Enhancement Effect of Aggregates on the Low-Temperature Cracking Resistance of Asphalt Mixtures

Aggregates’ configurations result in different stress fields, which change the fracture mode and mechanical properties of an asphalt mixture. To reveal the enhancing effect of aggregates with different particle sizes on the low-temperature cracking resistance of an asphalt mixture, an indirect tensile (IDT) test was carried out to analyze the aggregates’ influence on crack propagation and low-temperature cracking resistance from a macroscopic perspective. And combined with the test results, mesostructure models of an asphalt mixture with different aggregates’ spatial distributions were established through the extended finite element method (XFEM) to analyze changes in the crack propagation path and crack tip configuration force from a mesoscopic perspective. The main results showed that the crack tip configurational force was reduced due to the aggregate size increasing, demonstrating the inhibitory effect of aggregates on crack propagation. This contributes to enhancing asphalt mixtures’ low-temperature cracking resistance. Compared to single-grain aggregates, multi-grain aggregates exhibit a greater inhibitory effect on crack propagation. Nonetheless, an excessive disparity in particle sizes compromises particle continuity, leading to the formation of more branching cracks. Meanwhile, the aggregates’ inhibitory effect on crack propagation is influenced by the crack deflection angle. In particular, when the crack deflection angle, β, equals 45°, the crack tip’s configurational force is notably larger, leading the crack to enter an unstable state conducive to the expansion and formation of macrocracks. The research results reveal aggregates’ inhibitory effect on crack propagation from a macro- and microperspective and reveal the relationship between aggregate configurations and the low-temperature cracking resistance of asphalt mixtures.