Discrete element simulation of micro-cracking behaviour in warm-mix slag powder modified asphalt mixtures

This study employs the discrete element method (DEM) in conjunction with acoustic emission (AE) experimental data to systematically investigate the low-temperature cracking evolution behaviour of asphalt mixtures incorporating steel slag aggregates and the warm-mix additive SDYK, along with their mesoscopic mechanisms. By simulating the low-temperature loading process of a semi-circular bend (SCB) using DEM, this study captures the characteristics of bond failure, force chain reorganisation, and microcrack propagation at the granular scale, enabling a correlation analysis between the macroscopic mechanical response and micro-damage evolution. The results indicate that steel slag aggregate, owing to its high strength and rough surface characteristics, significantly enhances the force chain load-bearing capacity and optimises load transfer pathways. While the warm-mix additive SDYK improves inter-particle adhesion and structural compactness, resulting in a more continuous and uniform force chain distribution. Together, they establish a force chain system characterised by ‘strong bearing capacity—stable transmission—uniform distribution’, effectively suppressing microcrack propagation and delaying the penetration of primary cracks. Coupled AE–DEM analysis reveals a strong correlation between the sudden increase in cumulative AE energy and the accelerated bonding failure phase in the DEM. Following the incorporation of steel slag and warm-mix additives, the aforementioned critical damage stages were significantly delayed, indicating effective suppression of rapid crack propagation. This study elucidates the mechanism enhancing the low-temperature crack resistance of warm-mix steel slag polymer-modified asphalt mixtures at the micromechanical level, providing theoretical foundations for crack resistance evaluation and material optimisation design based on test-numerical coupling.