Insights into multiscale low temperature fracture mechanisms of steel slag asphalt mixtures via peridynamics

Due to the porous characteristics and asphalt absorption capacity of steel slags, the low-temperature crack resistance of steel slag asphalt mixtures (SAM) is compromised, and the fracture mechanisms of SAM remain unclear. Therefore, single particle crushing tests and three-point bending (TPB) tests were conducted in this study, along with the corresponding peridynamic simulations, to reveal the fracture mechanisms at both the particle and specimen scales. The results show that peridynamics demonstrates robustness in simulations at both scales. At the particle scale, the single particle crushing strength of steel slag aggregates follows a Weibull distribution, with a characteristic strength σ₀ = 15.7 MPa and a Weibull modulus m = 1.9380, indicating sufficient resistance to crushing. The pores in the steel slags act as weak points, allowing cracks to propagate through them and resulting in fragments of varying shapes and sizes. At the specimen scale, the optimized SAM demonstrates exceptional low-temperature crack resistance even with a coarse aggregate replacement ratio of 100 %. The mixtures achieve an average breaking strain of 2959.8 με, significantly surpassing standard requirements. During the damage and fracture process of the SAM, stress concentration around the steel slag pores markedly influences the crack paths. Although the ineffective asphalt absorbed into the steel slag aggregates sustains part of the stresses, delaying the crushing of the steel slag aggregates, the cracks still propagate along the interfaces between the ineffective asphalt and the steel slag aggregates and ultimately penetrate through the specimens along the pores of the steel slag aggregates.