Finite element simulation of crack propagation behaviour of warm-mix steel slag crumb rubber-modified asphalt mixture

A finite element model was developed to simulate the indirect tensile (IDT) test of a warm-mix steel slag crumb rubber-modified asphalt mixture (CR-WSAM). The simulations were performed under conditions consistent with indoor IDT tests and validated against experimental results. The finite element analysis effectively captured the crack formation process in CR-WSAM, including crack initiation, propagation, and penetration behaviours, achieving the objective of analyzing crack propagation from a mesoscopic structural perspective. Furthermore, IDT models incorporating different aggregate types and void ratios were constructed to explore the mesoscopic mechanisms by which variations in interface transition zones and void ratios influence crack propagation. The results demonstrate minimal discrepancies between the indoor test results and the simulation outcomes, validating the model's reliability. As cracks expand within the asphalt mortar-aggregate interface region, an inflection point occurs, leading to crack extension into the asphalt mortar. When the specimens in the interfacial transition zone of circular and elliptical aggregates fail, a large amount of aggregate debonding occurs, and a high proportion of cracks form within the asphalt mortar. In specimens with irregular aggregate interface transition zones, cracks appeared later and propagated more slowly. Cracks always propagate towards weak areas where voids are present, and an increase in the void ratio reduces the peak load, failure displacement, and energy consumption of CR-WSAM. Among the factors influencing crack propagation, voids substantially impact CR-WSAM cracking behaviour more than either the asphalt mortar or the asphalt mortar-aggregate interface.