Influence of crack configurations of asphalt mortar on the loading response characteristics of cracks under low-temperature conditions

Asphalt mortar is the base material used in asphalt concrete, and its mechanical properties directly affect those of the prepared asphalt concrete. An analysis of the loading response characteristics of cracks in asphalt mortar under low-temperature conditions can help reveal the interaction effect of multiple cracks in asphalt concrete and the influence mechanism of aggregates on the crack propagation and evolution behaviors. In this study, various forms of pre-cracks were generated in asphalt mortar specimens using the water jet cutting technology. Combined with the discrete element method (DEM), an indirect tensile (IDT) test and a virtual IDT test were conducted to analyze the effects of the crack deflection angle (beta) and crack length (r) on the crack propagation behavior from macro- and meso-perspectives. The main results showed that: (1) Changes in the crack shape parameters (beta and r) not only induced multiple branch cracks in the asphalt mortar but also led to the development of II Mode fractures; (2) With the increase in the crack shape parameters, the low-temperature crack resistance of the asphalt mortar decreased, with beta having a greater effect on the crack propagation behavior than r; (3) At the mesoscale, with the increase in the crack shape parameters, there was a gradual transformation of the fracture mode from I Mode to II Mode, and the crack propagation process accelerated, resulting in a significant decrease in the low-temperature crack resistance at the macroscale. The research results establish a theoretical foundation for revealing the characteristics of multi-crack propagation in asphalt concrete under environmental influences, and offer technical support for pavement crack repair and maintenance.