Investigation of fracture toughness and fracture process in cement asphalt mortar

Cement asphalt mortar (CAM) is primarily used in the ballastless track structures of high-speed railways, where its fracture performance is closely related to the structural serviceability. In this study, fracture behavior of CAM was investigated using the semicircular bending (SCB) test and the digital speckle correlation (DSC) method. Based on the test results, the fracture process, fracture toughness, and influencing factors of CAM with high emulsified asphalt content were analyzed. CAM exhibited ductile fracture at 25°C, and semi-ductile fracture at −15°C and 5°C. The fracture process was divided into three stages. With decreasing temperature, both the crack initiation point and the unstable propagation point shifted to later stages. The optimal emulsified asphalt content determined by the fracture toughness index was 25.7%, at which the temperature sensitivity of toughness reached its peak. A fitted correlation between fracture toughness parameters J_IC and K_IC was established.