Abstract: Semi-circular bending (SCB) fracture tests on asphalt concrete were conducted in this study, and load-crack opening displacement curves of its crack propagation process were obtained. We examine the effects of temperature, loading rate, and initial crack length on its initial fracture toughness, using the steep drop method of linear correlation coefficients; a digital image correlation method was used to study its damage and deformation characteristics at the stages of crack initiation and crack propagation. Research findings show that at the damage position, the initial cracking load obtained using this steep drop method is within the ranges of experimental load, verifying the rationality of the method in studying the initial fracture toughness. This toughness decreases gradually with the temperature and initial crack length, while increases with the loading rate.

Key words: asphalt concrete, initial fracture toughness, digital image correlation method, crack propagation, initial cracking load