Investigation of Factors Affecting the Intermediate-Temperature Cracking Resistance of In-Situ Asphalt Mixtures Based on Semi-Circular Bending Test

Cracking is one of the main distresses in asphalt pavement. At present, few studies have been conducted on the cracking performance of asphalt mixtures from the field due to the difficulty of sample collection. Therefore, this study aims to assess the cracking resistance of in-service asphalt pavement at intermediate temperature using a large number of field cores in Jiangsu province, China. A semi-circular bending (SCB) test at 25 °C was conducted on field-cored samples covering three asphalt layers from 16 in-service road sections that represent a combination of influencing factors, including air void, mixture type, service age, cumulative number of equivalent single-axle loads (ESALs), and overload rate. The flexibility index (FI) and tensile strength were calculated from the experimental data as cracking performance evaluation indices. According to the analysis of variance results, at the top layer, ESALs and service age had a strong influence on cracking resistance. The decline rate of FI became slower with increasing ESALs. The most rapid decline in crack resistance with service age occurred on medium-traffic-level sections that served for over 14 years. At the middle layer, the overload rate replaced service age as a significant factor for FI. At the bottom layer, the air void was the only significant factor affecting the cracking resistance. In general, as the depth of layer increased, the effect of traffic load and service age decreased, whereas the effect of material properties increased. In addition, the FI and tensile strength were more sensitive to traffic load and air void, respectively.