Evaluation of the effect of loading rate of Semicircular Bending test on different fracture mechanical parameters of asphalt mixtures at intermediate temperature

Asphalt pavement cracking is one of the most common pavement failures that can be caused by fatigue and aging of asphalt mixtures under environmental conditions and traffic loads, causing other damage to asphalt pavements. For this reason, investigation of fracture behavior and precise evaluation of mechanical fracture parameters of asphalt mixtures and its effective parameters can assist pavement engineers in designing and constructing high-quality pavements. In this study, semicircular bending specimens (SCB) were used to evaluate the impact of experimental loading rates on different fracture mechanics parameters of asphalt mixtures at intermediate temperatures (25 ° C). The main objective of this study was to determine the most appropriate loading rate for SCB testing at an intermediate temperature, taking into account the coefficient of variation of the test and with specimens with geometrical characteristics of diameter and thickness, 15 and 3 cm and crack length equal to 18 mm. For this purpose, SCB samples were subjected to loading rates of 0.5, 1, 3, 5, 20, and 50 mm / min and Peak Load parameters for cracking of asphalt samples (PL), Fracture Energy of asphalt samples (FE). Flexibility Index (FI) and Cracking Resistance Index (CRI) were evaluated. The results showed that as the loading rate increased, the amount of PL and FE for the asphalt mix failure always increased, but FI and CRI did not show a significant increase with the loading rate. Based on the results of the experiments and evaluation of the coefficient of variation (COV) of the parameters mentioned, loading rates of 3 and 5 mm / min are recommended for use in the SCB test.