Evaluation of Low-Temperature Cracking Properties of Asphalt Mixtures Containing RAP and Sasobit Using the SCB Test

Low-temperature cracking is one of the major failures of asphalt surfaces, and is considered as a performance indicator in the mechanistic-empirical design method. Fracture toughness and fracture energy are important parameters for investigating the low-temperature cracking of asphalt concrete. The purpose of this study is to explore the low-temperature fracture parameters of asphalt mixtures containing the recycled asphalt pavement (RAP) and the warm mix asphalt (WMA) additive namely, Sasobit using the semicircular bending (SCB) test. For this purpose, the SCB test is carried out at 0 °C under the load line displacement (LLD) controlled mode. The eight superpave-designed asphalt concretes including hot mix asphalt (HMA), Sasobit-modified asphalt concrete (WMA), HMA containing RAP (HRAP), and WMA containing RAP (WRAP), were prepared with two nominal maximum aggregate sizes of 9.5 and 19 millimeters. The recycled asphalt mixtures (both HRAP and WRAP) showed a sudden and brittle failure, while in the case of HMA and WMA mixtures, the failure was more ductile. The fracture toughness of the RAP mixtures was higher than the other ones (about 100% of mixtures without RAP).  Based on the fracture energy parameter, the recycled asphalt mixtures (HRAP and WRAP) had a better low-temperature cracking performance, in addition to the environmental and economic benefits. The coarse-grained WRAP mixtures showed an increase of about 22% in the fracture energy, followed by the fine-grained WRAP mixture (about 15%), and the coarse-grained HRAP mixture (about 12%). The cracking severity of the RAP mixtures was lower than the RAP-free mixtures (between 25% to 84% of the corresponding RAP-free mixtures)