Evaluation of long-term fracture behavior of hot mix asphalt modified with Nano reduced graphene oxide (RGO) under freeze-thaw damage and aging conditions

Asphalt mixtures suffer from different types of cracking such as low-temperature cracks (LTCs) and intermediate -temperature cracks (ITCs). These two types of cracking may occur in the short-or long-term due to conditions such as temperature cycles, freeze-thaw cycles (FTC), and the aging process. Therefore, it is necessary to investigate the effect of these factors on the fracture behavior of LTC and ITC. This study was used the fracture mechanics method to evaluate the short-term and long-term fracture behavior of hot mix asphalt (HMA) con-taining Nano reduced graphene oxide (RGO) under mode I loading conditions. To this purpose, the geometries of symmetric specimen SCB and classical-modified specimen SCB-2 containing vertical and angular cracks were selected. In order to simulate short-term fracture behavior, the SCB samples were subjected to 0 FTC (un-con-dition) and to simulate long-term behavior, the SCB samples were subjected to 3 FTC and long-term aging (LTA) process. The results showed that the Nano RGO additive enhanced the fracture resistance of the HMA mixture containing vertical and angular cracks at temperatures of + 15 and-15 degrees C by increasing the fracture energy and fracture toughness indices. Also, the results showed that by increasing the stiffness of the HMA mixture, the additive increased the resistance against elastic deformations. Compared to the LTA process, the application of 3 FTCs to the HMA mixture (with and without Nano RGO), by reducing Pmax and increasing the amount of displacement at the moment of fracture, caused a decrease in the stiffness of the samples (at temperatures of + 15 and-15 degrees C). For mixtures with and without Nano RGO that were subjected to the LTA process, the increase in stiffness resulted from the increase in Pmax and the decrease in displacement at the moment of fracture (at temperatures of + 15 and-15 degrees C). Finally, the results showed that the application of 3 FTCs had the greatest impact on reducing fracture indices such as KIC , GF , and Pmax at temperatures of + 15 and-15 degrees C (for HMA and Nano RGO modified HMA mixtures). This result indicated the importance of using 3 FTC instead of LTA to simulate 12 years of damage on asphalt pavement.