Effect of nano-reduced graphene oxide (NRGO) on long-term fracture behavior of Warm Mix Asphalt (WMA)

•The long-term performance of WMA and modified WMA mixtures under 3FTC and AP conditions were evaluated.•The effect of NRGO on the fracture behavior of WMA at low and intermediate temperatures was evaluated.•The effect of crack type, i.e. vertical or angular cracks, on the fracture behavior of WMA and modified WMA mixture was evaluated.•The addition of 0.6% and 0.3% NRGO improved the fracture behavior of WMA at low and intermediate temperatures.•Applying 3FTC was suggested to estimate the long-term performance of asphalt mixture (instead of AP). Recent studies have shown that in addition to ambient temperature, time-dependent factors such as temperature cycles and freeze–thaw cycles (FTCs) affect the speed of creation and growth of low-temperature cracks (LTCs) and intermediate-temperature cracks (ITCs) by creating the aging process in the asphalt mixture. Therefore, it is necessary to study the cracking behavior of asphalt mixtures by considering these factors. In the present study, an attempt was made to evaluate the long-term fracture behavior of Warm Mix Asphalt (WMA) modified with nano-reduced graphene oxide (NRGO) containing vertical and angular cracks under mode I loading conditions at low and intermediate temperatures using Semi-circular bend (SCB) geometry. In order to simulate long-term performance, two conditions of 3 FTC and aging process (for 6 days) were applied to the mixtures with and without NRGO, and the results were compared with samples subjected to 0 FTC (short-term performance). The results showed that adding 0.3% and 0.6% NRGO to the WMA mixture increased fracture toughness (KIC), fracture energy (GF), and stiffness under mode I at low and intermediate temperatures. At +15 °C and for the geometry containing the vertical crack, the NRGO-modified WMA mixture had better flexibility under 3 FTC than 0 FTC; while, the flexibility of the NRGO-modified WMA mixture decreased under aging process. For geometry containing angular crack, flexibility indices improved for NRGO-containing mixtures under 3 FTC and aging process (at +15 °C temperature). On the other hand, the results showed that the addition of NRGO to the WMA mixture, while increasing the maximum load at the moment of fracture, caused a decrease in the displacement at the fractured moment at low and intermediate temperatures. This result was obtained for the mixtures that were conditioned under aging process. However, the results showed that applying 3 FTCs decreased the maximum loa