Fracture investigation of asphalt mixtures containing reclaimed asphalt pavement using an equivalent energy approach

Asphalt concrete is linear-elastic at low temperatures and visco-elastic-plastic at intermediate temperatures. Stress intensity factor (K-IC) is generally used to evaluate the fracture performance at low temperatures; while the energy release rate, J-integral, could be employed at intermediate temperatures. Based on energy approach, this study adopted an equivalent stress intensity factor (K*(IC)) to evaluate the fracture toughness of asphalt concretes from low to intermediate temperatures. Semi-circular bending (SCB) tests were conducted on specimens incorporated with five different content of reclaimed asphalt pavement (RAP) (0%, 25%, 50%, 75% and 100%). Specimens with 100% RAP and rejuvenator were also prepared to explore the impact of rejuvenator. At -10 and 0 degrees C, stress intensity factor (K-IC) and fracture energy (G(F)) were measured. G(F) refers to the work of fracture divided by the ligament area. At 25 degrees C, J-integral and K*(IC) were calculated. Test results indicate that at -10 and 0 degrees C, both K-IC and G(F) decreased remarkably with the content increase of RAP. K(IC)s at 0 degrees C were lower than those at -10 degrees C; while G(F)s at 0 degrees C were larger than those at -10 degrees C. At 25 degrees C, as the content of RAP increased, both J-integral and K*(IC) increased, indicating RAP enhances the fracture performance at the intermediate temperature. The results also demonstrate that the equivalent stress intensity factor criterion can be used to evaluate the low-intermediate temperature fracture potentials of asphalt concretes. Rejuvenator was proved to be effective in enhancing the fracture resistance at both low and intermediate temperatures.