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.

Automated summary

Asphalt concrete exhibits different fracture behaviors at low and intermediate temperatures, with stress intensity factor (K-IC) and energy release rate (J-integral) commonly used to evaluate fracture performance. This study introduced an equivalent stress intensity factor (K*(IC)) to assess the fracture toughness of asphalt concrete at a wider temperature range. Test results indicate that the addition of reclaimed asphalt pavement (RAP) enhances fracture performance at intermediate temperatures. Furthermore, the use of a rejuvenator was found to be effective in improving fracture resistance at both low and intermediate temperatures.