A novel approach to determine mode II fracture toughness of hot mix asphalt

Fracture behaviors of hot mix asphalt (HMA) are critical to the durability of asphalt pavement, especially at low temperatures. This study proposed a method to test the mode II fracture behaviors of HMA, which is inspired by the mode II test of cement concrete. In this method, compressive tests were conducted on two types of specimens, including the double-edged notch specimen and the cubic specimen. The shear action resulting in the mode II fracture was extracted from the energy difference between the load-displacement curves of the two types of specimens. The stress intensity factor (KII) and fracture energy (GF) were calculated from the theory of energy consumption. On the other hand, the effects of reclaimed asphalt pavement (RAP) and rejuvenator were examined on the mode II fracture performance of HMA. Meanwhile, asymmetric semi-circular bending (SCB) tests were also conducted to obtain the mode II KII and GF, which were used to verify the feasibility of the method proposed in this study. Results indicated that with the increase of RAP, KII and GF both decreased remarkably. When RAP content was 100%, KII and GF were reduced by 42.8% and 55.8%, respectively. When the rejuvenator and 75% RAP were added, the fracture performance was enhanced compared to HMA with 75% RAP only, indicating rejuvenator benefited the mode II fracture resistance. The result comparison between the double-edge notched specimens and the SCB specimens verified the feasibility of the method proposed in this study.

Automated summary

This study proposed a method to test the mode II fracture behaviors of hot mix asphalt (HMA) and examined the effects of reclaimed asphalt pavement (RAP) and rejuvenator on the mode II fracture performance of HMA. Results indicated that with the increase of RAP, the fracture performance of HMA decreased, while the use of rejuvenator benefited the mode II fracture resistance.