Energy evolution in fracture process of hot mix asphalt containing reclaimed asphalt pavement and rejuvenator

Abstract

The fracture of hot mix asphalt (HMA) is accompanied by the energy absorption and release. Energy includes the dissipated energy (Ud), elastic strain energy (Ue) and post crack energy (Up). The dissipated energy is closely related to the plastic behavior, while the elastic strain energy is related to the reversable deformation. This study established a framework to analyze the energy evolution by investigating Ud, Ue and Up within the semi-circular bending (SCB) test. The development of Ud, Ue and Up was explored considering the whole fracture process from the low to the intermediate temperature for specimens with different content of reclaimed asphalt pavement (RAP). Three temperatures, −10 °C, 0 °C and 25 °C, were selected in the SCB test. Reclaimed asphalt pavement (RAP) with the content from 0% to 100% was incorporated to reveal the impact of RAP on the energy evolution during the fracture process. Rejuvenator was added to present the possible benefit in enhancing the resistance to fracture. Meanwhile, a brittleness parameter (BI) considering these energy parameters were proposed to show the effect of RAP on the brittleness of HMA. Results indicated that at −10 °C and 0 °C, a low content of RAP (25%) could generate positive effect on fracture resistance in terms of fractur energy. At 25 °C, fracture energy increased with the increase of RAP content, and the optimum RAP content was 75%, at which the fracture energy reached to the maximum value. At −10 °C and 0 °C, the total energy and Ue both increased with a high rate, and the magnitude of Ud was relatively small. The inclusion of 75% RAP made the increase of Ud more obvious than the specimens without the addition of RAP. No matter for mixtures with 0 or 75% RAP, Ue decreased quickly after the peak load and Ud increased sharply and was almost consistent with the total energy, indicating the quick failure after the peak load. At 25 °C, after the peak load, the total energy and Ud still increased with very high rates, indicating significant plastic deformations were induced due to the increase of temperature. From −10 °C to 25 °C, rejuvenator presented positive effect on enhancing the fracture resistance. The enhancement was mainly due to the improvement of the dissipated energy and the post-peak energy. RAP could apparently increase the brittleness index (BI), and rejuvenator could decrease BI due to the softening behavior.