Pure modes I and II fracture behavior of Modified-Hot mix asphalt (HMA) under Long-Term aging condition

Abstract

Top-down crack (TDC) as one of the pavement distresses, has a significant contribution to the quality of pavement service. Low-temperature top-down crack, which are subcategories of low-temperature crack (LTC) is representative of the cracks located on the pavement's surface and are directly affected by different environmental conditions such as temperature, air (oxygen), and light. Therefore, in the pavement body, this type of crack is more affected by long-term aging (LTA) than other cracks. To make sustainable mixtures, this research, it was tried to assess the long- and short-term fracture performance of hot mix asphalt (HMA) and HMA reinforced with different percentages of hospital waste pyrolysis carbon black (HWPCB) and hospital waste pyrolysis hydrocarbon (HWPHC) under mode I and II. The symmetrical specimen SCB and modified specimen SCB-2 geometries are utilized to simulate pavement crack behavior under tensile (opening) deformation and shear (sliding) deformations, respectively. For simulating the cracking behavior of semi-circular bending (SCB) samples in the laboratory with the pavement cracking behavior under the LTA process, an LTA condition, which was equivalent to a 12-year failure, was applied. Then, the long- and short-term fracture performance of the samples was examined using different fracture indices at temperatures of −15 °C. The results revealed that adding HWPCB and HWPHC to the HMA sample improved the fracture energy (GIIF and GIF) and fracture toughness (KIIC and KIC) of the HMA mixture under modes II and I (at −15 °C). Also, the improvement of the fracture stiffness and reduction of fracture brittleness of HMA specimens reinforced with HWPCB and HWPHC was concluded in long- and short-term conditions at the studied temperature (under modes II and I). From an operational point of view, the HMA mixtures reinforced with lower percentages of HWPCB and HWPHC are recommended for use in areas with an average temperature of about −15 °C and medium-heavy vehicle volumes. Also, the HMA mixtures reinforced with higher percentages of HWPCB and HWPHC are recommended for use in areas with medium temperatures and medium-heavy vehicle volumes. Moreover, the mixture containing both additives (HWPCB + HWPHC) is recommended for areas with medium temperature and high heavy vehicle volumes.