Stiffness, fatigue and cracking performance of porous asphalt concrete under varying freeze-thaw cycles

This study seeks to comprehensively analyze the deterioration behavior of porous asphalt concrete (PAC) under freeze-thaw cycle (FTC) tests, as well as develop a fatigue prediction model and service life estimation method. In this regards, using asphalt concrete (AC) as a control group, dynamic modulus (DM), indirect tensile creep (ITC), semi-circular bending (SCB), and splitting tensile (ST) tests were performed on PAC to examine the deterioration of mechanical properties. Further, semi-circular bending fatigue (SCBF) tests were performed to examine the fatigue performance. The FTCs exerted minimal differences (approximately 1 %) in the dynamic modulus master curves of AC, on the other hand, PAC showed an average decrease of 5 %. Further, both PAC and AC exhibited an increase in creep stiffness with time, with a significant acceleration after 1000 s. With the increase in the number of FTC, the reduction rate of fracture energy of PAC diminished from 3.57 % to 39.88 %, while AC diminished from 30.57 % to 74.69 %. The highest reduction effect in fracture toughness occurred when the number of FTCs rose from 15 to 19 times for the two types of asphalt mixtures, while the rate of decline of the PAC was 3.8 times that of the AC. The cracking performance of PAC was significantly reduced after three cycles, and when the number of FTCs was below 11 times, the fatigue life exhibited a more rapid diminishment. Based on the results, the proposed fatigue prediction model projected that, following 23 FTCs, the fatigue life of PAC was approximately 1701 cycles at a 0.3 stress ratio and 962 cycles at a 0.4 stress ratio. Overall, PAC exhibited greater performance deterioration than AC, though AC exhibited a more significant impact on low-temperature cracking resistance. This study systematically examines the performance of PAC under FTCs, providing novel perspectives on the long-term resilience of asphalt mixtures in cold regions.