RESEARCH ON REFLECTION CRACKING CHARACTERISTICS OF WARM-MIX RECYCLED ASPHALT MORTAR UNDER THE EFFECT OF FREEZE-THAW CYCLES

The reflection cracking behavior of warm-mix recycled asphalt mortar (WRAM) under freeze-thaw cycles was investigated using a combination of the overlay test and digital image correlation (DIC) technology. Based on the crack images of specimens, the average crack growth rate (V) was proposed as an index to characterize the macroscopic reflection cracking behavior of WRAM. Additionally, the correlation between V and temperature, salt-solution concentration, and freeze-thaw cycles was analyzed. A meso-index cracking damage factor (DA) was proposed based on the vertical strain (Eyy), considering the effects of the salt-solution concentration and freeze-thaw cycles. The results indicate that with the progression of freeze-thaw cycles, both V and DA of WRAM specimens exhibit an increasing trend, and V increases as the temperature decreases. V is an effective index for characterizing the macroscopic reflection cracking behavior of WRAM and is strongly correlated with temperature, salt-solution concentration, and freeze-thaw cycles. DA effectively reflects the cracking damage due to WRAM reflection cracks after freeze-thaw cycles. V and DA are recommended as comprehensive indices for evaluating the reflective cracking behavior of asphalt mortar from both macro and micro perspectives.