Evolution of Low-Temperature Properties of Warm-Mix Rubber-Modified Asphalt under Freeze-Thaw Cycles

Confocal scanning laser microscopy (CLSM), Fourier transform infrared (FTIR) spectroscopy and differential scanning calorimetry (DSC) were performed to analyze the changes in apparent morphology, the functional groups, and glass transition temperatures of warm-mix rubber-modified asphalt under freeze-thaw cycles to describe the evolution mechanism of the low-temperature performance of asphalt binders under freeze-thaw cycling at the microscale level. Using the bending beam rheometer (BBR) test, the relaxation and delay characteristics of the asphalt binders under freeze-thaw cycling were quantitatively analyzed using the parameters fitted by Burgers model, and based on the dynamic shear rheometer (DSR) test, the low-temperature evaluation indices of the asphalt binders were calculated using the Christensen-Anderson-Marasteanu (CAM) model. Regression analysis of the related performance parameters was carried out, so as to describe the evolution of the low temperature performance of asphalt under freezing-thawing cycles at the macroscopic level. It was indicated that freeze-thaw cycling reduced the low-temperature performance of the asphalt binders. Compared to water freeze-thaw cycling, salt freeze-thaw cycling caused a greater degree of damage to the surfaces and changes in the related parameters of the asphalt binders. Also, the addition of warm-mix additives (EM and SDYK) changed the low-temperature performances of the rubber-modified asphalt (60MCR). After freeze-thaw cycling, the rubber-modified asphalt with SDYK (0.6S-60MCR) showed lower degrees of change of characteristics describing low temperature performance than those of the rubber-modified asphalt (60MCR) and rubber-modified asphalt with EM additive (1E-60MCR), indicating its superior resistance to anti-cracking ability at low temperatures.