Thermoregulation, rheological properties and modification mechanism of asphalt modified with PUSSPCMs

Phase change materials (PCMs) can regulate asphalt temperature through thermal storage properties to prevent thermal damage in asphalt pavements. However, the effects of PCMs on the thermoregulation and rheological properties of asphalt require further study. In this study, polyurethane solid–solid phase change materials (PUSSPCMs) were prepared to impart thermoregulation properties to asphalt, and the effects of PUSSPCMs on the rheological properties and microscopic characterization of asphalt were investigated. The PUSSPCMs were produced by different soft segment mass fractions (70 %, 80 %, and 90 %), and they were used to prepare modified asphalt with varying contents (3 %, 5 %, and 7 %). Thermoregulation testing system, dynamic shear rheology (DSR), bending beam rheology (BBR) tests, differential scanning calorimetry (DSC), infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and atomic force microscopy (AFM) were conducted to determine the thermoregulation, rheological properties, and modification mechanism of PUSSPCM-modified asphalt, respectively. The results show that the thermoregulation property of PUSSPCM-modified asphalt improves with the increase of soft segment mass fraction and content, 7 % P90 asphalt exhibits the best thermoregulation property with the excellent delayed time (1105 s) and temperature difference (7.1 ℃). The high-temperature rutting resistance of the modified asphalt is enhanced by decreasing the soft segment mass fraction and increasing the content of PUSSPCMs, with the 7 % P70 being the best asphalt type. The 7 % P90 asphalt exhibits the optimum low-temperature creep performance due to a higher soft segment mass fraction. The modified asphalt may be a physical modification since no new characteristic peaks appear. With the increase of soft segment mass fraction, the PUSSPCMs in asphalt transform from elastomer to a ribbon-like structure. Furthermore, the microscopic roughness (S_q) and Young's modulus of the modified asphalt decline with the increase in soft segment mass fraction and content of PUSSPCMs, implying an increase in microscopic crack resistance and a decrease in elasticity.