Preparation and characterization of binary eutectic phase change material laden with thermal conductivity enhancer for cooling steel slag asphalt pavement

The active asphalt pavement cooling strategy using phase change material (PCM) is crucial for mitigating urban heat island impacts and reducing high-temperature rutting distress. However, most PCM-incorporated pavements use single pure PCM for temperature regulation, resulting in either a discrepancy between phase change temperature and pavement rutting sensitive temperature or a low phase change enthalpy. Moreover, their unacceptable low thermal conductivity can dramatically lower the PCM thermal performance in cooing asphalt pavements. This study aimed to develop a novel PCM-incorporated cooling asphalt pavement, which consists of a binary eutectic mixture of fatty acid PCMs (palmitic acid (PA) and stearic acid (SA)), a supporting material (waste steel slag aggregate (SSA)), and a thermal conductivity enhancer (TCE, Nano Al2O3). The PCM composite of PA-SA was screened out first based on a binary eutectic system. The composite phase change steel slag aggregate (CPC-SSA) and the TCE-based CPC-SSA asphalt mixture were then designed and developed with three types of TCEs. The performance tests were finally conducted to examine the thermal and rutting resistance performance of the PCM-incorporated asphalt pavement. The test results showed that the pavement incorporated with the PCM composite of PA-SA and Nano Al2O3 is capable of effectively cooling asphalt pavement and alleviating its high-temperature rutting distress. The findings of this study are expected to promote sustainable resource utilization and cooling strategies developed for the mitigation of high pavement temperature distresses and urban heat island impacts.