Effects of Anhydrous Calcium Sulfate Whisker and Waste Engine Oil on Performance of Asphalt Binder and Its Mixture

Abstract

Phosphogypsum is a solid waste generated when phosphate rock is wet treated with sulfuric acid during the production of phosphate fertilizers. It has been found that the improper handling and disposal of phosphogypsum can cause severe environmental harm. To promote sustainable development, anhydrous calcium sulfate whiskers (ACSWs) prepared from phosphogypsum have been proposed as an environmentally friendly asphalt modifier. This study investigated the effects of using ACSW and waste engine oil (WEO) as modifiers in hot mix asphalt (HMA). Various asphalts modified with ACSW and WEO were prepared, and their physical and rheological behaviors were systematically investigated. Results showed that incorporating ACSW into the asphalt binder considerably improved its high-temperature performance, but significantly weakened its low-temperature performance. However, the low-temperature performance degradation was compensated for by incorporating WEO, with a 5% ACSW to 2% WEO ratio being the optimal combination. Similarly, the pavement performance tests demonstrated that the HMA modified with 5% ACSW and 2% WEO considerably improved high-temperature antirutting deformation, low-temperature anticracking, and moisture stability. Moreover, the results from Fourier transform infrared spectroscopy showed that the ACSW-and-WEO-modified asphalt underwent only a physical reaction. Finally, a heavy metal leaching test was conducted to confirm that the ACSW-and-WEO-modified asphalt binder, as an environmentally friendly pavement material, was not hazardous to the environment. The findings of this study promote sustainable resource utilization and waste management in pavement engineering.