Synthesis of Hydrotalcite from Phosphate Tailings and Its Effect on the Anti-Ultraviolet Aging Properties of Asphalt Binder

Abstract

Ultraviolet (UV) aging can cause serious degradation of asphalt performance and shorten the service life of asphalt pavement. In this research, a kind of layered ultraviolet reflective material Ca/Mg/Al layered dihydroxyl metal hydroxides (Ca/Mg/Al-LDHs) was prepared from phosphorus tailings by the acid hydrolysis, purification, coprecipitation, and hydrothermal method (APCH) and used to enhance the anti-UV aging performance of asphalt binder. The synthesis condition of Ca/Mg/Al-LDHs was optimized according to the UV reflectivity of the hydrotalcite prepared and their effects on the physical and antiaging properties of asphalt binder were investigated. Organic surface modifier (KH560) was used to modify the Ca/Mg/Al-LDHs to improve their compatibility with asphalt. The results show that Ca/Mg/Al-LDHs can be prepared from phosphorus tailings by the APCH method. The optimal molar ratio of divalent ions to trivalent ions to produce Ca/Mg/Al-LDHs was 2, and the optimal pH was 10. The Ca/Mg/Al-LDHs achieves 94.1% of the UV light reflectance of commercial LDHs. The Ca/Mg/Al-LDHs could reflect 65%–83% of UV light from 280 to 400 nm. The surface modification can improve the compatibility of LDHs with asphalt and the anti-UV aging performance of LDHs-modified asphalt. The Ca/Mg/Al-LDHs prepared from phosphate tailings improved the anti-UV aging performance of asphalt; they have a similar anti-UV aging effect on asphalt binder as commercial LDHs.