Impact of a Novel Zinc Oxide/Red Mud Composite Material Dosage on Bitumen Aging Resistance

With the effects of heat, oxygen and light, bitumen pavements will experience thermal-oxidative and ultraviolet (UV) aging, which can lead to a reduction in the service life of pavement. With the aim of enhancing the aging resistance of bitumen, the zinc oxide/red mud composite material (ZnO/RM) was synthesized using hydrolytic precipitation method. The microstructure and elemental distribution of ZnO/RM were characterized by field emission scanning electron microscopy and energy dispersive spectrometry. The effects of different ZnO/RM dosages on high- and low-temperature performance and storage stability of bitumen were examined. Moreover, this study is the first to systematically investigate the optimal dosage of ZnO/RM for multimode aging of bitumen. The aging degree of bitumen was characterized based on physical and rheological aging indexes, changes in chemical functional groups and molecular weight distribution. The results indicated that ZnO was successfully loaded to RM with a uniform distribution. ZnO/RM exhibits favorable compatibility with bitumen. The ZnO/RM can enhance the high-temperature performance of bitumen, but slightly negatively affected the low-temperature crack resistance. However, all bitumen specimens exhibited the same low-temperature PG (−22 °C). The integrated evaluation of aging indicators in this study illustrates that ZnO/RM can simultaneously improve the thermal-oxidative and UV aging resistance of bitumen, with an optimal ZnO/RM dosage of 3%.