Influence of Surface Modification of Red Mud on the Antiaging Properties of Styrene-Butadiene-Styrene Modified Bitumen

ABSTRACT Styrene-butadiene-styrene (SBS) copolymer is widely used to modify bitumen due to its excellent temperature sensitivity. However, exposure to light, heat, and oxygen can degrade the physical and rheological properties of SBS modified bitumen (SBSMB), leading to aging behavior. Red mud (RM), an industrial waste, can enhances the aging resistance of bitumen. However, its poor compatibility with bitumen limits this improvement. This article explored the effect of organic RM on the physical properties, rheological properties, and the aging resistance of SBSMB. Four organic RMs were produced by different types of acid and coupling agent and then were doped with bitumen to prepare different RM composites of SBSMB. Different types of RM were characterized by field emission scanning microscope and nitrogen gas adsorption-desorption system. The high-temperature storage stability, physical and rheological properties, and aging resistance of all SBSMB samples were tested. Meanwhile, the functional group changes of unaged samples and aged samples were tested by Fourier transform infrared spectroscopy, and the butadiene index and sulfoxide index were applied to assess the aging resistance of SBSMB. The results show that after surface modification, the agglomeration phenomenon of RM is weakened, and the particle size of the particles becomes smaller and exhibits hydrophobic properties, which can be more uniformly dispersed in SBSMB. The addition of RM improved the high-temperature properties of SBSMB but negatively affected the low-temperature properties. Moreover, the incorporation of RM effectively improves the thermal-oxidative aging and ultraviolet aging resistance of SBSMB. After surface modification, RM further amplifies the improvement of the high-temperature properties and aging resistance of SBSMB while reducing the negative effect on low-temperature properties. Among them, SBSMB had the most excellent antiaging properties when RM treated with oxalic acid and titanate coupling agent is added.