Study on UV aging resistance of nano-TiO2/montmorillonite/styrene-butadiene rubber composite modified asphalt based on rheological and microscopic properties

•A matrix binder was modified to possess excellent low-temperature properties and anti-ultraviolet aging properties.•The response surface method was used to determine the dosage of modifies.•The interaction and modification mechanism of modifiers were revealed by FTIR and SEM. In order to improve the high-temperature performance and anti-ultraviolet aging performance of butadiene styrene rubber (SBR) modified asphalt, nano-TiO2 and Montmorillonite (MMT) were used for composite modification, and the test scheme was determined by Box Behnken Design (BBD). The high-speed shearing method is used to prepare nano-TiO2/MMT/SBR composite modified asphalt. Meanwhile, the dynamic shear rheometer (DSR) test and the bending beam rheometer (BBR) test were used to evaluate the rheological properties of the composite modified asphalt before and after aging to evaluate its anti-ultraviolet aging performance. Finally, the interaction and modification mechanism of the modifiers were revealed by scanning electron microscopy (SEM) and Fourier-transform infrared spectroscopy (FTIR). The results show that the optimal dosage of nano-TiO2, nano-MMT and SBR latex (solid content 60%) are 1.5%, 4%, and 6%, respectively. The synergistic effect of nano-TiO2 and nano-MMT can significantly delay the conversion process of light components to asphaltenes during asphalt aging, and makes CMI value of SBR modified asphalt significantly reduced and almost stabilized at about 2, and the average stiffness modulus change rate decreases from 0.27 to 0.13, and the carbonyl index dropped from 5.16 to 0.28. SEM test results show that nano-TiO2 particles can be used as physical cross-linking points to promote the combination of nano-MMT/SBR modifiers and asphalt, making the microstructure of nano-TiO2/MMT/SBR modified asphalt more stable and uniform. The modification of Nano-TiO2/MMT/SBR to asphalt is a physical modification process, more Si-O-Si functional groups were generated during the aging process of MMT, which further promote the formation of MMT and asphalt network structure. In conclusion, the study of nano-TiO2/MMT/SBR composite modified asphalt in this paper provided a reference for the selection of modified asphalt in cold and ultraviolet regions.