FTIR and rheology analysis of aging on different ultraviolet absorber modified bitumens

Three different kinds of ultraviolet absorbers (UVAs), including octabenzone, bumetrizole and tinuvin770, were used to modify the road bitumen. The base and UVA modified bitumens were aged by the thin film oven test (TFOT), pressurized aging vessel (PAV) and ultraviolet (UV) aging. The Fourier transform infrared (FTIR) spectroscopy was applied to investigate the chemical structures of the UVA modified bitumens. Several structural indexes based on the FTIR results were defined to evaluate the aging extent of the binders. Finally, the rheological properties of the UVA modified bitumens were tested in order to confirm the validity of the FTIR analysis. Results show that the UVAs have little influence on the branched aliphatic structure of bitumen, but increase the aromatic structure of bitumen. The thermal- and photo-oxidative aging of the bitumen can be restrained by the three UVAs since the reactions of chain scission, polycondensation and oxidation of the bitumen are slowed down by the UVAs during aging. Among the three UVAs, the tinuvin770 exhibits the most significant improvement on the thermal- and photo-oxidative aging resistance of bitumen.