Research on anti-aging properties of POE/SBS compound-modified asphalt in high-altitude regions

Styrene butadiene styrene (SBS)-modified asphalt ages prematurely in high-altitude regions, affecting the durability of asphalt pavement. To improve the anti-ageing properties of SBS-modified asphalt and delay the degradation of SBS in asphalt, polyolefin elastomer (POE), which has good resistance to oxygen, heat and UV, was added to SBS-modified asphalt for compound modification. The optimum dose of POE/SBS compound modification was selected by a rotating thin film oven (RTFOT) test and the asphalt samples were aged by two long-term ageing experiments (laboratory-simulated high-altitude ageing (SHA) and pressure ageing vessel (PAV)). Then the performance of asphalt before and after ageing was analysed through physical tests and rheological performance tests. In the mechanism analysis, the phase distribution and micromorphology of asphalt were analysed using fluorescence microscopy (FM) and atomic force microscopy (AFM). The changes in the four components, functional groups and relative molecular weight of asphalt were described using an asphalt chemical component test (four component method), Fourier transform infrared spectroscopy (FTIR) and gel permeation chromatography (GPC), respectively. Results showed that the optimum dose of POE/SBS compound modification was 3 % POE + 4 % SBS. The anti-aging properties of POE/SBS compound modified asphalt were better than those of SBS modified asphalt and the POE/SBS compound-modified asphalt possessed excellent high-temperature stability. The dispersibility of SBS in compound-modified asphalt was improved, and the excellent anti-ageing performance of POE phase in the compound system slowed down the degradation of the SBS phase. No new functional groups were produced when POE was added to asphalt before and after ageing. In the short-term ageing, the volatilization of light components and the agglomeration of small molecules play an important role, while the degradation of modifiers dominates in the simulated ageing process. During the simulated high-altitude ageing, the weight-average molecular weight generated by POE/SBS-modified asphalt was less than that of matrix asphalt, and POE/SBS compound-modified asphalt possessed good anti-UV ageing properties.