Evaluation of phosphorus slag (PS) content and particle size on the performance modification effect of asphalt

•The interaction between PSP and asphalt was mainly physical blending.•PSP was more sensitive to aged asphalt but less sensitive to original asphalt.•The increase of PSP content increased the shear complex modulus of PSMA.•The increase of the specific surface area of PSP provided better modification effect. To evaluate the modification effect of phosphorus slag powder (PSP) on the rheological performance of asphalt, five types of PSP with different particle sizes and different content were prepared and added into the AH-70 base asphalt. The dynamic shear rheometer (DSR) test was used to evaluate the influence of PSP content and particle size on the rheological properties of asphalt. Rolling thin film oven test (RTFOT) and pressure aging vessel (PAV) were used to simulate the asphalt aging after modification of PSP. The influence of aging conditions on the phosphorus slag modified asphalt (PSMA) was evaluated, and the impact of PSP on the function group of asphalt was analyzed by Fourier Transform Infrared spectroscopy (FTIR). The results indicated that the interaction between PSP and asphalt was mainly physical blending with some degree of chemical reactions. PSP was more sensitive to aged asphalt but less sensitive to original asphalt because it could react with some carbonyl groups. With the increase of PSP content, the shear complex modulus of PSMA increased first and then decreased, and the phase angle decreased first and then increased after RTFOT aging. With the increase of the specific surface area of PSP, the complex shear modulus of PSMA increased and the phase angle decreased. The result found that with the increase of the specific surface area, the high temperature rutting resistance and fatigue performance of asphalt was improved. This study provided important theoretical and practical guidance for the application of PSMA.