Investigation on mechanism and rheological properties of Bio-asphalt/PPA/SBS modified asphalt

To promote the application of environmentally-friendly and sustainable bio-asphalt (BA) in road engineering, polyphosphoric acid (PPA) and styrene–butadienestyrene (SBS) were used to prepare BA/PPA/SBS composite modified asphalt. The mechanical properties of composite modified asphalt and the interaction mechanism of each modifier were investigated through conventional property, rheological property, infrared spectroscopy, fluorescence microscopy test, and gravimetry analysis for SARAs fractions. The conventional property test results show that PPA and BA improve the storage stability of SBS modified asphalt, and the composite modified asphalt with lower SBS content still has excellent performance. The rheological property test results show that the decrease of SBS content has negative effect on the rheological property of asphalt. But in general, the composite modified asphalt has good high-temperature deformation resistance. The IR-spectra of BA before and after reacting with PPA indicates that the chemical composition of the BA in this study was mainly sugar alcohols, and the esterification reaction occurred during reaction with PPA. By comparing the fluorescence images, it was found that the BA significantly improve the dispersion and compatibility of SBS particles in asphalt. The SARAs fractions analysis shows that the composite modified asphalts have higher content of asphaltenes and aromatics.