Study On The Performance Of PPA/LSBR Composite Modified Asphalt And Mixture

Rubber materials are widely used in asphalt because of their strong elasticity,easy recovery under stress,and low glass transition temperature.However,the preparation process is complicated,the cost is high,the obtained modified asphalt has low compatibility with the asphalt,and it has disadvantages such as poor high-temperature storage stability and easy segregation.The liquid rubber has the excellent performance of wet rubber modified asphalt,but its high temperature performance cannot meet the needs of the current road surface.However,polyphosphoric acid not only chemically cross-links with the asphalt,but a small amount can significantly improve the high-temperature performance of the asphalt,so polyphosphoric acid is selected as the composite modifier.The thesis prepares liquid rubber(LSBR)modified asphalt and polyphosphoric acid/liquid rubber(PPA/LSBR)composite modified asphalt with different content.The four parameters of rutting factor,fatigue factor,viscosity temperature index VTS,continuous grading temperature T_C,Burger model and G-R parameter index based on black space are used to explore the high and low temperature performance of modified asphalt.Through four-component test,infrared spectroscopy and fluorescence microscope to study the change of asphalt components and microstructure,analyze its modification mechanism,and verify the road performance of SK90,SBS,LSBR,PPA/LSBR composite modified asphalt mixture.The main research conclusions are as follows:1)Conventional performance test shows that LSBR modifier significantly improves the low temperature performance of asphalt,but it will have an adverse effect on high temperature stability.The incorporation of PPA can significantly improve the high temperature performance of LSBR modified asphalt.2)From the results of the DSR test index,it can be seen that the fatigue resistance,temperature sensitivity and elastic recovery performance of the PPA/LSBR composite modified asphalt at the optimal content are better than that of the LSBR modified asphalt.3)According to the BBR test results,it can be concluded that the cracking risk of LSBR modified asphalt is less than that of PPA/LSBR composite modified asphalt.4)The black space parameters indicate that the PPA/LSBR composite modified asphalt increases the composite shear modulus of the asphalt and delays the aging of the LSBR modified asphalt.5)The infrared spectrum results show that LSBR and asphalt are simply blended physically,while new functional groups appear in the PPA/LSBR composite modified asphalt,which is chemical modification.6)Fluorescence microscope test results show that the addition of PPA improves the compatibility and stability of LSBR modified asphalt.7)According to the conventional performance test of the mixture,it can be concluded that the high temperature performance and anti-aging performance of PPA/LSBR composite modified asphalt are better than that of LSBR modified asphalt,and there is little difference in low temperature crack resistance between the two.According to the actual performance of the modified asphalt in the road performance of the mixture,it is recommended to use PPA/LSBR composite modified asphalt in areas with large temperature differences.