Study On Road Performance Of PPA/SBR Composite Modified Asphalt And Mixture

Styrene-butadiene rubber(SBR)modified asphalt is widely used in asphalt pavement in northern China because of its excellent low temperature performance,but its high temperature performance is general,and asphalt pavement is prone to high temperature stability when used in areas with large temperature difference.Polyphosphoric acid(PPA),as a kind of inorganic acid,was initially used to make drugs,chemical fertilizers and other materials.in recent years,it has been found that adding polyphosphoric acid into asphalt can effectively improve the rutting resistance of asphalt.In order to realize the complementary advantages of the two modifiers,PPA/SBR composite modified asphalt and mixture were prepared in this paper,and their properties were tested.Firstly,the paper studies the performance of PPA/SBR composite modified asphalt through three index tests,DSR,BBR and other tests.Three major index tests found that PPA can greatly enhance the high temperature performance of asphalt,but a higher amount of PPA will weaken the low temperature performance of asphalt,SBR can not improve the high temperature performance of asphalt,when the SBR content is more than 3%,the low temperature performance of asphalt is significantly improved.The DSR test shows that the rutting factor~*/sinincreases rapidly in the range of 0.5%-1.5%PPA content.BBR test found that the low temperature performance of composite modified asphalt decreased obviously when the content of PPA was more than 1.5%.Secondly,the interaction between PPA,SBR and asphalt was studied by molecular dynamics simulation.The results show that the interaction energy between SBR and matrix asphalt,PPA and SBR modified asphalt is mainly van der Waals potential energy,and the addition of PPA further increases the van der Waals potential energy,indicating that PPA enhances the bond strength of asphalt interface,thus improving the high temperature performance of modified asphalt and making the system tend to a more stable state.Compared with the base asphalt,the glass transition temperature of SBR modified asphalt decreases obviously,and the glass transition temperature of PPA/SBR composite modified asphalt is very close to that of SBR modified asphalt,indicating that there is little difference in their low temperature performance.Compared with base asphalt,the free volume fraction of SBR modified asphalt decreases obviously,and the free volume fraction of composite modified asphalt is similar to that of SBR modified asphalt,which indicates that PPA/SBR composite modified asphalt and mixture have better low temperature performance and water damage resistance.Finally,through the response surface method,the paper determined that the best content of PPA is 1.022%and the best content of PPA is 3.977%.Based on this,four kinds of mixtures of matrix asphalt,single modified asphalt and compound modified asphalt were prepared,and their high and low temperature performance,water stability and aging resistance were studied.The results show that the high temperature stability,water stability and aging resistance of PPA/SBR composite modified asphalt mixture are better than the other three kinds of asphalt mixture,and the low temperature crack resistance of PPA/SBR composite modified asphalt mixture is slightly lower than that of SBR modified asphalt mixture.Generally speaking,PPA/SBR composite modified asphalt mixture has better comprehensive road performance.