Research On Rheological Properties Of Polyphosphoric Acid Composite Modified Asphalt And Road Performance Of Mixture

As a road asphalt modifier,polyphosphoric acid(PPA)can improve its high temperature stability and fatigue resistance by adding to asphalt.Due to its simple preparation process and low price,it has attracted the attention of many scholars at domestic and foreign in recent years.However,due to the disadvantages of polyphosphoric acid modified asphalt in low temperature stability,and the lack of systematic research on its technical properties and modification mechanism,it is limited in domestic application.Based on the rheological behavior of asphalt,this paper studies the viscoelastic properties and modification mechanism of polyphosphoric acid composite modified asphalt and the pavement performance of the mixture.Based on the shortcomings of polyphosphoric acid modified asphalt in low temperature stability,PPA is added in different amounts of 2.8% SBS modified asphalt and 18% Crumb rubber modified asphalt,and PPA/SBS and PPA/Crumb rubber composite modified asphalt were prepared under high shear environment.The high temperature viscoelastic properties,low temperature creep properties,fatigue resistance and modification mechanism of composite modified asphalt before and after aging were analyzed by three major indexes of asphalt DSR,BBR rheology and infrared spectroscopy.The viscoelastic properties of PPA/SBS composite modified asphalt and PPA/ Crumb rubber modified asphalt before and after aging were studied.The results show that the addition of polyphosphoric acid improves the high temperature stability and creep recovery performance of SBS modified asphalt and Crumb rubber modified asphalt,and the improvement of SBS modified asphalt is better than Crumb rubber modified asphalt.The low temperature performance is weakened,but the low temperature stability of PPA/ Crumb rubber composite modified asphalt is still excellent,and it is better than 5% SBS modified asphalt and PPA/SBS composite modified asphalt.In terms of modification mechanism,the infrared spectrum image showed a weak absorption peak at the absorption peak of polyphosphoric acid,and a characteristic absorption peak with strong and weak intensity appeared at other positions.It indicates that the addition of PPA has both chemical reaction with asphalt and physical blending.The technical performance of polyphosphoric acid composite modified asphalt was comprehensively analyzed.The suitable dosage range of PPA in PPA/SBS and PPA/ Crumb rubber composite modified asphalt was 0.8%-1.2% and 1.2%-1.6%.The asphalt mixture was prepared by using 1.2% PPA/SBS,1.6% PPA/rubber powder composite modified asphalt,matrix asphalt and 5% SBS modified asphalt.The road performance of polyphosphoric acid composite modified asphalt mixture was verified by routine performance test and four-point bending fatigue test.The results show that the addition of PPA can improve the high temperature performance and fatigue performance of the mixture,and weaken its low temperature and water resistance performance,but the PPA/SBS and PPA/ Crumb rubber composite modified asphalt mixture are optimally blended.The low temperature stability and water resistance performance under the amount is higher than the specification requirements,and has good road performance.