Influence of Polyphosphoric Acid on Various Base Asphalt Performance
In the long service of asphalt pavement,heavy load,climate erosion and environmental degradation reduce asphalt performance,leading to the emergence of pavement disease.Therefore,in order to improve the performance of asphalt pavement,modified asphalt is widely used in road construction.The traditional polymer modified asphalt has disadvantages of high price and poor storage stability,therefore it is supposed to be modified with polyphosphoric acid(PPA).Compared with traditional polymer modified asphalt,PPA modified asphalt has the advantages of good compatibility,low price and excellent high temperature performance,however,the modification effect of PPA on different base asphalt varies greatly.Therefore,6 types of commonly used domestic base asphalt are selected.The high and low temperature performance and adhesion properties of various PPA modified asphalt are studied by softening point,ductility and penetration test,bending beam rheometer test,temperature sweep test and pull-off test.The result shows that PPA addition can improve the softening point of asphalt significantly,with the increase of PPA content,the ductility and penetration of asphalt decrease gradually,and the stiffness modulus increases significantly at ―18℃,indicating that PPA has a significant negative effect on the low temperature performance of asphalt.The result of temperature scanning test shows that the influences of PPA on the rheological properties of various base asphalt are quite different,asphalt PPA+70#has a generally higher rheological performance than that of asphalt PPA+90#,but its temperature sensitivity is greater.The result of Pull-off test shows that PPA addtion can improve the drawing strength of asphalt significantly,indicating that PPA modified asphalt has excellent adhesion property.The result of infrared spectrum test shows that the reactions of PPA with different asphalt are quite different.
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