Study On Adhesion Properties And Microscopic Characterization Of Polyphosphoric Acid Composite SBS Modified Bitumen

SBS modified asphalt has been widely used in expressway construction because of its good road performance.However,with the rise of petroleum price and polymer price,the price of polymer modified asphalt is more expensive.In addition,as a typical pavement disease,rutting and water damage make the current asphalt pavement face greater challenges.Based on this,polyphosphoric acid as a cheap acid modifier applied to road asphalt modification has gradually attracted the attention of scholars at home and abroad.However,at present,there is a lack of means to evaluate the water damage of polyphosphoric acid modified asphalt.The addition of SBS modifier and other raw materials makes its composition more complex,resulting in the bottleneck of its water damage mechanism.In this paper,the macroscopical and adhesion properties of polyphosphoric acid modified asphalt,polyphosphoric acid modified SBS?PPA/SBS?asphalt and polyphosphoric acid modified SBS asphalt after aging were studied by macroscopical technical performance index and surface energy free energy theory.The modification mechanism of polyphosphoric acid modified asphalt,polyphosphoric acid modified SBS asphalt and polyphosphoric acid modified SBS was analyzed by infrared spectroscopy.The aging mechanism of modified asphalt was revealed by atomic force microscopy.Finally,the adhesion mechanism of polyphosphoric acid modified asphalt,polyphosphoric acid modified asphalt and polyphosphoric acid modified asphalt after aging was revealed,and the relationship between micro-characterization method and macro-technical performance index and adhesion performance index was established.The results show that:?1?Polyphosphoric acid can significantly improve the high-temperature performance of base asphalt,but also make its low-temperature performance reduce greatly;when polyphosphoric acid and SBS modifier are mixed,not only improve its high-temperature performance,but also make the low-temperature performance meet the requirements of polymer modified asphalt.In addition,polyphosphoric acid can significantly improve the aging resistance of SBS modified asphalt.?2?New compounds were formed during the modification of polyphosphoric acid,which indicated that chemical modification was the main modification process.The characteristic peaks of 1030cm^-1,966cm-1 and 1700cm^-1 in the aging process of SBS modified asphalt with polyphosphoric acid compound show obvious changes.However,with the increase of aging temperature and the extension of aging mode,the increase of carbonyl and sulfoxide characteristic peaks is significantly smaller than that of SBS modified asphalt.It shows that PPA delays the aging of SBS modified asphalt with polyphosphoric acid compound and improves the aging resistance of SBS modified asphalt.?3?Polyphosphoric acid improves the adhesion performance of PPA modified asphalt and SBS modified asphalt.When PPA=0.5%,DBP=1.0%,extraction oil=1.5%,SBS=3.5,the adhesion performance of PPA/SBS modified asphalt is improved the most.Compared with the original SBS modified asphalt,with the increase of short-term aging temperature,the adhesion performance of polyphosphoric acid composite SBS modified asphalt gradually improved,while the adhesion performance of long-term aging SBS modified asphalt gradually became worse than the original SBS modified asphalt.?4?The honeycomb structure of polyphosphoric acid modified asphalt is more obvious than that of base asphalt.With the increase of concentration,the honeycomb structure decreases and disperses gradually.At the same time,polyphosphoric acid makes the nano-adhesion of polyphosphoric acid modified asphalt and PPA/SBS modified asphalt decrease obviously.After short-term aging at different aging temperatures,with the increase of aging temperature,the apparent adhesion,peak area ratio and surface roughness of PPA/SBS modified asphalt gradually increase.After long-term aging,the nano-adhesion,peak area ratio and surface roughness of PPA/SBS modified asphalt show a decreasing trend compared with short-term aging.?5?In the process of polyphosphoric acid modification,the performance changes mainly depend on the type of base asphalt,the type of PPA and the content of raw materials.Among them,when the base asphalt is SK90#base asphalt,PPA type is 115%PPA,PPA=0.5%,DBP=1.0%,extraction oil=1.5%,SBS=3.5,the adhesion performance of PPA/SBS modified asphalt is the best.?6?It is suggested that the nano-adhesion force should be used to characterize the change of adhesion properties of polyphosphoric acid modified asphalt and PPA/SBS modified asphalt,and the peak area ratio should be used to characterize the change of adhesion properties of aged PPA/SBS modified asphalt.