Study On The Adhesion Properties Of Polyphosphoric Acid Modified Asphalt And Aggregates And The Water Stability Of The Mixture

Polyphosphoric acid(PPA),as an asphalt modifier with low cost and simple preparation process,has received extensive attention at home and abroad in recent years,but the research on the water stability of asphalt mixture is still controversial.Therefore,in this paper,the water boiling method,contact angle method,photoelectric colorimetric method and dynamic shear rheometer method were used to study the adhesion properties of PPA modified asphalt and aggregates;four-component(SARA),atomic force microscopy(AFM),scanning electron microscope(SEM),X-ray diffractometer(XRD)and other microscopic methods to further explain the adhesion mechanism of PPA modified asphalt and aggregate;Prediction model of asphalt mixture water stability under energy parameters.The specific conclusions are as follows:(1)The optimum dosage of PPA single modified asphalt is 0.95%,and the optimum dosage of PPA composite modified asphalt is:2.0%styrene-butadiene-styrene(SBS)+0.65%PPA and 2.0%Styrene-butadiene(SBR)+0.65%PPA.According to the test results of water boiling method,contact angle method,photoelectric colorimetry method and dynamic shear rheometer method,the adhesion properties of asphalt are all:SBS/PPA>SBR/PPA>PPA>matrix asphalt,and aggregate adhesion properties Both are:limestone>basalt>granite.In addition,the correlation coefficient R2 between spalling work and spalling degree is above 0.70.It is recommended to use contact angle method and photoelectric colorimetric method to quantitatively evaluate the adhesion performance of PPA modified asphalt and aggregate.(2)According to the four-component test of asphalt,the results show that the content of asphaltene and saturate is an important factor affecting the adhesion performance of PPA modified asphalt and aggregate.According to the AFM test results,it is found that the roughness order of the four kinds of asphalt is:SBS/PPA<SBR/PPA<PPA<base asphalt,the smoother the asphalt surface,the stronger the interaction with the aggregate.The roughness of the surface texture of the aggregate is:limestone>basalt>granite.According to the calculation of the mineral content of the aggregate,it is found that the limestone belongs to the ultrabasic rock,and the basalt and granite belong to the acid rock.Among them,the aggregate texture index has a significant positive correlation with the interaction parameter B and the water stability index ER,and the mineral composition content has a significant positive correlation with the water stability index ER.(3)According to the test results of water stability of asphalt mixture,the order of water stability of 4 kinds of asphalt is:SBS/PPA>SBR/PPA>PPA>matrix asphalt,and the order of water stability of 3 kinds of aggregates is:limestone>basalt>Granite,it is recommended to use PPA composite modified asphalt and limestone and basalt aggregates for the combination design of the mixture.According to the prediction model,it is found that there is a good positive linear relationship between the adhesion work Was and the water stability index ER,the residual stability MS0 and the splitting strength ratio TSR,respectively.