Research On Adhesion Between Asphalt And Aggreate Based On Surface Energy Theory

With the increase of traffic volume,the phenomenon of overloading and overspeeding is becoming more and more serious.Asphalt membrane peeling,falling out,loosening and pits generally appear after the asphalt pavement been used for several years,which will not only reduce driving comfort,but also shorten the service life of the road and increase maintenance costs.Adhesion is the main factor affecting the structural strength and water stability of the mixture.Therefore,it is important to research the adhesion between asphalt and aggregate to improve the water resistance of asphalt mixture.Based on previous research,this paper analyzes the interaction mechanism of asphalt and aggregate,and the adhesion model and the water damage model of the asphalt-aggregate system were established,according to the surface energy theory.The parameters of surface energy of the asphalt and aggregate were measured and the adhesion of the asphalt and aggregate was quantitatively evaluated.Boiling text,immersion Marshall test,freeze-thaw splitting test and other methods were used for verification.The main conclusions are as follows:(1)As the asphalt is mainly composed of non-polar hydrocarbons,the dispersion component is the main part of the surface energy.Since SBS absorbs the light oil component of the asphalt,the nonpolar light oil component is converted to polar colloid and asphaltenes,increasing the polar component of SBS modified asphalt.The adhesion work produced by the polar component is also greater,so the adhesion between SBS modified asphalt and aggregate is stronger.(2)In anhydrous conditions,the adhesion work of asphalt aggregate system is positive,and under water conditions the spalling work is also positive,which shows the decrease of the Gibbs free energy of the system.The process of adhesion between asphalt and aggregate can be carried out spontaneously in anhydrous conditions as well as the peeling process under water condition.(3)The same conclusion is obtained from water boiling text and adhesion work.When use the matrix asphalt,adhesion is ordered as: limestone> sandstone> granite.With use of the SBS modified asphalt,the adhesion properties of the aggregate are improved.Adhesion grade of limestone and sandstone are 5,and their adhesion work is almost the same.Adhesion grade and adhesion work of granite are relatively low.(4)The water stability evaluated by the absolute value of the ratio of adhesionwork and exfoliated work is basically the same as that of the immersion Marshall test and the freeze-thaw splitting test.When using matrix asphalt,the water stability is ordered as: limestone> sandstone> granite.With the use of modified asphalt,the water resistance of the system is improved,in which the limestone is the highest.(5)In fatigue test,the fatigue life of immersed limestone,sandstone asphalt mixture is reduced compared to the non-immersed asphalt mixture,and sandstone asphalt mixture decreased the most.In anhydrous conditions,the specimen is split,while the immersed specimen is split and sheared.