Study On Adhesion Mechanism Of Asphalt Pavement To Hot-poured Sealant Based On Surface Energy Theory

Hot-poured sealant is a kind of sealing material commonly used in crack repair of asphalt pavement.According to the survey data,the early failure of sealant is generally found after a period of use.The lack of adhesion between the sealant and the crack wall is the main cause of the failure of sealant.At present,there is no uniform and reasonable evaluation method for the adhesion failure of sealant,especially the lack of quantitative indicators.Therefore,based on surface energy theory,this paper quantitatively evaluates the adhesion between crack walls and different types of sealant with different material compositions,and considers the geometric characteristics of crack walls and the influence of environmental factors such as temperature and moisture.It reveals the adhesion mechanism of asphalt pavement sealant and provides a theoretical basis for the selection of sealant and evaluation of adhesion.Firstly,based on the investigation and research,the raw materials commonly used in the asphalt pavement filling system are selected.The basic theory of surface energy is introduced.The contact angle between the raw materials and the three test liquids is determined by the sessile drop method,which provides theoretical support and data source for the calculation of adhesion work.According to Owens-Wendt theory,the adhesion work of cement,stone and crack sealant under waterless conditions was calculated respectively.The rationality and correlation of the results of adhesion work were tested by quantitative boiling method combined with SEM test.The results of quantitative boiling method show that there is a good linear relationship between the adhesion work and the test results,the coefficient of determination is as high as 0.9308,indicating that the adhesion work index can accurately characterize the actual adhesion performance of sealant and stone.Then,four kinds of mixture samples were made,and the area occupied by the stone,cement and voids of the mixture cross-section was extracted based on Matlab digital image processing technology,and the weighted average adhesion work of different crack sealantmixture sections was calculated.The relationship between the weighted average adhesion work of the mixture sections and the sealant A is:AC-13>AC-25>SMA-13>AC-20;The stone area plays a leading role in the weighted average adhesion work of the sealant-mixture cross-section.Cmbined with the adhesion test,it was found that the determinant coefficients of the linear correlation between the weighted average adhesion work and the shear and tensile tests are 0.8672 and 0.8906 respectively,and the goodness of fit is high,indicating there is a good correlation between the proposed weighted average adhesion work index and the actual interface adhesion strength.Finally,the influence of temperature and moisture on the adhesion of the crack sealant was discussed and verified by the interface shear test.The results show that with the increase of temperature and the invasion of water,the interfacial adhesion strength between the sealant and the four mixtures gradually decreased,and the degree of decrease was more than 50%.At this time,the adhesion failure of the sealant was prone to occur.Therefore,effective cooling and drainage measures should be taken during the construction and normal use of asphalt pavement to delay the process of adhesion failure of the sealant.Thus,the service life of sealant can be prolonged.