Shear Performance Analysis Of Reclaimed Asphalt Mixture Based On Contact Effect Of Aggregate Interface

The friction effect and migration mechanism between aggregates of asphalt mixture determine the macroscopic mechanical behavior of the mixture and affect the pavement performance of the material.In the past,the research on hot recycled asphalt mixture mainly started from the aspects of asphalt aging and regenerating mechanism,regenerating agents,additives,gradation and so on,and the deformation consistency of the composite skeleton of old and new aggregate under the action of load has not been paid enough attention to.The skeleton of hot recycled asphalt mixture is significantly different from that of new asphalt mixture,with the characteristics of different granule strength,uneven asphalt fusion,and different properties of old and new aggregate skeletons,so the research theory based on the traditional homogeneous hypothesis is not applicable to this kind of materials.In this paper,with the help of the independently developed"Asphalt Mixture Particle Shear Analysis System"and the pressure film technology,the particle interface shear test of AC-13 hot recycled asphalt mixture with different recycled asphalt pavement(RAP)content was carried out.Based on the theory of particle mechanics,the mechanical behavior of the contact interface of the internal skeleton particles in the hot recycled asphalt mixture was analyzed,and the influence of"new-new contact","new-old contact"and"old-old contact"on the shear modulus of the mixture was obtained by statistical analysis and weight analysis.The main conclusions are as follows:(1)The experimental results of contact boundary mechanics based on LLW film show that the asphalt mixture in compacted state has significant granule characteristics.RAP content has a significant impact on the contact interface area and stress distribution.The mixturel with RAP content of 50%has the largest particle contact area,and the particle contact stress is concentrated in 0.1?0.2mpa.(2)The results of particle interface shear test show that the particle interface shear stress of the hot recycled asphalt mixture with the RAP content of 30%is the largest.The analysis of the equivalent friction coefficient shows that the shear resistance of the hot recycled asphalt mixture is better than that of the new asphalt mixture when the RAP content of the mixture is more than 30%,and reaches the best when the RAP content of the mixture is 50%.(3)The interface tangential elastic strength of the hot recycled asphalt mixture increases with the increase of RAP as a whole,and the resistance to tangential deformation of the hot recycled asphalt mixture increases with the increase of RAP content.(4)The statistical results of the number of contact points of hot recycled asphalt mixture based on digital image processing technology show that the total number of particle contact points of hot recycled asphalt mixture does not change with RAP content under the same first-stage configuration,and the number of contact points of AC-13 asphalt mixture coarse aggregate skeleton in the cross-area of 5000mm~2is about 38.(5)The uniaxial test results show that the shear modulus estimation model of asphalt mixture based on the assumption of uniform strain and static mechanics and the interfacial shear test has a high degree of interpretation.The interpretation of the numerical analysis results show that the uniform strain model can better estimate the hot recycled asphalt mixture's shear modulus.(6)Based on the classification and analysis of the aggregate internal contact of the hot recycled asphalt mixture,the uniform strain model was modified,and finalized the basic expression of correction model formula.