Research On The Performance Of Recycled Asphalt Mixture Based On The Homogeneity Of Mortar And Aggregate Skeleton

The use of plant-mixed hot recycling technology to recycle reclaimed asphalt pavement(RAP)of old asphalt pavement can reduce engineering costs and promote green environmental protection.However,the transmission of RAP variation at micro,meso and macro scales will seriously affect the performance of recycled asphalt mixture.The high viscosity of the aged asphalt mortar in RAP affects the homogeneous miscibility with the new asphalt mortar.The cluster phenomenon caused by RAP particles hinders the homogeneous distribution of aggregates in the mixture.The inhomogeneous distribution of components leads to the easier cracking of recycled asphalt pavement,which affects the durability of the pavement and limits the further improvement of RAP utilization.Asphalt mixture is a multiphase composite material composed of coarse aggregates forming a skeleton structure.Asphalt mortar binds the aggregates while filling the voids therein.Therefore,the overall macroscopic mechanical properties of asphalt mixtures depend on the technical properties of the mortar and aggregate.The homogeneity of the distribution of fillers in the differential dispersion of asphalt mortar and the performance of the mortar simultaneously affect the mechanical properties of recycled asphalt mixtures,while the evaluation of the homogeneity of new and old mixed asphalt mortar is rarely mentioned in existing research.In addition,the homogeneity of mixtures is also closely related to the mechanical properties of materials,but mechanical parameters have not been involved in previous homogeneity studies.The proposed homogeneity evaluation method cannot form a clear mapping relationship with the true performance of mixtures,and lacks clear mechanical theoretical background support.Based on the above background,this paper attempts to quantitatively characterize the homogeneity of new and old mixed asphalt pastes,and characterize the characteristics of stress transfer in the skeleton structure by drawing a force chain network,adding mechanical performance parameters to the mixture homogeneity evaluation system,and ultimately constructing a correlation analysis model for the homogeneity of mixed asphalt pastes,mixture homogeneity,and macroscopic mechanical properties of recycled asphalt mixtures.The main work and conclusions of the paper are as follows:(1)A bending beam rheometer test(BBR)was carried out for new and old mixed asphalt mortar.The variation coefficient of the S/m value of the test results was used as the homogeneity evaluation index for mixed asphalt mortar to quantitatively characterize the homogeneity of the mortar and reflect the performance reliability of the mixed asphalt mortar.(2)Using digital image processing(DIP)technology,the new diabase aggregate and the old marble aggregate in the recycled asphalt mixture are distinguished from the asphalt mortar.Define aggregate contact point identification criteria,independently develop identification programs,search for and label aggregate indirect contacts,extract the stress state of the internal force chain transmission of the mixture using ABAQUS simulation mechanical tests,and propose the concept of vertical stress efficiency(ETVS)of force chain transmission,which characterizes the homogeneity of recycled asphalt mixture using the dispersion degree of ETVS.(3)The correlation analysis between the homogeneity of mixed mortar,the homogeneity of recycled mixture,and the mechanical properties of the mixture shows that the homogeneity index D1 based on ETVS has a good correlation with the compressive performance of the mixture,and the homogeneity index D2 based on the distribution of new and old aggregates has a good correlation with the compressive performance stability of the mixture.The homogeneity of mixed mortar The transverse homogeneity index D_H2 of the mixture has a good correlation with the fracture energy G_fof the mixture.