Analysis On Homogeneity Of Mesoscopic Structure Of Hot In-place Recycled Asphalt Mixture

Macroscopic mechanical properties and service life of recycled asphalt mixture are determined by its mesoscopic structure,and merits of the mesoscopic structure are reflected by the homogeneity of spatial distribution of each component of the mixture.Therefore,this paper attempted to do research in the spatial distribution of each component of hot in-place recycled asphalt mixture(AC-13 gradation)specimen from the perspective of mesoscopic by using CT technology and DIP technology.Firstly,based on investigation and analysis,the main factors which influencing the homogeneity of recycled asphalt mixture had been proposed to be quality ratio of old and new mixture,old and new mixture temperature,mixing temperature and mixing time,etc.Then taking various influencing factors of different level,the homogeneity evaluation test plan of hot in-place recycled asphalt mixture(AC-13 gradation)was designed by using orthogonal test design method.Secondly,the specimen scanning mode was chosen according to characteristics of the mixture composition and the specimen size.Then,combined with the general image processing methods,the image processing methods for fault pictures of recycled asphalt mixture specimen was put forward.Thirdly,Area ratio parameter of the basalt aggregate,perlite aggregate,asphalt mortar and void of recycled asphalt mixture specimens of different working conditions have been calculated and analyzed,the result showed that all of the specimens,along the axial direction of the specimen,distribution of area ratio parameter of the basalt aggregate presented a tendency of gradual increase from the bottom to the top.Distribution of area ratio parameter of void of SGC specimens has a characteristics of“small at center,big at both end”,while that of the compression specimens has a characteristics of“small in one end,big in the other end”.What’more,each kind of recycled asphalt mixture specimens,along the axial direction of the specimen,on the whole,void has the most uneven distribution,and the distribution homogeneity of basalt aggregate and asphalt mortar are both better than perlite aggregate.Finally,the single section aggregate homogeneity evaluation index~Qjwas put forward in reference to previous research results.Then,the variation coefficientC.Vof index~Qjof each section was put forward as the homogeneity evaluation index of aggregate of the whole specimen.Range analysis was used to do contrast analysis on the homogeneity index of basalt aggregate,perlite aggregate,asphalt mortar and void of specimens of different working conditions,which proposed the good optimal solution which had better homogeneity,namely,superpave gyratory compaction,with quality ratio of old and new mixture at the situation of30:70,old mixture temperature at the situation of 150℃,new mixture temperature at the situation of 150℃,mixing temperature at the situation of 155℃,and mixing time at the situation of 40s.A comparison of the corresponding homogeneity index of aggregate between specimens of the optimal solution and specimens of different working conditions which belong to the homogeneity evaluation test plan was made,and the result showed that the overall homogeneity of the optimal plan is the best.The study of the distribution respectively along the axial direction and radial direction of old and new aggregate of specimens of optimal scheme was made,and the result showed that,homogeneity of old and new aggregate in central specimen is superior to that at the end of the specimen both along the axial direction and radial direction.