Study On The Micromorphological Characteristics Of Asphalt And Mastic Area In Asphalt Mixture

Asphalt mixture is a complex heterogeneous distributed material,its spatial structure is complex which has a decisive influence on the service behavior of asphalt pavement.Therefore,it is of great significance to improve the service performance of asphalt pavement,to clarify the internal morphological structure of asphalt mixture at the microscopic level.At present,advanced technologies such as nanometer and CT have been applied to the study of microstructure in asphalt mixtures,which has promoted the rapid development of asphalt pavement design theory and technology.However,the research on the microstructure of asphalt mixture is very limited at present.In this study,a microsection technique was employed to established a prepare asphalt mixture microsections,which retained the original spatial structure and micromorphology of the mixture.At the same time,the microscopic morphology of SBS modifier in asphalt and its mixture,the microstructure of old and new asphalt mixed mortar in regenerated mixture were quantitatively characterized by fluorescence microscopy and image analysis.Firstly,a quantitative characterization method for the distribution of SBS modifier in asphalt and its mixture was proposed,and a prediction model for the viscoelastic properties of asphalt was established based on the micromorphology parameters: SBS asphalt microsections,SBS asphalt mixture microsections and hot regenerated mixture microsections are prepared by microchip technique.The image processing technology is applied to segment each component of SBS asphalt mixture image more accurately.The six parameters of area ratio,box dimension,particle area,coefficient of variation in area,the area weighted average axis ratio and the coefficient of variation in axis ratio are used to characterize SBS in microscopic morphology under different process parameters.The influence mechanism of SBS content,shear temperature and shear rate on SBS microscopic morphology are analyzed,and the relationship between the micromorphological parameters of SBS and rheological properties in modified asphalt was studied.Through the analysis of the difference in the microscopic morphology of SBS modifier in asphalt and asphalt mortar.It is proposed that the microscopic morphology of SBS particles is affected by multiple factors such as secondary swelling,mineral powder filling and friction,large size packing extrusion,etc.Secondly,a method for analyzing the miscibility state of old and new asphalt in the recycled asphalt mixture was proposed,and the influence mechanism of miscibility of old and new asphalt was clarified.The gray variation coefficient of the old and new asphalt interface in the hot regenerated mixture was used to evaluate the fusion state of the old and new asphalt under different processing parameters.The influence of process parameters on the fusion state of old and new asphalt and the macroscopic performance of the hot regenerated mixture was studied,and the correlation between the fusion state of old,new asphalt and the hot regenerated mixture’s high temperature anti-rutting performance,low temperature anti-cracking performance was further analyzed.With the help of fluorescence microscope system,the crack morphology of semicircular bending specimens of hot regenerated mixture and ordinary asphalt mixture was obtained.By comparing the crack morphology of the two mixtures,the effects of three cracking modes of the old and new asphalt interface on the structure were analyzed,the mechanism influence of the fusion state of old and new asphalt on the anti-cracking performance at low temperature was explained from a microscopic perspective.The above research results show that it is feasible to analyze the microstructure of the mastic area in asphalt mixture by microsection technique.The two mathematical model based on the classic model can predict the rut factor by SBS microscopic morphology parameters in a certain range.The gray variation coefficient of old and new asphalt interface is closely related to low temperature performance of hot regeneration asphalt mixture.The research results have good reference and promotion value,as they provide a good method for the study of micro-scale behavior,micro-damage mechanism and performance improvement technology of recycled asphalt mixture.