Analysis And Characterization On Blend And Diffusion Of Virgin And Reclaimed Asphalt In Hot Recycled Asphalt Mixtures

With the extensive application of reclaimed asphalt pavement technology all over the world,many fruitful researches make significant progress on reclaimed asphalt.However,due to the uncertainty of the degree of blending and actual diffusion state of the virgin and reclaimed asphalt,it is hard to accurately guide the recycled asphalt mixture design method and predict the mechanical behavior of asphalt pavement.Therefore,to characterize and analyze the degree of blending and diffusion homogenization of the virgin and reclaimed asphalt could help deeply understand the blend and diffusion mechanism,and are also of great significance for guiding the accurate recycling of asphalt mixtures and improving the recycling quality of asphalt pavement.Firstly.Comparing the tracers and observation methods commonly used to analyze the blend of new and reclaimed asphalt,an experimental design method and specific implementation steps based on the fluorescent particle characterization and laser scanning confocal microscope were proposed.The feasibility plan of three-dimensional observation and quantitative characterization of the blend and diffusion of new and reclaimed asphalt was determined.As substitute to virgin and RAP aggregate,the pretreatment steps were conducted in aggregates simulated by wooden,including the process of polishing the surface,the elimination of its auto-fluorescence and the correction of the amount of asphalt to ensure the uniformity of the asphalt film thickness.the standardization of sample preparation was achieved.Secondly.In order to address the noise and depth attenuation and loss of the laser scanning confocal microscope,the self-threshold median filter algorithm,the brightness attenuation function based on depth experience parameters,and the distribution of brightness weight coefficients based on depth of field and focal plane were determined.Meanwhile,Confocal preprocessing steps for fluorescence intensity image such as noise reduction,light scattering and absorption correction,image segmentation and feature extraction were performed to ensure correct quantification and characterization of the blend and diffusion processes for the virgin and reclaimed asphalt.According to the decay function of fluorescence intensity after the blend of virgin and reclaimed asphalt,the definition about the degree of blending based on area method was proposed,and the homogenization coefficient was introduced to characterize the diffusion homogenization.Finally.Based on the observation and characterization methods above for the blend and diffusion of the virgin and reclaimed asphalt,the degree of blending and diffusion homogenization on the construction phase and the pavement service status were separately analyzed.Influencing factors such as the heating temperature,heating time,different blend and homogenization on virgin and RAP aggregate were compared.It was found that heating temperature has more significant effect than heating time.Therefore,the blend and diffusion on construction phase has a greater impact than on the pavement service status.There are different proportion of virgin and reclaimed asphalt between the virgin and RAP aggregates,and the diffusion homogenization on the virgin aggregate was better than on RAP aggregate.In addition,on the basis of the verification analysis of image processing technology and laser scanning confocal microscope,virgin aggregates hold smaller particle size will be transferred more reclaim asphalt,which will further affect the blend and diffusion process of virgin and reclaimed asphalt.