Investigation On Asphalt Recycling Based On Multiple Blending Characterization

Due to long-term exposure to light,heat and oxygen,asphalt pavement is prone to aging,leading to the performance deterioration of asphalt pavement,which requires maintenance or resurfacing.A large amount of waste asphalt concrete is produced.It is an effective method to consume the waste asphalt concrete by adding it into the recycled asphalt mixture as aggregate.Hence,the research of blending process between virginal and ageing bitumen in the recycled asphalt mixture and how to improve the performance of recycled asphalt mixture has irreplaceable value and significance for the promotion and application of the recycled asphalt mixture.Based on the raw materials and specific external conditions,Fluorescence spectroscopy,Scanning electron microscopy(SEM),Ultrafine field microscope,and Fourier transform infrared spectroscopy(FTIR)and other technologies were employed to characterize the blending trend and morphological changes of virginal and aging asphalt from multiple blending characteristics.,the research results show that:(1)Based on the fluorescence spectrum,the aging process of bitumen has an obvious corresponding relationship with the excitation wavelength of the fluorescence spectrum.With the aging of bitumen,a significant "blue shift" phenomenon occurs in the excitation wavelength.The larger the magnitude of the “blue shift” vector of the fluorescence intensity peak coordinate is,the more the ageing bitumen is.When the magnitude of the vector is greater than 36,the bitumen has begun to deteriorate.During the mixing of recycled asphalt mixture,the fine aggregate is easier to coat by virginal bitumen than the coarse aggregate.(2)Based on the ultrafine field microscope,the aged bitumen cracked during heating.The optimal heating temperature of the recycled asphalt concrete aggregate is 115 ?,which is conducive to forming a blending interface between the virgin bitumen and the aging asphalt.At 120 ?,the process of infiltration of virginal bitumen into aging asphalt is almost complete,and the flow retardation effect of aging asphalt on virginal bitumen reaches the maximum,which is a better temperature for the blending of virginal and aging asphalt.(3)Based on the fluorescence tracer method,a tracer that emits bright red fluorescence can be seen in a fluorescence microscope.In conjunction with the mapping function in EDS,based on the distribution of Zn elements,the state of blending between virginal bitumen and aging asphalt is "meshing".The gaps between the aggregates in the RAP slice were observed.Through machine learning cluster analysis,it was found that the asphalt thickness on the surface of the aging aggregate in the recycled asphalt mixture was reduced by about 2 to 7 ?m,and the transition zone between the virginal bitumen and aging asphalt blending interface was about 4?8 ?m.