Homogeneity Analysis Of Emulsified Asphalt Cold Recycled Mixture Based On Coarse Aggregate Distribution Characteristics

In view of the fact that asphalt pavement cold recycling technology has high waste utilization rate,relatively little pollution during construction,and relatively good quality,it has been widely concerned and applied.However,due to its own material source,process management and construction technology,it will inevitably cause differences in the uniformity of its internal meso-structure.This affects the internal distribution of new and old aggregates,the properties of asphalt mortar,and the distribution of voids,and even the macroscopic properties of cold recycled asphalt mixtures.As more and more high-grade highways are undergoing large and medium repair periods or reconstruction and expansion projects,the structural layer where cold recycled mixture is applied becomes more and more important,and the uniformity evaluation of its construction quality is very important.From a meso-level perspective,based on the distribution characteristics of the coarse aggregates in the cold recycled mixture,industrial CT and digital image processing technology are used to obtain non-destructively information on the internal characteristics of the cold recycled mixture.From the two aspects of volume characteristics and virtual mechanical tests,Establish the uniformity analysis method of the cold recycled mixture,put forward the corresponding evaluation index,and conduct a systematic evaluation of the uniformity of the cold recycled mixture.First,in order to identify the new and old aggregates in the cold recycled mixture,a multiindex identification method for the new and old materials is established.Using iron tie wire and zirconium glass beads to make cold recycled mixture calibration specimens,identification indicators such as the average thickness of mortar,the proportion of equivalent circular expansion mortar,and the proportion of equivalent circular expansion voids are proposed.The recognition effect is good,and the recognition rate can reach about 80%.Secondly,in terms of volume characteristics,use IPP graphics processing software to obtain the basic properties of coarse aggregates,and use SPSS data analysis software to draw box diagrams to analyze the dispersion of coarse aggregate volume information in different cross-sectional images.Based on the new and old material identification methods,A number of evaluation indicators such as coarse aggregate area ratio(coarse aggregate area ratio,new-toold area ratio,coarse aggregate uniform variation coefficient),sand glue film thickness,coarse aggregate uniform distribution coefficient,coarse aggregate distribution coefficient,etc.are proposed.The uniformity of the distribution of coarse aggregates in cold recycling specimens of different gradation types was evaluated.Third,in terms of virtual mechanical test,import the acquired coarse aggregate spatial distribution information into PFC software to construct a three-dimensional discrete element mechanical model,perform virtual uniaxial compression test,analyze the data distribution using box diagrams,and propose the mean value of cross-sectional stress And stress uniformity coefficient two evaluation indicators,to explore the influence of specimen uniformity on mechanical properties.Finally,the above-established cold recycling uniformity evaluation method is applied to engineering projects,which can effectively evaluate the quality uniformity of engineering sections from a meso-level perspective,and find out the cause of the problem through differentiation,which is the engineering application and application of cold recycling technology.Its uniformity evaluation provides reference.