Study On The Influence Of Aggregate Morphology On Asphalt Mixture Microstructure And Mechanical Properties

Asphalt mixture is affected by factors such as the diversity of the constituent materials,the irregularity of the shape of the aggregate,and the uneven particle distribution during the preparation process,even in the case of the same gradation,there is a large variation between the internal mesoscopic structural characteristics and mechanical properties.Existing asphalt mixture volume evaluation parameters can only describe the characteristics of the asphalt mixture as a whole,and cannot reflect the spatial distribution of the materials inside the mixture from a microscopic perspective,and it is difficult to mechanically conduct the complicated destruction behavior of the asphalt mixture.Explanation.With the application of X-ray CT equipment in the industrial field and the development of image processing methods,a relatively complete digital image processing process for mixtures and meso-structure evaluation methods have been formed at home and abroad.,The extraction of void area and characterization of spatial distribution,the variability of the meso-structure characteristics of the mixture,the correlation between macro and micro performance have made many achievements.This paper conducts research on the influence of aggregate morphology on the mesostructure parameters,mechanical properties and stress distribution of asphalt mixture.The main research contents and research results are as follows:The digital image processing flow based on the two-dimensional image optimizes the digital image processing method of the three-dimensional model,completes the extraction of the aggregate image in the three-dimensional numerical model of the asphalt mixture,and uses the sub-matrix recognition algorithm based on the connected area judgment to generate and mark A three-dimensional matrix representing a single aggregate is used,and the particle size recognition algorithm that simulates the actual screening process is used to verify the accuracy of the three-dimensional particle extraction of the aggregate.With reference to the aggregate morphology characteristics of two-dimensional space and the meso-structure evaluation parameters of asphalt mixture,the three-dimensional evaluation method of aggregate and mixture mesostructure is improved,and the ratio of shaft length is used to characterize the sheet needle characteristics of the aggregate.The ratio of the surface area of the aggregate to the equivalent circle is used to characterize the angularity of the aggregate.The tilt angle of the aggregate is used to describe the distribution characteristics of the aggregate.The number of contact points is used to describe the contact characteristics of the aggregate.The uniformity coefficient is used to describe the distribution uniformity of the aggregate.Then completed the development of extraction algorithms and the preparation of programs.Using the method of changing the amount of needle-shaped aggregate addition and the times number of aggregate polishing,an asphalt mixture specimen with different shapes and angular aggregates was formed,and the asphalt mixture specimen was completed by X-ray CT scanning equipment.Meso-structure image extraction.The mesostructure parameters of the asphalt mixture were extracted by using a self-written program,the digital quantification of the flaky and angular characteristics of the aggregate needles was completed,and the characteristics and sensitivity of the three-dimensional parameters to characterize the meso-structure of the mixture were verified and carried out.The effect of different aggregate morphologies on meso-structure characteristics is studied.Based on the meso-structure image of the real test piece,PFC discrete element particle flow software was imported,a model generation program was written,and a discrete element model of asphalt mixture was established.The linear elastic model and Burgers model were used to characterize the mechanical properties of aggregate and mortar,respectively.Through experiment and formula derivation,the material micromechanical parameters are obtained.Finally,through the PFC discrete element particle flow software,the virtual loading of the static load creep test was carried out.The creep modulus and displacement curve were used to evaluate its mechanical properties.The contact force distribution of the aggregate during the loading stage was extracted and the set was analyzed.Correlation between the morphological characteristics and mesostructure parameters of the material and the contact force distribution inside the asphalt mixture.