3D Microstructural Virtual Design Of Asphalt Mixture Based On The Aggregate Morphology

With the rapid development of computational graphics and images technology,microscopic numerical simulation of asphalt mixture is widely used in the analysis and prediction of pavement performance.The accurate construction of mixture microscopic model is the premise of reliable simulation,among which,as the component with the largest proportion of mixture,the morphology and spatial distribution of aggregates have a important influence on the microscopic mechanical response of mixture.Based on the X-ray Computed Tomography(CT)images of the real aggregates,this paper the real aggregate is three-dimensional(3D)reconstructed,and obtained the three-dimensional solid model of the aggregate,completed the quantification and adaptive classification of the three-dimensional morphological characteristics of the aggregate,and based on this,constructed the aggregate model database,and realized the virtual design and molding of the asphalt mixture.The specific research work is as follows:(1)The three-dimensional morphological characteristics of aggregates and their quantitative methods were proposed.Based on the three-dimensional solid model of aggregate,the characterization indexes of sphericity,form dimension and angularity of aggregate are proposed.Then the algorithm is developed to obtain the minimum bounding sphere and the minimum bounding box of the aggregate model and calculate the sphericity and form dimension of the aggregate.On the basis of this,the triangular surface slices were quadratic clustered to obtain the plane cluster assembly,in order to quantify the aggregate angularity.The results of virtual measurement of sphericity,form dimension and angularity of 11 aggregates show that the method can accurately measure the three-dimensional shape characteristics of aggregates.(2)Adaptive classification method for angularity and texture of the aggregates is presented.First of all,the aggregate surface discrete into a triangular mesh,and optimize the triangles in the clustering algorithm,and improved the aggregate surface close to the plane area clustering for a plane and fitting out of the plane equation for clusters of clusters,as a reference plane,based on the planar triangles in clusters within the vertices to the change of the reference plane distance,definition and quantitative index of the aggregate surface texture;Finally,from the macroscopic statistical level and the microscopic data distribution level,the adaptive classification of aggregateangularity and texture is realized.The microscopic classification of 275 aggregates was achieved.It can be seen that,compared with the traditional classification method,this method proposes the quantitative index of aggregate angularity and texture based on metric unit,which is helpful to further study the correlation between aggregate shape characteristics and the micro-mechanical properties of asphalt mixture.(3)The virtual design and compaction method of microscopic structure of asphalt mixture are put forward.Firstly,the real aggregate database of more than 2000 aggregates was constructed.Aggregate gradation,spatial distribution,orientation,sphericity,form dimension,angularity,texture,aggregate content,asphalt content,voids content and other indicators were used as design parameters,and aggregates in accordance with shape parameters and volume parameters were selected from the database as aggregate components of the mixture.Then the spatial distribution of aggregate is determined according to the spatial position and orientation parameters.According to the content of asphalt mortar and voids,the virtual formation of the micro-structure of the mixture is realized by Boolean operation.This method provides an effective scheme for virtual design of micro-structure of asphalt mixture and is beneficial to further study the scientific relationship between design index and mechanical properties of asphalt mixture.