Study On Mechanical Behavior And Three-dimensional Reconstruction Of Alphalt Mixture Using X-ray Computed Tomography

The macroscopic performance of asphalt mixture has a close correlation with its internal structural characteristics and components behaviors. Thus, it is quite essential to study on macroscopic performance of asphalt mixture from the microscopic perspective. Numerical simulation of mechanical behaviors experiments considering microscopic structure characteristics and its evolution, which combines macroscopic performance with components of asphalt mixture quantitatively, moreover, controls the balance between different mechanical behaviors of asphalt mixture, and saves extensive experiential laboratory test.Firstly, the air voids distribution of three gradations of aggregate was characterized by using X-ray computed tomography and digital image processing technology based on the laboratory compaction methods of fabrication specimens in China. Furthermore, a mathematic model was made to present for describing the air voids distribution internal structure of asphalt mixtures by means of statistical analysis. The results showed that the gradation of aggregate and compaction methods had considerable influence on air voids distribution in the internal specimens, which was found to display symmetrical feature along the depth of Marshall specimen, whereby distribution of air voids in the static compacted specimen is nonsymmetrical along the depth, and the number of air voids on top part of a specimen was bigger than at bottom part. The number of air voids was more bigger and the fluctuations along the depth was more remarkable, the air voids size was almost consistent in static compacted specimens compared with the Marshall specimens in uniform gradation of aggregate. The statistical analysis performed validated the applicability of a two parameters mathematics model for characterizing air voids distribution of asphalt mixture, and the model could quantify the effect of compaction methods and gradation of aggregate on air voids.In addition, according to the theory of viscoelasticity, with the technique of X-ray CT, DIP and FEM, the indirect tensile test and numerical creep test were conducted to two-dimension numerical model of asphalt mixture. The selection method for the location of the optimum test section was proposed through the analysis on the internal structural mechanical response of homogeneous model and heterogeneous model, meanwhile, the location of damage cracking of asphalt mixture and its reasons under the splitting load effect was analyzed. The results showed heterogeneous model simulated creep test accurately as compared with homogeneous model. Different sections along the height direction had no impact on the results of numerical test. Therefore, any section along this direction may become the optimum test section. Variation trend of S11curve and S22curve was identical for two models mentioned above. The maximum compressive stress of homogeneous model appeared on the pivot of the model, the maximum compressive stress of heterogeneous model appeared on the interface of mortar and coarse aggregate, and the compressive stress along vertical path was bigger than the compressive stress along horizontal path, thereby the internal location of damage cracking of asphalt mixture can be concluded on the maximum compressive stress along vertical path.In the end, the reconstruction analysis on three-dimensional numerical model was performed using Mimics software based on X-ray CT, DIP and FEM. Additionally, a comparative analysis was carried out in terms of volume fraction of internal structural components of asphalt mixture specimen and numerical model, then the accuracy of three-dimensional numerical model was verified.