Numerical Simulation And Performance Studies Of Concrete Based On Material Meso-structures

In mesolevel concrete may be considered as a three-phase composite material, consisting of aggregates, cement matrix and interfacial transition zone(ITZ). Great different mechanical performance appears due to the different composition of those three phases. As such, the macroscopic properties of concrete are dependent on the volume fractions, mechanical properties and interaction of these three phases to great extent. Therefore, the study of the structural characteristics of three phases and their combination is of theoretical and practical significances.The numerical method is employed to simulate the three phases of concrete in this paper. Firstly, the relation between cumulative distribution function and aggregate size are available based on stereological theory. Then, a program in Fortran which can be used to calculate the sizes and locations of aggregates is developed, and the circle aggregate distributions in two-dimension concrete are available. As such, a finite element model based on the meso-structure of concrete is established.Secondly, the finite element method is employed to calculate the steady-state chloride diffusion coefficient. By comparing the numerical results with the experimental results and the numerical results of the cellular model, the model in this paper is verified effective to calculate the steady-state chloride diffusion coefficient. Through further numerical analyses, the effects of the meso-structure parameters on the diffusion coefficient are discussed. The numerical results indicate that the steady-state chloride diffusion coefficient increases with the augment of ITZ thickness and chloride diffusion coefficient, but decreases with the increase of aggregate maximum size.Thirdly, the finite element method is employed to calculate the elastic modulus of concrete based on the numerical model in this paper. By comparing the numerical results with the experiment results, the model in this paper used to calculate the elastic modulus of concrete is verified. The effects of the meso-structure parameters on the elastic modulus are discussed, and the numerical results indicate that the elastic modulus decreases when the thickness of ITZ and the elastic modulus of ITZ increase, but increases when the aggregate maximum size increases, and the poisson's ratio of ITZ almost has no effect on the elastic modulus of concrete.Finally, the finite element method is also employed to calculate the compressive strength of concrete based on the numerical model in this paper. Comparison between numerical results and experimental results shows the effectiveness of the model in this paper. By further numerical analyses, the effects of the meso-structure parameters on the compressive strength are discussed. The numerical results indicate that the compressive strength increases with the enhancement of tensile strength of ITZ and cement matrix. At the same time, the failure process of concrete under compression is discussed.