Behavior of meso-scale heterogeneous concrete under uniaxial tensile and compressive loadings

Meso-scale modeling approach is helpful for understanding the mechanism of both global nonlinear behavior and local failure pattern of concrete materials and structures. As a typical multiphase composite material, concrete is composed of randomly-distributed coarse and fine aggregates, mortar, interfacial transition zone (ITZ) together with initial pores or defects. The meso-scale mechanical behavior of concrete usually exhibits nonlinear and stochastic characteristics. In this paper, the influence of both distribution and geometrical shape of aggregates, the existence of ITZ, and meshing approach on macro stress-strain relationship, damage evolution and the final failure pattern of concrete are studied systematically. The results indicate that the effect of meso-scale structure of concrete on the nonlinear and stochastic characteristics of macro stress-strain curves and failure patterns is different when the concrete specimen is under tension and compression loadings. Comparatively, the geometrical parameters of coarse and fine aggregates have limited effect on the macroscopic tensile strength, but obvious effect on the post-tension segment and the compressive macro stress-strain curve. Moreover, the damage evolution and failure pattern of concrete under uniaxial tensile and compression are sensitive to the meshing approach. The existence of ITZ affects the tensile and compressive strength of concrete significantly. The statistic characteristics of macro stress-strain curves under both tension and compression loadings from the multi-scale simulation is compared with that from experimental studies and the rationality of the meso-scale simulation approach is validated.