Mesomechanical characterization of porosity in cementitious composites by means of a voxel-based finite element model

摘要

At the mesoscale, concrete is regarded as a heterogeneous material with two main phases, namely mortar and coarse aggregates. However, the presence of pores at this scale may play an important role on the macromechanical properties of the material. Due to their complex geometry, these mesostructures usually require a large number of discretization elements. In this paper, a voxel-based (volumetric pixel) model is used in order to account for porosity while reducing the number of elements on the characterization of the mesomechanical properties of concrete. In order to validate the voxel model, a comparison to an equivalent tetrahedralized mesh is carried out, showing an important reduction in computational times but with similar results. For such validation, the effect of the voxel size and the consideration of the interfacial transition zone are also accounted for. Finally, uniaxial tension tests are carried out in order to characterize the elastic (i.e. elastic modulus and Poisson's ratio) and fracture (i.e. tensile strength) properties in concrete mesostructures of different sizes (25, 35 and 50 mm). The effect of porosity is analyzed by considering different pore fractions and validated with analytical and experimental results.