Strength modeling of brittle materials with two- and three-dimensional pore structures

Strength under compression of highly porous aerated autoclaved concrete was modeled by means of Finite Element Analysis of the porous microstructure. The complex microstructure of aerated autoclaved concrete is characterized by three hierarchical levels of pores. Strength and failure behaviour is controlled by large artificial air pores (AAP) with a mean diameter of 0.5–3 mm. Stress distribution in the brittle matrix material under external load was calculated by FEA for different pore arrangements. Based on the stress distribution multiaxial Weibull Theory was used to predict failure probability with regard to the porous microstructure. Two- and three-dimensional ordered pore arrangements show an exponential decrease of strength with porosity in the range of 0–0.4, depending on the Weibull parameter m of the matrix material. Strength vs. porosity relation differs significantly for pore structures with simple cubic and body centered cubic pore arrangements. The compatibility of two-dimensional with three-dimensional models is examined.