Mode III fracture toughness testing and numerical modeling for aerated autoclaved concrete using notch cylinder specimen subjected to torsion

Abstract The aerated autoclaved concrete [AAC] is a widely used material in civil engineering for constructing masonry elements. It has excellent insulation and strength properties. The soft porous building materials during exploitation of engineering structures are subjected to various types of loading. The stress state in masonry elements are generated by thermal conditions, shrinkage, weight of other structural elements and service loads. In specific cases, the failure of these materials can be occurred due to out-of-plane sliding or mode III deformation. However, the mode III fracture toughness (KIIIc) of such materials has rarely investigated. In this research using a circumferentially notched cylinder sample subjected to torsion moment, the mode III fracture behavior of AAC (as a model brittle and soft building-material) is investigated experimentally. The KIIIc value was obtained equal to 8.201 ± 0.549 kPa m0.5 for the AAC with a nominal density of 700 kg/m3 that is significantly smaller than the mode I fracture toughness (KIc) of this material demonstrating the high risk of fracture under tear type loads. The laboratory tests were re-analyzed numerically. The results of the conducted analyses indicate that the numerical predictions of AAC under torsional loading conditions and based on the fracture properties assessed in the bending test allows predicting the mode III fracture toughness of AAC with an acceptable agreement.