Damage evaluation of two alumina refractory castables

The accumulation of damage by thermal treatment and its development under uniaxial loading–unloading cycles performed at room temperature has been evaluated for two alumina based refractory castables; an ultra low cement content bauxite material (Bau-ULCC) and a low cement content andalusite material (And-LCC).Both castables exhibit notable damage with a level related to the firing temperature. The tensile behaviour is characterised by an elastic domain at the beginning of loading followed by a non-linear evolution up to the peak. In addition to the non-linearity of the stress–strain curve, the evolution of the loading–unloading cycle characteristics confirms the development of diffuse damage within the materials. In order to better understand the damage behaviour of the studied materials, the evolution of various parameters in relation with to the extent of damage has been analysed. These parameters are Young's modulus measured at the beginning of each unloading step Euni, the residual strain after each cycle εresi and the associated consumed energy during the test (Whi).The parameters extracted from the stress–strain curve reveal some interesting analogies between the two materials. In particular, it seems that a parameter DTh, which quantifies the damage resulting from the thermal treatment, plays a major role in the mechanical behaviour until failure in a similar way for the two castables. It appears that the origin of damage in the two studied materials mechanically loaded after heat treatment is mainly thermal.