Room temperature mechanical properties of high alumina refractory castables with spinel, periclase and dolomite additions

The mechanical properties of refractory castables at room temperature are critical parameters for selecting suitable operating conditions for the structural design of refractory components. In this work, high alumina refractory castables based on the alumina-rich zone of the Al2O3–MgO–CaO ternary phase equilibrium diagram were prepared by adding synthetic spinel, periclase and dolomite via three processing routes. Bending strength studies at room temperature under several thermal treatments and the analysis of the elastic modulus of the refractories and their matrices point to two different mechanical behaviours. From room temperature to 1000 °C the refractory castables present a pronounced non-linear stress–strain behaviour both in the uniaxial tensile and compressive modes, as a result of damage to the microcrack network. Above 1000 °C the refractory castables begin to sinter owing to a transitory liquid phase, the crystallization of calcium aluminate cement phases (such as CA2 and CA6, for example) and the self-forming spinel phase (refractory castables with periclase or dolomite additions). At higher firing temperatures the sintering process leads a strengthening of the mechanical properties.