Improvement of physico-mechanical properties of self-forming MA spinel castables

Abstract

The effect of substituting calcium aluminate cement with different proportions (4, 7, and 9 wt-%) of fine calcined alumina (<40 µm) on the physico-mechanical properties of self-forming MA spinel castables was studied. The 7 day hydrated samples (cured at 20°C) were fired at different temperatures (800, 1400, 1500, and 1550°C) and their mineralogical composition and microstructure investigated using XRD and SEM methods. The densification parameters and cold crushing strength of the fired samples were also measured and correlated with their mineralogical compositions and microstructure. The results reveal that castable samples with 9 wt-% fine alumina and fired at 1550°C were found to give improved physico-mechanical properties (bulk density = 2·39 g cm^-3, apparent porosity = 7·04%, and cold crushing strength = 95·9 MPa) due to the formation of intertwined three-dimensional hexagonal plate-like crystals of CA₆ that improve the mechanical properties.