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

The effect of substituting calcium aluminate cement with different proporti ons (4, 7, and 9 wt-%) of fine calcined alumina (< 40 mum) on the physico-m echanical properties of self-forming MA spinet castables was studied. The 7 day hydrated samples (cured at 20 degreesC) were fired at different temper atures (800, 1400, 1500, and 1550 degreesC) and their mineralogical composi tion and microstructure investigated using XRD and SEM methods, The densifi cation parameters and cold crushing strength of the fired samples were also measured and cot-related with their mineralogical compositions and microst ructure. The results reveal that castable samples with 9 wt-% fine alumina and fired at 1550 degreesC were found to give improved physico-mechanical p roperties (bulk density = 2.39 g cm(-3), apparent porosity = 7.04%, and col d crushing strength = 95.9 MPa) due to the formation of intertwined three-d imensional hexagonal plate-like crystals of CA(6) that improve the. mechani cal properties.