Hamazaki et al. (70) investigated the effect of adding preformed spinel on
properties of Al2O3–SiC–C castables used in blast furnace troughs and found
that additions of spinel improved corrosion resistance while having little effect
on mechanical strength. The improved corrosion resistance was attributed to
the high resistance of spinel against the alumina-rich slag formed by dissolution
of Al2O3 from the castables in the original slag. However, the addition of spinel
was found to be detrimental to the spalling resistance as it accelerated oxidation
of SiC. Addition of small amounts (,5 wt%) of MgO to such castables was less
beneficial because the MgO reacted with Al2O3, CaO from the CA cement, and
SiO2 (SiC) to form liquid rather than in-situ spinel