In second generation MgO–MA castables, either fused or sintered spinel clinkers with
different stoichiometry can be used. Rigaud et al. (33) compared the effect of
MgO-rich (MR66) and two Al2O3-rich spinels (AR78 and AR90) on the Modulus of Rupture (MOR) and corrosion resistance of MgO–MA castables, and
found that castables using MgO-rich spinel had slightly higher MOR and better
corrosion resistance than those using AR78 and AR90. The better corrosion
resistance using MgO-rich spinel is attributed to the higher MgO content, as discussed by Zhang and Lee (34), since the solubility of MgO in silicate slag is
lower than Al2O3. Bi et al. (35) verified that increasing Al2O3 –MgO ratio in
MgO–MA castables generally leads to better slag penetration resistance but
poorer corrosion resistance.