This work addresses the thermodynamic evaluation of different spinel-containing refractory castable compositions in contact with a basic steel ladle slag (CaO/SiO2∼9). The main differences among the castable compositions were the amount of silica fume (0 or 1wt%), the binder source (calcium aluminate cement or hydratable alumina) and the spinel incorporation route (in situ or pre-formed). The interaction of the liquid slag with the refractory was carried out with the help of thermodynamic software (FactSage) and the applied methodology considered the changes in the slag composition due to the interaction with the castable. The theoretical results were compared with the experimental data attained by corrosion cup-tests, pointing out that the thermodynamic calculations were suitable for predicting various aspects observed in the corroded samples by SEM. Therefore, the equilibrium simulations led to parameters that indicated the corrosion resistance trends, complementing the experimental evaluation and reducing further experimental testing.