MgO–C refractories containing various ratios of chemically synthesized alumina/titania nano additives were investigated concerning their physical and mechanical properties, oxidation resistance, and slag wettability. The fired refractories ' bulk density, apparent porosity, cold crushing strength, oxidation index, and closed porosity were evaluated and compared using conventional techniques and X-ray micro-computed tomography (µCT). The results of the physical and mechanical property measurements showed differing trends, with a slight degradation of physical properties and an enhancement of mechanical properties, particularly in the specimens with high alumina content. By comparing the X-ray tomography results concerning the oxidation and corrosion of the refractories with those obtained from conventional methods, the effectiveness of the technique was confirmed, as it allowed for the determination of the oxidation index without sectioning and provided improved analysis of internal corrosion within the samples. On the other hand, although the Archimedes method cannot detect closed porosity, unlike X-ray tomography, it provides more accurate measurements of the physical properties of the refractories. In this study, the conventional method demonstrated superior resolution in detecting pore sizes within the 1–2 μm range, compared to the μCT system employed, which had a resolution limit of 20 μm.