Effect of SiC powder content on lightweight corundum-magnesium aluminate spinel castables

Highlights: • New lightweight corundum-spinel castables (LCSC) have been prepared. • The effect of SiC powder content on microstructure and properties was investigated. • The LCSC with 1.9 wt% SiC powder showed the best properties. This study investigates five lightweight corundum-magnesium aluminate spinel castables (LCSC) which consisted of porous corundum-spinel aggregates and matrices with 0–2.8 wt% silicon carbide (SiC). The effect of the SiC powder content (SPC) in the matrix on the microstructure, strength, thermal conductivity and slag resistance was analyzed by XRD, SEM and EDS as well as by the thermochemical software FactSage. The addition of SiC powder resulted in a significantly improved interface bonding between the porous aggregates and the matrix enhancing the strength and slag resistance. Whereas the thermal conductivity at 300 °C and 500 °C remained unchanged, it increased significantly at 800 °C and 1000 °C. The optimized LCSC contained 1.9 wt% SiC powder which combined a suitable apparent porosity (32.5%), a low bulk density (2.41 g/cm³), a high flexural strength (17.62 MPa), a high compressive strength (100.76 MPa), a low thermal conductivity (0.978 W/m·K, 1000 °C) and a high slag resistance.