The impact of bonite aggregate on the properties of lightweight cement-bonded bonite-alumina-spinel refractory castables

The lightweight bonite-alumina-spinel (CA6-Al2O3-MA) refractory castables with bonite aggregate and different spinel sources (pre-formed and in situ formation) were prepared in this study. The phase composition, microstructural features, and mechanical and thermo-mechanical properties of CA6-Al2O3-MA castables treated at various temperatures were investigated by techniques including X-ray diffraction (XRD), scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDS), three-point bending method, and thermal shock test. The results indicated that the incorporation of bonite aggregate had a positive influence on the strength, thermal shock resistance and slag corrosion resistance. It especially decreased the thermal conductivity and had a slightly negative influence on the refractory under load and slag penetration resistance of the castables. For the in situ spinel-containing castable, the formation of in situ spinel with finer particle sizes and acicular CA6 grains led to higher overall volume expansion, resulting in higher thermal expansion (∆L/L0), linear change and the apparent porosity of castables. Also, the heat insulation, thermal shock and slag penetration resistance of castables with in situ spinel improved, while the strength, displacement, refractory under load and slag corrosion resistance decreased sharply.