Comparative assessment of calcium aluminate cement and potassium-metakaolin-based geopolymer as binders in high-alumina refractories

Abstract This investigation demonstrated the effects of calcium aluminate cement’s total or partial replacement with a potassium-metakaolin-based geopolymeric binder (K-GP) in high-alumina castables. Experimental measurements were conducted to analyze the produced samples’ processing, microstructure, and properties after curing and firing (800-1400 °C). The results highlighted K-GP as a viable binder option for producing cement-free refractories. After firing at 1100-1400 °C, the improved properties of geopolymer-bonded refractories were attributed to their complex resultant microstructure, comprising alumina particles strongly adhered by a glassy phase and contained randomly distributed clusters of kaliophilite and/or leucite grains within the ceramic matrix. After firing at 1250 °C, the samples exhibited a promising set of properties: high thermal shock resistance, modulus of rupture of 17.01 MPa, Young’s modulus of 67.15 GPa, porosity of 16.85%, density of 2.87 g/cm³, and linear shrinkage of 0.33%. These properties are suitable for applications at intermediate temperatures (i.e., petrochemical and non-ferrous industries).