Effect of zircon addition on the physical properties and coatability adherence of MgO–2CaO·SiO2–3CaO·SiO2 refractory materials

Abstract

MgO–2CaO·SiO2–3CaO·SiO2 refractory compositions incorporated with zircon (ZrO2·SiO2) were obtained by solid state sintering at 1550°C for 3h. The effect of different ZrO2 contents (0%, 0.5%, 1.0%, 1.5%, 2.0% and 2.5%) on the physical properties and adherence ability to cement clinker were investigated. Specimens were characterized by bulk density, apparent porosity, cold crushing strength, cold and hot modulus of rupture and coatability adherence with the combination of crystalline phase formation (XRD) and microstructural analysis (SEM). The results showed that CaZrO3 was generated in the matrix grain boundaries and triple points, forming direct bonding between MgO and calcium silicate. Densification of the composites was promoted, and the apparent porosity decreased to 8.9% when the content of ZrO2 was 1.5%. The cold crushing strength increased steadily from 65MPa to 124.2MPa. The cold modulus of rupture slightly decreased in the ZrO2 content range of 0.5–1.5% and then reached 43.2MPa, whereas the hot modulus of rupture reached its highest value of 4.4MPa with 1.5% ZrO2 addition. The highest adherence strength (7.1MPa) was obtained for 0.5% ZrO2 addition because the dissolution of CaZrO3 into the cement clinker increased the viscosity of the clinker and the bonding with the specimen. At high ZrO2 concentrations (1.0–2.5%), penetration of the clinker into the matrix was hindered by CaZrO3, thus resulting in lower adherence strength.