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

MgO–2CaO·SiO 2 –3CaO·SiO 2 refractory compositions incorporated with zircon (ZrO 2 ·SiO 2 ) were obtained by solid state sintering at 1550 °C for 3 h. The effect of different ZrO 2 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 CaZrO 3 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 ZrO 2 was 1.5%. The cold crushing strength increased steadily from 65 MPa to 124.2 MPa. The cold modulus of rupture slightly decreased in the ZrO 2 content range of 0.5–1.5% and then reached 43.2 MPa, whereas the hot modulus of rupture reached its highest value of 4.4 MPa with 1.5% ZrO 2 addition. The highest adherence strength (7.1 MPa) was obtained for 0.5% ZrO 2 addition because the dissolution of CaZrO 3 into the cement clinker increased the viscosity of the clinker and the bonding with the specimen. At high ZrO 2 concentrations (1.0–2.5%), penetration of the clinker into the matrix was hindered by CaZrO 3 , thus resulting in lower adherence strength. [ABSTRACT FROM AUTHOR]