Reaction Characteristics of Magnesia–Spinel Refractories with Cement Clinker

The adherence ability of cement clinker on magnesia–spinel refractories is investigated, using a sandwich test, at 1550°C for 30 min under a load of 5.3 kPa. Fractional factorial experiments determine that the silica ratio (SR)—SiO₂/(Al₂O₃+Fe₂O₃) and particle size of raw meal, as well as heating rate, have a significant effect on adherence ability. Microstructural analyses indicate that the adherence ability depends upon reactions between clinker and refractories at high temperature. Only spinel reacts with CaO and 3CaO·SiO₂ from clinker to form n -calcium aluminate (such as 3CaO·Al₂O₃, 12CaO·7Al₂O₃, CaO·Al₂O₃), but there is no reaction between MgO and the clinker. Fine crystalline spinel, evenly distributed in magnesia-based brick, is prone to reacting with lime-containing phases from clinker to form low melting phases and a belite-enriched zone at the clinker/brick interface. This reaction positively contributes to the high adherence on a magnesia?spinel brick. The high content of liquid in clinker with low SR accelerates reactions between spinel and clinker, while a limited reaction occurs at the brick/clinker interface with high silica.