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 degrees 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 spine] reacts with CaO and 3CaO center dot SiO2 from clinker to form n-calcium aluminate (such as 3CaO center dot Al2O3, 12CaO center dot 7Al(2)O(3), CaO center dot 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.