Hydrogarnet formation in the system lime-alumina-silica-water

Abstract

Glasses of the composition of grossularite and similar glasses poorer in silica were t reated hyd rothermally, a nd t he composition of t he resulting hydrogarnets was estimated from t he unit cell size as calculated from X-ray powder pat terns. The silica content of the hydro- garnets in creased continuously with the temperature of formation, approximating t ha t of grossula ri te a t 8000 C. When mixt ures of lime, alumina, and silica, either as such or in various states of combinat ion, were treated in the same manner as t he glasses equilibrium was not at ta ined even after several weeks. At times as many as three d istinct'hydrogarnet composit ions were found t o coexist. The equilibrium temperature for the hydrot herma l decomposit ion of 3CaO·Ah03·6H20 to 4CaO·3Ah03·3H20 plus Ca(OH)2 was found t o be between 2200 and 2260 C. Hydroga rnets containing increasing amounts of s ilica underwent t he same type of decomposition at progressively higher temperatures. 1.