Design, obtainment and properties of glasses and glass-ceramics from coal fly ash

Glasses and glass-ceramics were obtained by mixing up to 50 wt% of Italian or Spanish coal fly ash with other wastes (glass cullet and float dolomite). The behaviour of 10 compositions was investigated by thermal (DTA) and mineralogical (XRD) analysis, microstructural (SEM) characterization, mechanical and chemical measurements. It was verified that the contribution of the alkaline-earth elements in the original composition is fundamental to easily obtain glass-ceramics with a fine microstructure which improves the mechanical properties. Otherwise, with a small addition of Ay ash and without dolomite, very stable glassy materials were obtained that did not exhibit any visible etching either in water or in acid media. Therefore, the combined vitrification/devitrification technique is a suitable methodology for the recycling and exploitation of coal fly ash. (C) 1998 Elsevier Science Ltd. All rights reserved.