Valorization of a steel plant fly ash in a CMAS glass-ceramic

Stable and inert glasses in the SiO2-Al2O3-CaO-MgO glass-ceramic system were prepared by adding up to 10 wt% of a steel plant fly ash, and subsequently crystallized. Steel waste dust acts mainly on the optical and thermal properties, without modifying the devitrification mechanism. In particular, the role of structure modifiers Fe2O3 and ZnO, the main oxides present in the waste, is to lower the viscosity and refractoriness of the system. Iron, present mainly in tetrahedral coordination in a 3+ oxidation state, confers yellow-brown color to the glasses. As a consequence of heat treatment, pyroxenic glass-ceramics develop with a surface mechanism, as in the CMAS parent system. On the basis of a previous work, the effect of steel waste dust is reasonably comparable to that of pure iron oxide, with the advantage of using an inexpensive raw material with a good environmental impact factor.