Optimization of the sintering process of raw material wastes

The analysis of the mineralogical composition of most rock wastes shows the presence of a high percentage of minerals with SiO2 and Al2O3, which could be used as raw materials for ceramic products. The main objective of this work is to recover wastes from one primary rock industry, utilised in the p roduction of tiles and flooring, for the manufacturing of ceramics, using p owder technology: pressing and sintering. The sinterability of the powders, with and without previous heat treatment, was studied in order to obtain a product with the best performance. Powders from different quarries after b eing uniaxial pressed at 40 MPa, or isostatic pressed at 170 MPa and sinter ed within the range 1150-1170 degrees C present properties as follows: (a) hardness: 5.5-7.5 GPa; (b) transverse rupture strength: 55-94 MPa; (c) abra sion and erosion wear better than that of bulk to be drawn materials, and ( d) water absorption of less than 0.5%. The results allow the conclusion tha t these wastes can be recovered and used successfully in the manufacture of ceramics with better performance than traditional tiles and flooring. (C) 1999 Elsevier Science S.A. All rights reserved.