Bauxite 'red mud' in the ceramic industry. Part 2. Production of clay-based ceramics

Some potential uses of red mud as a raw component in clay mixtures for cera mic bodies production are presented. The influence of increasing amounts of red mud on the forming procedure, sintering and final properties was analy zed. Samples were produced by uniaxial pressing and slip casting. Two diffe rent clays are used as basic materials, the former being currently employed for the production of bricks by extrusion, the second - almost pure Kaolin - for high quality ceramic manufacturing. In both cases the addition of re d mud led to more deflocculated solid-water systems and an increase of the critical moisture content. Mixtures prepared with the first clay and red mu d loads up to 50% were fired at 850 degrees C. The red mud content did not influence the sample porosity while determining a strength decrease attribu ted to the inertness of red mud at the working temperature. Samples produce d using the second clay and red mud (0 - 20%) were fired at 950 and 1050 de grees C. The addition of red mud determined increases of density and flexur al strength which can be accounted for by the formation of a larger amount of glassy phase at higher red mud contents. The results of this work indica te excellent perspectives for using 'red mud' as raw material in mixtures w ith clay for the production of ceramic bodies. (C) 2000 Elsevier Science Lt d. All rights reserved.