Use of thermally treated bentonitic clay in the formulation of ceramic tiles

Bentonitic clays are commonly available in several regions where ceramic tiles are produced. In spite of this availability, their use in the ceramic industry for the formulation of ceramic tile bodies is limited to contents below 10% w/w. The main reason for the restriction of its use is that bentonite induces the flocculation of water clay dispersions obtained by wet milling. In this paper we report the use of calcined (973 K) calcium bentonite to formulate a wall tile ceramic body with bentonitic clay content as high as 40% weight. The processes during firing were different from those of conventional formulation with kaolin. Thus a better control of dimensional characteristics of pieces during firing was achieved. Technological parameters of pieces formulated with bentonite (contraction, rupture module, apparent density, water absorption and expansion by moisture) fulfilled the industrial requirements for wall tile production. The substitution of ball clays by thermally treated bentonite has economical benefit.