CONICET | Buscador de Institutos y Recursos Humanos

Ceramic industry has known a considerable product and process innovation, that fostered the development of novel typologies and applications implying new technological requirements for ceramic raw materials. The latest innovation in tilemaking is particularly stressing properties like powder flowability, ability to densify during dry pressing and to toughen green tiles. Thus the technological requirements of ball clays are ever stricter in terms of plasticity, dispersion in water, rheological behaviour, workability in the green state, refractoriness and firing colour. This work is aimed at improving the technological performances of conventional ball clays by taking as benchmark the highest quality raw materials on the market. A case study was undertaken on ball clays from Patagonia (Argentina) which offer a wide range of technological behaviour and mineralogical composition. Different clays were selected and the main characteristics in terms of mineralogical and chemical composition, particle size distribution, rheological behaviour, specific surface plasticity, methylene blue index, colour and ceramic behaviour were determined. Appropriate mixtures, designed adding highly plastic materials (rich in expandable clay minerals) to moderately plastic clays were targeted on the benchmark. Porcelain stoneware formulations, containing improved ball clay mixes, were experimented at a laboratory scale, simulating the industrial tilemaking process. Technological properties and behaviour were measured on both semi-finished and finished products and compared with reference bodies made up with the benchmark. The improved ball clays behave in porcelain stoneware bodies like the best raw materials currently utilized, although modest changes of technological behaviour occur in the mechanical properties, water absorption and whiteness of the fired products.