Assessing white clays from Tabarka (Tunisia) in the production of porcelain stoneware tiles

Abstract

In recent times, there has been an increasing demand for white-firing clay materials in ceramic tile production, due to a progressive shift towards porcelain stoneware bodies. Furthermore, the recent geopolitics events have challenging the industries possibilities to satisfy their clay demand for porcelain stoneware production by well-established commercial channels. In this framework, there is a need to expand the reserves of ball clays, especially in Mediterranean countries, which have a low frequency of clay deposits suitable for the production of porcelain stoneware. For this purpose, the Tabarka clays in Northern-West of Tunisia have been studied. They have already been investigated in the literature for the production of various types of ceramic tiles (but not porcelain stoneware). The technological behaviour of bodies, containing 40% clay, was assessed by simulating the industrial tile manufacturing process on a laboratory scale. Tabarka clays (TC) were compared with high and low plasticity ball clays (which define a reference range for the raw materials currently used). TC exhibit a fine grain size distribution and plasticity approaching the most plastic ball clays currently used. The behaviour of the bodies containing TC during grinding, pressing, and drying is fully suitable, with values of the technological parameters that lie within the reference range. Using TC, a slightly higher temperature was necessary during firing to get the desired water absorption (<0.5%). This was due to the kaolinite-rich composition of TC that is more refractory than ball clays taken as reference, which contain illite and illite-smectite interstratified terms, along with kaolinite. The properties of fired bodies based on TC fulfil the technical requirements for porcelain stoneware tiles.