Characteristics and industrial application of the Lower Cretaceous clay deposits (Bouhedma Formation), Southeast Tunisia: Potential use for the manufacturing of ceramic tiles and bricks

• The Lower Cretaceous deposits from Southern East Tunisia are illitic–kaolinitic rich clays.
• The Bouhedma Formation deposits have been tested in ceramic manufacture.
• The Bouhedma clay mixtures give ‘Cottoforte’ and ‘Red stoneware’ type products.

The assessment of the possible applications of the Lower Cretaceous clays, belonging to the Bouhedma Formation, as raw materials in ceramic applications, was performed on the basis of the mineralogical, chemical, thermal and physical properties. The characterization was carried out by Atomic Emission Spectrometry (ICP-AES), X-ray diffraction (XRD) and Thermogravimetric–Differential Thermal Analysis (TG-DTA) techniques. Physical properties were determined by specific surface area, particle size distribution, dilatometry and consistency limits. The data showed that these materials were composed of illite, kaolinite, and chlorite and mixed layered clay minerals in variable amounts. Quartz, feldspars and dolomite were also detected. The plasticity presented a medium value; suggesting that these clays are plastic. The firing shrinkage and the expansion were limited. Mixtures of clays were prepared from the Bouhedma clays, and heated to the desired temperature to obtain different earthenware products. Semi-industrial processed mini-bricks revealed promising characteristics and were visibly free of defects. Ceramic tiles had a bending strength complying with the required standards. Therefore, the technological properties of the investigated deposits make the Bouhedma clays suitable for the production of high-quality common bricks.