Mineralogy, chemistry, and plasticity of the raw clay materials,
outcropping in different Tunisian domains were studied. These clays constitute
the only mineral resource of the ceramic industries in Tunisia, and are
exploitable at eight quarries. Powder X-ray diffraction analysis revealed that
illite and kaolinite are the major mineral phases. However, other clay minerals, such as illite/ smectite mixed-layer, and
chlorite are also present. The associated minerals detected in powdered
materials are: quartz, calcite, feldspar and, dolomite. These raw materials are
marly clays with 6% - 14% CaO, represented essentially by calcite; they show
the greatest relative amount of Na2O K2O (~3.5%) and
iron-oxide (~6%). The plasticity index and liquid limit of crude samples do not
exceed 22% and 42%, respectively. This indicates that these clays belong to the
zone of illitic clays, classified in the low to moderate plastic domain. The
analysis will be used to find appropriate applications for traditional ceramic.
In addition, this paper shows that the ceramic defects observed in the pieces
manufactured from these Tunisian clays are lamination, cracks, and lower
mechanical and bending strength. Some solutions are assured to avoid these
ceramic defects.