CLAY SOILS IN MCHINJI: POTENTIAL RAW MATERIALS FOR CERAMIC INDUSTRY

Mchinji district is composed of a thick layer of superficial deposits which include vast dambos, colluvium, and alluvial plains with aplenty clay soils in their numerous valleys. Regardless of its high proportion, clay soils from Mchinji are only exploited for conventional pottery and local ceramic bricks. This is basically because the potentialities of these clay soil have not been evaluated. Up to the present moment, no study that evaluates the potential applications of these clay soils is available.
Ceramic suitability of clays in the selected sites of Mchinji was assessed utilizing empirical diagrams, involving grain size distribution, and chemical composition and by adopting a new approach basing on the methodology of the experimental design. It is found that the particle size distribution contains higher percentages of sand fractions, followed by clay fractions, and the lowest being silt. The chemical composition was found by XRF analysis which showed higher percentages of SiO2, Al2O3, and Fe2O3. The low content in a fluxing agent is indicated by the low contents in Na2O, K2O, MgO, TiO2, CaO, MnO, and P2O5.
The Mchinji clays are distributed in sandy clay loam and sandy clay in the grain size distribution diagram. These clays have ceramic suitability of checker bricks (perforated bricks) and clay roofing tiles. Taking into account the chemical composition, the clays have the suitability of red stoneware.