Evaluation of clay soils from Manjacazi district (Mozambique) as potential raw material for the ceramic industry

The Manjacazi district is composed of vast alluvial plains with aplenty clay soils in their numerous valleys. Regardless of its high proportion, clay soils from Manjacazi 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. This study aims to evaluate the suitability of the Manjacazi clay soils as industrial mineral resources for the ceramics industry by studying their ceramic properties as well as drying and firing behaviours. The ceramic properties of the fired clay briquettes of Manjacazi were interpreted by linear shrinkage, compressive strength, and water absorption. The Manjacazi clays are distributed in loam, clay loam, clay, sandy clay loam, and sandy loam in the grain size distribution diagram. Besides, they are low plastic organic silts with low compressibility, medium plastic inorganic silts with low compressibility, and high plastic inorganic silts with high compressibility. Linear shrinkage was generally high and increased slightly with firing temperature. In contrary, their water absorption and compressive strength decrease with firing temperature. Therefore, these clays have ceramic suitability for the manufacture of walled floor blocks, clay roofing tiles, checker bricks, and solid bricks.