Influence of firing temperature on selected mechanical properties of alluvial clay blended with a limestone and kaolin mixture

The present study investigated the feasibility of low-energy and low-cost production of ceramic products from widely available alluvial clay in Batchenga, Cameroon, using low firing temperatures. A mixture consisting of 70% kaolin and 30% limestone was prepared and used as an additive in fired alluvial clay bricks. A series of samples was prepared in which the additive made up 5, 10 or 15% of the clay products, and the samples were heated at 700, 750, 800, 850 or 900 degrees C. The raw materials and ceramic products were characterised using x-ray diffractometry, scanning electron microscopy, bulk density, porosity, thermogravimetry and differential scanning calorimetry analysis. The results revealed that products with 10% additive showed improved mechanical performance and densification after heating at all tested temperatures. A compressive strength of 28 MPa was recorded when the product was heated at 800 degrees C. A drastic decrease in performance was observed for all samples heated at above 800 degrees C; this was likely due to the conversion of CaCO3 into CaO, resulting in the appearance of voids within the matrix that weakened the structure. This is in line with the high-water absorption and porosity values recorded. The resultant ceramic products have potential for use in engineering applications.