Assessment of the suitability of clay materials from the Sudano-Sahelian zone of Cameroon for brick production

This study evaluates the suitability of six clayey materials from artisanal brickmaking sites in the soudano-sahelian zone of Cameroon for use as raw materials in fired brick production, which have not been previously tested. Their mineralogical and geochemical compositions were determined respectively by using X-ray diffraction and Fourier transform infrared spectrometry as well as by X-ray fluorescence spectrometry. The physical properties of the clays were determined through Atterberg limit test and laser particle-size distribution analysis. Thermal analyses (TGA/DSC) were conducted to survey the behavior upon heating of the clays. The main clay minerals identified in the clayey materials are kaolinite, illite, and smectite (montmorillonite) in variable proportions, along with varying amounts of quartz, K-feldspars, and plagioclases as associated minerals. All of the samples are mainly composed of SiO₂, Al₂O₃, and Fe₂O₃, with variable amounts of K₂O, Na₂O, CaO, and MgO, which are regarded as fluxing oxides. High concentrations (4.5–8.3%) of these oxides in the MPG, MPZ, and MPZL samples point out a high fluxing content, capable of achieving adequate densification at relatively low firing temperatures. In contrast, the MPB, MPD, and MPDB samples contain low proportions of fluxing oxides (≤ 2.5%), that may cause insufficient densification. The clays studied are characterized by a high proportion of sand fraction, with moderate proportions of silt and clay fraction, resulting in a low plasticity even for those with a high content of swelling clay minerals. All of the clayey materials undergo progressive thermal transformations with increasing temperature, beginning with dehydration at low temperatures (up to 100 °C), followed by dehydroxylation between 400 and 600 °C, decomposition of carbonates between 700 and 900 °C and finally a structural reorganization and recrystallization of newly minerals at temperatures above 900 °C. These clay materials (MPZL and MPDB) have good properties for brick production, while MPD and MPZ have acceptable properties but require extrusion. However, MPG, can be used for fired brick production but requires optimum extrusion. Furthermore, MPB, with a high plasticity index, requires the addition of a degreaser for use in the production of fired bricks.