Mineralogical, geochemical, and geotechnical features of lateritic soils from termite mounds in two contrasting savannah areas (central Cameroon) as raw materials for brick making

Termite mound soils (TMS) from humid savannah (HS) and dry savannah (DS) were evaluated as raw materials for compressed earth bricks (CEB) and fired bricks. Mineralogy and major elements geochemistry were performed by X-Ray Diffraction and X-Ray Fluorescence, respectively. Physico-mechanical characteristics of unfired and fired bricks at 900, 950, 1000, 1050, and 1100 degrees C after 7 curing days were evaluated. The studied TMS are made up of quartz, muscovite, anatase, kaolinite, hematite, and goethite. Illite is present in humid savannah while in DS gibbsite appears. These materials are rich in SiO2 (58.96-61.79 wt%), Al2O3 (16.93-18.78 wt%), and Fe2O3 (7.41-10.33 wt%). The TMS from both HS and DS are sandy clay. Those from DS are silty (13%) than those from HS (< 5.7%). Termite mound materials in DS are moderately plastic, while those in HS are highly plastic. Flexural strength values vary between 2.20 and 2.38 MPa for unfired bricks and between 2.41 and 3.26 MPa for fired bricks, respectively at 1100 and 1050 degrees C. Compressive strength values are ranged from 2.01 to 3.50 MPa for unfired bricks and 2.44 (1100 degrees C) to 11.08 MPa (1050 degrees C), with the best values in the DS area. Water absorption and linear shrinkage values are less than 25% and 5%, respectively, in the studied fired and unfired bricks. The physical and mechanical properties of unfired and fired bricks show that the studied TMS can be used for dense brick manufacturing. Materials from dry savannah exhibit better characteristics as construction materials due to relatively high weathering intensity leading to a spread-out particle size distribution, sintering, which promotes densification by reducing the porosity, and the conversion of metakaolinite into primary mullite upon temperature increase.