Physical, chemical, and mineralogical characterization of Boula-Ibi and Indjode-Bidzar clays (northern Cameroon) for use as calcined cementitious materials

This study focused on the physico-chemical and mineralogical properties of clays from Boula-Ibi and Indjode-Bidzar (North Cameroon) for potential usage as a partial replacement in cement. Particle size distribution, X-ray diffraction, X-ray fluorescence spectrometry (XRF), Brunauer Emettand Teller (BET) model for the specific surface area, thermogravimetric analysis, and mechanical tests were used to determine the quality of the raw material. The results of the particle size analysis revealed that the size of most materials is in the range of clayey sands. The proportion of clayey sand observed in the materials is essential and constitutes the source of silica and alumina. These minerals contributed to the formation of calcium silicate hydrates (CSH) and calcium aluminosilicate hydrates (CASH), which have properties that are highly valued in cement production. The results of the mineralogical analysis showed a mineralogical assemblage consisting mainly of kaolinite, smectite, and quartz. Other minerals such as calcite, hematite, vermiculite and goethite are accessory. This mineralogical composition of the materials studied demonstrated the exceptional quality of the clays through the minerals most sought after by the cement industry, such as kaolinite and quartz. Chemically, the clays studied contain 48.02–69.77% of SiO2, 12.39–21.83% of Al2O3 and 3.44–9.77% of Fe2O3. Alkali and alkaline-earth oxides (CaO, MgO, K2O and Na2O) are relatively rare.This confirms the presence of the minerals observed by XRD. The specific surface areas of the clays range from 11.16 to 62.99 m2/g. This corresponds to a mixture of several types of clay minerals such as kaolinite, smectite, and illite identified by XRD. These parameters are important because they promote chemical interactions between the constituent elements of clay materials while enhancing substitution in cement production. Tests replacing ordinary cement with calcined clay revealed that compressive strength decreased from 26.4 to 15.12 MPa (MK-In-01), 26.4–17.23 MPa (MK-BO-02), and 26.4–18.03 MPa (MK-BO-04), respectively, and are inversely proportional to the temperature gradient. This is due to the presence of montmorillonite that has not been completely transformed and which could limit the pozzolanic activity of the different mixtures, thus affecting the development of strength. Collectively, the physico-chemical, mineralogical, and thermo-mechanical qualities indicate that both clays are appropriate raw materials for cement production. Expanding research on clays in the northern region may substantiate the utilization of these materials by cement factories.