Characterization of basaltic rock laterites in Dschang, West-Cameroon: Compressed Earth Bricks (CEB) for low-cost buildings

Abstract

This study reports on the geotechnical characterization of lateritic soils upon basaltic rocks in Dschang, West-Cameroon. Six (06) soil samples from six (06) sites were taken for assessing their suitability in good quality CEB manufacturing. An analytical approach was adopted and consisted of standard physical and mechanical properties including water content, absolute density, Atterberg limits, grain size distribution and Optimum Proctor Modified (OPM). Mineralogical and geochemical contents of the materials were obtained by X-ray diffraction (XRD) and X-ray fluorescence (XRF) respectively. In addition, density, water absorption, abrasion resistance, and dry and wet compressive strengths were determined for manufactured brick specimens. Results indicate that the materials are rich in kaolinite (33–38%), gibbsite (21–27%) and goethite (22–26%) associated to low proportions of smectites (2–7%) and oxides such as hematite, ilmenite, anatase and bohmite. SiO2 (29.57–35.8%), Al2O3 (22.72–26.93%) and Fe2O3 (20.67–27.95%) are the most abundant oxides while basic cations are generally low in the materials (WIP: 2.25–5.89). The absolute density varies from 2.26 to 2.57 t/m3 and could be indicative of higher Fe2O3 contents. The plasticity index (7.80–18.95%) and the liquidity limit (57.80–64.50%) of materials allow their classification as inorganic silt and organic clay with high plasticity and compressibility that are not suitable for the production of CEB. Furthermore, these materials fall out the preferential plasticity domain recommended by Cameroonian standard for CEB. Based on grain size distribution, the studied materials also fall out the sprindle reference of the Cameroonian standard. For improving the characteristics of studied materials, a grain size correction was performed and provided an optimal mixture made up of 75% natural materials and 25% medium sand (0.05–0.5 mm) that is locally available. This is accompanied by considerable variations of consistency parameters allowing to pass from inorganic silt and organic clay to inorganic clay that display appropriate compressibility and plasticity for good quality CEB production. The using of cement at 4%, 6% and 8% revealed a progressive increase of the MDD (1.40–1.77%) and Wopt (12.60–28.39%). Moreover, the density and mechanical parameters of the manufactured specimens increase with the cement content. The density, physical and mechanical properties of the manufactured specimens fall within the Cameroonian standard of compressed earth bricks (CEB). Globally, the lateritic materials of Dschang improved with sand (25%) and Cement (8%) can be suitable for the production of good and low-cost CEB especially as the two additional materials are locally available and accessible.