Evaluation of lateritic soils of Mbé for use as compressed earth bricks (CEB)

This work was carried out on the lateritic soils of Mbé in the Adamawa region of Cameroon. For this study, twenty (20) soil samples were taken from four (04) sites (Kabaa, Ndom, Mbé Norwegian camp, and Nyéssé). To assess their suitability for the production of compressed earth bricks, physical parameters were obtained by geotechnical tests to determine particle size distribution, water content, atterbergs limits, specific gravity, methylene blue value, maximum dry density (MDD), and optimum moisture content (OMC). Chemical and mineralogical properties were obtained by X-ray fluorescence and X-ray diffraction, respectively, followed by the determination of technological parameters (water absorption and mechanical properties) on compressed earth brick specimens. The results show that the studied lateritic soils contain mainly sand (52.8-90.3 wt%) and clay particles (8.4-42.1 wt%), gravel particles are slightly represented (1.1-16.3 wt%). The plasticity index of the studied materials is average (5-38%), about their methylene blue values (1-5), these soils correspond to clayey-silty soils. The materials studied are classified by the USCS as clayey sands/silty clays; according to the Highway Research Board (HRB), they are classified as A-7-5 or A-7-6 clayey soils with group index of 1 for Kabaa, 7 for Ndom, 9 for Mbé Norwegian Camp, and 12 for Nyéssé. These soils are rich in silica (SiO₂, 62.6-78.1 wt%), followed by aluminum (Al₂O₃, 11.8-18.2 wt%) and iron oxides (Fe₂O₃, 3.2-8.1 wt%); other oxides are in lower proportions (<1 wt%). The mineralogical content consists mainly of clay minerals such as kaolinite, illite, smectite (montmorillonite), and non-clay minerals such as quartz, muscovite, biotite, gibbsite, and hematite. The bulk density and mechanical properties of the specimens are within the standard NC 102-115 (2007) of compressed earth bricks (CEB), which recommends minimum compressive strengths of 2 Mpa for unstabilized CEB and 4 Mpa for stabilized CEB. Water absorption of CEB and physical parameters of soils have a significant impact on the mechanical behavior of CEB. According to the test results, Mbe lateritic soils are suitable for engineering applications in the production of stabilized compressed earth bricks.