Multi-scale characterization of lateritic soils from the Adamawa region of Cameroon and their suitability for sustainable compressed earth block production

This study presents a comprehensive multi-scale investigation of lateritic soils from Dir (Adamawa, Cameroon) to assess and optimize their potential for producing compressed earth blocks (CEB) and cement-stabilized earth blocks (SEB). Twenty soil samples collected from four sites underwent geotechnical, mineralogical (XRD, IR), chemical (XRF), and microstructural (SEM-EDS) characterization, alongside mechanical and durability testing of fabricated blocks. The soils exhibit suitable particle size distributions and plasticity (PI = 8–12%), with a mineralogy dominated by quartz and kaolinite, reflecting advanced weathering (CIA > 96%). A multivariate Principal Component Analysis identified four orthogonal factors controlling soil behavior: texture/compaction, plasticity/clay activity, organic-mineral balance, and natural moisture content, providing a scientific framework for formulation. While unstabilized CEBs showed moderate compressive strength (1.47–3.91 MPa), cement stabilization (4–12%) significantly enhanced performance, achieving strengths up to 9.79 MPa in compression and 4.38 MPa in flexure. Notably, nonlinear regression models revealed a parabolic relationship with cement, identifying a minimum effective threshold near 2% and quantifying the distinct effects of organic matter (beneficial in flexure, detrimental in compression). Microstructural analysis confirmed progressive matrix densification and C–S–H formation with increasing cement content. The blocks also demonstrated favorable hydric properties (bulk density: 1.79–1.99 t/m³; porosity: 25–30%; water absorption: 11–15%). This work moves beyond empirical characterization by establishing predictive models and microstructure-property relationships, demonstrating the viability of Dir’s laterites for sustainable construction and providing a rational basis for optimizing local earth-based materials in line with SDGs 9, 11, and 13.