Performance of Clay-Based Earth Bricks with Varying Sand Content: A Case Study of Lendi Soil, Douala

Abstract

This study evaluates the influence of sand content on the mechanical behavior and water resistance of compressed earth bricks (CEBs) manufactured from Lendi clay (Douala, Cameroon). Twenty-seven specimens (prismatic and cubic) were produced with three formulations: 0%, 30% and 60% sand substitution by dry mass, compacted at 2.5 MPa and cured for 7, 14 and 28 days. Raw material characterization included particle size distribution, sand equivalent, Atterberg limits, bulk density and Proctor compaction. The clay displayed a liquid limit of 44.07%, plastic limit of 35.23% and plasticity index of 8.84%; optimum moisture content was 15.9% and maximum dry density 1.24 g·cm⁻³. Mechanical testing showed that pure-clay bricks achieved the highest compressive and flexural strengths at all ages (up to ≈ 1.98 MPa and 0.56 MPa respectively). Although the 30% sand mix exhibited marginally higher early compressive strength (7 days), strength decreased substantially by 28 days. Capillary absorption tests revealed an important distinction: while 0% sand bricks exhibited continuous water uptake, they retained cohesion during immersion; conversely, 30% and 60% sand bricks disintegrated into a slurry within seconds of immersion, evidencing severe loss of internal bonding. These findings indicate that, for this highly plastic tropical clay, sand acts primarily as a microstructural diluent that undermines long-term cohesion and durability despite short-term packing benefits. The study underscores the need for locally tailored formulations or stabilizers when designing durable CEBs for humid tropical climates.