Performance Evaluation of Fonio Chaff, Eggshell Powder, and Charcoal Ash as Partial Cement Replacement in Compressed Stabilised Earth Bricks

Rapid urbanisation, natural resource depletion, and the high environmental impact of Portland cement production have intensified the search for sustainable, locally sourced construction materials. Compressed stabilised earth bricks (CSEBs) present a promising alternative due to their low energy demand and adaptability to local soils. This study investigated the strength performance of CSEBs incorporating agricultural by-products (Fonio chaff, Eggshell powder, and Charcoal ash) as partial cement replacements at 5% and 10% levels using a true experimental research design. The existing scientific evidence was reviewed to understand how these bio-derived additives influence the physical and chemical behaviour of stabilised earth matrices. The laboratory testing assessed physical properties. The compressive strength at different curing ages, water absorption, and workability. The materials exhibited specific gravity values of 1.4-2.7, bulk densities between 300-1700 g/cm3, and moisture content of 16.20-21.21%. The compressive strength finding showed performance improvements at both 5% and 10% replacement levels. Eggshell powder and charcoal ash demonstrated the greatest strength gains, with 10% replacement producing the highest strength across curing periods. Fonio chaff showed moderate improvement, particularly at 5% replacement. Water absorption varied notably, with eggshell powder mixes recording the lowest strength, while fonio chaff mixes showed a higher absorption rate. The workability remained within acceptable ranges for all mixes. These findings supported the potential of agricultural waste as eco-friendly cement substitutes in CSEBs, by converting and utilising locally available agricultural by-products into value-added construction materials. This approach advances circular-economy principles and offers a pathway toward low-carbon, affordable, and resilient housing solutions, particularly in Nigeria.