Investigation of Concrete Mix Design Optimisation Using Rice Husk Ash as Partial Cement Replacement in Kebbi State

Rice husk ash, an agricultural by-product abundantly available in Kebbi State, North West Nigeria, has demonstrated pozzolanic properties that make it a potential partial cement replacement material, offering cost and environmental benefits for local concrete production. This study investigates the effect of rice husk ash as a partial cement replacement on the workability and compressive strength of concrete in Kebbi State. Rice husk ash was sourced from rice mills in Argungu LGA, processed by controlled burning at 700 degrees Celsius, and used to replace Ordinary Portland Cement at 0, 5, 10, 15, and 20 percent by weight in a standard M25 concrete mix. Workability was assessed by the slump test, and compressive strength was measured on 150mm cubes at 7, 14, 28, and 56 days of water curing. Results indicate that workability decreases with increasing rice husk ash content, with slump reducing from 82mm at 0 percent to 47mm at 20 percent replacement. Compressive strength at 28 days peaks at 10 percent replacement (28.6 N/mm2) compared to 26.4 N/mm2 for the control mix, representing an 8.3 percent strength improvement. Replacement levels above 15 percent result in strength below the target M25 specification. The study concludes that 10 percent rice husk ash replacement offers the optimal balance of strength improvement and cement reduction, recommending its adoption for structural concrete in agricultural communities of Kebbi State to reduce construction costs.

Keywords: rice husk ash, cement replacement, concrete strength, pozzolanic material, Kebbi State