Evaluation of Compressive Strength of Concrete Produced with Rice Husk Ash as Partial Replacement for Cement in Kebbi State

Rice husk ash, a by-product of rice processing, is abundantly available in Kebbi State, North West Nigeria, a major rice-producing area, and its potential as a pozzolanic partial cement replacement offers both economic and environmental benefits for the local construction industry. This study evaluated the compressive strength of concrete produced with rice husk ash as a partial replacement for Portland cement at substitution levels of 0% (control), 5%, 10%, 15%, and 20% by weight of cement. Rice husk ash samples were collected from rice mills in Argungu Local Government Area, processed by controlled burning at 700 degrees Celsius for 2 hours, and characterised for chemical composition and fineness. Concrete cubes were cast, water-cured for 28 days, and tested per BS 1881-116 at 7, 14, and 28 days. Results showed that 10% rice husk ash replacement achieved the highest compressive strength at 28 days (32.8 MPa), exceeding the control mix (31.4 MPa) by 4.5%. Compressive strength declined at replacement levels above 15%, reaching 22.1 MPa at 20% replacement. The improvement at 10% replacement was attributed to the pozzolanic reaction producing additional calcium silicate hydrate gel. The study concludes that 10% rice husk ash replacement is the optimal substitution level for Kebbi State conditions, and recommends its adoption as a cost-saving and waste-reduction strategy in concrete production in North West Nigeria.

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