Assessment of Rice Husk Ash as a Supplementary Cementitious Material in Concrete

Cement production is responsible for nearly 8% of global CO₂ emissions, making it one of the construction industry's most pressing environmental challenges. Rice Husk Ash (RHA), an abundant agricultural by-product with high silica content, has been identified as a promising supplementary material capable of addressing this issue. This study investigates RHA's potential as a partial replacement for cement in concrete, with a superplasticizer added to maintain workability. Evaluations of workability, compressive strength, split tensile strength, and water absorption were carried out at replacement levels of 0%, 5%, 10%, and 15%. The slump test showed that workability decreased as RHA content increased. Testing was conducted on M20-grade concrete with a water-cement ratio of 0.45, using 200 ml of superplasticizer per 50 kg bag of cement. After 28 days, compressive strength and split tensile strength at 5% and 10% RHA replacement were close to those of conventional concrete, and water absorption remained within acceptable limits. RHA-modified concrete with 5% to 10% replacement therefore shows strong potential for practical use in construction, offering a sustainable approach that also facilitates in reducing the carbon footprint of cement production.