Performance evaluation and application framework for sustainable brick manufacturing using rice husk ash

This study investigates rice husk ash as a partial replacement for clay in sustainable brick manufacturing. Seven brick compositions were developed with rice husk ash contents of 0%, 5%, 7%, 9%, 11%, 13%and 15% by weight. The bricks were evaluated through compressive strength testing, water absorption analysis, shrinkage measurement and efflorescence examination. Results show that bricks containing 5% rice husk ash achieved compressive strength of 4.82 MPa, representing only a 5.3% reduction compared to conventional clay bricks. This performance exceeds the minimum requirement of 3.50 MPa specified in NBC 109–1994 for structural applications. Water absorption increased progressively from 22.81% in pure clay bricks to 38.65% at 15% rice husk ash content. This increase creates opportunities for specialized applications in permeable infrastructure and thermal insulation systems. Shrinkage decreased by 51.3% at maximum rice husk ash content due to the non-plastic nature of ash particles. This significant reduction enhances dimensional stability during manufacturing and addresses a critical quality control challenge in the Nepalese brick industry. The study establishes a practical application framework that categorizes rice husk ash bricks into three performance tiers. Bricks with 0–5% rice husk ash are suitable for load-bearing structural applications. Compositions with 5–7% rice husk ash meet requirements for non-load-bearing partitions. Bricks containing 9–15% rice husk ash are appropriate for permeable pavements and thermal insulation systems. These findings demonstrate that rice husk ash integration represents a technically viable and environmentally beneficial approach that transforms agricultural by-products into construction materials while advancing circular economy principles in the building materials industry.