Development of Sustainable High-Strength Fired Clay Bricks Using Rice Husk Ash

The increasing demand for bricks has raised environmental concerns related to natural clay depletion, land degradation, and agricultural waste disposal. To address these challenges, this study utilizes rice husk ash (RHA) as a sustainable partial replacement for clay in fired clay bricks. Brick mixtures were casted with varying RHA dosages (up to 80%), and the effect of 2% lime addition was also examined. Mixtures were fired at 1000 °C and 1200 °C and were tested for compressive strength, flexural strength, and water absorption. Microstructural and mineralogical characteristics were investigated using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). At 1000 °C, increasing RHA content and lime addition increased porosity and reduced mechanical strength due to limited vitrification. In contrast, firing at 1200 °C promoted extensive verification and densification, resulting in improved strengths surpassing the severe-weathering requirements of ASTM C62. Compressive strengths of 74.62 MPa and 52.55 MPa were achieved for bricks containing 20% and 40% RHA, respectively, exceeding ASTM C62 severe weather grade requirements. Results demonstrate that RHA can be utilized at high replacement levels when appropriate firing conditions are applied, supporting sustainable fired brick production and agricultural waste valorization.