Development of high-performance concrete using guinea corn and rice husk ashes as replacement for silica fume

High-Performance Concrete (HPC) offers higher strength and durability compared to nominal concrete. Silica fume, a key cementitious material in HPC, significantly enhances mechanical performance because of its fine particle size and high reactivity. However, Nigeria’s dependence on imported silica fume poses sustainability and cost challenges. Between August 2023 and July 2024, imports increased by 400 %, with a single exporter serving one buyer. By July 2024, no imports were recorded, revealing the volatility and risks of relying on foreign supply. This study investigates the potential of Guinea Corn Husk Ash (GCHA) and Rice Husk Ash (RHA), agricultural wastes abundantly available in Nigeria, as sustainable alternatives to silica fume in HPC production. The characteristics of GCHA and RHA were evaluated, alongside their effect on concrete workability and strength. Findings showed that RHA improves compressive, tensile, and flexural strengths due to its high amorphous silica content and reactive surface. GCHA, with lower reactivity and higher water demand, causes a gradual decline in strength properties. However, an optimized blend containing 8 % GCHA and 22 % RHA achieved a compressive strength of 50 N/mm², along with improved sustainability and adequate workability. These findings support the use of local pozzolans in cost-effective, high-performance concrete.