Exploring Rice Husk Ash in Uncontrolled Condition as Supplementary Cementitious Materials for Enhanced Performance in Construction Materials

This study investigates the potential of Rice Husk Ash (RHA), an abundant agricultural byproduct in Bangladesh, as a sustainable supplementary cementitious material (SCM) in concrete. Ordinary Portland Cement (OPC) was partially replaced with locally produced, unprocessed RHA at proportions of 5%, 10%, 15%, and 20% by weight, with a control mix (0% RHA) for comparison. Mechanical performance was evaluated through compressive and tensile strength tests at 7, 14, and 28 days, complemented by durability assessments in saltwater conditions. Microstructural and chemical analyses were conducted using X-ray Diffraction (XRD), Energy Dispersive X-ray Spectroscopy (EDX), and Scanning Electron Microscopy (SEM). Results revealed that 10% RHA replacement achieved the optimal balance between strength and sustainability, with compressive strength reaching 22.06 MPa and tensile strength showing improved pozzolanic activity over time. Higher replacement levels (15–20%) significantly reduced strength due to dilution effects. Microstructural studies confirmed the high amorphous silica content and favorable morphology of RHA, supporting its pozzolanic reactivity. Incorporating RHA reduces cement demand, lowers emissions, and offers an environmentally friendly solution for managing agricultural waste. The findings establish that a 10% substitution of OPC with unprocessed RHA provides an effective, eco-friendly, and cost-efficient pathway toward green construction in Bangladesh and other rice-producing regions.