Performance Evaluation of Rice Husk Ash as a Sustainable Supplementary Cementitious Material in Pavement Concrete

Abstract

This study examines the feasibility of utilizing rice husk ash (RHA) as a supplementary cementitious material (SCM) in concrete for pavement applications. Unlike many prior investigations that rely on thermally processed RHA, this work employs locally sourced RHA without additional treatment, thereby reflecting a more practical and resource-efficient approach. A series of laboratory evaluations, including X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and compressive strength testing, were conducted to characterize the chemical composition, microstructure, and mechanical performance of RHA-modified concrete. The RHA was found to be rich in amorphous silica, indicative of substantial pozzolanic activity. Concrete incorporating 5% RHA as a partial cement replacement exhibited the highest compressive strength, outperforming the control mix. In contrast, higher replacement levels (10–20%) led to decreased strength due to the dilution of cementitious phases and the presence of unreacted RHA. Microstructural observations confirmed that RHA contributes to matrix refinement by reacting with calcium hydroxide to form additional calcium silicate hydrate (C–S–H) gel. Overall, the findings demonstrate that low-level RHA incorporation can enhance mechanical performance while simultaneously promoting sustainability through agricultural waste utilization and reduced CO₂ emissions associated with cement production.