Effects of Rice Husk Ash on Concrete Compressive Strength: A Systematic Review

Rice husk ash (RHA), a silica-rich agricultural byproduct, has increasingly been investigated as a sustainable supplementary cementitious material in concrete. However, reported findings regarding its effect on compressive strength vary substantially across studies due to differences in curing duration, particle fineness, water-cement ratio, and mix design. This study presents a systematic review and quantitative synthesis of published experimental studies evaluating the effect of partial cement replacement with RHA on concrete compressive strength. Following PRISMA-based screening, studies reporting compressive strength outcomes for control and RHA-modified concrete mixtures were included. Extracted variables included RHA replacement level, curing age, mix parameters, and compressive strength values. A random-effects framework was adopted to synthesize relative strength changes due to substantial betweenstudy heterogeneity. Results indicate that low replacement levels (approximately 5–10%) generally maintain compressive strength, with occasional modest improvements, whereas higher replacement percentages (¿15%) tend to significantly reduce strength. Substantial heterogeneity was observed across studies due to methodological variation. These findings suggest that a potentially effective range of low-level RHA incorporation appears to be favorable for supporting sustainable concrete production while preserving structural performance.