Abstract Rice husk ash (RHA) has been widely investigated as a supplementary cementitious material in self-compacting concrete (SCC); however, reported effects remain highly variable, limiting its reliable adoption in practice. Addressing this challenge is critical for advancing sustainable SCC design and reducing cement-related environmental impacts. This review critically synthesizes existing research on RHA-incorporated SCC, focusing on performance trends, sources of variability, and implications for sustainable construction. The influence of RHA chemical and physical characteristics on fresh behavior, mechanical properties, durability, and microstructure is systematically analyzed. The literature indicates that RHA performance is strongly dependent on combustion conditions, particle fineness, replacement level, and mix design, leading to non-uniform and sometimes contradictory results. RHA typically exhibits a mean particle size of approximately 21.4 µm, with about 90 % of particles finer than 35 µm, and a specific surface area reaching up to 850 m 2 /kg. Incorporation of RHA often reduces slump flow due to increased surface area and water demand; however, acceptable or improved workability has been reported under optimized superplasticizer dosages and mixture proportions. Mechanical properties show a clear non-linear response: compressive and flexural strengths are frequently enhanced at replacement levels of 10–15 % due to pozzolanic activity and micro-filling effects, while higher dosages commonly lead to strength reduction from binder dilution. The elastic modulus generally follows compressive strength trends but exhibits mixture-dependent variability. Durability performance reflects competing mechanisms, with moderate RHA contents promoting pore refinement and interfacial transition zone densification, whereas excessive replacement may increase porosity and water absorption. Overall, this review provides a mechanistic framework that reconciles conflicting findings, identifies optimal RHA incorporation ranges, and supports performance-based mix design for sustainable SCC.
Mohamed et al. (Thu,) studied this question.