Rice husk ash and nanomaterial-blended cement composites: a review

Enhancing the sustainability and performance of cement composites is crucial to the protection of the environment and advancing building technology. Numerous studies have been carried out to evaluate binary and ternary mixes incorporating micro- and nanosized supplementary cementitious materials (SCMs) to achieve these goals. Rice husk ash (RHA) stands out as an SCM due to its abundance as an agricultural residue having pozzolanic properties. However, the relatively low reactivity and the reduced workability due to the mesoporous structure hinder the adoption of RHA in cement composites. While nanomaterials offer the advantage of improved microstructure and higher reactivity, their high cost and demanding processing techniques limit their widespread adoption. Combined blends of nano- and micro-sized SCMs have shown promising results, as synergistic effects can mitigate their individual drawbacks, but the inter relationship is unclear. This paper reviews the existing studies on RHA and nanomaterial-blended cement composites to provide an understanding of their interactions. The available literature is categorized by the type of nanomaterial employed, and the mechanical, microstructural, and durability properties are summarized. The correlation between mechanical properties is derived, and summarized results are discussed to identify the underlying mechanism. Overall, this paper aims to provide a comprehensive overview of current knowledge on RHA-nanomaterial-blended cement composites. This summary will be beneficial in identifying research gaps and suggesting future directions for advancements in sustainable blended cement composites.