State-of-the-art-review on rice husk ash: A supplementary cementitious material in concrete

Rice husk ash (RHA) is a good supplementary cementitious material for concrete production, as it requires low energy and emits negligible greenhouse gas during processing and service life as well as it shows high pozzolanic reactivity. The pozzolanic reactivity of RHA depends on its amorphous silica content, fineness, mix proportion, available alkaline media, and temperature because all of these factors are related to the dissolution of silica from RHA. Thus, incineration time, temperature, processing, and grinding of RHA should be controlled to acquire the desired level of pozzolanic reactivity. Depending on the filler effect and pozzolanic reactivity of RHA, concrete's strength varies. The RHA-blended cement concrete possesses dense microstructure, high mechanical performance, and enhanced durability against harsh environmental exposure. However, the cement replacement level by RHA should be within the optimum level, which is a factor of fineness and the mixed proportion of concrete. This review covered the current practice and guidelines of RHA-blended concrete. Simultaneously, this review also revealed a gap in in-depth investigations about the long-term durability and serviceability of reinforced RHA-blended concrete. Further research could lead to the application of RHA as a cost- and environmentally competitive alternative in the production of high-performance concrete. The summary and discussions provided in this paper will provide both direction and knowledge on the applications of greener and more sustainable RHA-blended concrete for researchers.