Sustainable Concrete Made with Rice Husk Ash: Comparison with Fly Ash and Blast-Furnace Slag

Cement production is responsible for roughly 8% of worldwide CO2 emissions. However, substituting 15% of cement with rice husk ash (RHA) has the potential to cut these emissions by around 10%. At the same time, the construction industry continues to struggle with unstable supply chains for supplementary cementitious materials such as silica fume, slag, and fly ash. To address this urgent issue, this study examines the performance of a concrete mix that incorporates RHA as a 10% replacement for ordinary Portland cement (OPC) and compared the results with 10% fly ash (FA), and 10% ground granulated blast-furnace slag (GGBS), as well as control mix (100% OPC). The stress-strain behaviour and strength of mixes were assessed at 14, 28, and 90 days. Data-driven models were created, and the results were compared with laboratory results. Although the slope of the stress-strain curves was slightly lower at an early age, all mixes containing RHA, FA, and GGBS exhibited notably higher slopes at 28 and 90 days. A moderate decrease in compressive strength was observed at 14 days (13% for RHA and GGBS and 15% for FA); however, at 28 and 90 days, the strength of mixes with RHA, FA, and GGBS was similar to or greater than that of the control mix. The developed mathematical models closely matched the experimental stress-strain profiles, including the more nonlinear regions. The accuracy of models was outstanding, with R2 values ranging from 0.9703 to 0.9990 for all mixes and curing periods. These results demonstrate that replacing 10% of OPC with RHA can be effectively used in concrete production, as it yields similar properties to those of mixes containing 10% FA and 10% GGBS, thereby 10% RHA can reduce around 7% CO2 emissions.