Physical and Mechanical Performance of Mortar with Rice Husk Ash and Sugarcane Bagasse Ash as Partial Cement Replacement

Natural supplemental cementitious materials (SCMs) with pozzolanic qualities, such as rice husk ash (RHA) and sugarcane bagasse ash (SCBA), are a promising alternative to the currently used SCMs that are becoming increasingly unavailable. This work presents a comprehensive comparative examination of their impact on mortar properties when OPC was partially replaced by RHA and SCBA. The percentage substitution of OPC with ashes was 0, 5, 10, and 15%. The air content, consistency, compressive strength, flexural strength, and shrinkage of the mortar were investigated primarily. Microstructural characteristics were analysed using porosimetry, MIP, and SEM photography. According to the study, up to 10% replacement of OPC with RHA or 15% with SCBA has the potential to be used as a partial cement substitute while maintaining good mechanical qualities. Mortars with up to 15% SCBA exhibited no significant change in compressive strength after 28 days or a decrease with <11%, while for 10% RHA, there was no difference in compressive strength or increase. Use of 5% RHA decreased shrinkage by 35%, while addition of 5% SCBA by 30%. Obtained results demonstrated the usefulness of SCMs in masonry mortars.