Effects of rice husk ash on strength and durability performance of slag-based alkali-activated concrete

Despite their low impact on the environment and excellent mechanical strength, alkali-activated concretes (AAC) can potentially replace ordinary Portland cement based concrete (OPC). However, AAC can be eco-friendly and more sustainable by incorporating agricultural waste such as rice husk ash (RHA). Therefore, this study investigated the impact of RHA on the strength and durability performance of ground granulated blast furnace slag (GGBS) based AAC. For this purpose, seven mixes were made, in which RHA partially substituted GGBS with an increment of 5% up to 30%. The results of the experiments show that the workability and unit weight of AAC mixes decreased as the amount of RHA in the mix increased. The compressive strength of AAC mixes lies between 39.78 and 64.80 MPa, which is adequate for structural application. The AAC showed similar trends for all the mixes in terms of water absorption, permeable voids, apparent porosity and sorptivity. Compared to other mixes, the 5% GGBS substituted with RHA yields the highest resistance against carbonation. Compared to the sulfuric acid (H2SO4) cured sample, the specimen treated with hydrochloric acid (HCl) performed better in loss in mass, strength and ultrasonic pulse velocity. From scanning electron microscope test, the dense microstructure with pore refinement was observed in GGBS based AAC mix with 10% RHA content. According to the findings, RHA content up to 10% substitution can be used as a substitute for the binder to produce sustainable AAC with greater durability and could eventually replace conventional concrete in structural applications.