Transformation of rice husk modified basic oxygen furnace slag into geopolymer composites

Synergistic use of industrial and agricultural by-products can be solution of carbon emission from construction industry. The whole world is facing a crisis in finding ways to dispose of waste material. Hence, this study attempts to use rice husk and rice husk ash in geopolymers. Thus the study aims to develop a rice husk/basic oxygen furnace slag based geopolymer and study the factors affecting the performance of the binder. The developed geopolymer specimens were characterized using mechanical testing, physical and chemical techniques. The expansive nature of the organic matter in rice husk resulted in the geopolymer expanding and cracking. For this reason, rice husk ash was used to replace basic oxygen furnace slag. The rice husk was calcined at 600 °C to produce rice husk ash. The amount of rice husk ash as a replacement for basic oxygen furnace slag geopolymer varied from 0% to 50%. The effect of NaOH concentration, solid/liquid ratio, Na₂SiO₃/NaOH ratio, and the curing temperature was also studied to investigate the optimum parameter. The unconfined compressive strength is used to determine the performance of the binder. The results indicated an uptrend in unconfined compressive strength when increasing the rice husk ash content from 5% to 10%, and the optimum was 10%. Specimen with 8 M NaOH concentration had the highest unconfined compressive strength of 6.285 MPa. Moreover, it was also found that curing at 80 °C is an optimum condition for curing. Efflorescence formation and alkali leaching increased with the increase in rice husk ash content.