Development of a sustainable geopolymer using blast furnace slag and lithium hydroxide

Abstract

Ground Granulated Blast furnace Slag (GGBS) is a promising alternative to ordinary Portland cement due to its potential to reduce CO2 emissions. However, the limited binding capability of pure GGBS necessitates the use of alkaline activators to enhance its hydration behaviour. The present work establishes the use of lithium hydroxide (LiOH), which can be synthesized by recycling lithium-ion batteries, as an effective alkaline activator for GGBS. Experimental results demonstrate that a 10 M LiOH solution enhances the hydration of GGBS 36 folds. LiOH activated GGBS exhibits the presence of hydration products such as lithium-alumino-silicate-hydrate and calcium-silicate-hydrate from day 1 of hydration, while GGBS mixed with DI water shows onset of hydration only after 28 days. Thermogravimetry results from long-term hydration studies indicate that LiOH activated GGBS forms a 73% higher quantity of hydration products as compared to cement paste samples. Additionally, LiOH activated GGBS demonstrates 42% and 46% higher compressive strength than GGBS activated with NaOH and Na2SiO3 at 7 and 28 days, respectively. Embodied energy analysis reveals that geopolymer prepared with GGBS and recycled LiOH leads to equivalent CO2 emissions reduction of 83% compared to NaOH based geopolymer and 85% compared to cement concrete.