Synthesizing GGBS-LiOH based geopolymer with low embodied energy as a new alternative for construction

Abstract

Ground Granulated Blast furnace Slag (GGBS) is a promising alternative binder of Ordinary Portland Cement (OPC) due to its potential to reduce CO2 emissions and promote efficient waste recycling in the construction industry. However, the limited cementing capability of pure GGBS when hydrated with water necessitates the use of alkaline activators to enhance its hydration behavior. The present work establishes the use of lithium hydroxide (LiOH) as an effective alkaline activator for GGBS. As LiOH can be synthesized from the electrolytes of used lithium-ion batteries (LIBs), the study establishes the use of two waste products to potentially reduce the carbon footprint of the construction industry. Experimental results demonstrate that a 10M LiOH solution significantly enhances the cumulative heat evolution of GGBS (GGBS with DI water = 3.53 J/g, GGBS with LiOH = 127.59 J/g). LiOH activated GGBS exhibits the presence of hydration products such as LiASH and CSH from day 1 of hydration, while GGBS mixed with DI water shows CSH peaks only after 28 days. TGA 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 ~ 51% compared to NaOH based geopolymer and ~ 55.50% compared to cement concrete.