Using hazardous barium slag as a novel admixture for alkali activated slag cement

Abstract

Barium slag (BS) is a hazardous industrial solid waste formed during the production of barium carbonate. The accumulated stock of BS in China has exceeded 10 million tons, which urgently needs to be recycled in an efficient and sustainable way. BS contains a lot of soluble Ba2+ with a leaching concentration up to 2000 mg/L in water. Meanwhile, Ba2+ is an alkali-earth metal which can activate ground granulated blast furnace slag (GGBFS). This paper explores the possibility of incorporation BS as an admixture for alkali activated slag (AAS) cement. The mechanical property and microstructure evolution of AAS pastes with addition of BS are investigated in comparison with pure AAS paste. The results indicate that the addition of BS could significantly enhance mechanical strength of AAS paste, attributing to the increased hydration degree and the formation of dense pore structure. In addition, the leaching concentration of Na+ shows a significant decline by incorporation of BS in AAS paste, associated with the changed composition of hydration products. Therefore, BS is a promising admixture for AAS cement and holds great potential for promotion and application.