Investigation on the basic performance of the sustainable alkali-activated slag blended with sulphidic copper tailings

Utilizing sulphidic copper tailings (SCT) with rich sulfur content in cementitious materials presents a challenge due to its incompatibility with cement. For the bulk use of SCT, this paper demonstrated that alkali-activated slag (AAS) can be a good binder for SCT, and the effects of SCT addition on the setting time, hydration products, microstructure, compressive strength, pore structure, and autogenous shrinkage of AAS were investigated. Results showed that introducing SCT into AAS facilitated the generation of sulfate-containing products during GGBS hydration, e.g., gypsum and ettringite, since the pyrite in SCT is prone to oxidation, leading to the formation of sulfates. SCT can work as an auxiliary activator for GGBS along with NaOH to accelerate the hydration of ground granulated blast furnace slag (GGBS). Consequently, the gel pores of AAS mortar increased, the microstructure of AAS mortars was densified and the compressive strength was improved by 5.5~19.8% at 28d. In addition, the addition of SCT delayed the setting of the AAS paste, and the autogenous shrinkage of the mortars was mitigated by 27.2%-35.8%.