Synthesis, characterization, and environmental impact analysis of one-part alkali-activated materials based on alkali-fused basic oxygen furnace slag

Abstract

One-part alkali-activated materials (AAM), a low-carbon alternative to cement, can reduce CO₂ emissions while improving the utilization of industrial by-products. In this study, basic oxygen furnace slag (BOFS) was activated by alkali fusion with different contents of sodium hydroxide (NaOH), and the optimum NaOH content was selected by the mineral phase composition and micromorphology of alkali-fused basic oxygen furnace slag (ABOFS). Then, ABOFS and ground granular blast furnace slag (GGBFS) were used to prepare one-part AAM pastes, and the effects of GGBFS content on the reaction products, microstructure, leaching characteristics and mechanical strength of one-part AAM pastes were studied. Finally, the life cycle assessment (LCA) of one-part AAM pastes was conducted. The results showed that alkali fusion activation promoted the formation of reactive mineral phases in BOFS and increased its specific surface area. The optimum NaOH content for alkali fusion activation is 10 wt%. The reaction products of one-part AAM pastes primarily consisted of C-(N-)A-S-H gel and hydrotalcite. As GGBFS content increased from 0 wt% to 80 wt%, the amount of gel products first increased and then decreased, peaking at 60 wt%. The addition of GGBFS reduced the porosity of pastes and increased the proportion of gel pores, resulting in a denser structure. Therefore, the compressive strength of one-part AAM pastes increased with the increase of GGBFS. LCA results indicate that the global warming potential (GWP) of one-part AAM is significantly lower than that of ordinary Portland cement. The findings of this study provide new insights into the application of BOFS in AAM.