Recycling copper slag as precursor in alkali-activated materials: Reaction mechanisms, microstructural features, and environment impact

This study explores the feasibility of incorporating copper slag (CS) as a partial mineral precursor in alkali-activated materials (AAM). By utilizing ground granulated blast furnace slag (GGBS), fly ash (FA), and CS as precursors, a novel three component eco-friendly binder has been successfully developed. The study comprehensively assesses the influence of CS on the reaction rate, microstructural feature, and environment impact of AAM system. Compared to FA, CS exhibits higher solubility of silica and calcium, which can participate more effectively in geopolymerization and play a notable role in the formation of C-(A)-S-H gels. A K-D model was constructed using heat release data, revealing that the addition of CS significantly enhances the reaction extent. This led to a 33.3 % increase in the compressive strength of the matrix at 3 d and a notable enhancement in the degree of polymerization of the gel network. Microstructural analysis demonstrates that increasing CS substitution improves gel enrichment and pore filling effects. This optimization of the pore structure resulted in a decrease in both porosity and the quantity of large sized pores. From an economic and environmental perspective, reusing CS brings about a substantial decline in both energy consumption and carbon emissions, achieving a 56.92 % decrease in energy consumption and a 75.81 % reduction in carbon emissions. Such work may shed valuable insights to the recycling of various types of solid waste and low-carbonation of building field.