Performance, thermodynamic modelling, and global warming potential of low sodium-activated artificial granulated slag substituted with quartz and limestone fillers

Abstract

Commercialization of alkali-activated slag faces, among others, two major hurdles: limited availability of blast-furnace slag and the high cost of alkaline activators. Furthermore, the corrosive nature of the alkaline solution, the energy-intensive production, and the resulting CO₂ emissions significantly impede widespread adoption. This research presents a novel approach to overcome these challenges and pave the way for commercially viable alkali-activated binders. We propose utilizing highly reactive artificial granulated slag (AS) synthesized from the treatment of slag generated during ferrochrome alloy production. This AS serves as the primary reactive precursor within the alkali-activated system. Activation of AS with a low Na₂O concentration (3 wt%) yields a hardened material boasting a remarkable 90 d compressive strength of approx. 105 MPa. Capitalizing on the exceptional reactivity of AS, we explored its partial replacement with readily available and cost-effective quartz and limestone powders. Despite the lower reactivity of these fillers compared to AS, the resulting hardened materials containing 50 vol% filler still achieve an impressive 90 d compressive strength of 75 MPa, even with a low Na₂O content of 2 wt%. Phase composition determined via thermodynamic modelling closely aligns with microanalyses and the observed compressive strength. Life cycle assessment (LCA) conclusively demonstrates that the synergistic combination of highly reactive AS, fillers, and low Na₂O concentration offers a promising route for producing alkali-activated binders with significantly lower energy demand and CO₂–eqv emissions (up to 67% reduction).