Temperature-regulated ammonium carbonate curing of steel slag: Enhanced carbonation, strength, and CO2 mineralization for sustainable building materials

Abstract

This study systematically examines the effects of temperature on the carbonation consolidation of steel slag in ammonium carbonate solution, aiming to develop sustainable building materials and improve CO 2 mineralisation efficiency. By exposing steel slag compacts to curing temperatures of 20°C, 40°C, and 60°C, the research shows that higher temperatures significantly enhance both the compressive strength and carbonation conversion of the material. Specifically, the 60°C curing group achieved a peak compressive strength of 118.38 MPa, which is 114% greater than at 20°C, emphasizing the vital role of temperature in speeding up reaction kinetics and fostering the formation of strong carbonation-hydration products. Comprehensive characterizations—including uniaxial compression, total carbon analysis, XRD, TG-DTG, FT-IR, and SEM—indicate that higher temperatures promote Ca 2+ dissolution, increase calcium carbonate crystallinity, and encourage the development of denser microstructures. The addition of ammonium carbonate not only aids mass transfer and Ca 2+ extraction but also introduces a new mineralisation pathway involving carbamate ions. These findings offer a theoretical and experimental basis for optimizing the carbonation process of steel slag, advancing its use as an eco-friendly construction material with significant CO 2 sequestration potential.