Structural and compositional changes in ladle furnace slag during CO2 capture

Abstract To facilitate the optimization of carbon capture and utilization through ladle furnace slag (LFS), it is essential to develop a deeper understanding of the interrelated evolution of reaction, microstructure, and performance. To this end, a novel carbonation-isothermal-calorimetry setup was devised and integrated with multiscale characterization (including TG–DTA, CS analysis, XRD, SEM–EDS, MIP, and DFT) to observe the reaction kinetics of LFS in real time. This comprehensive strategy reveals a significant temporal mismatch between chemical conversion and the development of mechanical properties. Notably, the majority of the chemical reaction and CO 2 sequestration is completed within the first 30 min, as confirmed by calorimetry and thermal analysis. In stark contrast, the primary increase in compressive strength is significantly delayed, occurring rapidly only between 30 and 45 min. This decoupling clarifies that the ultimate performance of the material is not kinetically limited by the initial rapid CO 2 reaction. Instead, strength development is governed by subsequent diffusion-limited processes, including the recrystallization of initial metastable phases into stable calcite and the progressive densification of the silica-rich binding matrix through pore refinement.