Simultaneous use of industrial converter slag as CO₂ sorptive materials and paving blocks

High-quality steel is widely utilized in numerous industries worldwide. However, converter slag (CS), a by-product of the steel manufacturing process, presents significant challenges in terms of sustainable management and disposal. In this study, the feasibility of using CS as a CO₂-sorptive material in a high-temperature incineration facility was systematically evaluated. Subsequently, the potential application of CO₂-adsorbed CS as a sustainable material for concrete paving blocks was examined. The CO₂ uptake capacity of CS was investigated over a temperature range from ambient conditions to 900 °C, corresponding to the typical operating temperatures of incinerators and air pollution control systems. CO₂ uptake by CS commenced at approximately 460 °C and increased continuously up to 860 °C; however, significant CO₂ desorption was observed at higher temperatures. Both the CS and CO₂-adsorbed CS (CCS) were then used as concrete aggregates in the production of paving blocks. The flexural strength of the CS- and CCS-containing paving blocks was comparable to, or higher than, that of commercial paving blocks. Specifically, replacing 50 wt% of the conventional concrete aggregate (i.e., crushed stone) with CCS resulted in improved flexural strength. Additionally, the CCS-containing paving block exhibited superior environmental stability compared with conventional paving blocks, as no hazardous heavy metals were released during leaching tests. Finally, the economic feasibility of the proposed approach was evaluated. Overall, the CO₂-sorptive paving block demonstrated enhanced mechanical properties and environmental stability with no adverse effects. Therefore, this study suggests that the combined use of CS as a CO₂-sorptive material and as a component of sustainable concrete blocks represents a viable strategy for managing steel industry waste while contributing to carbon neutrality.