Sustainable utilization of ladle furnace slag: enhancing mechanical properties through accelerated carbonation

Abstract

Steel production generates a significant quantity of ladle furnace slag (LFS), awaste material with limited conventional applications, predominantly disposed of in landfills. This study investigates the potential of valorizing LFS through accelerated carbonation, a process that consumes CO₂ and converts the slag into a valuable non-cementitious binder for construction materials. The work specifically focused on the influence of key process parameters water-to-solids (W/S) ratio, carbonation time, and compacting pressure on the mechanical properties of carbonated LFS compacts. Cylindrical LFS samples were prepared by uniaxial pressing with varied W/S ratios (0.07–0.13) and compacting pressures (2–32MPa). These samples were subsequently carbonated in a sealed stainless steel reactor under pure CO₂ at 0.6 bar overpressure, for varying durations (2, 4, 6, 14, and 24 hours), without active temperature control. Compressive strength testing was performed immediately post-carbonation. Results demonstrated that the W/S ratio critically influences strength, with an optimal ratio of 0.11 yielding a maximum compressive strength of 51.34 MPa. Carbonation time significantly impacted strength development, showing rapid initial gain followed by a sustained increase, reaching 51.34MPa at 24 hours (for W/S 0.11, 16 MPa). Furthermore, compacting pressure was directly correlated with strength, with higher pressures leading to denser samples and enhanced mechanical properties; the maximum strength of 55.07 MPa was achieved at 32 MPa (for W/S 0.11, 24 h carbonation). These findings highlight the crucial role of process parameter optimization in developing high-strength carbonated LFS products. The achieved strengths confirm the viability of carbonation as an effective and sustainable method for LFS valorization, offering a promising alternative binder for the construction industry and contributing to CO₂ sequestration.