Study on preparation and CO2 sequestration mechanism of high-strength carbonated Ladle refining slag binder

Abstract

Abstract Ladle refining slag (LFS), classified as solid waste, presents an imminent need for comprehensive utilization. Notably, LFS contains a substantial amount of γ-Ca2SiO4 (γ-C2S) with remarkable carbonation potential, making it an ideal candidate for the production of carbonated cement through Carbon Capture and Storage (CCS) technology. This study delves into the carbonation reaction of the cast and molded lump LFS within a CO2 pressure vessel. It systematically examines the influence of water-solid ratio and water content on the initial properties of specimens. Furthermore, the investigation encompasses the impact of temperature, reaction time, and CO2 pressure on carbonation processes and resultant products, contributing to the formulation of a carbonation reaction and mass-transfer mechanism. The research reveals pivotal findings: lower water-solid ratios lead to denser specimens with higher strength, and an optimal 7% water content facilitates effective cementation and reactant dissolution. The controlled growth of densely layered calcite at 20°C yields impressive strengths of up to 120.5MPa, while elevated temperatures, such as 60°C, encourage the growth of smaller calcium carbonate crystals, resulting in a favorable carbon sequestration rate of 19.72%. Extending the carbonation time enhances the conversion rate of γ-C2S to calcium carbonate. Intriguingly, CO2 pressure exerts minimal influence on the specimens. The research elucidates the five-step carbonation process and its underlying diffusion mechanism. In essence, this study harnesses CCS technology to offer a high-value solution for addressing LFS disposal challenges.