Enhancing the Hardening Properties and Microstructure of Magnesium Slag Blocks by Carbonation-Hydration Sequential Curing

This study focuses on addressing the challenges of low activity and poor volumetric stability in magnesium slag (MS) blocks. The novel approach of rapid carbonation-hydration sequential curing is employed to enhance the hardening properties and microstructure of MS blocks. The effect of different pre-carbonation degrees on volumetric stability and compressive strength is investigated. Characterization techniques such as XRD, TGA, FT-IR, NMR, and SEM-EDS are utilized to analyze the phase assemblage and microstructure. Results demonstrate that a 2-h pre-carbonation effectively eliminates volumetric instability. The MS blocks exhibit a compressive strength of 90 MPa after 24 h of carbonation, with CO2 uptakes reaching 17.28%. Subsequent hydration curing leads to a compressive strength of 120 MPa. The carbonation process generates significant amounts of calcite, aragonite, and highly polymerized silica, while hydration produces amorphous fibrous C-S-H. The interplay between the crystalline phase calcium carbonate and C-S-H results in a dense hardened structure, contributing to further strength enhancement. These findings highlight the potential for high-strength construction prefabrication using 100% solid waste MS and CO2 sequestration.