Enhancing the hardening properties and microstructure of magnesium slag blocks by carbonation-hydration sequential curing

Abstract

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.