Enhancing the carbonation efficiency of reactive magnesia cement (RMC) through geometry-driven design strategy

Limited carbonation depth and consequent non-uniformity of reactive magnesia cement (RMC) raise concerns regarding its sustainability and structural integrity. This work developed a geometry-based design strategy to improve the overall carbonation efficiency and reduce the non-uniformity of RMC mortar. A central hole with different diameters was intentionally created in RMC cylinders, and its effects on the physical and chemical properties across varying depths were evaluated through a suite of material characterization techniques. The non-uniform distribution of carbonation degree, chemical composition, and microstructure along the depth was evident in control group. Such non-uniformity was effectively mitigated and virtually eliminated in RMC matrix with varying central holes. This improvement was attributed to the presence of central hole enabled the CO₂ to penetrate RMC matrix simultaneously from both the outer surface and inner surface, significantly enhancing the overall carbonation degree by up to 41.6% and compression strength by up to 85.1%. Additionally, the contribution of carbonation to the strength gain varied across different groups, which is associated with type and crystallinity of the formed hydrated magnesium carbonates (HMCs). The advantages of employing a geometry-based design strategy in RMC structures are multifaceted, representing a promising avenue towards the production of load-bearing RMC components.