Properties of binary and ternary reactive MgO mortar blends subjected to CO₂ curing

Research and development of low CO₂ binders for building material applications is warranted in efforts to reduce the negative environmental impacts associated with the cement and concrete industry. The purpose of this study is to investigate the effect of carbonation curing on the mineralogy, morphology, microstructure and evolution of compressive strength of mortars comprised of general use (GU) cement, ground granulated blast furnace slag (GGBFS), and reactive MgO used as cement replacement. This study investigates binary (GU-MgO) and ternary (GU-GGBFS-MgO) blends exposed to atmosphere curing (0.0038%CO₂) and carbonation curing (99.9%CO ₂). Carbonation-cured mortars exhibited greater compressive strengths than atmosphere mortars at all ages (7 d, 28 d, and 56 d). Increasing percentages of reactive MgO decreased the compressive strength markedly less for carbonation-cured mortars than atmosphere-cured mortars particularly due to magnesium calcite formations. Magnesium calcite influenced the morphology of carbonates and promoted the carbonate agglomeration resulting in a dense and interconnected microstructure.