Influence of CO₂ concentration on the performance of MgO cement mixes

This paper investigated the influence of different CO₂ concentrations on the microstructural and mechanical development of reactive MgO cement (RMC) concrete. Combination of various analyses revealed the enhancement of hydrated magnesium carbonate (HMC) phases with relatively superior micro-mechanical properties as the CO₂ concentration increased from ambient (~0.04%) to accelerated (5–20%) levels. The higher CO₂ diffusion within samples cured under 5–20% CO₂ increased the compressive strength by ~5 times. While samples cured under 20% CO₂ revealed high early strengths, the formation of a dense HMC layer on the sample exterior led to limitations on further CO₂ diffusion. Use of 5% CO₂ produced comparable strengths as 20% CO₂ at 28 days, highlighting the potential of using lower concentrations. Samples cured under 10% CO₂ revealed the best performance at 28 days, thereby defining this environment as the most favorable condition for the development of microstructural and mechanical properties of RMC concrete.