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 (similar to 0.04%) to accelerated (5-20%) levels. The higher CO2 diffusion within samples cured under 5-20% CO2 increased the compressive strength by similar to 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.

Automated summary

This study found that the microstructural and mechanical properties of reactive MgO cement concrete are enhanced as the CO2 concentration increases. 5-20% CO2 led to a 5-fold increase in compressive strength, but samples cured under 20% CO2 showed limitations on further CO2 diffusion. The use of 5% CO2 produced comparable strengths at 28 days as 20% CO2, while samples cured under 10% CO2 exhibited the best performance.