Exploring carbonation-induced volume changes and their relationship to microstructure development in reactive magnesia cement

Reactive magnesia cement (RMC) hardens through hydration and carbonation, where it sequesters CO2 from the air.The hydration and carbonation of RMC is an intrinsically volumeexpansion process.A sample calculation for the changes in molar mass and molar volume during hydration and carbonation is provided below.The hydration product, brucite undergoes carbonation and forms hydrated magnesium carbonates (HMCs), which is the primary contributor to the strength of carbonated cement.This work studies and quantifies the effect of carbonation on the volume change of RMC.The development of the microstructure over time, as it relates to volume change, was examined.Reactive magnesia cement (RMC) paste, without any additives, typically undergoes setting in 2 hours or less.The length at final setting was used as the reference point for measuring length change.After demoulding at final setting, the RMC paste was cured in a high humidity chamber for 24 hours before undergoing accelerated carbonation (10% CO2, 23C, 85%RH).The length of the RMC specimens was measured at days 1, 3, 5, 7, 14, and 28 to quantify the volume change due to carbonation.The effect of factors such as Water-to-cement ratio, and Hydration agent were explored.