Influence of CO2 curing on mechanical properties and microstructure of hydrated magnesium silicate

Hydrated magnesium silicate (M-S-H) samples with good fluidity of 270 mm were prepared. The mechanical properties of the M-S-H samples cured in CO₂ conditions were examined. Moreover, the M-S-H samples under 70 % RH wet curing and standard curing conditions were prepared as comparison samples. As a result, the mechanical properties of the M-S-H samples under CO₂ curing conditions significantly improved. Compared to the M-S-H samples under 70 % RH wet curing and standard curing conditions, the 28-day compressive strength of the samples under CO₂ curing conditions was increased by 116.83 % and 74.25 %, respectively. Additionally, the microstructure of the M-S-H samples under the three curing conditions was investigated using XRD, SEM-EDS, TG/DSC, FTIR, and pore structure analysis. The results revealed that brucite reacted with CO₂ to form nesquehornite under CO₂ curing conditions. Furthermore, the volume stability of M-S-H was greatly affected by humidity, exhibiting expansion under standard curing and strong shrinkage under 70 % RH wet curing, while CO₂ curing can attenuate the shrinkage of the M-S-H samples.