Hydration and carbonation reaction dynamics in CO2-rich environment for tricalcium silicate (C3S) and dicalcium silicate (C2S)

In the context of geological sequestration and utilisation of CO2, research on cement in high CO2 environments is becoming increasingly common. Yet, the fundamental mechanisms of cement's hydration and carbonation reactions under elevated temperature and pressure CO2 settings remain insufficiently investigated. This research concurrently exposed two primary cementitious phases (C3S and C2S) to water and high levels of CO2 to explore how these phases, under the combined influence of hydration and carbonation, impact overall cement hydration and carbonation. The results indicate that due to the fast hydration rate of C3S, most carbonates form through the interaction of C3S hydration by-products with CO2. In contrast, C2S primarily reacts directly with CO2, having a carbonation reaction rate of 41.67, notably higher than C3S (21.39). Environments abundant in water and CO2 are conducive to C3S carbonation, whereas environments with high CO2 levels but limited water favour C2S carbonation.