Reaction of hydrated cement paste with supercritical carbon dioxide

For geologic sequestration of captured CO₂, CO₂ is stored in spent oil wells and concrete is used to seal wellbore penetrations to prevent leakage of CO₂. In such deep underground environment, CO₂ stays in supercritical condition, so carbonation resistance of portland cement concrete against supercritical CO₂ becomes critical for ensuring long-term durability of wellbore concrete. In this work, reaction between hydrated portland cement and supercritical CO₂ was investigated at different temperature and pressure levels. It is to provide necessary information on prediction of long-term performance of portland cement concrete in wellbore environment. According to the experimental results, it was found that the amount of aragonite increased with the increase in temperature and pressure, but vice versa for the case of vaterite. In terms of total CO₂ uptake into hydrated cement paste, there was no clear relation observed as increase in temperature and pressure. It is probably due to the fact that hydrated cement paste has reached its full level of carbonation after 24 h of reaction with supercritical CO₂.