CO2 sequestration by high initial strength Portland cement pastes

Abstract

During the formation of pastes, mortar and concretes have been used to capture CO2. This work presents a methodology to estimate the carbon dioxide (CO2) sequestered by high strength and sulfate-resistant Portland cement pastes during their early stages of hydration, by Thermogravimetry and Derivative Thermogravimetry. Water to cement ratio equal to 0.50 and 0.70 were evaluated and the captured CO2 amount was determined through TG/DTG curve data on initial cement mass basis, obtained during accelerated carbonation from the fluid state and accelerated carbonation after a first hydration process. The experiments were performed in a controlled chamber, maintaining the CO2 content at 20 vol % and the temperature at 25 °C, at different relative humidity (RH) (60 and 80 %) ambient. The procedure allows one to estimate the amount of CO2 sequestered by the initial cement mass of a given volume of paste, as well as to evaluate the RH and W/C ratio influence on the amount of hydrated formed products, mainly on the Ca(OH)2, important for CO2 fixation.