Influences of w/c and CO2 curing duration on the high temperature properties of cement pastes

Abstract

CO2-cured cement paste containing rich carbonate products is expected to have a better performance at elevated temperatures. In this study, cement pastes with varying water-to-cement ratio (w/c) were cured with CO2 for various duration, aiming to induce different carbonation degrees and hence elucidate the underlying mechanism upon exposure to high temperatures (200°C, 400°C, 600°C, and 800°C). The results showed that CO2-cured cement paste exhibited better performance in terms of water absorption and compressive strength after exposure to temperatures up to 600°C. The composition and microstructure results demonstrated that high w/c which induced larger pore structure not only increased the carbonation degree of cement paste but also increased the proportion of well-crystallized calcites. However, when the temperature was raised to 800°C, CO2-cured cement paste had a relatively lower residual strength than water-cured cement paste due to the decomposition of CaCO3, regardless of w/c and CO2 curing duration.