Influence of Cellulose Ethers on the Carbonation Behavior of Cement Pastes

Cellulose ethers (CE) are generally used in cement-based materials as viscosity modifying admixtures. However, previous investigations scarcely focused on the effect of CE on the carbonation behavior of host materials. This work studied the effect of CE on the carbonation behavior of cement pastes. The carbonation resistance of samples was determined using the carbonation depth and pH values. The changes in hydration products and microstructure of host materials were monitored to reveal the underlying mechanisms using electrochemical impedance spectroscopy, X-ray diffraction analysis, thermogravimetric analysis, scanning electron microscopy, and mercury intrusion porosimetry. The results indicate that CE decrease the portlandite (CH) content and inhibit the growth of CH crystal with a smaller size and eroded edges, thus increasing its reactivity with CO2 during carbonation. CE increase the porosity and coarsen the pore structure because of the air-entrainment effect in cement pastes, promoting the CO2 diffusion in the system. As a result, CE decrease the carbonation resistance of cement pastes with increasing the CE content.