Comparison of concrete carbonation process under natural condition and high CO2 concentration environments

To compare the results obtained under both natural and accelerated environments, the pH values of carbonated concrete were measured, the variation of pH values was determined, and the variations of Ca(OH)2 and CaCO3 contents in the carbonated concrete under natural condition and high CO2 concentration accelerated climate environments were determined by microcosmic test methods such as DTA and X-ray diffraction. The experimental results showed that the overall variation trend of pH values and phase component of carbonation layer of concrete under accelerated climate environments with high CO2 concentrations were the same as those under natural conditions. Therefore, the carbonation processes of concrete were considered consistent under both conditions. However there was a difference in the length of semi-carbonation zones. The one measured under high CO2 concentration accelerated climate environments was shorter than that under natural condition. Experimental investigation showed that it was caused by the differences in climate condition (temperature and relative humidity) as well as the properties of the concrete. The concentration of CO2 and the duration of the carbonation process have no effect on the length of semi-carbonation zone. Thus, it is acceptable to simulate the natural condition by applying the high CO2 concentration artificial accelerated carbonation technique for the purpose of the study of carbonation process of concrete.