Evaluation methods of concrete carbonation suppressive performance of surface coating

Various studies have been conducted to estimate the ability of coating materials to suppress the carbonation process in concrete. The typical method for determining the effect is to use an accelerated carbonation test of concrete specimens with various coating materials. After the accelerated carbonation test, the neutralization depth is usually determined by using phenolphthalein. In our study, thermogravimetric analysis (TGA) was also performed besides using the phenolphthalein method in order to evaluate the carbonation suppressive performance more quantitatively. Next, in order to develop a method for the evaluation of the suppressive effect that is quicker than the accelerated carbonation test, we developed a box method that we could apply to evaluate the carbon dioxide (CO₂) permeability of a variety of coating materials. The main results obtained can be summarized as follows: 1) It is well known that a parabolic law can be obtained between carbonation periods and neutralization depth values determined by the phenolphthalein method. It has been confirmed that such a parabolic law can also be obtained between carbonation periods and the total amounts of CaCO₃ formed in the specimens. The coefficients of the neutralization rate obtained from both of the parabolic relations reasonably correspond to each other. 2) The box method can quickly evaluate the carbon dioxide permeability and is useful for predicting the effect that coating materials have on the suppression of the carbonation process in concrete.