Predicting carbonation depth for concrete with organic film coatings combined with ageing effects

Abstract A new time-dependent model for concrete carbonation depth prediction combining with the ageing effects of a coating was established to predict the carbonation depth of concrete with organic film coatings under practical service environmental conditions. This model could be solved by introducing a function about the equivalent concrete thickness of a coating with ageing time. Three coated concrete specimens with epoxy, polyurethane, and chlorinated rubber coatings were fabricated and subjected to natural outdoor experiments of exposure degradation for one year. The coated specimens were collected and subjected to accelerated carbonation experiments with different corresponding ageing periods. Based on these experiments, development models of the coatings’ equivalent concrete thickness with exposure time were obtained through regression analysis, and the carbonation depths of concrete with organic film coatings combined with the ageing of the coatings and repainting effects were obtained through numerical calculation. Results indicated that organic film coatings could improve concrete carbonation resistance effectively, and a coating with denser equivalent concrete thickness could better improve the carbonation resistance of concrete compared with a thinner application. However, this protection would gradually decrease and reach zero because of coating degradation. Coatings would not affect the development of concrete carbonation after reaching the desired service life. The carbonation resistance of concrete could be improved again through effective coating repainting, which could prolong its service life against carbonation.