Concrete Carbonation as a Limited Process and Its Relevance to Concrete Cover Thickness

A theoretical model for predicting the carbonation depth of concrete is presented. The proposed, experimentally determined model describes the carbonation depth as a function of the time of exposure, the water-binder ratio, and early-age curing conditions. The result is a new mathematical formulation of carbonation depth as a hyperbolic function of time, which assumes that the depth of the carbonation is ultimately limited as the concrete pores fill with carbonation products. Tests were carried out for 6 years in a natural atmospheric concentration of CO2 in an urban-industrial environment. The results showing the carbonation depth for concrete using different types of cement are used to derive equations to predict carbonation depth. It is expected that the resulting equations can be applied to the prediction of the concrete cover thickness for reinforcement in concrete structures.