Carbonation of Concrete: Measurement and Repair

To extend the service life of concrete structures, measures against the damage from carbonation are often sought. However, it becomes progressively difficult to guard the existing concrete as the structures have aged and their porosities may be mixed and varied. This work aims to provide the state of the art concerning the carbonation process of concrete and the methods available for the determination of the carbonation depth, assessing the quality of the concrete, and repairing the damaged concrete. Information is gathered from an extensive literature study and from interviews with experts in the field. Interaction with research students and researchers working in the field of carbonation of concrete has also been of value. The phenolphthalein test and the indicator method were adapted to determine the carbonation front of the concrete. The extent of carbonation was evaluated using concrete core extraction method and a cover meter which can give an indication of the depth of concrete cover over reinforcement and a rough estimation of the diameter of steel present. Since the carbonation process is affected by a myriad of variables, this study focuses solely on the most systematic methods available for determining the carbonation depth and the influence factors on reinforcement corrosion such as water-cement ratio (W/C), composition of the concrete, the temperature, the relative humidity and the resistivity. Test results have shown that the carbonation is the principal cause of reinforcement corrosion in many concrete structures. Indeed, the measure of the depth of carbonation and thus detecting its presence has very important repercussions on the repair method.