The influence of carbonation on the passive layer of concrete

Abstract

Concrete carbonation is a pathology that arises from a chemical reaction between carbon dioxide (CO2), humidity and calcium hydroxide (Ca(OH)2), usually common in large cities. The process occurs more frequently in tunnels and viaducts, for example, where the presence of this element is greater. It stems from cracks that allow water to enter in the interior of reinforced concrete. Specifically, the carbonation of concrete can be defined as a physical-chemical process between carbon dioxide (CO2) present in the atmosphere and the compounds of the cement paste. Thus, the main result is the initiation of calcium carbonate (CaCO3) in the cover region, thus constituting a layer that starts to have a much lower alkalinity than the region not affected by this phenomenon. The carbonation advances from the outside to the inside in the concrete, through a carbonated front. When it reaches the depth of the reinforcement, it ends up causing the deterioration of the passive layer of the concrete, thus causing the beginning of corrosion of the reinforcement.