Concrete carbonation is the result of a chemical reaction between air carbon dioxide (CO2) and cement calcium hydroxide. Carbonation results in a lowering of the pH of concrete. This in turn reduces the natural capacity of concrete to protect reinforcement bars against corrosion in the presence of water (corrosion results in swelling of the bars, and eventually in burst of the concrete cover). Concrete elements sheltered from seepage caused by weather or condensation will not be subject to carbonation.
Reinforced concrete has long been regarded as age-insensitive. However, concrete carbonation is not a new phenomenon and remains an issue, because many structures are affected by the combined effects of air pollution and the use of de-icing salts (chlorides).
Today, preventive measures can be taken, such as improving concrete quality, monitoring of concrete pouring, and increasing the bar cover.
Our publications on this topic (in French):
"Façades et carbonatation - Faux problèmes, vraies solutions", Erik Langlo – Corinne Van Cauwenberghe.
Articles in revue IAS, Ingénieurs et Architectes Suisse: