chapter  4
38 Pages

Transport of carbon dioxide and carbonation

It is a well-known fact that steel corrosion reduces the serviceability and safety performance of reinforced concrete in general (Chapter 9 and Chapter 10). Usually, concrete maintains high alkaline conditions, which leads to a passive layer forming on the steel surface. However, several types of environmental actions such as carbonic, sulphuric and nitric acid can cause the reduced alkalinity of pore water in concrete. Under low-pH conditions, the passive layer around the steel surface breaks down, and rust readily appears on the surface. In order to evaluate performance factors of a concrete structure in a corrosive environment, it is therefore essential to quantify the neutralization of concrete, that is to say, the pH reduction due to such environmental acids. In this chapter, the authors mainly focus on the carbonation phenomenon, and aim to predict pH fl uctuations and material degradations under carbonic acid attack. This is also the basis of corrosion prediction of steel in concrete (Chapter 6).