Carbonation of blended cement concretes after 12 years of natural exposure

In urban environments, the durability of reinforced concrete structures is limited by carbonation-induced corrosion. To prevent steel corrosion, the selection of a proper concrete in terms of type of binder, water/binder ratio and curing time, is of fundamental importance. At this aim the knowledge of the resistance to carbonation in the exposure environment is required. Usually carbonation is evaluated from accelerated tests, however natural exposure tests are needed to validate short-term tests and make reliable predictions of the behaviour in a real environment. This paper reports the carbonation of concretes with different binders, water/binder ratios and curing, exposed for more than twelve years outdoor in Milan in sheltered conditions. Concretes with Portland cement exhibited a higher carbonation in comparison with concretes with limestone and pozzolanic cements. Curing seemed to be less effective than the type of binder and the water/binder ratio.