12 years of natural carbonation on concretes made with supplementary cementing materials

Carbonation-induced corrosion is one of the major causes of degradation of reinforced concrete (RC) structures. To design durable RC structures the knowledge of the resistance to carbonation penetration is essential. Usually, in the literature, the carbonation resistance is evaluated through accelerated tests, which allow a first screening of the performances of different types of concrete, but cannot be directly used to evaluate their long-term behaviour. Hence, there is the need of tests under natural exposure conditions. Unfortunately, their duration is often quite limited compared to the usual values of service life of RC structures. This paper reports the results obtained on different types of concrete made with Portland cement and several supplementary cementing materials and different water/binder ratios, exposed for more than twelve years outdoor in Milan in sheltered conditions. Results showed that concrete with Portland cement has a higher carbonation resistance than concrete with limestone and pozzolanic cements.