Corrosion rate of carbon steel in carbonated concrete made with different supplementary cementitious materials

Carbonation-induced corrosion limits the durability of reinforced concrete structures exposed in urban environments. In these exposure conditions, the propagation phase of corrosion can be an important part of the service life and, hence the knowledge of the corrosion rate is essential for the design. However, data regarding the corrosion rate in carbonated concrete are scarce and mainly refer to Portland cement concrete. This paper reports the corrosion rate and corrosion potential of steel bars embedded in concretes with different binders and water/binder ratios, exposed both outdoor in unsheltered conditions and in laboratory conditions characterised by different temperatures and relative humidities. Concrete resistivity at different depths is also reported and correlations among these parameters are discussed. Corrosion potential, corrosion rate and concrete resistivity were strongly influenced by the relative humidity, while temperature played an important role only at high relative humidity. Steel in Portland cement concrete showed the lowest corrosion rate.