Electrochemical and gravimetric corrosion rate of steel bars in carbonated concretes

In corrosion affected concrete structures, the determination of the rate at which the corrosion attack proceeds is necessary to determine the magnitude of damage. Often, both in laboratory and in field, electrochemical techniques, such as the linear polarization resistance (LPR), are used to determine the corrosion rate. In this work, periodic LPR measurements were performed on steel bars embedded at different depth in carbonated concrete made with different supplementary cementitious materials and exposed to unsheltered exposure conditions. After about 15 years of exposure, the bars were extracted and the mass loss was evaluated. The comparison between electrochemically and gravimetrically measured reinforcement corrosion rates presented a quite high scatter, irrespective cover thickness and concrete quality. LPR seems to underestimate the corrosion rate in comparison to mass loss.