Challenges in corrosion surveys on reinforced concrete structures – practical experiences from more than 20 years

Corrosion related measurements on reinforced concrete structures are often easy to apply, and many guidelines indicate that a straight and formal handling of the received data is possible. But practical experience advises to be careful, since similar data readings can be caused by very different, even contradicting situations and hence require an individual, distinguished assessment. For example, negative potential values may be caused either by true, chloride induced corrosion or just by extremely wet concrete – without any possibility of active rebar corrosion. For avoiding wrong interpretations and improper repair strategies, the recommended approach is to obtain various, different parameters, including a sound visual and acoustical inspection, and to compare them thoroughly on a common, plausible pattern. The paper gives some examples where usual survey approaches basing on potential mapping and chloride sampling only would have resulted in either not recognizing the extent of corrosion problems properly or in concluding on severe problems that in fact do not exist.