Innovative Korrosionsprüfung für Beton- und Spannstähle

Test methods for corrosion testing of reinforcing and prestressing steels

Corrosion is a primary damage mechanism in reinforced concrete construction, significantly reducing the service life of infrastructure. A categorisation of corrosion is imperative for the comprehension of the subject. The corrosion of concrete can be attributed to the carbonation process, whilst chloride-induced corrosion is prevalent in structures exposed to seawater or by de-icing salt. Additionaly to the former corrosion processe, prestressing steel structures could be also highly susceptible to hydrogen-induced stress corrosion cracking (SCC). In order to utilise alternative reinforcing steels, such as stainless reinforcing steel, it is necessary to ascertain the level of critical chloride threshold that can induce corrosion. Nevertheless, there is an absence of standardised test methods for determining this for the respective reinforcing steels to date. Acc. to current standardization, the sensitivity of prestressing steels to chromium content necessitates long-term ageing tests, which impede in-house production control due to the extended testing times. However, a newly developed test method using cathodic polarization, which has now been included in the latest draft of DIN EN ISO 15630–3, makes it possible to assess the susceptibility of prestressing steels to corrosion cracking within 24 hours. The results of this study will contribute to the improvement of service life estimation and the further development of standards for corrosion-resistant reinforcing steels and the robustness assessment of prestressing steels.