Driven by the desire for load bearing yet slender constructions, prestressed concrete structures have become a widely adopted construction principle. Due to the increasing traffic loads on roads over the years, the stress profile of many prestressed concrete structures, such as bridges, has changed. The high strength steel used in these constructions is referred to prestressing steel. Depending on the application, prestressing steels are used in various forms and strengths. They can be categorized into three basic types: prestressing bars, prestressing wires, and prestressing strands. In Europe, they are produced according to DIN EN 10138 with strengths up to 2160 MPa. The prestressing steels are protected from corrosion in the alkaline environment of concrete. However, the necessary testing in these embedded conditions becomes even more challenging. Damage occurs through corrosion processes, especially cathodic stress corrosion cracking, which leads to brittle and sudden failure of the prestressing steel. Currently, about 4,500 highway bridges in Germany require repair or replacement.

On the international stage, prestressing steels with strengths up to 2360 MPa are already in use. These are largely unexplored in terms of their resistance to hydrogen embrittlement. Material investigations on these steels aim to clarify whether increasing the strength also increases the risk of hydrogen embrittlement or whether potential durability reserves can be identified. Mechanical testing in form of constant load tests is used to assess the mechanical properties of the prestressing steels in corrosive environments. These corrosion tests are conducted in accordance with DIN EN ISO 15630-3, Section 10. Micro morphological and micro analytical investigations will be used to demonstrate the damage mechanisms and highlight the critical level of hydrogen, generated by hydrogen induced stress corrosion cracking, particularly focusing on its diffusible content.