Stress corrosion cracking of prestressing steels

During the investigation of a post-tensioned bridge structure incipient cra cks of the prestressing steels of the transverse prestressed members were o bserved. Defects related to non-injected ducts or the presence of corrosion inducing substances could not be detected. The prestressing steel used is a quenched and tempered steel, strength class St 140/160, which was produce d in the former GDR. The cause for the cracks is the susceptibility of this type of steel to hydrogen-induced stress corrosion cracking as could be sh own in laboratory tests. Under unfavourable conditions cracks can be initia ted before grouting. Additional magnetic particle tests at selected areas o f the longitudinal prestressed members did not indicate any signs for incip ient cracks.