Rissbildung infolge Bewehrungskorrosion

Cracking due to reinforcement corrosion. Mechanisms and prediction models

Current approaches for service life design of concrete structures define the end of the initiation period (depassivation of the reinforcement) as the critical limit state. It would be a significant improvement to specify the occurring damage as a limit state, i. e. the condition when cracking due to reinforcement corrosion appears. However, this is not yet possible since the time interval between the end of the initiation period and the cracking of cover concrete is unknown. The solution of this unsolved problem is of high importance since the unknown time interval may last between few months and decades. The latter could imply that an elaborate service life design based on the limit state depassivation of the reinforcement is obsolete.
Against this background the present paper is dealing with the propagation period, i. e. with the processes after the end of the initiation period and the cracking due to reinforcement corrosion. The results of a comprehensive scientific research project are summarized. They allowed for the development of a model which enables to calculate the time interval between depassivation (start of corrosion) and damage occurrence (cracking, spalling) for different exposures and concrete technical conditions. A further successful outcome, which is based on novel experiments and a special test configuration, is the first constitutive law for rust that is formed under practical conditions within the transition zone between the reinforcing steel and concrete.