Extending service life by coupling the limit state of corrosion initiation and corrosion induced cracking

The service life design of reinforced concrete structures requires models capable of reliably describing both the mechanisms of damage and its progression over time. For concrete exposed to chlorides, service life design typically disregards the onset of damage, i.e. the progress of corrosion of the reinforcing steel. Common service life design practice typically considers the end of the initiation phase of the degradation process as the design limit state. A method is proposed where a model for estimating the time to corrosion initiation is coupled with a model for estimating the time to corrosion induced cracking into a single limit state determination. An example is provided of a structural element that has been designed for the serviceability limit state of corrosion induced concrete cover cracking. The results show that the corrosion rate is a major factor for the coupled service life determination. Where fast corrosion is expected, service life extension is insignificant, and where slow corrosion rates are expected, service life extension can be significant.