Modelling durability of reinforced concrete structures

ABSTRACT

Existing models for predicting the time to the commencement of serious reinforcement corrosion in chloride conditions provide results that do not compare well with long-term observations and practical experience for actual concrete structures. Many high-quality concrete structures show little or no evidence of serious corrosion, even after decades of exposure to chloride conditions. Earlier it was proposed that the mechanisms for corrosion initiation differ from those for long-term corrosion. This is reviewed. New research shows corrosion initiation is dominated by the presence of air voids adjacent to the reinforcement. For good concretes this is mainly a short-term transient effect. Long-term active corrosion is the direct result of the usually slow loss of concrete alkalinity, a process accelerated by chlorides. This, rather than direct chloride attack, is the cause of damaging reinforcement corrosion. It is argued also that the role of concrete cracking intersecting the reinforcement must be reconsidered. These new interpretations open up the way for improved modelling and prediction of ‘chloride-induced’ corrosion.

KEYWORDS:

• Corrosion
• reinforcement
• alkalinity
• structures
• pitting
• quality

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Correction

Acknowledgments

The support of the Civil Engineering laboratories at the University of Newcastle, in particular Ian Jeanes and Goran Simundic, the suggestion of (the late) Dr Dick van der Molen to try sulphate-reducing cement, the earlier research support of Dr Torill Pape and more recently Dr Igor Chaves in sample analyses and the support from Central Scientific Services at the University of Newcastle are all acknowledge with much gratitude. In addition, the helpful comments and suggestions from the reviewers are appreciated.

Disclosure statement

No potential conflict of interest was reported by the author.

ORCID

R. E. Melchers http://orcid.org/0000-0002-1068-4368

Additional information

Funding

This work was supported by Australian Research Council: [Grant Number DP0771695].