Abstract:For reinforced concrete structures the conventional wisdom is that after some years of exposure to marine conditions reinforcement corrosion is inevitable. Much attention is paid in the literature to the rate of ingress of chlorides through the concrete cover to the reinforcing bars and to ensuring highly impermeable cover and/or deeper cover, to try top prevent chloride-induced or carbonation-induced corrosion initiation. Actual field experience shows that there are many reinforced concrete structures that ha… Show more
“…Figure 1 shows an example for which there is useful background information [38]. This case and many others have a number of features in common, including [28,29,39]:…”
Section: Observations From Rc Structuresmentioning
confidence: 99%
“…Figure 1 shows an example for which there is useful background information [38]. This case and many others have a number of features in common, including [28,29,39]: Very high levels of chloride concentrations on reinforcing bars do not necessarily ‘cause’ other than very minor corrosion, and often no visual evidence of corrosion at all, for many years, often decades.For high-quality concretes, the onset of serious, damaging corrosion is considerably later in time than any measure of corrosion initiation.The causative mechanism(s) for the commencement of serious reinforcement corrosion remain unclear but do not appear to be the same as those for corrosion initiation.Very serious localised reinforcement corrosion without obvious external signs of corrosion such as rust staining and concrete cracking or spalling can and does occur, but clear explanations for such corrosion remain outstanding. Figure 1 End and side view at low tide in 2009 of a Phoenix caisson similar to those used for the WW2 Normandy invasion, beached in Langstone Harbour, UK. The caisson was constructed on the adjacent coastline (Hayling Island) and broke its back (in 2 places) during launching in 1943.…”
Section: Observations From Rc Structuresmentioning
confidence: 99%
“…Increasingly it has become clear that the mechanisms involved in reinforcement corrosion are more complex than simply the direct action of chlorides on the steel of the reinforcement. In what follows it is proposed that progress can be made in elucidating the mechanisms involved by using observations from actual concrete structures, particularly those that have shown, overall, excellent resistance to reinforcement corrosion, over extended periods of time [12,[27][28][29].…”
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.
“…Figure 1 shows an example for which there is useful background information [38]. This case and many others have a number of features in common, including [28,29,39]:…”
Section: Observations From Rc Structuresmentioning
confidence: 99%
“…Figure 1 shows an example for which there is useful background information [38]. This case and many others have a number of features in common, including [28,29,39]: Very high levels of chloride concentrations on reinforcing bars do not necessarily ‘cause’ other than very minor corrosion, and often no visual evidence of corrosion at all, for many years, often decades.For high-quality concretes, the onset of serious, damaging corrosion is considerably later in time than any measure of corrosion initiation.The causative mechanism(s) for the commencement of serious reinforcement corrosion remain unclear but do not appear to be the same as those for corrosion initiation.Very serious localised reinforcement corrosion without obvious external signs of corrosion such as rust staining and concrete cracking or spalling can and does occur, but clear explanations for such corrosion remain outstanding. Figure 1 End and side view at low tide in 2009 of a Phoenix caisson similar to those used for the WW2 Normandy invasion, beached in Langstone Harbour, UK. The caisson was constructed on the adjacent coastline (Hayling Island) and broke its back (in 2 places) during launching in 1943.…”
Section: Observations From Rc Structuresmentioning
confidence: 99%
“…Increasingly it has become clear that the mechanisms involved in reinforcement corrosion are more complex than simply the direct action of chlorides on the steel of the reinforcement. In what follows it is proposed that progress can be made in elucidating the mechanisms involved by using observations from actual concrete structures, particularly those that have shown, overall, excellent resistance to reinforcement corrosion, over extended periods of time [12,[27][28][29].…”
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.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
