On the corrosion risk presented by chloride bound in concrete

In previous work the influence of the solid phases of cement hydration on the pore solution chemistry during corrosion initiation has been discussed. It was noted that, because a fall in local pH is necessary for stable pits to develop on the passive steel, much of the chloride bound in concrete may...

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Bibliographic Details
Published in:Cement & concrete composites 2002-02, Vol.24 (1), p.1-5
Main Authors: Reddy, B, Glass, G.K, Lim, P.J, Buenfeld, N.R
Format: Article
Language:English
Subjects:
Bound chloride
Chloride threshold
Concrete
Corrosion
Passive steel
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Summary:In previous work the influence of the solid phases of cement hydration on the pore solution chemistry during corrosion initiation has been discussed. It was noted that, because a fall in local pH is necessary for stable pits to develop on the passive steel, much of the chloride bound in concrete may participate in the process of corrosion initiation. At least two phases in hydrated ordinary Portland cement (OPC) will release such bound chloride before the pH falls to 11. In this work, these studies have been extended to include OPC blended with 10% calcium aluminate cement (CAC) and sulphate resisting Portland cement (SRPC). Evidence of a third phase that releases bound chloride was uncovered. Once again the data confirms that most of the bound chloride will be released by a relatively small reduction in pH. The release of chloride at such a high pH value compared to that required to sustain passive film breakdown suggests that the corrosion risk presented by bound chloride may be very similar to that presented by free chloride in concrete.
ISSN:0958-9465
1873-393X
DOI:10.1016/S0958-9465(01)00021-X