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1st Global Internet Corrosion Conference

InterCorr/96

Rebar Location and Cover Measurement
to Aid Corrosion Potential Surveys

John C Alldred MA, MSc, Protovale (Oxford) Ltd

Abstract

The measurement of half-cell potential at the surface of the concrete is one common and standard method of estimating degree of corrosion in reinforced concrete. Although this technique can be used on its own, there are advantages in combining it with a survey to locate the reinforcing bars and measure their cover.
The first advantage arises from the fact that it is necessary to expose and access one bar in order to connect the reference electrode. By being able to accurately locate a suitable bar, it is possible to minimise both the time taken in breaking out to the bar, and also the amount of reinstatement work necessary after completion of the survey.
The second advantage is in the interpretation of the half-cell potential readings. Although guidelines exist suggesting limits for estimating likelihood of corrosion, it is also known that absolute values of potential alone are not sufficiently reliable as indicators. A survey of concrete cover to the reinforcing steel can be used in conjunction with the survey of potentials to assist in the interpretation of the potential readings and to improve the assessment of likelihood of corrosion.
[Web] This paper presents some practical applications of this dual approach.
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