Determination of the corrosion rate of steel reinforcements in concrete

Abstract

Corrosion of reinforcing steel in concrete is the most serious problem, resulting in the loss of performance of concrete structures today. Quick and effective means of assessing the extent and severity of active corrosion are needed by engineers so that remedial measures may be taken at a cost effective stage. Potential mapping is a technique that has been very successfully used on in situ structures to locate active corrosion regions, but the method gives no information about the rate of corrosion. It has been proposed that a measurement of the electrical resistivity of the concrete used in conjunction with potential mapping can be used as an indicator of the rate of active corrosion. -In this thesis discussion will be concentrated on undertaking resistivity measurements of in situ concrete using non-destructive testing methods. Results can be automatically stored and output graphically to enable the quick assimilation of a large data base. Some of the problems that are encountered when carrying out the resistivity measurements, such as the presence of a reinforcing bar or a moist surface layer from recent rainfall can cause error in determining the underlying concrete resistivity. Guidance is given on methods for avoiding or allowing these problems and obtaining a realistic assessment of resistivity of the studied concrete.