Potential mapping is a widely applied and accepted non-destructive measuring technique to assess the condition of concrete structures with respect to corrosion of the embedded reinforcement steel. Most often a single reference electrode is used to perform point measurements according to a predefined grid. At present there is much debate on the appropriate potential level to allow for a distinction between passive and actively corroding steel. In the RILEM recommendation for half-cell potential measurements, a statistical analysis of the results of potential mapping is advocated in order to arrive at an improved quantification of this potential region pertaining to the structure under investigation. However, the underlying calculation procedure has not been elaborated and consequently there is no practical and unambiguous guidance for the consulting engineer on how to perform such a statistical analysis. In this paper, the theory for the statistical analysis is presented based on the assumption that the potential distribution for both actively corroding and passive steel can be adequately described by a normal probability density distribution. This theory is applied to a number of situations to exemplify the procedure by clear graphs. The potential criteria derived will demonstrate a significantly smaller range as compared to the criteria presented in ASTM C 876. Moreover, with this statistical analysis any desired probability level of detection of corroding reinforcement steel can be chosen.
Development of a calculation procedure for the statistical interpretation of the results of potential mapping performed on reinforced concrete structures
ELSENER, BERNHARD
2009-01-01
Abstract
Potential mapping is a widely applied and accepted non-destructive measuring technique to assess the condition of concrete structures with respect to corrosion of the embedded reinforcement steel. Most often a single reference electrode is used to perform point measurements according to a predefined grid. At present there is much debate on the appropriate potential level to allow for a distinction between passive and actively corroding steel. In the RILEM recommendation for half-cell potential measurements, a statistical analysis of the results of potential mapping is advocated in order to arrive at an improved quantification of this potential region pertaining to the structure under investigation. However, the underlying calculation procedure has not been elaborated and consequently there is no practical and unambiguous guidance for the consulting engineer on how to perform such a statistical analysis. In this paper, the theory for the statistical analysis is presented based on the assumption that the potential distribution for both actively corroding and passive steel can be adequately described by a normal probability density distribution. This theory is applied to a number of situations to exemplify the procedure by clear graphs. The potential criteria derived will demonstrate a significantly smaller range as compared to the criteria presented in ASTM C 876. Moreover, with this statistical analysis any desired probability level of detection of corroding reinforcement steel can be chosen.
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