The results of potential mapping surveys of bridge decks of the Swiss highways, realized with a new eight-wheel electrode measurement system, are reported. Several effects on the potential field (concrete cover, humidity, chloride content) are discussed. A comparison of the state of corrosion of the rebars (obtained by visual inspection after removing the concrete cover) with the potential fields and theoretical considerations, clearly demonstrate that an absolute potential value (i.e. --350 mV CSE as proposed in ASTM C876-80) for the identification of active corrosion of steel in concrete does not exist. Combining the local potential gradient on the surface with information on the electrical resistivity of the concrete allows determination of a rough estimate of the corrosion rate in a single macro-cell. A very rapid new technique--galvanostatic pulse measurement--has been tested successfully on site. It gives unambiguous results for the corrosion state of the rebars when half-cell potential measurements are uncertain.
Potential Mapping of Steel in Concrete
ELSENER, BERNHARD;
1988-01-01
Abstract
The results of potential mapping surveys of bridge decks of the Swiss highways, realized with a new eight-wheel electrode measurement system, are reported. Several effects on the potential field (concrete cover, humidity, chloride content) are discussed. A comparison of the state of corrosion of the rebars (obtained by visual inspection after removing the concrete cover) with the potential fields and theoretical considerations, clearly demonstrate that an absolute potential value (i.e. --350 mV CSE as proposed in ASTM C876-80) for the identification of active corrosion of steel in concrete does not exist. Combining the local potential gradient on the surface with information on the electrical resistivity of the concrete allows determination of a rough estimate of the corrosion rate in a single macro-cell. A very rapid new technique--galvanostatic pulse measurement--has been tested successfully on site. It gives unambiguous results for the corrosion state of the rebars when half-cell potential measurements are uncertain.
I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
