Corrosion monitoring of steel in concrete - theory and practice.

Maintenance and planning of the restoration work on reinforced concrete structures need a rapid, non-destructive inspection technique that detects corrosion at an early stage. In this paper the results of potential surveys on several bridge decks of the Swiss highways, realized with a new computer controlled eight-wheel measurement system, are presented. It is clearly shown that a fixed potential value (as proposed in ASTM C 876-80) for the identification and location of active corrosion of steel in concrete does not exist. A very rapid new technique using galvanostatic pulse measurements was tested successfully on site. It gives clear, unambiguous results on the corrosion state of the rebars when half-cell potentials are uncertain. In addition, the concrete resistivity and the corrosion rate of the rebars may be estimated simultaneously. (A)