Abstract
Electrochemical chloride extraction (ECE) is meant to re-establish the corrosion protection of concrete for the embedded reinforcement by removing chloride non-destructively and by enhancing the alkalinity of the rebar surrounding concrete. Both effects depend on various parameters, such as concrete cover, rebar spacing, chloride profile (especially if chloride ingress is deeper than the outside rebar layer) and concrete permeability. Often these parameters require long or multi-stage treatments, which basically can achieve any desired target level of chloride profile and impressed charge, but become a costly solution after a while. The acceptance criteria mentioned in CEN TS 14038-2 clause 8.6 refer to the achieved chloride content and to the amount of impressed charge, which are the conventional, easy measurable, but not direct parameters for evaluating the corrosion activity. A third parameter – the re-measurement of potentials for assessing (intended) low potential gradients and more positive average potentials – requires some weeks to months of depolarization and evaporation of water, before such a measurement can be applied successfully. A promising approach for an instant performance testing after an ECE treatment has been made on several occasions with follow-up measurements of electrolyte resistance, polarization resistance and corrosion current. Convincing changes towards significantly lower corrosion activity could be obtained (and compared to known classified values) – regardless of sometimes high residual chloride and very wet concrete. These data could be verified when re-assessed after some weeks, so enhanced corrosion measurements seem to be a useful tool for either establishing that the designed treatment time has been sufficient or to check on possible earlier termination of the treatment during a running ECE.
Highlights
During the past 8 years enhanced corrosion measurements (AC impedance, galvanostatic pulse measurement, linear polarization and Tafel polarization) have been increasingly used in corrosion survey projects of CITec, and the device applied for these measurements has been described in [1]
This information was received mainly by potential surveys that demonstrated significantly more positive values in the treated areas than before Electrochemical chloride extraction (ECE) and a low deviation from potentials in adjacent, chloride-free areas. Such conditions cannot be found immediately after terminating ECE, where the strong cathodic polarization enforces instant-off potentials < 800 mV vs. CSE, and in the usually very wet concrete it lasts some 3 to 6 months until equalized, stable moisture conditions allow a useful assessment of potential measurements
The following electrochemical test methods have been applied at different stages of the ECE: AC impedance: With this method it is possible to obtain the electrolyte resistance of the concrete in a 2electrode setup at a frequency of ca. 1 kHz
Summary
During the past 8 years enhanced corrosion measurements (AC impedance, galvanostatic pulse measurement, linear polarization and Tafel polarization) have been increasingly used in corrosion survey projects of CITec, and the device applied for these measurements has been described in [1]. General explanations about ECE are given for instance in [3] It has been observed from many projects, that much higher amounts of residual chloride than 0.4 %, related to the cement mass can be tolerated even in the rebar vicinity with proven elimination of corrosion activity. This information was received mainly by potential surveys that demonstrated significantly more positive values in the treated areas than before ECE and a low deviation from potentials in adjacent, chloride-free areas. The 3 case studies of this paper give good confidence in a promising approach
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
