How does chloride extraction work for chloride contaminated concrete?
Electrochemical desalination or chloride extraction involves a technique whereby a current is passed through the concrete to the reinforcement by means of an externally applied anode, which is temporarily attached to the concrete surface. A paste of sprayed cellulous fibre with a conductive solution is normally used as the electrolyte covering the concrete surface.
The duration of the treatment is typically between 4 to 10 weeks. A variety of electrolytes can be used. During treatment, chlorides migrate out of the concrete towards the external anode and are collected in the electrolyte reservoir. At the same time, hydroxyl ions are produced at the surface of reinforcement re-passivating the steel reinforcement.
This technique has not been used extensively in Australia due to the fact that most of the problems associated with chloride induced corrosion are in tidal and splash zones. The application of this system is not appropriate under these conditions as ingress of chloride cannot be prevented in these areas after the completion of the chloride extraction process. For structures away from tidal and splash zones, prevention of new chloride ingress after the chloride extraction process requires that the concrete is protected by an anti-chloride protective coating.
Key features of this technology are:
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Environmentally friendly: Major reduction of concrete breakout.
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Low maintenance: No requirements for permanent system for monitoring.
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Long term global protection: Provides effective treatment for the entire area of application.
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Proven technology: Long history and an excellent track record.
Our recommended application:
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Chloride contaminated structures that are not subject to constant exposure to salt contamination such as tidal and splash zones in marine environment.
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Magnesite floors and car parks.
Standards:
Electrochemical realkalisation and chloride extraction treatments for reinforced concrete, CEN / TS 14038 -1.
Standard Practice: Electrochemical realkalisation and chloride extraction treatments for reinforced concrete, NACE SP0107-2007.