Electrochemical treatments of reinforced concrete 
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The objective of an electrochemical treatment on reinforced concrete is to slow down or to stop reinforcement corrosion, by acting on the interface between steel and concrete. Its principle is as follows.

A reinforcement, which is embedded in concrete, is connected to a unit called anode, which is a metal "plate", embedded in either a wet paste or a mortar. A direct electrical current is applied between reinforcement and anode. This current flows in concrete, from the anode towards reinforcement.

In the traditional processes, the current is due to a power source, such as a rectifier or a generator. In this case, the anode is connected to the positive terminal of the source. In the process called with galvanic anode, this anode is not made of steel, but of another metal. This nature difference can produce an electrical current, if these materials are connected to each other, by a wire and a wet conductive medium. The electrical circuit includes here the embedded anode and concrete.

The electrical current which flows in concrete, can change its chemical composition, especially near reinforcement. These changes can give concrete, its initial protective properties for reinforcement.





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Cathodic protection : If the current between reinforcement and anode is low, about 0,01 A/m² (reinforcement area), only the direct interface between steel and concrete is concerned. This cathodic protection is applied permanently, so that its effect is continuous. The anode is often coated with mortar. This treatment is detailed and specified in the European standard EN 12696.


Power supply for a cathodic protection system for reinforcement in a bridge

Re-alkalisation : If the current is about 0,5 A/m² a concrete ring formed around reinforcement, is concerned with this treatment. Its description is in the Technical Sheet CEN TS 14038-1. If the concrete cover is previously carbonated (its pH is approximately 9 as compared to 12 for a sound concrete), this treatment can give back this concrete its original pH. The effect of this re-alkalisation process remains after the current is switched off. This is the reason why the anode and its cover are removed after a treatment, which lasts between a few days and a few weeks.



Re-alkalization of concrete cover around a reinforcement
The paste embedding anode is saturated with an alkaline liquid, which enters concrete.


Chloride extraction by an electrochemical treatment

Embedding anode with a paste, for a re-alkalization treatment with applied current

Embedding anode with a paste, for a re-alkalization treatment with galvanic anode

Chloride extraction : If the current is about 1 A/m², the treatment concerns concrete placed between reinforcement and facing. Its description is in the Technical Sheet CEN TS 14038-2. If this concrete is previously polluted with chlorides coming from the environment, the treatment can remove chlorides towards outside. The effect of this process of chloride extraction remains after the current is switched off. So, the anode and its cover are removed at the end of the treatment, which lasts a few weeks.

The effectiveness of a re-alkalisation treatment is determined by applying a colour pH indicator to concrete cores taken close to reinforcement. The effectiveness of a chloride extraction treatment is assessed by determining chloride content at various depths in concrete.



Chloride extraction by an electrochemical treatment

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