The reinforced concrete structures are designed and built for a service life, which is defined by the designer and is controlled by the manufacturer. For this period of time, the structure should not be so deteriorated that it does not fulfill any more its functions.

The deterioration of reinforced concrete is mainly due to reinforcement corrosion The mechanism of this deterioration is to be reminded. Reinforcements corrode when they are in contact with a high amount of aggressive agents. This is the reason why, the prevention of reinforcement corrosion, in structures to be built, is obtained mainly by controlling the thickness and the quality of the concrete cover.

The design of traditional concrete, in particular its cement dosage and its water-cement content ratio, depends on the environment to which this material is exposed.

In very particular cases, additives can be added in the freshly-mixed concrete to improve of its workability, its mechanical properties and more rarely its protective qualities.

The concrete cover thickness around reinforcement also depends on the environment aggressiveness. But, in addition to the requirements given by the designer, it is significant to consider the implementation (reinforcements positioning, concrete mixing, curing, etc.) to estimate the durability of a reinforced concrete really in place.

When reinforced concrete structures are exposed to a very aggressive environment, an additional protection can be considered by cover steel. The two types of the most frequent covers on steel are organic coatings and metal coatings (hot-dip galvanising, etc).

These protective coatings which must adhere to steel must also ensure good a bond between reinforcement and concrete.

Protection against corrosion can also be to improve using a coating on concrete.

Other similar means are available (concrete impregnation).

When reinforcements are strongly corroded, their corrosion products can expand, and deteriorate the concrete cover, by cracking, delamination and spalling.

Then, the first action to be undertaken is to eliminate these geometrical defects, by replacing concrete cover, or sometimes injecting cracks.

As this first action relates to only the zones under high corrosion, the close zones, where corrosion can appear in a short term, must be treated by other methods.

In some cases, concrete reinforcement can be depassivated (i.e. corroding) or will corrode shortly. Its cover seems physically satisfactory and has neither crack or delamination. But, it is then convenient to slow down this corrosion rate, even to stop it.

The methods which can be proposed are either concrete impregnation with water-proof products (sealants) or inhibitors, or an electrochemical treatment : cathodic protection, re-alkalisation or chloride extraction.

When reinforcement is embedded in a sound cover and its corrosion is likely initiated only in short or long term, it can be useful to protect them by impregnating concrete cover.

Paintings and coatings of various thickness can also be applied on concrete to improve its resistance to liquid penetration. It deals, for example, with either of coatings containing epoxy resin or polyurethane, or with mortar containing modified hydraulic binder.

    European standard EN 12696 " Cathodic protection of steel in concrete " (July 2000).

    Draft standard prEN 14038-1 " Electrochemical re-alkalisation and chloride extraction for reinforced       concrete. Part I : Re-alkalisation ".

    LCPC