Sustainable concrete rehabilitation of bridges is not a pipe dream!

Concrete is a strong and durable building material that is frequently used for the construction of bridges, tunnels and bridge basements. However, this concrete is also subject to aging and may suffer damage under the influence of external factors.

Many bridges in Belgium show damage and are in urgent need of repair. Concrete damage to bridges and bridge basements is mainly caused by external influences such as carbonation, water infiltration, chlorides from de-icing salts or in a maritime environment, mechanical stress, .... Concrete damage, if the correct repair method is followed, can be repaired in a sustainable manner. Provided additional protection after repair, the service life of these structures is significantly extended.

The disposal of demolition waste and the production and supply of new concrete causes very high CO2 emissions. Therefore, sustainable concrete repair contributes greatly to a better environment and climate.

FEREB vzw is the Belgian Federation of specialists in concrete repair, reinforcement and protection. Together with its members, it has been campaigning for years for sustainable concrete repair. It also developed a step-by-step plan based on the NBN 1504 standard.

A durable concrete repair starts with a preliminary study or diagnosis, performed by an architect or specialized engineering firm. This preliminary study is necessary to determine the extent and especially the cause of the damage. In addition to a visual inspection, it includes some simple tests such as determining the depth of the reinforcement, measuring the hardness of the concrete and a test for the presence of carbonated concrete. If necessary, even more in-depth tests can be carried out by a specialized laboratory on the presence of chlorides, for example, based on samples.

Once the cause and extent of the damage have been identified, a specification text can be drawn up. This defines the repair method and the appropriate repair mortars, CE-labeled and preferably Benor-certified. This immediately includes consideration of what protection should be provided to avoid future damage. Think for example of cathodic protection.

The repairs must be carried out with care by experienced and preferably Benor-certified contractors. Indeed, these certified workers followed a theoretical and practical training course on "sustainable concrete repair" at BCCA for this purpose.

Concrete repair starts with the removal of the loosened parts. This is done by manually hacking away, usually with a pneumatic hammer and increasingly by hydrodemolition. Then the reinforcement is de-rusted and, if necessary, treated with a bonding mortar. Finally, the appropriate repair mortar is applied manually or mechanically and smoothed afterwards.

The contractor will make the necessary checks during and after the execution of the works. For carbonated concrete, for example, it is necessary to check whether the concrete around the corroded reinforcement has been removed sufficiently deep (to behind the reinforcement). This check is done using a phenolphthalein test. The adhesion of the repair mortar to the existing concrete surface should also be tested.

To extend the service life of repaired concrete structures such as bridges, bridge basements and tunnels, it is preferable to apply protection in the form of a coating or impregnation. This protects the concrete surface, for example, from penetration of moisture, action of chemicals, abrasion or fire. Bridges exposed to de-icing salts and bridge cellars in maritime environments are often affected by chlorides. Cathodic protection is often provided here. During repair work, sacrificial anodes are applied to the rusted reinforcement. The technology of cathodic protection with imposed current is also used more often. Thanks to the technology of cathodic protection, the service life of the concrete structure can be extended by more than 25 years.

Finally, continuous monitoring and maintenance of the repaired concrete structures ensures a long service life.

Then contact the specialized members of FEREB asbl for a diagnosis, the drafting of specifications and the execution of concrete repair and protection. You can find the list of members at
the website.

Then attend the seminars on May 23 (hydrodemolition) and June 16 (cathodic protection). For the program and registrations, please visit the website.