Four Brussels tunnels in new look of concrete

The large-scale renovation of the Brussels tunnels is in full swing. As a specialist in concrete renovation, Renotec could not fail to be involved. "Our teams are carrying out the concrete repairs from A to Z and applying more than 40 kilometers of titanic strips for cathodic protection in the Troon, Boileau, Tervuren and Naamsepoort tunnels," explains project manager Jens Van De Putte. A technical feat in which Renotec pulls out all the stops to meet the strict deadlines.

The Brussels Region put a multi-year investment program on the table for the Brussels tunnels in 2016 after inspections revealed that they were in urgent need of renovation. Since then, the tunnels have been undergoing a phased overhaul. In February last year, Renotec was awarded the contract for the concrete renovation of the Troon, Boileau, Tervuren and Naamsepoort tunnels. "Not only was the lowest price considered, but our Plan of Action was also qualitatively assessed," explains technical director Jo Vandernborne. "The intensive work that preceded this plan paid off because our expertise was the deciding factor in choosing Renotec." 

Renotec's assignment consists of the concrete renovation and cathodic protection of the ceilings of the four tunnels. Van De Putte explains his team's approach: "After removing the wall panels, all concrete rot in the (concrete) tunnel roofs is removed by hydrodemolition. Then we carry out all concrete repairs using the wet spray method, a technique that we have mastered like no other thanks to our years of experience. Furthermore, we ensure that the tunnels are 100% watertight using injections. We also apply the relatively new technique of cathodic protection in the tunnels, at least as far as the application in Belgian tunnel roofs is concerned. Specifically, this means that we will protect the reinforcement by placing titanium strips and imposed current."

Several techniques come together in one project here. This means that the tunnels present quite a challenge in terms of coordination, because in addition to the actual renovation work, Renotec also coordinates, among other things, the cleaning, hydrodemolition, asbestos removal and the dismantling and reinstallation of all techniques and signage. "It's like a little train of our own teams and sub and ancillary contractors, who all need to know exactly what to do in time. It is our job to keep the little train running and so far we have succeeded smoothly, to the great satisfaction of our client," Vandernborne said. 

In other words, efficiency is the key word, also because the project has a very short lead time. "We were awarded the contract at the end of February 2022, after which we immediately started the study phase. During this, we created test surfaces and viewing windows during the nighttime closures of the tunnels. This is our first large-scale tunnel renovation project in Brussels, so it also took some doing in terms of permits," says Van De Putte. "In collaboration with the engineering office, the plans were worked out so that we could start the actual execution on May 16, 2022." 

Now the tunnels are closed during the day. A partition wall divides the tunnels into two halves, allowing Renotec to work in two phases of three months each. In the third and final phase - which will be completed in the second quarter of 2023 - the concrete repairs, cathodic protection and overlay will be carried out in the places now inaccessible because of the partition wall. "This phase will be done exclusively in night work. In the morning, the entire site will have to be demobilized because traffic will have to pass through the tunnel again. From an organizational point of view, this means another major challenge," Van De Putte says. 

"Renotec starts where another contractor stops," states Vandenborne. "That is one of our company philosophies that we are once again living up to on this project. We were one of the first to master the spray method and have perfected the technique over the years. Today we are also pioneers in the field of cathodic protection as far as application in tunnels is concerned. In the Brussels tunnels, we are applying the technique on a large scale for the first time. In that respect too, the project undoubtedly adds value to our record of achievements." 

"Furthermore, we are also demonstrating our agility. We had to move very quickly in order to meet the deadlines, and we did so successfully. Of course, the daily efforts of our workers should not be forgotten either," concludes the technical director.