Pouring underwater concrete requires specialist knowledge

Nice challenge: Pouring concrete on a 10 percent slope

As specialists in civil underwater construction, the people of DISA International dive underwater for the construction, maintenance and repair of large civil infrastructure projects. They are also coming into action for the reinforcement of the Afsluitdijk. “A wonderful project where all the elements of our work come into play,” he says.

Ideally, DISA joins as early as the design phase of a project. “Because,” says superintendent Marc Veldhuizen, ”we like to think along in the preparation about underwater solutions. We increasingly notice that many companies lack the knowledge and experience in this specific area. Civil underwater construction is our specialty and so we are called in to think along. For example, we collaborated on the Maasdelta and Holland Tunnel, De Groene Boog and OPENIJ. In all our projects, including the renewal of the Afsluitdijk, our customers appreciate our innovative, safe and reliable approach. Since this year, we as a company have also achieved Safety Ladder step 4.”

Underwater solutions

One of the solutions DISA provided was how to pour underwater concrete on a 10 percent slope. Superintendent Cecil de Groot explains: “In two construction pits on the Wadden Sea side of the Den Oever pumping station there is a 10 percent slope. Such a slope is quite unique. You can imagine that if you start pouring concrete here, it will soon flow away. We solved that by placing reinforcement baskets with curb steel on them that ensured that the slope of the concrete was maintained and prevented sagging. We also made the consistency of the concrete slightly thicker. We also prepared the reinforcement completely in terms of drawing work for LevveL and eventually the placement and execution. We also provided the sheet piling with a special sealing joint to absorb any movement of the wall. This too we completely figured out in advance with LevveL.” In addition to pouring underwater concrete, DISA's diving teams carried out dam wall burning, welding and various construction work underwater in preparation for pouring underwater concrete, among other tasks. In total, an average of four dive teams are at work performing the various tasks.

Depth sensor

Measurement under water is carried out to the nearest centimeter thanks to depth sensors. Whereas in the past someone above the water accompanied the diver with a steel line with weights, the depth sensor is now used. Marc: “All our diving teams are equipped with such a sensor. In addition to depth measurement, it can also measure whether an object is level. The sensor works quickly and efficiently. For everything we need to measure in, we use it. What used to take you maybe two days, we now do in a few hours. We are one of the few companies working with it.”

Weekly consultation

To keep everything running smoothly and on schedule, there are weekly consultations at the construction site. “The cooperation is very good. By discussing things on site every week, you keep your finger on the pulse and can make quick adjustments when necessary.”