Unlike in the United Kingdom, there are currently no problems in the Netherlands with buildings built with RAAC concrete or aerated concrete. There are only concerns, according to a tour of the NOS.
In the UK, hundreds of schools built between the 1950s and 1980s may have to close because the RAAC concrete used to build them is prone to rot. If concrete rot occurs, there is a chance that they will collapse.
There are also post-war buildings in the Netherlands in which aerated concrete was used, including schools. “But problems such as in England are not known to our members,” says Bob Gieskens of VN Constructeurs, the trade association for constructors.
Don’t panic, just worry
Sander Pasterkamp, lecturer in construction technology at TU Delft, does not see any immediate problems either. “Aerated concrete is used here for roof or facade panels, although on a smaller scale than in England.” According to him, there is no reason to panic, but there are concerns, he says.
“The safety of aerated concrete stands or falls with maintenance. Moisture can cause damage. At first you see nothing problematic, then it is suddenly too late and the material can come loose. Aerated concrete is therefore not a bad material, but it depends on maintenance .”
Constructors from construction company Arcadis also say that aerated concrete in the Netherlands does not cause any problems, as long as the maintenance of the roof, for example, is good.
Earlier this year, a piece of concrete came loose at a school in Rotterdam. This was due to a so-called MuWi system, in which the floor consists of concrete beams with lightweight concrete filling elements.
The MuWi system is different from aerated concrete, explains structural engineering teacher Pasterkamp. “But if the school boards look in the archives at the material with which their school is built, let them also check whether aerated concrete has been used,” he says.
Last month, outgoing Minister of Housing, De Jonge, asked municipal authorities to check whether school buildings in their municipalities have certain floors that can crumble.
Xella is the only manufacturer of aerated concrete in the Netherlands. The company is surprised by the problems in the United Kingdom. “Our material is mainly used for industrial halls, distribution centers and warehouses,” says spokesperson Han den Hartog. The concrete is used to separate spaces and for fire protection. He is not aware of any problems.
Other companies that work with aerated concrete also say they have no problems. The Ministry of Education, Culture and Science cannot yet say whether the British problems with the concrete will prompt additional research in the Netherlands.
“But we are not taking any risks,” the ministry said. The ministries of the Interior and Education, Culture and Science say they are checking whether the system in question is also used in Dutch school buildings.
- Hundreds of schools in the UK are at risk of closing due to the risk of collapse