Unlike in the UK, there are currently no problems in the Netherlands with buildings constructed of RAAC concrete or aerated concrete. There are only concerns, according to an NOS tour.
In the UK, hundreds of schools built between the 1950s and 1980s may have to close because the RAAC concrete used to build them tends to rot. If the concrete rots, it may collapse.
There are also post-war buildings in the Netherlands in which aerated concrete was used, including schools. “But our members don't know the problems like in England,” says Bob Gieskens of VN Constructeurs, the trade association for builders.
Don't panic, just worry
Sander Pasterkamp, professor of building technology at TU Delft, doesn't 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 depends on maintenance. Moisture can cause damage. At first you don't see anything problematic, then it's suddenly too late and the material can come loose. So aerated concrete is not not a bad material, but it depends on maintenance.”
The builders of the construction company Arcadis also claim that, to their knowledge, aerated concrete in the Netherlands does not cause any problems, provided, for example, that the roof is properly maintained.
Earlier this year, a piece of concrete came loose at a school in Rotterdam. This is due to a so-called MuWi system, in which the floor consists of concrete beams with lightweight concrete infill elements.
The MuWi system is different from aerated concrete, explains Pasterkamp, professor of structural engineering. “But if school boards look in the archives for the materials their school is built with, they should also check whether aerated concrete was used,” he says.
Last month, the Deputy Minister of Housing and Public Housing, De Jonge, asked municipal authorities to check whether school buildings in their municipalities have certain floors that can collapse.
Xella is the only aerated concrete manufacturer in the Netherlands. The company is surprised by the problems in the UK. “Our material is mainly used for industrial halls, distribution centers and warehouses,” says spokesman Han den Hartog. Concrete is used to separate spaces and for fire protection. He is not aware of any problem.
Other companies that work with aerated concrete also claim that they have no problems. The Department for Education, Culture and Science cannot yet say whether the UK concrete issues will prompt further research in the Netherlands.
“But we are not taking any risks,” the ministry said. The Ministries of the Interior and of Education, Culture and Science claim to check whether the system in question is also used in Dutch school buildings.