The walls of the Mauritshal in the Groningen village of Zuidwolde – built in 2010 – have been made earthquake-proof with QuakeShield. But not in the now familiar way where grooves are milled into the wall; this time, holes were drilled into the wall from above. This is an idea of Marcel de Boer, project leader at the municipality of Bedum. It resulted in enormous time savings and less disturbance; demolition work is not required and the execution time is short. “We can be rightfully proud of this innovative approach”, says Rob Huyzer from the Centre for Safe Living.
You see only a sealed 16 mm drill hole on the upper side of the inner wall. The visible side of the inner walls, which is executed in MBI concrete stone, is fully intact. Concrete drilling company Bleeker from Winschoten – a company with which we frequently work – drilled a total of almost 100 holes in the walls, the majority of which are 2.5 metres deep. In the area where the storey floor lies on the walls, the drill had to be used up to three metres deep. Each drill hole was applied dead straight by using a tripod and a level. “How can we reinforce the sports hall without demolition and damage? This was the main question”, says Marcel de Boer, “We could achieve this by drilling from above. The carbon rods and adhesive were subsequently applied in the drill holes from above.”
Recognisable green adhesive was adapted
However, the specially developed tough elastic adhesive that is normally used for the grooves in the wall was too thick to completely fill the drill holes. This is why the viscosity of the epoxy was adapted specially for the Mauritshal. The ideal composition was found after a number of tests. “We used an old recipe that is a great deal thinner; it proved to work very well”, says Jan Folkert de Vries from QuakeShield. “But not all walls were treated in this way. A number of them, including those in the dressing rooms, were reinforced with milled grooves and finished with a mortar in the same colour as the wall.” We carried out the project together with contractor De Roo Bouw; a very pleasant and smooth cooperation. The construction company from Bedum was responsible for the preparatory activities and the finishing. “It was a great job with great people”, confirms Roel de Roo. “The cooperation went very well and ensured we only needed six weeks to successfully finish the job.”