Museum De Lakenhal in Leiden:

Danish brick places high demands on masonry mortar

The masonry of the exterior walls of the new wing of Museum De Lakenhal in Leiden is done with a Danish brick, the so-called Petersen brick. A special brick, which makes high demands on the masonry mortar. Remix Dry Mortar was able to develop exactly the right mortar for this, thanks to its Mortar-to-measure system.

"Museum De Lakenhal is an impressive project and beautiful to work on," assures Jan Jousma, product manager at Remix Dry Mortar. "Because of the Petersen stone, it was also quite a challenge. This brick has a hard exterior but an enormously high water absorption capacity. With standard mortars, the stone sucks up moisture for a long time and eventually all the water from the mortar. As a result, the mortar burns and no longer provides adhesion and strength. Walls have already toppled in Denmark and Norway due to the wrong choice of mortar."

Unique strike-through mortar

The Lakenhal construction consortium asked several mortar manufacturers who could supply a suitable strike-through mortar for this brick. Jousma: "We were the only ones who could. We collected bricks from the construction site and examined them in our laboratory. With the Mortar-On-Masure system we developed, we can put together a mortar that is tailored to the brick, the type of masonry, the climatic conditions, the construction site conditions and the intended number of layers per day. We are unique in that."

In addition, the mortar developed also had to match the existing historic masonry of Museum De Lakenhal. "We therefore applied a coarser grain, giving the joints a somewhat rougher appearance. We also brought the mortar to the desired color. Due to the high water retention capacity of the mortar, the Petersen brick does not suck out too much moisture and the good adhesion gives strong masonry."

Good workability

Two silos were placed on the construction site, one for the exterior work with the Petersen brick and one for the interior work, which mainly involved repairs. Jousma: "We could always refill those silos with our bulk trucks, which also saved a lot of transportation. No special instruction was needed for the masons; a trial wall was sufficient. The low efflorescence (UA) permeable mortar we developed was very easy to process and spread. The result is to be proud of. We are now exporting this mortar to Denmark and Norway."