Decreasing Humidity in Concrete Facades after Water Repellent Treatments

One of the tallest buildings in Stockholm is The Scraper (after skyscraper) built in 1959. The building is 81 m high and the facades are covered with precast concrete elements. The elements have several problems related to high moisture content. To replace all the facade elements would be expensive and the Swedish Cement and Concrete Research Institute was commissioned to find a method to save the old ones. The choice fell upon water repellent treatments in order to lower the humidity and a test was initiated with measurements of the RH (relative humidity) and temperature inside the elements (40 mm from the surface). Three sites on the building were chosen for the test. The first was on the ground level facing west, the second one on the roof facing north and the third one on the roof facing south. Three facades elements were treated with isooctyltriethoxysilane twice on the same day whereas two remained untreated on each test-site. The results are presented as average values on each test-site and they show that the RH could be lowered by 20 % under the right circumstances. The conclusions are based on two testing periods in 2003 and 2004, respectively.