Silicon-based water repellents: Long-term performance evaluation by artificially accelerated ageing

The long-term performance of water repellents intended for use on external wall surfaces has been evaluated by subjecting test samples to UV radiation and water spray in a Weather-Ometer®. The exposure programme includes 5000 hours in order to simulate longer periods of natural exposure. In this paper, the testing programme is described and the results obtained after 2500 hours of exposure are compared with those of unexposed samples as well as naturally exposed samples. The repellent was applied to porous-rendered autoclaved aerated concrete substrates either by impregnation after surface rendering, or by mixing additive powder with the rendering. The performance parameters measured were capillary water absorption and evaporation.