In practice, hydrophobing impregnation has been established as an effective surface protection system against water and de-icing salt attack. Cracks in concrete, whether impregnated by a hydrophobing treatment or not, are unavoidable and can therefore lead to damage. In absorption tests on laboratory samples, the significant influences of cracks on the penetration behaviour of capillary water have been determined and quantified. The experimental results show that the water uptake depends on the craclc width and the penetration depth of the hydrophobing agent. There exists a 'critical' crack width depending on the penetration depth of the hydrophobing agent which can maintain the hydrophobing behaviour. Finally practical conclusions of the present work are draw
