Oberflächenschutzmassnahmen und Korrosionsinhibitoren für bewitterte Stahlbetonkonstruktionen

Surface Treatments and Corrosion Inhibitors for the Protection of Reinforced Concrete Structures

Abstract

Reinforced concrete structures exposed to weathering can suffer damage in different ways. Weathering and frost can, for instance, degrade the surface of the concrete or cause spalling. The consequences of rebar corrosion are very serious due to the fact that the load bearing capacity of structures may well be adversely affected. Corrosion of reinforcing steel takes place when the passivated shield of the steel surface has been destroyed by carbonation and/or chlorides.
Surface protection measures for concrete façades reduce the water absorption of concrete, thus decreasing its electrolytic conductivity, which in turn reduces or stops the corrosion process. Organic silicon compounds (silanes, siloxanes), applied to saturation onto the concrete surface, are most often used to this end. This kind of water repellents are not film-forming and do not alter the concrete's aspect.
Appropriate film-forming coatings do not only reduce the absorption of water, but can also prevent carbonation of the concrete. Acrylic dispersions, which have to be applied in a continuous and sufficiently thick and pore-free coat, are frequently used for this purpose. When using crack-bridging façade coatings, the necessary dry film thickness leads to a considerable loss of the concrete's original texture. Good water-vapour diffusion capacity is vital for all kinds of coatings.
Corrosion inhibitors for the protection of existing concrete structures are available since recently only. Inhibitors penetrate through the concrete and fix themselves onto the steel surface. The protective film formed in this way reduces access of oxygen to the surface of the steel and slows down the speed of the corrosion process.
Corrosion inhibitors do not alter the concrete's aspect, cannot be affected by any mechanical action on the concrete's surface and have an excellent price/performance ratio.