Concrete floors have changed their image in the last 30 years. Though formerly preferred in garages, warehouses and factory halls, they gained a place in modern interior design in the 1980s: high-quality concrete and cement-bound flowing-screed flooring that has been ground and polished is now considered chic. It adorns exhibition and retail areas, shopping arcades, bistros and museums. Even developers of exclusive residential areas have been won over by the unadorned elegance of a concrete flooring in kitchens and living rooms.

However, concrete flooring and cement-bound screeds and less abrasion resistant than they appear due to their porous surface. When subject to foot or wheel traffic, concrete floors shed material, which is later deposited as dust on nearby objects. When heavily stressed for longer periods, the flooring even becomes fragile. As a result of its porosity, the unprotected surface also absorbs spilled drinks, engine oil or other fluids. The result is ugly marks that cannot be removed.

However, day-to-day soils push many impregnation agents to their limits: WACKER chemist Dr. Udo Anders has tested some commercial concrete floor impregnation agents and ascertained that silicate-, and even silane-based agents only provide very limited stain protection in many applications - even for day-to-day soiling materials. What use is an impregnation that cannot deal with ketchup, mustard, red wine or cola? Despite impregnation, it is difficult to remove such stains and keep the floor looking like new. What is more, for toxicological and environmental-protection reasons, the construction industry is striving to avoid solvent-based systems.

“SILRES^® BS 6920 makes it possible for the construction industry to easily produce one-component impregnating agents that exhibit high scrub resistance for concrete and screed floors,” says ^{Dr. Udo} Anders The binder itself is solvent-free and can also be further processed without additives due to its low viscosity. But it can be diluted with solvents if needed. It is now possible to produce transparent impregnating agents that give concrete floors a glossy and polishable surface finish, even on rough surfaces. However, formulators can also mix in matting agents, pigments or reinforcing fillers and then reduce the viscosity by adding a solvent. In this way, the preparation produces a thin coating with a matt surface.

“SILRES^® BS 6920 is therefore the binder of choice when dealing with heavy stress from food, tire marks, foot traffic or vehicle traffic and the flooring needs to remain easy to clean,” adds marketing manager Udo Goedecke. The application possibilities of impregnation agents produced with this silane-terminated binder range from parking garages, car repair shops, train stations and logistics centers, through showrooms, catering facilities, event and convention centers to museums and residential buildings.

According to the EN 1504-2 standard, concrete impregnation is a treatment that partially or totallfills the pores of the concrete. Depending on the absorbency of the concrete and the quantity of the preparation used for the treatment, an ultrathin, non-uniform film also forms on the concrete surface. In comparison, the term coating applies if the treatment agent does not penetrate the pores and – instead of filling the pores – lies on the surface, bonds strongly and forms a sealed, thick film that also covers the pores. The film thickness of a coating is normally between 0.1 and 5.0 millimeters. Impregnations are generally produced using no-solids formulations based on SILRES^® BS 6920. Adding solids stops the formulation from penetrating deeply into the pores, producing a thin coating.

In the early 2000s, WACKER developed organofunctional alkoxysilanes that could couple to organic polymers and were also characterized by an exceptionally high reactivity to moisture. The reason for the reactivity lies in the structure of these silanes: one of the four binding partners of the silicon atom is a nitrogen-containing organic group, whose nitrogen atom is bound to the silicon atom via a methylene bridge. This short bridge creates precisely the distance needed between the two atoms for the nitrogen atom to facilitate release of the alkoxy groups from the silicon atom, thereby accelerating the reaction with water molecules. Silanes of this type are called alpha-silanes – in contrast to those containing the significantly longer propylene bridge, the so-called gamma-silanes. The reaction-accelerating effect is so great in the alpha-silanes that they react about 100 to 1,000 times faster than the corresponding gamma-silanes.

This high reactivity is not even affected when the alpha-silane is coupled to an organic polymer. For the alpha-silane-terminated polyethers WACKER has already performed the coupling, rendering the polymer crosslinkable: the reaction with moisture produces a siloxane network. However, WACKER also offers alpha-silanes that are not bound to a polymer. At WACKER, “alpha-silane technology” refers to the company’s entire product portfolio of alpha-silanes and alpha-silane-terminated polymers as well as its extensive chemical-technical expertise concerning these compounds.