When reinforcing steel corrodes in concrete, the results are all too familiar. Electrical current flows from the corroding bar, rust forms, and the pressure caused by rust buildup may pop off the concrete cover. How long it takes for this to happen depends primarily on the moisture and chloride content of the concrete. Drying out concrete after it has cured, and then keeping it that way, is an effective means for preventing corrosion. Reducing the ease with which chlorides penetrate the concrete also helps. One way to keep out water and chlorides is to apply a silane material, more specifically, one containing alkyltrialkoxysilane.
Unlike coatings, oils and other currently used sealers, silanes don't block the pores in concrete. Instead, they react chemically with cement hydration products in the pore walls to form a hydrophobic layer that is repellent to liquid water but permeable to water vapor. The silane is clear and colorless and does not discolor the concrete surface, nor does it affect other surface characteristics such as skid resistance.
Silane treatments are fully effective only when the material penetrates pores and capillaries. The surfaces to be treated must be essentially free of oil, dust, dirt, curing compounds or any other coatings. The best way to ensure proper cleanness is to shotblast or sandblast the surface. The other critical requirement for successful application of silanes is that the concrete surface must be dry.