Beginning in 1980, the Kansas Department of Transportation (KsDOT) used alkyl-alkoxy silane to waterproof 57 newly placed concrete decks or overlays on old or new bridges. In 1985, research teams inspected 14 of the treated bridge decks to see if the silane kept salt out of the concrete.
HIGH CHLORIDE CONTENTS FOUND AFTER ONLY ONE WINTER
One new deck, constructed and treated with silane in 1984, had salt contents up to 8 pounds of chloride per cubic yard of concrete after one winter. One pound of chloride ion per cubic yard of concrete is considered to be enough to start corrosion of bare steel.
HIGH CHLORIDE CONTENTS FOUND IN LOW-SALT-USAGE REGIONS
The least amount of deicing salt is used in the southeast region of Kansas. Even so, the chlorides averaged 2.12 and 5.96 pounds per cubic yard of concrete in the top 3/4 inch of two concrete overlays sampled. The silane did not keep salt out of the concrete even in Kansas' mildest climate with low deicing salt usage. Other bridges in other areas showed similar high chloride ion contents in the concrete bridge decks treated with silane.
After evaluating performance of alkyl-alkoxy silane on decks in Kansas, KsDOT recommended that it no longer be used.