Concrete sealers come in a wide variety of kinds, each suited to a specific and particular type of project. For a concrete highway, the best choice would be a silane/siloxane concrete sealer. Silane/siloxane concrete sealers, like the Department of Transportation Approved Siloxa-Tek 8500, contain particles of silane and particles of siloxane. The silane particles will penetrate slightly past the surface of the concrete while the siloxane particles will pool on the surface of the concrete to be spread out over the course of the application process. Together, the two types of particles suspeneded in the Siloxa-Tek's water-based solution will work in concrete to create a hydrophobic barrier that locks out excessive water, as well as other minerals (like salts from DOT trucks in the winter), from entering the concrete where they can wreak havoc, resulting in potentially costly repairs.