"Seal the concrete with a silicate based sealer, such as the products from endur-o-seal. These are sprayed on to the cement with a garden sprayer, soak into the cement and fill the pores with a solution that gels and then hardens over a period of several days."
I used Drylok in my basement garage and it worked fantastic. Just make sure you have one of those drill mounted mixing thingies. Stuff was pretty thick as I recall