If you have a damp concrete floor, there will be a perfectly good reason for it. Normally, signs of dampness result from impermeable materials such as lino being placed on the floor and trapping condensation. A damp floor will always have a very simple solution. Concrete can trap moisture in itself, sending it sideways under the floor to the walls - creating symptoms of 'rising damp'. Allowing a small separation between the edge of the concrete and the wall will stop moisture reaching the wall and dry out the join. Damp proofing floors is NOT recommended under any circumstances. If there is a problem, it needs to be professionally diagnosed, and a suitable solution provided.