Wait 60 days before attempting to remove any white stains on new concrete. This will allow the moisture in the concrete to rise to the surface and evaporate, leaving behind the salts that cause the whitish discoloration. Attempting to clean the concrete before all the salts have risen to the surface may lead to a deposit of additional white residue after the first cleaning.
The white residue on the surface of new concrete can be removed only with an acidic cleaner. Given enough time, acid rain can clean the majority of white concrete stains, but many homeowners do not wish to wait to remove the problem. Purchase an acidic efflorescence stain remover, available at hardware stores and home centers.
Lightly mist the concrete with water and then spray on efflorescence cleaner. Choose a moderately warm day, but if possible wait until the concrete is in the shade before spraying. Use a nylon-bristle brush to scrub the concrete once it has been sprayed with the cleaner. Wear gloves, eye protection and heavy clothing while scrubbing. Rinse off the cleaner with water after you have thoroughly scrubbed the entire area. Allow the concrete to dry.
Apply a concrete sealer or concrete paint to the clean and dry concrete after the manufacturer's specifications. The sealer or paint will help the concrete last longer and should prevent any additional white residue from rising to the surface of the concrete.