I have a client who has what appears to be white crystals appearing on his concrete basement floor. It has been wet in the past, so I am wondering if something is crystallizing after evaporation of the moisture in the basement floor. Do you have any idea what the material might be and how to get rid of it?
The tan and white deposits are called efflorescence. They are from salts and lime in the concrete. Whenever water moves through concrete, mortar or block, the salts move with the water. The water evaporates and leaves behind the efflorescence deposits.
You can remove the efflorescence with a mild acid. You need to remove the deposits for any type of coating to stick. I suggest using UGL Brand ETCH. It’s a powder that you mix with water. ETCH is available at most hardware stores. You can also remove most of the surface deposits with a wire brush – but you must treat with an acid for real cleaning.