The porosity of the concrete can be a problem when it comes to painting your concrete floor; not only does paint soak in and create a blotchy job, but moisture can seep through the pores and cause paint failure. Moreover, if the concrete pad is on a poorly drained area, seepage can create white efflorescence streaks whether you paint the pad or not.
Concrete sealers are designed to prevent these problems, and a sealer that contains polyvinyl acetate -- PVA -- can be especially effective. A PVA sealer can also provide an adhesive undercoat for new concrete. You apply it with a paintbrush after thoroughly cleaning the concrete.
A Sealer and Adhesive
PVA is the component of white carpenter's glue that make the glue sticky, and it's the adhesive ingredient in drywall primer. In fact, it's even an ingredient in acrylic latex paint. Through a reaction involving ethanol and heat, polyvinyl acetate can be converted to polyvinyl alcohol, which is also identified as PVA and is the main component of some gel glues.
As far as applying your concrete sealer, though, it doesn't matter whether the PVA in your concrete sealer is polyvinyl acetate or polyvinyl alcohol -- both are just as sticky.
Applying PVA Concrete Sealer
The surface to which you apply PVA sealer must be clean and dry, and it must be free of dust and chipping or flaking concrete. This sealer remains white, so it's best used as an undercoat for paint, mortar or some type of floor covering -- using it isn't an option if you want to stain your concrete or leave it natural.
Things You'll Need
Rotary floor scraper
Mortar or hydraulic cement
Remove glue, mastic and old paint from the floor by using a chemical stripper. Spread the stripper; allow it to work for the recommended time, and scrape it up with a floor scraper. You may have to use a rotary floor scraping tool to remove stubborn material.
Patch any holes or cracks, using mortar or hydraulic cement. Spread and smooth the patching compound with a trowel. Then allow it to dry thoroughly, which may take several days, depending on the location and condition of the pad.
Wash the floor with a solution of 1/2 cup trisodium phosphate per gallon of water to remove any grease or oil that could interfere with adhesion of the sealer. TSP lightly etches the concrete surface and improves adhesion.
Let the floor dry, and then give it a final vacuuming to make sure there's no lingering dust.
Use the sealer as a primer by diluting the sealer as required by the instructions on the container. Depending on the product, you may have to dilute it with as much as 4 parts water. If you plan to use the sealer as a key coat or an adhesive, less dilution is required -- perhaps as little as 2 parts sealer to 1 part water.
A key coat is one you apply before laying a topcoat of new mortar or thinset.
Spread the sealer with a paintbrush, working it deeply into all the corners as well as into any cracks and crevices that remain after patching. Let the PVA sealer dry when you use it as a primer before painting. If you're using it as a key coat, recoat it while it's still tacky.