Concrete questions and issues continue to dominate my time. Not that I don’t enjoy receiving emails and phone calls from you, but everyday up and down the east coast I get questions about concrete.
The flooring industry is the only trade that is responsible for any all issues in its trade. If the drywall tape cracks or comes loose, they don’t call in a painter to fix it. But, if the concrete cracks and shows through the flooring, they call the flooring professional.
General contractors keep pushing flooring contractors into doing more and more subfloor prep and expect little to no charge for it. I had a flooring contractor call the other day and said that the concrete cracking and splitting. The General Contractor wants to know what the flooring manufacturer can do about this. This is not a flooring contractors issue; this is a concrete structural issue.
In commercial construction, the basic question is what concrete sealer, curing compound, or adhesive remover does the flooring manufacturer recommend? Let’s address this one issue at a time.
Concrete Sealers;
The RFCI (Resilient Floor Covering Institute) which represents the entire resilient flooring industry does not endorse the use of concrete sealers. They state; “cured concrete slabs on all grades, coatings, sealers, curing compounds present require non-chemical removal.” Adhesive and floor patch manufacturers also do not endorse the use of concrete sealers. Even if a loose lay floor is to be installed over concrete, the concrete sealer must be removed. Why? Because I know you want to do proper moisture testing. For proper moisture testing, you have to get down to the actual concrete. Concrete sealers keep the slab sealed up and do not allow proper drying of the concrete slab.

Curing Compounds
Curing compounds are agents applied to concrete slabs to retard the escape of water during the initial curing process. Curing compounds leave a film that can interfere with the adhesion of other materials to the treated surface. Their use should be avoided on surfaces that will later be covered with resilient floor coverings. Such compounds can remain on the surface of a slab and continue to retard the escape of water during the drying process. They may break down after the floor covering has been installed and the building is in use. This can occur on suspended slabs as well as those in contact with the ground.
The elimination of excessive free water from the concrete is essential for the formation of a bond between the adhesives, the flooring materials and the concrete. In the presence of excessive free water, water-based adhesives will not set up, and solvent-based adhesives will not adhere. In the case of adhesives already bonded to concrete, the adhesive will be displaced by water if the availability of water is sustained.

Adhesive Removers
I don’t care what the adhesive remover supplier says, stay away from jobs where these were used. These products can migrate down into the slab and resurface at any time and do again what they are intended for, remove the newly applied adhesive. I have received calls over the years where these products were used and a few years later there is adhesive oozing up through the tile joints. The adhesive remover migrated down into concrete slab and now has re-surfaced and is breaking down the new adhesive. Adhesive removal products contain solvents that leave a residue within the subfloor. This residue can negatively affect the new adhesive and bleed through the new floor covering. These products may be biodegradable, but they do contain solvents.

I pulled this off the label of one of these products;
•    Wear protective clothing, goggles, acid resistant gloves, and a NIOSH approved air-purifying respirator with an organic vapor cartridge
•    MAY CAUSE PERMANENT SKIN DAMAGE AND SEVERE RESPIRATORY SYSTEM IRRITATION.

Sealers, curing compounds, and adhesive removers are also known as bond breakers. They impede the bonding of adhesives and patches to the actual concrete substrate.

There is an ASTM Specification for Concrete to Receive Resilient Flooring, ASTM F710. It states the concrete slab must be;

Free of dust, solvent, paint, wax, oil, grease, residual adhesive, adhesive removers; curing, sealing, hardening, or parting compounds; alkaline salts, excessive carbonation or laitance, mold, mildew, and other foreign materials that might prevent adhesive bond.

So, how do we get around this? Well, in most cases sealers and curing compounds are going to be used. The first thing that should touch that concrete slab from a flooring installers end should be a floor machine with grinding stones or with a sanding disc. Open the slab up by hitting it with the floor machine.
With Adhesives Removers, you can rinse, sand and grind, but if that product has migrated down into the slab, there is no cure.
So now if a contractor asks you about what sealer, curing compound, or adhesive remover to use, you have the answer at you finger tips. Refer them to the Specification ASTM F710.

Thanks to Tim Mcadoo from JJ Haines.