We recently were called upon to refinish a section of flooring at a facility in Erlanger, KY. Although most refinishing projects are on the simple side of this profession, this one had a few obstacles. The coating on the floor was a brown urethane put down many years ago. Although it held up fairly well, it was time for a recoat.
To start the surface preparation, we had to address a few specific areas with the diamond grinder. The first area was at a cross section of control joints. The previous installer had poured material out into a puddle and failed to spread it evenly. To achieve a smooth profile, we ground down the area to remove the hardened lump.
That wasn't all the diamond grinding that had to be done on this job. The owner of the facility had a section of the slab removed and then replaced with fresh concrete. When the new section was poured, the installer failed to level the edges with the rest of the floor. That resulted in a trip hazard around most of the newly poured slab. This had to be ground down.
The new slab also had to be prepared with the diamond grinder to give the proper surface profile to ensure proper material adhesion. Proper adhesion can not be accomplished by sanding the concrete. Bare concrete needs to be prepared for coating in one of these ways:
- Mechanical preparation with a shotblast machine
- Mechanical preparation with a diamond grinder
- Chemical preparation with an acid solution (should be a last resort)
After using the diamond grinder to prepare the bare concrete, we removed the heavy dust with a vacuum. We then took KEY #635 MVT and mixed it with Cab-O-Sil (fumed silica) to make a stiff material to patch the saw cuts around the new slab with. We then primed the surface with KEY #635 MVT and let cure overnight.
The second day, we continued to prepare the rest of the floor. When there is already an epoxy or urethane coating on the floor, it can be prepared by sand abrading. When sanding the floor, it is pertinent to remove all of the gloss from the existing coating. This will ensure the proper adhesion of the first coat of new material.
After abrading the entire floor with 36 grit sand paper, we removed the heavy dust by vacuuming the entire floor, using the hose to vacuum out corners and edges. After the heavy dust was removed, we proceeded to tack the floor with plain water to remove any fine dust remaining on the surface. We then mixed some Cab-O-Sil with KEY #520 100% Solids Epoxy to patch the floor with.
It was finally time to apply the base coat. We installed a coat of KEY #520 Dark Gray 100% Solids Epoxy Coating. By installing an epoxy base coat at around 10 mils, we can hide some of the imperfections in the floor that have occurred over many years of abuse. It also helps to guarantee a strong bond between the old coating and the new urethane topcoat being installed next.
After letting the base coat cure overnight, it was now time to install the top coat. For a top coat, we used KEY #467 Dark Gray Moisture Cured Urethane. This material has excellent abrasion and chemical resistance. It can be installed with fine anti-slip mixed in, but it was not called for on this project. Before the top coat was applied, we screen abraded the base coat so the two coats would bond not only chemically, but mechanically.