Preparation of Concrete Floors


The preparation of concrete surfaces is just as important as the surface preparation of steel. Regardless whether one chooses latex, alkyd, epoxy or urethane, preparation is critical to ensure long life and avoid lifting, bleeding or peeling.

New or Uncoated Concrete Floors:

Step One: Allow the concrete to sure thoroughly prior to coating. "Cured" is defined as concrete poured and aged at a temperature of 75° F. for at least 90 days.

Step Two: Concrete must be free from moisture as much as possible (concrete will generally contain 15-18% moisture). Vapor pressure, temperature, humidity differentials and hydrostatic pressure can cause a premature coating failure if not detected and corrected. If there is any doubt about the floor being dry enough, conduct a sample test by placing a rubber mat on the floor and check 24-48 hours laterr for moisture condensation on the back of the mat or a darkening of the concrete due to moisture. If condensation is found, the concrete is too damp to coat and the source of moisture must be located and corrected. If only additional drying is necessary, allow two weeks before retesting.

Step Three: Very dense, non-porous, smooth troweled or chemically treated concrete will probably require acid etching. The need for this can be determined by pouring a small amount of water onto the concrete floor. If the surface soaks up the water somewhat like a blotter, it is porous enough for coating. If water does not absorb into the concrete, etching is a must.

Acid Etching Requires the Following:

WEAR SAFETY GOGGLES AND PROTECTIVE GLOVES!!!

1. Sweep or blow down surfaces to remove loose dirt.
2. Wet surface with clean water.
3. Etch with a 10% solution of Muratic Acid at a rate of 1 gallon of acid per 75 sq.ft..
4. Scrub with a stiff brush.
5. Allow sufficient time for scrubbing until bubbling stops.
6. If no bubbling occurs, surface is contaminated with oil or grease. Remove the contaminate then continue.
7. Flush surface 2 or 3 times with water to totally remove acid solution.
8. Surface should have a texture similar to medium grit sandpaper.
9. Allow surface to dry and remove dust before painting. Retest for moisture.
10. Finish with preferred coating. Air, material and surface temperature must be 60° F. 24 hours prior to, during and 24 hours after coating application.

Other acceptable methods is lieu of acid etching are: Brush Blasting, Sweep Blasting or Power Tool Cleaning.

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