Concrete Priming

Concrete Priming with Damp Concrete Primer™

Smith & Co. has provided floor-surfacing [floor finishing] materials to businesses engaged in food storage, preparation or sale, as well as to their contractors, for over thirty years. Aircraft hangar floors, car showroom and repair areas, warehouse floors, machine shop and many other industrial and commercial areas, all benefit from a concrete floor that no longer absorbs dirt, oil, water that contributes to mold growth, or allows moisture evaporation that causes staining and efflorescence.
One common requirement of all these applications is that a coating stuck to concrete and stays stuck.

Smith & Co. has the molecular engineering expertise to stick just about anything to almost anything else.

Health inspectors routinely approve kitchen and food storage area floors finished with Smith & Co. products, as outlined in this application note.

Our surface preparation primer technology is normally compatible with other manufacturers’ coatings, such as epoxy or polyurethane paints. The Damp Concrete Primer sticks to both the concrete and the other manufacturer's product and then you get the finish and function you want and it stays stuck.

Any skid-resistant elastomeric coating may also be applied as a final topcoat.

Step one: Surface preparation and chemical cleaning

The most common substrate is a concrete slab, often old and irregular. There are special adhesion considerations for new concrete, and the contractor is to consult the Smith & Co. Factory for guidance.

Concrete takes time to cure to a degree of chemical stability that coatings of any sort will stick, and this depends on average annual temperature. Sufficiently cured, chemically stable concrete is at least two years old at the latitude of San Diego, CA, at least five years old at the latitude of San Francisco, Ca, or at least twenty years old at the latitude of Seattle, WA.

New concrete, however, may receive chemically bonded coatings by cleaning of the concrete such that there is exposed silica sand on the surface. That means the coating will stick and stay stuck. Such cleaning is best done by abrasive-grit blasting with a fine abrasive, to remove the film of cement covering the silica. Hydrochloric [Muriatic] acid may also be used. This comes under the heading of mechanical preparation before the first step of chemical surface preparation. Acid etching is normally done first on new concrete, between a month and a year old. This is actually a mechanical, not chemical surface preparation step, removing a cement film from the surface silica grains. Chemical bonds will be established with that silica, and then other things can stick.

Old concrete which may have absorbed food spills, grease or oil, antifreeze, brake fluid or hydraulic fluid will give adhesion problems if not chemically cleaned. Abrasive-blasting does not remove soaked-in contamination, and that can still dissolve in and come to the surface of the first coating to be applied. This is why a precleaner is necessary before the Damp Concrete Primer, the adhesion-promoting primer that bonds any topcoat to the concrete surface and keeps it stuck there.

The first chemical surface preparation step is to clean and seal the microscopic porosity of the concrete. This will flush up any oils or dirt that is in the porosity of the concrete. This is done with Smith's Permanent Concrete Sealer ™. It is applied at a coverage of about 50-200 square feet per gallon, depending on concrete porosity. Ideally one applies as much as soaks into the concrete. It is then covered with a plastic sheet to prevent water evaporation. Do not let any of this sealer dry hard on the concrete surface; it will be difficult to remove and will interfere with adhesion of subsequent coatings. It is kept covered for five hours at 77F/25C [longer in colder weather]. At the end of that time the plastic cover is removed and the concrete is rinsed with tap water while being scrubbed with a stiff bristle brush, to carry off any dirt or emulsified oil flushed up by the powerful detergent action of this Sealer.

At this point the concrete surface should show water standing, not soaking in. That proves it has been sealed against liquid water and oil absorption. It can still pass water vapor, however. This seal is based on a mineral kind of chemistry similar to the concrete itself. Acrylic-emulsion-type sealers biodegrade and weather away, and need to be repeated. Our technology is 100% Acrylic-free, and on fully cured concrete, this seal is permanent. This treatment is sufficient to seal concrete against efflorescence, the white stains commonly appearing on concrete from dissolved minerals left behind when ground-water evaporates from a brick or concrete surface. When the concrete surface is treated with Smith's Permanent Concrete Sealer, liquid water cannot reach the surface. This sealer passes water vapor only, thus the evaporation of the water takes place below the surface The dissolved minerals are thus deposited within the concrete, below the surface where they cannot be seen and actually contribute to further sealing and densification of the bulk porosity of the concrete.

The use of this product alone has been found by the VTT Institute in Finland to almost entirely prevent freeze-thaw damage in their testing program.

Step two: The Damp Concrete Primer™

The purpose of this product is to glue a coating to concrete.

Should we wish to continue with the surface treatment procedure with the goal of obtaining a painted surface or helping some slip-resistant topcoat to stick, the excess rinse water is removed, and the concrete will now appear damp, but with no standing water. Normally, this is the end of a work-day. Fans or open doors are used to provide overnight ventilation to aid in evaporation of the water.

The next day, the concrete normally appears lighter in color but may not be completely dry. The Damp Concrete Primer may now be applied, to either damp or dry concrete. Smith’s Damp Concrete Primer is a waterborne polyurethane primer, which develops a permanent silane-polyurethane chemical bond to concrete, silica sand, rock or any mineral surface recently treated with Smith's Permanent Concrete Sealer. In most cases, on clean concrete treated directly with Damp Concrete Primer, this chemical bond will be directly developed and will then stick as strongly as possible.

Damp Concrete Primer is provided as a concentrate, and one part of the concentrate is to be mixed with two parts tap water, and then applied, usually by roller, at the coverage of 400 square feet per three-quart batch. The Pot Life [Working Time] is one hour once mixed with water, and unused stale material is to be discarded. If more is needed a fresh portion must be prepared. After application, one waits about 1 to 3 hours, depending on temperature and ventilation. The opaque tan color of the material will have become a clear, brown oily film, tacky or almost tack-free. Any epoxy or polyurethane or elastomeric coating may then be applied.

If repairs are necessary at some future date, the surface may be sanded to expose bare concrete, and a new application of the Damp Concrete Primer done first. The new coating or slip-resistant finish product may then be applied.