Gray concrete floors can be gorgeous, but aren’t the only color choice.
A pearly gray polished concrete floor can be a thing of beauty. But the days of gray-only for concrete floors are long gone. Now, the color choices for concrete are unlimited as dreams and imagination.
Particularly when used with concrete polishing, coloring can provide translucent, almost gem-like effects.
Color offers almost gemlike effects when used with concrete polishing.
Here are the 6 most common ways to color horizontal concrete.
1. Integral coloring
Colorant added to concrete during mixing produces uniform color throughout the slab.
The colorant may be liquid or powder. Integral color is for new installations only, and usually only for large monochrome areas, since the main application device is a ready mix truck. Integral colors are expensive because you are coloring the entire depth of the slab.
2. Shake-on colors
Shake-on color consists of finely-ground pigments and dry cement that is “broadcast” onto freshly placed concrete. The powder gets worked into the concrete during bullfloating.
Bleed water from the plastic concrete wets the cement powder, causing it and the pigments to bond to the exposed surface. Because the pigments are concentrated in the top layer, grinding and polishing will remove the color. Since shake-on colors rely on water from freshly placed concrete, they are only suitable for use on freshly placed concrete.
3. Acid Stains
Acid stains are formulas of acid, metallic salts and water. The acid chemically reacts with minerals in the concrete, creating a unique, mottled color effect that’s as durable as the wear zone of the concrete it’s applied to. Acid stains are hazardous materials and require all the safety precautions common to acidic products.
Concrete floors that have been acid stained must be neutralized and rinsed thoroughly to remove any excess acid. You must be careful when handling acid stains, also, because spills, sloshes and drips instantly create permanent “features” in the floor. Acid stains can be used for retrofits or new installations.
4. Acetone dyes
The benefits of fast-drying solvent-based dyes are often overshadowed by the risks inherent with using highly flammable reduction solvents. Acetone – one of the most common reduction solvents, has a flash point of 4 degrees F and an odor and toxicity that makes it impractical to use in most occupied spaces. The color usually is applied after the floor has been polished with a 400-grit resin.
Though solvent-based dyes can impart vivid colors, they aren’t UV-stable. Sunlight, through a window or skylight can fade the colors. Most require a topical protective treatment to lock the color in. Respirators and explosion-proof ventilation are required when installing solvent based dyes on new or existing concrete floors.
5. Water-based dyes
Water-based stains and dyes have several advantages. They are odorless, safe and easy to apply, and dry quickly. Different colors can be easily mixed and matched, creating striking patterns and effects in areas large or small. Combined with hardening, densifying and polishing, water-based stains can create a translucent, gemlike effect. However, water-based stains must be used with protective coatings to lock in the color. Like acetone dyes, they are not UV-stable and will fade in direct sunlight. Water-based dyes can be used for new installations or retrofits.
Water-based colors were used to create a Navajo Wedding Basket design in the entryway of this elementary school in Monument Valley, Utah. Scot Zimmerman photo
Water-based colors are easily applied with pump-up or airless sprayer, followed by spreading with a microfiber pad. The color usually goes on before the floor has been hardened and densified.
6. Color hardener/densifiers
Color hardener/densifiers are a recent innovation in which fine pigments suspended in water are blended by the applicator with a lithium-silicate hardener/densifier. This lets you harden/densify and color in one step. Apply color hardener/densifiers to concrete floors ground no finer than with a 200-grit resin pad.
UV-stable color hardener/densifiers outside an elementary school in Monument Valley, Utah. Scot Zimmerman photo
The pigments in these products are similar to shake-on colors in that they are surface treatments, so polishing after application removes the color. Also like shake-on colors, most are UV stable and suitable for exterior application. While a protective treatment to “lock in” the color isn’t needed, strictly speaking, protective treatments are always a good idea for horizontal concrete, inside or out.
Which is right for your project?
The answer is… it depends. If it’s a new installation, any of these products will work. If it’s a refit or restoration, you’re limited to acid-stains, water-based dyes, acetone dyes or colored hardener/densifiers.
If it’s polished concrete and uniform color you’re after, acetone or water-based dyes are your best bet. The difference? For safety and environmental concerns, choose water-based dyes. For slightly more vivid colors, acetone may be the product you want.
For the mottled, antique look without polishing, consider acid-staining.
Shake-ons are best for small, simple jobs, when there’s not going to be any grinding. Since shake-ons are surface treatments, grinding will take the color off. Consider integral color for large areas where you want uniform color.You can grind these installations aggressively if, for example, you want to expose aggregate.
And though your standard gray concrete isn’t the only color option any more — it can still look pretty good.
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