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What is Coloured Concrete?

Colour Concrete Sample

Concrete is one of the most versatile construction materials available, and the range of decorative uses are only just starting to be explored. Concrete colouring enables you to use concrete in even more interesting and creative ways; letting you add a new dimension to your home, or building project.

Coloured concrete is as versatile and easy to use as conventional concrete, but it comes with an added benefit because it can be coloured in order to match existing work. It is a material that will help your home or project to melt into the surroundings, or really stand out from other properties depending on the colours that you select and the designs that you choose.

This definitive guide will give you an in depth insight into the history, benefits and uses of coloured concrete, as well as giving you some top tips for DIY coloured concrete design.

History of Coloured Concrete

Animation of concrete pyramidsAn early form of concrete was used by the ancient Egyptians in 3000 BC. Since then concrete has been used for a range of industrial uses that include building bridges, streets, and high rise buildings. During the later course of concretes history (post 1850), companies added a range of colours and stains to their concrete mixes to make their projects unique, and interesting.

In the 1900’s, castings were submerged in stains in order to colour them. This method of colouring concrete was popular between the 1920’s and 40’s for colouring luxury homes and public buildings. Also during the 1920’s pigment colour for mixing into dry concrete powder was produced by Lynn Mason Scofield. After the war, the Bromite process was developed to produce cast in place, textured and coloured concrete. At a similar time overlay cement was experimented with and in the 70’s its decorative potential was realised as it was found that it could be combined with colour and sprayed onto concrete. Since then, decorative concrete has grown in popularity and range of uses.

Just as with standard concrete, coloured concrete can be moulded into almost any shape, and it can be used to produce any texture, design or pattern; giving you freedom to create whatever you want. Coloured concrete is sure to add a dramatic design statement to your home.

How to Colour Concrete

There are two main ways to colour concrete.

  1. The first uses a dry pigment that is brushed across concrete once it has been laid.
  2. The second uses liquid or dry pigment that is mixed into the concrete before it is poured.

This is possible because the pigment particles are much smaller than cement particles so when they are added to a cement based mix the small particles cover the cement particles and colour them. In both cases iron oxide pigments that have been manufactured or that have been mined from the ground are used.

Check out this article by Chris Sullivan on understanding concrete colouring if you are looking for more information about the concrete colouring process.

The method of colouring concrete that you use depends on what design you are hoping to achieve and what surface you are working on as each method has a range of different advantages and disadvantages.

  • For example the sweep over with dry pigment is easy to do, but the resultant concrete can be easily chipped and the dye is less durable.
  • The second, combined method, is a little more difficult to do, but if your project is small, or you want to ensure the best results, then choosing it is likely the best solution.

ways to color concrete

Gray concrete floors can be gorgeous, but aren't the only color choice.

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.

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 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 the elementary school in Monument Valley, Utah. Scot Zimmerman photo

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.