Colored concrete has been a decorative design choice for architects and concrete installers since the early 1950’s and continues to grow in popularity today, leading all other market segments of concrete construction. In addition to residential driveways and commercial building entrances, contractors now use colored concrete for patios, swimming pools, basement floors, walkways, garden walls and flowerbed edging, as well as pavers, masonry blocks and stucco. The ideas are limited to one’s imagination.
To become an expert in producing beautifully colored decorative concrete projects requires an understanding of:
- color theory
- different processes for coloring concrete
- use of each process
- factors affecting the final color
1. Integrally Colored Concrete
Integrally colored concrete uses natural or synthetically manufactured iron oxide pigments. Available in powder, liquid and granular form, the smaller iron oxide pigment particles cover the larger cement particles when added to any cement-based mix to create color that is uniform throughout the concrete. Iron oxide comes in four colors: black, red, brown and yellow. The blending together of these basic colors produces a variety of other colors. Cobalt and chromium oxide are used for blue and green pigments.
Integrally colored concrete will not fade over time, but will change due to efflorescence, pollution, dirt and traffic. Typically a good cleaning and sealing will bring back the original color.
Natural Versus Synthetic Pigment
- Chemically the same — iron oxides in both are lightfast and UV stable
- Natural pigments are less expensive
- Limited color range for natural pigments versus more color options with synthetic
- Natural pigments produce warmer colors — synthetic pigments produce vibrant colors
- Natural pigments do not have the tinting strength of synthetics
Water to Cement Ratio
- Critical factor in producing consistent color
- Added water permanently changes concrete, typically lightening the final color
- Use a surface evaporative control agent instead of water to slow the hydration of concrete in hot windy conditions, or if the concrete surface is drying out
Gray Cement Versus White Cement
- Use color samples instead of color charts to determine desired color
- The gray color of cement mixes with the pigment to make the final concrete color, usually darker earth-tone shades
- Not all shades of gray concrete are consistent — maintaining batch-to-batch consistency by using gray cement from the same lot
- Proper curing is required to produce consistent color — use a matching colored curing compound or color wax that are non-yellowing, blush resistant or for decorative concrete
- To obtain a truer or lighter color, use white cement, a more expensive option
How to Save Concrete with Inconsistent Color
- Hide color with one or two coats of a tinted sealer
- Higher solids water-based sealers are more opaque
- Lower solids solvent-based sealers are higher in gloss level
- Change slightly varying color with a translucent water-based penetrating stain or a topical acrylic stain
- Fix inconsistent color with a polymer modified thin section topping, available in any color that can be finished to look like concrete
2. Acid Stained Concrete
Acid-based chemical stains permeate concrete to give it a rich, luxurious color with luminous, translucent tones that can’t be achieved with any other process. Depending on the surface they are applied to and the application techniques used, acid stained concrete can look like polished marble, tanned leather, natural stone or stained wood.
Concrete stains are semi-transparent, soaking into existing concrete to enhance what’s already there, and will not hide cracks, blemishes, texture issues or an underlying color. Proper surface preparation is critical for full color penetration, including the cleaning of dirt, grease, glues, coatings, curing membranes and sealers.
Acid-Based Chemical Stains Versus Water-Based Acrylics
- Acid stains react chemically with the concrete, etching the surface, a permanent color won’t fade, chip off or peel away
- Acid stains are ideal for producing earthy tones like tans, browns, terra cottas and soft blue-greens
- Water-based acrylic stains also penetrate the concrete to produce permanent color and are available in dozens of standard colors, offering an alternative to earth tones
- Both can be applied to new or old and plain or integrally-colored concrete
- Both are ideal for revitalizing dull, lackluster surfaces
- Both have excellent UV stability and wear resistance
- Both can be used on interior or exterior concrete
3. Concrete Dyes
Concrete dyes do not react chemically with concrete, so the color that you see applied is the finished color. Tinting strength and penetration will vary depending on the characteristics of the concrete. Because concrete dyes are available in almost any color, they can expand a project’s color palette, creating subtle effects not possible with other coloring agents, or fix problems with acid stain applications.
Dyes can be used with acid stains to provide accent colors, color layering and depth. Used alone, they can be layered for an artistic variegated effect. Dyes are either water-based or solvent-based, in solution, powder or liquid concentrates.
- come in mix-yourself and ready-mixed basic colors
- can be diluted for less saturated color
- create a pastel, watercolor look, ideal for color layering
- create faux stone or weathered stone effects
- evaporate slowly and will leave rings if allowed to pool
- come in primary and secondary colors, mixed to form other colors
- can be diluted for less saturated color
- produce bold colors when used at full strength
- create dramatic looks
- evaporate rapidly and require a deft touch
- can be hazardous to work with; prevent vapors from igniting
Concrete dyes behave differently than stains because they don’t bond to concrete. They can be applied like stains using airless sprayers, brushes, rollers and sponges, but an understanding of color theory is required to mix colors successfully. Dyes are not as resistant to ultraviolet light as acid stains and are more like to wash away, so they require a UV sealer when used indoors or outdoors.
Here at Runyon Surface Prep we carry a wide range of concrete color products from Ameripolish, Prosoco, Convergent, Dayton Superior and Scofield. For any questions you have on integral color, stains, dyes, applying color, etc. please feel free to contact us.