Article No: 101
Coloring Decorative Concrete Expands Home Design Options
By: Scott Thome
Photo Courtesy of L. M. Scofield Company
Decorative concrete plays a starring role in walkways, patios, pool decks, and even driveways. What's more, colored concrete moves inside to deliver unique and durable entryways, play rooms, kitchen floors and other dramatic interiors.
The many options for coloring, finishing, stamping or using exposed aggregates multiply the opportunities to use concrete as a practical and beautiful building material. Its versatility allows builders and homeowners to personalize their properties by combining a wide array of colors, patterns and textures.
Over the next few months, this column will detail various techniques for enhancing the beauty of concrete through color and texture. We will cover ideas for new projects and options for beautifying and restoring existing concrete. We begin here with a discussion of the three methods of permanently coloring concrete: integral coloring admixtures, dry-shake color hardeners and chemically reactive stains.
Integral color is desirable for a broad range of vertical and horizontal applications. When producing integrally colored concrete, the coloring agent is added during mixing and disperses through the entire concrete slab. This means the slab retains the integrity of the color even if chipped, worn or saw-cut. Integral coloring products are supplied in dry-powdered formulations or in liquid dispersions. Recent advances in batching technology have made liquid coloring increasingly popular.
Products for integrally coloring concrete are supplied either as raw pigment or as coloring admixtures in which the pigments are finely inter-ground along with set-controlling, water-neutral admixtures that facilitate consistently even dispersion of the color within the concrete mix. True coloring admixtures, unlike raw pigments, are streak-free, UV-stable and non-fading. When adding integral coloring materials to concrete it is important to check with the manufacturer about compatibility with any other additives or admixtures in the mix design.
Integrally colored concrete can have a muted, natural appearance because the colors typically are blended into concrete that contains gray portland cement. A brighter, color can be achieved using white portland cement or very light colored sand.
For more dramatic opaque colors, use a dry-shake color hardener. Dry-shake color hardeners are hand broadcast onto the surface of freshly placed concrete and then troweled into the surface paste to form a dense crust. They deliver vibrant, uniform, opaque colors across a spectrum ranging from pastel to bold and bright. Color hardeners improve durability and increase resistance to freeze/thaw cycles and deicing, so they also are a good choice for high traffic areas.
Both integral colors and dry-shake color hardeners can be used as a base for more intricate concrete coloring and texturing techniques. Stamping, imprinting and texturing methods will be discussed in a future column.
The third method for coloring concrete is applying a chemically reactive, or acid etch, stain. These penetrating stains add color by reacting with the concrete to create rich, variegated translucent colors that are unique to each surface. Stained concrete has subtle shadings that can simulate the patina of natural stone or create artistic faux finishes. Because stains penetrate and react with the concrete, the color becomes a permanent part of the surface and will not fade, chip, crack or peel. Unlike integral and dry-shake colors, however, chemically reactive stains do not change the performance characteristics of the concrete.
Stains can be applied to fully cured concrete, either new or existing concrete surfaces. It can also be applied over the two other coloring methods described above. Different creative effects can be achieved by applying one color of stain over another color or using various applicators such as sea sponges, rags, specialty rollers or acid brushes. Staining techniques and limitations can not be summarized in a short article, so it's important to learn more from the technical literature supplied by the manufacturer.
With so many materials and methods to choose from, the decorative possibilities for homes and landscapes are limited only by one's imagination. Different concrete finishing techniques can change the look of colored concrete dramatically. For flatwork, designers might want broom, swirl, sponge float or flat hand trowel finishes. Sandblasting or grinding the surface to expose aggregate improves slip resistance and creates a natural look very different from a smooth troweled finish. Using contrasting areas with more than one color or texture adds dramatic effect for a patio or walkway.
The job of coloring concrete is not complete until the project is properly cured and sealed. Using the right materials and methods for curing and sealing will help produce durable colored concrete surfaces that maintain their color and appearance. Follow the manufacturer's recommendations for all curing materials, sealers and joint fillers. It is extremely important to follow proper curing procedures and use compounds that meet the standards of ASTM C 309 ("Liquid Membrane-Forming Compounds for Curing Concrete"). Using plastic sheeting can cause discoloration and mottling. Color-matched materials specifically designed for curing colored concrete allow it to develop its full color and strength potential. Color-matched or clear sealers offer a variety of finished appearances including matte, satin or gloss. A systems approach using coloring and finishing materials engineered to be compatible with each other is most likely to deliver a successful project.
As important as it is to use the right combination of products, there is another crucial element to success. Perhaps the most important part of the "system" is the installer. There is no substitute for training and experience.
There are many reasons to select experienced concrete contractors trained in the specialty of decorative concrete placement and finishing. Experienced concrete contractors know that moisture content affects color tones and will place concrete on well-drained, damp subgrades that are properly sloped for drainage. They know the importance of proper curing and sealing.
Having an experienced contractor is even more important where structural work is done.
Coloring concrete is a great way to add value and increase the beauty of any residential concrete project from the simplest driveway to the most elaborate pool deck and patio. Decorative concrete can provide durable, low-maintenance attractive surfaces that will last for many years - and many family activities.
For more information, call 800-800-9900 or see www.scofield.com.
Scott Thome is director of training and product services for L. M. Scofield Co., and is based in the Douglasville, Ga. headquarters outside Atlanta. In addition to supervising product testing, his responsibilities include developing curricula for the Scofield Institute and monitoring training standards. He has been involved with the International Cement Mason's Apprenticeship Training programs. His professional affiliations include the ASCC/DCC, ICRI and others, and he holds a master's degree in industrial management from the University of Wisconsin.