Stamped and Colored Concrete

DEAR TIM: Our builder is trying to convince us to use colored stamped concrete for our front walk. I'm worried that the textured finish will not last. Is stamped concrete as good as regular concrete? What can be done to insure a long lasting job? Is it possible to colorize regular concrete after it is poured? D. A.

DEAR D. A.: I think I can significantly reduce your anxiety level about pattern stamped concrete. It is a fantastic technique to improve the visual characteristics of otherwise bland concrete. Concrete in and of itself is a premier building material. Adding color and texture to it simply enhances its appeal to me.

Pattern stamping is not really new. It has been done for years in one form or another. As a child, I would often see the name stamp of the concrete contractor who installed the sidewalks in my neighborhood. Steep concrete roadways were often stamped with horizontal lines to increase traction. The pattern stamped residential concrete your builder is using has been around for almost four decades.

The stamping processes available today can create over 90 different patterns. They include a wood boardwalk look, slate, cobblestone, brick, flagstone, ceramic tile, etc. When the installer blends different colors with the wet concrete the effect is dramatic. If you have visited theme parks or other attractions there is a good chance you have walked across stamped concrete thinking it was a natural stone product! Contractors who use newer molds and pattern stamps can create unbelievable results.

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There is no reason why your front walk shouldn't last for many years. As long as your contractor follows all of the known industry standards for pouring concrete, your stamped walk should outlast you. I would suggest that you install 1/2 inch steel reinforcing bars on 24 inch centers in both directions of your walkway. Be sure this steel ends up in the middle of the 4 inch thick sidewalk. In addition, make sure that the concrete is ordered with a minimum compressive strength of 4,000 pounds per square inch. If you choose to install stamped concrete in your driveway, insist on a minimum thickness of 6 inches. Be sure the concrete is cured after it is installed.

Concrete shrinks when it dries. This shrinkage usually amounts to 1/16 inch for every ten feet you pour. This shrinkage produces internal stresses within the concrete. To prevent random cracking you must install control joints. These joints are saw cut lines often created the day after the pour. They should be cut to a minimum depth of one-fourth the thickness of the slab.

It is possible to colorize an existing slab. There are various chemical concrete stains that can be used. Often these contain muriatic acid and metallic salt compounds. The acid etches the concrete allowing the stain to penetrate. Because of differences in the texture and makeup of the existing concrete, it can be difficult to maintain uniform coloration. If you choose to stain existing concrete, you must pay close attention to manufacturer's instructions. Rich colors are possible, however, you will need to practice to achieve them on a consistent basis.