Pervious concrete is often described as looking like a gray Rice Krispies treat. Now that color is becoming more common in the pervious market, maybe we can drop the “gray.”
With the sustainable paving technology spreading across the country, designers are finding new and innovative ways to incorporate it into their projects. This includes options of color and texture. While pervious concrete only accounts for a fraction of a percent of the larger ready-mixed concrete market, the colored pervious market is only a smaller percent of that segment. However, as this elusive goddess comes within reach, the size and share of the decorative pervious concrete market should grow.
Often the landscape architect specifies pervious. Landscape architects are masters of manipulating color and texture on their projects. Pervious concrete offers options for both of these while maintaining its positive benefits for stormwater management.
As with plain concrete, the full range of color possibilities is available to pervious concrete, especially with liquid color dispensing systems. This provides flexibility to the designer to choose any color that might enhance the project's environment. Likewise, contractors are now stamping pervious concrete to give the surface a more dramatic appearance.
The producer's role
From the concrete producer's perspective, little needs to change in the mixture proportions of a pervious concrete to allow it to be colored. As with any pervious concrete, it should be proportioned to maximize water. Maximizing water in uncolored pervious concrete will enhance workability, consistency, and durability. In colored pervious concrete, maximizing water will further help reduce variability in surface color.
To maximize water in the mix, the producer should proportion the mix by the guidelines in ACI522R-10 or by any other reputable mix design system for pervious concrete. Also, using an ASTM C 494 Type D admixture like V-MAR VSC500 will enable the highest possible water/cement ratio.
When batching colored pervious concrete, the same procedures should be followed as for batching normal pervious. This includes carefully controlling and monitoring aggregate moisture, introducing about 90% of the batch water on the head of the load, discharging slowly into the ready-mix truck, and providing a little extra mixing time.
Envirocrete Inc., based in Sacramento, Calif., is an experienced contractor for colored pervious concrete. Since 2006, this producer has placed thousands of square feet of colored pervious concrete. “Fifty percent of our projects are produced in color,” says company president Guy Collignon.
Colored pervious concrete is usually seen in areas without much vehicle traffic, such as parks, zoos, nature trails, streetscapes, and pedestrian malls. However, Envirocrete has placed two parking lots with black pervious concrete.
While some contractors are afraid to do any colored work, Envirocrete prefers it. “Any time you add color to pervious, it's going to be better,” says Collignon, discussing his customers' satisfaction with their pervious concrete projects. He also reports better color retention over time with pervious compared to plain concrete, without having to increase the normal color dosage rate.