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Beautiful, Durable, and Affordable: Decorative Concrete
By Aaron Chusid, CSI

Sustainable design has penetrated the construction industry to such an extent that buildings can no longer get by on LEED® points alone. Now owners expect sustainability without sacrificing appearance, performance, or affordability. Many designers are now turning to innovative decorative concrete techniques to achieve the look and environmental profile they want while controlling costs.

What is decorative concrete?
The range of decorative concrete options continues to expand, moving past simple exposed concrete to explore color, texture, shape, and more. Techniques including dyeing, staining, stamping, stenciling, polishing, and sculpting have found acceptance in a wide range of commercial, retail, institutional and residential projects, and faux techniques mimic the appearance of more expensive or labor-intensive materials, such as natural stone.

Decorative concrete extends beyond flatwork. Precast concrete elements are prefabricated off-site, reducing labor costs and construction time. Concrete countertops are popular because they can match the beauty and performance of marble or granite at lower costs and with far greater versatility; through custom forming they offer results not possible with other materials. Exotic aggregates – some designers use bolts, gears, and seashells – can be incorporated in the slab and exposed by grinding for truly unique looks. Tilt-up construction also has long incorporated decorative techniques, using form liners to create intricate textures and designs.

While the manufacture of concrete is still a major source of carbon dioxide emissions, concrete construction offers benefits that can provide a net advantage. First and foremost, it can reduce overall material use. Exposed concrete surfaces remove the need for additional covering, such as tile or paint, and the associated adhesives and coatings. This reduces total construction time, providing further cost and environmental benefit. These benefits get multiplied by concrete’s durability; a polished concrete floor that lasts 50 years will have a lower lifecycle cost than floor coverings like carpet or vinyl tile that require replacement every decade or less.

Decorative concrete has increased in popularity in the current economy because it can be used in existing construction, on existing concrete, as well as new. Extending the service life of existing facilities is another valuable sustainability benefit.

This article will examine several projects that successfully used decorative concrete to produce highly sustainable results without sacrificing appearance or budget.

Performance
The Intermediate Care Facility in Arlington, Tenn. provides transitional housing for persons with mental retardation. The facility’s two 2,500 square foot parking areas were surfaced with pervious concrete, a type of concrete with high porosity, one of the EPA’s best management practices for controlling storm runoff. Pervious concrete was used for the entire parking area, including drive lanes.

Using pervious for the parking areas eliminated the need for separate retention ponds; connecting the concrete’s underlayment to a perforated drainage pipe created a retention system with practically indefinite capacity. According to J.B. Beer, President of Jaycon Development Corporation of Memphis, Tenn., the contractors for the job, “The concrete took water as fast as we could pour it. It didn’t even move from the spot, like we were pouring it on a sponge.”

Using pervious did not substantially increase construction time. Says Beer, “Prep work took a week beforehand, but it only took two days to pour the concrete.” Concrete was placed in strips 12 feet wide and 40-60 feet long; narrow strips allowed teams to lay down plastic sheeting to cure the concrete quickly after pouring.

According to Alan Sparkman, Executive Director of the Tennessee Concrete Association, “These were some of the first commercial uses of pervious in the Mid-Tennessee area. Now, almost every day someone is pouring pervious concrete. The design community has migrated to it as the easiest, most cost-effective solution, because it helps people meet increasingly stringent stormwater regulations in space-limited urban sites.”

Estimating costs for pervious concrete can be tricky; first-costs are higher than for impervious asphalt pavement, but total costs for stormwater management can be substantially reduced. For the Arlington project, final installed cost of the pervious concrete averaged $5 per square foot. Beer estimates retention ponds for a project this size would cost $10,000-12,000 – less than half the cost of the pervious – but would consume 7,500-10,000 square feet. Since land costs can exceed $5 per square foot in urban settings, pervious saved money on land costs alone. Active filtration requirements are also reduced as pervious acts as a passive filter, reducing the amount of runoff water while improving its quality.

As pervious concrete gains wider adoption, it is also becoming more decorative. Sparkman reports an increase in use of integrally colored pervious; designers are also using innovative surface-applied aggregates, such as crushed recycled glass, to make a surface as beautiful as it is sustainable.

Appearance
One of the most common uses of decorative concrete is to emulate the visual appeal of more expensive materials, while keeping the high performance and lower cost of concrete. This was the goal at Rosedale Elementary School in Hillsboro, Ore., one of the first ten schools in the country to earn LEED Gold certification. Decorative concrete flooring helped by providing low emissions, recycled content, and locally sourced materials. Highly reflective polished concrete also improved the school’s use of natural lighting.

For the cafeteria and commons area -- a total of 7,500 square feet of flooring -- polished concrete was the natural choice. “The main reason was to have a floor that would not require sealing, waxing, stripping, and rewaxing,” explains Loren Rogers, Executive Director of Facilities Planning & Properties for the Hillsboro School District. “With a polished concrete floor, all we have to do is sweep and mop it.”

Robinson Construction of Hillsboro, General Contractor for the project, and Sustainable Flooring Solutions, the polishing contractor, achieved a terrazzo-like look at concrete prices. A pea-gravel aggregate mix was floated on top of the freshly poured concrete. Normally this would be pushed down and the surface troweled to bring the cementitious cream to the surface; for this project, the aggregate was left near the surface so it would be revealed during polishing. Leaving aggregate so close to the surface did produce voids and air pockets; these were filled in with concrete slurry. To fix the slurry in place and prepare the floor for polishing, a colloidal silica-based densifier manufactured by Lythic Solutions, Inc. was used.

According to Brad Sleeper, General Manager of Lythic Solutions, “This was a much easier process than broadcasting the aggregate, or other typical processes that involve extensive placement and compaction.” Troweling concrete to raise the cream is also a labor intensive process; eliminating that step helped control costs.

Final cost for the floor was $5.25 per square foot. Sleeper estimates doing a similar floor in terrazzo would cost at least $30 per square foot because of costly materials and labor. Rogers notes that the floor’s low maintenance costs are also an important factor. “The upfront cost for this polished concrete floor is about four times what I was told I would pay for vinyl tile. But the lifecycle cost, the amount we save on not sealing, waxing, and stripping, will pay for the polished concrete in just 4 years.”

Where to learn more
Decorative concrete is proving a cost-effective means of achieving both sustainability and appearance goals. Demonstrating its cost benefits, however, requires taking a long view to see how its impact on the total project offsets higher first-costs. Estimators and designers interested in learning more about decorative concrete should attend the Concrete Decor Show & Spring Training, March 15-18, 2011 in Nashville, Tenn. The Concrete Decor Show is the industry’s only conference and trade show focusing exclusively on decorative concrete. Emphasis is placed on hands-on training led by top decorative concrete professionals, and opportunities to network with industry experts. For more information about the show, visit www.concretedecorshow.com.


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