ReCrete Materials, Inc. created “ToroStone” from pieces of recycled runway at the former El Toro Marine Corps Air Station.

The use of recycled materials is not new in the concrete industry, but in the past some contractors have downplayed its inclusion because of (mistakenly) perceived lower value. That time is gone, says Jason Buesing, president of ReCrete Materials, Inc. His company, along with its affiliate, Recycled Materials Company, is setting new standards for use of recycled materials in concrete.

Recycled Materials Company’s role in the movement started in 1987, and accelerated in 1999 when it received the contract for deconstruction of the former Stapleton Airport in Denver. (At the time, the company joined with the Colorado School of Mines to create concrete mix designs that included recycled materials.) Since starting the deconstruction of the airport, says Buesing, the company has sold 6.5 million tons of recycled concrete and asphalt — and still operates an urban recycling center at the site.

In 2006, Recycled Materials Company decided the demand for more highly-engineered recycled materials was growing fast enough that it needed to start up a separate venture to handle the products, and ReCrete Materials, Inc. was formed. One of its first big jobs: Enterprise Park at Stapleton, developed by Etkin Johnson Group and home to three tilt-up buildings with 441,000 square feet of office and industrial space. (CAL Construction Company is providing tilt-up services on the project.) Construction began in March 2008.

According to Buesing, concrete foundations for the structures will use approximately 620 tons of recycled aggregate and 115 tons of fly ash; concrete for the tilt-up panels will use approximately 1,570 tons of recycled concrete aggregate.

Tilt-up buildings at Enterprise Park, located at the site of the former Stapleton Airport, contain a large amount of recycled concrete aggregate in both foundations and tilt-up components. Images courtesy of ReCrete Materials, Inc.

Much of the material is roughly 10 percent to 15 percent lighter in weight by volume, so the project requires less material overall. Plus, using materials recycled from the nearby decommissioned airport means reduced costs for fuel and truck miles, and fewer emissions from transport.

The success that the two companies have experienced at Stapleton did not go unnoticed. In April 2005, the City of Irvine, Calif., selected Recycled Materials Company to perform recycling and material removal operations at the former El Toro Marine Corps Air Station, handling a total of approximately 3.5 million tons of concrete and asphalt. While the project was recently put on hold, plans are still in place to turn El Toro into the Orange County Great Park — one of the largest metropolitan parks in the U.S., according to the Great Park Conservancy.

Mark Wachal, co-founder and partner in Recycled Materials Company, says the Great Park opportunity is a huge step forward in the recycled concrete movement. “Our program encompasses all things we have learned at Stapleton,” Wachal says, maximizing every resource available at the site and creating almost 10 different recycled products.

The resulting recycled concrete aggregate products include an aggregate base course (for use under pavement); a bedding product for underground utilities; landscaping material called ToroStone (essentially three by four-foot pieces of runway) that can be used for water revetment, stream protection, park benches and water features; and — of course — fine and coarse aggregate components for ready mixed concrete.

Concrete puts a beautiful face on recycled materials and ICFs

Southface Eco Office, image courtesy of Georgia Concrete and Products Association.

In Atlanta, a large staff at Southface Energy Institute is working to educate people about sustainable homes, workplaces and communities…so what better place to put green building practices into action? The organization has two buildings: One a residential-style structure, the other a new commercial building, the Eco Office. Both function to house staff and educational tools, and as demonstration projects for consumers and the construction community.

Both structures are built with insulating concrete forms (ICFs). “We think concrete is a great building material because it’s very durable, termites won’t eat it, it’s easier to manage moisture issues with it—and the ICF system makes it a great energy performer,” says Southface executive director Dennis Creech.

For the Eco Office, Southface used ICFs from PolySteel, creating a building that has a life beyond being a “show home,” according to Will Oliver, president of Oliver Building Solutions and supplier of the ICFs. The energy efficiency of the ICF system allowed Southface to reduce their HVAC tonnage by eight tons on the 10,000-square-foot structure.

The savings will be tracked and documented, says Creech: “With support from PolySteel, we’ve fully instrumented this building. We’ll be monitoring the moisture, mechanical and plumbing, and we’ve got thermocouples on the outside and inside of walls to measure flow of temperature.” Data will be posted online for observers.

Concrete for the structure incorporated supplementary cementitious materials: in the ICFs, cement replacements were at 15 percent fly ash and 20 percent slag cement; in footings and slab on grade, that replacement level was pushed to substitute 20 percent with each material. “Being a green building demonstration project, we wanted to use as high a replacement amount as possible,” says Frank Burdette, Southface’s project manager with commercial green building services.

And concrete is sprinkled throughout the organization’s campus: pervious concrete is used for sidewalks, plazas and driveways; concrete countertops adorn kitchens and public restroom facilities; exposed, colored concrete flooring in the main entryway serves to connect the office building with the 6,500-square-foot residential structure; and recycled concrete aggregate was used in landscaping.