Concrete Recycling

Concrete recycling has expanded dramatically in the United States in the past 10 years, though its use is still much less than in Europe and Japan where there are shortages of both virgin aggregate and landfill space. Only about 10 percent of concrete is recycled here, compared to 90 percent in the Netherlands and 40 to 50 percent in the United Kingdom and Japan, Chini says. Before concrete recycling becomes more prevalent, he says it will need to become economically feasible. “We have to reach a point that disposal of concrete is not as cheap as it is right now,” he says. “This is a place where governments can play a role by making landfill usage more expensive and by providing additional incentives to people who recycle.”

Some increased recycling is already happening due to normal economic forces. Landfill tipping fees in some areas are quite high. A distant landfill also favors recycling when the high cost of diesel fuel, trucks and drivers to haul debris is considered. To get around these expenses, some general contractors stockpile their leftover concrete and are visited by a portable crusher owned by a concrete recycler once a year. Other contractors have a portable crusher visit a specific site for a few days to handle small demolition jobs.

Increased demand for crushed aggregate in areas like the Northeast where much construction is underway is another factor promoting recycling. “Some of our customers crush everyday and cannot produce enough material to keep up with demand,” Hillis says.

Brossart Materials and Recycling, a subsidiary of Spartan Construction, recycles concrete for that company and about 50 other contractors. These contractors bring mostly demolition materials to Brossart’s yard in Burlington, Ky., and pay $10 to $20 per load depending on the truck size for the privilege, a fair price because landfills are far away. It also accepts washout and leftover concrete from ready--mix companies. Brossart only crushes at its yard twice a year and sells the resulting rock, which includes 1 1/2--, 2-- and 4--in. sizes, for commercial work and sub--base at $5.50 to $6 per ton.

Contractors and government agencies in north and central Florida save a $32 per ton landfill tipping fee by taking their old concrete to Chip’s Dozer Service, which accepts these materials for free. The company crushes 60,000 to 80,000 tons of concrete per month. Much of the resulting aggregate is purchased by those same government agencies for use in sub--base, underground bedding and new concrete.

Gettin into recycling

Although the entry level price for a portable crushing plant is $200,000, the payback period for this investment is short. Crushers can be used with any material, including natural limestone, and the plants have a high resale value.

Crushing system operators are required to comply with the federal Clean Air Act. “It’s time--consuming but it’s not difficult to meet the standards,” Brossart says. Each location must be qualified separately. After setting up, an inspector comes and does an analysis while the crusher is operating and gives approval that is good for one year.

Concrete producer Rinker Materials is currently studying whether to use recycled aggregate in its ready--mix and anticipates knowing whether the company will enter this market in about a year. The performance, handling costs and transportation costs of recycled aggregate compared to virgin aggregate are the issues of concern.

However, Rinker is already active in recycling concrete in other ways. For several years it recycled unused concrete returned from jobsites into tetrahedrons used to create artificial reefs. These 3-- to 6--ft. triangular units were purchased by government agencies for placement underwater off the Florida coast. Marine animals find the crevices the randomly placed tetrahedrons create to be appropriate habitats. Reduced market interest led to the end of their production by Rinker.

“We do recycle concrete now by making large mac blocks,” Don Beers of Rinker says. “This is a solid chunk of concrete that is 6 ft. long and 3-- by 3--ft. We stack them up and use them for 9--ft.--tall aggregate storage walls.” These blocks are made from unused concrete returned on ready--mix trucks.

Some concrete recycling could become unnecessary if concrete contractors did a better job of calculating how much ready--mix they need, Beers noted. “We are flabbergasted at the amount of concrete that comes back to us from the contractors,” he says. “If you order the correct amount of concrete, you pay less and we don’t have to worry about what to do with it when it comes back in.”