Producers of pipe and structural precast products can find it difficult and costly to recycle their out-of-specification or damaged concrete units. Some products include so much reinforcement that it is hard to separate the concrete from the steel. Another cause of difficulty in recycling pipe is the relatively high 28-day compressive strengths the concrete can achieve. Concrete recyclers who use crushers and hydraulic breakers often charge producers higher tipping costs to handle these labor-intensive units. Engineers at Road Processing Resources (RPR) Inc., Vail, Colo., have found that energy waves of the proper frequency and strength cause a concrete mass to crumble and fall away from reinforcing steel. Since reinforcing steel is more flexible, the vibrations don't damage it or distort its shape. Using RPR's technology, pipe producers could turn the costly problem of recycling culls into a break-even operation. Engineers have drafted a system that RPS is ready to field test. The plans call for a self-contained unit that could rubblize round pipe of most common diameters. Operators will place a round steel anvil through the pipe and then lift the unit to within half an inch of the hydraulic hammer. The round anvil will turn the concrete pipe as the hammer's energy rubblizes the concrete. Broken concrete, in pieces smaller than 4 inches, will fall onto a portable conveyor under the unit's frame. Studies indicate that the process will take about five minutes per pipe piece and produce 75 to 125 tons per hour. RPS designers believe their rubblizing technology has two other applications. One unit, called the Panel Recycler, is designed to process general rubble such as precast/prestressed products and construction debris. Another application, currently in the planning stages, would remove and process pavements, primarily slipformed pavements, on 12-foot-wide highway lane at a rate of about one mile per day.

Keywords: Road Processing Resources, RPR, pipe, anvil, hammer, recycle