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Uses of Reclaimed Concrete

Reclaiming, or recycling, concrete is essentially breaking it up and crushing it into various sizes of what the construction industry calls RCA (recycled concrete aggregate). Before further use, foreign matter such as reinforcing steel must be removed, and the RCA cannot be treated in the same way as "virgin" aggregates, notes the Portland Cement Association (PCA), because it has higher porosity -- it contains hydrated cement paste after mixing with cement in the concrete-making process. Reclaimed concrete benefits the environment by keeping landfills clear and reducing the need for raw materials to come from the land itself.

  1. Requirements

    • Coarse reclaimed aggregates find their way into many forms of concrete, according to the California Department of General Sciences. In California, strict regulations surround their use; coarse or fine aggregate may go into only such applications as sidewalks, curbs and parking strips and may not exceed 50 percent of total aggregate. Regulations require thorough cleaning and washing and the absence of foreign matter, which could be asphalt, chlorides, glass, gypsum, plaster or wood, depending on the original use. Salt-contaminated concrete may not be used as RCA.

    Without Processing

    • The Portland Cement Association notes that unprocessed reclaimed aggregate mostly goes as a subbase for pavement and other uses such as bank protection, general bulk fill, base for drainage, noise barriers and embankments.

    Contaminant Removal

    • Once the contaminants are thoroughly washed away, RCA's uses expand significantly. RCA can go into new concrete, including structural-grade concrete. The Portland Cement Association says RCA should be treated like lightweight aggregate and "the paste content or amount of water reducer generally have to be increased." Concrete made from fine RCA needs special care, says the association.

    States Usage

    • Concrete reclaiming, or recyling is a major growth area. At the time of publication the Texas Department of Transport is a major user of RCA, taking 60 percent of the state's production, and finds after working with it since 2000 that RCA is an economical option. In Minnesota, almost 100 percent of the concrete removed from pavements becomes RCA. Virginia found the production costs of RCA were higher than new aggregate but handy location of production plants kept the overall cost down. The Indiana Department of Transportation allows 50 percent by weight of recycled materials on concrete bridge decks.

    O'Hare Experiment

    • In 2009 construction at Chicago's O'Hare International Airport included a field test of RCA. A lane of concrete with new aggregate was laid next to a lane using RCA. Sensors in the two slabs measured temperature, internal relative humidity and the slabs' lift off the permeable base. After five months the data showed no difference in behavior between the two.

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