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What is Concrete Recycling?

Jeremy Laukkonen
Jeremy Laukkonen

Concrete recycling is the process of reclaiming some of the rubble from demolished buildings. In the past, concrete from demolished buildings was disposed of in landfills. New techniques resulted in this wasted material being recycled into new uses. Concrete recycling typically involved crushing old material into small aggregate and then using it as gravel or as a component in fresh concrete. If concrete has been contaminated in any way it typically can not be recycled, though the presence of metal, such as rebar, is typically accepted.

The process of concrete recycling typically begins with the crushing of old concrete into smaller pieces. This part of the process may be repeated until an aggregate of sufficiently small size has been obtained. The aggregate may then undergo a number of different processes to separate out contaminants. Magnets are often used to remove rebar and other types of metal, though water flotation and other methods can be useful in separating out wood and other particles. Once the aggregate consists mainly of crushed concrete, it can be used in a variety of applications.

Old concrete that's ready for recycling.
Old concrete that's ready for recycling.

One of the simplest uses for recycled concrete is as a gravel substitute. The concrete may be used alone or as a base layer for asphalt or other substances. This is one way that worn out old roads may be reprocessed to drive down the costs associated with new road construction. If the aggregate is sufficiently free of contaminants, it may be used to make new concrete. In this case, some or all of the rock or gravel present in most concrete will be be replaced by recycled aggregate.

Wet concrete being poured.
Wet concrete being poured.

Aggregate obtained from concrete recycling may also be used in a number of other applications. If the product is clean and looks attractive, it can be used as a landscaping material. It can also be placed into wire mesh cages and used in the creation of retaining walls.

The two main purposes of concrete recycling are to achieve a positive environmental impact and to reduce the costs associated with new construction. A positive impact on the environment can be achieved simply by recycling a material that would otherwise take up space in a landfill. There may also be less energy expended in crushing and sorting old concrete than would otherwise be used to mine and process new rock or gravel aggregate, which can potentially reduce the carbon emissions associated with a project. Costs may be reduced in a similar way, as it may be cheaper to process old concrete than to purchase new aggregate.

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    • Old concrete that's ready for recycling.
      By: Taweesak Ngamamornpi
      Old concrete that's ready for recycling.
    • Wet concrete being poured.
      By: uwimages
      Wet concrete being poured.
    • Magnets are used to remove metal reinforcing bars, or rebar, before concrete is recycled.
      By: wittybear
      Magnets are used to remove metal reinforcing bars, or rebar, before concrete is recycled.