Concrete Recycling Process

Recycled concrete can be used again instead of thrown away.

In the past, concrete from demolition sites was trucked to a landfill. Today, however, concrete recycling has become very popular for environmental and economic reasons. Concrete is collected at a demolition site, then is crushed to form aggregate for new concrete. Recycled concrete is currently used to construct new buildings, roadways and even airports.

Initial Breaking Process

Concrete is first broken down through traditional demolition techniques, including jackhammers, wrecking balls and explosives. It is reduced to chunks ranging from 30 inches to four feet. These chunks must be relatively free of major contaminants such as trash, wood, glass and other materials. The broken concrete is taken to recycling plants in large trucks, or portable plants are brought to the demolition area to perform the recycling process on-site.

Crushing

The broken concrete rubble is loaded by bulldozer into an initial crusher, which can be adjusted to accept many different sizes of rubble. The crusher uses several rollers covered with interlocking teeth to reduce the concrete rubble into smaller pieces. These pieces are then sorted by size. Ones that are still too large will go through additional crusher passes, while smaller pieces move on to be filtered.

Filtering

Crushed concrete passes along a conveyor belt under a strong electromagnet, which pulls out pieces of iron rebar. This rebar is separated for recycling in a different facility. The concrete is then passed through a water chamber, which causes small, light contaminants such as wood and paper to float to the top. Finally the rubble is inspected visually and with electronic air blowers to remove any contaminants that still remain.

Reuse

Recycled concrete aggregate is mixed with virgin aggregate, sand, water and Portland cement to make fresh concrete. Concrete with recycled material is typically used in the sub-base layer on construction projects, however, there are no requirements stating where recycled concrete may or may not be used. The recycled concrete aggregate is lighter and stronger than virgin aggregate and helps to minimize both construction costs and environmental impact.

References

• Zhengzhou YiFan Machinery: Recycling Concrete
• Concrete Network: Recycling Concrete
• CMRA: How Concrete Is Recycled