Fact file on recycled concrete

Recycling concrete reduces natural resource exploitation and associated transportation costs and reduces wastes going to landfill. However, it has little impact on reducing greenhouse gas emissions. Twice as much concrete is used in construction around the world than the total of all other building materials, including wood, steel, plastic and aluminum. Here are some facts about the recycled concrete:

• Concrete cannot be recycled

Although concrete cannot be broken down into its constituent parts, namely cement, aggregate, it can be recovered and crushed for reuse as aggregate, in ready-mix concrete (RMC) or other applications

• Recycled concrete aggregate cannot be used for structural concrete

It is generally accepted that about 20% (or more) of aggregate content can be replaced by recycled concrete for structural applications.

• Although some concrete can be recycled it is not possible to achieve high rates

Countries such as the Netherlands and Japan achieve near complete recovery of waste concrete

• Concrete can be 100% made by recycling old concrete

The recycled concrete can be used as aggregate in making new concrete but (a) new cement is always needed and (b) in most applications only a portion of recycled aggregate content can be used. The regulations often limit content as do physical properties, particularly for structural concrete

• Recycling concrete reduces greenhouse gases and carbon footprint

Most greenhouse gas emissions from concrete production occur during the production of cement. Small GHG savings may be made if transportation needs for aggregates are reduced by recycling

• Recycling concrete into low-grade aggregate is down-cycling and is environmentally not the best solution

A full life cycle assessment needs to be undertaken. Sometimes low-grade use is the most sustainable solution as it diverts other resources from the project and uses minimal energy in processing.

• Recycled aggregate is more expensive

It depends upon the local conditions, including transportation costs

Source: The Cement Sustainability Initiative, World Business Council for Sustainable Development