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Can we recycle aggregates?

Yes we can.

these symbols are used to show that construction materials can be recycled
Aggregates are quarried from rocks that have been chosen because they are strong and also resistant to chemical attack. This means we can recycle the construction materials of which aggregates are the major ingredient. In Victoria in 1999, about 70% of the concrete and bricks in construction and demolition waste were recovered and recycled for re-use. For asphalt, the recovery rate is even higher … close to 90%.

By recycling construction materials we reduce the need to make new natural aggregates. We also reduce the amount of waste that goes to landfill. The substitution of recycled construction materials for natural aggregates helps extend the lives of existing quarries and also extends the lives of existing landfill sites.

But we need to be careful. Recycled concrete is recovered from the demolition of buildings and road pavements. It contains a mixture of aggregates as well as other materials such as mortar (sand and cement) and possibly bricks and rock rubble. This makes it more difficult to predict the strength and durability of the recycled concrete.

It would be dangerous to use re-crushed concrete on its own to build a high-rise building or a new bridge when we couldn’t predict exactly what would happen. We therefore tend to use recycled construction materials in situations where we know they can be used safely. We might use recycled construction materials as a substitute for natural aggregates to make a new base for a road, carpark or footpath or bicycle pathway for instance.

We can blend a certain amount of recycled construction materials with natural aggregates to make new concrete. Certain products like asphalt (which we use for road surfaces) can sometimes be recycled in place by using special machines.

Every year we learn more and more about recycling construction materials. We need to continue to find improved ways to recover and recycle ‘pre-loved’ aggregates. Recycling may be able to provide about 10% of our total aggregate needs. But most of our community need for aggregates must come from new natural aggregates. This is why it is important that we have new quarries and use all the available resources in existing quarries.

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