Recycled aggregates

Recycled and secondary aggregates are making an increasingly important contribution to the UK's needs.

By reducing demand on primary aggregates, they are helping the industry to become more sustainable - in other words, not using up assets today that our children may need tomorrow.

The industry is enthusiastically supporting the Government's drive to bring more recycled aggregates into play and, by 1999, had already exceeded the target set for 2001. It is well on its way to beating the 55 million tonne-a-year goal set for 2006.

Significantly, Britain has sailed ahead of previous leaders Holland in the European recycling league. While the Dutch manage to satisfy 14.6 per cent of their aggregate needs through recycling, we are close to 17 per cent. Third-placed Germany achieved just half that figure.

Recycled materials

Materials suitable for use as recycled or secondary aggregates fall into two broad groups:

• Demolition and construction materials - some 60 per cent are already used as aggregates and fill
• Industrial by-products such as:
  • colliery spoil - widely used for bulk fill
  • china clay waste - used in some areas as mortar and concreting sands
  • power station ash (PFA) - used as a cement substitute and for block making
  • blastfurnace slag from the iron and steel industries - used as aggregates and cementitious materials
  • slate

Challenges to be faced

The challenges that go with recycled and secondary aggregates are threefold:

• environmental - recovery of some wastes that have become part of a local landscape can have environmental consequences. Slate tips are an example
• technical - quality constraints have to be considered. An absence of adequate technical specifications has inhibited wider use of recycled materials to date
• economic - recycling isn't always cheaper. Transport costs, for example, can make recycled aggregates prohibitively expensive in some areas.

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