The concrete industry places a heavy demand on primary aggregate sources; it is estimated that 165 million tonnes are used annually. There is therefore considerable incentive to develop alternative aggregate sources based on waste materials. The disposal of used vehicle tyres is one of the world’s largest environmental problems: over 40 million worn tyres are produced in the UK annually. The EU landfill Directive bans the disposal of whole tyres in landfill and shredded tyres will be banned from July 2006. Granulated rubber is obtained by mechanically shredding used tyres, during which the reinforcing steel is removed. It has been found that it can be used as a partial (say 6%) replacement for the aggregate in concrete. The result is a concrete that has similar resistance to freeze/thaw damage as air entrainment, a low thermal conductivity and an excellent resistance to impact.
For further information see Research Information Digest 5, Granulated rubber, published in CONCRETE in October 2005, pp 6–8. Copies are available as a free download from the Members Area of the Concrete Society web site.
The AggRegain web site may also provide information.