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Watchword sustainability

The Concrete Centre and The British Cement Association are putting together a 'sustainability team' to develop and implement an environmental strategy. The team will include representatives from both companies and trade associations, and will look at two potential mechanisms for improving concrete's contribution to reducting CO 2emissions: increased use of recycled materials in manufacture; and using concrete in construction to minimise environmental impact.

'The cement and concrete sector has been addressing how sustainable thinking can be applied to its manufacturing processes and to concrete construction for some time, ' says Anna Scothern, head of performance in practice at the Concrete Centre.

'Substantial progress has been made in using alternatives to fossil fuels for cement manufacture.'

One alternative fuel source is the 28M used tyres that are dumped in landfill every year.

Castle Cement uses them for its cement kiln, burning 1,000 waste tyres a day at its Ketton plant in Rutland.

Scothern says other waste products that can safely and environmentally be recycled for fuel in cement production include solvents, domestic refuse and sewage sludge.

The cement industry has for many years used waste products as a constituent material, with waste ash from power stations - pulverisedfuel ash (PFA) - now a recognised component of Portland PFA cement. Lafarge Cement UK at Westbury in Wiltshire also uses PFA as an alternative to clay and, by altering the chemical balance, the plant reuses its own principal solid waste, cement kiln dust, which was formerly landfilled. As a result 100,000t less virgin material is quarried each year, and 120,000t of material is recycled instead of being sent to landfill sites.

Similarly, the slag waste from blast furnaces is ground to produce cement. And the gypsum that is a waste byproduct of the desulphurisation processes installed at coal-fired power stations as part of the acidrain reduction programme can be substituted for mined gypsum in cement making.

Recycling is well established within the concrete sector, with old concrete frequently crushed and re-used as aggregate.

The use of recycled and secondary aggregates for construction has increased by 94% from 1989 to 2002.

Buildings that are demolished are increasingly being crushed for use as aggregate, with up to 95% of the structure of some concrete buildings being recycled.

This means less use of natural aggregate resources and a reduction in the volume of waste going to landfill.

The industry is also highlighting the contribution concrete can make to reducing energy consumption in completed buildings.

Around 90% of the total energy used in buildings is for heating, cooling and lighting, so designers are keen to find ways to reduce this.

Concrete's thermal mass can be used to absorb, store and radiate heat and, when combined with natural ventilation, can also reduce the need for air conditioning.

The industry's new sustainability team will develop medium and long term strategies to increase the sustainability potential of concrete, and organise seminars to communicate some of these issues.

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