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While the 2004 packaging recovery figures posed few problems for the glass industry, its targets for the next four years increase more steeply than any other material. According to British Glass, an increase of 120,000 tonnes of glass recycling is needed in each of those years if this huge jump is to be achieved - a daunting task by anyone's standards.

However, in the quest to create end use markets The Waste and Resources Action Programme (WRAP) has announced the results of, what they say is, the widest-ever study into the performance of waste glass as an aggregate and pozzolan in concrete manufacture.

The ConGlassCrete I and II studies, conducted by the Centre for Cement and Concrete at the University of Sheffield concluded that ground glass pozzolana is suitable for use as a pozzolanic cement replacement material and that concrete products containing waste glass complied with appropriate British Standards.

As a result of the research, BRE Certification has produced a pre-certification report stating that ground glass pozzolana is suitable for use as a pozzolanic cement replacement.

Andy Dawe, material sector manager for glass at WRAP says: "The use of waste glass as an aggregate and pozzolan in concrete manufacture has huge potential that has not been exploited due to a lack of standards and third party certification.

"These projects have been extensively researched by industry and the University of Sheffield, and third party certification for the use of glass from various waste streams in concrete has been achieved. Industry now has tentative specifications and pre-certification reports that may increase confidence in glass as a material that can be used in concrete, especially as a pozzolan and decorative aggregate."

The ConGlassCrete I Project found that all products made with waste container glass have equivalent type test results to products made with natural aggregates and that after one year, dimensional stability tests indicated detrimental reactions between cement and glass only occur when high-alkali Portland cement is used.

However, according to WRAP, the project clearly demonstrated that the use of alkali-silica reaction (ASR) suppressants almost totally eliminated these effects at one year and how glass particle size of less than 1mm may also reduce ASR effects.

According to the ConGlassCrete II report, while some markets for recycled waste glass do exist in construction - 200,000 tonnes as aggregate in asphalt, pipe bedding, backfill, loose fill, decorative use and golf bunkers - there is "huge potential" to increase usage in the concrete construction sector. It says: "Finely ground glass has the appropriate silica (Si02) content to react with dissolved calcium hydroxide in the presence of water and form hydrated compounds in a similar way to pozzolanic materials such as pulverized fuel ash (PFA), ground-granulated blastfurnace slag (GGBS) and microsilica (MS)."

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