Heart of glass

Britain's boozers could inadvertently be helping to fund the building of the nation's highways. Last Christmas, the UK threw away 490 million empty coloured glass wine, beer and spirits bottles - and the chances are that a substantial number of them will end up being recycled and used in road construction.

Materials firms like Lafarge and RMC are now recycling an increasing amount of glass each year for use in roads.

"It's a logical extension to the company's established business," says Andrew Bate, general manager of waste, landfill and recycling at Lafarge. "England and Wales produces around 1.4 million tonnes of coloured glass a year, and it obviously makes sense to provide a market for a waste material which would otherwise have no beneficial use."

Also, Bate points out, glass recycling kills two birds with one stone: "It helps local authorities achieve their recycling targets under Waste Strategy 2000 and meets the government requirement of the mineral industry to reduce dependence on primary aggregate."

Lafarge hopes to become a significant player in the glass recycling market, and has just secured Environment Agency accreditation for two of its glass recycling facilities, with three further applications in the pipeline. At its Harper Lane site in Hertfordshire, roughly six and a half million bottles are processed annually, although the site has the capacity to handle three times that amount. At the Ashbury site in the heart of Manchester, some eight million bottles are processed each year.

At both sites the waste glass is crushed and screened to produce an aggregate substitute which, when blended with primary materials, meets the requirements of both the Health and Safety Executive and Clause 29 (Bitumen Bound Layers) of the Specification for Highways Works under the May 2001 amendments.

Lafarge also has a 10-year roads maintenance agreement contract with Hertfordshire County Council, and as Bate puts it: "We now turn Hertfordshire's glass into Hertfordshire's roads".

Recycling potential

RMC Aggregates was one of the first aggregates firms to recognise the potential of recycling materials like glass. Sales of non primary aggregate products manufactured by the company have increased fourfold in the last five years.

"Support for recycled materials such as glass within construction has changed for the better as a result of government policy," says John Lay, the firm's technical services manager. "Local authorities and the Highways Agency now increasingly favour materials specified on the basis of performance rather than mix."

Three years ago, RMC launched Glasphalt, a material containing 30% crushed glass. It has been used in road construction layers as base and binder courses on all classes of road around the country.

The main ingredient of Glasphalt is green glass, which is ideally suited to the mixing process as it is relatively hard and its particles are consistent in size and absorb little moisture.

The glass is crushed using a mobile asphalt granulator and is later screened into six sizes before being mixed with primary aggregate and bitumen using conventional asphalt production methods. RMC is currently looking at ways to increase the proportion of glass in the material, and can now also include up to 20% recycled asphalt planings in place of primary aggregate.

Glasphalt was specified recently by Cheshire County Council for the repair of an existing binder course over a short stretch of the A533 in Northwich towards the end of last year.

The road in question is one of the main commuter routes into Liverpool and is popular with drivers of heavy goods vehicles. The carriageway was deeply cracked and rutted and was in a poor state of repair.

Cheshire County Council's senior highways engineer James Wood says: "As an authority, we are keen to put waste glass to good use. Specifying Glasphalt as part of our road maintenance programme is one way in which we can make good use of a sustainable material."

RMC recently set up its own steering committee to keep track of developments affecting the secondary and recycled aggregates sector, and one of its aims is to further increase awareness among both construction clients and contractors of the benefits of specifying recycled materials.

"Pressure on construction companies to use recycled materials has increased markedly, but many contractors still don't like taking what they perceive are unnecessary risks by specifying recycled aggregates," believes Lay. "We are trying to demonstrate to them that the appropriate technology to use secondary or waste material exists - and we are giving guided tours of our operations to show specifiers how we go about developing recycled products.

"The long term aim of our strategy is to change the culture of the industry to the point where all aggregates, be it primary or secondary, are regarded by specifiers as being of equal quality." n