A study funded by the Waste & Resources Action Programme finds that abandoned airfields could be s a major potential source of recycled aggregates. However, the study finds that while the project won’t be effective on a national level, it might be successful on a more localized level.
The project, performed by C4S, a part of TRL Ltd., concluded that, although there are significant quantities of concrete and asphalt at abandoned airfield sites across the United Kingdom, the amount that could be recovered in practice would not make a significant contribution towards existing mineral planning targets for aggregate provision. However, it does identify five major airfields in the East of England where recycling the air strips could be economically and environmentally beneficial, particularly as they are situated in areas with the least permitted reserves of crushed rock.
WRAP says the research was necessary to ascertain to what degree disused airfields around England could provide a vital source of high quality recycled aggregates, thereby helping English regions to quantify the potential of this more sustainable resource in fulfilling their planning and development targets.
"Reserves of crushed rock in England vary from region to region and this often necessitates the transport of rock to areas where development is planned, but natural resources are low," explains John Barritt, Technical Advisor to the Aggregates Programm at WRAP.
Wartime pavement quality concrete is generally very clean and of prime quality, and some contractors and aggregate suppliers already actively seek out opportunities to reclaim concrete and bituminous materials from old airfields. The materials can easily be reused as type 1 sub-base in accordance with the Highways Agency’s Specification for Highways Works, which allows 100% recycled aggregate with a recycled asphalt content of up to 50 percent and therefore negates the need to separate the recycled materials. Nevertheless, segregation is feasible for a number of structural uses in concrete and asphalt if required.
The potential is significant: based on a concrete density of 2.4kg/m3, a single runway of 2000 meters in length and 45 meters width constructed with 300mm concrete contains around 64,800 metric tons of potentially reusable material. An airfield generally has at least two runways, plus taxiing and parking areas.
The research ascertained that not all of England’s 688 inactive airfields are suitable for recycling in practice. Some have been put to other uses, such as industrial parks, residential developments or leisure facilities, while others have had their air strips incorporated into the local road infrastructure or removed altogether. In addition, some have become heritage sites with listed buildings, museums and memorials so removal of the concrete air strips would not be appropriate. Other sites are so small that recycling would be uneconomic.
There are other barriers too: planning consent to recycle in situ can be refused on the grounds of noise and dust, particularly if the site is close to housing. The need to make provision for the disposal or treatment of associated substances, such as tar, asbestos, underground fuel tanks and contaminated soil, plus the potential for unexploded ordnance, can also make recycling concrete runways a less attractive option.
Taking these factors into account, the research calculated that suitable disused airfields could potentially yield 9.5 million metric tons of concrete, plus one million metric tons of asphalt planings. Around half of this total would come from just five large airfields based in the East of England - and this could be significant.
The final report, An assessment of the potential of redundant airfields in England as a resource for recycled aggregates, contains full details about the potential uses of recycled concrete aggregates and recycled asphalt, the results of the airfield survey and an assessment of the potential markets for recycled aggregates - including MDAs and major road schemes - in England. It is available to download from WRAP’s dedicated aggregates website www.aggregain.org.uk.