New surfacing technology could help the UK meet environmental targets
contractjournal.com Newsletter: 09.06.05
New surfacing technology could help the UK meet environmental targets
An innovative British designed surfacing technology could hold the key to the development of more large scale composting sites, needed to help the UK achieve new European environmental targets. The highly effective and durable asphalt product, called Durafalt 'C', has been developed by BP Bitumen and Hanson Aggregates as a lower cost and high performance alternative to concrete for the critical surfacing of windrow composting processes, where the material is piled in elongated rows and aerated.
"Because Durafalt 'C' costs much less than concrete, and is also quicker to install, composting companies can now afford to surface larger areas and produce more recycled material, increasing the reduction of organic wastes from landfill," said Chris Field from The Composting Company, who designed and project managed the construction of the new 50,000t p/a West London Composting (WLC) site in the London Borough of Hillingdon last year.
Durafalt 'C' has been successfully trialed at the WLC plant and also at Cleanaway's integrated waste management facility at Rainham in Essex. BP and Hanson are now hoping that the rest of the UK composting industry will take advantage of the new technology.
"The timing could not be better," Field added. "The need to meet EU targets is now bringing about a major increase in composting activities throughout the UK and, in order to divert the volume of biodegradable waste from landfill, as required by the EU landfill directive, hundreds of new composting sites are required by 2020."
Cost savings
Windrow composting areas in the UK have traditionally been surfaced with concrete, which is both expensive and time consuming to lay. In the past, the use of standard asphalt as a lower cost alternative, has been prohibited by EU legislation.
"There is a significant cost saving from using Durafalt 'C' instead of concrete," said Hanson's Tony Zigler. "Asphalt is also quicker to both place and to repair in the case of damage. Conventional asphalt would be prone to chemical attack from acidic leachates, which are a by-product of the composting process. This would mean it would become necessary to repair the surface frequently, and may result in contamination of water courses."
A key component of Durafalt 'C' is Olexobit FRB, a polymer modified binder developed by BP Bitumen and used, in this application, to provide resistance to elevated temperatures and chemical attack. During the biological decomposition process the core of a windrow can reach temperatures of 70 – 80°C.
Performance tests have shown Durafalt 'C' to have a low air-void content, low surface texture, high deformation resistance and good fuel resistance when compared to traditional asphalt surfacing materials. Durafalt 'C' utilizes a continuous aggregate grading to give a strong mechanical structure and a low surface texture to give improved shedding of leachates, effective impermeability and a resistance to marking from slow moving, heavy and turning traffic. Durafalt 'C' should be laid at a nominal layer thickness of 40mm, and on SMA binder course or equivalent, and is laid by a traditional asphalt paver, with rolling by a minimum 10 tonne dead-weight, or equivalent vibratory roller. Special attention should be given to compaction, particularly, at the joints, which should be painted with BP Olexobit FRB joint paint.