Cutting Emissions On The A45

02 June, 2008

As you read this, work has just started on a scheme to reconstruct 480metres of carriageway on the A45 near Prior Deram Walk in Coventry. The Tarmac National Contracting project using its FoamMaster product promises to halve the carbon dioxide emissions that would be released if a hot mix asphalt were used. MQR decided to find out more.

For all local authorities, cutting carbon emissions and hitting recycling targets while maintaining highways can often be a bumpy ride. Yet, for Coventry City Council, the benefits of recycling up to 95% of a road surface and then re-using it to reconstruct the very same carriageway, is helping to cut carbon emissions as well as promote the use of secondary materials.

Coventry is using Tarmac’s FoamMaster, a sustainable road surfacing system that uses road arisings and other recycled aggregates as an energy efficient alternative to traditional hot asphalt.

This time the system is being used by Tarmac National Contracting to reconstruct 480metres of carriageway on the A45 near Prior Deram Walk. It is being undertaken as part of the company’s four-year road maintenance partnership agreement with Coventry City Council and builds on the successes of two similar road reconstruction projects undertaken by the company for the local authority.

The project breaks down as follows. The Tarmac team will plane to a depth of
200-300mm removing 2,662tonnes of road arisings. It is projected that around 54% of this material (1,430tonnes) will be reprocessed on-site using specialist plant equipment.
This material will then be blended with pulverised fuel ash to produce a foamed bitumen-based asphalt suitable for the road’s new binder course and base materials to a depth of around 250mm.

Developed by Tarmac’s recycling division, the FoamMaster mix is tested to ensure that it meets the requirement for stiffness and standards specified in SHW 948 &TRL 611, 2004, which regulates the use and specification of cold-lay recycled materials.
Malcolm Spandley is highways maintenance programme manager for Coventry City Council. He says there are significant environmental advantages to adopting systems such as FoamMaster.

Spandley: “Since 2006, we have worked with Tarmac using the system on appropriate deep road reconstruction schemes around the city.

“It is an energy efficient manufacturing process which saves material going to landfill while at the same time helps us conservs virgin aggregates. This is vital to helping us meet our commitment to conserve resources, minimise energy output and reduce waste.”

Counting the cost of carbon

The A45 scheme will cut carbon emissions by over half compared with the emissions that would be emitted by using traditional hot mix asphalt techniques, says Kevin Marshall, business manager for Tarmac National Contracting.

He continues: “Our analysis, which is based on modelling the carbon costs associated with conventional methods versus FoamMaster, produces a calculation for the transportation of constituents and waste arisings, the mixing of constituents as well as the transportation of product and plant.

“Ordinarily, we have calculated that for a scheme such as the A45, around 64tonnes of carbon would be emitted. Using FoamMaster will deliver a total carbon saving of around 32tonnes of carbon for this project.”

Reducing the number of transport movements

Reprocessing road arisings on-site contributes a great deal to these carbon savings and helps reduce lorry movements. Marshall says his projections indicate “...that we will save around 2,726miles compared with transporting aggregates in from further afield.”

He continues: “As well as delivering transport emissions savings, fewer lorry movements to site means that the job can be completed more quickly with less disruption to local residents and motorists.”

Road to sustainability

While the capability to recover worn out roads and recycle them has existed for sometime, some local authorities have perhaps initially been reluctant to implement these technologies. But this now appears to be changing.

Local authorities such as Coventry City Council are increasingly adopting a sustainable approach to road repair and maintenance work. Driven by the implications of Agenda 21, local authorities have an obligation to develop an environmental programme for their area based on the principles of sustainable development.

This has resulted in specification target levels of more than 10% use of recycled and secondary materials in suppliers’ products, which can include highways contracts.
In addition, the introduction of the Waste Acceptance Criteria in 2004, which brings more stringent tests for all material for landfill, is also increasingly focused on adopting more sustainable methods.

Tried and tested systems such as FoamMaster help to increase authorities’ confidence in recycling options and further boost adoption of these technologies.

Dealing with hazardous waste

And as well as lowering carbon levels and boosting the use of recycled aggregates in road-building, these systems can also cut down on hazardous waste costs.

The A45 reconstruction scheme does not contain contaminated tar material but if it did it could carry disposal costs of around £110 a tonne, says Marshall.

However, systems such as FoamMaster can remove this overhead. If traces had been found through the pavement survey and investigation, contaminated planings could be reprocessed to produce the end product solving any expensive disposal issues.

Just a few years ago it would have been unusual for a business such as Tarmac to talk about methods and innovations that actually reduced customers’ use of primary aggregates.

Now, as markets change and local authorities face new challenges, companies such as Tarmac must step up to the line to help local authorities manage the environmental impact of road maintenance projects by helping them to cut carbon emissions as well as minimise waste as authorities strive to find more sustainable ways of keeping the UK’s traffic flowing.