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2020 / 2021 Edition

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Cotswold Contamination

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Asphalt

In Gloucestershire the need to upgrade the A40 would have meant extra landfill costs because of the presence of tar. Instead the council is using Tarmac’s FoamMaster road recycling product, which is saving money as well as helping to halve CDE waste volumes going to landfill by 2012.Tarmac’s director of recycling, Alan Sheppard, explains further.

With the introduction of the new landfill regulations and the Government’s industry target of halving the amount of construction, demolition and excavation (CDE) waste sent to landfill by 2012, local authorities are under increasing pressure to review their waste management processes and undertake alternative methods of waste disposal.

Tarmac’s national road surfacing contracting arm is at the forefront of investing in the development of new road surfacing technologies which use recycled materials and prevent the amount of road arisings sent to landfill.

One of these is called FoamMaster and it involves planing and recycling the existing carriageway. It uses 95% of its constituents from road arisings and other recycled aggregates to produce new binder course and base materials.

But while the capability to recover worn out roads and recycle them for use in the construction of new road surfaces has existed for some time, local authorities have perhaps initially been a little reluctant to be first to implement these new technologies.

The hesitation is understandable. Few want to apply road recycling technology discountywide or within a city centre without assurance that it will provide a high performance and long-lasting solution.

However as a result of the new landfill directive and the introduction of Waste Acceptance Criteria (WAC) – which bring more stringent tests for all material sent for landfill – local authorities are now increasingly focused on adopting more sustainable methods.

Driven by Agenda 21, for example, authorities are increasingly specifying a target level of more than 10% use of recycled and secondary materials in suppliers’ products, which can include highways contracts. Tarmac has been working with a number of local authorities to design and implement ‘start-to-finish’ road recycling schemes.

The principal advantages of FoamMaster over conventional surfacing techniques is that it offers an energy efficient manufacturing process that can reduce transport movements – if it is manufactured on site – and conserves local primary aggregate resources.

Combining tried-andtested foamed bitumen technology with cold mix production and paving, Foam-Master is a sustainable, cost effective and environmentally friendly alternative to traditional hot asphalt materials. It is tested to ensure that it meets the requirement for stiffness and standards specified in SHW 948 and TRL 611, 2004, which regulates the use and specification of cold lay recycled materials.

Tarmac has a great deal of experience in the delivery of major road recycling contracts, including the UK’s biggest road recycling scheme completed to date on the A38 in Devon.

This contract was a breakthrough for the road recycling industry in general, demonstrating that sustainable asphalt was viable and practical on a large scale on heavily trafficked roads.

The work involved recycling approximately 60,000tonnes of the existing surface, which included tarbound materials. The re-use of the carriageway planings saved 300 lorry movements, as there was no need to remove these planings off site or bring in virgin aggregates from local quarries.

FoamMaster is currently being used in a number of projects across the UK, including a contract on the A40 in Cheltenham that Tarmac is undertaking on behalf of Gloucestershire Highways.

As with many roads, parts of it contain a proportion of tar, which is an issue for local authorities in terms of disposal of the tar material. It can cost up to £110 a tonne to dispose of tar based material. It cannot be dumped in landfill as inert waste just because it has come from a construction project because of the WAC regime demanding testing before it goes to landfill.

The A40 contract involves planing existing carriageway and re-processing the excavated material using Tarmac’s own on-site plant and equipment. This is then mixed to produce around 7,000tonnes of foamed bitumen-based recycled asphalt, which is used to construct the lower layers of the new road to a depth of about 250mm.

It is estimated that the scheme will save 180tonnes of carbon dioxide, reduce transport movements by 9,600 miles, divert 6,200 tonnes of planings from landfill and result in potential savings of over £127,000.

FoamMaster was also used recently on parts of the M1, resulting in considerable cost savings as it has diverted hazardous waste from going to landfill.

After initial site investigations on the M1, tar was discovered and the local authority was faced with the problem of how to dispose of it. By using FoamMaster £60,000 was saved by diverting the tar from landfill.

Tarmac has found that a number of local authorities across the country have been keen to take the lead and develop a more sustainable approach to road repair and maintenance work in light of the introduction of FoamMaster. And in doing so, they have been able to include it within their Local Minerals and Waste Frameworks, demonstrating their commitment to conserving resources, minimising energy output, and reducing the waste they produce.

Tarmac also produces a deferred set product, Remac, which takes planings and highways excavation waste and converts it into a cold lay material for footpaths and minor roads. This product can be stored for six-to-eight weeks, ensuring complete elimination of waste.

Even without the foamed bitumen materials, Tarmac has been able to help some local authorities to reduce their use of virgin aggregates by more than 10%.

This has been achieved by taking a pan-regional approach, so that planings recovered from one road are re-processed for use in the construction of other local new road surfaces through hot asphalt products.

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

Now we are at the forefront of developing innovative, sustainable options like our road recycling solutions that allow us to make use of recycled and secondary materials, thereby managing the environmental impact of road maintenance projects and minimising waste, while conserving our virgin aggregate resources.

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