Road Recycling In The Spotlight

Tarmac describe their involvement in the biggest road-recycling contract carried out in the UK

As the Government increases its focus on sustainable development, so the aggregates and asphalt industries are looking for new ways to process and apply recycled or secondary aggregates in a way that will meet the quality assurance standards specified by the Highways Agency.

In recent years, technological advances in the use of mobile plant and equipment have changed the way that highway-surfacing contracts are managed. This has been driven by a number of factors, not least an increasing focus on sustainability among local authorities following their adoption of Local Agenda 21, which specifies a target level of 10% for the use of recycled or secondary materials in suppliers’ products.  

It is not unusual for a local quarry to provide the virgin materials used to complete the surface course, whereas sub-base, base and binder courses can be produced from recycled planings removed from the existing road surface. As well as conserving virgin aggregates, this sustainable construction solution can also be much quicker to apply, as the recycled ‘foam-mix’ is a cold-lay roadstone product, used as an alternative to hot-laid materials in base and binder layers.

Rod Calder, contracting director – southern at Tarmac, explained the effect this is having on the aggregates and asphalt industries: ‘The aggregates industry welcomes the increasing focus on recycled or secondary aggregates and in response quarries are finding that they are providing a more efficient, streamlined service to contractors to ensure that they get the right amounts of virgin materials in a timely way.

‘At Tarmac we are helping to accelerate progress to the road recycling future by investing in this part of our business and ensuring we have mobile plant capable of processing planings and other suitable waste materials to the required standards. In doing so, we are effectively making existing roads the quarries of the future. Demand for virgin materials will remain, of course, but we intend to conserve these materials for as long as possible.’

Earlier this year Tarmac completed the biggest road-recycling contract ever carried out in the UK, on behalf of the Highways Agency, on the A38 in Devon. While the use of road recycling in highway resurfacing is not new, this project is by far the largest of its kind to date. In order to resurface the 12km route between Plymouth and Exeter, Tarmac produced about 100,000 tonnes of road planings ,of which some 70,000 tonnes were recycled as ‘foam-mix’ for use in the reconstruction of the carriageway.

Nigel Holpin, South West general manager of Tarmac’s national contracting business, commented: ‘Just to give an idea of the scale of this project, before starting work in September last year, the largest road-recycling scheme we had carried out was for the Welsh Assembly, which involved using 30,000 tonnes of recovered asphalt. Prior to this we had recovered about 2,500 tonnes of planings for use on a 1.7km stretch of the M6 in Cumbria.

‘The A38 contract allowed us to demonstrate just how far our capabilities have come and has provided a model of sustainable road construction for the future.’

In specifying this road-recycling contract, the Highways Agency wanted to optimize the use of the recycled materials to create a road surface that would support heavy commuter traffic in the longer term and reduce the need for short-term maintenance.

While planning the programme of works, Tarmac established at an early stage that it would be necessary to develop an ex-situ processing solution. While traditional planing equipment was used on the site, other plant required for crushing and grading the planings was located just a few miles away at Linhay Quarry. Here the planings were crushed using mobile crushing equipment. The 10–28mm planings were then used to produce FoamMaster, a high-performance foamed bitumen, which was then used as a base course for the new road surface.

Nigel Holpin commented: ‘Normally, when implementing road-recycling contracts, we aim to do as much of the processing as possible on site or very close to the site. In this way we can minimize traffic movements and complete the contract more quickly. In this case, the sheer volume of planings being removed and the constraints of the site meant that we needed to take the materials off site.

‘When a suitable location adjoining the site became available during the final phase of the contract, we were able to move the processing plant and equipment even closer.’

When using recycled materials, it is especially important to ensure that the quality of the road surface is maintained to the standards required by the Highways Agency. The recycling mix was performance tested to ensure it fulfilled TRL 611, ‘2004 – a guide to the use and specification of cold recycled materials’. Achieving this quality and performance criteria has effectively created a new benchmark, which local authority engineers and contract teams can specify against in the future.

Nigel Holpin added: ‘The success of this contract really opens up opportunities for road-recycling contracts around the UK. For the first time, we can talk about real ‘linear quarrying’ and we now know that high-performance, sustainable road-surfacing solutions are achievable on a major scale. We have experience of delivering technical solutions that are capable of meeting the capacity demands of the project while optimizing quality and minimizing traffic disruption.’

Since the start of 2006 Tarmac have invested in the acquisition of the road-planing business National Road Planing Ltd, and in new mobile recycling plant and equipment, which has further extended their recycling capabilities. The company views this investment as a sign of their commitment to the road-recycling future and their responsible approach to the use of virgin aggregates.

Rod Calder concluded: ‘Aggregates and asphalt businesses have been accused of being slow to support recycling initiatives and the use of recycled materials. By focusing on developing contracting solutions that provide a practical and high-performance alternative we are showing our commitment in this area, and our quarries have an important part to play in making sure they can fulfil the new demands of these contracts.’