Driving the use of recycled aggregates

John Barritt, Technical Advisor for Aggregates, at WRAP on reducing consumption of new quarried materials

Almost 280 million tonnes of aggregates are used every year in UK construction. This article looks at how recycled aggregates can play a part in the procurement for roads, reducing the consumption of new quarried materials.

Recycling and the efficient use of materials are increasingly important to the delivery of local authority services. While around half of local authorities use recycled materials in highways projects, only some 20 per cent are currently setting requirements that actively encourage contractors to maximise use and seek the associated cost savings. There is the potential for many more authorities to encourage and drive change through the procurement process.

The approach to procurement should ensure that recycling and reuse of road materials is embedded in all highways contracts and schemes. By specifying requirements for the use of recycled content in a highways contract, you help to meet your authority's policy targets. This may include sustainability, procurement good practice, 'Best Value' and waste management - in compliance with national strategies and Government requirements.

Recycled aggregates meet the performance specifications for all aggregates in the Specification for Highways Works. A wide range of recycled products are available, whose quality and performance are fully comparable to their virgin equivalents. New processing techniques are also resulting in a higher quality aggregate, which is suitable for use in a number of high value applications - such as concrete and asphalt. Almost every highways maintenance application can use recycled and secondary materials. These include aggregates for the asphalt and unbound layers of road pavement structure, engineering fills, pipe bedding, block paving and drainage media.

Importantly for local authorities, there are clear financial benefits to be gained from using recycled products and recycling techniques in highways maintenance, as well as the environmental contributions to sustainable development, including reductions in C02.

Financial benefits

Across the UK, local authorities spend roughly £3 billion each year on highways construction and maintenance. Therefore, the overall financial benefit from good procurement practice will be substantial. Road materials are 100 per cent recyclable back into roads and there is a strong business case for local authorities to view them as assets. The use of recycled materials for highways maintenance is often at least cost neutral, and in many cases can deliver good financial returns.

Some specific cost savings associated with using recycled aggregates include:

  • Avoidance of waste disposal charges and Landfill Tax;
  • Lower costs of maintenance techniques such as 'crack and seat', cold-lay foamed bitumen asphalt, and reprocessing with hydraulic road binders;
  • Reduced costs of transporting aggregates if recovered materials are available locally;
  • In-situ recycling can reduce the duration of traffic disruption by around 50 per cent; and
  • Foamed concrete can allow faster trench filling with fewer people.

Environmental benefits

Substituting virgin materials with recycled materials in highways maintenance can deliver clear environmental advantages, decreasing energy consumption, and diverting waste from landfill sites. Some of the most successful local authorities have 'closed the loop' by using waste materials produced locally.

For example, the use of recycled materials on the Burntwood Bypass in Staffordshire saved nearly 200,000 miles of lorry movements, equivalent to 128,000 litres of fuel - and the financial saving on the project was £60,000.

Local authorities should consider the following six tips for encouraging the use of recycled aggregates in roads:

  • Set objectives for recycled content, based on your authority's core objectives for
    sustainability and waste management;
  • Make choices within your form of contract to provide a positive context for introducing recycled content - particularly by developing partnering arrangements;
  • When inviting tenders, you should specify objectives and quantitative requirements for recycled content;
  • When evaluating tenders, give credit for those that offer higher recycled content and associated benefits;
  • Set key performance indicators and targets for improvement, and allocate risks and rewards accordingly;
  • During contract extension, introduce requirements and indicators that create incentives to use recycled content.

Case study: Ex-situ recycling of trunk road

The reconstruction of part of the A38 in South Devon demonstrates how a sustainable alternative to full pavement reconstruction can be delivered by traditional contractual and supply chain mechanisms.

A permanent and widespread solution was investigated to solve the rapid deterioration of the A38. Ex-situ recycling was adopted after aspects of cost and sustainability were considered. One particular aspect that made recycling relatively straightforward to control was the uniformity of the material being recycled. There were a number of 'quick wins' that could be easily made by choosing materials with a higher level of recycled content, at no extra cost or compromise on performance. So, many financial, environmental and logistical benefits were achieved:

  • The recycling costs represented an estimated saving of around £300,000, compared with conventional reconstruction;
  • If full reconstruction was carried out, an additional 70,000 tonnes of primary aggregate would have been required;
  • Switching from a hot mix bituminous mix to a cold bituminous (foam) mix and reduced transport distances saved 55 per cent (2,000 tonnes) of the total CO2 emissions of a conventional construction method; and
  • Although the recycling operation was ex-situ, the recycling plant was only around 1km from the works, which meant that materials required minimal transportation.

Support available

WRAP provides free guidance to anyone involved with the procurement of highways