An industry group, funded by investment from the Carbon Trust under the Industrial Energy Efficiency Accelerator (IEEA), has embarked on a two-year research initiative to develop a unique approach for more sustainable asphalt production. Led by Tarmac Limited, the project team consists of Nynas UK, Atkins and the Mineral Industry Research Organisation (MIRO).
The group aims to design, test and demonstrate the viability of semi-warm and cold-temperature asphalt as an alternative to the traditional hot-mix asphalt. The ultimate goal is to save energy in the asphalt production process, and reduce the carbon footprint of roads, by developing more carbon-efficient technology and new specifications that can be adopted across the UK.
Research conducted by the Carbon Trust has identified that the energy used to dry aggregates in existing hot mix production processes currently contributes 20 per cent of the carbon generated by the aggregates sector. Presently, asphalt in the UK is produced at temperatures ranging from 1500C to 1900C. The aggregates are heated at temperatures greater than 1700C to remove water, maximise the coating of the aggregates by the binder and improve the adhesion between aggregates and binder. The production of asphalt at warm or ambient temperatures will reduce or eliminate the need to dry aggregates altogether and maximise the use of recycled aggregates in asphalt.
Cold-mix technology has made significant progress over recent years to a point where it can be considered for use as alternative to hot asphalt in certain circumstances. Cold-mix asphalt makes a significant contribution towards meeting government safety, health and environmental targets and should interest all local authorities tasked with meeting government sustainability targets.
''This project is an important step in making the UK asphalt and road industry more sustainable and carbon efficient. By reducing the temperatures needed during asphalt production we can minimise energy consumption and achieve major reductions in asphalt-related carbon emissions. In addition to the technical research we're carrying out, this project will also deliver workable specifications that enable lower temperature asphalts to be adopted by UK highway operators." says Dr Nizar Ghazireh, project director at Tarmac Limited.
'Early indications are that this approach can also offer significant carbon savings in transportation (the major carbon contributor in the aggregates sector) through the use of mobile plants and manufacturing cold mix using locally sourced recycled asphalt planings," adds Dr Ghazireh.
"Low temperature asphalts have been used extensively overseas but the technology has not been employed as much in the UK. A major obstacle has been a lack of client understanding about the products and how they should be specified," continues Nynas UK's product application manager for cold paving technology Dennis Day. "The support from the Carbon Trust will enable the project team to engage clients in developing guidelines which will help them specify lower temperature asphalts - assisting the industry in reducing its carbon footprint."
"Engineering a low carbon future is core to every aspect of Atkins' work and this project will help to bring significant reductions in the industry's carbon footprint. The outcome will provide a means for highway authorities to address their carbon reduction commitments by deployment of the technology in maintenance and construction works undertaken everyday on the highway network," concludes Alan Taggart, Director, Atkins Highways and Transportation.
The benefits of using asphalt produced at lower temperatures have already been widely recognised across Europe. As part of the project, the group will undertake extensive production and demonstration trials to demonstrate the capabilities of semi-warm and cold-mix asphalt, including plant production, installation and in situ product performance.
The project team, led by Tarmac, will research and identify how these materials have been used and specified across Europe and through dialogue with key industry stakeholders develop a guidance note to facilitate their use across the industry. Tarmac and Nynas will work jointly using binder technology developed by Nynas in Europe and asphalt developed by Tarmac in the UK to lay the site trials. These sites will be monitored and evaluated by Atkins and Tarmac and the findings will be used to development working specifications.