Emerald Knight

Energy efficient concrete could ease road closures  

• 20th October 2010
• Comments (2)

A new development in the production of concrete for paving new roads could cut building costs and reduce the amount of time routes need to be closed. Researchers on a project led by The University of Sheffield experts have developed a new type of dry mix concrete which uses recycled steel fibres from old tyres as reinforcement.

The new type of surface not only recycles the steel from used tyres, it is 12 per cent cheaper to produce than traditional concrete for roads, takes 15 per cent less time to construct and across the lifetime of a concrete pavement results in a 40 per cent reduction in energy consumption.

The EU produces some 3.2 million tonnes of tyres each year, which all has to be recycled. The tyre production process involves reinforcing steel threads which account for 15-25 per cent of the tyre, and which are often unsuitable to be recycled for new steel production as rubber and plastics in tyres hold on to the fibres.

Using these fibres in building new roads, The University of Sheffield and their partners in the EcoLanes FP6 project have been able to produce a concrete in a bid to create long-lasting, efficient transport paving for the continent. The use of these recycled steel fibres from post-consumer tyres is at least 50 per cent cheaper than buying new steel reinforcement, and as no raw materials need to be mined and formed, energy consumption is greatly reduced.

An additional benefit of the new concrete is that it doesn’t require roller-compaction to consolidate, and therefore uses less cement in the dry mix. The new type of concrete is also stable enough for light traffic straight after being laid, rather than having to wait for the 7-28 days usually required when laying conventional concrete. This would significantly reduce road closure times and traffic problems, as well as easing labour and machinery cost pressures as equipment and manpower needs to be on site for less time.

Various durability tests have since been carried out by the development team, with very encouraging results to date. The team have exposed the road surface to 40-degree Celsius variations in temperature on a constant cycle over 56 days, immersion in salty water to test corrosion levels. Other tests have included a simulation of extremes of temperatures and moisture by bending the road surface and submitting it to one million load cycles – in which the new concrete proved to be very durable.

One other test on the new concrete road was to subject the road to 1.5 million cycles with a single axle load of 11.5 tonnes – after which the surface was still performing well, indicating that over 30 years of use the surface would still hold up.

The EcoLanes construction concept has also been validated in a number of European environments, which should begin the process of introducing the road surface for widespread use in the future.