A new type of concrete for road building has been developed as an alternative to asphalt or traditionally made concrete in pavements. The material is more energy efficient, means less potholes and maintenance, is cheaper to make and is ready for use immediately after it has been laid, helping to reduce road closure times and traffic jams. Another key benefit is that, when it is disused, the material can be taken away, crushed and recycled for use in a new pavement.
The new roller-compacted concrete (RCC), which has been developed by researchers at the University of Sheffield and EU partners as part of the EcoLanes project, consists of dry mix concrete reinforced with recycled steel fibres from waste tyres, and is 12 per cent cheaper than conventional road construction. It also reduces construction time by 15 per cent, bringing a 40 per cent reduction in energy consumption over its lifetime.
The new concrete material uses a very different consolidation method, roller compaction, which means that the dry mix requires less cement than conventional concrete and is stable enough for light traffic straight after being laid. Finding a suitable reinforcement material that is also compatible with roller compaction technology, such as fibre reinforcement, was the initial challenge that led to the Ecolanes project.
The researchers undertook a number of successful demonstrations in different countries to ensure the technology could operate under a range of climatic conditions. Concrete laid with roller compaction technology utilises a similar technology as that of asphalt construction, making it ideal for future construction projects.
The success of the Ecolanes project, which started in 2006, has meant the team are developing new guidelines that assume the benefits of fibre reinforcement and allow for the design of thinner pavements. It could also lead to tyre recycling plants that produce tyre wire for these new concrete applications, which would have the advantage of increasing the profitability of tyre recycling and helping the industry comply with EU landfill directives.
However, work still needs to be done to convince the construction industry to introduce new codes of practice that accept fibre-reinforced RCC. The researchers are aware that they need to develop their guidelines so that they can be used in codes.
The next focus for their research will now move to recycled aggregates, as they are suitable for fibre reinforcement and would help reduce costs further.
Laurie Donaldson