Articles
Who
Researchers at the University of Sheffield are helping to develop a new type of concrete road, made of dry-mix concrete reinforced with recycled steel fibres from waste tyres, that it claims is 12% cheaper than conventional road construction with a 15% reduction in construction time.
Technology
Every year in the European Union, 3.2 million tonnes of tyres are produced, all of which have to be recycled. However, 15-25% of the tyre is comprised of steel fibres, which hold a large amount of rubber and plastic from the reinforcement, limiting the options for reuse in new steel production.
The fibre-reinforced concrete developed by the team at the University of Sheffield and their EU partners as part of the EcoLanes project is able to use processed steel fibres for the first time. These recycled steel fibres are at least 50% cheaper than manufactured steel fibre reinforcement.
The new concrete uses a different consolidation method, called roller-compaction, which requires less cement than conventional concrete and is stable enough for light traffic straight after being laid.
The concrete, developed to create long-lasting rigid pavements for the transport industry, has been tested for its durability. The team kept the new material within a climate chamber for 56 days, with a daily changing temperature from plus 20°C to -20°C.
Researchers also tested the corrosion of the fibres by placing the fibre-reinforced concrete into a basin of salty water for several months and exposing it to wet-dry cycles. Corrosion normally leads to an expansion of the steel fibres on the surface – however, the expansion was not high enough to crack the concrete.
Technicians used a bending experiment to test how well the material coped with the exposure to extreme temperatures and moisture, as well as one million load cycles.
The experiments revealed that the new concrete can be highly durable, especially when a relatively modest amount of fibres is used.
Large-scale accelerated load testing of a circular concrete pavement three metres wide and 18 metres in diameter was also undertaken by Romanian experts working on the project, using a standard single axle load of 11.5 tonnes. After 1.5 million cycles the pavement was still performing well, indicating excellent performance even after the equivalent of 30 years of traffic.
Application
The concept of the EcoLanes project has been validated by constructing demonstration pavements in four different environments (the UK, Romania, Cyprus and Turkey).
Professor Kypros Pilakoutas of the University of Sheffield’s department of civil and structural engineering said: “The new material will provide a better infrastructure: fewer potholes, less maintenance and therefore less impact on the traffic. When the material is disused, it can be removed, crushed and recycled for a new pavement.”