Making inroads into better transportation surfaces Rising oil prices have been accompanied by an increase in the cost of the traditional asphalt road. A European project has researched the use of recycled and low-energy materials for an eco alternative cement-based road surface. Industrial Technologies © Shutterstock Concrete as a road surface is exceedingly strong, long lasting, safe, quiet and potentially aesthetically superior to asphalt – it can even be coloured, a selling point in urban areas as a design feature. However, because cement is generally a more expensive alternative, the EU-funded project 'Economical and sustainable pavement infrastructure for surface transport' (Ecolanes) investigated replacement processes and materials to lower the price. Ecolanes' economic objectives were ambitious. Fulfilling them would mean that construction costs could be cut by up to 20 %, construction time by 15 % and, importantly, energy consumption by up to 40 %. Successfully developing, testing and validating lower cost steel fibre reinforced concrete (SFRC) pavements promises to contribute to the priority area of sustainable surface transport. Models were developed with new analysis and design software for the construction of long-lasting rigid pavements (LLRPs) made with SFRC. Cuts were achieved both in construction costs and time by using a mixture of recycled materials and new manufacturing techniques. Concrete bases require steel mesh reinforcement and old tyre fibres provided a low-cost recycled alternative. Recycled aggregates, pulverised fuel ash (PFA) – a by-product of coal from power stations – and low-energy cements also contributed to savings on materials. As for the processes, fibre cleaning and sorting techniques were optimised to increase the yield of the useful recycled steel tyre cord fibres. The team also compared properties of recycled aggregates against the natural more expensive version. Interestingly, flexural behaviour of dry SFRC mixes was equal in performance to mixes made from natural aggregates. The scientists constructed a trial pavement for accelerated load testing. After 1.5 million load cycles, put into real terms, results showed that over a design life of some 30 years, the road would survive at least 20.5 million single axis vehicles The Ecolanes project provided a sustainable market for the recycling of worn out tyres. The main objective was also achieved creating a firm basis for the construction of more economic and environmentally friendly LLRPs.
