A massive and targeted investment is currently required for the rehabilitation and extension of the European road infrastructure. The attainment of these objectives can be facilitated if the construction and maintenance costs, as well as the production lead-times, of the surface infrastructure are minimised.
The main element of road transport infrastructure is the pavement, which can be either asphalt or concrete. With increasing oil prices the future of asphalt pavements on deep foundations is less certain, due to cost as well as to political and environmental concerns, whereas concrete pavements appear to be more cost-effective than asphalt pavements, as they can reduce the foundation layers and decrease or eliminate the asphalt topping.
However, to provide a truly sustainable solution for concrete pavements, it is necessary to reduce the energy consumption during the production of concrete pavement. The main energy component of concrete pavements (from extraction of raw material through to the placement of the pavement) is the energy used for the manufacture of cement and steel reinforcement. The use of recycled materials appears to be a promising solution for reducing energy consumption.
EcoLanes' main objectives were to develop, test and validate steel fibre reinforced concrete (SFRC) pavements that will contribute towards the strategic objectives of the thematic priority area of sustainable surface transport.
EcoLanes aimed to use roller-compaction techniques (based on existing asphalt laying equipment) as well as recycled materials to reduce construction costs in the range of 10-20 %, construction time by 15 % and energy consumption by up to 40 %.
EcoLanes aimed to integrate simplicity and innovation to ensure the timely and cost-effective implementation of its findings into the construction and maintenance of surface transport. The main scientific and technological objectives were to develop:
- Techniques and equipment for post-processing steel fibres produced from post-consumer tyres, to arrive at fibres suitable for incorporation in concrete.
- Techniques and equipment for dispersing the fibres into concrete (both wet and dry mixes).
- Slip forming and roller-compaction techniques for SFRC similar to those used for asphalt laying.
- SFRC mixes suitable for slip forming and roller compaction.
- Models for the design of long lasting rigid pavements (LLRP) made with SFRC.
- Life cycle tools to determine cost, energy efficiency, and environmental impact of the new infrastructure.
- Full-scale demonstration projects in Cyprus, UK, Romania and Turkey
The project comprised nine work packages (WPs): four RTD, three for demonstration, one for dissemination and one for management.
The fibre cleaning and sorting techniques, developed during the first and second reporting period, were optimised to increase the yield of useful recycled steel tyre-cord fibres. WP1 could produce (to the project specification) up to 500 kg of recycled steel tyre-cord fibres per day. Parametric studies were undertaken to assess the effect of key parameters on the fresh and hardened properties of dry SFRC. Experimental results indicated that the flexural behaviour of dry SFRC mixes, made with recycled concrete aggregates, is equivalent to the one obtained from SFRC mixes made with natural aggregates. Experimental results indicate that dry SFRC mixes are more susceptible to corrosion and freeze-thaw than wet SFRC mixes.
The trial SFRC pavement, constructed and instrumented at the ALT LIRA facility, was tested under accelerated load testing; by the end of the third reporting period, 1,5 million load cycles were accomplished. Results showed that there was no failure in any of the sectors, showing that (over a design life of 30 years) the proposed roads would survive at least 20,5 million-single-axis of traffic. In addition, extensive analytical and numerical (elastic and inelastic finite element) analyses of plain-concrete and SFRC pavements were undertaken to develop appropriate design tools and failure criteria for wet and dry SFRC pavements. Existing design methods for concrete pavements were examined and a design framework and software were developed for LLRPs made with wet and dry SFRC.
Guidelines were prepared for the production of pavements made with dry SFRC. Methodologies were also developed / refined for the life cycle assessment (LCA) of the environmental impact and cost of the LLRP and data was collected for the LCA of the demonstration pavements, constructed during the third reporting period. On the demonstration side, activities included design, construction, and monitoring of the four demonstration pavements.
A number of results were produced from the work of the EcoLanes project.
- The project developed small to medium scale industrial processes and machinery for sorting the steel tyre-cord fibres.
- The project developed SFRC mixtures, which use materials with low energy requirements.
- Analysis and design software were also developed for the concept of LLRP.
- Methodologies were also developed for the LCA of LLRPs made with wet and dry SFRC.
These results should:
- provide a sustainable market for the steel fibres recycled from post consumer tyres and, thus, encourage the material recovery of large amounts of tyres,
- open the way for the construction of LLRP, which are more economic and environmentally friendly.