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Innovative Reuse of All Tyre Components in Concrete

Final Report Summary - ANAGENNISI (Innovative Reuse of All Tyre Components in Concrete)

Executive Summary:
Around one billion tyres are discarded each year, with post-consumer tyre arisings for EU countries alone exceeding 3M tonnes per year. Tyres comprise roughly 80% rubber, 15% steel wire and 5% textile reinforcement by mass. Nearly 50% of all recycled tyres/components end up as fuel, in low grade applications or in landfill. Less than 25% of the energy required to produce rubber is recovered by incineration. All tyre constituents (rubber, high strength steel cord and wire, high strength textile reinforcement) are high quality materials and the aim of Anagennisi was to recycle them as reinforcement in structural concrete applications. For that purpose, all materials were cleaned, sorted and classified using standardised or novel techniques developed during the project.
Rubber particles were used to substitute conventional aggregates in plain concrete (up to 60% total aggregate replacement) which results in severe loss in compressive strength, but increase in lateral strain. To regain the compressive strength, Rubberised Concrete (RuC) was confined with Aramid FRP jackets and the results showed compressive strengths up to 90 MPa and, more significantly, axial deformations up to 6% (normal concrete 0.2%). This high deformability can be utilised in seismic and other applications. The seismic performance of RC medium and large scale piers was assessed using AFRP confined RuC (CRuC) in targeted regions of the piers. The results showed that AFRP CRuC improved the energy dissipation up to 50% and increased ductility up to 25% - (compared to RuC). Successful shake table tests were also conducted on buildings with CRuC elements and base isolation columns. Based on material tests, numerical models were developed to predict the short-term structural behaviour as well as the free shrinkage and creep deformations of RuC and CRuC.
Recycled Tyre Steel Fibres (RTSF) can partially replace manufactured steel fibres to increase the flexural strength of concrete – saving on virgin materials and reducing energy input requirements by 97%. RTSF fibres are shorter and much thinner than manufactured steel fibres, helping to control cracks at the micro and meso level. Extensive tests on the flexural behaviour of RTSF reinforced concrete showed that fibre blends (with manufactured steel fibres) result in optimum mechanical characteristics, outperforming each fibre type on its own. Steel fibres do not have a significant impact on free shrinkage, but help prevent or control cracking under restrained conditions. No cracking was observed after a period of 9 months for restrained specimens with 50% restraint.
Recycled Tyre Polymer Fibres (RTPF) were easy to integrate in mortar and concrete easy using novel integration methods. The results show that they can decrease initial plastic and autogenous shrinkage and can potentially substitute virgin polypropylene fibres. RTPF reinforced concrete showed remarkable resistance to spalling when subjected to elevated temperatures, confirming the potential of these fibres for fire-induced concrete spalling mitigation.
Several demonstration projects were undertaken in five European countries to convince contractors and infrastructure owners of the benefits of the examined tyre by-products. These projects included slabs on grade, tunnel linings, precast concrete elements (rubberised poles and railway sleepers) and a repair screed application. Design recommendations and examples were developed for all three tyre constituents. Work was undertaken on the environmental (LCA) and cost (LCCA) life cycle assessment of the aforementioned demonstration projects to demonstrate the potential benefits.

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Professor Kypros Pilakoutas
Tel.: +44 114 22 25065