Sustainable Fire-Spalling-Resistant Concrete

Fire-induced spalling of concrete experienced by constructed facilities such as tunnels, buildings and bridges has been shown to cause catastrophic failure, and to lead to huge economic costs and potential loss of life. However, despite the consequences, fire-induced spalling remains one of the least well understood aspects of concrete behaviour. This project aims to develop an improved understanding of fire-induced spalling of modern high-performance concrete, and to find a sustainable spalling-mitigation solution by using fibres recovered from end-of-life tyres. To achieve this, X-Ray Computed Tomography (XRCT) will be used to detect the microstructural changes in concrete due to thermo-mechanical loading and to examine the underlying mechanics of spalling and the spalling-mitigation mechanism of polymer fibre in general and that of the Reused Tyre Polymer Fibre (RTPF) in particular (the latter offering major economic and sustainability benefits). Also, a state-of-the-art fire testing system will provide more controllable heating and hence more reliable and repeatable test results than provided by conventional furnace testing. The high-quality test results collected will form a database for use in this and future research projects. Numerical modelling will be performed, allowing key aspects of the experimentally observed behaviour to be simulated, and preparing the ground for the eventual development of a predictive spalling model. Preliminary design guidance for fire-spalling-resistant concrete with RTPF will also be developed, in order to expedite the uptake of this technology by practitioners.

WHO WILL BENEFIT AND HOW?

- Environment: Finding high-value uses for tyre polymer fibre will reduce the environmental impact of tyre manufacturing and that of concrete construction. The energy required to produce the reused polymer fibres is only about 1% of that required for the virgin fibres they replace. This will result in:

1. Reductions in greenhouse gas emissions from the production of polymer fibres to be used in concrete by 99% and 99.5% for CO2 and methane, respectively.

2. 100% reduction of dangerous substances, such as volatilized monomer (caprolactam) and oil vapors or mists irritant/corrosive, which are released during the incineration of tyre polymer fibre.

3. Polymer fibre reinforcement can result in fire-resistant concrete elements. Assuming that 63,000 tonnes of polymer fibre could be recovered from end-of-life tyres every year and used as reinforcement to replace the demand (which is higher: 75,000 tonnes of virgin polypropylene fibre), then a possible annual reduction can be achieved of up to 0.5 million tonnes of CO2 in the EU market, worth about £50 million per year.

- Society: This research will benefit society, not only by reducing CO2 emissions, but also by developing safer concrete (through a more fundamental understanding of spalling) and by improving the quality of life, health and safety of those who live close to and/or work in tyre recycling plants (tyre polymer fibre is highly flammable and is easily carried away by wind). It has been estimated that a total of eight new jobs will be created for every 1,000 tonnes/annum of reused-fibre manufacturing capacity. New job opportunities will also be created in engineering consultancies and construction companies.

- People: The research programme will train a highly skilled researcher. This will have a direct economic impact via the provision of a skilled worker for a beneficiary organisation.

- Tyre recyclers (e.g. project partner, Conica Ltd) and reused fibre producers (e.g. project partner, Twincon Ltd) are likely to be key economic beneficiaries. More details are given in the Pathways to Impact document.

- Tyre manufacturers will benefit from the reduction of the environmental impact of end-of-life tyres.

- End users:

1. Tunnel and building contractors using fibre reinforced concrete will have a more economical and environmentally friendly alternative to manufactured polypropylene and steel fibres, thus increasing their competitiveness.

2. Ready-mix (i.e. self-compacting and high-performance/high-strength concretes) and precast concrete suppliers may decide to offer RTPF concrete to guarantee fire resistance.

3. Infrastructure owners, local authorities and utility companies will all benefit from the increased choice of reinforcement solutions. This will promote innovation, sustainability and improvement of existing products while maintaining competitive prices.

4. Engineering consultancies (e.g. project partner, Ramboll) will benefit from a reliable, sustainable and economical spalling prevention solution and the related know-how, and hence enhance their competitiveness.

- Professional bodies: The Concrete Society, RILEM, ACI, fib, ETRA will benefit from high-quality data and a fresh approach to design using RTPF.

WHEN?

The industrial benefits will arise once the research findings lead to development of a new sustainable product. Experience from Reused Tyre Steel Fibre development suggests that this is likely to take around 5 to 10 years.

The academic and professional benefits will begin just after the project finishes, and when the research outputs are published. Initial guidance on mitigation of fire-induced concrete spalling will immediately benefit specialist practitioners in the field. Future work will include the further development of design guidelines; it is expected that it will take 5 to 10 years before these are accepted by relevant authorities.