Effects of recycled steel and polymer fibres on explosive fire spalling of concrete

Modern high-performance concrete, increasingly used in tunnels and other important infrastructure, is susceptible to explosive fire-induced spalling. To prevent fire spalling, modern codes recommend the use of small quantities (e.g. 2 kg/m3 as recommended by the Eurocodes) of polypropylene fibres in the concrete mix. This paper presents an experimental study investigating, the effect of cleaned recycled fibres extracted from end-of-life tyres on the explosive fire-induced spalling of concrete. This paper presents 24 spalling tests, indicating that recycled tyre polymer fibres, at dosages equal to or larger than 2 kg/m3, might help prevent fire spalling. Recycled tyre steel fibres also show the potential of preventing fire spalling damage by keeping spalled concrete attached to the heated surface, thus protecting the main steel reinforcement. The use of these fibres might lead to safe and sustainable fire spalling mitigation solutions.