Concrete spalling due to fire: a technical day to better understand this phenomenon
Tunnel owners, design offices, testing laboratories and tunnel operators gathered in Bron on 13th November for a technical day on concrete spalling in fire conditions, organised by the CETU.
After a review of fire safety regulations in all modes of transport and fire resistance requirements, the functioning of a tunnel in the event of a fire and the phenomenon of spalling were explained.
For tunnels in operation, when a fire causes spalling on the concrete lining of the structure, the consequences are significant in terms of immediate post-fire safety and require diagnosis, repairs and closure to traffic for the duration of works. Feedback from tunnel owners who have experienced this type of incident in their tunnels (Eurotunnel, ATMB, APRR) has helped to highlight these issues.
Where fire resistance requirements mean that this phenomenon must be taken into account, it must be considered from the design stage of an underground structure, bearing in mind that fire resistance can vary depending on the type of concrete used. The Société des Grands Projets (SGP) has therefore reviewed the spalling tests carried out as part of the construction of the Grand Paris Express. These tests were the first to be carried out on fibre-reinforced concrete segments within the regulatory framework for guided transport and demonstrated the need to test certain precast concrete formulations.
The three laboratories approved by the French Home Office (CERIB, CSTB and Efectis) detailed the current methods used for spalling tests in the absence of a dedicated standard currently available on this specific subject. The work led by the CETU as part of a working group bringing together the three laboratories aims to standardise practices and improve the assessment of the resistance of concrete to spalling under fire conditions.
This technical day proved to be highly instructive and will contribute to the technical doctrine on the fire resistance of concrete, with a CETU publication on this subject to come!
CETU would like to thank all the speakers!