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Following several tunnel fires in Europe, design engineers have had their minds firmly focused on how to prevent the explosive spalling of concrete in tunnels. The phenomenon occurs when concrete is exposed to high temperatures such as those experienced during a hydrocarbon fire. The high quality dense concrete that is associated with tunneling projects means that in the event of a fire, moisture escaping from the heat source cannot escape quickly enough. Any voids that are present within the concrete soon become saturated.

This is where Adfil construction fibres come in: When mixed in concrete Ignis polypropylene fibres, specifically designed for the application in tunnelling, will increase permeability of the concrete during heating. They do this by melting, creating voids and reducing pore pressure, thus allowing steam to escape and reduce the risk of spalling. For many years now, Ignis micro synthetic fibres have been used in tunneling projects across Europe to reduce damage in the event of a fire. Examples include T5 at Heathrow Airport, the Westerschelde Tunnel (the Netherlands) as well as the Dublin Port Tunnel.


  • Reduced explosive spalling
  • Increased speed of construction
  • Reduced labour costs
  • Improved resistance to plastic shrinkage cracks

Would you like to discuss your next tunnel project? Our design and customer service teams are here to help.


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