Case studies

North Downs , segments at a purpose built factory The 3.2 km Tunnel forms in Ridham Docks. part of the Channel Tunnel Rail Link running from Folkestone, Kent to De Westerschelde Tunnel, the St. Pancras in . The primary Netherlands tunnel lining was made up of sprayed The client Maafroute BV instructed concrete. 1 kg of Ignis PP monofilament the precast contractors to add 1 kg fibres were added to the 60 N/mm2 of Ignis to the C40 concrete. The fibre concrete secondary lining. The lining was included in the concrete sections was constructed insitu, forming a forming the security exits, safety sacrificial layer. barriers and connection .

T5, Heathrow Airport Dublin Port Tunnel, Ireland Ignis has been added to Grade C60 This 4 lane underground highway is concrete on various contracts within this designed to take heavy vehicle traffic prestigious project. The Ignis enhanced off the streets of Dublin. A 275 mm concrete has been used on site in thick lining over the tunnels arch is a sprayed concrete applications and it non-load bearing sacrificial concrete has also been added to precast ring containing 1-2 kg of Ignis.

IGNIS® Monofilament Fibre PASSIVE FIRE PROTECTION

North Downs Tunnel, Kent T5, Heathrow Airport, London

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Westerschelde Tunnel, the Netherlands Dublin Port Tunnel, Ireland

Ignis® Monofilament Fibres Increasing the safety of people and structures BRE sample without Ignis subjected to European BRE sample with Ignis subjected to European Hydrocarbon Curve showing severe spalling Hydrocarbon Curve showing no spalling Concrete is the most widely used construction material in tunnels around the globe. Due to several tunnel fires in Europe and the increased threat of terrorism, public attention has been focused on the performance of concrete structures both above Testing and below the ground. Passive fire protection that safeguards structural integrity in the event of a fire is of utmost importance for the safety of tunnels. Without such Proven perfomance The sample containing no fibre was Extensive testing at independent severely damaged, whereas the panel protection, heavy objects and/or hot spalled concrete can pose a serious threat. laboratories such as TNO (NL) with 3 kg of Ignis fibre showed virtually and BRE (UK) has proven that Ignis no damage at all. significantly enhances the fire Avoiding explosive spalling Fig. 1 / Mechanism of concrete spalling rating of concrete structures. BRE Although concrete is non-combustible Samples containing granite aggregates and has low thermal diffusivity, it does Causes of concrete spalling Prevention of concrete spalling Technical details TNO and Ignis monofilament polypropylene experience explosive spalling from the with polypropylene fibres • Fibre length: 6 mm Back in 1999 TNO proved that the use fibres were exposed to a severe build up of pore pressure and internal • Equivalent diameter: 18 μm of monofilament fibre gave the best hydrocarbon fire curve that rises 1 High quality dense concrete means 1 The fibres will melt at 160° C tensile stresses during a fire. Ignis that moisture can’t escape quickly • Shape: Monofilament results when compared to fibrillated rapidly to 800 °C in three minutes and enough. At this point the voids Fig. 3 / RWS fire curve vs. alternative tests 3 polypropylene monofilament fibres, become saturated. • Specific gravity: 0,95 kg/dm fibres in avoiding explosive spalling. peaks at 1100 °C. The samples were when mixed in concrete, increase • Fibre count: 718 mio. A year later, the institute used the subject to compressive forces during 1350 1260 its permeability during heating thus RWS Fire Curve on a number of the test; equivalent to the design 1200 1200 reducing pore pressure and avoiding Functions concrete samples that contained loadings predicted in the tunnel lining 1080 the risk of spalling. Heat • Passive fire protection 1.2 and 3 kg/m3 of Ignis monofilament of the Channel Tunnel Rail Link project. 1078 925 1029 source • Crack control polypropylene fibre. The samples The plain control sample suffered 867 Temperature (C°) Moisture ecaping from 2 822 Breadth of end-uses heat source were loaded to 6.5 N/mm . The RWS extensive explosive spalling up to a Ignis fibres are applied in a wide range Benefits Fire Curve models a severe hydro- depth of 120 mm. The sample containing 556 482 of applications. Examples include 2 Hot front quickly overtakes moist front. 2 When the temperature reaches 360° C, • Prevention of explosive spalling carbon fire and after just 10 minutes Ignis fibres showed no evidence of Moisture starts to vaporise and the fibres will disintegrate, creating sprayed linings, precast segments and increases pressure within concrete voids in the concrete. • Improved resistance to the temperature was 1200 °C. spalling after two hours of testing. pumped concrete behind slip formed pores. plastic shrinkage cracks The temperature was increased Even the mixes containing lightweight shuttering for: • Enhanced abrasion and again to 1350 °C resulting in the aggregate which totally disintegrated Time impact resistance samples being subject to extreme during the initial tests, showed no spalling RWS (NL) Hydrocarbon (EC) • Road and rail tunnels temperature conditions for two hours. when Ignis fibres were added. ZTV (D) Standard ISO or BS 476 • High rise buildings • Cable tunnels Fibres Concrete close to surface in • Bridges compression

• Underground/multi storey car parks 3 Crack and explosion 3 Vapour pressure is released • Refractory products through the newly formed voids. Explosive spalling is avoided. Fig. 2 / Ignis vs. alternative fibre

No. of Surface Spalling depth fibres/kg area fibres/kg Max Avg

Ignis 6 mm 718 Mio 245 m2 15 mm 6 mm

2 Release of vapour 32 μm (micron) 110 M io 133 m 60 mm 20 mm pressure monofilament fibre

Bridge Underground car park High rise building Road tunnel Rail tunnel