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Experimental Evaluation of Tiled Finishes and Bonded Fire Resistive Coatings for Normal Weight Concrete Tunnel Liners under High Intensity Thermal Exposure
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2022-09-01
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[PDF-3.30 MB]
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Alternative Title:Fire Resistance of Tunnel Surfaces [Title from Cover]
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Edition:Final Report
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Abstract:This experimental program examines the relative fire resistance offered by the following bonded coatings for normal weight concrete tunnel liners: ceramic tiling on mortar, spray-applied fire resistive material (SFRM), and intumescent paint (IP). Sixteen panel specimens (150 mm [6 in.] thick, 457 mm [18 in.] wide, and 610 mm [24 in.] tall) were subjected to single-sided heating using a gas-fired radiant panel, which can apply heat flux of similar intensity as a hydrocarbon fuel fire. All specimens were cast from a single batch of normal weight concrete (with compressive strength of 39.8 MPa [5769 psi]) and included a single curtain of steel reinforcing bars with 38.1 mm (1.5 in.) of concrete cover to the heated face. All specimens were vertically loaded to a service level of compressive uniaxial stress (i.e. at 13-18% of ambient compressive strength), which remained relatively consistent during each test. Four bare concrete panel specimens were tested as a control group, and a ceramic tile finish was installed on six specimens in accordance with a state department of transportation specification. The remaining six specimens were coated with fire resistive material (three with SFRM and three with IP) at thicknesses corresponding to a 1-hour fire resistance rating per manufacturer specifications. Thermally-induced explosive concrete spalling was observed in 3 of 4 control specimens, in 4 of 6 tiled specimens, and none of the six SFRM/IP coated specimens. When conventional installation methods are used, the tiled finishes did not provide reliable, substantive fire resistance relative to that provided by the SFRM or IP fire protection materials. Temperature time histories through the outer 25-mm thickness of the heated concrete were recorded and are used to evaluate the relative fire resistive capabilities of each surface finish comparisons. Heat-induced damage depths are examined, and post-fire removal of the surface finishes is demonstrated.
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