Thermal behaviour of unloaded concrete tunnel lining through an innovative large-scale tunnel fire experimental testing setup

•New proposed experimental testing setup had produced actual tunnel fire temperature.•Thermal behavior of new concrete tunnel lining materials could be determined.•Large scale fire test producing peak temperature over 1000 °C at lower cost.•New materials shows low temperatures at all cover depths.•Concrete tunnel lining for current construction had spalled severely. A full-scale tunnel fire test requires extensive preparation of the fire source and an empirical design setup of the tunnel to reach 1200 °C of tunnel fire temperature. This paper shows comprehensive experimental research on the method of designing a large scale fire test setup for new unloaded concrete tunnel segments. The thermal and spalling behaviour of fire-resistant Patent- MY-163281 composition concrete (PMC) tunnel lining segments are compared to those of a current construction project coded SPC. The tests were conducted to follow the RABT time–temperature curve. Unloaded tunnel segments were considered to minimise the effects of mechanical loading on the spalling and failure behaviour. The results show that the test setup could replicate the RABT time–temperature curve with a nominal difference. The temperatures decreased gradually, with the increasing depth of concrete cover from the surface exposed to fire, with the PMC segments less than SPC’s. The PMC segments showed good concrete spalling resistance behaviour, but the SPC segments were severely spalled. The PMC tunnel lining showed better performance under tunnel fire compared to SPC lining with similar design strength.