Tunnel fires demonstrate how the load-bearing capacity of the structure is reduced by fire loading which eventually leads to collapse of the tunnel. In this work, different aspects of Concrete Subjected to Fire Loading are tackled. First, spalling of near-surface layers of heated concrete is investigated employing a high-speed camera. This allows identification of the main processes controlling spalling of concrete. In addition, the permeability obtained from experiments on concrete with or without polypropylene (PP) fibers is related to the pore structure of heated concrete. This highlights...