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 the effect of PP-fibers as well as of additives and the production process on transport properties of concrete under fire attack. Besides experimental investigations, finite-element analyses of heat and mass transport in heated concrete are conducted. The obtained temperature and gas-pressure results provide insight into the risk of spalling of concrete for varying amount of PP-fibers. Finally, a structural analysis tool is employed to investigate the structural performance of a real tunnel structure under different fire and spalling scenarios.