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This work faces the problem of fire resistance and temperature penetration depth in reinforced concrete under construction subjected to fire. Indeed, the design approaches always neglect the fire-induced effects on the structures under construction. In current applications, a lot of information about working boundary conditions during fire, actual material parameters and geometrical details lacks. The paper presents an original approach for the case study of a vertical reinforced concrete element (a stack under construction of the new bridge “Viadotto Polcevera”, Genoa) subjected to a fire accident. Lacking information was retrieved and integrated following a multi-reference approach (numerical simulation, design and operational data, norms). The critical areas of the stack, identified by means of a simplified numerical model, were compared to samples of materials extracted from the construction site and tested in laboratory. Particular attention was given to the model sensitivity to data uncertainties about component geometry, material thermophysical properties and possible thermal effects due to the reinforcement bars extruding from the cast of concrete, acting like fins. The very good agreement between the model and experimental data allowed to identify the minimum volume of stack to be demolished and rebuilt with a significant saving in time and money.