The subject of the article is to inform the experts about results of a set of fire resistance tests of light concretes designed for traffic and tunnel structures. In addition to commonly used recipe C 30/37 FX4, corresponding version of light concrete class LC 35/38/XF 4 was tested. One of the goals of the tests was verification of behaviour of “road” (XF4) concretes under the most demanding conditions of fire, especially in road tunnels. In addition to standard curve, the hydrocarbon and Eureka curves were used for the fire tests. The loading curves differ from normally used standard curve especially in the temperature rise speed (temperatures over 1,000°C are reached within a couple of minutes). In this case, real concrete moisture and possibility to remove water steams from a component are substantially important for the fire safety (integrity).