Contribution of Concrete Pavements to the Safety of Tunnels in Case of Fire

A number of tunnel fires in Europe have demonstrated the need for appropriate choice of materials for tunnel construction to ensure high safety and reliable availability to traffic. In case of fire, an incombustible and non-toxic road pavement, as it is a concrete one, contributes to the safety of people (users and rescue teams) and protects both the tunnel equipment and its structure. In this paper, the results of different fire tests on the behaviour of asphalt and concrete used for pavements performed in several countries are analyzed. It has been found that asphalt has a high calorific value, shortly igniting after being heated and emitting toxic gases. In addition, asphalt concrete loses its mechanical characteristics (after ignition, only aggregates are still present but no longer bound by asphalt). In comparison, concrete is incombustible, does not release fumes, does not change shape when submitted to high temperature and keeps a large part of its mechanical characteristics. Spalling phenomena are restricted to concretes that are very uncommon in pavements. Therefore it can be concluded that concrete pavements can largely contribute to the safety of tunnels in case of fire in comparison with other paving alternatives.