Durability of ordinary concrete after heating at high temperature

After a fire, the concrete structures are usually repaired. This repair requires a diagnosis so as to know the areas to be preserved and the areas to be demolished. In this analysis, the loadbearing capacity is often the primary endpoint. However, the question of the durability of the structure must also be asked. This experimental study aims to assess the durability of one ordinary concretes after heating at high temperature (up to 600°C). The ordinary concrete have a compressive strength at 28 days of about 40 MPa. Five characteristics were determined for each target temperature (20, 120, 250, 400 and 600°C): the compressive strength, the water porosity, the nitrogen permeability, the pore distribution by mercury porosimetry and the absorption coefficient. The evolution of the characteristics with temperature are evaluated. Their evolution with compressive strength is analysed and durability index are detailed. The results show that some correlation exist between the characteristics in particular between nitrogen permeability and water porosity. The evolution of durability index shows that the compressive strength is not sufficient to evaluate the durability of concrete after heating.