As a rule, concrete is a safe building material in a fire but it may sustain severe damage from both fire and extinguishing efforts. In addition to high temperatures, factors affecting concrete structures include rapid cooling by firewater, mechanical disassembly and demolition as well as a partial structural collapse.<\/p>\n\n\n\n
Fire-induced damage of concrete typically occurs as cracking, scaling, discoloration, deformations, and reinforcement damage. The damage usually spreads deeper quite slowly into the structure from the surface due to the poor thermal conductivity of concrete.<\/p>\n\n\n\n
The strength of concrete deteriorates permanently with increasing temperature and will not be restored when the structure cools down. The very first discoloration already indicates a clear loss of strength and at high temperatures, it is possible that the concrete only has a part of its strength left. Prestressed structures are especially challenging and may sustain severe damage without any visible indications on the concrete. For this reason, the assessment of fire damage calls for a comprehensive analysis, observations made at the scene of the fire, and often also laboratory tests.<\/p>\n\n\n\n
Repairs must be designed to restore the safety and functionality of the structure also in any future abnormal conditions.<\/p>\n\n\n\n