Fire damage - concrete

In case of natural/normal fires at temperatures up to about 1.000 °C unreinforced normal concrete has a sound resistance to heat (no deformations) as well as flame-retardant properties (non combustible, consequently no smoke emission, no release of toxic substances, no flame transmission). Fires producing extremely high temperatures and/or burning plastics (particularly PVC - hydrochloric acid HCI is produced) may cause (irreparable) structural damages to reinforced concrete (deformation of the reinforcement). The deformations may cause cracks, concrete spalling, and in extreme cases the loss of the load bearing capacity. Due to crack formation and concrete spalling the reinforcement is not protected any more so that the hydrochloric acid is able to attack freely.