Causes and mechanism of concrete spalling under high temperature caused by fire

The review of the papers concerning the concrete spalling due to fire exposure are showing two causes: thermo-mechanical and moisture - thermal. Concrete spalling takes place in the case of high strength i.e. HPC, but is not encountered for low grade concrete, which have high porosity. The addition of polypropylene fibres not always can avoid its occurrence. The observation of concrete damages allowed to distinguish four forms of spalling: 1) spalling of aggregate, 2) surface spalling, 3) explosive spalling, 4) spalling of element corners. After fire the fifth forms is known as surface exfoliation.