Pre- and post-fire audits

Pre- and post-fire verifications are aimed at assessing the state of degradation of structures subjected to thermal loading. Nondestructive testing and site investigations determine the extent of deterioration suffered during the fire and propose a more accurate result in the presence of an ignited zone-that is, one damaged by thermal loading-and an unimpaired one, since a set of tests can be performed on healthy elements and compared with tests on elements between the zone of propagation and the zone of ignition. They fall into this typology:

• Sclerometric tests: establish how the rebound of a mass decreases as deterioration increases. They allow identification of percent degradation and give an indication of surface characteristics
• Ultrasonic tests: measure how the ultrasonic velocity in a healthy element hypothetically decreases in elements subjected to thermal loading. They can be by transparency, performed with two probes applied on opposite faces of the structural element, or homeosurface, when the transmitting and receiving probes are placed on the same side
• Visual investigation of artifacts: allows considerations to be made about the temperatures reached by the structure by observing the color assumed by the concrete and its surface appearance. Experience in this area is decisive in capturing some important clues within the structural element and in the area’s surroundings