High temperature effects on the properties of limestones: post-fire diagnostics and material's durability

The research aims at investigating the temperature dependency of important properties of construction limestones, in the temperature range that could be reached during fires (200-800 degrees C). Limestones, through their different species and geographical origins, show a great variability in basic properties. The presented data will be useful to the post-fire recovery design of stonework buildings, by supporting the judgement on the perspects of durability based on the post-fire state of stones. The research features six varieties of construction limestones from different zones of France. The tests-colorimetry, ultrasonic P-wave velocity, total porosity, mercury intrusion porosimetry (MIP), scanning electron microscope (SEM) observations, capillary water absorption-are performed after high temperature exposure in a controlled furnace oven. The samples and heating conditions are designed to attain a uniform maximum temperature inside the samples. Nondestructive investigation techniques have a great potential usefulness in the perspect of post-fire investigations; on the other hand, the changes in the porous network, porosity and capillarity-investigated in laboratory-are direct indicators of post-fire materials' decay. The individuated temperature-property relationships of the single stone species, as well as correlations between P-wave velocity to porosity and compressive strength, are generally reliable. Finally, the detrimental effect of post-cooling rehydration has been observed through the kinetics of deterioration for all the investigated varieties of limestone. The results demonstrate the need of integrating non-destructive techniques to laboratory tests for cost-effective diagnostics on fire-damaged stonework buildings.