High temperature effects on the properties of a high porosity calcareous stone building material

Abstract

High temperatures affecting buildings during fires have a potential of impact on the material’s performance. A variety of thermal effects may take place on natural stones in historic buildings, and their investigation in laboratory simulations may be effective to support a reliable diagnosis of fire damage in order to select proper conservation measures. To this aim, this study reports on the high temperature effects on a highly porous calcareous stone. Analytical and microscopic techniques (X-Ray Diffractometry, Thermogravimetry and Differential Scanning Calorimetry, optical microscopy and SEM), were combined in a systematic investigation of chemical-mineralogical and microstructural modifications affecting the stone under increasing temperatures, up to 700 °C. Non-destructive ultrasonic velocity propagation (UPV) test and quantitative evaluations of colour changes and physical parameters relating to the stone microstructure were also performed. The overall findings highlight that thermal effects mainly compromised the aesthetic features of the investigated stone, through colour changes relating to chemical-mineralogical transitions. The damage to the stone microstructure due to thermal dilatations was limited, likely because of the high presence of pore spaces. Fissuring was observed microscopically, and also recorded through porosimetric changes and UPV decreases, but it led to negligible increases of both the open porosity and water uptake.

Keywords:

• Masonry fire damage
• porous limestone
• thermal heating
• chemical-mineralogical changes
• microstructure
• physical properties
• UPV test

Acknowledgements

This study was carried out in the framework of the activities promoted by a collaboration contract between CNR-ISPC and the Municipality of Tricase (Lecce).

The authors would like to thank Prof. Alfonso Maffezzoli for making available the SEM at the Dept. of Innovation Engineering of the Salento University (Lecce) and the technician Mr. Donato Cannoletta for the support in SEM analyses.

Disclosure statement

No potential conflict of interest was reported by the authors.