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

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.