Petrophysical and mechanical properties of Piromafo, a stone variety of the Pietra Leccese Fm. (Apulia, southern Italy)

Many historic buildings and monuments in Salento (Apulia, southern Italy) were built from locally quarried Miocene calcarenites due to their workability, aesthetic appeal and availability. Mazzara, Dura, Bianca, Dolce, Gagginara, Piromafo, Cucuzzara, Saponara and Nera are the traditional names of the stone varieties belonging to the Pietra Leccese Fm. (Late Burdigalian-early Messinian). These are mainly white-yellowish fine-grained calcarenites, homogeneous and porous with a wackestone depositional texture, composed of calcareous microfossils, such as Foraminifera, and bioclasts of bivalves, ostracods, echinoderms together with pellets and intraclasts. The durability of these materials, defined as the property of natural building stone to resist the weathering agents in the course of time and conserve its appearance and characteristics of strength, is however not the same in the different varieties, being controlled strongly by depositional fabric and diagenetic processes. The purpose of this work is to present a comprehensive review of the main petrophysical and mechanical properties of Piromafo, a glauconitic facies greenish-brown in colour, well-known as a refractory and heat insulation material which clearly differs from the other varieties not only for aesthetic appearances. Rock fabric inspection was performed by means of transmitted light on standard thin-sections using optical polarizing microscopy. Specific gravity, density, porosity, water absorption and degree of saturation were obtained following the test procedure described in the ISRM and ASTM standards. Pore size distribution was carried out by mercury intrusion porosimetry technique and image analysis performed on photomicrographs applying the methods of quantitative stereology. Computer analysis of digital images was applied to determine also the grain size distributions. Water permeability tests were conducted on cylindrical rock samples using the constant head and falling head methods and the constant pressure technique. The thermal parameters were determined with the experimental ‘cut carrot’ method, first in the dry state then in the saturated state and for different water contents. Uniaxial compressive strength and indirect tensile strength were correlated in different physical states