Evaluation of post-thermal shock effects in Carrara marble and Santa Caterina di Pittinuri limestone

Abstract

This article describes the effect of thermal shock on the petrographic and petrophysical properties of two Italian carbonate building stones: Carrara marble from the Apuan Alps in Tuscany and ‘Santa Caterina di Pittinuri’ limestone, from Sardinia.The samples were exposed to two thermal cycles to study surface and inner stone decay. The changes induced by thermal shock were assessed in terms of microstructural alterations measured with ultrasonic pulse velocity, Hg intrusion porosimetry, polarised light and fluorescent optical microscopy and micro-computed tomography. Variations in surface microhardness were also measured. The marble developed a dense network of pseudo-parallel intercrystalline, intracrystalline and transcrystalline microcracks, whereas the limestone underwent no significant microcracking. Those findings attested to lower resistance to thermal shock in marble calcite crystals than in limestone sparite cement and micrite. Thermal shock, an accelerated weathering technique, simulates possible stone exposure to high temperatures over long periods of time. Here the method was used to evaluate and compare microcrack distribution and orientation in the two heritage stones studied.