Potential thermal expansion of calcitic and dolomitic marbles from Andalusia (Spain)

Marble has historically been used as an ornamental stone because of its aesthetic appeal, ease of polishing and ex;cellent physical properties. One of the main factors affecting the durability of marbles is their thermal behaviour. Although marble is used extensively in Spain as a building and decorative material, little research has been done into its thermal behaviour. In this work, the textural and microstructural properties of seven calcitic and dolomitic marbles from Andalusia (southern Spain) were characterized to assess how these properties affect their thermal response. Rock fabric properties (grain morphology, boundaries and micro-crack populations) were studied by polarized microscopy and lattice preferred orientation using X-ray texture goniometry. Elastic properties were measured by ultrasound, thermal properties were determined by a six-rod dilatometer (thermal expansion) and the opening of micro-cracks was observed using environmental scanning electron microscopy. For each marble, thermal coefficients of calcite and dolomite crystals were calculated using thermo-X-ray diffraction, a novel application to characterize historic marbles. The results show that marble thermal expansion coefficients are related to preferred crystallographic orientation, which can help to identify the directions along which decay occurs. The results also show for the first time that the thermal expansion coefficient of the main components of marble, i.e. calcite and dolomite, is specific to each marble, and plays a key role in their different thermal behaviours. Thermal properties also depend on mineral composition, the existence of micro-cracks and hydric properties.