Decay of calcareous building stone under the combined action of thermoclastism and cryoclastism: A laboratory simulation

摘要

This paper aims at illustrating the driving forces of thermoclastism and cryoclastism in calcareous building stone and their effects on fabric and technical properties. An artificial accelerated ageing test was carried out on a soft and porous calcarenite, which is exploited in Apulia (southern Italy) and historically used in the local architecture and manufacture as building and carving stone. The ageing was calibrated over the typical climatic characteristics of the region, attempting to simulate seasonal climatic changes. In details, quarry samples were subjected to temperature cycles from 60 to -5 ℃, in a climatic chamber with a maximum relative humidity of 60%. During the test, the modifications in fabric were observed via SEM, whereas the changes in technical properties were analyzed through the direct or indirect measurement of: density, porosity, residual strains, p-wave velocity, compressive strength and Young's modulus. The results give clues about the durability of soft calcareous stone opposed to thermo-hygrometric stresses and, indirectly, to natural weathering driven by climate variables. Moreover, a method is suggested for evaluating the resistance of stone to freezing-thawing decay, combining its porosimetric distribution with the environmental conditions of weathering. Finally, this paper globally adds new information about a material of significant cultural interest, which has been studied only recently in archaeometry.