High-temperature behaviour of various limestones at the block scale

The violent fires undergone by many cultural-heritage masonry buildings during their history are the starting point of this work, whose objective is to investigate the effect of high-temperature on building stones at the block scale. The effects of geometry and particularly of the thickness-to-side on the behaviour of square and rectangular limestone blocks subjected to high temperatures were studied. Six French limestones with compressive strengths ranging from 9.4 to 74.5 MPa and total porosity varying from 11 to 31% were selected for this study. The limestone blocks with different shapes and dimensions were subjected to unidirectional heating with a heating rate of 9 C/min. The results give information on the influence that the geometry and the size of the blocks have on the crack pattern and on the damage extent at high temperature. Among the various physical and mechanical properties of the stones, the tensile strength and the fracture toughness (i.e., the material's resistance to breaking or fracturing when subjected to stress), play a sizeable role in the thermal sensitivity of the stones, as the higher the toughness and the tensile strength, the lower the damage at high-temperature.