Post-heating mechanical behaviour and pore network evolution of limestones: Influence of petrographic properties

This article investigates the high-temperature behaviour of thirteen types of limestone used in masonry, focusing on their petrographic properties. Thermochemical and thermomechanical characteristics were evaluated through thermogravimetric analysis and linear measurements up to 1050 °C. Both non-destructive tests (P-wave velocity and dynamic modulus of elasticity) and destructive tests (uniaxial compression, three-point bending, and Brazilian splitting) were conducted on specimens of varying geometries. These specimens underwent four distinct heating-cooling cycles at 200, 400, 600, and 800 °C. The pore network was assessed using water-accessible porosity (under vacuum), capillary water absorption (up to 600 °C), and mercury intrusion porosimetry at 750 °C. Limestone undergoes a significant reduction in its physical and mechanical properties at 600 °C, primarily due to the differential thermal expansion of its constituent minerals. At 800 °C, limestone loses even more of its mechanical properties due to calcite contraction during decarbonatization. Furthermore, limestone thermal sensitivity is also influenced by grain size and by the proportion of fine pores (<10 μm), which respectively govern the magnitude of internal thermal stresses and the ability of the bonding phase to accommodate thermal expansion. • The high-temperature behaviour of thirteen limestones is investigated. • Mechanical and physical properties significantly decrease at 600 °C. • Thermal cracks connect inaccessible pores and increase capillary water absorption. • The fine-pore fraction (<10 μm) affects the thermal sensitivity of limestones.