A new perspective on hydric dynamics and damage susceptibility in natural stones: Insights from the thermal impact on carbonate lithologies

Thermal exposure can substantially alter the hydric behaviour of carbonate stones, with direct implications for damage susceptibility and post-fire durability. This study provides a new perspective on hydric dynamics by analysing not only how water is absorbed, but also how it is retained and released after thermal exposure. Thirteen Portuguese carbonate lithologies (limestones, marbles, a breccia, and a travertine) were heated to 300 °C and 600 °C, and their hydric response was characterised through open porosity, bulk density, capillary uptake coefficients, drying rates, and total water absorption. Pore-size distribution analysis was used to assess the role of porosity and its spatial organisation in controlling these processes. Hydric susceptibility was further evaluated using time-based metrics describing the progression of both water intake and water release within each stone. Results reveal clear lithology-dependent responses, showing that thermal damage modifies pore geometry and connectivity in ways that distinctly affect both absorption and evaporation pathways. These findings deepen our understanding of thermally induced hydric behaviour and support more robust evaluations of damage susceptibility in fire-affected carbonate stones.