Effect of thermal stress, condensation and freezing-thawing action on the degradation of stones on the Castle of Chambord, France

This work consists in estimating the role of climatic conditions in the degradation of two French limestones, tuffeau and Richemont stone, used in the construction and the restoration of the Castle of Chambord, the largest castle in the Loire Valley, France. Meteorological data, air temperature, air relative humidity and rainfall were statistically analysed in combination with stone data from thermal-humidity sensors inserted into the walls. The climatic conditions of the surrounding area were described to assess their role in enhancing the degradation of the stones through three weathering processes: thermal stress, condensation and freezing-thawing. The damage risks due to the weathering processes were taken into account not only through the bulk effects on the stone surfaces, but also their effects were extended to investigate the damage that occurs within the porous structure of the stone. Field observations showed that the main patterns of degradation affecting the stones of the castle are biological colonization and stone detachment in the form of stone spalling and exfoliation. The results of the analysis show that there is no risk of damage to the stones due to thermal stress. Moreover, the two stones experience similar overall trends against freezing-thawing processes. Finally, this study clearly highlights the important role of condensation in the degradation of the stones of the castle.