Dilatometrical behaviour of porous calcareous rock samples subjected to freeze-thaw cycles

Dilatometry can be used in geomorphology as an evaluation method for the behaviour of rocks during weathering by frost shattering and also for the role of unfrozen water migration during this process. It has already been demonstrated in other publications that calcareous rock cylinders undergoing humidification/drying cycles (no freezing) vary in length. These length changes are most significant when water enters or leaves the smallest pores in the rocks. By analogy, these observations allow us to interpret the curious dilatometrical behaviour of certain rock cylinders during freeze-thaw cycles as part of water migration. It is only when these samples are close to saturation and submitted to a relatively quick freeze that a large increase in volume is observed, as the majority of literature on the subject has advanced. For samples relatively far from the saturated state, volume can diminish during freezing. Furthermore, these variations in volume are anisotropic. This anisotropic behaviour of rocks during freezing is due to the migration of unfrozen water within the samples, a migration which is strongly influenced by the porosimetry of the rock, by its saturation coefficient and the freezing rate used, but also by slight experimental modifications. The distribution of the water measured within the frozen cylinders confirms the preceding interpretation.