Deformation of fired clay material during rapid freezing due to supercooling

To better understand the mechanisms of the deformation of fired clay materials due to frost actions, we investigated the effects of rapid freezing due to supercooling on the deformation through both experimental and numerical approaches. We conducted a freeze–thaw experiment to measure the strain evolution of the material during freezing and thawing. Subsequently, we developed a coupled hygrothermal and mechanical model of the freezing and thawing processes including supercooling, and conducted numerical simulations corresponding to the freeze–thaw experiment. The model was based on the theory of poromechanics. The results of the freeze-thaw experiment revealed that the supercooling effects were small in fired clay materials compared to cement-based materials examined in literature, and the material expanded significantly associated with subsequent freezing after the rapid freezing due to the supercooling stopped. Based on the results of the experiments and numerical simulations, the equilibrium freezing temperature and water movement toward the material surfaces enhanced by relatively large moisture permeability restrict pressure development in the material even though the freezing of the supercooled water in the material was considerably rapid. The results of the numerical simulations also showed that the effect of the supercooling can be much more significant if a material had a low moisture permeability.