  The generation of stress in a pore due to salt crystallization is generally
analysed as a compressive stress generation mechanism using the concept of
crystallization pressure. We report on a completely different stress generation
mechanism. In contrast with the classical picture where the crystal pushes the
pore wall, the crystal growth leads to the generation of a local tensile
stress. This tensile stress occurs next to a region where a compressive stress
is generated, thus inducing also shear stresses. The tensile stress generation
is attributed to capillary effects in the thin film confined between the
crystal and the pore wall. These findings are obtained from direct optical
observations in model pores where the tensile stress generation results in the
collapse of the pore region located between the crystal and the pore dead-end.
The experiments also reveal other interesting phenomena, such as the hyperslow
drying in PDMS channels or the asymmetrical growth of the crystal during the
collapse.
