Solids fracturing by crystallization pressure through metastability-driven pathways
Résumé
The salt damage provoked by crystallization pressure due to salt growth inside a porous material requires a certain supersaturation of the pore solution. The itineraries to build it are here revisited at the one pore scale, through experiments allowing direct observations of the multistep processes as well as the visualization of the damage itself.
We present phase transitions experiments within silica micro-capillaries filled with Na-SO4 aqueous solution submitted to: (i) drying by isothermal evaporation, (ii) temperature change, and (iii) the cavitation of a metastable capillary-type liquid.
We directly observed the multistep processes that drive salt damage due to in-pore crystal growth, until the container is fractured, for the first time to our knowledge. We thus demonstrate that supersaturation (linked to direct drying, temperature drop, or capillarity) allows the salt damage to happen as a brutal process. Interestingly, the newly-observed capillary mechanism, never described in the literature to our knowledge, can take place after a long latency period without any apparent immediate triggering cause.
Those findings magnify the versatility of the crystallization pressure that can occur in very contrasted situations. They also enforce the fact that this chemo-mechanical coupling is strongly pore-size dependent, with the third process that should predominate in cement and stones hosting nanoscale porosity prone to strong capillarity.
Origine : Fichiers produits par l'(les) auteur(s)