Monitoring of Deformations Induced by Crystal Growth of Salts in Porous Systems Using Microscopic Speckle Pattern Interferometry

Electronic speckle pattern interferometry (ESPI) has been used to monitor microdeformations and surface microstructure changes produced by crystallization or hydration pressure of magnesium sulfate in a porous material. Samples of fritted glass were chosen as a standard porous substrate because of its mean grain size, its porosity distribution, and its negligible humidity expansion. The glass samples, soaked with salt solution, were exposed to changes in relative humidity of the surrounding air. The full-field ESPI measurements were combined with cryogenic SEM visualizations. Results from these investigations were partly riot expected theoretically and give new insight in the underlying salt phase transition processes.