ION TRANSPORT AND CRYSTALLIZATION IN POROUS MATERIALS AS STUDIED BY MAGNETIC RESONANCE IMAGING

摘要

Salt weathering is one of the major causes of deterioration of buildings and monuments. We have determined the underlying moisture and ion transport within a representative building material by measuring the time evolution of NaCl saturated samples during one-sided drying with Magnetic Resonance Imaging. The obtained NaCl concentration profiles reflect the competition between advection to the surface and redistribution by diffusion. By representing the measured moisture and NaCl profiles in a so-called efflorescence pathway diagram (EPD) also information about the crystallization process is obtained. The pathways followed in the EPDs indicate that for historical objects in general crystallization at the surface cannot be avoided, when evaporation cannot be prevented.