Salts in the Deterioration of Porous Materials: An Overview

The present overview on salt-induced deterioration of inorganic porous materials focuses on those topics considered the most relevant for understanding this phenomenon. These are movement of both water/moisture and salts within the pore system; influence of the presence of salts in moisture absorption; effect of the simultaneous presence of more than one salt; salt distribution in masonry; deterioration mechanisms; and weathering patterns. Of the latter, the most ubiquitous are powdering and scaling, and they have been found to occur on most stone types. However, the mechanism that induces the same outward appearance on different stones can vary significantly depending on the synergism that develops among porous material, salt, and moisture.