Salt distribution mapping in natural building and decorative stones

Abstract

Despite extensive work in the field of salt crystallization throughout the years, there are few reported attempts in the literature to map the distribution of the salt front in porous masonry materials and therefore try to explain the effect pore clogging may have on the damage caused by salt weathering. In the research reported in this paper, relatively new and complimentary test methods (drilling and scratch resistance measurements) for assessing the mechanical properties of materials have been applied to map the distribution of salts within natural building stone. The results show that both methods may be used successfully for salt distribution mapping. Through the application of these techniques, it is confirmed that sodium sulfate salt crystallizes in a thin layer at or just behind the surface of the stone, and that the use of water repellent forces this layer further behind the surface.