ABSTRACT
Sodium sulfate is often regarded as the most damaging soluble salt to afflict masonry and concrete. It has a high and very temperature sensitive solubility which can produce a significant amount of hydrate crystal growth on cooling. Dissolution and crystallization cycling between thenardite and mirabilite, which can occur during normal urban diurnal heating and cooling, can produce significant damage. Combined, the hydrate chemistry of sodium sulfate and solubility relationship between phases leads to damage from frequent dissolution and precipitation. Damage to masonry from salt crystallization is poorly understood and therefore difficult to remediate against. Salt and ice crystallization inside the pores of building materials is a well-known deterioration mechanism, however very little is known about why some salts are more damaging than others or the development of pore level strain prior to fracture. Almost all literature on sodium sulfate and stone damage assumed that mirabilite was the only hydrate to form.
