SALTS IN THE DETERIORATION OF POROUS MATERIALS: AN OVERVIEW
A. ELENA CHAROLA
3 2. ORIGIN OF SALTS
As C. Price (1996) summarizes in his review on stone deterioration, salts can originate from various sources: air pollution, deicing salts, soil, sea spray, inappropriate treatments, or interaction between building materials. Some materials may even contain salts inherently. For example, Portland cement usually contains alkali sulfates that are released from concrete or cement mortars; and bricks, if not fired adequately, may contain sodium sulfate. This salt becomes evident as efflorescences on random bricks soon after construction of the masonry. Historic buildings, over centuries, may accumulate a high concentration of salts, particularly if some sections of them had been used for salt storage or as stables.