Efflorescence is a chalky, white mineral deposit caused by soluble salts. These salts can come from many sources including such Portland cement-based products as concrete slabs, concrete and masonry walls, cement-based grouts, cement-based thin-set mortars and cement pavers. Well water that has a naturally high concentration of minerals can also cause efflorescence. In addition, home water softeners add minerals to the water, which can contribute to efflorescence.
