Efflorescence control admixtures inhibit the formation of a white haze or chalky deposition as the result of concrete exposure to water and/or environmental conditions. There are two type of efflorescence – Primary of Bloom Efflorescence, and Secondary Efflorescence. Primary or Bloom efflorescence occurs as the result of free lime or calcium oxide, inherently present in Portland cement, which reacts with water to form Calcium Hydroxide. Calcium Hydroxide, a solid, has a limited but unique solubility, displaying increased solubility in colder conditions. The solubility of the Calcium Hydroxide liberates Calcium ions, where they diffuse to the surface of the concrete during the curing process. These liberated Calcium ions, as they reach the concrete surface, react with the carbon dioxide in the air and form chalk – the white haze or deposition commonly referred to as efflorescence. Because of the unique solubility of Calcium Hydroxide, primary efflorescence is always more prevalent in cold wet conditions.
Secondary efflorescence occurs after the concrete has fully cured. Salts solutions, which form from naturally occurring salts or those intentionally distributed onto concrete by man, penetrate the concrete and destroy the cement portion, liberating calcium. Often referred to as “osteoporosis of concrete,” the liberated calcium as the result of secondary efflorescence diffuses to the surface of the concrete, where they react with the carbon dioxide in the air and form chalk.
Efflorescence control admixtures work in a variety of ways, all intended to affect the capillary action of water, or to reduce the amount of available or liberated calcium ions from reaching the surface of the concrete.