Calcium hydroxychloride

Calcium hydroxychloride or calcium chloride hydroxide is an inorganic compound with the chemical formula Ca(OH)Cl. It consists of calcium cations (Ca²⁺) and chloride (Cl⁻) and hydroxide (⁻OH) anions. A white solid, it forms by the reaction of hydrogen chloride with calcium hydroxide According to X-ray crystallography, it adopts a layered structure related to brucite (magnesium hydroxide, Mg(OH)₂).

Calcium hydroxychloride is sometimes confused with calcium hypochlorite. Calcium hydroxychloride is a double salt, which consists of calcium cations Ca²⁺ and two kinds of anions, chloride Cl⁻ and hydroxide ⁻OH, while calcium hypochlorite consists of calcium cations Ca²⁺ and only one kind of anions, hypochlorite ⁻OCl.

Calcium hydroxychloride may form on concrete roads and bridges as a consequence of the use of calcium chloride as a deicing agent. Calcium chloride reacts with calcium hydroxide (portlandite) present in cement hydration products and forms a deleterious expanding phase also named CAOXY (abbreviation for calcium oxychloride) by concrete technologists. The stress induced into concrete by crystallisation pressure and CAOXY salt expansion can considerably reduce the strength of concrete.

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