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Portlandite

Portlandite is a mineral formed during the curing of concrete, also known as portland cement. It is a calcium hydroxide mineral, Ca(OH)2, and is quite common. Although the majority of portlandite is formed during the curing of concrete, it does occur in nature as soft, typically white masses. Occasional crystals may be found.

Distribution

Portlandite is the major bonding agent in cement and concrete. It is formed during the curing process, when elemental calcium reacts with water to form calcium hydroxide.

Henderson D.M., and H.S. Gutovsky. 1956. Bull. Geol. Soc. Amer. 67:1705