Portlandite is an oxide mineral.It is the naturally occurring form of calcium hydroxide (Ca(OH) 2) and the calcium analogue of brucite (Mg(OH) 2).. Occurrence. Portlandite occurs in a variety of environments. At the type location in Northern Ireland it occurs as an alteration of calc–silicate rocks by contact metamorphism of larnite–spurrite.It occurs as fumarole deposits in the Vesuvius area.
The carbonated portlandite showed a 38.4% weight loss due to the release of the CO 2 at 700°C (almost 40%, the maximum theoretical weight loss of pure calcite), indicating that all the calcium present in the sample, whether from portlandite or from other minor calcium compounds, was carbonated and revealed an extremely high carbonation ...
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.
Portlandite and other recent mineral discoveries in the granites at Lake Boga, and Wycheproof and Pyramid Hill, Victoria. Australian Journal of Mineralogy Vol.2 No.2 Dec. 1996, pp. 47-50 Belgium
In this study, the significantly higher yield achieved by the FBA treatment supports the explanation given above, because slaked FBA contained not only gypsum but portlandite, calcite and other alkaline components and these compounds were responsible for the significant decrease in labile monomeric Al concentrations in the topsoils (Figs 1 and 2).
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REFERENCES for Portlandite; American Mineralogist Crystal Structure Database Record: [view record] Anthony J W, Bideaux R A, Bladh K W, and Nichols M C (1990) Handbook of Mineralogy, Mineral Data Publishing, Tucson Arizona, USA, by permission of the Mineralogical Society of America.
Portlandite Ca(OH)2 c 2001-2005 Mineral Data Publishing, version 1 Crystal Data: Hexagonal. Point Group: 32/m. Hexagonal plates, to 6 cm; commonly ﬁbrous, powdery, massive.
5.4.3 Calcium Hydroxide (CH) Calcium hydroxide, also known by its mineral name portlandite, forms from C 3 S and, to a lesser extent, C2S via reactions 5.1 and 5.2. It occupies about 15% of the volume of a normal portland cement paste (not 20-25%, as is reported in some texts [7, ]).
The solubility of calcium hydroxide (portlandite) at 70 °C is about half of its value at 25 °C. The reason for this rather uncommon phenomenon is that the dissolution of calcium hydroxide in water is an exothermic process, and also adheres to Le Chatelier's principle.