Torbermorite CSH 3D Crystal Structure RasMol.gif on:
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Tobermorite is a calcium silicate hydrate mineral with chemical formula:
Ca5Si6O16(OH)2·4H2O or
Ca5Si6(O,OH)18·5H2O.
Two structural varieties are distinguished: tobermorite-11 Å and tobermorite-14 Å.
Tobermorite occurs in hydrated cement paste and can be found in nature as alteration mineral in metamorphosed limestone and in skarn. It has been reported from the Maqarin Area of north Jordan and in the Crestmore Quarry near Crestmore Heights, Riverside County, California.
Tobermorite was first described in 1880 for an occurrence in Scotland, on the
'' Washington Post'', Ben Guarino, July 4, 2017. Retrieved July 5, 2017.''Ancient lessons: Roman concrete durable, green'', Jim Destefani, ed., Ceramic Tech Today, The American Ceramic Society, June 7, 2013
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Tobermorite in the American Mineralogist Crystal Structure Database
{{commonscat, Tobermorite Calcium compounds Calcium minerals Cement Crestmore Heights, California Geology of Riverside County, California Hydrates Inorganic compounds Inosilicates Minerals in space group 20 Orthorhombic minerals
Isle of Mull
The Isle of Mull ( gd, An t-Eilean Muileach ) or just Mull (; gd, Muile, links=no ) is the second-largest island of the Inner Hebrides (after Skye) and lies off the west coast of Scotland in the Council areas of Scotland, council area of Arg ...
, around the locality of Tobermory.
Use in Roman concrete
Aluminum substituted tobermorite is understood to be a key ingredient in the longevity of ancient undersea Roman concrete. The volcanic ash that Romans used for construction of sea walls containedphillipsite
Phillipsite is a mineral series of the zeolite group; a hydrated potassium, calcium and aluminium silicate, approximating to . The members of the series are phillipsite-K, phillipsite-Na and phillipsite-Ca. The crystals are monoclinic, but only c ...
, and an interaction with sea water actually caused the crystalline structures in the concrete to expand and strengthen, making that material substantially more durable than modern concrete when exposed to sea water. Ancient Romans made world’s ‘most durable’ concrete. We might use it to stop rising seas'' Washington Post'', Ben Guarino, July 4, 2017. Retrieved July 5, 2017.
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Cement chemistry
Tobermorite is often used in thermodynamical calculations to represent the pole of the most evolved calcium silicate hydrate (C-S-H). The value of its atomic Ca/Si or molar CaO/SiO2 (C/S) ratio is 0.83 (5/6) as directly calculated from its elementary composition formula. Jennite represents the less evolved pole with a C/S ratio of 1.50 (9/6).See also
* Other calcium silicate hydrate (C-S-H) minerals: ** ** ** ** * Other calcium aluminium silicate hydrate, (C-A-S-H) minerals: **Hydrogarnet
Hydrogrossular is a calcium aluminium garnet series (formula: Ca3Al2(SiO4)3−''x''(OH)4''x'', with hydroxide (OH) partially replacing silica (SiO4)). The endmembers of the hydrogarnet family (grossular, hibschite, and katoite) depend on the deg ...
** Hydrotalcite
Hydrotalcite or formerly also Völknerite is a layered double hydroxide (LDH) of general formula ·4, whose name is derived from its resemblance with talc and its high water content. Multiple structures containing loosely bound carbonate ions ex ...
References
* American Mineralogist (1954) 39, 1038. * * * * * * * * * *External links
Tobermorite in the American Mineralogist Crystal Structure Database
{{commonscat, Tobermorite Calcium compounds Calcium minerals Cement Crestmore Heights, California Geology of Riverside County, California Hydrates Inorganic compounds Inosilicates Minerals in space group 20 Orthorhombic minerals