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Tobermorite is a
calcium silicate hydrate Calcium silicate hydrate (or C-S-H) is the main product of the hydration of Portland cement and is primarily responsible for the strength in cement based materials (e.g. concrete). Preparation When water is added to cement, each of the compounds ...
mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. (2 ...
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 A cement is a binder, a chemical substance used for construction that sets, hardens, and adheres to other materials to bind them together. Cement is seldom used on its own, but rather to bind sand and gravel ( aggregate) together. Cement mi ...
paste and can be found in nature as alteration mineral in
metamorphosed Metamorphic rocks arise from the transformation of existing rock to new types of rock in a process called metamorphism. The original rock (protolith) is subjected to temperatures greater than and, often, elevated pressure of or more, causi ...
limestone Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms whe ...
and in
skarn Skarns or tactites are hard, coarse-grained metamorphic rocks that form by a process called metasomatism. Skarns tend to be rich in calcium-magnesium-iron-manganese-aluminium silicate minerals, which are also referred to as calc-silicate mineral ...
. It has been reported from the Maqarin Area of north
Jordan Jordan ( ar, الأردن; tr. ' ), officially the Hashemite Kingdom of Jordan,; tr. ' is a country in Western Asia. It is situated at the crossroads of Asia, Africa, and Europe, within the Levant region, on the East Bank of the Jordan Rive ...
and in the Crestmore Quarry near Crestmore Heights,
Riverside County Riverside County is a county located in the southern portion of the U.S. state of California. As of the 2020 census, the population was 2,418,185, making it the fourth-most populous county in California and the 10th-most populous in the Uni ...
,
California California is a state in the Western United States, located along the Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the most populous U.S. state and the 3rd largest by area. It is also the m ...
. Tobermorite was first described in 1880 for an occurrence in
Scotland Scotland (, ) is a Countries of the United Kingdom, country that is part of the United Kingdom. Covering the northern third of the island of Great Britain, mainland Scotland has a Anglo-Scottish border, border with England to the southeast ...
, on the Isle of Mull, 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 Roman concrete, also called , is a material that was used in construction in ancient Rome. Roman concrete was based on a hydraulic-setting cement. It is durable due to its incorporation of pozzolanic ash, which prevents cracks from spreading. ...
. The volcanic ash that Romans used for construction of sea walls contained phillipsite, 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 ''The Washington Post'' (also known as the ''Post'' and, informally, ''WaPo'') is an American daily newspaper published in Washington, D.C. It is the most widely circulated newspaper within the Washington metropolitan area and has a large na ...
'', 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
/ref>


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 Jennite is a calcium silicate hydrate mineral of general chemical formula: Ca9Si6O18(OH)6·8H2O. Jennite occurs as an alteration mineral in metamorphosed limestone and skarn. It typically occurs as vein and open space fillings as a late minera ...
represents the less evolved pole with a C/S ratio of 1.50 (9/6).


See also

* Other
calcium silicate hydrate Calcium silicate hydrate (or C-S-H) is the main product of the hydration of Portland cement and is primarily responsible for the strength in cement based materials (e.g. concrete). Preparation When water is added to cement, each of the compounds ...
(C-S-H) minerals: ** ** ** ** * Other calcium aluminium silicate hydrate, (C-A-S-H) minerals: ** Hydrogarnet ** Hydrotalcite


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