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|Molecular formula||Ca2Al(OH)6(Cl, OH) · 2 H2O|
| (what is: / ?)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
Friedel's salt is an anion exchanger mineral belonging to the family of the layered double hydroxides (LDHs). It has affinity for anions as chloride and iodide and is capable to retain them to a certain extent in its crystallographical structure.
Friedel's salt general formula is:
- Ca2Al(OH)6(Cl, OH) · 2 H2O.
In the cement chemist notation, considering that
- 2 OH– ↔ O2– + H2O,
and doubling all the stoichiometry, it can also be written as follows:
- 3CaO·Al2O3·CaCl2 · 10 H2O
- 2 Cl- + 3CaO·Al2O3·CaSO4 · 10 H2O → 3CaO·Al2O3·CaCl2 · 10 H2O + SO42-
It plays a main role in the retention of chloride anions in cement and concrete. However, Friedel's salt remains a poorly understood phase in the CaO-Al2O3-CaCl2-H2O system, and is critical for the stability of salt-saturated Portland cement-based grouts.
Nowadays, Friedel's salt discovery is relatively difficult to trace back from the recent literature, simply because it is an ancient finding of a poorly known and non-natural product. It has been synthesised and identified in 1897 by Georges Friedel, mineralogist and crystallographer, son of the famous French chemist Charles Friedel. Georges Friedel also synthesised Calcium aluminate (1903) in the framework of his work on the Macles theory (twin crystals). This point requires further verification.
- Relation with Tricalcium aluminate.
- Incorporation of chloride.
- Solid solutions.
Role in cement
- Importance for the reactive transport of chloride in cement in relation with corrosion of steel reinforcement.
- Trap toxic anions in cement such as, e.g., 129I-, SeO32-, SeO42-
- Aluminium chlorohydrate
- Salt-concrete, also known as salzbeton
- Layered double hydroxides
- Tricalcium aluminate
- Friedel-Crafts reaction
- Friedel family, a rich lineage of French scientists:
- Charles Friedel (1832–1899), French chemist known for the Friedel-Crafts reaction
- Georges Friedel (1865–1933), here above mentioned, French crystallographer and mineralogist; son of Charles
- Edmond Friedel (1895-1972) (1895–1972), French Polytechnician and mining engineer, founder of BRGM, the French geological survey; son of Georges
- Jacques Friedel, (1921-), French physicist; son of Edmond, see the French site for Jacques Friedel
- Friedel, Georges (1897). "Sur un chloro-aluminate de calcium hydrate´ se maclant par compression". Bulletin de la Société française de minéralogie et de cristallographie 19: 122–136.
- Biography of Georges Friedel by F. Greandjean on annales.org., in French.
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