Friedel's salt

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IUPACName = Calcium chloroaluminate
OtherNames = Friedel's salt
Calcium aluminium chlorohydrate
Calcium aluminium chlorohydroxide
Calcium aluminium oxychloride
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Formula = Ca₂Al(OH)₆(Cl, OH) · 2 H₂O
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Appearance = White solid
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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.

Composition

Friedel's salt general formula is:

:Ca₂Al(OH)₆(Cl, OH) · 2 H₂O.

In the cement chemistry notation, considering that

:2 OH^– ↔ O^2– + H₂O,

and doubling all the stoechiometry, it can also be written as follows:

:3CaO·Al₂O₃·CaCl₂ · 10 H₂O

Friedel's salt forms in cements rich in tri-calcium aluminate (C3A).

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.

Discovery

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. Fact|date=October 2008. [ [http://www.annales.org/archives/x/gfriedel.html Biography of Georges Friedel by F. Greandjean on annales.org., in French.] ]

Formation

* 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.

Anion getter

* Trap toxic anions in cement such as, "e.g.", ¹²⁹I^-, SeO₃^2-, SeO₄^2-

ee also

* Cement
* Concrete
* Chloride
* Layered double hydroxides
* Tricalcium aluminate
* Charles Friedel
* Georges Friedel
* [http://www.annales.org/archives/x/friedel.html Edmond Friedel (1895-1972)]
* Jacques Friedel
* Friedel-Crafts reaction

References

* Cite journal
last = Bai
first = J.
coauthors = S. Wild, B. B. Sabir
date = 2003
title = Chloride ingress and strength loss in concrete with different PC–PFA–MK binder compositions exposed to synthetic seawater
journal = Cement and Concrete Research
volume = 33
issue = 3
pages = 353-362

* Cite journal
last = Barberon
first = F.
coauthors = V. Baroghel-Bouny, H. Zanni, B. Bresson, J. B. d'Espinose de la Caillerie, L. Malosse, Z. Gan
date = 2005
title = Interactions between chloride and cement-paste materials
journal = Magnetic Resonance Imaging
volume = 23
issue = 2
pages = 267-272

* Cite journal
last = Birnin-Yauri
first = U. A.
coauthors = F. P. Glasser
date = 1998
title = Friedel's salt, Ca₂ Al(OH)₆ (Cl, OH) · 2H₂O: its solid solutions and their role in chloride binding
journal = Cement and Concrete Research
volume = 28
issue = 12
pages = 1713-1723

* Cite journal
last = Bothe
first = James V.
coauthors = Paul W. Brown
date = 2004-06
title = PhreeqC modeling of Friedel's salt equilibria at 23 ± 1 °C
journal = Cement and Concrete Research
doi = 10.1016/j.cemconres.2003.11.016
volume = 34
issue = 6
pages = 1057-1063
accessdate = 2008-10-04
url = http://www.sciencedirect.com/science/article/B6TWG-4B94K0R-1/2/2182af1335b6bdcd0a4cecc34f70d7f7

* Cite journal
last = Brown
first = P. W.
coauthors = S. Badger
date = 2000
title = The distributions of bound sulfates and chlorides in concrete subjected to mixed NaCl, MgSO₄, Na₂SO₄ attack
journal = Cement and Concrete Research
volume = 30
issue = 10
pages = 1535-1542

* Cite journal
last = Brown
first = P. W.
coauthors = A. Doerr
date = 2000
title = Chemical changes in concrete due to the ingress of aggressive species
journal = Cement and Concrete Research
volume = 30
issue = 3
pages = 411-418

* Cite journal
last = Chatterji
first = S.
date = 1995
title = On the applicability of Fick's second law to chloride ion migration through portland cement concrete
journal = Cement and Concrete Research
volume = 25
issue = 2
pages = 299-303

* Cite journal
last = Csizmadia
first = J.
coauthors = G. Balázs, F. D. Tamás
date = 2001
title = Chloride ion binding capacity of aluminoferrites
journal = Cement and Concrete Research
volume = 31
issue = 4
pages = 577-588

* Cite journal
last = Mohammed
first = T. U.
coauthors = H. Hamada
date = 2003
title = Relationship between free chloride and total chloride contents in concrete
journal = Cement and Concrete Research
volume = 33
issue = 9
pages = 1487-1490

* Cite journal
last = Nakamura
first = A.
coauthors = E. Sakai, K. Nishizawa, Y. Ohba, M. Daimon
date = 1999
title = Sorption of chloride-ion, sulfate-ion and phosphate-ion in calcium silicate hydrates
journal = Journal of the Chemical Society
pages = 415-420

* Cite journal
last = Nielsen
first = E. P.
coauthors = M. R. Geiker
date = 2003
title = Chloride diffusion in partially saturated cementitious material
journal = Cement and Concrete Research
volume = 33
issue = 1
pages = 133-138

* Cite book
last = Pitt
first = J. M.
coauthors = M. C. Schluter, D. Y. Lee, W. Dubberke
date = 1987
title = Sulfate impurities from deicing salt and durability of Portland cement mortar
publisher = Transportation Research Board

* Cite journal
last = Reddy
first = B.
coauthors = G. K. Glass, P. J. Lim, N. R. Buenfeld
date = 2002
title = On the corrosion risk presented by chloride bound in concrete
journal = Cement and Concrete Composites
volume = 24
issue = 1
pages = 1-5

* Cite journal
last = Suryavanshi
first = AK
coauthors = RN Swamy
date = 1998
title = Influence of penetrating chlorides on the pore structure of structural concrete
journal = Cement, concrete and aggregates
volume = 20
issue = 1
pages = 169-179

* Cite journal
last = Suryavanshi
first = A. K.
coauthors = J. D. Scantlebury, S. B. Lyon
date = 1996
title = Mechanism of Friedel's salt formation in cements rich in tri-calcium aluminate
journal = Cement and Concrete Research
volume = 26
issue = 5
pages = 717-727

External links

* [http://cat.inist.fr/?aModele=afficheN&cpsidt=1654808 Friedel's salt, Ca₂Al(OH)₆ (Cl, OH) · 2H₂O: Its solid solutions and their role in chloride binding]
* [http://www.whd.co.uk/understanding%20cement/cementandconcret.html Glossary of cement concrete and SEM terminology]