Friedel's salt
Encyclopedia
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.
In the cement chemist notation
, considering that
and doubling all the stoichiometry, it can also be written as follows:
Friedel's salt can also be considered as an AFm phase
in which chloride ions have replaced sulfate ions and is formed in cements initially 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.
, 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 Macle
s theory (twin crystals). This point requires further verification.
Layered double hydroxides
Layered double hydroxides comprise an unusual class of layered materials with positively charged layers and charge balancing anions located in the interlayer region. This is unusual in solid state chemistry: many more families of materials have negatively charged layers and cations in the...
(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 chemist notation
Cement chemist notation
Cement chemist notation was developed to simplify the formulas cement chemists use on a daily basis. It is a "short hand" way of writing the chemical formula of oxides of calcium, silicon, and various metals.-Abbreviations of oxides:...
, considering that
- 2 OH– ↔ O2– + H2O,
and doubling all the stoichiometry, it can also be written as follows:
- 3CaO·Al2O3·CaCl2 · 10 H2O
Friedel's salt can also be considered as an AFm phase
AFm phase
An AFm phase is an "alumina, ferric oxide, monosulfate" phase. AFm phases are important in the hydration of hydraulic cements.They are crystalline hydrates with general, simplified formula 3 CaO·2O3·CaSO4·nH2O....
in which chloride ions have replaced sulfate ions and is formed in cements initially rich in tri-calcium aluminate
Tricalcium aluminate
Tricalcium aluminate Ca3Al2O6, often formulated as 3CaO·Al2O3 to highlight the proportions of the oxides from which it is made, is the most basic of the calcium aluminates...
(C3A).
- 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.
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 FriedelGeorges Friedel
Georges Friedel was a French mineralogist and crystallographer.- Life :Georges was the son of the famous chemist Charles Friedel...
, mineralogist and crystallographer, son of the famous French chemist Charles Friedel
Charles Friedel
Charles Friedel was a French chemist and mineralogist. A native of Strasbourg, France, he was a student of Louis Pasteur at the Sorbonne...
. Georges Friedel also synthesised Calcium aluminate (1903) in the framework of his work on the Macle
Macle
Macle is a term used in crystallography. It is a crystalline form, twin-crystal or double crystal .Macle is an old French word, a heraldic term for a voided lozenge...
s theory (twin crystals). This point requires further verification.
Formation
- Relation with Tricalcium aluminateTricalcium aluminateTricalcium aluminate Ca3Al2O6, often formulated as 3CaO·Al2O3 to highlight the proportions of the oxides from which it is made, is the most basic of the calcium aluminates...
. - 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-, SeO32-, SeO42-
See also
- Aluminium chlorohydrateAluminium chlorohydrateAluminium chlorohydrate is a group of specific aluminium salts having the general formula AlnClm. It is used in deodorants and antiperspirants and as a coagulant in water purification....
- CementCementIn the most general sense of the word, a cement is a binder, a substance that sets and hardens independently, and can bind other materials together. The word "cement" traces to the Romans, who used the term opus caementicium to describe masonry resembling modern concrete that was made from crushed...
- Sorel cementSorel cementSorel cement is a non-hydraulic cement first produced by Frenchman Stanislas Sorel in 1867.The cement is a mixture of magnesium oxide with magnesium chloride with the approximate chemical formula Mg4Cl268, corresponding to a weight ratio of 2.5–3.5 parts MgO to one part MgCl2...
, a mixture of general formula: Mg4Cl2(OH)6 - Stanislas SorelStanislas SorelStanislas Sorel was a French engineer, raised the son of a poor clock-maker.Sorel filed a patent on 10 May 1837 for a "galvanic" method of protecting iron from rust by either coating it in a bath of molten zinc or by covering it with galvanic paint...
, a french engineer who made a new form of cement from a combination of magnesium oxideMagnesium oxideMagnesium oxide , or magnesia, is a white hygroscopic solid mineral that occurs naturally as periclase and is a source of magnesium . It has an empirical formula of and consists of a lattice of Mg2+ ions and O2– ions held together by ionic bonds...
and magnesium chlorideMagnesium chlorideMagnesium chloride is the name for the chemical compounds with the formulas MgCl2 and its various hydrates MgCl2x. These salts are typical ionic halides, being highly soluble in water. The hydrated magnesium chloride can be extracted from brine or sea water...
- Sorel cement
- ConcreteConcreteConcrete is a composite construction material, composed of cement and other cementitious materials such as fly ash and slag cement, aggregate , water and chemical admixtures.The word concrete comes from the Latin word...
- Salt-concreteSalt-concreteSalt-concrete is a construction material that is used to reduce the water inflow in mining shafts in salt mines. It is composed of 16% cement, 39% halite, 16% limestone powder, 14% water and 15% sand.-History:...
, also known as salzbeton
- Salt-concrete
- ChlorideChlorideThe chloride ion is formed when the element chlorine, a halogen, picks up one electron to form an anion Cl−. The salts of hydrochloric acid HCl contain chloride ions and can also be called chlorides. The chloride ion, and its salts such as sodium chloride, are very soluble in water...
- Layered double hydroxidesLayered double hydroxidesLayered double hydroxides comprise an unusual class of layered materials with positively charged layers and charge balancing anions located in the interlayer region. This is unusual in solid state chemistry: many more families of materials have negatively charged layers and cations in the...
- Tricalcium aluminateTricalcium aluminateTricalcium aluminate Ca3Al2O6, often formulated as 3CaO·Al2O3 to highlight the proportions of the oxides from which it is made, is the most basic of the calcium aluminates...
- Friedel-Crafts reactionFriedel-Crafts reactionThe Friedel–Crafts reactions are a set of reactions developed by Charles Friedel and James Crafts in 1877. There are two main types of Friedel–Crafts reactions: alkylation reactions and acylation reactions. This reaction type is a form of electrophilic aromatic substitution...
- Friedel familyFriedel familyFour French scientists with the same Friedel family name are in direct lineage, Charles, Georges, Edmond and Jacques:* Charles Friedel , French chemist known for the Friedel-Crafts reaction...
, a rich lineage of French scientists:- Charles FriedelCharles FriedelCharles Friedel was a French chemist and mineralogist. A native of Strasbourg, France, he was a student of Louis Pasteur at the Sorbonne...
(1832–1899), French chemist known for the Friedel-Crafts reactionFriedel-Crafts reactionThe Friedel–Crafts reactions are a set of reactions developed by Charles Friedel and James Crafts in 1877. There are two main types of Friedel–Crafts reactions: alkylation reactions and acylation reactions. This reaction type is a form of electrophilic aromatic substitution... - Georges FriedelGeorges FriedelGeorges Friedel was a French mineralogist and crystallographer.- Life :Georges was the son of the famous chemist Charles 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 FriedelJacques FriedelJacques Friedel FMRS is a French physicist and material scientist.-Life:His great-grand father Charles Friedel was an organic chemist and crystallographer at Paris-Sorbonne University, his grand-father Georges Friedel worked on liquid crystals, and his father Edmond Friedel was the director of the...
, (1921-), French physicist; son of Edmond, see the French site for Jacques Friedel
- Charles Friedel