Chemical elements
    Physical properties
    Chemical properties
      Aluminium subfluoride
      Aluminium trifluoride
      Aluminium trichloride
      Aluminium tribromide
      Aluminium iodide
      Aluminium chlorate
      Aluminium perchlorate
      Aluminium bromate
      Aluminium periodate
      Aluminium suboxide
      Aluminium sesqui-oxide
      Aluminium peroxide
      Aluminium hydroxides
      Tricalcium aluminate
      Sodilim aluminate
      Aluminium sesqui-sulphide
      Aluminium selenide
      Aluminium telluride
      Aluminium sulphite
      Aluminium sulphate
      Sodium alum
      Potassium alum
      Ammonium alum
      Hydroxylamine alum
      Silver alum
      Aluminium dithionate
      Aluminium selenite
      Aluminium selenate
      Aluminium chromate
      Aluminium molybdate
      Aluminium silicomolybdate
      Aluminium tungstate
      Aluminium silicotungstate
      Aluminium phosphotungstate
      Aluminium nitride
      Aluminium phosphide
      Aluminium arsenide
      Aluminium nitrate
      Aluminium Phosphates
      Basic aluminium arsenite
      Aluminium carbide
      Aluminium carbonate
      Aluminium thiocyanate
      Aluminium oxalate
      Aluminium alkyls
      Aluminium Hydrocarbon
      Aluminium acetylacetonate
      Aluminium silicide
      Aluminium silicates
      Aluminosilicic acids aluminosilicates
      Aluminium Borides
      Aluminium Boride
      Aluminium Boride
      Aluminium borocarbides
      Aluminium borate
      Aluminium sodium perborate
    PDB 1a6e-1zca
    PDB 2b8w-3i62
    PDB 3kql-5ukd

Tricalcium aluminate, 3CaO.Al2O3

Tricalcium aluminate, 3CaO.Al2O3.
system lime-silica-alumina
Projection of liquidus surface for the system lime-silica-alumina.
Tricalcium aluminate, 3CaO.Al2O3, is an important constituent of Portland cement clinker, which consists mainly (over 90 per cent.) of silica, lime, and alumina. Its constitution has long been the subject of discussion. A complete thermal and optical study of the system lime - silica - alumina has been made by Rankin and Wright, and the results, so far as they bear on the constitution of Portland cement, are shown in fig. Considering only the lime, silica, and alumina content, the variations in the composition of the commercial cement are restricted to the area ABCD. It may be deduced from the diagram by aid of the Phase Rule that a fluid mass of this composition, when slowly cooled until complete solidification has occurred, is converted into a mixture of tricalcium silicate, 3CaO.SiO2, dicalcium silicate, 2CaO.SiO2, and tricalcium aluminate, 3CaO.Al2O3.

Portland cement clinker should therefore consist essentially of these three compounds if, in its manufacture, the heating be prolonged for a length of time sufficient for equilibrium to be established. This deduction has been verified by experiments carried out in the laboratories of the United States Bureau of Standards. Since, however, complete equilibrium is not reached in its manufacture, the cement also contains lime, CaO, and the aluminate 5CaO.3Al2O3 as minor constituents. The iron oxide contained in the cement may be present as calcium ferrite or magnetite, or held in solid solution in the compounds 2CaO.SiO2 and 5CaO.2Al2O3; the magnesia and alkalies are apparently held in solid solution in the compounds 2CaO.SiO2 and 3CaO.Al2O3.

In contact with water, the compounds CaO.Al2O3, 3CaO.Al2O3, and 5CaO.3Al2O3 yield an amorphous hydrate, 3CaO.Al2O3.xH2O, which in time crystallises; except with tricalcium aluminate, amorphous aluminium hydroxide is also formed. When hydrated with aqueous calcium sulphate an additional compound, calcium "sulpho-aluminate." 3CaO.Al2O3.3CaSO4.xH2O, is formed, which crystallises in long prismatic needles.

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