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Calcium aluminates phase diagram Crystal structure of dodecacalcium hepta-aluminate, 12CaO·7Al 2 O 3 (C 12 A 7). [1] Calcium aluminates are a range of materials [2] obtained by heating calcium oxide and aluminium oxide together at high temperatures. They are encountered in the manufacture of refractories and cements.
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AFm form inter alia when tricalcium aluminate 3CaO·Al 2 O 3, or C 3 A in CCN, reacts with dissolved calcium sulfate (CaSO 4), or calcium carbonate (CaCO 3). As the sulfate form is the dominant one in AFm phases in the hardened cement paste (HCP) in concrete, AFm is often simply referred to as Aluminate Ferrite monosulfate or calcium aluminate ...
The hydration reactions of calcium aluminate cements are very complex. The strength-developing phases are monocalcium aluminate (CA), dodeca-calcium hepta-aluminate (C 12 A 7), and belite (C 2 S), a dicalcium silicate. Calcium aluminoferrite (C 4 AF), monocalcium dialuminate (CA 2), gehlenite, and pleochroite contribute little to the concrete ...
Tricalcium aluminate Ca 3 Al 2 O 6, often formulated as 3CaO·Al 2 O 3 to highlight the proportions of the oxides from which it is made, is the most basic of the calcium aluminates. It does not occur in nature, but is an important mineral phase in Portland cement .
Calcium aluminates can form complex salts in combination with different types of anions.Two series of calcium aluminates are known in cement chemistry: AFm and AFt phases, being respectively mono- or tri-substituted with a given divalent anion X (e.g. SO 2− 4, CO 2− 3, or hosting a divalent impurity such as SeO 2− 4 [3]...), or with two units of a monovalent anion, e.g. OH −, Cl − ...
Dodecacalcium hepta-aluminate (12CaO·7Al 2 O 3, Ca 12 Al 14 O 33 or C 12 A 7) is an inorganic solid that occurs rarely in nature as the mineral mayenite. It is an important phase in calcium aluminate cements and is an intermediate in the manufacture of Portland cement. Its composition and properties have been the subject of much debate ...
4 AF) (white) and tricalcium aluminate (C 3 A) (grey) occupying interstitial space between alite (C 3 S) (blue) and belite (C 2 S) (orange) crystals. These are false (interference) colors. Calcium aluminoferrite (Ca 2 (Al,Fe) 2 O 5) is a dark brown crystalline phase commonly found in cements. In the cement industry it is termed tetra-calcium ...