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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.
Phase diagram of calcium aluminates present in the anhydrous calcium aluminate cement before hydration. ... and is stable at high temperatures and thermal cycling ...
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 ...
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 − ...
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 Portland clinker essentially consists of four minerals: two calcium silicates, alite (Ca 3 SiO 5) and belite (Ca 2 SiO 4), along with tricalcium aluminate (Ca 3 Al 2 O 6) and calcium aluminoferrite (Ca 2 (Al,Fe) 2 O 5). These main mineral phases are produced by heating at high temperature clays and limestone. [3]
The active ingredients are monocalcium aluminate CaAl 2 O 4 (CaO · Al 2 O 3 or CA in cement chemist notation, CCN) and mayenite Ca 12 Al 14 O 33 (12 CaO · 7 Al 2 O 3, or C 12 A 7 in CCN). Strength forms by hydration to calcium aluminate hydrates. They are well-adapted for use in refractory (high-temperature resistant) concretes, e.g., for ...