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So, CAC cement must not be confused with calcium sulfo-aluminate (CSA) cement containing calcium sulfate and invented later in 1936. [6] The main constituent, and also the most reactive phase, of calcium aluminate cements is the monocalcium aluminate (CaAl 2 O 4 = CaO · Al 2 O 3, also written as CA in the cement chemist notation).
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 − ...
The necessary additional calcium is provided by the calcium hydroxide and calcium silicate hydrate in the cement paste; The effect of these changes is an overall loss of concrete strength. The above effects are typical of attack by solutions of sodium sulfate or potassium sulfate. Solutions containing magnesium sulfate are generally more ...
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 ...
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.
In calcium aluminate cements, it exists as a solid solution in which the amount of minor elements depends upon the bulk composition of the cement. A typical composition [4] is Ca 0.93 Al 1.94 Fe 0.11 Si 0.02 O 4.
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 .
In concrete chemistry, ettringite is a hexacalcium aluminate trisulfate hydrate, of general formula when noted as oxides: 6CaO·Al 2 O 3 ·3SO 3 ·32H 2 O. or 3CaO·Al 2 O 3 ·3CaSO 4 ·32H 2 O. Ettringite is formed in the hydrated Portland cement system as a result of the reaction of tricalcium aluminate (C 3 A) with calcium sulfate, both ...