Calcium aluminates
Encyclopedia
Calcium oxide
Calcium oxide , commonly known as quicklime or burnt lime, is a widely used chemical compound. It is a white, caustic, alkaline crystalline solid at room temperature....
and aluminium oxide
Aluminium oxide
Aluminium oxide is an amphoteric oxide with the chemical formula 23. It is commonly referred to as alumina, or corundum in its crystalline form, as well as many other names, reflecting its widespread occurrence in nature and industry...
together at high temperatures. They are encountered in the manufacture of refractories
Refractory
A refractory material is one that retains its strength at high temperatures. ASTM C71 defines refractories as "non-metallic materials having those chemical and physical properties that make them applicable for structures, or as components of systems, that are exposed to environments above...
and cement
Cement
In 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...
s.
The stable phases shown in the phase diagram
Phase diagram
A phase diagram in physical chemistry, engineering, mineralogy, and materials science is a type of chart used to show conditions at which thermodynamically distinct phases can occur at equilibrium...
(formed at atmospheric pressure
Atmospheric pressure
Atmospheric pressure is the force per unit area exerted into a surface by the weight of air above that surface in the atmosphere of Earth . In most circumstances atmospheric pressure is closely approximated by the hydrostatic pressure caused by the weight of air above the measurement point...
under an atmosphere of normal humidity
Relative humidity
Relative humidity is a term used to describe the amount of water vapor in a mixture of air and water vapor. It is defined as the partial pressure of water vapor in the air-water mixture, given as a percentage of the saturated vapor pressure under those conditions...
) are:
- 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...
, 3CaO·Al2O3 (C3A) - Dodecacalcium hepta-aluminateDodecacalcium hepta-aluminateDodecacalcium hepta-aluminate occurs rarely in nature as the mineral mayenite. It is an important mineral phase in Calcium aluminate cements and is an intermediate in the manufacture of Portland cement...
, 12CaO·7Al2O3 (C12A7) - Monocalcium aluminateMonocalcium aluminateMonocalcium aluminate is one of the series of calcium aluminates. It does not occur in nature, but is important in the composition of calcium aluminate cements.-Properties:...
, CaO·Al2O3 (CA) - Monocalcium dialuminate, CaO·2Al2O3 (CA2)
- Monocalcium hexa-aluminate, CaO·6Al2O3 (CA6)
In addition, other phases include:
- Dicalcium aluminate, 2CaO·Al2O3 (C2A), which exists only at pressures above 2500 MPa. The crystal is orthorhombic, with density 3480 kg·m−3.
- Pentacalcium trialuminate, 5CaO·3Al2O3 (C5A3), forms only under an anhydrousAnhydrousAs a general term, a substance is said to be anhydrous if it contains no water. The way of achieving the anhydrous form differs from one substance to another...
and oxygen free atmosphere. The crystal is orthorhombic, with a density of 3067 kg·m−3. It reacts rapidly with water. - Tetracalcium trialuminate, 4CaO·3Al2O3 (C4A3), is a metastable phase formed by dehydratingDehydrationIn physiology and medicine, dehydration is defined as the excessive loss of body fluid. It is literally the removal of water from an object; however, in physiological terms, it entails a deficiency of fluid within an organism...
4CaO·3Al2O3·3H2O (C4A3H3).
See also
- 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...
- Cement chemist notationCement chemist notationCement 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:...
(CCN)
in which the following abbreviations for calcium and aluminium oxides are defined as:- C = CaO
- A = Al2O3