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.
Monocalcium hexa-aluminate, CaO·6Al2O3 (CA6) (occurring in nature as hibonite, a representative of magnetoplumbite group[6])
In addition, other phases include:
Dicalcium aluminate, 2CaO·Al2O3 (C2A), which exists only at pressures above 2500 MPa.[7] The crystal is orthorhombic, with density 3480 kg·m−3. The natural dicalcium aluminate, brownmillerite, may form at normal pressure but elevated temperature in pyrometamorphic zones, e.g., in burning coal-mining heaps.[8]
Pentacalcium trialuminate, 5CaO·3Al2O3 (C5A3), forms only under an anhydrous and oxygen free atmosphere. The crystal is orthorhombic, with a density of 3067 kg·m−3. It reacts rapidly with water.
Buttler, F. G.; Dent Glasser, L. S.; Taylor, H. F. W. (March 1959). "Studies on 4CaO·Al2O3·13H2O and the related natural mineral hydrocalumite". Journal of the American Ceramic Society. 42 (3): 121–126. doi:10.1111/j.1151-2916.1959.tb14078.x. eISSN1551-2916. ISSN0002-7820.
