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 dialuminate, CaO·2Al2O3 (CA2) (occurring in nature as grossite [5])
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.
Tetracalcium trialuminate, 4CaO·3Al2O3 (C4A3), is a metastable phase formed by dehydrating 4CaO·3Al2O3·3H2O (C4A3H3).
Ye'elimite, C4A3S̅, a rare natural anhydrous calcium sulfoaluminate
References
^Hosono, H.; Tanabe, K.; Takayama-Muromachi, E.; Kageyama, H.; Yamanaka, S.; Kumakura, H.; Nohara, M.; Hiramatsu, H.; Fujitsu, S. (2015). "Exploration of new superconductors and functional materials, and fabrication of superconducting tapes and wires of iron pnictides". Science and Technology of Advanced Materials. 16 (3): 033503. arXiv:1505.02240. Bibcode:2015STAdM..16c3503H. doi:10.1088/1468-6996/16/3/033503. PMC 5099821. PMID 27877784.
^Taylor H.F.W (1990) Cement Chemistry, Academic Press, ISBN 0-12-683900-X, pp. 34–38.
^"Mayenite Supergroup".
^"Krotite".
^"Grossite".
^"Hibonite".
^Taylor H.F.W (1990) Cement Chemistry, Academic Press, ISBN 0-12-683900-X, pp. 28, 29.
^"Brownmillerite".
Further reading
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. eISSN 1551-2916. ISSN 0002-7820.