Calcium aluminates
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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.
The stable phases shown in the phase diagram (formed at atmospheric pressure under an atmosphere of normal humidity) are:
- Tricalcium aluminate, 3CaO·Al2O3 (Page Module:Chem2/styles.css has no content.C3A)
- Dodecacalcium hepta-aluminate, 12CaO·7Al2O3 (Page Module:Chem2/styles.css has no content.C12A7) (once known as mayenite[3])
- Monocalcium aluminate, CaO·Al2O3 (CA) (occurring in nature as krotite and dmitryivanovite – two polymorphs[4])
- [[Template:Chem name]], CaO·2Al2O3 (Page Module:Chem2/styles.css has no content.CA2) (occurring in nature as grossite [5])
- Monocalcium hexa-aluminate, CaO·6Al2O3 (Page Module:Chem2/styles.css has no content.CA6) (occurring in nature as hibonite, a representative of magnetoplumbite group[6])
In addition, other phases include:
- Dicalcium aluminate, 2CaO·Al2O3 (Page Module:Chem2/styles.css has no content.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]
- [[Template:Chem name]], 5CaO·3Al2O3 (Page Module:Chem2/styles.css has no content.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.
- [[Template:Chem name]], 4CaO·3Al2O3 (Page Module:Chem2/styles.css has no content.C4A3), is a metastable phase formed by dehydrating 4CaO·3Al2O3·3H2O (Page Module:Chem2/styles.css has no content.C4A3H3).
Hydration reaction
In contrast to Portland cements, calcium aluminates do not release calcium hydroxide (Page Module:Chem2/styles.css has no content.Ca(OH)2) portlandite or lime during their hydration.
See also
- Calcium aluminate cements
- Cement
- Cement chemist notation (CCN)
in which the following abbreviations for calcium and aluminium oxides are defined as:- C = CaO
- A = Page Module:Chem2/styles.css has no content.Al2O3
- Hydrocalumite
- Mayenite
- Ye'elimite, Page Module:Chem2/styles.css has no content.C4A3S̅, a rare natural anhydrous calcium sulfoaluminate
References
Page Template:Reflist/styles.css has no content.
- ^ Page Module:Citation/CS1/styles.css has no content.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, Template:ISBN, pp. 34–38.
- ^ Page Module:Citation/CS1/styles.css has no content."Mayenite Supergroup".
- ^ Page Module:Citation/CS1/styles.css has no content."Krotite".
- ^ Page Module:Citation/CS1/styles.css has no content."Grossite".
- ^ Page Module:Citation/CS1/styles.css has no content."Hibonite".
- ^ Taylor H.F.W (1990) Cement Chemistry, Academic Press, Template:ISBN, pp. 28, 29.
- ^ Page Module:Citation/CS1/styles.css has no content."Brownmillerite".
Further reading
Page Template:Refbegin/styles.css has no content.
- Page Module:Citation/CS1/styles.css has no content.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.
