AFm phase
An AFm phase is an "alumina, ferric oxide, monosubstituted" phase, or aluminate ferrite monosubstituted, or Al2O3, Fe2O3 mono, in cement chemist notation (CCN). AFm phases are important hydration products in the hydration of hydraulic cements.
They are crystalline hydrates with generic, simplified, formula 3CaO·(Al,Fe)2O3·CaXy·nH2O,
where:
- CaO, Al2O3, Fe2O3 represent calcium oxide, aluminium oxide, and ferric oxide, respectively;
- CaX represents a calcium salt, where X replaces an oxide ion;
- X is the substituted anion in CaX:
– divalent (SO2−4, CO2−3…) with y = 1, or;
– monovalent (OH−, Cl−…) with y = 2. - n represents the number of water molecules in the hydrate and may be comprised between 13 and 19.[1]
AFm form inter alia when tricalcium aluminate 3CaO·Al2O3, or C3A in CCN, reacts with dissolved calcium sulfate (CaSO4) or calcium carbonate (CaCO3). As the sulfate form is the dominant one in AFm phases, it is often referred to as Aluminate Ferrite monosulfate or calcium aluminate monosulfate. However, carbonate-AFm phases also exist: monocarbonate and hemicarbonate.
See also
- Concrete degradation#Chloride attack
- Layered double hydroxides (LDH)
- Friedel's salt
- Ettringite (AFt)
- Pitting corrosion of rebar induced by chloride attack
References
- Matschei, T.; Lothenbach, B.; Glasser, F. P. (2007-02-01). "The AFm phase in Portland cement". Cement and Concrete Research. 37 (2): 118–130. doi:10.1016/j.cemconres.2006.10.010. ISSN 0008-8846. Retrieved 2022-02-10.
Further reading
- Hirao, Hiroshi; Yamada, Kazuo; Takahashi, Haruka; Zibara, Hassan (2005). "Chloride binding of cement estimated by binding isotherms of hydrates". Journal of Advanced Concrete Technology. 3 (1): 77–84. doi:10.3151/jact.3.77. eISSN 1347-3913. ISSN 1346-8014. Retrieved 2022-02-19.
- Galan, Isabel; Glasser, Fredrik P. (2015-02-01). "Chloride in cement". Advances in Cement Research. 27 (2): 63–97. doi:10.1680/adcr.13.00067. eISSN 1751-7605. ISSN 0951-7197. Retrieved 2022-02-19.
- Baquerizo, Luis G.; Matschei, Thomas; Scrivener, Karen L.; Saeidpour, Mahsa; Wadsö, Lars (2015-07-01). "Hydration states of AFm cement phases". Cement and Concrete Research. 73: 143–157. doi:10.1016/j.cemconres.2015.02.011. ISSN 0008-8846. Retrieved 2022-02-10.
- Feng, Pan; Miao, Changwen; Bullard, Jeffrey W. (2016-03-01). R. Riman (ed.). "Factors influencing the stability of AFm and AFt in the Ca – Al – S – O – H System at 25 °C". Journal of the American Ceramic Society. 99 (3): 1031–1041. doi:10.1111/jace.13971. ISSN 1551-2916. PMC 4911640. PMID 27335503.
- Nedyalkova, Latina; Tits, Jan; Renaudin, Guillaume; Wieland, Erich; Mäder, Urs; Lothenbach, Barbara (2022-02-15). "Mechanisms and thermodynamic modelling of iodide sorption on AFm phases". Journal of Colloid and Interface Science. 608 (Pt 1): 683–691. Bibcode:2022JCIS..608..683N. doi:10.1016/j.jcis.2021.09.104. ISSN 0021-9797. PMID 34634544. S2CID 238637368.
This article is issued from Wikipedia. The text is licensed under Creative Commons - Attribution - Sharealike. Additional terms may apply for the media files.