An AFm phase is an "alumina, ferric oxide, monosubstituted" phase, or aluminate ferrite monosubstituted, or , 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 , where: CaO, , 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 (, …) with y = 1, or;– monovalent (, …) with y = 2. n represents the number of water molecules in the hydrate and may be comprised between 13 and 19. AFm form inter alia when tricalcium aluminate in CCN, reacts with dissolved calcium sulfate () or calcium carbonate (). 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 Further reading Aluminium compounds Cement Concrete Hydrates Iron compounds Iron(III) compounds Silicates Sulfate minerals Sulfates