The main oxides present in cement (or in glass and ceramics) are abbreviated in the following way: For the sake of mass balance calculations, hydroxides present in hydrated phases found in hardened cement paste, such as in portlandite, Ca(OH)2, must first be converted into oxide and water.
To better understand the conversion process of hydroxide anions in oxide and water, it is necessary to consider the autoprotolysis of the hydroxyl anions; it implies a proton exchange between two OH−, like in a classical acid–base reaction: or also, For portlandite this gives thus the following mass balance: Thus portlandite can be written as CaO · H2O or CH.
To avoid the flash setting of concrete, due to the very fast hydration of the tricalcium aluminate (C3A), 2–5 wt.
This is why the reaction leads to the elimination of the excess of portlandite (Ca(OH)2) and brucite (Mg(OH)2), respectively, out of the silicate system, giving rise to the crystallization of both hydroxides as separate phases.
This comparison suggests that mineralogists could probably also benefit from the concise formalism of the cement chemist notation in their works.