Conversion of Hydroxides in Oxide and Free Water
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 in 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:
- OH– + OH– → O2– + H2O
- acid 1 + base 2 → base 1 + acid 2
or also,
- 2 OH– → O2– + H2O
For portlandite this gives thus the following mass balance:
- Ca(OH)2 → CaO + H2O
Thus portandite can be written as CaO • H2O or CH.
Read more about this topic: Cement Chemist Notation
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