Cement chemist notation
Cement chemist notation (CCN) was developed to simplify the formulas cement chemists use on a daily basis. It is a shorthand way of writing the chemical formula of oxides of calcium, silicon, and various metals.
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.
These oxides are used to build more complex compounds. The main crystalline phases described hereafter are related respectively to the composition of:
Four main phases are present in the clinker and in the non-hydrated Portland cement.
They are formed at high temperature (1,450 °C) in the cement kiln and are the following:
The four compounds referred as C3S, C2S, C3A and C4AF are known as the main crystalline phases of Portland cement. The phase composition of a particular cement can be quantified through a complex set of calculation known as the Bogue formula.
Hydration products formed in hardened cement pastes (also known as HCPs) are more complicated, because many of these products have nearly the same formula and some are solid solutions with overlapping formulas. Some examples are given below:
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