Cement chemist notation


Cement chemist notation 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.

Abbreviations of oxides

The main oxides present in cement are abbreviated in the following way:
CCNActual formulaName
CCaOCalcium oxide, or lime
SSiO2Silicon dioxide, or silica
AAl2O3Aluminium oxide, or alumina
FFe2O3Iron oxide, or rust
TTiO2Titanium dioxide, or titania
MMgOMagnesium oxide, or periclase
KK2OPotassium oxide
NNa2OSodium oxide
HH2OWater
CO2Carbon dioxide
SO3Sulfur trioxide
PP2O5Phosphorus hemi-pentoxide

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, Ca2, 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.

Main phases in Portland cement before and after hydration

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 in the cement kiln and are the following:
CCNActual formulaNameMineral phase
C3S3 CaO · SiO2Tricalcium silicateAlite
C2S2 CaO · SiO2Dicalcium silicateBelite
C3A3 CaO · Al2O3Tricalcium aluminateAluminate or Celite
C4AF4 CaO · Al2O3 · Fe2O3Tetracalcium alumino ferriteFerrite

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.

Hydrated cement paste

products formed in hardened cement pastes 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:
CCNActual formulaName or mineral phase
CHCa2 or CaO · H2OCalcium hydroxide
C-S-H0.6–2.0 CaO · SiO2 · 0.9–2.5 H2O, with variable composition within this range, and often also incorporating partial substitution of Al for SiCalcium silicate hydrate
C-A-HThis is even more complex than C-S-HCalcium aluminate hydrate
AFtC6A3H32, sometimes with substitution of Fe for Al, and/or Carbonate| for Sulfate|calcium trisulfoaluminate hydrate, or ettringite
AFmC4AH12, often with substitution of Fe for Al, and/or various other anions such as OH− or for Calcium monosulfoaluminate
C3AH63CaO · Al2O3 · 6 H2OHydrogarnet

The hyphens in C-S-H indicate a calcium silicate hydrate phase of variable composition, while 'CSH' would indicate a calcium silicate phase, CaH2SiO4.

Use in ceramics, glass, and oxide chemistry

The cement chemist notation is not restricted to cement applications but is in fact a more general notation of oxide chemistry applicable to other domains than cement chemistry sensu stricto.
For instance, in ceramics applications, the kaolinite formula can also be written in terms of oxides, thus the corresponding formula for kaolinite,
is
or in CCN

Possible use of CCN in mineralogy

Although not a very developed practice in mineralogy, some chemical reactions involving silicate and oxide in the melt or in hydrothermal systems, and silicate weathering processes could also be successfully described by applying the cement chemist notation to silicate mineralogy.
An example could be the formal comparison of belite hydration and forsterite serpentinisation dealing both with the hydration of two structurally similar earth -alkaline silicates, Ca2SiO4 and Mg2SiO4, respectively.
;Calcium system: belite hydration:
;Magnesium system: forsterite serpentinisation:
The ratio Ca/Si and Mg/Si decrease from 2 for the dicalcium and dimagnesium silicate reagents to 1.5 for the hydrated silicate products of the hydration reaction. In other term, the C-S-H or the serpentine are less rich in Ca and Mg respectively. This is why the reaction leads to the elimination of the excess of portlandite and brucite, respectively, out of the silicate system, giving rise to the crystallization of both hydroxides as separate phases.
The rapid reaction of belite hydration in the setting of cement is formally "chemically analogue" to the slow natural hydration of forsterite leading to the formation of serpentine and brucite in nature. However, the kinetic of hydration of poorly crystallized artificial belite is much swifter than the slow conversion/weathering of well crystallized Mg-olivine under natural conditions.
This comparison suggests that mineralogists could probably also benefit from the concise formalism of the cement chemist notation in their works.