3.2    Note on cement chemistry notation and mineral names

     At the high temperatures present in a cement kiln, all of the constituents of the raw ingredients are either driven off as a gas or converted to an oxide form.  To make the formulas of cement minerals, compounds, and reactions shorter and easier to read, it is traditional to use a shorthand notation that leaves out the oxygen.  This system is listed in Table 3.1.

Table 3.1: Cement chemistry notation based on oxides.

Oxide form

Notation

CaO

C

SiO2

S

Al2O3

A

Fe2O3

F

SO3

H2O

H


     Other abbreviations are also in use, such as MgO=M and Na2O = N, but only those listed above in Table 3.1 will be used in this monograph.  While this system has definite advantages, it does take some getting used to, since, for example, C normally stands for carbon and H normally stands for hydrogen.

     Unfortunately the confusion does not end there, as we also have to deal with chemical and mineral names for solid phases.  The chemical name of a solid compound is simply the word version of the chemical formula, for example “calcium hydroxide”.  The mineral name (in this case “portlandite”) is meant to represent either a particular crystal structure or a potentially impure form of the phase.  The various ways of describing some of the main solid phases associated with cement chemistry are summarized in Table 3.2.  In this monograph we will use primarily the chemical name and the cement notation.  In the case of the cement minerals, this is actually a bit inaccurate.  Names such as alite and belite indicate a particular crystal structure  as well as the fact that these phases contain a variety of impurities when found in cement. 

Table 3.2: Summary of the different ways to represent some cement minerals and products.

Chemical Name

Chemical Formula

Oxide Formula

Cement Notation

Mineral Name

Tricalcium Silicate

Ca3SiO5

3CaO.SiO2

C3S

Alite

Dicalcium Silicate

Ca2SiO4

2CaO.SiO2

C2S

Belite

Tricalcium Aluminate

Ca3Al2O6

3CaO.Al2O3

C3A

Aluminate

Tetracalcium Aluminoferrite

Ca2AlFeO5

4CaO.Al2O3.Fe2O3

C4AF

Ferrite

Calcium hydroxide

Ca(OH)2

CaO.H2O

CH

Portlandite

Calcium sulfate dihydrate

CaSO4.2H2O

CaO.SO3.2H2O

C H2

Gypsum

Calcium oxide

CaO

CaO

C

Lime


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