Introduction
Portland cement gets its strength from chemical reactions between the
cement and water. The process is known as hydration.
This is a complex process that is best understood by first understanding
the chemical composition of cement.
Manufacture of cement
Portland cement is manufactured by crushing, milling and proportioning
the following materials:
Chemical shorthand
Because of the complex chemical nature of cement, a shorthand form
is used to denote the chemical compounds. The shorthand for the basic compounds
is:
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Calcium oxide (lime) |
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Silicon dioxide (silica) |
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Aluminum oxide (alumina) |
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Iron oxide |
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Water |
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Sulfate |
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Tricalcium aluminate | Ca3Al2O6 | C3A | 10 |
Tetracalcium aluminoferrite | Ca4Al2Fe2O10 | C4AF | 8 |
Belite or dicalcium silicate | Ca2SiO5 | C2S | 20 |
Alite or tricalcium silicate | Ca3SiO4 | C3S | 55 |
Sodium oxide | Na2O | N | )
)Up to 2 |
Potassium oxide | K2O | K | |
Gypsum | CaSO4.2H2O | CSH2 | 5 |
Properties of cement compounds
These compounds contribute to the properties of cement in different
ways
By mixing these compounds appropriately, manufacturers can produce different types of cement to suit several construction environments.
References:
Sidney Mindess & J. Francis Young (1981): Concrete, Prentice-Hall,
Inc., Englewood Cliffs, NJ, pp. 671.
Steve Kosmatka & William Panarese (1988): Design and Control of Concrete Mixes, Portland Cement Association, Skokie, Ill. pp. 205.
Michael Mamlouk & John Zaniewski (1999): Materials for Civil and Construction Engineers, Addison Wesley Longman, Inc.,