Basic Properties of Bouge Compounds | C3S, C2S, C3A, C4AF2 min read

These are the 4 principle mineral compound in portland cement

  1. Tri-calcium silicate
  2. Di-calcium silicate
  3. Tri-calcium alluminate
  4. Tetra-calcium alumino ferrite

1. Tri-calcium silicate (C3S)

The formula is 3CaOSiO2 and the symbol of Tri-calcium silicate is C3S

It is known as Alite

This compound is in the range of 30-50%

It produces a faster rate of reaction with greater heat evolution, imparts early strength to the cement, and also contributes well to ultimate strength. If it is in excess then rapid hardening enhances.

2. Di-calcium Silicate (C2S)

The formula is 2CaOSiO2 and the symbol of Tri-calcium silicate is C2S

It is known as Belite

This compound is in the range of 20-45%

It hydrates slowly and imparts ultimate strength. The C2S has less heat of hydration therefore it is resistant to chemical attack.

3. Tri-calcium Aluminate (C3A)

The formula is 3CaOAl2O3 and the symbol of Tri-calcium silicate is C3A

It is known as Celite

This compound is in the range of 8-12%

It imparts a fast reaction with water and it produces very high heat therefore it imparts more towards rapid hardening.

If C3A would be more than an immediate setting (flash set) would be enhanced to prevent this flash setting gypsum is added to it during manufacturing.

4. Tetra-calcium alumino ferrite (C4AF)

The formula is 4CaOAl2O3 Fe2O3 and the symbol of Tri-calcium silicate is C4AF

It is known as Felite

This compound is in the range of 6-10%

It also reacts with water at a faster rate and evolves heat to a greater extent but it is more stable than C3A because it produces if produces less heat compared to C3A.

 

The principle mineral compounds in portland cement Formula NameĀ  Symbol Percentage
1. Tri-calcium silicate 3CaOSiO2 Alite C3S 30-50%
2. Di-calcium silicate 2CaOSiO2 Belite C2S 20-45%
3. Tri-calcium alluminate 3CaOAl2O3 Celite C3A 8-12%
4. Tetra-calcium alumino ferrite 4CaOAl2O3 Fe2O3 Felite C4AF 6-10%

 

FAQS
  • Decreasing order of ultimate: (C2S > C3S > C3A > C4AF)

Decreasing order of quickest reaction with water: (C3A > C4AF > C3S >C2S)

  • The rate of hydration is increased by an increase in the fineness of the cement. However, total heat evolved is the same. The rate of hydration of the principal compounds will be in the following descending order

C4AF > C3A > C3S > C2S

  • The rate of heat evolution of Bougue compound, if an equal amount of each is considered will be in the following descending order
    C3A (865 J/gm) > C3S (865 J/gm) > C3AF (420 J/gm) > C2S (260 J/gm)
  • The initial setting time of cement depends most on Tri-calcium aluminate

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