BOGUES COMPOUND IN CEMENT

When water is added to cement the ingredients of cement react chemically with water and form various complicated chemical compounds terms as Bogues compund. The formation of these compounds are not simultaneous. Following are the important chemical compound formed during setting action of cement:

S.No.	Chemical Name	Chemical Formula	Notation	Percentage (%)
1	Tricalcium Silicate	3CaO, SiO2	C3S	30-50
2	Dicalcium Silicate	2CaO, SiO2	C2S	20-45
3	Tricalcium Aluminate	3CaO, Al2O3	C3A	8-12
4	Tetra-calcium Alumino-ferrite	4CaO, Al2O3, Fe2O3	C4AF	6-10

(1). Tricalcium Silicate (C3S):

• Formed within about 24 hours after addition of water to cement.
• Responsible for initial set and early strength of cement.
• It produces more heat of hydration.
• Higher percentage of C3S will exhibit higher early strength.
• A cement with more C3S is better for cold weather concreting. 

(2). Dicalcium Silicate (C2S):

• The hydration of C2S starts after 7 days, hence it gives strength after 7 days.
• Formed very slowly and responsible for giving progressive strength to the cement.
• It produces less heat of hydration.
• Hydrates and hardens slowly and provide much of the ultimate strength.
• It is responsible for the later strength of concrete.
• Greater resistant to chemical attack.  

(3). Tricalcium Aluminate (C3A):

• Formed within a week or so after addition of water to the cement.
• Hydrates and hardens the quickest.
• Maximum evolution of heat of hydration.

(4). Tetra-Calcium Alumino-ferrite (C4AF):

• Formed within about 24 hours after addition of water to cement.
• High heat of hydration in initial period. 
• It does not contribute to the strength of concrete.
• Hydrates of C4AF show higher resistance to sulphate attack than the hydrates of C3A.