Table of Contents

CEMENT COMPOSITION

Cement composition is the raw material proportion used in the manufacturing of good quality cement comply with IS 8112 : 1998 of 43 grade OPC and IS 469 for 33 grade.

Cement Raw Materials

Cement production mainly consist of Argillaceous and Calcareous raw Material

Argillaceous Materials – silica, alumina and oxides of iron.

Calcareous Material – compounds of calcium and magnesium.

Chemical Composition requirement by IS for OPC (Ordinary Portland Cement)

For the production of OPC 43 Grade, manufacturer should follow the recommendation of Indian standard code IS 8112 : 1998

Ratio of percent of lime to percentage of silica, alumina and iron oxide should not greater than 1.02 and not less than 0.66 when calculated by the formula

Alumina and iron oxide ratio should not less than 0.66

Insoluble residue not more than 2 percent by mass

Magnesia should not more than 6 percent by mass

Total sulphur (SO3) content should not more than 2.5 percent when tricalcium aluminate is below or equal to 5 percent otherwise 3 percent of SO3 if tricalcium aluminate is more than 5 percent by mass.

Total loss of ignition should not more than 5 percent

Here tricalcium aluminate is calculate by the formula

Composition by Weight

Chemical composed of	Formula	Short form	% by weight
Tri-calcium aluminate	Ca₃Al₂O₆	C₃A	10 %
Tetra-calcium alumino ferrite	Ca₄Al₂Fe₂O₁₀	C₄AF	8 %
Di-calcium silicate	Ca₂SiO₅	C₂S	20 %
Tri-calcium silicate	Ca₃SiO₄	C₃S	55 %
Sodium oxide	Na₂O	N	2 %
Potassium oxide	K₂O	K	2 %
Gypsum	CaSO_4.2H₂O	CSH₂	5

Tricalcium aluminate ( Ca₃Al₂O₆)is responsible for the initial setting and high heat of hydration.

Gypsum is used in the cement as a retarder to increase the initial setting time, but this could not be more than 5 percent otherwise it could cause the strength of cement.

Chemical Ingredients by Weight Percent

Lime (CaO)	60 to 67%
Silica (SiO2)	17 to 25%
Alumina (Al2O3)	3 to 8%
Iron oxide (Fe2O3)	0.5 to 6%
Magnesia (MgO)	0.1 to 4%
Sulphur trioxide (SO3)	1 to 3%
(Na2O+K2O) Soda / Potash	0.5 to 1.3%