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
|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 %|
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%|