Chemical Requirement of Cement

Chemical composition of ordinary or rapid-hardening cements when tested accroding to IS : 4032 - 1968 should be as follows :

1. Ratio of percentage of lime to percentage of silica , alumina and iron oxide when calculated by formula ,

  CaO - 0.7 SO3 / 2.8 SiO2 + 1.2 Ai2 O3 + 0.65 Fe2 O3
2. Weight of insoluble residue  not more than 1.5 percent
3. weight of magnesia   not more than 6 percent
4. Ratio of percentage of alumina to that of iron oxide  not less than 0.66
5. Total sulphur content in form of S03  not more than 2.75 percent
6. Total loss on ignition     not more than 4 percent

In the case of low heat cement the percentage of lime , after deduction of that necessary to combine with sulphuric anhydride ( S03) , present in cement shall be as follows :

  Not more than  2.4 SiO 2 + 1.2  A12o3  + 0.65 Fe2O3

  In all other chemical composition , low heat cement shall comply the requirements specified in 2, 3 , 4, 5 , and 6