Chemical Requirements of Cement

1) Insoluble Residue :-
                       The insoluble material is an inactive part of cement. It should be minimum quantity. The maximum permissible value of the insoluble residue for different types of cement not more than 2%.
2) Magnesia[MgO] :-
                      Unsoundness of cement is largely due to the presence of free magnesia which hydrates slowly causing expansion. Its quantity, should not be more than 6%.
3) Sulphur :-
                     The total sulphur content calculated as sulphuric-anhydride is produced due to the presence of gypsum. It causes expansion and consequently unsoundness. The maximum permissible value of this compound in cement should not be more than 2.75%.
4) Loss of Ignition :-
                     When the cement is heated it loses its weight. The loss in weight occurs as the moisture and co2, which are present in combination with free lime or magnesia evaporate. The loss in weight is a measure of the freshness of the cement. The loss on ignition of cement should not be more than 4%.