Question

if I am not present in the cement it will get hard very fast what is my common name and molecular formula​

Answer 1

Calcium Sulfate: Chemical formula is CaSO4

1.    This is present in cement in the form of gypsum(CaSO4.2H2O).
2.    It slows down or retards the setting action of cement.

Answer 2

Answer:

plaster of paris

formula

2h2o