The suitability of cement for a certain purpose is tested by means of an apparatus shown in the figure. It consists of a glass plate and a vicat needle. A paste of cement is made placed on the glass plate. The vicat needle is allowed to drop under its own weight. At first the needle can pierce the cement and touch the glass plate. But as the time passes, it fails to do so. The time at this stage is noted.
This interval of time since the start is called “initial setting time”. The experiment is continued until cement sets and it becomes difficult to take out the needle. The time at this stage is also noted and is called “final setting time”. For a good type of cement, the initial setting time should not be less than 45 minutes and the final setting time not more than 10 hours. The quality of cement can also be tested by means of the following characteristics of cement.