Initial Setting Time:

An initial setting time is the interval between the addition of water to cement and the stage when needle (1 mm square; 40 to 50 mm length) fails to pierce the test block by about 5 mm from the bottom.

The cement of weight 400 gm is taken and it is mixed with 0.85 P percentage of water where P is the % of water as determined in consistency test. The cement paste is filled in the Vicat mould. The square needle of cross section 1 mm × 1 mm called as initial setting time needle is attached to the moving rod of the Vicat apparatus. The needle is rapidly released and it is permitted to penetrate the cement paste. In the starting, the needle penetrates fully. It is then taken out and dropped at a fresh place. The process is repeated until the needle fails to pierce the cement paste in block for about 5 mm that was measured from the bottom of the mould. The time therefore recorded shall be the initial setting time. The care should be taken that each time the needle should be cleaned and released at a new place, on the top surface of the paste. The time from the readings and stopwatch from the scale should be recorded continuously.