What are the Initial and Final Setting Time of Cement.

Initial Setting Time of Cement.

Initial setting time of cement is defined as the time elapsed between the moments when water is added to the cement to the time when the cement paste starts losing its plasticity. It can also be defined as the time elapsed between the moments when water is added to the cement to the time when the Vicat square needle penetrates a depth of 33-35 mm from the top (5 to 7 mm from the bottom) of the mould of the Vicat Apparatus.

Final Setting Time of Cement

Final setting time of cement can be defined as the time elapsed between the moments when water is added to the cement to the time when the cement paste has completely lost its plasticity. Final setting time of cement can also be defined as the time elapsed between the moments when water is added to the cement to the time when square needle makes impression on the paste, while the annular collar fails to do so.

Vicat Apparatus Test For Initial Setting Time of Cement

The device which is used to find the initial setting time of cement is called as Vicat apparatus. It has a square needle of 1 mm size and 50 mm length and a mould, which is 40 mm in height and 80 mm in diameter.

Test Procedure:

• A cement paste is prepared by mixing water 0.85P% by weight of cement.
• The time of mixing should not be less than 3 minutes and should not be more than 5 minutes.
• After proper mixing the paste is filled in the vicat mould and the top surface is levelled properly.
• The mould is then placed under square needle and this needle is slowly brought down to touch the surface of the paste.
• Now the square needle is suddenly released and allowed to sink into the cement paste by its own weight.
• The depth of penetration of the square needle in the paste is noted down.
• The whole experiment is repeated with incremental time intervals until such a time when the square needle is penetrated to a depth of 33 to 35 mm from the top of the mould.
• The time elapsed between the moments when water is added to the cement to the time when the square needle penetrates a depth of 33 to 35 mm from the top of the mould is known as the Initial Setting Time of that cement.
• The initial Setting Time should not be less than 30 minutes for Ordinary Portland Cement.

Also Read : Cement Concrete Specification for Design Mix 1:2:4

Vicat Apparatus Test For Final Setting Time of Cement

The apparatus used for the final setting time of cement test is same as that of used for the test of initial setting time of cement.

Test Procedure :

• A cement paste is prepared by adding water 0.85P% by weight of cement.
• The time of mixing should not be less than 3 minutes and should not be more than 5 minutes.
• Now the paste is filled in the Vicat mould and the top is levelled off.
• The mould is now placed under the square needle with annular collar and is brought down touch the surface of the paste.
• Now the square needle with annular collar is suddenly released and allowed to make on impression on the cement paste by its own weight.
• The impression made by this square needle with annular collar is observed.
• The whole experiment is repeated with incremental time intervals until such a time when the square needle makes an impression on the paste while the annular collar fails to do so.
• The time elapsed between the moments when water is added to the cement to the time when the square needle makes an impression on the paste while the annular collar fails to do so is known as the Final Setting Time of the cement.
• The final setting time of cement should not be more than 600 minutes for Ordinary Portland Cement.

Also Read : Workability of Concrete & Factors Affecting It