LAB TEST FOR DETERMINATION OF INITIAL AND FINAL SETTING TIME OF CEMENT

OBJECTIVE: To determine initial and final setting time.

APPARATUS: balance of 0.1gm accuracy, vicat apparatus with needle and annular attachment, standard weights, gauging trowel, graduated glass measuring and stop watch.

PROCEDURE:

1.      Take a representative cement sample to be tested with a sample driver.

2.      Take 300gm of cement in evaporation dish and mix water of about 0.85 times that is required to form a cement paste of standard consistency by the weight of cement.

3.      Switch on the exactly at the moment water added to cement.

4.      Care shall be taken that the mixing time is not less than 3 minutes or not more than 5minutes for the time of water adding to the dry cement.

5.      Place the mould of the vicat’s apparatus on a non-porous plate and fill the mould with paste.

6.      After filling, smoothen the surface of the paste, making it level with the top of the mould.

7.      Shake the mould slightly to expel the entrapped air.

8.      Place it below needle of vicat apparatus and lower the needle gently to touch the surface of the test block.

9.      Quickly release the needle, allow it to sink into the paste and record the penetration of needle from the bottom of the mould.

10.  If it is not in between 5+-5mm,allowit to remain there without any disturbance or vibrations and check the penetration into the cement paste at frequent intervals of time.

11.  Since it required to access the final setting time, do not stop the stopwatch.

12.  Initial setting time is the time taken for the needle to have a penetration of 5+-0.5mm from the bottom of mould, from the time of water added to dry cement.

*Remove the needle and attach the needle with the annular attachment to the vicat apparatus.

13.  Lower the needle with the annular attachment gently to touch to the surface of the test block.

14.  Observe the impression made by the needle with annular attachment.

15.  If the impression made only by needle the cement said to be final set,if not allow it to remain there without any disturbances or vibrations, and check the impression made on the cement paste at frequent interval of time.

16.  Final setting time is the elapsed time between the time when water added to the dry cement to the time when the needle makes an impression on the surface of the test block and annular attachment fails to do so.