LAB TEST FOR DETERMINATION OF CONSISTENCY OF CEMENT PASTE

OBJECTIVE: to determine the quantity of water required producing a cement paste of standard consistency.

APPARATUS: balance of 0.1gm accuracy, vicat’s apparatus with plunger, standard weights, graduated glass measuring jar and gauging trowel.

PROCEDURE:

1.      Determination of consistency of cement paste

2.      Code of practise: is 4031 (part4)-1993-first reprint

3.      Objective: to determine the quantity of water required producing a cement paste of standard consistency.

4.      Apparatus: balance of 0.1gm accuracy: vicat’s apparatus with plunger : standard weights : graduated glass measuring jar and gauging trowel.

5.      Procedure:

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

7.      Take 300gm of cement in evaporation dish and mix water of about 25% by the weight of cement.

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

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

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

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

12.  Place it below plunger, allow it to sink into the paste and record the penetration of plunger from the bottom of the mould.

13.  If this is not in between 5-7mm, take a fresh sample of dry cement of same weight and add little more water and repeat the test.

14.  Repeat the above test with increased water content until the penetration of plunger in the cement paste in between 5 to 7 mm.

Therefore, the standard consistency of cement paste is the percentage of water required, where the plunger penetrates into to cement paste of about 5 to 7 mm from the bottom of the mould.