Consistency Test of Cement

Consistency test is performed to determine the quantity of water required to produce a cement paste of standard consistency. It is essential to fix the quantity of water to be mixed with cement to perform test such as Initial and Final setting time of cement, soundness test, compressive strength test of cement etc. Therefore, one has to perform this test before one can perform other tests on cement.

This test is performed as per IS 4031 Part 4.

Standard or normal consistency of a cement paste is that consistency which will permit the Vicat Plunger, 10 mm in diameter and 40 to 50 mm in length to penetrate to a point 5 to 7 mm from the bottom or 33 to 35 mm from the top of the Vicat mould when the paste is tested within 3 to 5 minutes after it is thoroughly mixed with water.

Vicat Apparatus to be used in test shall conform to IS 5513

Procedure:

1. Take about 400 g of sieved cement through IS sieve no 9.


2. Add 100 g of water to cement in a non porous vessel and mixed thoroughly for about 3 minutes.


3. Fill the Vicat mould (placed on a non porous plate) with the cement paste, make its top surface level and struck off the surplus paste by means of a trowel.


4. Shake to mould filled with paste slightly to expel the air.


5. Place the mould on the base plate of the apparatus centrally below the movable rod to which plunger is attached and brought in contact with the surface of the cement paste.


6. Note the initial reading and release the rod quickly without any jerk and note the penetration.


7. If the penetration is between 33 to 35 mm from top of the mould then the paste is said to be of normal consistency, other wise test should be repeated with different water quantity.

Note: The time of gauging shall note be less than 3 minutes nor more than 5 minutes.

Percentage of water for normal consistency,

                                   $P=\frac{\text{Weight of water for desired penetration}}{\text{Weight of cement taken}}\times 100$

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