NORMAL CONSISTENCY OF CEMENT: VICAT APPARATUS

The standard (or normal) consistency of a cement paste is necessary to standardize the quantity of water to be mixed in cement for finding out the initial setting time, final setting time, soundness of cement and compressive strength of cement and can be done with the help of vicat apparatus.

The standard consistency is defined as the consistency of cement paste which will permit the vicat plunger to penetrate to a point 33 to 35 mm from top (or 5 - 7 mm from the bottom plate) of the mould. This experiment helps us to find out the quantity of water to be mixed for a given quantity of cement to give a cement paste of normal consistency.

 AIM: To determine the water quantity required to produce a cement paste of standard consistency.

APPARATUS: Vicat apparatus (meeting IS: 5513 – 1976 guidelines) having plunger (10 mm in diameter) balance, weights, gauging trowel.

 

Vicat apparatus

PROCEDURE:

1. Prepare a cement paste of weighed cement quantity (300 grams) with a weighed quantity of potable or distilled water. Start with 26% water of 300 g of cement.
2. Take care that the time of gauging is not less than 3 minutes, not more than 5 minutes and the gauging shall be completed before setting occurs.
3. The gauging time should begin from the time of adding the water to the dry cement and noted down up to commencing to fill the mould.
4. Fill the vicat mould completely with this paste and then rest the mould on a non-porous plate.
5. Trim off the surface of the paste, making it in level with the top of the mould. The mould may slightly be shaken to expel the air.
6. Place the test block with the mould on the non-porous resting plate, under the rod bearing the plunger (10 mm diameter) and gently lower the plunger to touch the surface of the test block and quickly release, allowing it to penetrate into the paste.
7. This operation should be carried out immediately after filling the mould.
8. Prepare a few trial cement paste having varying percentages of water and test the trail paste as described above until the exact amount of water necessary for making the standard consistency as defined above is obtained.
9. Express the amount of water in term of percentage by weight of the dry cement.

PRECAUTIONS:

1. Clean appliances shall be used for gauging.
2. The temperature of cement, water and that of test room, at the time when the above operations are being performed, shall be 27 ± 2 ᵒC.
3. The fresh cement is to be taken for each repetition of the experiment.

RESULT: The Normal consistency for the given cement sample is…………………