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Question:

Published on: 30 June, 2022

How standard consistency test is done on cement? Explain the procedure briefly.

Answer:

Standard Consistency Test:-

Standard consistency of cement paste is defined as that consistency which permits the Vicat plunger to penetrate to a point 5 to 7 mm from the bottom of the Vicat mould in this test. It is expressed as amount of water as a percentage (by weight) of dry cement.

Necessity and uses of standard consistency

Generally the water percentage for standard consistency is about 30%. However cement produced by different factories may not have same properties and so it is necessary to standardize the consistency using standard equipment.
The knowledge of standard consistency is required while performing other important test such as setting time, soundness etc. as these tests are performed on cement paste using a certain percentage of water required for standard consistency.

Gauging time

It is period observed from the time when water is added to cement for making cement paste till commencing the filling of mounld of Vicat Apparatus, in this test.

Apparatus :-

A Vicat apparatus with plunger 10mm dia
Weighing balance
Trowel weighing 210g ± 10g
Measuring glass 200ml
Clean platform to make cement paste

Materials: -

Cement 3 to 4 kg
Water

Procedure: -

Take a sample off cement 300g. Weigh it correctly.
Add water 25% by weight i.e., 75g (75ml) to the cement and mix it thoroughly, to make a cement a cement paste.
Place the Vicat mould on a non-porous plate, fill the mould with cement paste, smooth off the surface of the paste making it level with the top of the mould. To expel air shake the mould slightly. The care that the gauging time is between 3 to 5 minutes. While filling the mould use of operator’s hand and blade of trowel only should be used.
Place the test block in the mould together with the non-porous plate, under the rod bearing the 10mm dia plunger gently to touch the surface of the test block and quickly release, allowing it to sink into the cement paste. Carry this operation immediately after filling the mould. Note the penetration of the needle from the bottom of mould indicated on the scale.
Prepare trial pastes with varying percentages of water, increasing water percentage by 1 % each time, until the amount of water necessary for making standard consistency (which permits plunger to penetrate to a point 5 to 7 mm from the bottom of the mould) is determined.

Subjects

Concrete Technology Design of Reinforced Concrete Structures

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