To determine the percentage of water required to prepare a cement paste of a standard (Normal) consistency for a given sample of cement.

 

OBJECT: To determine the percentage of water required to prepare a cement paste of a standard (Normal) consistency for a given sample of cement.

 

APPARATUS: - Vicat apparatus (I.S.: 5513 – 1969), plunger 10 mm. diameter.

 

EXTRACTS FROM I.S. 4031 - 1968: -

The standard consistency of a cement paste is defined as that consistency which will permit the Vicat plunger to penetrate to a point 5 to 7 mm from the bottom of the Vicat mould; when the cement paste is tested as described under:

 

1. Prepare a paste of weighed quantity of cement (400 gms.) with a weighed quantity of water (start with 28% of water), taking care that the time of gauging is not less than 3 minutes, nor more then 5 min, and the gauging time shall be completed before any signs of setting occur. The gauging time shall be counted from the time of adding water to the dry cement until commencing to fill the mould. Fill the Vicat mould with this paste, the mould resting upon a non-porous plate. After completely filling the mould, smooth off the surface of the paste, making it level with the top of the mould. The mould may be slightly shaken to expel the air.

 

    Clean appliances shall be used for gauging. Temperature of cement, water and that of test room, at the time when the above operations are being performed, shall be form 27° ± 2° C. in filling the mould, the operator's hands and the blade of the gauging trowel shall alone be used. The trowel shall weight 210 ± 10 g.

 

2. Place the test block in the mould, together with the non-porous resting plate, under the rod bearing the plunger: lower the plunger gently to touch the surface of the test block and quickly release, allowing it to sink into paste. This operation shall be carried out immediately after filling the mould.

 

3. Prepare trial pastes with varying percentage of water and test as described above until the amount is found. Express the amount of water as a percentage by weight of the dry cement.

 

 

 

 

 

 

 

OBSERVATION: 1. Weight of cement

 

S. No.	Weight of water added.	Percentage of water added.	Penetration of plunger from the bottom of the mould. (mm.)

 

RESULT: - Water required to make a cement paste of standard consistency %.

 

DISCUSSION: - Cover following points:

1. Importance of gauging time.

2. Importance of the test.

3. Normal result expected.

4. Reasons for deviation of actual results from expected results.

 

NOTE: -

1. Leave the appliances used by you and their surroundings clean.

2. Record your observation in the journal and get them verified by your teacher.