What is Consistency of Cement?
The standard consistency of cement paste is the percentage of water required, where the plunger penetrates into the cement paste of about 5mm to 7mm from the bottom of the mould and in the other word consistency of cement is the minimum amount of water required to initiate a chemical reaction between water and cement to form a paste. The standard consistency of a Portland cement varies between 25–35%.
Importance of Cement Consistency
As we all know that the strength of concrete depends on the quality Cement. To get the required cement strength, we have to add the right amount of water. Water below standard stability will not initiate the chemical reaction between water and cement, which will increase the strength of cement. Excess water over stability results in excess water and loss of strength. Therefore it is important to know the standard consistency of cement.
- Fineness test of Cement by dry sieving method 90 micron sieve
- Soundness test of cement by Le Chatelier
Test method of standard consistency
Test Stanadard : IS 4031-Part 4: 1997
Test Apparatus :
- Weighing Balance of accuracy 0.01gm
- Vicat apparatus with plunger
- Measuring jar
- Gauging towels
- Evaporating dish
- Maintained the testing room at a temperature and relative humidity of 27±2 °C and 65±5 %.
- Take the about 300 gms of cement sample in evaporation dish and mix water approximately 25% by weight of cement.
- Start the stopwatch at the time of adding water to the dry cement. Care shall be taking that the mixing time is not less than 3 minutes or not more than 5 minutes from the time of water adding to the dry cement.
- Place the mould of the Vicat’s apparatus on a nonporous plate and fill the mould with the paste.
- After smoothing the surface of the paste, make it level with the top of the mold. Shake the mold slightly to flush out the entrapped air.
- Place it below plunger of Vicat’s apparatus and lower the plunger gently to touch the surface of the test block.
- Quickly release the plunger, allow it to sink into the paste and record the penetration of plunger from the bottom of the mould. If this is not in between 5-7mm, take a fresh sample of dry cement of same weight and increase the percentage of water & record the penetration of the plunger.
- Keep on repeating the above paste with increase in water contents until the penetration of plunger in the cement paste is in between 5 to 7 mm.
The reading of vicat apparatus should have 5-7 mm for standard consistancy.
Test Format for Consistancy test
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