Consistency Of Cement | Standard Consistency Test Of Cement | Vicat Apparatus
Hello friends, today in this post you will learn the Standard Consistency Test of Cement with calculations & detail stepwise procedure.
So, don't skip to read the post completely. After reading the post, you will completely understand the simple tests of the Compression test on concrete cubes.
So, let's start with these amazing topic...
What is Standard Consistency of Cement?
It is the % of water added in the cement, which will allow the Vicat plunger having dimensions such as 50 mm length & 10 mm diameter to penetrate in cement paste upto a depth of 33-35 mm from the top of the mould.
The main objective of Consistency Test of Cement :
To find out the standard consistency of cement paste in the laboratory using Vicat apparatus.
I.S code for the Consistency Test of Cement : IS : 5513-1976, IS : 4031 ( Pat 4 ) – 1988.
Apparatus
- Vicat apparatus,
- Balance,
- Gauging Trowel,
- Stop Watch, etc.
Procedure for the Consistency Test of Cement :
1.Standard consistency of the cement is achieved, when cement paste allows the Vicat plunger to penetrate about 33-35 mm from the bottom of the Vicat mould.
2.Take about 300g of cement into a enamel tray, after that mixed with a known percentage of water by weight of cement.
Assuming, 26% of water at starting, after that we have to increase it by 2% until the normal consistency is achieved.
3.Now we have to Prepare cement paste by adding 26% of water to 300 gm of cement & mix it well with care.
4.Mixng time should be between 3-5 min and we also take care that mixing shall be completed before any sign of setting occurs.
5.The mixing time shall be counted from the time of adding water to the dry cement until commencing to fill the mould.
6.Now we have to Fill the Vicat mould which having 80mm dia. & 50mm height with this paste, mould be kept on a non-porous plate (glass plate), before filling with paste.
7.After completely filling the paste, we have to level the top surface. Sometimes, shaking should be done to remove entrapped air.
8.Place the mould together with the non-porous plate, below the plunger in the Vicat apparatus.
9.After that we have to Lower the plunger such that it just touches the top surface of mould filled with paste & quickly release, allowing it to sink into the paste. This process shall be done quickly after filling the mould.
Calculation of Cement Consistency :
- Weight of cement = 300 gm,
- % of water = 26% to 38 % (normal consistency of OPC)
- Take 26% of water for the test, then the amount of water to be added in 300 gm of cement will be
10.Now we have to observe the penetration value on the Vicat apparatus scale. It should be around 33-35 mm from the mould filled with cement paste.
11.It should not to be increase the % of water & repeat the above steps.
12.Repeat the whole process with varying % of water to cement, until penetration value comes to 33-35 mm from the top of mould toward the bottom of the mould.
= 300 x 26%
= 300 x (26/100)
= 78 ml.
- Then add 78 ml of water to 300 gm of cement, prepare well mix and test.
- If the test is not successful, increase % of water by 28 %.
- Take about 28% of water for a test, then the amount of water to be added in 300 gm of cement will be
- Then, again add 78 ml of water of 300 gm of cement prepare a good mix and test.
= 300 x 28%
= 300 x (28/100)
= 84 ml
Points to be Noted
- The mixing time for the cement paste should be 3-5 minutes. Mixing time means the time from which the time of adding water to the dry cement until commencing to fill the mould.
- The cement consistency test should be conducted at room temperature 27oC +/- 2o C
- While testing, we should assure that there should be no vibration on the working table.
- The plunger should be cleaned during every repetition.
FAQs:
Standard Consistency of Cement
It means the percentage of water added In 300gm weights of cement which will allow a Vicat plunger having 50 mm length & 10 mm diameter to penetrate in cement paste to a depth of 33-35 mm from the top of the mold.
Why it is necessary to perform the cement consistency test?
It is necessary to perform, the standard consistency of cement, because the amount of water added to cement affects the setting time of cement.
If less percentage of water added than this standard consistency would not complete the chemical reaction.
As a result, there will be reduction in the strength of concrete & more water would increase water-cement ratio and so would reduce its strength.
What is the normal consistency of cement paste?
The normal consistency of cement paste generally varies from 25-35%. There is no trial and error method by using the Vicat apparatus to find out the correct consistency of cement.
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