What Is Standard Consistency of Cement?
The standard consistency of cement paste is defined as the percentage of water added In 300gm weight of cement which will permit a Vicat plunger having 50 mm length and 10 mm diameter to penetrate in cement paste to a depth of 33-35 mm from the top of the mold.
The objective of Consistency Test of Cement: To find out the standard consistency of cement paste in the laboratory using Vicat apparatus.
Test On Cement
The following tests are conducted on cement in the laboratory are as follows:
- Fineness Test of Cement
- Consistency Test of Cement
- Setting Time Test of Cement
- Soundness Test of Cement
- Heat of Hydration Test
- Speicific Gravity Test of Cement
- Tensile Strength Test
- Chemical Composition Test
- Vicat apparatus,
- Gauging Trowel,
- Stop Watch, etc.
Consistency Test of Cement Procedure
1. The standard consistency of any cement is achieved when cement permits the Vicat plunger to penetrate to a point 33 to 35 mm from the bottom of the Vicat mould.
2. First of all, take about 300 gm of cement into a tray and is mixed with a known percentage of water by weight of cement. Let’s start with 26% of water and then it is increased by 2% until the normal consistency is achieved.
3. Prepare cement paste by adding 26% of water to 300gm of cement and mix it well with taking care that the time of mixing is not less than 3 minutes, nor more than 5 min and the mixing shall be completed before any sign of setting occurs. The mixing time shall be counted from the time of adding water to the dry cement until commencing to fill the mould.
4. Fill the Vicat mould having 80mm diameter and 50mm height with this paste, mould shall be resting upon a non-porous plate (glass plate). After completely filling the mould with cement paste level the top surface and remove any extra cement from the top and make it smooth. Sometimes, shaking should be done to remove any extra air.
5. Place the cement paste-filled mould together with the non-porous resting plate, under the consistency test plunger in the Vicat apparatus.
6. Now, Lower the plunger such that it touches the top surface of mould filled with paste, and quickly release, allowing it to sink into the paste. This process shall be done quickly after filling the mould.
7. Observe the penetration value on the Vicat apparatus scale. It should be around 33 to 35 mm from the mould filled with cement paste. If is not, then increase the % of water and repeat the above steps.
8. Repeat the whole process with varying % of water to cement, until penetration value comes to 33 mm to 35 mm from the top of mould toward the bottom of the mould.
Cement Consistency Calculation
- Weight of cement = 300 gm,
- % of water = 26% to 38 % (normal consistency of OPC range between this)
- Take 26% of water for the test, then the amount of water to be added in 300 gm of cement will be
= 300 x 26%
= 300 x (26/100)
= 78 ml
- Then add 78 ml of water of 300 gm of cement, prepare well mix and test.
- If the test not successful, increase % of water as 28 %.
- Take 28% of water for test, then the amount of water to be added in 300 gm of cement will be
= 300 x 28%
= 300 x (28/100)
= 84 ml
- Then add 78 ml of water of 300 gm of cement prepare well mix and test.
Observation Table for Consistency Test of Cement
Conclusion / Result : The Standard consistency of cement =
Points to be Noted
- The time of mixing cement paste should not be less than 3 minutes and not more than 5 minutes. Mixing time is the time elapsing from 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 +/- 2oC
- Assure that there should be no vibration on the working table.
- The plunger should be cleaned during every repetition.
Standard Consistency of Cement
The standard consistency of a cement paste is defined as the percentage of water added In 300gm weight of cement which will permit a Vicat plunger having 50 mm length and 10 mm diameter to penetrate in cement paste to a depth of 33-35 mm from the top of the mould.
Why do we do cement consistency test?
Finding out standard consistency of cement is essential because the amount of water added in cement affect the setting time of cement, Less water added than this standard consistency would not complete chemical reaction thus resulting in the reduction concrete of strength and 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% to 35%. There is no trial and error method by using the Vicat apparatus to find out the correct consistency of cement.
Consistency of Cement
The standard consistency of cement varies between 25-35%. To prepare a mix of cement paste 25-35% water by weight of cement added to achieve good consistency of cement.
Watch Video: Consistency Test of Cement | Procedure & Result Calculations
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