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Test to Calculate the Consistency of Cement
Test to Calculate the Consistency of Cement: The Cement Consistency Test is used to determine the normal consistency of every cement paste. Additionally, the consistency value is used to determine the initial setting time, final setting time, and soundness of cement, as well as the strength parameter of cement.
What is the Standard Cement Consistency?
A cement paste’s standard consistency is described as that which allows the vicat plunger to penetrate to a point 5 to 7mm from the bottom of the vicat mold.
The aim of the Cement Consistency Test is to determine the standard consistency of cement paste in the laboratory using the vicat apparatus.
Finding the Standard Consistency of Cement
Apparatus
1. Vicat Apparatus
The vicat apparatus consists of a frame with a movable rod with a cap at one end and one of the following interchangeable attachments at the other end:
- Needle for calculating the time required for initial setting
- A needle is used to determine the final setting time.
- Plunger for deciding the consistency of the cement
2. Moving Rod
Movable rod carries an indicator which moves over a graduated scale connected to to the frame.
3. Mould
Single mould
The vicat mold is made of foam and has an internal diameter of 60 +/-0.5mm at the tip, 70 +/-0.5mm at the bottom, and a height of 40 +/ 0.5mm.
Test Procedure for Cement Consistency
- Unless otherwise stated, this test shall be performed at a temperature of 27 + 20 degrees Celsius and a relative humidity of 65 + 5% in the laboratory.
- Prepare a paste by combining a weighted quantity of cement (300gms) and a weighed quantity of potable or purified water, taking note that the gauging period is neither less than 3 minutes but more than 5 minutes, and that the gauging is done prior to any indication of setting.
- Gauging is performed from the moment water is added to the dry cement until the mold is filled.
- Fill the vicat mold halfway with this paste, which should be lying on a non-porous tray.
- Smooth the paste’s surface until it is level with the tip of the mold.
- Shake the mold slightly to remove any trapped air.
- Operators shall only use their hands and the blade of the gauging trowel when filling the mould.
- Place the test block with the non-porous resting plate immediately underneath the plunger rod.
- Gently lower the plunger until it reaches the test block’s surface and immediately detach, allowing it to settle into the paste.
- Keep track of the penetration depth.
- Prepare trial pastes with various water percentages and measure as mentioned above until the plunger is 5mm to 7mm from the bottom of the vicat mold.
Calculations
Take note of the following:
- mass of taken cement
- Initial % of water added to cement
- Amount  of water added to cement
Precautions
Care must be taken to preserve the specified temperature, humidity, and mixing time to prevent the cement paste from settling.
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