Amit Payal

1. The Consistency of cement test is performed to determine the amount of water content
that is to be added in cement to attain Standard consistency or normal consistency of
cement.
OR
Amount of water added in cement to penetrate the VICAT plunger up to a depth of 5-7mm
from the bottom of the VICAT mould or 33-35mm from top of the VICAT mould.
OR
The standard consistency of cement is that consistency, which permit the VICAT plunger
to penetrate to a point 5 to 7mm from the bottom of the VICAT mould when tested.
Significance of NC:
When water is mixed with cement hydration reaction starts. Excessive addition of water
in cement results in an increase in Water cement ratio & ultimately cement loses its
strength when it hardens. If less water is added than required, cement isn’t properly
hydrated and results in loss of strength.
Why Normal Consistency of cement varies? The main reasons are: -
❖ Weather conditions (Temperature & Humidity)
❖ Water–Cement (w/c) ratio
❖ The excessive composition of silica (Fly Ash)
❖ The fineness of cement.
❖ The Grinding system adopted by cement companies
❖ Cement produced by different companies doesn’t have the same consistency.

2. For finding the Normal Consistency of cement as per IS:4031-PART4-1988 - VICAT
APPARATUS test is performed. Procedure of NC test of cement: -
❖ Take 400 gm of cement for making a paste.
❖ In Portland Cement the Normal Consistency varies from 25% to 35%, so we start this experiment
by using 25% of the cement weight.
❖ The quantity of water can be calculated as (25 *400)/100 = 100 ml
❖ Prepare a paste of weighed quantity of Cement with a weighed quantity of potable or distilled water.
❖ Take care of the time of gauging, it should be between 3-5 minutes and the gauging must be
completed before any sign of setting occurs.
❖ The gauging time is counted from the time of adding water to the dry cement until commencing to
fill the mould.
❖ Fill the VICAT Apparatus mould with this paste, the mould resting upon a non-porous plate.
❖ After completely filling the mould, smoothen the surface of the paste, making it level with the top of
the mould. The mould may be slightly shaken for removing the air.
❖ Place 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 mould, and quick release, allowing it to sink
into the paste.
❖ This operation is carried out immediately after filling the mould.
❖ Then note down the reading of penetration from the graduated scale.
❖ Prepare a trial paste with varying percentages of water and test as described above until the
penetration reading is 33-35 mm from top of the scale.
Reporting of Results
Express the amount of water as a percentage of the weight of dry cement to the first place of decimal.
Number of repetitions of test: - Number of repetitions required will depend on
❖ Accuracy while performing the test
❖ Skill of performer
❖ An accuracy of apparatus
❖ Maintaining temperature and humidity

3. Frequency of Normal Consistency test of Cement
❖ At use of every 50 MT cement.
❖ When the source of cement is changed.
❖ When the type of cement is changed.
❖ When the brand of cement is changed.
❖ When the grade of cement is changed.
What should you do when result is not in range of Acceptance Criteria?
Normal consistency for Portland cement varies between 25-35%. More than this value show that the cement
paste might have become extra wet and poor which lead to bleeding and less than this value shows that
cement paste might have become harsh which can cause cracks and give a rough surface. If the test result
is not in range of acceptance criteria, then you should find the reason. There are many reasons behind it,
as given below: -
❖ Cement may be very fine
❖ Chemical properties might have changed due to some reason,
❖ There may be defect during a manufacturing process
❖ Cement might have absorbed moisture from the atmosphere
Points to be Take Care
❖ Clean appliances shall only be used for the experiments.
❖ Temperature and Humidity: experiment to be conducted at the room temperature and the relative
humidity of the laboratory shall be around 65 ± 5 per cent.
❖ There should be no vibration during the experiment on the working table.
❖ The plunger and mould should be cleaned and oil should be applied on the surface during every
repetition.