Overview
Standard consistency of a cement paste is
defined as that consistency which will permit a vicat plunger having 10 mm dia
and 50 mm length to penetrate to a depth of 33-35 mm from top of the mould.
Apparatus
Measuring
Instruments
|
NAME
|
CAPACITY
/ RANGE / SIZE
|
ACCURACY / LEAST COUNT
|
|
Vicat
apparatus
|
Should
be made as per IS:5513
|
—
|
|
Balance
|
1000
g
|
1
g
|
|
Measuring
cylinder
|
100
ml
|
1
ml
|
Other
accessories
|
Tray,
glass plate
|
Vicat Apparatus
Environmental Condition
|
Temperature
|
27
± 20 C
|
|
Humidity
|
65
± 5 %
|
Procedure
1. Take 400 g
of cement and place it in the enameled tray.
2. Mix about
25% water by weight of dry cement thoroughly to get a cement paste. Total time
taken to obtain thoroughly mixed water cement paste i.e. “Gauging time” should
not be more than 3 to 5 minutes.
3. Fill the
vicat mould, resting upon a glass plate, with this cement paste.
4. After
filling the mould completely, smoothen the surface of the paste, making it
level with top of the mould.
5. Place the
whole assembly(i.e. mould + cement paste + glass plate) under the rod bearing
plunger.
6. Lower the
plunger gently so as to touch the surface of the test block and quickly release
the plunger allowing it to sink into the paste.
7. Measure
the depth of penetration and record it.
8. Prepare
trial pastes with varying percentages of water content and follow the steps (2
to 7) as described above, until the depth of penetration becomes 33 to 35
mm.
Calculation
Calculate percentage of water (P) by weight
of dry cement required to prepare cement paste of standard consistency by
following formula, and express it to the first place of decimal.
Where,
P=W/C*100
W=Quantity of water added
C=Quantity of cement used
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