VICAT APPARATUS WITH DASHPOT
Working Manual
OPERATING INSTRUCTIONS
FOR
VICAT APPARATUS WITH DASHPOT
The equipment comprises of the
following :
1.
One metallic frame bearing a movable rod with a cap at
top
2.
One Vicat Mould
3.
One Glass Base Plate
4.
One Initial Needle, in plastic container
5.
One Final
Needle, in plastic container
6.
One Consistency Plunger, in plastic container
7.
One Operating
Instructions with General Assembly Drawing.
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I
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NTRODUCTION : The equipment is meets the requirement of IS:
5513. There are used for the determination of Standard Consistency Initial
Setting Time and Final Setting Time of
cement paste of Ordinary Portlanmd Cement, Rapid Hardening Portland
Cement, Low Heat Portland Cement, and other Hydraulic Cements as per procedure
described in IS - 1727, 2541 (P.I), 2645, 4031, BS : 12, 146, 915, 1370, 4027,
4246, 4248, ASTM C-91, C-141, C-187, C-191, C-308, C-472 and ASSHO T-129 E-131.
'HT' Model has an additional
attachment of dash pot which facilitates lowering of movable rod slowly.
DESCRIPTION : The equipment are illustrated in the General
Assembly Drawing attached. The instrument consists of a metallic frame
bearing a movable rod with a cap at one end.
At the other end, any one of the following attachment which are
interchangeable may be attached.
1.
Initial Needle
2.
Final Needle
3.
Plunger
The movable bearing rod carries
an indicator which moves over a graduated scale attached to the frame. A release pin is provided for holding the
movable rod while fixing the needle or
plunger. In 'HT' make model, a dash pot is fitted to the frame. The dash pot is filled with oil of low
viscosity (oil is not supplied) helps in
lowering the movable rod slowly. It is
recommended to use 3-in-1 or singer oil or any equivalent oil of low viscosity.
VICAT MOULD : The mould is
in the form of frustum of a cone having internal diameter at upper and lower
end 70 + 0.5 and 60 + 0.5 mm respectively and a height of 40 +
0.5 mm.
INITIAL NEEDLE : The
needle is circular in cross-section having a cross sectional area of 1mm2.
The end of the needle is flat . This is
used for the determination of the initial setting of the cement.
FINAL NEEDLE: The needle is circular in cross-section
having a cross sectional area of 1mm2. The needle is fitted in a metal attachment
(hollowed out). The end of the needle
projects beyond the cutting edge of the hollowed out metal attachment. This is used for determining the final
setting time of cement.
PLUNGER : The Plunger is
known as the consistency plunger. It is
made of polished brass with a projection at the upper end for insertion into
the movable rod. The lower end is flat.
SETTING UP : Keep the
Vicat Apparatus on a level base. When
using 'HT' model keep the movable rod at its highest position and hold it with
the pin. Unscrew the top of the
dashpot. Half fill the dashpot with
suitable oil of low viscosity and screw on the top. Work the plunger a couple of times.
TEMPERATURE FOR TESTING
: The temperature range within which
physical tests may be carried out should , as far as possible be 27OC
+ 2OC.
DETERMINATION OF CONSISTENCY
OF STANDARD CEMENT PASTE :
1.
DEFINATION : The standard consistency of cement
past is that which will permit the Vicat Plunger to penetrate to a point 5 to
7mm from the bottom of the Vicat Mould, when cement is tested as described
below.
2.
SPECIMEN PREPARATION : Take 400g of weighed
cement in a dish. Run down a known
quantity of water from the burette into the dish and mix it thoroughly taking
care that the time of gauging is neither less than 3 minutes nor more than 5
minutes and that gauging is completed before any sign of setting occurs. Gauging time is the time elapsing from the
time of adding water to the dry material until commencing to fill the
mould. Clean appliances shall be used
for gauging. The gauging trowel (Gauging
Trowel supplied as accessory at extra cost) and operator's hand shall alone be
used.
3.
TEST PROCEDURE : Apply petroleum jelly to the
inner surface of the Vicat Mould and the base plate, so that there may not be
any leakage of water. Fit the plunger to
the movable rod. Prepare the cement
paste as described above and fill mould.
For filling the mould, operator's hand and the blade of gauging trowel
shall alone be used. Level-off the
surface of the mould, place the whole assembly on the base of the Vicat
Apparatus and slowly bring down the plunger attached to the bearing rod to the surface of the
cement paste and quickly release. (when
'HT' model Vicat Needle Apparatus with dashpot is used, place the mould filled
with cement paste and the non-absorbent plate on the base plate of the Vicat
Apparatus. Raise the plunger of the
dashpot, bring it in contact with the top cap of the movable bearing rod,
remove the pin holding the movable bearing rod to the surface of the cement
paste and quickly release by pushing down the plunger of the dashpot with
hand). All these operations are to be
carried out within the minimum possible time after filling the mould, so that
there may not be any setting. If the
signs of setting are observed, reject the paste and start with fresh specimen.
Prepare the trial
paste with varying percentages of water until plunger penetrates to a point 5
to 7mm from the bottom of the Vicat Mould, which is read on the scale. Express the water required as percentage by
weight of the dry cement. The apparatus
shall be free from vibrations during the test.
DETERMINATION
OF INITIAL SETTING TIME :
1.
SPECIMEN PREPARATION : Prepare neat cement paste
by gauging the cement with 0.85 times the water required to give a paste of
standard consistency in the manner and under the conditions already described
above preferably in an atmosphere of 90% relative humidity. Start a stop watch at the time water is added
to the cement. Remove the grease on the
initial needle.
2.
TEST PROCEDURE : Attach a needle for the
determination of initial setting time to the movable bearing rod of the Vicat
Apparatus. Place the glass plate on the
base of the Vicat Apparatus. Lower the
movable rod and rest the needle on the plate.
Raise the rod and pin it. Note
the reading on the scale. Fill the
mould, positioned on the glass plate, with cement paste.
In filling the
mould, operator's hands and the gauging trowel shall alone be used. Place the
mould with the test block on glass plate on the base of the Vicat apparatus
under bearing rod to which the initial needle is attached. Slowly bring down the needle to the surface
of the cement paste and quickly release (When
'HT' model Vicat Apparatus with dash pot is used, place the mould filled
with cement paste and the glass plate on the base of the Vicat Needle
Apparatus).
Raise the
plunger of the dashpot, bring it in contact with the top cap of the movable
rod, remove the pin holding the movable bearing rod and bring down the initial
needle attached to the movable bearing rod to the surface of the cement paste
and quickly release by pushing down the plunger of the dashpot with hand.
Note down the
reading on the scale. Similarly, take
penetration reading at a regular interval, say at every 10 minutes. Be vigilant as the setting time approaches
and observe the penetration at smaller
intervals. Every time, clean the
needle from the sticking cement paste soon after it is withdrawn. Note the time when the needle rests, about a
point 5 + 0.5mm from the original reading which corresponds to the
bottom of the Vicat Mould. This gives
the initial setting time.
DETERMINATION OF FINAL SETTING
TIME:
TEST PROCEDURE : Remove
the initial needle and fit in the final needle with hollowed out metallic
attachment to the bearing rod. Lower down the needle slowly to contact with the
surface of the paste and apply the needle gently to the surface (wile 'HT'
Vicat Needle Apparatus with dashpot employ the plunger of the dashpot and set
up needle as described under determination of initial setting time test
procedure). Repeat the same operation at
regular intervals of time until the projection makes a mark on the surface of the test block while
metallic attachment fails to do so .
Note down the time.
The period elapsing between the time when water is added the dry
material and the time at which the needle makes an impression on the surface
while the attachment fails to do so, when upon applying the needle gently to
the surface, gives the final setting time.
In the event of a scum forming on
the surface of the test block, the under side of the test block may be used for
determining the final test.
Take at least three specimens and
take the mean as the final setting time.
SPECIFICATIONS FOR SETTING
TIMES OF VARIOUS TYPES OF CEMENTS
Sr.No.
|
TYPE OF CEMENT
|
INITIAL SETTING TIME NOT LESS
THAN
|
FINAL SETTING TIME NOT MORE
THAN
|
1.
|
Ordinary
|
30 minutes
|
600 minutes
|
2.
|
Rapid Hardening
|
30 minutes
|
600 minutes
|
3.
|
Low Heat Period
|
60 minutes
|
600 minutes
|
PRECAUTIONS :
1.
The apparatus should remain free from vibrations during
the test.
2.
Care should be taken that the initial needle is not
bent and is fixed vertically straight into the movable rod.
3.
The needles and the plunger should be kept free from
the adhering cement, as the cement adhering on the sizes may retard penetration
and cement at the bottom may increase.
4.
All the tests should be carried out at 27OC
+ 2OC and 90% relative humidity.
5.
Petroleum Jelly should be applied to the mould.
MAINTENANCE: BEARING ROD
SHOULD BE OILED PERIODICALLY AND THE NEEDLES SHOULD BE KEPT IN THEIR
RESPECTIVE CASES AFTER THESE ARE CLEANED
& GREASED.
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