OBJECT: To determine for a given sample of cement the
(a) initial setting time
APPARATUS: The Vicat apparatus (IS: 5513-1969) setting
time needles
Extracts from IS: 4031-1968
(i) Preparation of Test Block: Prepare a
neat cement paste by gauging the cement with 0.85 times the water required to
give a paste of standard consistency (P). The paste shall be gauged in the
manner and under the conditions prescribed in exp. No. 1. Start a stop watch at
the instant when water is added to the cement. Fill the Vicat mould, with a
cement paste gauged as above, the mould resting on a non-porous plate. Fill the
mould completely and smooth off the surface of the paste making it level with
the top of the mould. The cement block thus prepared in the mould is the test
block.
Clean appliances shall be used for gauging the
temperature of water and that of test room, at the time of gauging, shall be
within 27+ 2° C.
During the test, the block shall be kept
at a temperature of 27+ 2° C in an atmosphere of at least 90 percent relative
humidity and away from draughts. Determination of Initial Setting Time: Place
the test block under the rod bearing the proper needle lower the needle gently
in contact with the surface of the test block and quickly release, allowing it
to penetrate into the test block. In the beginning, the needle will completely
pierce the test block. Repeat this procedure until the needle, when brought in
contact with the test block and released as described above, fails to pierce
the block for 5±0.5 mm measured from the bottom of the mould. The period
elapsing between the time when water is added to the cement and the time at
which the needle fails to pierce the test block by 5+0.5mm shall be the initial
setting time.
Determination of Final Setting Time:
Replace the needle used for initial setting time test by the needle with an
annular attachment. The cement shall be considered as finally set when, upon
applying the needle gently to the surface of the test block, the needle makes
an, impression thereon, while the attachment fails to do so.
The period elapsing between the time when
water is added to the cement and the time at which the needle makes an
impression on the surface of test block while the attachment fails to do so
shall be the final setting time.
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