For
convenience, initial setting time is regarded as the time elapsed between the
moments that the water is added to the cement, to the time that the paste
starts losing its plasticity. The final setting time is the time elapsed
between the moment the water is added to the cement, and the time when the
paste has completely lost its plasticity and has attained sufficient firmness
to resist certain definite pressure.
AIM:
To
determine the initial and final setting time of a given sample of cement.
Apparatus:
· Vicat apparatus conforming to IS : 5513-1976,
· Balance,
· Gauging Trowel,
· Stop Watch.
Figure:
Procedure:
1.
Preparation of Test Block - Prepare
a neat 300 gms cement paste by gauging the cement with 0.85 times the water
required to give a paste of standard consistency. Potable or distilled water
shall be used in preparing the paste.
2.
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 nonporous plate. Fill the mould completely and smooth
off the surface of the paste making it level with the top of the mould.
3.
Immediately after moulding, place the test
block in the moist closet or moist room and allow it to remain there except
when determinations of time of setting are being made.
4.
Determination of Initial Setting Time -
Place the test block confined in the mould and resting on the non-porous plate,
under the rod bearing the needle ( C ); lower the needle gently until it comes
in contact with the surface of the test block and quickly release, allowing it
to penetrate into the test block.
5.
Repeat this procedure until the needle, when
brought in contact with the test block and released as described above, fails
to pierce the block beyond 5.0 ± 0.5 mm measured from the bottom of the mould
shall be the initial setting time.
6.
Determination of Final Setting Time - Replace
the needle (C) of the Vicat apparatus by the needle with an annular attachment
(F).
7.
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.
8.
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.
Observation:
1.
Weight of given sample of cement is _ _ _ _ gms.
2.
The normal consistency of a given sample of cement is _ _ _ _ %
3.
Volume of water addend (0.85 times the water required to give a paste of
standard consistency) for preparation of test block _ _ _ _ ml.
Sr.
No.
|
Setting
Time
(Sec)
|
Penetration
(mm)
|
Remark
|
1
|
|||
2
|
|||
3
|
Result:
i)
The initial setting time of the cement sample is found to be ______.
ii)
The final setting time of the cement sample is found to be ______.
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