22-02-2013, 02:32 PM
DETERMINING INITIAL SETTING TIME OF CEMENT
Theory :
SETTING TIME: Setting time is arbitrary points used to
characterize cement,
Initial set: Occurs when the paste begins to stiffen considerably.
Final set: Occurs when the cement has hardened to the point at
which it can sustain some load.
Initial Setting Time is defined as the period elapsing between the
time when the water is added to cement and the time at which
the needle of 1 mm square sections fail to pierce the test block
for 5+/-0.5mm measured from the bottom of the mould. IS 269
specifies that the initial Setting Time should not be less than 30
minutes.
The Final Setting Time is defined as the period elapsing between
the time when water is added to cement and - the time at which
the needle with the annual attachment makes an impression of
the needle alone on the test block while the attachment fails to
make an impression on it. IS 269 specifies.
That the Final Setting Time should not be more than 600 mm (10
hours).
Procedure :
1) Weigh 400 gm cement.
2) Prepare paste by adding 0.85 times the percentage of water
required for standard consistency.
3) Start the stop watch at the instant when water is added to the
cement.
4) Mix thoroughly cement and water to form paste and fill the
Vicat mould on a non porous plate. Gauging time should not be
less than 3mm and more than 5 mm.
5) Tap the mould gently to expel entrapped air. Then smooth off
surface of the paste, making it level with the top of the mould.
6) Place the test block under the rod bearing the needle. Lower
the needle gently in order to make contact with the surface of the
cement paste and release quickly, allowing it to penetrate the
test block.
7) Repeat the procedure till the needle fails to pierce the test
block to a point 5.0 ± 0.5mm measured from the bottom of the
mould.
8) The time period elapsing between the time, water is added to
the cement and the time, the needle fails to pierce the test block
by 5.0 ± 0.5mm measured from the bottom of the mould, is the
initial setting time.
Result : Quality of given cement sample is _________________.
Theory :
SETTING TIME: Setting time is arbitrary points used to
characterize cement,
Initial set: Occurs when the paste begins to stiffen considerably.
Final set: Occurs when the cement has hardened to the point at
which it can sustain some load.
Initial Setting Time is defined as the period elapsing between the
time when the water is added to cement and the time at which
the needle of 1 mm square sections fail to pierce the test block
for 5+/-0.5mm measured from the bottom of the mould. IS 269
specifies that the initial Setting Time should not be less than 30
minutes.
The Final Setting Time is defined as the period elapsing between
the time when water is added to cement and - the time at which
the needle with the annual attachment makes an impression of
the needle alone on the test block while the attachment fails to
make an impression on it. IS 269 specifies.
That the Final Setting Time should not be more than 600 mm (10
hours).
Procedure :
1) Weigh 400 gm cement.
2) Prepare paste by adding 0.85 times the percentage of water
required for standard consistency.
3) Start the stop watch at the instant when water is added to the
cement.
4) Mix thoroughly cement and water to form paste and fill the
Vicat mould on a non porous plate. Gauging time should not be
less than 3mm and more than 5 mm.
5) Tap the mould gently to expel entrapped air. Then smooth off
surface of the paste, making it level with the top of the mould.
6) Place the test block under the rod bearing the needle. Lower
the needle gently in order to make contact with the surface of the
cement paste and release quickly, allowing it to penetrate the
test block.
7) Repeat the procedure till the needle fails to pierce the test
block to a point 5.0 ± 0.5mm measured from the bottom of the
mould.
8) The time period elapsing between the time, water is added to
the cement and the time, the needle fails to pierce the test block
by 5.0 ± 0.5mm measured from the bottom of the mould, is the
initial setting time.
Result : Quality of given cement sample is _________________.