WAY TO FIND INITIAL SETTING TIME
initial setting time :
The initial setting time is found based on the standards published by Indian standards (IS:4031-Part 5-1988)
Every mason or every
civil engineer must know the setting time of cement to work effectively and
efficiently. Initial Setting time is the time at a point of time it starts
hardening. It means it stops flowing and starts hardening or it will turns into
plastic state After this point of time it is difficult to change the shape of
that cement past.it can be molded after the initial setting time with some
difficulty .
To talk technically
In order to place the concrete in position, it
is necessary that the initial setting time of the cement is not too low. Once
it has been laid, the hardening should be rapid so that the structure can be
subjected to the incidental loads as early as possible. The initial set is a
stage after which any visible crack will not re-unite. Therefore certain limit
for the initial setting time has to be specified
Generally the test is conducted on the cement past
only
Apparatus required for doing this test:
o Vicat apparatus conforming to "IS: 5513-1976"with needle (1.13 mm diameter).
o
Balance
of capacity 1kg and sensitivity 1 gram.
o
Gauging
trowel conforming to IS: 10086-1982.
o
Vicat
mould
o
Measuring
jar
o
Tray
o
Stop watch
Procedure to find initial setting time
Unless otherwise specified this test
shall be conducted at a temperature of 27+or -20C and 65+or -5% of relative humidity of the laboratory. Prepare a neat cement paste by gauging 400 g
cement with 0.85P water, where P is the "normal consistency" of the given sample of cement. The gauging time is between 3 and 5 minutes.
The gauging time is counted from the instant of adding of water to dry cement. Fill the vicat mould with the prepared paste
and level it to the top of the mould. The cement block thus prepared is known
as the test block. Place the test block on a non-porous plate and
set it below the vicat needle. Lower the needle to make contact with the
surface of the test block. Quickly release the needle and allow it to
sink. Note the reading. Repeat the experiment until the needle fails
piercing the block at a level 5 to 7 mm from bottom.
Values
for different types of cement and for different grades
Type/Name Of Cement
|
Referenced Indian Stanadard
|
Initial Setting Time, mints (min.)
|
OPC(33)
|
IS:269
|
30
|
OPC(43)
|
IS:8112
|
30
|
OPC(53)
|
IS:12269
|
30
|
SRC
|
IS:12330
|
30
|
PPC
|
IS:1489-1
|
30
|
RHPC
|
IS:8041
|
30
|
PSC
|
IS:455
|
30
|
High
alumina
|
IS:6452
|
30
|
Super
sulphated
|
IS:6909
|
30
|
Low
heat
|
IS:12600
|
60
|
Masonry
cement
|
IS:3466
|
90
|
IRS-T-40
|
Railway
|
60
|
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