WAY TO FIND FINAL SETTING TIME
final setting time :
the final setting time is found based on the standards published by Indian standards (IS: 4031-Part 5-1988)
To work effectively and efficiently every mason or every civil engineer must know the setting time of cement. " Initial Setting time "(Initial Setting time is the time at a point of time it starts hardening (or) it starts moving from liquid state to plastic state). Final Setting time is the time at a point of time it should lose its plasticity at the earliest possible time. After this point of time it is difficult to change the shape of that cement past. permanently it sets it can’t be remolded after the final setting time
To
talk technically
In actual construction dealing with cement paste, mortar or
concrete, certain time is required for mixing, transporting and placing. During
this time, cement paste, mortar or concrete should be in plastic condition.
Once the concrete is placed in the final position, compacted and finished, it should
lose its plasticity at the earliest possible time so that it is vulnerable to
damages from external destructive agencies. This time is referred to as the
final setting time.
Apparatus required for doing this test:
Vicat apparatus conforming to IS: 5513-1976. With
needle (1.13 mm diameter). Balance of
capacity 1kg and sensitivity 1 gram. Gauging trowel
conforming to IS: 10086-1982. Vicat mould Measuring jar Tray Stop watch
Procedure to
find initial setting time
o
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.
o
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.
o
The
gauging time is between 3 and 5 minutes. The gauging time is counted from the
instant of adding of water to dry cement.
o
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.
o
Place
the test block under the Vicat needle with the annular attachment and lower the
needle just to make contact with the surface of the test block.
o
Quickly
release the needle allowing it to penetrate into the test block.
o
The
cement is said to be finally set when the needle makes an impression on the
test block and the attachment fails to do so.
o
The
time elapsed between this stage and the instant when the water was added to the
cement is called the final setting time.
Values for different types of
cement and for different grades
Type/Name Of Cement
|
Referenced Indian Stanadard
|
Final Setting Time, mints (max.)
|
OPC(33)
|
IS:269
|
600
|
OPC(43)
|
IS:8112
|
600
|
OPC(53)
|
IS:12269
|
600
|
SRC
|
IS:12330
|
600
|
PPC
|
IS:1489-1
|
600
|
RHPC
|
IS:8041
|
600
|
PSC
|
IS:455
|
600
|
High
alumina
|
IS:6452
|
600
|
Super
sulphated
|
IS:6909
|
600
|
Low
heat
|
IS:12600
|
600
|
Masonry
cement
|
IS:3466
|
1440
|
IRS-T-40
|
Railway
|
600
|
0 comments :