SETTING TIME OF CEMENT

 SETTING TIME OF CEMENT

AIM:

            To determine the initial and final setting time of cement.

vicat apparatus

APPARATUS REQUIRED:

  • Vicat apparatus confirming to IS: 5513-1976
  • Stop Watch
  • Measuring jar
  • Metal Tray
  • Weigh balance

SAMPLE

The cement taken should be finely ground material which of addition of requisite quantity of water is capable of hardening both under water and in air by the chemical interaction of its constituents with water and capable of binding together the appropriate materials. (Reference IS: 3535 - 1986)

PROCEDURE:

  1. Prepare a neat cement paste by gauging the cement (500g) with 0.85 times the water required to give a paste of standard consistency.
  2. The paste shall be gauged in the manner under the condition prescribed in IS: 4031(Part)-1988
  3. Start the stop watch at the instant when the water is added to the cement. Record this time (t1).
  4. Fill the Vicat mould with the cement paste gauged as above, the mould should be resting on a non-porous material.
  5. 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 is called test block.

INITIAL SETTING TIME:

  •  Place the test block confined in the mould and resting on the non-porous plate, under the rod bearing the needle.
  •  Lower the needle, gently and bring it into the contact with the surface of the test block and quickly release, allowing it to penetrate in to the test block.
  •  In the beginning, the needle will completely pierce the test block. But after some time when the paste starts losing it plasticity, the needle will penetrate only up to a depth of 5 ±0.5mm from the bottom of the mould. Note this time (t2).
  • 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 at a point 5.0±0.5mm measured from the bottom of the mould is taken as initial setting time.

FINAL SETTING TIME:

  •      Replace the needle used for initial setting time of the Vicat apparatus by a needle with a circular attachment with a diameter of 5mm2.
  •     The cement shall be considered as finally set when upon lowering the attachment gently to the surface of the test block, the needle makes an impression, while the circular cutting edge of the attachment fails to do so or when the centre nails fails to make an impression of depth more than 0.5mm. Note this time (t3).
  •      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 the test block while the attachment fails to do so shall be the final setting time.
  •      The initial and final setting time shall be reported to the nearest 5minutes.

OBSERVATION:    

SI.No

Time in Minutes

Penetration in mm

1

5

 

2

10

 

3

15

 

4

20

 

5

25

 

6

30

 

 CALCULATION:

            Initial Setting Time = t2-t1

            Final Setting Time = t3-t1

Where,

t1=Time at which water is first added to cement

t2=Time when needle fails to penetrate 5 mm to 7 mm from bottom of the mould

t3=Time when the needle makes an impression but the attachment fails to do so

NOTE:

Acceptable Value for the followings

1.    Initial Setting Time – 30mins

2.    Final Setting Time – 10hours

 

REFERENCE:

            IS: 4031 (PART 5) – 1988


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