SETTING TIME TEST FOR CEMENT

SETTING TIME

OBJECTIVE

To determine the initial & final setting time of cement.

APPARATUS

MEASURING INSTRUMENTS

NAME	CAPACITY / RANGE / SIZE	ACCURACY / LEAST COUNT
Vicat apparatus	Should be made as per IS:5513	—
Balance	1000 g	1 g
Measuring cylinder	100 ml	1 ml
Stop watch	30 min.	0.2 sec

OTHER APPARATUS

Glass plate, enamel tray, trowel

             

                                                  Fig:-Showing Vicat Apparatus

ENVIRONMENTAL CONDITION

Temperature	27 ± 20 C
Relative Humidity	90 % (min)

PROCEDURE

(A) TEST BLOCK PREPARATION

1.      Before commencing setting time test, do the consistency test to obtain the water required to give the paste normal consistency (P).

2.      Take 400 g of cement and prepare a neat cement paste with 0.85P of water by weight of cement.

3.      Gauge time is kept between 3 to 5 minutes. Start the stop watch at the instant when the water is added to the cement. Record this time (t₁).

4.      Fill the Vicat mould , resting on a glass plate, with the cement paste gauged as above. 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.

(B) INITIAL SETTING TIME

1.      Place the test block confined in the mould and resting on the non-porous plate, under the rod bearing the needle.

2.      Lower the needle gently until it comes in contact with the surface of test block and quick release, allowing it to penetrate into the test block.

3.      In the beginning the needle completely pierces the test block. Repeat this procedure i.e. quickly releasing the needle after every 2 minutes till the needle fails to pierce the block for about 5 mm measured from the bottom of the mould. Note this time (t₂).

(C) FINAL SETTING TIME

1.      For determining the final setting time, replace the needle of the Vicat’s apparatus by the needle with an annular attachment.

2.      The cement is considered finally set when upon applying the final setting needle gently to the surface of the test block; the needle makes an impression thereon, while the attachment fails to do so. Record this time (t₃).

CALCULATION

Initial setting time=    minutes

Final setting time=      minutes

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.

PRECAUTIONS

§  Release the initial and final setting time needles gently.

§  The experiment should be performed away from vibration and other disturbances.

§  Needle should be cleaned every time it is used.

§  Position of the mould should be shifted slightly after each penetration to avoid penetration at the same place.

§  Test should be performed at the specified environmental conditions.