IN THIS ARTICLE WE WILL LEARN ABOUT TEST METHOD TO FIND DETERMINATION OF INITIAL AND FINAL SETTING TIMES OF CEMENT AS PER IS 4031(PART-5)- 1988
DETERMINATION OF INITIAL AND FINAL SETTING TIME OF CEMENT
SCOPE – This standard covers the procedure for determining the initial and final setting times of cement.
SAMPLING AND SELECTION OF TEST SPECIMEN – The samples of the cement shall be taken in accordance with the requirements of IS 3535-1986 and the relevant standard specification for the type of cement being tested. The representative sample of the cement selected as above shall be thoroughly mixed before testing.
TEMPERATURE AND HUMIDITY – The temperature of moulding room, dry materials and water shall be maintained at 27±2 °C. The relevant humidity of the laboratory shall be 65±5 percent.
The moist closet or moist room shall be maintained at 27±2 °C and at a relative humidity of not less than 90%.
APPARATUS –
1. Vicat Apparatus – Vicat Apparatus conforming to IS 5513 – 1976
2. Balance – The balance shall confirming to the following requirements. On a balance in use, the permissible variation at a load of 1000g shall be plus or minus 1.0g. The permissible variation on new balance shall be one half of the value. The sensibility reciprocal shall not be greater than twice the permissible variation.
3. Standard Weights
4. Gauging Trowel – Gauging Trowel conforming to IS 10086: 1982.
PROCEDURE –
1 – Preparation of Test Block –
a. Prepare a neat cement paste by gauging the cement with 0.85 times the water required to give a paste of standard consistency. Potable or distilled water shall be used in preparing the paste.
b. The gauging time shall be counted from the time of adding water to the dry cement until commencing to fill the mould.
c. Start a stopwatch at the instant when water is added to the cement.
d. Fill the Vicat mould E with this paste, gauged as above, the mould resting on a nonporous plate.
e. Fill the mould completely and smooth off surface of the paste making it level with the top of the mould.
f. The cement block thus prepared in the mould is the test block.
g. Immediately after moulding, place the test block in the moist closet or moist room and allow it to remain there except when the determination of time of setting is being made.
2 – Determination of Initial Setting time –
a. Place the test block confined in the mould and resting on the non-porous plate, under the rod bearing the needle(C); lower the needle gently until it comes in contact with the surface of the test block and quickly release, allowing it to penetrate into the test block.
b. In the beginning, the needle will completely pierce the test block. Repeat this procedure until the needle, when brought in contact with the test block and released as described above, fails to pierce the block beyond 5.0 ± 0.5 mm measured from the bottom of the mould.
c. The period elapsing between the time when water is added to the cement and time at which the needle fails to pierce the test block to a point 5.0 ± 0.5 mm measured from the bottom of the mould shall be the initial setting time.
3. – Determination of Final Setting Time –
a. Replace the needle (C) of the Vicat apparatus by the needle with an annular attachment (F).
b. The cement shall be considered as finally set when, upon applying the needle gently to the surface of the text block, the needle makes an impression thereon, while the attachment fails to do so.
c. The period elapsing between the time when the water has added the cement and the time at which the needle makes an impression on the surface of test block while the attachment fails to do so shall be final setting time.
d. In the event of a scum forming on the surface of the text block, use the underside of the block for the determination,
REPORTING OF RESULTS – The result of initial and final setting time be reported to the nearest five minutes.
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