Various Laboratory Tests on Cement

Initial and Final Setting Time of Cement FINENESS OF CEMENT: We need to determine the fineness of cement by dry sieving as per IS: 4031 (Part 1) โ€“ 1996. The principle of this is that we determine the proportion of cement whose grain size is larger than specified mesh size. Apparatus: The apparatus used are ) 75ยตm IS Sieve ii) Balance capable of weighing 10g to the nearest 10mg iii) A nylon or pure bristle brush, preferably with 25 to 40mm iv) bristle, for cleaning the sieve Figure No. Sieve No. 200 Procedure to determine fineness of cement: i) Weigh approximately 10g of cement to the nearest 0. 01g and place it on the sieve.

Agitate the sieve by swirling, planetary and linear movements, until no more fine material passes through it. iii) Weigh the residue and express its mass as a percentage R1,of the quantity first placed on the sieve to the nearest 0. 1 percent. v) Gently brush all the fine material off the base of the sieve. v) Repeat the whole procedure using a fresh 10g sample to obtain R2.

The apparatus for conducting the Le-Chatelier test should conform to IS: 5514 โ€“ 1969 Balance, whose permissible variation at a load of 1000g should be +1. 0g and Water bath. Procedure to determine soundness of cement i) Place the mould on a glass sheet and fill it with the cement paste formed by gauging cement with 0. 78 times the water required to give a paste of standard consistency. ii) Cover the mould with another piece of glass sheet, place a small weight on this covering glass sheet and immediately submerge the whole assembly in water at a temperature of 27 ยฑ 2oC and keep it there for 24hrs.

To do so we need Vicat apparatus conforming to IS: 5513 โ€“ 1976, Balance, whose permissible variation at a load of 1000g should be +1. 0g, Gauging trowel conforming to IS: 10086 โ€“ 1982. Procedure to determine initial and final setting time of cement : i) Prepare a cement paste by gauging the cement with 0. 85 times the water required to give a paste of standard consistency. ii) Start a stop-watch, the moment water is added to the cement. iii) Fill the Vicat mould completely with the cement paste gauged as above, the mould resting on a non-porous plate and smooth off the surface of the paste making it level with the top of the mould.

The cement block thus prepared in the mould is the test block. Place the test block under the rod bearing the needle. Lower the needle gently in order to make contact with the surface of the cement paste and release quickly, allowing it to penetrate the test block. Repeat the procedure till the needle fails to pierce the test block to a point 5. 0 ยฑ 0. 5mm measured from the bottom of the mould. The time period elapsing between the time, water is added to the cement and the time, the needle fails to pierce the test block by 5. 0 ยฑ 0. mm measured from the bottom of the mould, is the initial setting time.

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