TESTS ON CEMENT

TESTS ON CEMENT

1. FINENESS

AIM: To determine the fineness of cement by dry sieving as per IS: 4031 (Part 1) - 1996.

PRINCIPLE
The fineness of cement is measured by sieving it through a standard sieve. The proportion of cement, the grain sizes of which, is larger than the specified mesh size is thus determined.

APPARATUS: IS SIEVE
i) 90μm IS Sieve
ii) Balance capable of weighing 10g to the nearest 10mg
iii) A nylon or pure bristle brush, preferably with 25 to 40mm bristle, for cleaning the sieve

PROCEDURE
i) Weigh approximately 10g of cement to the nearest 0.01g and place it on the sieve.
ii) 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.
iv) 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. Then calculate R as the mean of R1 and R2 as a percentage, expressed to the nearest 0.1 percent. When the results differ by more than 1 percent absolute, carry out a third sieving and calculate the mean of the three values.

REPORTING OF RESULTS
Report the value of R, to the nearest 0.1 percent, as the residue on the 90μm sieve.



2. CONSISTENCY

AIM: To determine the quantity of water required to produce a cement paste of standard consistency as per IS: 4031 (Part 4) - 1988.

PRINCIPLE

The standard consistency of a cement paste is defined as that consistency which will permit the Vicat plunger to penetrate to a point 5 to 7mm from the bottom of the Vicat mould.

APPARATUS : VICAT APPARATUS
i) Vicat apparatus conforming to IS: 5513 - 1976
ii) Balance, whose permissible variation at a load of 1000g should be +1.0g
iii) Gauging trowel conforming to IS: 10086 - 1982

PROCEDURE

i) Weigh approximately 400g of cement and mix it with a weighed quantity of water. The time of gauging should be between 3 to 5 minutes.
ii) Fill the Vicat mould with paste and level it with a trowel.
iii) Lower the plunger gently till it touches the cement surface.
iv) Release the plunger allowing it to sink into the paste.
v) Note the reading on the gauge.
vi) Repeat the above procedure taking fresh samples of cement and different quantities of water until the reading on the gauge is 5 to 7mm.

REPORTING OF RESULTS
Express the amount of water as a percentage of the weight of dry cement to the first place of decimal.



3. INITIAL AND FINAL SETTING TIME

AIM: To determine the initial and the final setting time of cement as per IS: 4031 (Part 5) - 1988.

APPARATUS
i) Vicat apparatus conforming to IS: 5513 - 1976
ii) Balance, whose permissible variation at a load of 1000g should be +1.0g
iii) Gauging trowel conforming to IS: 10086 - 1982


PROCEDURE

i) Prepare a cement paste by gauging the cement with 0.85 times the water required to give a paste of standard consistency (see Para 1.2).
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.

A) INITIAL SETTING TIME
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 ± 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 ± 0.5mm measured from the bottom of the mould, is the initial setting time.

B) FINAL SETTING TIME
Replace the above needle by the one with an annular attachment. The cement should be considered as finally set when, upon applying the needle gently to the surface of the test block, the needle makes an impression therein, while the attachment fails to do so. The period elapsing between the time, water is added to the cement and the time, the needle makes an impression on the surface of the test block, while the attachment fails to do so, is the final setting time.

REPORTING OF RESULTS
The results of the initial and the final setting time should be reported to the nearest five minutes.


4. SOUNDNESS

AIM: To determine the soundness of cement by Le-Chatelier method as per IS: 4031 (Part 3) - 1988.

APPARATUS
LE-CHATELIER'S TEST APPARATUS

i) The apparatus for conducting the Le-Chatelier test should conform to IS: 5514 - 1969
ii) Balance, whose pemissible variation at a load of 1000g should be +1.0g
iii) Water bath

PROCEDURE
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 ± 2oC and keep it there for 24hrs.
iii) Measure the distance separating the indicator points to the nearest 0.5mm (say d l ).
iv) Submerge the mould again in water at the temperature prescribed above. Bring the water to boiling point in 25 to 30 minutes and keep it boiling for 3hrs.
v) Remove the mould from the water, allow it to cool and measure the distance between the indicator points (say d 2 ).
vi) (d 2 – d l) represents the expansion of cement.

REPORTING OF RESULTS

Calculate the mean of the two values to the nearest 0.5 mm to represent the expansion of cement.

Author : Unknown

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