DETERMINATION OF SOUNDNESS OF CEMENT BY THE LE CHATELIER METHOD.


DETERMINATION OF SOUNDNESS OF CEMENT
BY THE LE CHATELIER METHOD.
(IS: 4031 – part – 3)
Object:
Determination of the Soundness of cement by the Le Ch atelier method.
Apparatus:
The apparatus for conducting the test consists of small split cylinder of spring brass or other suitable metal of 0.5 mm thickness, forming a mould 30 mm internal diameter and 30 mm high. On either side of the split mould are attached two indicators with pointed ends, the distance from these ends to the center of the cylinder being 165 mm. The mould shall be kept in good condition with the Jaws not more than 0.50 mm apart.
Procedure:
Place the mould on a glass sheet and fill it with cement paste formed by gauging cement with 0.78 times the water required to give a paste of standard consistency. The paste shall be gauged in the manner and under the conditions prescribed in determination of consistency of standard cement paste, taking care to keep the edges of the mould gently together while this operation is being performed. 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 270C +/- 20C and keep there for 24 hours. Measure the distance separating the indicator points. Submerge the moulds again in water at the temperature prescribed above. Bring the water to boiling, with the mould kept submerge, in 25 to 30 minutes, and keep it boiling for three hours. Remove the mould from the water, allow it to cool and measure the distance between the indicator points. The difference between these two measurements represents the expansion of the cement.

Limits:
Expansion should not be more than 10 mm.



DETERMINATION OF FINENESS OF CEMENT.
(IS: 4031 – part – 3)
Object:
To determine the fineness of cement by dry sieving.
Apparatus:
a) Standard balance with 100 gm. weighing capacity.
b) IS : 90 micron sieve confirming to IS : 460 – 1962 and a Brush.
Procedure:
a) Break down any air-set lumps in the cement sample with fingers.
b) Weigh accurately 100 gms of the cement and place it on a standard 90 micron IS.sieve.
c) Continuously sieve the sample for 15 minutes.
d) Weigh the residue left after 15 minutes of sieving. This completes the test.

Result:
The percentage weight of residue over the total sample is reported.

                                         Wt.of  Sample Retained on the Sieve
% Weight of Residue =     
                                              Total Weight of the Sample

Limits:
The percentage residue should not exceed 10%.
Precautions:
Sieving shall be done holding the sieve in both hands and gentle wrist motion, this will involve no danger of spilling the cement, which shall be kept well spread out on the screen. More or less continuous rotation of the sieve shall be carried out throughout sieving.

Washers, shots and slugs shall not be used on the sieve. The underside of the sieve shall be lightly brushed with a 25 or 40 mm bristle brush after every five minutes of sieving.

Mechanical sieving devices may be used, but the cement shall not be rejected if it meets the fineness requirement when tested by the hand method.



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