Soundness of cement

AIM
To determine the soundness of the given sample of cement by "Le Chatelier" Method.

APPARATUS
Le Chatelier apparatus conforming to IS 5514-1969, Balance, Weights, Water bath.

THEORY
It is essential that the cement concrete shall not undergo appreciable change in volume after setting. This is ensured by limiting the quantities of free lime, magnesia and sulphates in cement which are the causes of the change in volume known as unsoundness. 
Unsoundness in cement does not come to surface for a considerable period of time. This test is designed to accelerate the slaking process by the application of heat and discovering the defects in a short time. Unsoundness produces cracks, distortion and disintegration there by giving passage to water and atmospheric gases which may have injurious effects on concrete and reinforcement.
The apparatus for conducting the test consists of small split cylinder of spring brass or other suitable metal of 0.5mm thickness forming a mould 30 mm internal diameter and 30mm high. On either side of the split mould are attached to indicators with pointed ends, the distance fromthese ends to the center of the cylinder being 165 mm. The mould shall be kept in good condition  with the jaws not more than 50mm apart.



PROCEDURE:
1. Place the lightly oiled mould on a lightly oiled 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.

2. 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

3. 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 27°- 2°C and keep there for 24 hours.

4
. Measure the distance separating the indicator points.

5. Submerge the moulds again in water at the temperature prescribed above.

6. Bring the water to boiling, with the mould kept submerged for 25 to 30 minutes, and keep it boiling for three hours.

7. Remove the mould from the water allow it to cool and measure the distance between the indicator points.

8. The difference between these two measurements represents the expansion of the cement.

9. For good quality cement this expansion should not be more than 10mm.

OBSERVATIONS:
Initial distance between the indicator points in mm =
Final distance between the indicator points in mm =
Expansion in mm = final length - initial length =

RESULT
Expansion in mm
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