The cement considers unsound if it undergoes a large change in volume (expansion) that causes cracking of hardened cement paste when it is under the condition of restraint.

Apparatus Required: Le-Chateliers Apparatus, Water bath, Vernier Caliper, Weighing Scale.

Procedure :

1. Place the lightly oiled mold 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. Cover the mold with another piece of lightly oiled 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.

3. Measure the distance separating the indicator points to the nearest 0.5 mm. Submerge the mold again in water at the temperature prescribed above.

4. Bring the water to boiling, with the mold kept submerged, in 25 to 30 minutes, and keep it boiling for three hours. Remove the mold from the water, allow it to cool, and measure the distance between the indicator points.

5. The difference between these two measurements indicates the expansion of the cement. This must not exceed 10 mm for ordinary, rapid hardening, and low heat Portland cements. If in case the expansion is more than 10 mm as tested above, the cement is said to be unsound.

Observation And Recording:

Soundness/expansion of cement = L1-L2
L1=Measurement taken after 24 hours of immersion in water at a temp. of 27 ± 20C
L2=Measurement taken after 3 hours of immersion in water at boiling temperature.
Calculate the mean of two values to the nearest 0.5 mm.