Theroy-

• The soundness of cement is that property by virtue of which it maintains a constant volume or doesn't undergo any observable expansion. It is a measure of cement’s stability during the change in it's volume after the process of setting and hardening has taken place.

• The test is important to carry out on cement because unsoundness leads to cracks and distortion in cement which are produced due to the expansion of excessive free lime. These cracks allow the entry of water and atmospheric gases which may be injurious to the structure, thus affecting its overall durability. Hence, this test specifies the optimal quantity of free lime to be used in the cement sample.

• The unsoundness effect is not quite evident for a significant period of time. Therefore, accelerated test such as Le- Chatelier’s experiment is performed to ascertain this effect in a short span.

Apparatus-

1. Le-Chatelier’s apparatus conforming to IS: 5514-1969.
2. Balance.
3. Weights.
4. Glass plates.
5. Water bath.