What is the Soundness of Cement?
The soundness of cement can be defined as its ability to retain its volume after it gets hardened. This means that a properly sound cement will have hardened paste’s ability to retain its volume after setting.
A cement is referred to as unsound, lacking soundness when subjected to delayed destructive expansion.
Unsoundness of cement is due to the presence of an excessive amount of hard-burned free lime or magnesia.
The soundness of cement indicates quality to expand on the setting. Unsound cement expands too much on setting and develops cracks in the structure.
The test used for determining the soundness of cement is known as the “Le chatelier apparatus test.”
By soundness of cement, it is understood that its capacity to form a non-disintegrating, hard uniformly strong mass on the setting.
Soundness of Cement Test Methods
The cement after setting must not undergo any appreciable change of volume. Certain types of cement have undergone a large expansion immediately after settling, disrupting the hardened mass and set. This will cause major difficulties for the durability of structures if such type of cement is used.
On the other hand, the unsoundness in cement is due to an excess of free lime combined with acidic-oxide at the kiln. This is also likely that too high a proportion of magnesium content of calcium sulfate content may lead to cement unsoundness.
The soundness of cement can be determined by two methods:
- The autoclave method and
- The Le-Chatelier method.
In the soundness test, a specimen of hardened cement paste is boiled for a fixed time so that any tendency to expand is speeded up and can be detected. Soundness means the ability to resist volume expansion.