What is Soundness Property of Cement?
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Once the concrete paste sets, and it does not go any appreciable change in a volume called Soundness.
Cement has some quantity of lime, magnesia, and sulfate which changes in volume with time elapses causing cracks in concrete.
Methods used to determine soundness :
a) Le Chateliers method:
The expansion does not exceed 10mm for OPC.
The expansion should not exceed 0.8 mm.
When it comes to soundness property, we generally go for the hardening ability of cement paste to retain its volume after setting without delayed destructive expansion. And the destructive expansion is caused by excessive amounts of free lime (CaO) or magnesia (MgO).
The soundness of cement determines the strength of cement to maintain its volume as soon as it gets solidified. If once the cement mortar gets dried, then there isn’t any change in volume. If any change in volume occurs, then it allows the cement to inflate or contract. So, these cracks may take place.
Soundness of cement is determined by two methods, they are;
Ability of cement to retain its volume after getting hardened is known as the soundness of cement.
We can also say that the test conducted to identify the excess amount of lime in cement is known as the soundness of cement.
Two methods are there for measuring soundness of cement.
The soundness property of cement is mainly affected by the type of oxide present in the mass. Particularly magnesium and calcium oxide, if present in mass, then expansion of cement mass takes place after setting and hardening, which will ultimately cause disruption and crack in the concrete. This affects the durability of concrete structures due to expansion or due to volume change. It is soundness.
So for cement, if volume change will occur, cement can be called as unsound cement.
For finding this property, two methods are adopted:
1- Le- Chatelier apparatus: when only lime is only present.
expansion/distance between two indicator points should not be greater than 10mm
2- autoclave expansion test: for lime and magnesia both
The expansion should not be higher than 0.8%.
The soundness of a material is the ability of the material to retain its volume after hardening without excess expansion.
Now coming to the soundness of concrete,
Concrete is made up of cement, aggregates, water and admixtures. Of this, only cement has expansive properties.
Therefore soundness of concrete is can be related to the soundness of cement. This expansive behavior is caused due to excess lime in the cement. The excess lime CaO hydrates very slowly to form slaked lime. This slaked lime is higher in volume than the initial lime. This causes volume changes and results in high volume.
The same phenomenon can be observed in the cement having high traces of the magnesium oxide.
The excess volume may also be caused by the sulfate attack where the sulfate components in the cement react with the environment to produce calcium sulphoaluminate, which is very high in volume.
The soundness of the cement can be improved if the above-mentioned mishaps are avoided. Soundness can be found using Le – Chatelier’s apparatus, where we subject the cement to an environment that challenges the soundness of the cement. A cement of 10 mm or less expansion is accepted.
The Soundness test by Le- Chatelier’s apparatus is explained in detail here TheConstructor.org
The soundness property is related to the cement in the concrete.
Soundness is the property of cement to retain its volume after setting. There should not be any expansion in the cement. The volume change in the cement may be caused by excess amounts of lime, magnesium and calcium sulphate.
Soundness of cement can be tested using the Le’- Chateliers’s Experiment, where the maximum expansion of the cement can be 10 mm.
Soundness refers to the ability of hardening cement to retain its volume after setting with any destructive expansion.
Unwanted destructive volume expansion occurs due to free lime and magnesia.
Effect of unsound concrete
The soundness test is performed to identify the soundness property of cement.
Soundness is the property of cement to resist large volume change once it is hardened.
2 Tests are conducted to find out the soundness of cement.
Soundness refers to the ability of a hardened cement paste to retain its volume after setting without delayed destructive expansion. This destructive expansion is caused by excessive amount of free lime Cao or magnesia Mgo.
Soundness property of cement is checked by Le-chatelier method as per IS:4031 (part-3) 1988.