What is Soundness test of cement?
The soundness test of cement is one of the methods to determine the volume change in cement and concrete after the setting. Excessive expansion after the setting is said to be unsound.
It is done by two methods namely Le-Chatelier Method and the Auto-Clave test. Le- Chatelier Method is only applicable for that cement containing free lime while Auto-Clave tests cement containing both free lime and magnesia. Here, free indicates unburnt during the manufacturing process.
Why to do Soundness test of cement?
The free lime and free magnesia obtained in cement causes unsound cement. Free lime (CaO) and Magnesia (MgO) are known to react with water very slowly and increase in volume considerably, which result in cracking, distortion and disintegration.
When cement gets unsound, large expansion is seen after the setting also. This causes disrupting of the hardened mass causing problems of cracks which in turn causes durability loss in structure. Soundness test of cement determines the volume expansion after the setting of cement.
Below are the steps to perform soundness test of cement by Le-Chateliers Method according to IS : 5514-1969.
- Le-Chateliers Apparatus (small split spring brass cylinder of thickness 0.5mm, internal diameter 30mm, and 30 mm height. On either side of split 2mm brass pointed wire is attached in such a way that the distance of these ends to the center of the cylinder is 165mm)
- Two glass plates of more than 32mm×32mm size.(to cover the apparatus)
- Tray (to mix cement and water sample)
- Trowel (to mix cement and water sample)
- Weighing Machine (to weight cement and water)
- Vernier Calliper (to measure the expansion of pointed wires)
- Take a cement sample of either of the weight given in Table 1 obtained from IS 4031(Part 3):1988 Methods of Physical Test for Hydraulic Cement: Determination of Soundness.
|Weight (g)||Permissible Variation on Weights in use Plus or Minus (g)|
Let us take 100gm of cement sample.
- Prepare a cement paste formed by mixing cement with 0.78 times the water required to give a paste of standard consistency.
- Place the lightly oiled Le-Chateliers apparatus on a lightly oiled glass plate and fill it with the cement paste prepared.
- Cover the Le-Chateliers apparatus with another piece of the lightly oiled glass plate, place a small weight on this covering glass plate and immediately submerge the whole assembly in the water at a temperature of 27 ± 2°C and keep there for 24 hours.
- After 24 hours take the apparatus out of the water and measure the distance between the indicators i.e, pointed wires.
- Again submerge the whole apparatus inside boiling temperature water (100°C) for 3 hours. After that let the whole apparatus to cool down to room temperature.
- Then again measure the expanded indicator distance.
Water to be mixed = 0.78*P% of cement, where P= standard consistency
Example; for P=25%
Water in ml= 0.78*(25/100)*weight of cement in gm
Soundness/expansion of cement = L1 – L2
L1 = Measurement taken after 24 hours of immersion in water at a temp. of 27 ± 20°C
L2 = Measurement taken after 3 hours of immersion in water at boiling temperature.
|Cement types||Permissible soundness/expansion|
Where, OPC= Ordinary Portland Cement
RHC=Rapid Hardening Cement
LHC= Low Heat Cement
PCC= Portland Pozzolano Cement
HAC= High Alumina Cement
SSC= Super Sulphate Cement
If the obtained value of soundness is more than permissible than the cement is said to be unsound. To cross-check this cement, another experiment called aeration + le-Chateliers method is done.
In this test, at first, the cement is aerated by spreading out to a depth of 75 mm and store it for 7 days in an atmosphere maintained at 27±2°C and relative humidity of 50 to 80 percent.
After this, a cement sample of required weight for the Le-Chateliers Method is taken from the aerated sample and the same steps explained above are done.
If the result obtained again is above the permissible value, then the sample is not preferred in construction.
- Split in the cylinder must be measured at the tip of the indicator.
- Measure the distance separating the indicator points to the nearest 0.5 mm.
- Weight error should be in permissible range given in table no 1.
I hope this post remains helpful for you.
Happy Learning – Civil Concept
Civil Engineer – Pradip Dahal