How to determine the soundness of cement

How to determine the soundness of cement?

                                      Soundness Test
Scope:
             This method applies to common cements only. It may not apply to cements types e.g; which have a very short initial setting time.

Principle:
          The soundness is determined by observing the volume expansion of cement paste of standard consistency as indicated by the relative movement of two needles.

Apparatus:
 1. Le Chatelier Apparatus
                      It consists of a mold which is made up of a non-corrodible spring metal e.g; brass and having a radius of 30 mm and thickness of 0.5 mm and two indicator needles having a length of 150-165 mm. The resilience of the mold shall be such that the action of a mass of 300 g applied shall increase the distance between the indicator needles by not less than 150 mm without permanent deformation.

2. Water Bath
              With means of heating capable of raising the temperature of the water from 20C to boiling in 30 minutes.

3. Humidity Cabinet
              Maintained at 20C and 90% relative humidity.

                                                                      

                               

Note:
     1.   Loops shown on each side of the central split facilitates demolding of the hardened paste   specimen after test.
    2.   A pair of base and cover plates of impermeable material, non-corrodible by cement paste shall be provided for each mold. Each plate shall be larger than the mold. The cover plate shall weigh at least 75 g.

Procedure:
  1.     Prepare a cement paste of standard consistency and fill the cement paste in the Le Chatelier mold using your hands and level the top of the surface of the mold with a straight-edged implement.

2.      Cover the mold with a glass plate and place weight over it.

3.       Place this assembly in the humidity cabinet at temperature of 20C and 90% humidity.

4.       Measure A = Distance between the indicator points/needles after 24 hours period.

5.       Heat the mold at boiling and keep it in water for 3 hours at boiling temperature.

6.       Measure B = Distance between the indicator points/needles after 3 hours.

7.       Allow the mold to cool at room temperature and measure C = Distance between the indicator
          points/needles after cooling.

                                    Soundness =   C – A
Note:
    Specification Limit for cement is 10 mm. If the soundness value exceeds this limit than a retest should be done.
      Retest can be done on the fresh cement after storing it for 7 days in an atmosphere at 20C and not less than 50% humidity. Then retest the cement.

Calculations:

A = 17 mm
B = 13 mm
Soundness = C – A = 17-13 = 4 mm
Soundness value is 4 mm < 10 mm. This indicates that expansion is less and there will be less chances of cracking .If the value comes out to be greater than 10 mm than this cement can’t be used because it will have excessive cracking.

Results:

      For a paste of standard consistency we measured C-A which came equal to 4 mm and less than the standard specification limit of 10 mm. Hence we can say that this cement is sound.