Casagrande Test for Liquid Limit of Soil: Lab Procedure, Observation & Result

“Liquid limit of soil is the minimum water content at which a pat of soil cut by a groove of standard dimension will flow together for a distance of 12 mm under an impact of 25 blows in the apparatus (Casagrande Apparatus)”

This test is also called Casagrande Test because of the use of the Casagrande apparatus.

  1. Apparatus Required  

1. Casagrande’s liquid limit device

2. Grooving tools of both standard and ASTM types

3. Oven

4. Evaporating dish or glass sheet

5. Spatula

6. 425 micron IS sieve

7. Weighing balance having an accuracy of 0.01g.

8. Wash bottle.

  2. Procedure of Casagrande Test  

~ Casagrande’s liquid limit device is used for determining the liquid limit. Setup the device by adjusting the drop of the cup utilizing screws. The drop height should be exactly 1 cm.

~ Take a soil sample passing through the sieve of 0.425 mm. Generally. 120 gm of sample is used for the test.

~ Make a paste of soil using distilled water. Mixing should be done for about 15-30 minutes until a uniform mix is obtained.

~ For obtaining uniform moisture distribution; the mix is placed under humid conditions.

~ Place the mix on the metal brass cup and level horizontally using a knife or spatula.

~ Divide the soil into two portions using the grooving tool.

~ Rotate the liquid limit device at the rate of 2 revolutions per second.

~ Record the number of blows (N) to close the bottom of the groove through a distance of 12 mm.

~ Determine the water content (W) using the oven drying method.

~  Water content at 25 no. of blows is taken as the liquid limit value.

~  Draw the flow curve between log N and W; determine the liquid limit corresponding to N=25.

~ The test should be done at least 3 times.

  3. Datasheet for Casagrande Test

  4. Result of the Casagrande Test

Draw a flow curve between log N and w.

Liquid limit (for N=25) =