Liquid Limit Test of Soil Procedure by casagrande 2019

Liquid Limit test of soil procedure by Casagrande is required to find out the maximum limit of water which soil can hold. We described the procedure of liquid limit test of soil by Casagrande.


Liquid Limit of Soil

What is a Liquid Limit Test?

Liquid limit of soil indicates its water content by mixing the soil converts into a perfect paste. In easy word we can say, the liquid limit of a soil is the maximum water content which soil can hold before flowing.


Why do We do Liquid Limit Test?

To know the quality and class of soil.


Liquid Limit Test IS code

The IS code used for the liquid limit test is IS 2720 part 5.


Atterberg Limit

 Liquid limit and Plastic limit comes under Atterberg limit. Which means Plasticity index.


Plasticity index = Liquid limit – Plastic limit


Liquid Limit Test Apparatus

  1. Casagrande apparatus
  2. Grooving tool
  3. Evaporating dish
  4. Glass plate to mix soil with water
  5. Spatula to mix
  6. Weighing balance ( capacity minimum – 500 gram, least count – 0.01 gram )
  7. Hot air oven to maintain the temperature 100 to 110 degree centigrade.
  8. Containers to take soil sample
  9. IS Sieve 425 microns

Liquid Limit Test Equipment

Liquid Limit Test


Precautions Before Test

  • Check the Casagrande apparatus, whether it’s working properly or not.
  • It should be clean.
  • Check the falling distance of Casagrande cup. It must be 10 mm.
  • To adjust the falling distance, place the adjustment plate under the cup and tight adjustment screw.
  • Ensure that the cup falls freely.


Liquid Limit Test Procedure

  • Soil sample for the test should be in natural dry condition or oven-dry condition, but its temperature shall be similar to the atmosphere while testing.
  • Take soil and sieve it by 425 microns.
  • Take near about 150 grams of passed soil through 425 microns.
  • Add distilled water and soil in evaporating dish and mix it with spatula properly until mix convert into a paste.
  • It should not take long time maximum of 5 minutes.
  • After mixing, a part of paste shall be placed in Casagrande cup adjusted with the adjustment plate.
  • Spread the paste in the cup and cut it with groove tool across dia towards our body.

Liquid Limit Test of Soil

  • Clean the area between both soil parts y grooving tool and ensure that the distance between both parts is 12 mm.
  • Remove the adjustment plate from under the cup.
  • Immediately start moving Casagrande handle in clockwise, in speed 2 revolutions (blows) in one second.
  • Carefully stop moving handle when both side of soil paste come in contact.
  • See the revolutions number it must be between 15 to 35. If it is not, then repeat the taste. If it is, then note down the revolutions/blows number

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  • Take the soil paste sample in a container not less than 50 gram.
  • Note down the container serial number and weight of soil sample weight.
  • Take some soil passed through 425 microns and mixed thoroughly with water.
  • Four readings are required for the liquid limit test between 15 to 35 blows.
  • Always remember that for a good graph we should get two reading between 15 to 25 blows and the next two readings between 25 to 35 blows or revolutions.
  • If we get 30 to 35 bows reading in the first attempt then for 15 to 25 blows we should add a bit more water than we added in the previous paste.
  • For more bows, less water required and for fewer blows, a bit more water required.
  • Repeat the test until you get four readings between 15 to 35 blows.
  • Note down each blows with container number and container weight with soil sample
  • Watch the video for better understanding below.


How is Liquid Limit Calculated?

Formula to calculate liquid limit of soil is (water weight/dry soil weight)*100

But the liquid limit shall be calculated as per graph on 25 penetration if you are using Casagranda apparatus. I recommend you to watch my video for the better.


Liquid Limit Test Lab Report


Liquid Limit Test Graph



Liquid Limit Test Practical Video


Liquid limit Test Calculation, Report and Graph Video

I recommend this video for calculation and graph, I have prepared.


Liquid Limit Limits [Atterberg Limits]

ActivityLiquid Limit ( max )Plasticity Index ( max )
Embankment / Subgrade7045
Granular sub-base256
Wet Mix macadam6

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Viva Questions on Liquid Limit Test

Q.1  What is liquid limit of a soil?

Ans. the liquid limit of a soil is the maximum water content which soil can hold before flowing


Q.2  How to choose liquid limit test apparatus between casagranda and cone penetrometer?

Ans. Even we use 425 microns passed material –

Casagranda apparatus shall be used for fine-grained soil, silty and clayey soil, where very fine particles are available in soil.

Cone penetrometer apparatus shall be used for coarse-grained soil or material like granular sub-base, wet mix macadam and bituminous concrete, etc.


Q.3  What is the IS code for liquid limit test?

Ans. IS code 2720 part 5.


Q.4  What is the rate of blows given to the soil pad in liquid limit is?

Ans. The rate of blows given to the soil pad in liquid limit is 2 blows per second.


Q.5 What is the limit of blows for Casagranda apparatus and cone penetrometer during the test?

Ans. The limit of blows for Casagranda apparatus is 15 to 35.

The limit of blows for cone penetrometer apparatus is 14 to 28.


Q.6  On which blows number, the liquid limit shall be considered for Casagranda apparatus and cone penetrometer apparatus in the graph?

Ans. For Casagranda apparatus, the liquid limit shall be considered on 25 blows in the graph and for cone penetrometer apparatus, the liquid limit shall be considered on 20 blows in graph. 


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Student Corner

Screened until sufficient soil is collected to perform the test. A loamy soil must be tested immediately after thorough mixing with water. 

In case of cracking of the groove sides or slippage of the soil, the groove may be cut in steps. 

The number of drops was recorded and then the soil was removed and placed in the first of the moisture cans and placed in the oven. 

Then, additional water was added to the bottom in the porcelain evaporating dish, and then the bottom was put in the apparatus to perform another test with a higher water content than the first one. 

After one day, the moisture doses were weighed and the moisture content of each sample determined. 

The moisture content in percent, at which the volume of the soil mass no longer changes, is defined as the shrinkage limit (Das, 1998). 

The limits for liquids and plastics are determined by relatively simple laboratory tests, which provide information on the nature of connected soils. 

Engineers extensively use these tests to correlate several physical soil parameters as well as soil identification.


The liquid limit (II) is conceptually defined as the water content at which the behavior of a clayey soil change from the plastic to the liquid state.

However, the transition from plastic to liquid behavior occurs gradually over a range of water contents, and the shear strength of the soil is not actually zero at the liquid boundary. 

The precise definition of the liquid limit is based on the standard test methods described below.

The non-dewatered shear strength of soil from the water content around the liquid limit to the water content around the plastic limit can be determined by the falling cone test.

The determination of the liquid limit by the falling cone test is based on the assumption that the soil at the liquid boundary assumes a unique condition giving a unique shear strength. 

When the unrestrained shear strength is related to the liquid and the plastic limit, it is emphasized that the liquid limit and the plastic limit could also be clearly related.

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