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Determine Free Swell Index Of Soil

To determine the free swell index of soil as per IS: 2720 (Part XL) – 1977. Free swell or differential free swell, also termed as free swell index, is the increase in volume of soil without any external constraint when subjected to submergence in water. The apparatus used :

i) IS Sieve of size 425µm

ii) Oven

iii) Balance, with an accuracy of 0.01g

iv) Graduated glass cylinder- 2 nos., each of 100ml capacity

strong>Procedure to determine Free Swell Index Of Soil
i) Take two specimens of 10g each of pulverised soil passing through 425µm IS Sieve and oven-dry.

ii) Pour each soil specimen into a graduated glass cylinder of 100ml capacity.

iii) Pour distilled water in one and kerosene oil in the other cylinder upto 100ml mark.

iv) Remove entrapped air by gently shaking or stirring with a glass rod.

v) Allow the suspension to attain the state of equilibrium (for not less than 24hours).

vi) Final volume of soil in each of the cylinder should be read out.

Free swell index = [Vd – Vk] / Vk x 100%
Vd = volume of soil specimen read from the graduated cylinder containing distilled water.
Vk = volume of soil specimen read from the graduated cylinder containing kerosene.

Free Swell


Degree of





















Very high




We are thankful to Er Jithesh for submitting the table to us


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Kanwarjot Singh

Kanwarjot Singh is the founder of Civil Engineering Portal, a leading civil engineering website which has been awarded as the best online publication by CIDC. He did his BE civil from Thapar University, Patiala and has been working on this website with his team of Civil Engineers.

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29 comments on "Determine Free Swell Index Of Soil"

Yogendra says:

with such notes, things becomes easy to learn

Rambha says:

Thanx a lot for making my search easier. Its a great help

Bijan says:

Thanks alot

raj says:

What is the minimum limit of Free Swell as per I.S for filling purpose

suman kumar says:

first of all its not minimum but maximum limit & as per MORT&H specifications for roads and bridge work the maximum limit is 50 %(cl.305.2.1.2.). In any case this limit should not exceed for filling materials.

Motiul says:

It was really helpful to me.Thnx a lot..

M K GUPTA says:

This is realy very useful for civil engineers

kaushik jadav says:

what is the minimum limit of free sweel index and free sweell presser as per IS for back filling pourpoues.

tonya basar says:

thanks its was very helpful

Nilesh Korde says:

Thanks for giving easy notes

Daramola sunday says:

Thanks for these easy and straight forward notes

Mokhtar Sayed says:

Thanks alot for help

Manoj Chaudhary says:

A soil have liquid limit is 21 & plastic limit is 19. Pl. conferm me this soil is sutable for back filling?

madan s ambulgekar says:

pl. i want to know what will be the minimum F.S.I. of soil and will be the maximum F.S.I. of soil of any categaory.

Bharat Singh Rawat, Roorkee says:

Excellent website.


thank you so much for your help.

Jayanthan says:

what is the meaning of “Talus”?

Akshay kanade says:

Why free swell test is calculated

Meeran says:

I want to know what is the limitation for free swell index…pls send me..

uwaoma b.u says:

is there difference between free swell and swell index

shoaib ahmad KGP SGR says:

how to determine cement content in hardened concrete,please

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