This document summarizes the liquid limit and plastic limit tests conducted on a soil sample. The liquid limit was found to be 51.679% using two different methods that produced similar results. The plastic limit was 24.525%. Based on these Atterberg limits, the soil was classified as clay with high plasticity. The limits help characterize the soil's engineering properties and behavior when wet or dry. The experiment showed the soil behaves plastically when wet and becomes hard when dry, typical of clays.

1. University of Sulaimani
College of Engineering
Civil Engineering Department
(Soil Mechanics Lab)
Name of the Test: Liquid Limit & Plastic Limit Test
Test No. :
Students Name:
1- Zhyar Abubakir
2- Rawezh Saady
3- Raz Azad
Group & Sub-Group: A1-A6
Date of the Test:

2. Introduction:
The liquid limit (LL) It is defined as the percentage moisture content at
which a soil changes with decreasing wetness from liquid to plastic
consistency or with increasing wetness from plastic to liquid
consistency. It is the water content at which a soil changes from plastic
to liquid behavior.
The plastic limit (PL) is the water content, in percent, at which a soil can
no longer be deformed by rolling into 3.2 mm (1/8 in.) diameter threads
without crumbling. In other words, it is the percentage moisture content
at which a soil changes with decreasing wetness from the plastic to the
semi- solid consistency or with increasing wetness from the semi-solid
to the plastic consistency.
Those limits of soil are very important property of fine grained soil and
its Value issued to classify fine grained soil and calculate activity of
clays and toughness index of soil. Moreover, it also gives us information
regarding the state of consistency of soil onsite. In addition, it also can
be used to predict the consolidation properties of soil while calculating
allowable bearing capacity & settlement of foundation.

3. Purpose:
The main purpose of this test is to determine the liquid limit and plastic
limits which are known as atterberg limits, this testing method is used as
an integral part of several engineering classifications systems to
characterize the fine‑ grained fractions of soils and to specify the
fine‑ grained fraction of construction materials. The liquid limit, plastic
limit and plasticity index of soils are also used extensively, either
individually or together, with other soil properties to correlate with
engineering behavior such as compressibility, permeability,
compatibility, shrink‑ swell and shear strength.

4. Equipment:
1-Casagrande Liquid limit Device.
2-Grooving tool.
3-Moisture cans.
4-Porcelain evaporating dish.
5-spatula.
6-oven.
7-Balance sensitive up to (0.01g).
8-Plastic squeeze bottle.
9-Paper towels.
10- Ground glass plate.

5. Procedure:
Liquid Limit:
1-Determine the weight of the three moisture cans (W1).
2-Take about 250g of air dry soil passing No.40 sieve in an evaporating
dish. Add water from the plastic squeeze bottle and mix the soil to form
of a uniform paste.
3-place a portion of a paste in the brass cup of the liquid limit device.
Using the spatula, smooth the surface of the soil in the cup such that the
maximum depth of the soil is about 8mm.
4-Using the grooving tool, cut along the centerline of the soil pat in the
cup.
5-Turn the crank of the liquid limit device at the rate of about 2
revolutions per second. By this, the liquid limit cup will rise and drop
through a vertical distance of 10mm once for each revolution.
The soil from two sides of the cup will begin to flow toward the center.
Count the number of blows, N, for the groove in the soil to close through
a distance of (0.5) in (12.7mm).
If N = about 25 to 35, collect a moisture sample from the soil in the cup
in a moisture can .Close the cover of the can and determine the weight of
the can plus the moist soil (W2).
Remove the rest of the soil paste from the cup to the evaporating dish.
Use paper towels to clean the cup well.
If the soil is too dry, N will be more than about 35.In that case ,remove
the soil by the spatula to the evaporating dish. Clean the liquid limit cup

6. well with paper towels. Mix the soil in evaporating dish with more water
and try again.
If the soil is too wet N will be less than about 25, In that case ,remove
the soil by the spatula to the evaporating dish. Clean the liquid limit cup
well with paper towels. Stir the soil paste with the spatula for some time
to dry it up . The evaporating dish may be placed in the oven for a few
minutes for drying also .Do not add dry soil to the wet soil paste to
reduce the moisture content for bringing it to the proper consistency.
Now try again in the liquid limit device to get the groove closure of
(0.5)in.(12.7mm)between 25 to 35.
6-Add more water to soil-paste in the evaporating dish and mix
thoroughly. Repeat steps 3,4 and 5 to get groove closure of
(0.5in.)((12.7mm) in the liquid limit device at a blow count, N=20 to 25.
Take a moisture sample from the cup .Remove the rest of the soil paste
to the evaporating dish, clean the cup with paper towels.
7- Add more water to soil-paste in the evaporating dish and mix well,
Repeat steps 3,4 and 5 to get blow count N , between 15 to 2 to get
groove closure of (0.5in.)((12.7mm) in the liquid limit devic.Take a
moisture sample from the cup.
8-Put the three moisture cans in the oven to dry to constant weights W3.
(The caps of the moisture cans should be removed from the top and
placed at the bottom of the respective cans in the oven.)

7. Plastic Limit:
1-Take approximately 20 grams of a representative soil sample which is
passing through no. 40 sieve (air dry) in a porcelain evaporating dish.
2-Add water from the plastic squeeze bottle to the soil and mix
thoroughly .
3- Take the weight of a moisture can and record it on the data sheet
(W1).
4. From the moist soil prepared in step 2, prepare several ellipsoidal-
shaped soil masses by squeezing with fingers.
5-Take one of the ellipsoidal-shaped soil masses (step 4) and roll it
on a ground glass plate using the palm of the hand (fig.7.1).the rolling
should be done at the rate of about 80 strokes/minuet. Note that one
complete backward and one complete forward motion of the palm
constitutes a stroke.
6- When the thread being rolled in step 5 reaches 1/8-in. (3.18 mm) in
diameter, break it up into several small pieces and squeeze it with
fingers to form an ellipsoidal mass again .
7- Repeat steps 5 and 6 until the thread crumbles into several pieces
when it reaches a diameter larger than 1.8-in (3.18 mm) it is possible
that a thread may crumble at a diameter larger than 1/8-.in (3.18 mm)
during a given rolling process, whereas did not crumble at a diameter of
1/8-in. (3.18 mm) during the previous rolling. This is. However,
satisfactory.
8- Collect the small crumbled pieces in the moisture can and close the
cover .

8. 9-Take the other ellipsoidal soil massed formed in step 4 and repeat
steps 5 through 8.
10-Take the weight of the moisture can plus the wet soil (W2). Remove
the cap from the top of the can and place it (with the cap at the bottom of
the can) in the oven.
11. After about 24 hours, remove the can from the oven and take the
weight of the can plus the dry soil (W3).

9. Calculation:
Liquid Limit:
Moisture content (w %) =
𝑊2−𝑊1
𝑊3−𝑊1
*(100)
1- Can No. ( 6 )
W1=67.29g , W2=94.47g , W3=85.59g
(w %) =
94.47−67.29
85.59−67.29
* (100) = 48.525%
2- Can No.( 8 )
W1=64.99g , W2=84.71g , W3=77.89g
(w %)=
84.71−64.99
77.89−64.99
* (100)= 52.868%
3- Can No.(19)
W1=75g , W2=93.17g , W3=86.68g
(w%)=
93.17−86.68
86.68−75
* (100)=55.565 %
Liquid limit value by US. Army waterways experiment Station
(1949):
LL= WN (%) (
𝑁
25
)0.121
LL=48.525*(
23
25
)0.121
= 48.038%
Liquid limit from the graph=51.679%

10. Plastic Limit:
PL= (W2-W3)*100/ (W3-W1)
Can No.(18):
W1=68.96g
W2=76.17g
W3=74.75g
PL= (76.17-74.75)*100/ (74.75-68.96)= 24.525%
PI=LL-PL
PI=51.679 - 24.525=27.154

11. Table of Results:
Liquid Limit:
LL (liquid limit) =51.679%
Plastic Limit:
PI (Plasticity index) =27.154
Can
no.
Weight of can,
W1 (g)
weight of can + wet soil
, W2 (g)
Weight of can + dry
soil,W3(g)
Moisture Content
(w %)
Number of
blows (N)
6 67.29 94.47 85.54 48.525 34
8 64.99 84.71 77.89 52.868 23
19 75 93.17 86.68 55.565 12
Can
No.
Weight of Can,W1
(g)
Weight of can + wet
soil,W2(g)
Weight of can + dry soil,W3(g) PL(%)
18 68.96 76.17 74.75 24.525

12. Graph:

13. Discussion & Conclusion:
Atterberg limits are a basic measure of the nature of a fine-grained soil. Depending
on the water content of the soil, it may appear in four states: solid, semi-solid,
plastic, and liquid.. The boundary between these states can be defined using the
change in behavior of the soil. The Atterberg limits are commonly used to
distinguish between silts and clays, and also types of silts and clays. Atterberg
limits like the liquid limit, the plastic limit and the plasticity index of soils are also
used widely, either individually or together, with other soil properties to correlate
with engineering behavior such as compressibility, permeability, shrink swell,
shear strength, and compaction.
Liquid limit of soil can also be used to predict the consolidation properties of soil
while calculating allowable bearing capacity and settlement of foundation. Also,
liquid limit value of soil is also used to calculate activity of clays and toughness
index of soil.
For this experiment regarding to the results we notice that liquid limit is equal to
(51.679%), and also we calculated it by US. Army waterways experiment Station
(1949) which was (48.038%) these value aren’t equal but they are approximate,
also we determined plastic limit equal to (24.525%).
After thorough analysis of the Atterberg limits of the soil sample, it is concluded
that the soil is classified as clay with high plasticity under the Unifies Soil
Classification System.
Clays are known to be the plastic fines. They have low resistance to deformation
when wet, but they dry to hard, cohesive masses. Clays are virtually impervious,
difficult to compactwhen wet, and impossible to drain by ordinary means. Large
expansion and contraction with changes in water content are characteristics of
clays. The small size, flat shape, and mineral composition of clay particles
combine to producea material that is bothcompressible and plastic. Generally, the
higher the liquid limit of a clay, the more compressible it will be and at the same
liquid limit, the higher the plasticity index, the more cohesive the clay. The clay
used in the experiment probably contains high amount of silts that affects its
plasticity and making it not to compressible as compared to clays with high

14. plasticity. Lean clays easily turns into mud as compared to fat clays and hence the
careful analysis in the planting the foundations is more needed.
References:
 https://www.academia.edu/28124222/Lab_Report_2_Li
quid_Limit_Plastic_Limit_and_Plasticity_Index_of_Soi
ls.
 Soil Mechanics Laboratory Manual.
 http://civilengineeringlaboratory.blogspot.com/2012/02/l
iquid-limit-and-plastic-limit-tests.html