CENTRAL MINDANAO UNIVERSITY
University Town, Musuan, Maramag, Bukidnon
College of Engineering
Department of Civil Engineering
CE 34.1 Geotechnical Engineering 1 – Soil Mechanics
Laboratory
Plastic Limit and Liquid Limit Test
(Sieve Analysis)
Title of experiment
Submitted By:
Timtim, Karl Frances L.
BSCE 3B
Date performed:
May 29, 2021
I.
BACKGROUND OF THE EXPERIMENT
The liquid and plastic limit are water contents at which the
mechanical properties of soil changes. They are applicable to finegrained soils, and are performed on soil fractions that pass the #40
(0.425-mm) sieve. The plastic limit is the water content where soil starts
to exhibit plastic behaviour. A thread of soil is at its plastic limit when
it is rolled to a diameter of 3 mm or begins to crumble. To improve
consistency, a 3 mm diameter rod is often used to gauge the thickness
of the thread when conducting the test. The liquid limit is the water
content where a soil changes from plastic to liquid behaviour. Casa
Grande subsequently standardized the apparatus and the procedures to
make the measurement more repeatable. Soil is placed into the metal
cup portion of the device and a groove is made down its centre with a
standardized tool. The cup is repeatedly dropped 10mm onto a hard
rubber base during which the groove closes up gradually as a result of
the impact. The number of blows for the groove to close for 13 mm (½
inch) is recorded. The moisture content at which it takes 25 drops of the
cup to cause the groove to close is defined as the liquid limit.
The liquid and plastic limits of many soils that have been allowed
to dry before testing may be considerably different from values obtained
on non-dried samples. If the liquid and plastic limits of soils are used to
correlate or estimate the engineering behaviour of soils in their natural
moist state, samples should not be permitted to dry before testing unless
data on dried samples are specifically desired.
II.
OBJECTIVE
The liquid limit and plastic limit tests provide information
regarding the effect of water content (w) on the mechanical properties
of soil. Specifically, the effects of water content on volume change and
soil consistency are addressed. The results of this test are used to
classify soil in accordance with ASTM D2487, and to estimate the swell
potential of soil. This information is used to classify the soil in
accordance with the Unified Soil Classification System (USCS).
III.
EQUIPMENT USED
The equipment used in this experiment consists of:
LIQUID LIMIT APPARATUS:
1. Triple Beam Balance
2. Soil Mixing bowl
3. #40 sieve (0.425-mm opening)
4. Distilled or demineralized water
5. Casa Grande
6. Temperature Controlled Oven
7. Fine-grained soil
8. Four Soil Moisture Containers
9. Markers
PLASTIC LIMIT APPARATUS:
1. Triple Beam Balance
2. Ceramic Soil Mixing bowl
3. #40 sieve (0.425-mm opening)
4. Distilled or demineralized water
5. Frosted Glass
6. 0.125-in. Diameter metal rod
7. Temperature Controlled Oven
IV.
SCHEMATIC DIAGRAM OF THE EQUIPMENT USED
TRIPLE BEAM BALANCE
CASAGRANDE SCHEMATIC DIAGRAM
TEMPERATURE CONTROLLED OVEN
V.
PROCEDURE
The students met up at MMEI laboratory located in
Bagontaas, Valencia City. The students conducted the
experiments with the guide of the personnel from the laboratory.
The students performed the experiment for the Liquid Limit and
Plastic Limit. The two experiment have different procedure and
was divided in to two parts of the Activity.
For the Liquid Limit, the students used the percentage of soil
which passes through #40 sieve and the students weighed the
sample and fuse it in the mixing bowl. A 15 ml of distilled water
was then added into the sample and carefully mixed the soil
sample together with water. The second and third trials used an
amount of water ranging from 1 ml to 3 ml to be poured into
sample. A frosting knife was used to put a portion of the sample
over the liquid limit device cup, making a half moon shape with
a thickness of 10mm. Six strokes from front to rear or back to
front might be considered as one stroke to avoid soil cake from
slipping at the cup. The students created a cut in the soil using a
grooving tool. The Casa Grande crank was rotated to a pace of 2
revolutions per second and closely monitored. The cup would
slide from a height of 1.0 cm for each crank. The total number of
blows in each trial was determined. The sample was placed to the
mixing bowl for the second and third trials, and the process
repeats. The students cleaned the cup and performed the
processes four times to ensure that the findings were accurate and
within a few cranks of each other.
For the Plastic Limit, after the students obtained a moisture
loss sample (LL test), an 8 g portion of the soil cake mixture was
removed. The soil sample was formed into little balls and blended
with water. The students rolled out a little ball-shaped soil sample
onto the glass to produce a 0.125-inch-wide rod. If the soil
crumbled during the initial take, additional water will be added,
and thus the operation then redone. They simply repeated the
process of making a rod, rolling it up in a ball between their
palms, generating a rod, till the soil crumbled. The crumbled soils
were collected in moisture cans, weighed, and the outcome
recorded. The moist weight of the soil was immediately
measured, and thus the samples had been subsequently heated at
110°F till it attained the constant weight. The water capacity of
the sample at this level is considered as the plastic limit (PL).
The samples are collected out of the oven, cooled, and measured.
The operation was conducted thrice, providing an average value
for plastic limit.
After all the experiment was performed, the students began
cleaning all the equipment used in the test and placed the
equipment used to where it belongs. And lastly, the students gave
thanks to the laboratory personnel for the help and time they
offered to the students in the activity.
VI. RESULTS
MEASUREMENT OF Plastic Limit and Liquid Limit (ASTM D4318)
LABORATORY DATA SHEET
General Information:
Tested By: MMEI
Date Tested: May 29, 2021
Lab partners/organization: Jaen Eudson Corotan, James Andrew
Modequillo Angelo Montesclaros, Nino Ortega, Karl Frances Timtim,
Earl Donnie Villaver
Client: BSCE 3B
Project: Plastic Limit and Liquid
Limit
Boring no.
Recovery Depth:1.50 m
Recovery Date: February 24,2021
Recovery Method: Method of
Test pit
Soil Description:
Measurement and Calculations:
Determination Number
Container and Wet Soil (g)
1
44.4
Liquid Limit
2
3
39.0
44.2
4
34.6
Plastic Limit
1
2
32.9
32.2
Container and Dry Soil (g)
37.8
33.7
34.2
30.2
30.4
Moisture Loss (g)
Mass of Container (g)
Mass of dry soil (g)
Moisture content (%)
Number of blows
6.6
21.0
16.8
39.3
35
5.3
21.0
12.7
41.7
27
6.0
20.9
13.3
45.1
19
4.4
21.1
9.1
48.4
15
2.5
2.4
21.0
21.0
9.4
8.8
26.6
27.3
Average = 27
Liquid Limit (LL)
Corresponding Plastic Limit (PL)
43
27
Plasticity Index (PI)
Group Index (GI)
Group Classification
16
11
A-7-6: Clayey Soil
29.8
The table shows the calculations and measurements made to determine
the liquid limit, plastic limit, and plasticity index of the soil sample.
The Liquid Limit test was done in four trials. Each trial has 35, 27, 19
and 15 number of blows respectively. The amount of moisture ranges
from 39.3-48.4 %. Meanwhile, the Plastic Limit test was done twice
averaging 27 number of blows. The first trial is determined to have a
26.6% of moisture content while the second trial have 27.3%.
The data acquired from the liquid limit test are plotted on a semilogarithmic graph paper as shown above in order to show the
relationship between moisture content and the corresponding number
of flows. The soil sample was then determined by determining first its
Liquid Limit which is 43% and Plastic Limit of 27%. The Plasticity
Index of 16 shows the difference of the Liquid Limit to the Plastic
Limit of the soil sample. Using the Unified Soil Classification System
(USCS), its Group Index is 11 and classified as A-7-6, Clayey Soil.
VII. CONCLUSION
Liquid limit of soil is a very important property of fine grained
soil and the value obtain is used to classify fine grained soil.
Liquid Limit gives us information regarding the state of
consistency of soil in a particular area or site. Plastic limit may
be defined as the moisture content where the thread of soil breaks
apart at a diameter of 3.2 mm. In this regard, the soil is considered
non-plastic if the soil thread cannot be rolled down to 3.2 mm at
any possible moisture conditions. There are still mistakes that
might influence the results of this experiment. If the quantity of
blows and their rate are not precisely followed, the outcome may
change substantially. The rolling of the soil sample and the
amount of water added to might have an impact on the results. In
regards to minimizing the error, a experts in this field would be a
great guidance to obtain an accurate data regarding on the soil
sample.
VIII. REFERENCES
 LIQUID LIMIT OF SOIL – WHAT, WHY & HOW? CivilBlog.Org
 ASTM D4318- Standard for Liquid Limit, Plastic limit and
Plasticity Index of soil
 ASTM, 100 Barr Harbor Drive, PO Box C700, West
Conshohocken, PA 19428-2959, United States.
 Plastic Limit Test Of Soil | Importance & Lab Procedure Of Plastic Limit Test
(dreamcivil.com)