The document reports on an experiment to determine the Atterberg limits of a soil sample composed of 70% bentonite and 30% kaolinite. The liquid limit was found to be 134% and plastic limit was 40%, giving a plasticity index of 94%. Various properties were calculated including flow index and toughness index. The results were compared to other bentonite-kaolinite mixtures, showing that liquid limit decreases with lower bentonite content. The liquid limit provides information about the soil's stress history and engineering properties.

1. 1
Department of Civil Engineering, IIT Delhi
Submitted By:
Abhinav Kumar
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Soil Engineering Lab
REPORT TITLE (04)
Atterberg Limits Test

2. 2
Objective: Determination of Liquid Limit and Plastic Limit of given soil sample.
Apparatus:
1. Mechanical Liquid Limit Device - conforming to
IS: 9259- 1979.
2. Grooving tool - conforming to IS: 9259-1979.
3. Porcelain Evaporating Dish - about 12 to 15 cm in
diameter.
4. Flat Glass Plate - 10 mm thick and about 45 cm
square or larger.
5. Spatula - flexible, with the blade about 8 cm long
and 2 cm wide (for mixing soil and water in the
porcelain evaporating dish).
6. Palette Knives - two, with the blade about 20 cm
long and 3 cm wide (for mixing soil and water on
the flat glass plate).
7. Balance- sensitive to 0.01 g.
8. Oven- thermostatically controlled with interior of non-corroding material to maintain the
temperature between 105 and 110°C.
9. Wash Bottle or Beaker- containing distilled water.
10. Containers - air-tight and non-corrodible for determination of moisture content.
11. Soil Sample - A sample weighing about 60 g was taken from the thoroughly mixed portion of
material (70% Bentonite: 30% Kaolinite) passing 425-micron IS Sieve [ IS: 460 (Part 1)-1978]
obtained in accordance with IS : 2720 (Part 1)-1983.
12. Surface for Rolling - ground-glass plate about 20 x 15 cm.
13. Rod - 3 mm in diameter and about 10 cm long.
Bentonite Kaolinite 70% Bentonite: 30% Kaolinite

3. 3
Testing methods and Procedures:
1. TEST FOR THE DETERMINATION OF LIQUID LIMIT (70% Bentonite : 30% Kaolinite)
(MECHANICAL METHOD)
Adjustment of the Mechanical Device:
The liquid limit device was inspected to determine that it is clean, dry and in good working order, that the
cup falls freely and it does not have too much side play at its hinge. The grooving tool was also inspected
to determine that it is clean and dry.
Using the gauge on the handle of the grooving tool or a separate
gauge and by means of the adjustment plate of the mechanical liquid limit device, the height through
which the cup is lifted and dropped shall be adjusted so that the point on the cup which comes in contact
with the base falls through exactly one cm for one revolution of the handle. The adjustment plate was
then secured by tightening the screw.
2. About 60 g of the proportioned soil sample passing 425-micron IS Sieve was mixed thoroughly with
distilled water in the evaporating dish to form a uniform paste. The paste shall have a consistency that will
require 30 to 35 drops of the cup to cause the required closure of the standard groove.
Divided Soil cake before test Soil cake after test
3. TEST FOR THE DETERMINATION OF PLASTIC LIMIT
Soil Sample - A sample weighing about 20 g from the thoroughly mixed portion of the material passing
425-micron IS Sieve, obtained in accordance with-IS: 2720 (Part 1)-1983 was taken. At a stage in the
process of mixing of soil and water at which the mass becomes plastic enough to be easily shaped into a
ball, a portion of the soil sample in the plastic state was taken for the plastic limit test.
The soil sample shall be mixed thoroughly with distilled water in an evaporating dish or on the flat glass
plate till the soil mass becomes plastic enough to be easily moulded with fingers.
The rolling shall be done till the threads are of 3 mm diameter. The soil shall then be kneaded together to
a uniform mass and rolled again. This process of alternate rolling and kneading shall be continued until
the thread crumbles under the pressure required for rolling and the soil can no longer be rolled into a
thread.

4. 4
Calculations:
• Liquid Limit (wl)= The moisture content corresponding to 25 drops as read from the curve was
rounded off to the nearest whole number and reported as the liquid limit of the soil.
• Plastic Limit (wp)= The average of the results calculated to the nearest whole number shall be
reported as the plastic limit of the soil.
• Plasticity Index (Ip)= Liquid Limit – Plastic Limit
• Flow Index (If) = (w1 – w2)/ log(N2/N1)
• Toughness Index (IT) = Ip/If
Data Table
Liquid Limit
Trial 1 2 3 4
Number of Blows (N) 32 26 20 15
Log (N) 1.51 1.4 1.3 1.18
Container No (3) (VI) (G2-4) (M1)
Wt. of Can +Wet Soil (g) 24.28 31.71 19.49 29.01
Wt. of Can + Dry Soil (g) 17.25 22.82 13.18 17.76
Wt. of Water (g) 7.03 8.89 6.31 11.25
Wt. of Can (g) 11.73 16.13 8.67 9.86
Wt. of Dry Soil (g) 5.52 6.69 4.51 7.9
Water Content (%) 127.3551 132.8849 139.9113 142.4051
Plastic Limit
Trial 1 2 3
Container No (14) (B-48) (32)
Wt. of Container (g) 12.79 12.75 12.64
Wt. of Can +Wet Soil (g) 15.1 13.92 14.01
Wt. of Can + Dry Soil (g) 14.43 13.57 13.63
Wt. of Water (g) 0.67 0.35 0.38
Wt. of Dry Soil (g) 1.64 0.82 0.99
Water Content (%) 40.8537 42.6829 38.3838
Average 40.64014

5. 5
Result:
1. Liquid Limit (wL) = 134 %
2. Plastic Limit (wP) = 40 %
3. Plasticity Index (Ip)= 94 %
4. Flow Index (If) = 58.75
5. Toughness Index (IT) = 1.6
Discussion:
1. The four combinations of Bentonite-Kaolinite mixture gave following trend. In general with
decrease in bentonite content and increase in kaolinite content, the Liquid Limit, Plastic Limit and
Plasticity Index starts decreasing.
Group Soil Type LL % PL % Plasticity Index % If IT
1 Bentonite 70% : Kaolinite 30% 134 40 94 58.75 1.6
2 Bentonite 100% 169 49 120 52.41 2.289
3 Bentonite 50%: Kaolinite 50% 105 33 72 12.76 5.64
4 Bentonite 30%: Kaolinite 30% 74 25 49 7.83 6.26
2. As demonstrated by the graph, 100% Bentonite has very high liquid limit. Though all are very high
plastic soil (Plasticity Index > 40%), but with decrease in Bentonite content Flow Index (If)
decreases as the slope of curve decreases. Thus, Toughness Index (IT) increases as the mixture
becomes less plastic which is also evident from the graph.
3. The cup was fitted and dropped by turning the crank at the rate of two revolutions per second
until the two halves of the soil cake come in contact with bottom of the groove along a distance of
about 12 mm.
125
127
129
131
133
135
137
139
141
143
145
5 50
Water
Content
(%)
Log (No of Blows N)
LIQUID LIMIT
25 Blows
Liquid Limit= 133.78%

6. 6
65
70
75
80
85
90
95
100
105
110
115
120
125
130
135
140
145
150
155
160
165
170
175
180
185
5 50
Water
Content
(%)
Log (No of Blows N)
LIQUID LIMIT
25 Blows
LL = 168.61%
LL = 133.78%
LL = 105.31%
LL = 74.21% Bentonite 30%: Kaolinite 70%
Bentonite 50%:Kaolinite 50%
Bentonite 70%:Kaolinite 30%
Bentonite 100%

7. 7
4. The liquid limit is the moisture content at which the groove, formed by a standard tool into the
sample of soil taken in the standard cup, closes for 12 mm on being given 25 blows in a standard
manner. This is the limiting moisture content at which the cohesive soil passes from plastic state
to liquid state.
5. Liquid limit is significant to know the stress history and general properties of the soil met with
construction. From the results of liquid limit the compression index may be estimated.
6. The compression index value will help us in settlement analysis.
7. If the natural moisture content of soil is closer to liquid limit, the soil can be considered as soft. If
the moisture content is lesser than liquid limit, the soil is brittle and stiffer.
References:
1. IS: 2720 (Part 5) – 1985
2. IS: 2720 (Part 2)-1973
3. IS: 2720 (Part 1)-1983
4. IS: 9259-1979
5. ASTM D 4318