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Experimental Investigation on Black Cotton Soil
Using Bio-Enzyme as a Soil Stabilizer in
Road Construction S.P.Kanniyappan
1, R.G.Dhilip Kumar
2, A.Faizuneesa
3, S.Saranya
4
1, 2, 3, 4 Assistant Professor, Department of Civil Engineering, R.M.K Engineering College, Kavaraipettai, Tamilnadu
1spk.civil@rmkec.ac.in
Abstract — Bio-enzyme is a natural, non-toxic, non-flammable, non-corrosive liquid enzyme formulation fermented from
vegetable extracts that improves the engineering qualities of soil, facilitates higher soil compaction densities and increases stability.
Enzymes catalyse the reactions between the clay and the organic cat-ions and accelerate the cat-ionic exchange process to reduce
adsorbed layer thickness. In this study, Black cotton soil with varying index properties have been tested for stabilization process and
strength of the stabilized soil were evaluated after the curing period of 7 days & 14 days for various enzyme dosages 200 ml/3m3,
200 ml/2.5m3, 200ml/2m3, 200ml/1.5m3. The tests which were carried out are the California Bearing Ratio (CBR) test and Unconfined
Compressive strength (UCS) test for the soil specimen. The test results indicates that bio-enzyme stabilization improves the strength
of Black Cotton soil up to great extent, which indicate the bearing capacity and the resistance to deformation increases in stabilized
soil. Adopting the IRC method, based on soil CBR, the pavement design thickness on stabilized soil also reduces 25 to 40%.
Keywords — Black Cotton Soil, Compressive Strength, California Bearing Ratio, Shear Strength, Terrazyme, Unconfined
Compressive Strength
I. INTRODUCTION
A. General
The process of improving the strength and durability of soil is known as soil stabilization. The main aim of stabilization is
cost reduction and to efficiently use the locally available material. Most common application of stabilization of soil is seen in
construction of roads and airfields pavement. Chemical stabilization is done by adding chemical additives to the soil that
physically combines with soil particles and alter the geotechnical properties of soil. Enzymes enhance the soil properties and
provide higher soil compaction and strength.
Terrazyme is non-toxic, non-corrosive and inflammable liquid which can be easily mixed with water at the optimum
moisture content and improves the properties of soil and strength of soil significantly. Life of a structure increases as CBR
value is increased and consistency limits are decreased. The chemical bonding of the soil particles is increased by the use of
Terrazyme and a permanent structure is formed which is resistant to wear and tear, weathering and infiltration of water in soil.
Apart from improving strength of soil, this bio enzyme replaces the need of granular base and sub base. Terrazyme dosage
entirely depends on the type of soil, clay content and plasticity index of soil. Different parameters were considered in the
present work to check the effects of Terrazyme on local soil. Sub-grade soil is an important material in highway construction.
In general practice locally available material is used as sub-grade soil. In some cases, the local material does not have sufficient
strength to bear the estimated loads. Such soils which do not possess sufficient strength can be stabilized using various
additives like lime, cement etc.
Soil improvement is a combination of physical and chemical methods for improving the characteristics of soil when it is
used as a construction material. Pozzolana material like fly ash can also be used as soil stabilizer. The materials like fly ash are
not easily available in every area. If fly ash is transported from distant places, transportation cost increases. An ideal soil
stabilizer should be easily available, economical and eco-friendly. Terrazyme is a good alternative to the conventional soil
stabilizers like fly ash, lime etc. Terrazyme is a bio-enzyme which is used as a soil stabilizer in construction of road
infrastructure. It is used to improve the soil properties. It is non-toxic and natural substance. It is formulated from plants,
vegetable extract and fruit extract. So it is also ecofriendly. In the present study, effect of addition of Terrazyme for improving
CBR value of soil is analyzed.
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B. Bio-Enzymatic Soil Stabilization
1) About Bio-enzyme
Bio-enzyme is a natural, non-toxic, non-flammable, non-corrosive liquid enzyme formulation fermented from
vegetable extracts that improves the engineering qualities of soil, facilitates higher soil compaction densities, and increases
stability. Enzymes catalyse the reactions between the clay and the organic cat-ions and accelerate the cat-ionic exchange
process to reduce adsorbed layer thickness. For other types of chemical stabilization, chemicals are mixed with soil, which is
difficult to mix thoroughly, but Bio-enzyme is easy to use as it can be mixed with water at optimum moisture content and then it
is sprayed over soil and compacted.
2) Mechanism of soil stabilization by bio-enzyme
In clay water mixture positively charged ions (cat-ions) are present around the clay particles, creating a film of water
around the clay particle that remains attached or adsorbed on the clay surface. The adsorbed water or double layer
gives clay particles their plasticity.
In some cases the clay can swell and the size of double layer increases, but it can be reduced by drying. Therefore to
truly improve the soil properties, it is necessary to permanently reduce the thickness of double layer.
In the present study, one type of bio-enzyme has been used for stabilization of five types of soil with varying index
properties. Detailed laboratory tests were carried out to ascertain the benefits in terms of reduction in design thickness.
Cat-ion exchange processes can accomplish this. By utilizing fermentation processes specific micro-organisms can
produce stabilizing enzyme in large quantity. These soil stabilizing enzymes catalyse the reactions between the clay
and the organic cat-ions and accelerate the cat-ionic exchange without becoming part of the end product.
3) Bio-enzyme as soil stabilizer in road construction
Cost effective roads are very vital for economic growth in any country. There is an urgent need to identify new
materials and to improve road construction techniques to expand the road network. Commonly used materials are fast depleting
and this has led to an increase in the cost of construction. Hence, the search for new materials and improved techniques to
process the local materials has received an increased impetus. When poor quality soil is available at the construction site, the
best option is to modify the properties of the soil so that it meets the pavement design requirements. This has led to the
development of soil stabilization techniques. Since the nature and properties of natural soil vary widely, a suitable stabilization
technique has to be adopted for a particular situation after considering the soil properties. Soil improvement by mechanical or
chemical means is widely adopted. In order to stabilize soils for improving strength and durability, a number of chemical
additives, both inorganic and organic, have also been used. Recently bio-enzymes have emerged as a new chemical for soil
stabilization. Bio- enzymes are chemical, organic, and liquid concentrated substances which are used to improve the stability of
soil sub-grade for pavement structures. Bio-Enzyme is convenient to use, safe, effective and dramatically improves road quality.
4) Enzyme stabilization effects
Organic cat-ions generated by the growth of vegetation and microorganisms also have the capability to exchange
position with other ions attracted to the clay platelet in the soil. In contrast with metal cat-ions, the organic cat-ions have large
flat structures that approach the size of small clay particles. These organic cat-ions can blanket the clay particle and effectively
neutralize its negative charge in a short distance, thus greatly reducing the double layer thickness. Certain soil microorganisms
make use of this chemistry to stabilize their environment. They produce specific enzymes that catalyse the reactions between
the clays and the organic cat-ions, producing clods of stable soil among the roots of the vegetation. These soil-stabilizing
enzymes accelerate the cationic exchange without becoming part of the end product.
By utilizing fermentation processes, specific microorganisms can produce stabilizing enzymes in large quantities. This
fermentation, formulated products are non-toxic and environmentally harmless. When exposed to the air, the microorganisms
multiply rapidly and produce large organic molecules, which the enzyme attaches to the clay platelets. The negative charges on
the clay platelets are neutralized through this process and the size of the electrical double layer shrinks. This limits further
adsorption of water or the resultant swelling with loss of density. The enzyme is regenerated by the reaction and goes on to
perform again. Reactions, which might otherwise take years to occur, can be carried out in weeks. While some soil strength
gain will become apparent within days, field research indicates that strength will continue to increase over a period of several
weeks. As the soil is exposed to air and the reaction proceeds, water, which was initially adsorbed on, the clay will be released
from the clay structure and can evaporate. As this occurs, clay particles are drawn closer together, soil density increases and the
load bearing structure strengthens.
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Terrazyme soil stabilization products are also designed to improve soil strength by increasing the density of initial
compaction and facilitating the removal of pore water, which minimizes the destructive impact of water under conditions of
loading. Combined with the impact of Terrazyme on the electrical double layer of clay particles, these factors can promote the
formation of a stabilized soil structure of superior density and load bearing strength even in soils lacking a significant plastic
fines fraction. Field results indicate that soil treated with Terrazyme can reach 95% Modified Proctor with significantly reduced
compaction effort.
Compacting of the soil at the optimum moisture content using proper construction methods and equipment is essential
to produce the high density necessary for enzymatic stabilization. The reduction in voids resulting from this realignment would
decrease pore water within the treated road layer and inhibit water penetration. This impact of the Terrazyme treatment Process
on the soil structure correlates with observed reductions in permeability. All of the factors discussed can combine to minimize
the destructive impact of soil water on the load bearing structure of the treated layer. Because the organic ions are very large,
little migration takes place within the pore water. Therefore, to achieve the desired results, intimate mixing is required to
distribute the enzyme solution throughout the soil. In addition, compaction of the soil at the optimum moisture content using
proper construction methods and equipment is essential to produce the high density necessary for enzymatic stabilization. Close
adherence to all aspects of the Terrazyme treatment process is important to soil stabilization success.
C. Scope of the Present Study
Enzymes catalyze the reactions between the clay and the organic cat-ions and accelerate the cationic exchange process to
reduce adsorbed layer thickness. For other types of chemical stabilization, chemicals are mixed with soil, which is difficult to
mix thoroughly, but bio-enzyme is easy to use as it can be mixed with water at optimum moisture content and then it is sprayed
over soil and compacted. In this study Black cotton soil with various qualities, index properties will be test for stabilization
process and strength of the stabilized soil will be evaluated after the curing period of 7 days &14 days for various enzyme
dosages of 1%, 2%, 3% and 4% of 200ml/3m3.
D. Objectives of the Present Study
To study the experimental output by doing stabilization tests.
To study the effect of Bio-enzyme on the quality of sub grade/base course layers and its influence on pavement system.
To optimize the quantity of Bio-enzyme to be used as stabilizing agent and the extent of stabilization of strength gain
with time.
II. METHODOLOGY, MATERIALS USED & ITS PROPERTIES
A. Methodology
The total study is carried out in two stages. In the first stage, the soil characterization is done. In the second stage,
Terrazyme is added to the soil in two dosages, 0.05% and 0.1% and studies are conducted. Tests are conducted with soil alone
as well as soil stabilized with terrazyme containing different dosages. The soil is oven dried and pulverized then mixed with the
desired amount of terrazyme. Water is added to the mixture and mixed until it becomes homogenous. The laboratory tests
carried out on the natural soil include particle size distribution as per IS: 1498-1970, Specific Gravity as per IS: 2720 Part III
section 1-1980, Atterbergs limits test as per IS: 2720-part V 1985, Compaction test as per IS: 2720 part VII-1980, Unconfined
compressive strength test as per IS: 2720-part X. CBR tests as per IS: 2720 part XVI. Unconfined compression tests are
conducted on soil and terrazyme mixes compacted at their respective Maximum Dry Density (MDD) and Optimum Moisture
Content (OMC).
B. Materials
1) Black cotton soil
Black Cotton Soil (BC Soil) is a highly clayey soil. The black colour in Black cotton soil is due to the presence of titanium
oxide in small concentration as shown in Fig 1. The Black Cotton Soil (BC Soil) has a high percentage of clay, which is
predominantly montmorillonite in structure and black or blackish grey in colour. Expansive soils are the soils which expand
when the moisture content of the soils is increased. The clay mineral montmorillonite is mainly responsible for expansive
characteristics of the soil. The expansive soils are also called swelling soils or black cotton soils.
2) Terrazyme
Bio-enzyme from Australia is a natural, nontoxic bio-degradable liquid concentrate as shown in Fig 2 that mixes easily in
water for application with standard water spraying equipment. Bio-Enzyme is a low cost additive with long lasting effects.
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By altering the physical and chemical characteristics of soil, materials treated with Bio-Enzyme retain higher performance
levels and extended life span. Bio-Enzyme may be used to increase the Maximum dry density and Unconfined Compressive
Strength (UCS) values of a marginal material to achieve specified standards for a base course.
Fig. 1 Black Cotton Soil Fig. 2 Terrazyme
C. Properties of Terrazyme
TABLE I PROPERTIES OF TERRAZYME
Colour Dark brown
PH 3.50
Evaporation Rate Same as water
Odour Smells like Molasses
Extracted from Molasses
Specific Gravity 1.414
III. EXPERIMENTAL INVESTIGATION & TEST RESULTS
A. California Bearing Ratio (CBR) Test
CBR is California Bearing Ratio, defined as the ratio of force per unit area required to penetrate a soil mass with standard
circular piston that requires for the corresponding penetration of standard material. This test is usually needed to determine the
sub-grade strength of the soil in pavements. With the addition of Terrazyme a significant increase in the values of both soaked
and unsoaked CBR samples is seen. This is because of the increased compaction which creates a stronger bond between the soil
particles, helping them to resist penetration more appreciably. Also with the increase in curing period of samples with
Terrazyme, it is seen that the CBR value increases, indicating more strength provided by the soil with time.
B. Unconfined Compressive Strength (UCS)Test
UCS is the maximum axial compressive stress of a right cylindrical sample of soil or any other material can withstand under
unconfined (confining stress is zero) conditions. UCS test basically gives the strength of the soil so to determine the effect of
Terrazyme it is necessary to know the changes on UCS. After performing various tests on different types of soils it is seen that
with the addition of Terrazyme there is an increase in the unconfined compressive strength of soil to a great extent. In some
cases, UCS has increased as much as 200% making the enzyme an ideal solution for soil stabilization.
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1) Experimental Results of Black Cotton Soil without Bio-Enzyme
a) California Bearing Ratio (CBR) Test Observations
TABLE II
CBR TEST WITHOUT BIO-ENZYME
Sl. No. Penetration (mm) Proving Ring Divisions Load (Kg)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
6.0
7.0
8.0
9.0
12
32
50
56
60
64
66
67
70
71
71
72
73
74
14.40
38.42
60.03
67.23
72.04
76.84
79.24
80.44
84.04
85.24
85.24
86.45
87.65
88.85
Calculation of CBR corresponding to 2.5mm & 5mm penetration using the relation,
CBR = (Test Load/Standard Load) ×100
Penetration (mm) Standard Load (Kg)
2.5 1370
5.0 2055
Fig. 3 Graph between Penetrations (mm) Vs. Load (Kg)
CBR @ 2.5mm = 5.25%
CBR @ 5.0mm = 4.14%
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b) Unconfined Compression Strength (UCS) Test Observations
TABLE III
UCS TEST WITHOUT BIO-ENZYME
Proving Ring Load = 0.2674
Initial Diameter of Mould = 3.4 Cm
Length of the Mould = 7.0 Cm
Compressive Strength (qu) = 0.94 kg/cm2
Shear Strength = qu/2 = 0.472 kg/cm2
Fig. 4 Graph between Strain and Stress (Kg/cm2)
c) Properties of Black Cotton Soil without Bio-Enzyme
TABLE IV
PROPERTIES OF BC SOIL
Sl. No. Property Result
1 Dry Density 1.46 g/cc
2 Optimum Moisture Content 30 %
3 Liquid Limit 76 %
4 Plastic Limit 43.62
5 CBR
Un Soaked
Soaked
5.25 %
0.74 %
6 Unconfined Compressive Strength 0.944 kg/cm2
7 Soil Classification CH (High Compressible Inorganic Clay)
Divisions (∆L)
mm
Proving
Divisions
Load Strain
e=∆L/L0
Area
A=A0/(1-e) cm2
Stress
P/A
Kg/cm2
50
100
150
200
250
300
350
400
450
500
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
16
21
24
26
28
30
31
34
34
34
4.28
5.61
6.42
6.95
7.49
8.02
8.29
9.09
9.09
9.09
0.007
0.014
0.021
0.028
0.036
0.042
0.050
0.057
0.064
0.071
9.144
9.209
9.274
9.341
9.419
9.478
9.558
9.628
9.700
9.773
0.468
0.609
0.692
0.744
0.795
0.846
0.867
0.944
0.937
0.930
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Terrazyme stabilization has shown little to very high improvement in physical properties of soils. This little
improvement may be due to chemical constituent of the soil, which has low reactivity with Bio-enzyme. Therefore, it is
advisable to first examine the effect of Bio-enzyme on soil stabilization in the laboratory before actual field trials. In some cases
where the soil is very weak like highly clay to moderate soil, like silty soil to sandy soil, the effect of stabilization has improved
the CBR and unconfined compression strength.
d) Dosage of Enzyme
The Terrazyme dosage for 200ml/3m3
soils varies for 1%, 2%, 3% and 4%. The Enzyme dosage is calculated as
follows:
Bulk Density of Black Cotton Soil = 1.46 g/cc
Bulk Density = Weight/Volume
Weight = Bulk Density ×Volume
= 1.46×3.0×1000
= 4380 Kg
Therefore, Consider 5Kg Soil Sample,
For 1% Terrazyme dosage = (1/5000) ×100 = 0.02 ml
2% Terrazyme dosage = (2/5000) ×100 = 0.04 ml
3% Terrazyme dosage = (3/5000) ×100 = 0.06 ml
4% Terrazyme dosage = (4/5000) ×100 = 0.08 ml
Dosage (%) Terrazyme (ml)
1
2
3
4
0.02
0.04
0.06
0.08
2) Experimental Results of Black Cotton Soil with Bio-Enzyme
To know the Strength and Durability of Black Cotton Soil with Bio-Enzyme, Unconfined Compression Strength (UCS)
Test and California Bearing Ratio (CBR) Test is conducted.
a) Unconfined Compressive Strength (UCS) Test Observation & Results
Unconfined Compression Test is conducted with various Terrazyme dosages of 1%, 2%, 3% and 4% with 7 days
and 14 days curing period.
The Unconfined Compression Test results is as follows for 7 days curing period with various dosages of Terrazyme,
Dimensions of the mould:
Length of the mould (L) = 7 cm
Diameter of the mould (D) = 3.4 cm
Area of the mould (Ao) = 9.08 cm2
For 1% Dosage 7 Days Curing:
Observations:
TABLE V UCS (1%) 7 DAYS
Divisions (∆L) mm Proving
Divisions Load
Strain
e=∆L/L0
Area
A=A0/(1-e) cm2
Stress
P/A Kg/cm2
50
100
150
200
250
0.5
1.0
1.5
2.0
2.5
70
134
149
168.5
143
18.72
35.83
39.84
45.06
38.24
0.007
0.014
0.021
0.029
0.035
9.144
9.209
9.274
9.341
9.419
2.047
3.890
4.295
4.824
4.059
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Fig. 5 UCS (1%) graph after 7 days curing
Result:
Compressive Strength (qu) = 4.824 kg/cm2
Shear Strength = qu/2 = 2.412 kg/cm2
Shear Strength is increased from 0.472 kg/cm2 to 2.412 kg/cm
2
For 2% Dosage 7 Days Curing:
Observations:
TABLE VI
UCS (2%) 7 DAYS
Divisions (∆L) mm Proving
Divisions Load
Strain
e=∆L/L0
Area
A=A0/(1-e) cm2
Stress
P/A Kg/cm2
50
100
150
200
250
0.5
1.0
1.5
2.0
2.5
68
116
146
174
174
18.18
31.02
39.04
46.52
46.52
0.007
0.014
0.021
0.029
0.035
9.144
9.209
9.274
9.341
9.419
1.988
3.368
4.234
4.980
4.941
Fig. 6 UCS (2%) graph after 7 days curing
Result:
Compressive Strength (qu) = 4.980 kg/cm2
Shear Strength = qu/2 = 2.490 kg/cm2
Shear Strength is increased from 0.472 kg/cm2 to 2.490 kg/cm
2
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For 3% Dosage 7 Days Curing:
Observations:
TABLE VII
UCS (3%) 7 DAYS
Divisions (∆L)
mm
Proving
Divisions Load
Strain
e=∆L/L0
Area
A=A0/(1-e) cm2
Stress
P/A
Kg/cm2
50
100
150
200
250
300
350
0.5
1.0
1.5
2.0
2.5
3.0
3.5
38
95
127
184
228
222
215.5
10.16
25.403
33.96
49.201
60.96
59.36
57.62
0.007
0.014
0.021
0.029
0.035
0.043
0.050
9.144
9.209
9.274
9.341
9.419
9.478
9.558
1.111
2.758
3.662
5.267
6.472
6.263
6.02
Fig. 7 UCS (3%) graph after 7 days curing
Result:
Compressive Strength (qu) = 6.263 kg/cm2
Shear Strength = qu/2 = 3.123 kg/cm2
Shear Strength is increased from 0.472 kg/cm2 to 3.123 kg/cm
2
For 4% Dosage 7 Days Curing:
Observations:
TABLE VIII UCS (4%) 7 DAYS
Divisions (∆L)
mm
Proving
Divisions Load
Strain
e=∆L/L0
Area
A=A0/(1-e) cm2
Stress
P/A
Kg/cm2
50
100
150
200
250
0.5
1.0
1.5
2.0
2.5
32
87
150
282
282
8.55
23.26
40.11
75.41
75.41
0.007
0.014
0.021
0.029
0.035
9.144
9.209
9.274
9.341
9.419
0.935
2.525
4.325
8.073
8.006
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Fig. 8 UCS (4%) graph after 7 days curing
Result:
Compressive Strength (qu) = 8.073 kg/cm2
Shear Strength = qu/2 = 4.036 kg/cm2
Shear Strength is increased from 0.472 kg/cm2 to 4.036 kg/cm
2
The Unconfined Compression Test results is as follows for 14 days curing period with various dosages of Terrazyme,
For 1% Dosage 14 Days Curing:
Observations:
TABLE IX UCS (1%) 14 DAYS
Divisions (∆L)
mm
Proving
Divisions Load
Strain
e=∆L/L0
Area
A=A0/(1-e) cm2
Stress
P/A
Kg/cm2
50
100
150
200
250
300
0.5
1.0
1.5
2.0
2.5
3.0
20
35.8
75.2
90.2
110.2
105.00
5.35
9.57
20.11
24.12
29.47
28.77
0.007
0.014
0.021
0.029
0.035
0.043
9.144
9.209
9.274
9.341
9.419
9.478
0.585
1.039
2.168
2.583
3.128
3.035
Fig. 9 UCS (1%) graph after 14 days curing
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Result:
Compressive Strength (qu) = 3.128 kg/cm2
Shear Strength = qu/2 = 1.564 kg/cm2
Shear Strength is increased from 0.472 kg/cm2 to 1.564 kg/cm
2
For 2% Dosage 14 Days Curing:
Observations:
TABLE X UCS (2%) 14 DAYS
Divisions (∆L)
mm
Proving
Divisions Load
Strain
e=∆L/L0
Area
A=A0/(1-e) cm2
Stress
P/A
Kg/cm2
50
100
150
200
250
300
0.5
1.0
1.5
2.0
2.5
3.0
52
76
126
190
244
240
13.904
20.322
33.692
50.806
65.245
64.176
0.007
0.014
0.021
0.029
0.035
0.043
9.144
9.209
9.274
9.341
9.419
9.478
1.520
2.206
3.633
5.439
6.927
6.771
Fig. 10 UCS (2%) graph after 14 days curing Result:
Compressive Strength (qu) = 6.927 kg/cm2
Shear Strength = qu/2 = 3.384 kg/cm2
Shear Strength is increased from 0.472 kg/cm2 to 3.384 kg/cm
2
For 3% Dosage 14 Days Curing:
Observations:
TABLE XI
UCS (3%) 14 DAYS
Divisions (∆L)
mm
Proving
Divisions Load
Strain
e=∆L/L0
Area
A=A0/(1-e) cm2
Stress
P/A
Kg/cm2
50
100
150
200
250
300
0.5
1.0
1.5
2.0
2.5
3.0
80
101
172
226
342
342
21.39
27.00
45.99
60.43
91.45
91.45
0.007
0.014
0.021
0.029
0.035
0.043
9.144
9.209
9.274
9.341
9.419
9.478
2.339
2.932
4.959
6.469
9.995
9.649
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Fig. 11 UCS (3%) graph after 14 days curing
Result:
Compressive Strength (qu) = 9.995 kg/cm2
Shear Strength = qu/2 = 4.998 kg/cm2
Shear Strength is increased from 0.472 kg/cm2 to 4.998 kg/cm
2
For 4% Dosage 14 Days Curing:
Observations:
TABLE XII
UCS (4%) 14 DAYS
Divisions (∆L)
mm
Proving
Divisions Load
Strain
e=∆L/L0
Area
A=A0/(1-e) cm2
Stress
P/A
Kg/cm2
50
100
150
200
250
300
350
400
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
98
144
226
294
382
450
496
492
26.205
38.506
60.434
78.616
102.147
120.330
132.630
131.561
0.007
0.014
0.021
0.029
0.035
0.043
0.050
0.058
9.144
9.209
9.274
9.341
9.419
9.478
9.558
9.628
2.866
4.181
6.516
8.416
10.845
12.695
13.876
13.66
Fig. 12 UCS (4%) graph after 14 days curing
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Result:
Compressive Strength (qu) = 13.876 kg/cm2
Shear Strength = qu/2 = 6.830 kg/cm2
Shear Strength is increased from 0.472 kg/cm2 to 6.830 kg/cm
2
b) California Bearing Ratio (CBR) Test Observation & Results
California Bearing Ratio Test is conducted with various Terrazyme dosages of 1%, 2%, 3% and 4% with a 7 days
curing period.
The California Bearing Ratio Test results is as follows for 7 days curing period with various dosages of Terrazyme,
For 1% Dosage 7 Days Curing:
Observations:
TABLE XIII CBR (1%) 7 DAYS
Sl. No. Penetration (mm) Proving Ring Divisions Load (Kg)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
6.0
7.0
8.0
25
53
74
88
106
119
130
137
146
152
156
158
160
160
30.02
63.67
88.85
105.66
127.27
142.88
156.09
164.49
175.30
182.51
187.31
189.71
192.11
192.11
CBR @ 2.5mm = (127.77/1370) × 100 = 9.28%
CBR @ 5.0mm = (182.51/2055) × 100 = 8.88%
Fig. 13 CBR (1%) graph after 7 days curing
Result:
CBR for 1% = 9.28%
Percentage of CBR value increased = ((9.28-5.25)/5.25)×100 = 76.76%
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For 2% Dosage 7 Days Curing:
Observations:
TABLE XIV
CBR (2%) 7 DAYS
Sl. No. Penetration (mm) Proving Ring Divisions Load (Kg)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
6.0
7.0
8.0
17
30
52
76
112
120
133
148
160
163
168
172
179
184
20.411
36.021
62.436
91.253
134.478
144.089
159.693
177.704
192.112
195.714
201.717
206.520
214.925
220.928
CBR @ 2.5mm = (134.478/1370) × 100 = 9.81%
CBR @ 5.0mm = (195.714/2055) × 100 = 9.53%
Fig. 14 CBR (2%) graph after 7 days curing
Result:
CBR for 2% = 9.81%
Percentage of CBR value increased = ((9.8-5.25)/5.25)×100 = 86.87%
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For 3% Dosage 7 Days Curing:
Observations:
TABLE XV
CBR (3%) 7 DAYS
Sl. No. Penetration (mm) Proving Ring Divisions Load (Kg)
1
2
3
4
5
6
7
8
9
10
11
12
13
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
6.0
7.0
32
65
8
124
131
137
142
146
148
160
179
196
196
38.422
78.045
105.661
148.886
157.291
164.495
170.499
175.302
177.704
192.112
214.925
235.337
235.337
CBR @ 2.5mm = (157.291/1370) × 100 = 11.44%
CBR @ 5.0mm = (177.704/2055) × 100 = 9.35%
Fig. 15 CBR (3%) graph after 7 days curing
Result:
CBR for 3% = 11.44%
Percentage of CBR value increased = ((11.44-5.25)/5.25)×100 = 118.00%
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For 4% Dosage 7 Days Curing:
Observations:
TABLE XVI
CBR (4%) 7 DAYS
Sl. No. Penetration (mm) Proving Ring Divisions Load (Kg)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
6.0
7.0
8.0
43
81
127
166
198
230
255
272
284
293
317
317
324
337
51.630
97.267
152.485
199.316
237.738
276.161
306.178
326.590
340.998
351.805
380.621
380.621
389.026
404.635
CBR @ 2.5mm = (237.738/1370) × 100 = 17.35%
CBR @ 5.0mm = (351.805/2055) × 100 = 17.11%
Fig. 16 CBR (4%) graph after 7 days curing
Result:
CBR for 4% = 17.35%
Percentage of CBR value increased = ((17.35-5.25)/5.25)×100 = 230.47%
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c) Consolidated Test Results
1) Unconfined Compression Strength (UCS) Test Results TABLE XVII
UCS TEST RESULTS
Dosage of
Terrazyme (%)
UCS Value
7 Days
UCS Value
14 Days
1
2
3
4
2.412
2.490
3.123
4.036
1.564
3.384
4.998
6.830
2) California Bearing Ratio (CBR) Test Results TABLE XVIII
CBR Test Results
Dosage of
Terrazyme (%)
CBR Value
(7 Days) % Increased
1
2
3
4
9.28
9.81
11.44
17.35
76.76
86.87
118.00
230.47
IV. CONCLUSIONS
The addition of Terrazyme increases the CBR Value and UCS Value of the Black Cotton Soil consistently when there
is an increase in the dosage of the Terrazyme and it is being cured for several days and also the cost of the pavement is reduced
by using Terrazyme as an admixture. The pavement construction value is reduced by 30% of the total cost with the help of this
Bio-Enzyme. As a result of soil stabilization, the bearing capacity of the foundation of the structure is increased and its strength,
water tightness, resistance to washout, and other properties are improved. Soil stabilization is widely used in the construction on
sagging soils of industrial and civil buildings.
Terrazyme stabilization has shown little to very high improvement in physical properties of soils. This little
improvement may be due to chemical constituent of the soil, which has low reactivity with Bio-enzyme. Therefore, it is
advisable to first examine the effect of Bio-enzyme on soil stabilization in the laboratory before actual field trials. In some cases
where the soil is very weak like highly clay to moderate soil, like silty soil to sandy soil, the effect of stabilization has improved
the CBR and unconfined compression strength.
Pavement design thickness also reduces to 25 to 40 percent. Moreover, in case of scarcity of granular material, only
stabilized surface with thin bituminous surfacing can fulfil the pavement design requirement with more than 10 percent saving
in cost component.
REFERENCES
[1] Rajoria, Vijay and Suneet Kaur, “A Review on Stabilization of Soil Using Bio-Enzyme", International Journal of Research in Engineering and Technology, 1999.
[2] Isaac, P.Kuncheria, P.B.Biju and A.Veeraragavan, "Soil Stabilization using Bio-enzymes for Rural Roads", Seminar on Integrated Development of Rural
and Arterial Road Network for Socio-Economic Growth, New Delhi, Vol. 2 - 2003. [3] Marasteanu and O.Mihai, "Preliminary laboratory investigation of enzyme solutions as a soil stabilizer", 2005.
[4] Naagesh, Sureka and S.Gangadhara, "Swelling properties of bio-enzyme treated expansive soil", International Journal of Engineering Studies, P.No.155-
159, 2010. [5] C.Venkatasubramanian and G.Dhinakaran, "Effect of Bio-Enzymatic Soil Stabilization on and Applied Sciences”, P.No.295-298, 2011.
[6] Agarwal, Puneet, and Suneet Kaur, "Effect of Bio-Enzyme Stabilization on Unconfined Compressive Strength of Expansive Soil", International Journal of
Research in Engineering and Technology, 2014. [7] S.M.Lim, D.C.Wijeyesekera, A.J.M.S.Lim and I.B.H.Bakar, “Critical Review of Innovative Soil Road Stabilization Techniques”, International Journal of
Engineering and Advanced Technology, June 2014.
[8] Purnima Bajpai, “Non - Conventional soil stabilization techniques the way forward to an aggregate free pavement and a cost effective method of road construction”, International Journal of Scientific & Engineering Research, June 2014.
[9] Kavish S.Mehta, Rutvij J.Sonecha, Parth D.Daxini, Parth B.Ratanpara, Kapilani S.Gaikwad, “Analysis of Engineering Properties of Black Cotton Soil &
Stabilization Using By Lime”, International Journal of Engineering Research and Applications, May 2014. [10] Saini, Venika and Priyanka Vaishnava, "Soil Stabilization by using Terrazyme", International Journal of Advances in Engineering & Technology 2015.
[11] Joydeep Sen and Jitendra Prasad Singh, “Stabilization of black cotton soil using bio enzyme for a highway material”, International Journal of Innovative
Research in Science, Engineering and Technology 2015. [12] Swathy M Muraleedharan and Niranjana K, “Stabilization of Weak Soil using Bio-Enzyme”, International Journal of Advanced Research Trends in
Engineering and Technology, March 2015.
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