effect of drying on the strength properties …igs/ldh/files/igc 2015 pune/theme 2 challenges... ·...

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50th INDIAN GEOTECHNICAL CONFERENCE

17th – 19th DECEMBER 2015, Pune, Maharashtra, India

Venue: College of Engineering (Estd. 1854), Pune, India

EFFECT OF DRYING ON THE STRENGTH PROPERTIES OF TERRAZYME

TREATED EXPANSIVE AND NON-EXPANSIVE SOILS

H.N. Ramesh1, Sagar S.R.2

ABSTRACT

TerraZyme is a natural, non-toxic, non-flammable, non-corrosive liquid enzyme formulation fermented

from vegetable extracts that improves the engineering properties of soil; facilitate better workability of

soil and increases stability by catalyzing the reactions between the clay and the organic cations and

accelerate the cationic exchange process to reduce adsorbed layer thickness.

In the present study the effect of curing on the strength properties of TerraZyme treated black cotton soil

and red earth have been studied for the curing periods from 7days to 60days. The effect of curing on the

index properties and compressibility is also studied for validation of the study. Tests were carried out to

determine the Unconfined compressive strength, CBR, Consistency limits, Compressibility and Swelling

behaviour of the soil specimens with and without stabilization subjecting to air dry curing and desiccator

curing. Air-dry curing simulating on-field conditions has shown enormous increment in strength of

TerraZyme treated expansive and non-expansive soils as UCS and CBR compared to laboratory

conditions of desiccator curing. Though TerraZyme is successful in improving the index properties of

expansive and non-expansive soils air-dry curing and desiccator curing has same effect on the treatment.

Even in case of Compressibility and Swelling behaviour, air-dry curing has proved the best than the

desiccator curing. The test results indicate that air-dry curing is best suited for TerraZyme stabilization of

expansive and non-expansive soils. An attempt has been made to study the properties of soil modified

with TerraZyme subjected to air-dry curing and desiccator curing, in order to use this technology for low

cost soil stabilization techniques.

Keywords: TerraZyme (TZ), Consistency limits, Unconfined compressive strength (UCS), California

Bearing Ratio (CBR), Black cotton soil (BCS), Red earth (RE).

1Dr_ Ramesh H.N., Professor, University Visvesvaraya College of Engineering, Bangalore, India, [email protected]

2Mr_ Sagar S.R., Assistant Professor, RK University, (former PG student, UVCE), Rajkot, India, [email protected]

H.N. Ramesh & Sagar S.R.

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EFFECT OF DRYING ON THE STRENGTH PROPERTIES OF TERRAZYME

TREATED EXPANSIVE AND NON-EXPANSIVE SOILS

H.N. Ramesh, Professor, University Visvesvaraya College of Engineering, [email protected]

Sagar S.R., Assistant Professor, RK University, (former PG student, UVCE), [email protected]

ABSTRACT: Research on soil stabilization by enzymes though started more than two decades ago, very little

research has been done on simulating field conditions for the laboratory studies on behaviour of enzyme treated

soils. In the present study, an attempt has been made to study the effect of drying on the strength and other

properties of expansive and non-expansive soils stabilized by TerraZyme through laboratory studies on strength,

consistency limits, compressibility and free-swell index of the soils subjected to air-dry curing and desiccator

curing. Air-dry curing simulating on-field conditions has shown enormous increment in strength of TerraZyme

treated expansive and non-expansive soils as UCS and CBR compared to laboratory conditions of desiccator

curing. Though TerraZyme is successful in improving the index properties of expansive and non-expansive soils

air-dry curing and desiccator curing has same effect on the treatment. Even in case of Compressibility and Swelling

behaviour, air-dry curing has better results than the desiccator curing. The test results indicate that air-dry curing is

best suited for TerraZyme stabilization of expansive and non-expansive soils.

INTRODUCTION

The growing metropolitan cities needs more and

number of good lands for both construction

activities and road development. This is the major

limitation for the construction industry since most

of the good lands have already been built upon.

Most of the Central part of India is covered with

expansive black cotton soil and red earth appears in

patches throughout the nation. Black cotton soil

poses serious construction problems both to

structures and highways whereas red earth is good

for construction activities. Expansive soils show

swell-shrink behaviour with the variation in

moisture content whereas variation in moisture has

little effect on the properties of Red earth soil.

Soil stabilization is a very useful technique for

major civil engineering works. To utilize the full

advantage of the technique, quality control must be

adequate. Soil stabilization is the alteration of one

or more soil properties by mechanical or chemical

means, to create an improved soil material

possessing the desired engineering properties. Soils

may be stabilized to prevent erosion and dust

generation. Regardless of the purpose for

stabilization, the desired result is the creation of a

soil material or soil system that will remain in

place under the desired conditions for the design

life of the project. Engineers are responsible for the

selecting or specifying the correct stabilizing

method, technique, and quantity of material

required.

Extensive research has been carried out to evaluate

the effects of stabilizers such as cement, lime,

chemical admixtures on improving the strength and

reduce the settlement and swell-shrink nature of

soils. Not much research has been carried out on

utilizing bio-enzymes for stabilizing soils.

Microbial geo-technology is an emerging branch of

geotechnical engineering that deals with the

application of microbiological methods to improve

the mechanical properties of soil to make it more

fitting or appropriate for construction and

environmental purposes. In this regard two

noteworthy applications, bio-clogging and bio-

cementation have been explored. Bio-clogging is

the production of pore-filling materials through

microbial means so that the porosity and hydraulic

conductivity of soil can be reduced whereas bio-

cementation is the generation of particle binding

materials through microbial processes in situ so

that the shear strength of soil can be increased

[Ivanov & Chu 2008].


Most clay has a molecular structure with a net

negative charge. To maintain the electrical

neutrality, cations (positively charged) are attracted

to and held on the edges and surfaces of clay

particles. These cations are called exchangeable

cations because in most cases cations of one type

may be exchanged with cations of another type.

When the cation charge in the clay structure is

weak, the remaining negative charge attracts

polarized water molecules, filling the spaces of the

clays structure with ionized water. As a

consequence a movement of moisture from areas

of low cation concentration to areas of high cation

concentration is produced to achieve the

equilibrium of the cation concentration. Cations are

unable to disperse freely in the soil structure

because of the attractions of the negatively charged

surface of the clay particles. This creates an

osmotic pressure gradient, which tries to equalize

the cation concentration. As a consequence a

movement of moisture from areas of low cation

concentration to areas of high cation concentration

is produced to achieve the equilibrium of the cation

concentration [Scholen 1992].

The flow of cations through the clay deposits gives

the shrinking and swelling properties of the soils;

when a stabilizer solution is added in to the soil,

the magnitude of the effect depends on the

characteristics of the particular cation. In general

there are two main characteristics, the valence of

the cation or number of positive charges and the

size of the cation [Rauch et al. 2002].

The size determines the mobility of the cation;

smaller ones will travel a greater distance

throughout the soil structure (the hydrogen ion is

the smallest one). With respect to the valence, the

hydrogen ion is doubly effective affecting the clay

structure because even though it has only a single

charge, the hydrogen ion produces an effect of

valence of two due to its high ionization energy.

These hydrogen cations exert a stronger pull on the

clay layers pulling the structure of the soil together

and removing the trapped moisture permitted by

the single sodium and potassium cations. The loss

of moisture results in a strengthening of the

molecular structure of the clay [Scholen 1992].

Enzymes speed up a chemical reaction, that

otherwise would happen at a slower rate, without

becoming a part of the end product. The enzyme

combines with the large organic molecules to form

a reactant intermediary, which exchange ions with

the clay structure, breaking down the lattice and

causing the cover-up effect, which prevents further

absorption of water and the loss of density. The

enzyme is regenerated by the reaction and goes to

react again. The enzymes are absorbed by the clay

lattice, and then released upon exchange with

metals cations. They have an important effect on

the clay lattice, initially causing them to expand

and then to tighten. The enzymes can be absorbed

also by colloids enabling them to be transported

through the soil electrolyte media. The enzymes

also help the soil bacteria to release hydrogen ions,

resulting in pH gradients at the surfaces of the clay

particles, which assist in breaking up the structure

of the clay [Scholen 1992].

Lacuoture and Gonzalez (1995) conducted a

comprehensive study of TerraZyme soil stabilizer

product and its effectiveness on sub-base and sub-

grade soils. The variation in properties was

observed over a short period only and it was found

that in cohesive soils there was no major variation

in properties during the early days but the soil

showed improved performance progressively.

Bergmann (2000) studied the effect of bio-enzyme

on soils with different amount of clay content.

Bergmann conducted field study on the effects of

seven different soil stabilizers in The Wood River

accessible fishing site and day use area on the

Winema National Forest. The temperature varied

from -9oC to 38oC with climatic conditions.

Among the other stabilizers, enzyme stabilized

section showed significant improvement in soil

strength and its surface finish was retained for

long. Hitam and Yusof (1998) of Palm Oil

Research Institute of Malaysia conducted field

studies on improvement of plantation roads.

TerraZyme was treated to 27.2 km of the road,

which was having serious problems during the

monsoon season or after heavy downpour. The

sections were then monitored on the surface

erosion due to rainwater and wear due to usage.

After two monsoon seasons the road was found to

be in very good condition in spite of large exposure

to heavy rainfall. No surface damage was

observed, thus requiring no repair works to the

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road section. TerraZyme stabilization can convert

the road to an all-weather road that has minimum

destruction in hot and wet seasons. Isaac et al

(2003) conducted a comprehensive study of the

TerraZyme and its effectiveness on lateritic soil

and clay type soil collected from Kerala. The

reactions of the soils treated with the enzyme was

observed and recorded and compared to the

untreated samples for the period of 8 weeks. It was

found that in all soil types considered, the CBR

value has increased by addition of TerraZyme,

which proved its suitability as a stabilizing agent.

The increase in CBR was in the range of 136 to

1800 percent that of the original value. TerraZyme

is useful for clay soil and sand but is less

significant to silty soils; clayey and sandy soils had

increase in CBR by 700 percent. Manoj et al

(2003) conducted a study to assess the suitability of

Bio-Enzyme as soil stabilizer on five types of soils

with low clay content to very high clay content.

Laboratory tests were conducted to determine the

engineering properties of soil and strength

characteristics of soil with and without stabilization

with Bio-Enzyme. The Bio-Enzyme stabilization

has shown little to very high improvement in

physical properties of soil. This little improvement

may be due to chemical and constituent of the soil,

which has low reactivity with Bio-Enzyme. In the

cases of highly clay moderate soil, like silty soil to

sandy soil, the effect of stabilization has improved

the CBR and unconfined compressive strength.

Ravi Shankar et al (2009) studied the effect of

enzyme on lateritic soil and blended lateritic soil in

terms of unconfined compressive strength, CBR,

compaction and permeability. Their study found

that Bio-Enzyme stabilization showed medium

improvement in physical properties of lateritic soil.

Enzyme was found to be ineffective for improving

the consistency limits of lateritic soil. CBR value

showed 300% increment while unconfined

compressive strength increased by 450% and

permeability decreases by 42%. Marasteanu et al

(2005) conducted resilient modulus and tri-axial

tests on two soils which were stabilized with two

different enzymes. They studied enzymatic action

of both enzymes by conducting enzyme activity

tests and surface tension test was conducted to

study surfactant characteristics. They found that

bio-enzymes stabilize the soil both by catalysing

the reactions through enzymatic action and other

mechanism such as surfactant like characteristics.

They found that the enzyme was effective in

reducing the surface tension of water than a

common surfactant. Rauch et al (2003) measured

the effects of ionic stabilizer, enzyme stabilizer and

polymer stabilizer on five different soils. Two soils

were natural clays of high plasticity and three were

composed of predominantly one clay mineral. The

treated and untreated clay minerals were

characterized using BET surface area analysis,

cation exchange capacity, environmental scanning

electron microscopy and X-ray diffraction. They

found a significant reduction in surface area for all

the clay minerals and soil tested. They concluded

that the enzyme stabilizer caused a substantial

amount of agglomeration of the soil particles

regardless of the nature of the soil material. Peng et

al (2011) compared the effects of Perma-zyme and

quicklime on three soils. The samples were cured

up-to 60 days in two different conditions; air-dry

and in sealed container. They observed that the

enzyme was more effective in air-dry curing for

fine grained and silty soils than quicklime whereas

it was not effective for coarse grained soil in air-

dry curing and for three soils in sealed curing too.

Sureka et al (2010) conducted oedometer

consolidation tests on expansive soil on both

untreated and bioenzyme treated soil specimens.

The dosage of bioenzyme was varied from 0.25%

to 2%. The swelling potential and swelling

pressure were measured in the one dimensional

consolidation load cell using swell and load

procedure, scanning electron microscope studies

and cation exchange capacity tests were conducted

to observe the structural and CEC modifications.

They observed that bioenzyme treated expansive

soil exhibit lesser percent of swell and swell

pressures. Curing period beyond 30days did not

yield any further significant reduction in swell

properties. The structure of the soil changed from

flocculated to dispersed structure. No significant


changes were observed in cation exchange capacity

values of bio-enzyme treated soil specimen.

MATERIALS USED AND TESTS

CONDUCTED

The materials used for the tests include black

cotton soil (BCS), red earth (RE) and TerraZyme

(TZ) (Bio-Enzyme).

Table 1 Properties of Black Cotton Soil and Red

Earth

Properties Black

Cotton

Soil

Red

Earth

Colour Black

Brick

Red

Specific Gravity 2.62 2.59

Grain Size Distribution

Fine Sand Fraction (%)

Silt Size (%)

Clay Size (%)

14.8

63.6

21.6

36.0

45.76

18.24

Atterberg’s Limit

Liquid Limit (%)

Plastic Limit (%)

Plasticity Index (%)

Shrinkage Limit (%)

76

32

44

8

39

22

17

18

IS Soil Classification CH CI

Compaction

Characteristics

Maximum Dry Density

(kN/m3)

Optimum Moisture

Content (%)

13.5

30

17.22

18

Unconfined

Compressive Strength

(kPa)

147 414

California Bearing

Ratio (unsoaked) (%) 3 7

Black cotton soil was obtained from Haveri district

while red earth was obtained from Bangalore

University campus. Both the soils obtained from

the field were tested in the laboratory for the basic

index and engineering properties.

Table 2 TerraZyme Dosages

Dosage 200ml/m3 of Soil

BCS RE

1 3.0 4.0

2 2.5 3.5

3 2.0 3.0

4 1.5 2.5

The basic properties of these soils are tabulated in

Table 1. TerraZyme was obtained from Nature Plus

Inc., USA through Avijeet Agencies in Chennai.

Both the soils were treated using different dosages

of TerraZyme. Table 2 gives the details of Dosages

of TerraZyme used to treat BCS and RE.

TerraZyme treated soils were tested to evaluate the

effect of TerraZyme on the consistency limits,

compaction characteristics, unconfined

compressive strength, CBR of expansive and non-

expansive soils and swelling and compressibility

behaviour of expansive soils. All the tests were

performed as per IS specifications.

RESULTS AND DISCUSSIONS

This section summarizes the experimental results

of the Atterberg limits tests, compaction tests,

unconfined compressive strength tests which are

used as defining parameters for the optimization of

the dosage of TerraZyme required to treat the soils.

The CBR tests, oedometer tests, differential free

swell tests were conducted for the soils treated with

optimized dosage of TerraZyme.

Atterberg Limits

Black cotton soil and red earth treated with

TerraZyme were cured in both desiccator curing

and air-dry curing. Later the specimens were

subjected to Atterberg limits tests based on the

curing period. The results of the Atterberg Limits

tests have been given in table 3 and table 4

respectively. In Table 3 it can be inferred that for

black cotton soil, the liquid limit initially increased

for 7 days of curing and later on decreased with

further curing.

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Table 3 Results of Atterberg Limits Tests of Black Cotton Soil treated with TerraZyme

Combination Liquid Limit

(%)

Plastic Limit

(%)

Shrinkage Limit

(%)

Curing Period in days 0 7 30 0 7 30 0 7 30

BCS Alone 76 - - 32 - - 9 - -

Desiccator

Cured

BCS+TZ d1 76 78 70 32 29 25 9 10 11

BCS+TZ d2 76 78 68 32 29 24 9 10 12

BCS+TZ d3 76 77 65 32 28 23 9 10 12

BCS+TZ d4 76 77 67 32 28 23 9 10 12

Air-Dry

Cured

BCS+TZ d1 76 78 70 32 29 25 9 10 11

BCS+TZ d2 76 78 68 32 29 24 9 10 12

BCS+TZ d3 76 77 65 32 28 23 9 10 12

BCS+TZ d4 76 77 67 32 28 23 9 10 12

Table 4 Results of Atterberg Limits Tests of Red Earth treated with TerraZyme

Combination Liquid Limit

(%)

Plastic Limit

(%)

Shrinkage Limit

(%)

Curing Period in days 0 7 30 0 7 30 0 7 30

RE Alone 39 - - 22 - - 18 - -

Desiccator

Cured

RE+TZ d1 39 41 37 22 21 20 18 17 16

RE+TZ d2 39 42 36 22 21 20 18 17 15

RE+TZ d3 39 43 36 22 20 19 18 16 14

RE+TZ d4 39 44 35 22 20 19 18 16 14

Air-Dry

Cured

RE+TZ d1 39 42 37 22 21 20 18 17 16

RE+TZ d2 39 42 36 22 21 19 18 17 15

RE+TZ d3 39 43 36 22 21 19 18 16 15

RE+TZ d4 39 43 35 22 20 18 18 16 14

But the plastic limit has shown continuous

decrement with curing while the shrinkage limit

has shown some increment though not so

significant. Similar behaviour for liquid limit and

plastic limit of red earth can be seen from Table

4. But the shrinkage limit of red earth has

decreased by a small amount. While conducting

the Atterberg limits tests for black cotton soil

and red earth after 30days of curing, the soils

cured under air-dry curing condition exhibited

hydrophobic nature. While mixing the soils with

water for the tests, the soils were relatively

difficult to break and mix with water. It took

more time and energy to re-pulverize and mix

the soil and water to bring it to a proper

consistency for the tests.

The results of Atterberg limits tests exhibited no

distinct effect of air-dry curing when compared

with that of the desiccator cured samples.

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Compaction Characteristics

Standard proctor test was conducted on untreated

and TerraZyme treated black cotton soil and red

earth. Compaction test was conducted

immediately after mixing the TerraZyme in the

soils.

Fig. 1 Compaction characteristics of Black

Cotton Soil treated with TerraZyme

Both the soils were not allowed to cure to

simulate the field compaction conditions where

compaction is done immediately after

moisturizing the soil to optimum condition. Fig.

1 and Fig. 2 presents the compaction curves for

untreated and treated black cotton soil and red

earth.

Fig. 2 Compaction Characteristics of Red Earth

treated with TerraZyme

TerraZyme had little to no effect on the

compaction characteristics of both black cotton

soil and red earth when tested immediately after

mixing.This is because; TerraZyme requires

some amount of time to start acting on the soil

particles.

In the case of compaction, the soils were not

subjected to curing so as to simulate the field

compaction conditions.

Table 5 Unconfined Compressive Strength of Black Cotton Soil treated with TerraZyme

Combination Unconfined Compressive Strength (kPa)

Curing Period in days 0 7 15 30 45 60

BCS Alone 147 - - - - -

Desiccator

Cured

BCS+TZ d1 163 180 240 283 418 445

BCS+TZ d2 166 244 305 347 437 457

BCS+TZ d3 174 268 340 368 471 488

BCS+TZ d4 177 291 349 400 486 507

Air-Dry

Cured

BCS+TZ d1 163 337 442 627 1170 1351

BCS+TZ d2 166 375 532 944 1206 1388

BCS+TZ d3 174 397 607 1044 1248 1481

BCS+TZ d4 177 478 838 1147 1385 1533

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Table 6 Unconfined Compressive Strength of Red Earth treated with TerraZyme

Combination Unconfined Compressive Strength (kPa)

Curing Period in days 0 7 15 30 45 60

RE Alone 414 - - - - -

Desiccator

Cured

RE+TZ d1 446 505 554 628 775 944

RE+TZ d2 461 519 588 659 841 957

RE+TZ d3 464 549 638 740 998 1066

RE+TZ d4 466 554 642 748 1006 1072

Air-Dry

Cured

RE+TZ d1 446 648 2479 2964 3488 3668

RE+TZ d2 461 941 2590 3311 3616 3748

RE+TZ d3 464 1112 2891 3655 3744 3829

RE+TZ d4 466 1123 2908 3671 3757 3841

Unconfined Compressive Strength Tests

Unconfined compressive strength of black cotton

soil and red earth was evaluated by stabilization

with variable dosages of TerraZyme and

subjected to desiccator and air-dry curing

conditions up to 60 days of curing. Table 5

presents the unconfined compressive strength for

treated black cotton soil and Table 6 for red

earth. The unconfined compressive strength of

TerraZyme treated black cotton soil and red

earth has shown tremendous improvement. With

increase in curing periods, UCS has increased

and also with increase in dosage amount.

Table 5 and Table 6 clearly show the effect of

Air-dry curing on the treatment of the soils with

TerraZyme. Air-dry curing enhances the rate of

evaporation of water in the soil. So, as the

diffused double layer (DDL) is reduced by the

TerraZyme, the water from DDL enters the pore

spaces in the soil and this water is removed

quickly during air-dry curing. Thus it keeps the

soil dry and enhances the bond development

process resulting in the tremendous increment in

UCS of both the soils for air-dry curing

compared to desiccator curing.

Both soils showed good results for dosages 3 and

4, but dosage 3 can be taken as optimum as the

rate of improvement is better in dosage 3 than in

dosage 4. Hence for unsoaked CBR, Free swell

index and Compressibility, dosage 3 will be

taken as the optimum value.

Unsoaked CBR Tests

Black cotton soil and red earth were treated with

dosage 3 of TerraZyme and subjected to curing

up to 30 days. Dosage 3 has been considered as

the optimum dosage of TerraZyme for both the

soils based on Index properties tests and UCS

tests. The treated specimens were tested in

unsoaked condition. The test results are

presented in Table 7 and Table 8 for black cotton

soil and red earth respectively.

Table 7 Unsoaked CBR of Black cotton soil

treated with TerraZyme

Combination CBR (%)

Curing Period in days 0 7 30

BCS Alone 3 - -

Desiccator

Cured

BCS+TZ

d3 3 5 11

Air-Dry

Cured

BCS+TZ

d3 3 6 15

Table 8 Unsoaked CBR of Red earth treated

with TerraZyme

Combination CBR (%)

Curing Period in days 0 7 30

RE Alone 7 - -

Desiccator

Cured RE+TZ d3 7 9 22

Air-Dry

Cured RE+TZ d3 7 12 32


A tremendous increment in unsoaked CBR has

been observed in the TerraZyme treated black

cotton soil and red earth.

Even in the case of CBR, air-dry curing has

proved the best method of curing than the

desiccator curing for treating the expansive and

non-expansive soils using TerraZyme.

Compressibility Behaviour

Compressibility behaviour of expansive black

cotton soil treated with optimum dosage of

TerraZyme and cured for 30 days has been

studied and presented in this section. Figure 3

presents the pressure void ratio relation of the

untreated and treated black cotton soil.

Figure 3 e-log p curve of BCS treated with TZ

Table 9 Compression Index of BCS

Combination

Compression Index (Cc)

Cc=0.007(LL-

10)

From Slope

of Curve

BCS Alone 0.462 0.473

BCS + TZ d3

DC 0.385 0.383

BCS + TZ d3

ADC 0.385 0.38

TerraZyme treated black cotton soil is more

stable in air-dry cured condition than the

desiccator cured sample and the untreated soil as

seen from figure 3. Desiccator cured soil had

lesser void ratio than the air-dry cured soil but

the structure of air-dry cured soil was more

stable.

Table 9 presents the compression index values of

untreated and TerraZyme treated black cotton

soil. The compression index of black cotton soil

has decreased considerably upon treatment with

TerraZyme.

Table 10 presents the variation of coefficient of

consolidation of TerraZyme treated black cotton

soil over the untreated soil. The coefficient of

consolidation of treated black cotton soil

exhibited very little variation with increase in

pressure indicating the soil attained structural

stability after treatment.

Table 10 Coefficient of Consolidation of BCS

Combination

Coefficient of Consolidation

(Cv x10-9 in m2/sec)

Pressure Range from (200-

800 kPa)

200 400 800

BCS Alone 1.367 1.801 3.084

BCS + TZ d3

DC 4.183 4.283 4.384

BCS + TZ d3

ADC 4.177 4.283 4.352

Free Swell Index (Differential Free-Swell

Test)

Differential free swell test has been conducted

on the black cotton soil treated with optimum

dosage of TerraZyme and cured for 30 days in

desiccator and air-dry conditions. Table 11

presents the values of Free Swell Index for the

untreated and treated black cotton soil.

Table 11 Free Swell Index for BCS

Combination Free Swell Index (%)

BCS Alone 118

BCS + TZ d3 DC 45

BCS + TZ d3 ADC 27

Free swell index of black cotton soil has

decreased drastically with the treatment from

TerraZyme. The air-dry curing (ADC) condition

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is more effective than desiccator curing (DC) in

stabilizing the expansive soil.

CONCLUSIONS

The suitability of TerraZyme for the

modification of Geotechnical properties of

expansive and non-expansive soils is concluded

by studying the effect of TerraZyme on the index

and engineering properties of black cotton soil

and red earth. Air-dry curing condition was

adopted along with regular controlled laboratory

desiccator curing condition to study the

suitability of TerraZyme for field conditions

during treatment of soils. Based on the test

results, the following conclusions have been

drawn.

TerraZyme stabilization has shown good

improvements in engineering properties of

both black cotton soil and red earth.

Unconfined Compressive Strength of both

black cotton soil and red earth has shown

tremendous increment with drying than

curing in a laboratory desiccator after

treating it with TerraZyme.

Atterberg Limits for both black cotton soil

and red earth did not exhibit any difference

in drying and desiccator curing.

Both black cotton soil and red earth attained

hydrophobic nature with drying after

treatment form TerraZyme as observed

during Atterberg limits test.

The properties of Black cotton soil have

been much improved by stabilizing with

TerraZyme dosage of 200ml/2.0m3 of soil

and for red earth by 200ml/3.0m3 of soil.

Hence this dosage is considered as the

optimum one.

Even Unsoaked CBR of both black cotton

soil and red earth has shown better

improvement with treatment in drying than

in desiccator curing.

Compaction characteristics are not affected

immediately after treatment with

TerraZyme.

Compressibility behaviour of black cotton

soil is improved well with treatment from

TerraZyme.

Black cotton soil showed more structural

stability during oedometer test.

Free Swell Index of black cotton soil

showed drastic reduction with treatment

from TerraZyme especially with drying.

Air-dry curing (or drying) condition proved

more efficient in treating both the soils than

desiccator curing condition.

ACKNOWLEDGEMENTS

The authors are thankful to Mr. Apoorva Modi,

Avijeet Agencies, Chennai for supporting this

project by supplying TerraZyme.

REFERENCES

1. Mohd, R., Taha, Tanveer, A., Khan, Ibtehaj,

Taha, J., Ali, Akbar, Firoozi and Ali,

Asghar, Firoozi (2013), Recent experimental

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