nit surathkal terrabind review

8/9/2019 NIT Surathkal Terrabind Review

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EXPERIMENTAL INVESTIGATION ON BLACK

COTTON SOIL TREATED WITH TERRABIND

CHEMICAL AND FLY ASH

by

VIJETHA R.V

Register No.: 11TS27F

THESIS SUBMITTED FOR THE AWARD OF THE DEGREE OF

MASTER OF TECHNOLOGY

in

TRANSPORTATION SYSTEM ENGINEERING

DEPARTMENT OF CIVIL ENGINEERING

NATIONAL INSTITUTE OF TECHNOLOGY KARNATAKA

SURATHKAL, P.O. SRINIVASNAGAR - 575 025

MANGALORE, INDIA

JULY 2013


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National Institute of Technology Karnataka, Surathkal

D E C L A R A T I O Nby the M.Tech Student

I hereby declare that the Report of the P.G. Project Work entitled EXPERIMENTAL

INVESTIGATION ON BLACK COTTON SOIL TREATED WITH

TERRABIND CHEMICAL AND FLY ASH which is being submitted to the

National Institute of Technology Karnataka Surathkal,in partial fulfilment of the

requirements for the award of the Degree of Master of Technology in the

Department ofCivil Engineering, is a bonafide report of the work carried out by me.

The material contained in this Report has not been submitted to any University or

Institution for the award of any degree.

11TS27F VIJETHA R.V

(Register Number, Name & Signature of the Student)

Department of Civil Engineering

Place: NITK, SURATHKALDate:


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ACKNOWLEDGEMENT

I avail myself of this opportunity to express my gratitude and regards for Dr. A. U. Ravi

Shankar,Professor, Department of Civil Engineering, who has been both the inspiration and the

instrument for the success of the entire project. I thank him for his able and timely guidance

throughout.

It gives me great pleasure to acknowledgeMs. Lekha B.M, Phd Scholar, Department of Civil

Engineering, who has supported and guided me at every stage of the project. I also express my

extreme gratitude towards Mr. Samir Das Gupta, Terra Nova Technologies, for providing,

Terrabind chemical for my present study.

I am deeply indebted to all the faculty members of the Department of civil engineering for their

knowledgeable advice and encouragement throughout the course of the study.

I sincerely acknowledge the valuable help rendered byMr. Sadhanand and Mr. Yatish and all

other non-teaching staff of the Department of Civil Engineering, NITK.

Finally, I would like to thank my family and friends for their support. It would have been

impossible for me to accomplish this study without their support.

Vijetha R.V


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ABSTRACT

Black cotton soil (BC) is one among the problematic soil that has a high potential for shrinking or

swelling due to change in moisture content. Destructive results caused by this soil have beenreported in many countries. Black cotton soil abundantly found in Gadag district of North

Karnataka, are susceptible to detrimental volumetric changes, with changes in moisture. There

have been many methods available for controlling the expansive nature of black cotton soil.

Chemical stabilization is one of the effective methods that can be used to stabilize these soils.

Hence, in the present work, laboratory studies has been carried-out to investigate the influence of

chemical called Terrabind on BC soil and further the influence on BC when Terrabind is added in

combination with fly ash (FA) is investigated. Basic geotechnical properties like grain size

distribution, specific gravity, consistency limits have been determined and engineering properties

like MDD, OMC, Unconfined compressive strength, CBR, Triaxial compression test has been

determined for untreated and treated soil. Swelling properties have been determined by

conducting free swell index test and swell pressure test. Durability of the soil is studied by

conducting wet-dry cycle test and freeze- thaw cycle test. Fatigue test has been conducted to

determine the fatigue life of untreated and treated BC soil. Further chemical analysis was

conducted to determine the chemical composition of untreated and treated soil. From the

experimental results it was observed that consistency limits and dry density improved marginally,

unconfined compressive strength and unsoaked CBR has increased enormously, Soaked CBR has

not increased much. Soil stabilized with Terrabind and FA has showed better results compared to

soil stabilized with Terrabind. Percentage weight loss was less than 14% for 12th

cycle of freeze-

thaw, which shows that the stabilized soil has become durable. Swelling has reduced to a great

extent. Swelling of soil stabilized with Terrabind and fly ash (FA) has reduced by 100%.

.


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CONTENTS

Declaration

Certificate

Acknowledgement

Abstract

Contents

List of figures

List of tables

List of Abbreviations

1.0 INTRODUCTION 1

1.1 GENERAL 1

1.2ROLE OF SUBGRADE 2

1.3SOIL STABILIZATION 3

1.4USES OF STABILIZATION 4

1.5PRINCIPLES OF SOIL STABILIZATION 4

1.6STABILIZATION USING TERRABIND CHEMICAL 5

1.6.1The science behind reacting clay soil with Terrabind 6

1.6.2 Terrabind and Fly Ash (FA) 7

1.6.3 Terrabind chemical constituents 7

1.7 NEED OF PRESENT INVESTIGATION 9

1.8 OBJECTIVES OF PRESENT INVESTIGATION 9

1.9 SCOPE OF WORK 10

2.0 LITERATURE REVIEW 112.1 GENERAL 11

2.2 IDENTIFICATION AND CLASSIFICATION OF SWELLING SOILS 11

2.3 BLACK COTTON SOIL 13

2.4 STABILIZATION TECHNIQUES 14


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2.4.1 Mechanical stabilization 14

2.4.2 Chemical stabilization 15

2.5 TYPES OF STABILIZERS 17

2.5.1 Portland Cement 17

2.5.2 Quick Lime/Hydrated Lime 17

2.5.3 Fly ash 18

2.6 REVIEWS ON RESEARCH FINDINGS ON STABILIZATION OF SOIL USING

TRADITIONAL ADMIXTURES 19

2.7 REVIEWS ON RESEARCH FINDINGS ON STABILIZATION OF SOIL USING

NON TRADITIONAL ADMIXTURES 22

2.8 DURABILITY STUDIES 25

2.9 SUMMARY 26

3.0 CHEMICAL ANALYSIS 27

3.1 GENERAL 27

3.1.1SOIL SPECIMEN 27

3.2 pH OF SOIL BY ELECTROMETRIC METHOD 27

3.3 CONDUCTIVITY OF SOIL BY ELECTROMETRIC METHOD 28

3.4 SILICA CONTENT IN SOIL BY GRAVIMETRIC METHOD 29

3.5 IRON OXIDE (Fe2O3) IN SOIL BY COLORIMETRIC METHOD 30

3.6 R2O3 (Al2O3 + Fe2O3) IN SOIL BY GRAVIMETRIC METHOD 31

3.7 CHLORIDE CONTENT IN SOIL BY ARGENTOMETRIC METHOD 32

3.8 Ca AND Mg OXIDE IN SOIL BY TITRIMETRIC METHOD 33

3.9 CHEMICAL ANALYSIS RESULTS ON UNTREATED AND TREATED SOIL

36

4.0 MATERIALS AND METHODOLOGY 37

4.1 GENERAL 37

4.2 MATERIALS USED 37

4.2.1 Soil 37


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4.2.2 Terrabind 38

4.2.3 Application of Terrabind to BC Soil 38

4.2.4 Class C Fly ash 38

4.2.5 Terrabind dosage 39

4.3

TESTS CONDUCTED ON SOIL 40

4.3.1 Specific Gravity test 40

4.3.2 Grain size analysis test 40

4.3.3 Consistency limits test 40

4.3.4 Compaction tests 41

4.3.5 Unconfined Compression Test 42

4.3.6 California Bearing Ratio Test 42

4.3.7 Triaxial compression test 43

4.3.8 Free swell index 44

4.3.9 Swell pressure 45

4.3.10 Durability 45

4.3.11 Fatigue test 47

5.0 RESULTS AND DISCUSSIONS 50

5.1 GENERAL 50

5.2 TESTS ON BASIC PROPERTIES OF BLACK COTTON SOIL 50

5.3 RESULTS OF TESTS PERFORMED ON BC SOIL TREATED WITH

TERRABIND CHEMICAL AND TERRABIND+ FLY 51

5.3.1 Plasticity Characteristics 51

5.3.2 Compaction test results 53

5.3.3 Unconfined compression test results 54

5.3.4 CBR test results 56

5.3.5 Triaxial test 57

5.3.6 Free swell index 58

5.3.7 Swell pressure 58

5.2.8 Durability 59

5.3.9 Fatigue 61


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6.0 CONCLUSIONS 63

6.1 SCOPE FOR FUTURE STUDIES 65

REFERENCES 66

LIST OF FIGURES

Fig No. Description Page No

2.1: Distribution of black cotton soil in India 14

4.1: Black cotton soil 37

4.2: Casagrande apparatus for determination of liquid limit 41

4.3: Samples prepared for the determination of plastic limit 41

4.4: UCS Samples 42

4.5: Determination of CBR 43

4.6: Triaxial compression testing setup 44

4.7: Free swell index setup 45

4.8: Samples prepared for freeze-thaw & wet-dry cycle test 47

4.9: Samples prepared for freeze-thaw & wet-dry cycle test 47

4.10: Schematic Diagram of Accelerated Fatigue Load Test Set-up 48

5.1: variation of liquid limit of treated soil for different curing period 52

5.2: variation of Plastic limit of treated soil for different curing period 53

5.3: variation of Plasticity index of treated soil for different curing period 53

5.4: variation of maximum dry density of treated soil for different curing 54

5.5: Variation of UCS of treated soil for different curing period 55

5.6: Variation of Unsoaked CBR of treated soil for different curing period 57

5.7: Variation of Soaked CBR of treated soil for different curing period 57

5.8: Graphical representation of freeze-thaw cycles for untreated and treated

BC soil 61


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1

CHAPTER 1

INTRODUCTION

1.1GENERAL

Mobility is fundamental to economic and social activities of any country. Mobility is

provided by the transportation infrastructure and this has a huge impact on the

development and welfare of the population. In several countries, lack of transportation

infrastructure and regulatory controls are jointly impacting economic development.

Moreover, transport systems are among the various factors affecting the quality of

life. Though there are several modes of transport, like road, rail, air, and water, in

many countries road networks cater to the majority of transportation needs. Hence

roadways are the lifeline of our country and the development of road infrastructure

has played a very important role in faster development of the Indian economy. For

example, in India, as per the National Highways Authority of India, about 65% of

freight and 80% passenger traffic is carried by the roads. The National Highways

carry about 40% of total road traffic, though only about 2% of the road network is

covered by these roads. Rural areas have very poor access. About 33% of villages in

India still do not have all-weather road and remains cut-off during monsoon. Average

growth of the number of vehicles has been around 10.16% per annum over recent

years (The Automobile industry in India is rapidly growing with an annual production

of over 2.6 million vehicles). Hence only roads are considered in this project. The

growth of the population has created a need for better and economical vehicular

operation which requires good highways having proper geometric design, pavement

condition and maintenance. The highways have to be maintained so that comfort,

convenience and safety are provided to the travelling public. Problematic soil such as

expansive soil is normally encountered in foundation engineering designs for

highways, embankments, retaining walls, backfills etc. Expansive soil are normally

found in semi-arid regions of tropical and moderate climate zones and are abundant,

where the annual evaporation exceeds the precipitation and can be found anywhere in

the world. (Chen 1975).


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Volume changes: Soil may undergo volume change when exposed to excessive

moisture or freezing conditions. Some clay soil shrink and swell depending upon their

moisture content, while soil with excessive fines may be susceptible to frost heave in

freezing areas.

1.3SOIL STABILIZATION

Stabilization is the process of blending and mixing materials with a soil to improve

certain properties of the soil. The process may include the blending of soil to achieve

a desired gradation or mixing of commercially available additives that may alter thegradation, texture or plasticity, or act as a binder for cementation of the soil. Soil

stabilization is the collective term used to denote any physical, chemical or biological

method or any combination of such methods employed to improve certain properties

of natural soil to make it serve adequately for an intended engineering purpose. The

different uses of soil pose different requirements of mechanical strength and

resistance to environmental forces, controlling method to be used for the stabilization.

Stabilization is being used for a variety of engineering works, the most common

application being in the construction of road and air-field pavements, where the main

objective is to increase the strength or stabilization of soil and to reduce the

construction cost by making best use of locally available materials. In other words,

stabilization includes compaction, preconsolidation, drainage and many other such

processes. A cement material or a chemical is added to a natural soil for the purpose

of stabilization. The decreasing availability and increasing cost of construction

materials and uncertain economic climates force engineers to consider more

economical methods for building roads.

There is an urgent need to identify new materials, improve construction techniques to

achieve economy in construction cost. 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 for better

performance 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


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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, an

appropriate 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 soil for improving strength and durability, a

number of chemical additives, both inorganic and organic, have also been used.

1.4USES OF STABILIZATION

Pavement design is based on the premise that minimum specified structural quality

will be achieved for each layer of material in the pavement system. Each layer must

resist shearing, avoid excessive deflections that cause fatigue cracking within the

layer or in overlying layers, and prevent excessive permanent deformation through

densification. As the quality of a soil layer is increased, the ability of that layer to

distribute the load over a greater area is generally increased so that a reduction in the

required thickness of the soil and surface layers may be permitted.

Quality Improvement: The most common improvements achieved throughstabilization include better soil gradation, reduction of plasticity index or swelling

potential, and increases in durability and strength. In wet weather, stabilization may

also be used to provide a working platform for construction operations. These types of

soil quality improvement are referred to as soil modification.

Thickness reduction: The strength and stiffness of a soil layer can be improved

through the use of additives to permit a reduction in design thickness of the stabilized

material compared with an unstabilized or unbound material. The design thickness

strength, stability, and durability requirements of a base or sub base course can be

reduced if further analysis indicates suitability.

1.5 PRINCIPLES OF SOIL STABILIZATION

The principles of soil stabilization are:

1. Densification of soil by decreasing the air voids.

2. Increasing the compaction using well graded soil mass.


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3. Designing the soil mix for intended stability and durability values.

4. Reducing the adsorbed water layer of clay particle to achieve maximum

compaction.

The process of soil stabilization is useful in the following applications,

1. Reducing the permeability of soil.

2. Increasing the bearing capacity of foundation soil.

3. Increasing the shear strength of soil.

4. Improving the durability and life span of the structures under adverse moisture

and stress conditions.

5. Improving the natural ground for the construction of highways and airfields.

6. Controlling the grading of soil and aggregates in the construction of bases and

Sub bases of the highway and airfields.

The needs for soil stabilization in the present scenario are

1. Limited financial resources make it difficult to provide a complete network

road network system using conventional method of construction.

2. Effective utilization of locally available soil and other suitable stabilizing

agents.

3. Environment friendly procedures to encourage the use of industrial wastages

to reduce the cost of construction of roads.

1.6 STABILIZATION USING TERRABIND CHEMICAL

The need to replace clay soil in the embankment/ sub grade layer is eliminated/

reduced with Terrabind treatment. The reaction of Terrabind with clay soil creates a

permanent reaction in the molecular structure of clay soil particles rendering reduced

swell potential, greater compaction, load bearing and soil particle cohesiveness.

Terrabind will improve engineering properties (compaction, cohesion, load bearing)

of soil and crushed macadam road base designs by 25% - 150%.


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Conventional soil stabilization techniques involve chemicals molecules attaching to

clay soil grains. However, these chemicals molecules get washed away with rising

ground water. Terrabind alters the very molecular structure thus the characteristics of

the soil clatter permanently. With terrabind, road developers can reduce pavement

thickness, lower initial construction costs, improve logistical efficiency. Lower life

cycle costs and minimize human error while increasing road base strength and

durability when compared to their planned design mix. World over, this stabilization

technology has proved its capability. Terra Nova technologies manufactures the same

technology in India at a lower cost.

1.6.1 The science behind reacting clay soil with Terrabind

1. Terrabind attacks the clay lattice of the soil which alters the ionic charge in

clay and creates a chemical bond between the clay particles.

2. Terrabind reduces shrink and swell by forming a chemical and physical bond

between the clay particles that resist water absorption. This allows the

moisture content of the soil to stabilize which reduces the movement of the

soil.

3. Terrabind breaks down the capillary action of soil particles thus reducing the

moisture retentive nature of most expansive soil.

4. Terrabind distributes the mineral ions evenly throughout the mixture, thereby

increasing particulate attraction and decreasing voids resulting in increased

material density and hardness while maintaining flexibility.

5. The interaction of its components activates and binds the naturally occurring

mineral cements in soil together to form a material analogous to most

sedimentary rocks.

6. More effective than lime in high sulphate soil (lime reaction in such soil leads

to volume expansion leading


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1.6.2 Terrabind and Fly Ash (FA)

Terrabind in combination with Fly ash is highly recommended for use in combination

with Terrabind. Terrabind has a catalyst effect when combined in clay soil with fly

ash. 5%-10% fly ash (Class C) by weight of soil is an ideal range.

1.6.3 Terrabind chemical constituents

Terrabind is an advanced proprietary electrolyte lignin emulsion and a highly

concentrated liquid chemical. The science behind Terrabinds formulation focuses on

creating three primary changes in soil molecules;

1. Alter the ionic exchange responsible for water attraction in soil molecules.

2. Break down capillary action responsible for water retention (swell/shrink).

3. Activate aluminosilicates within soil to increase particle binding and layer

density.

Lignins and lignosulphonates: Lignin is the active chemical compound responsible

for binding cells and fibres in trees and plants. Lignins provide the required tensileand compressive strength for trees to grow vertically without being drawn to the

ground. Terrabind formulation consists of a proprietary combination of

lignosulphonates (that contain calcium hydroxide) and organic lignins that allow for

polymeric binding between soil grains.

Electrolyte emulsion: The electrolyte emulsion attacks the clay lattice of soil by

altering the ionic charge in clay and breaking down the capillary action of clay soil

particles thus reducing the ability for soil particles to attract and retain moisture. This

results in reduced shrink and swell of soil particles. The electrolyte emulsion also

stabilizes the moisture level resulting in reduced soil particle movement.

The process of mechanical mixing of the electrolyte emulsion and lignins in Terrabind

and with soil activates aluminosilicates present in soil that catalyses the absorption of

mineral ions resulting in strong polymeric binding, greater layer density and reduced

voids.


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The addition of cementitous binders (lime/fly ash/cement) with Terrabind treatment of

soil further strengthens soil because Terabind catalyses the activation of

aluminosilicates in soil along with the calcium hydroxide present in cementitous

binders. Additionally, the properties of emulsions allows for greater workability of the

materials with lesser moisture thus resulting in a more uniform mix and greater

absorption of cementitous components with soil molecules.

Table 1.1 shows the physical properties of Terrabind chemical.

Table1.1 Physical properties of Terrabind

Description Properties

Form Liquid

Odor Sharp,sulfurous

Color Dark Amber

Toxicity See Cautions

Wetting Ability Excellent

Detergency None

Foaming None

Emulsification None

Phosphates None

Storage 2 Years

Cold Stability Excellent

Flash Point None

Boiling Point 182 degrees C

Solubility in Water Complete

Specific Gravity 1.7

Ph 1

Weight per gallon 14.19 lb.


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1.7 NEED OF PRESENT INVESTIGATION

In recent years, more attention has been given to the use of various non-traditional

chemicals such as sulfonated oils, potassium compounds, ammonium chloride,

enzymes, polymers and so on as soil stabilizers due to expansion in manufacturing

capacity, low cost, and relatively wide applicability compared to standard stabilizers

(hydrated lime, Portland cement, and bitumen) which require large amounts of

stabilizers to stabilize soil thus leading to higher costs. The process has not been

subjected to a rigorous technical investigation and is presently carried out using

empirical guidelines based on experience. Thus we need to investigate the

stabilization mechanism of some of the commercially available chemical based

products to better understand their potential value for road construction.

Terrabind is one such chemical manufactured by Terra Nova technologies for the first

time in India. World over, this stabilization technology has proved its capability.

Limited laboratory experiments are performed to determine if these products improve

the material properties of soil and if they offers superior mechanical properties

compared to other types of stabilization for which comprehensive laboratory and field

performance already exists. It becomes therefore important to perform a research

study that can give required scientific support to the use of Terrabind as soil stabilizer.

Since black cotton soil is one of the problematic soils, terrabind is used to stabilize

this soil to prove its capability.

1.8OBJECTIVES OF PRESENT INVESTIGATION

The investigation is carried out on black cotton soil (expansive soil), which is a majortype of soil available in Northern Karnataka. In order to overcome the high shrinkage

and swelling properties of this soil, stabilization is a must to prevent destruction of

structures built on it. This soil is having very poor geotechnical properties. The liquid

limit and plasticity index are very high (>50 and >30 respectively) and to improve

these properties, laboratory investigation has been conducted by stabilizing the soil

with Terrabind chemical. Although there are variety of chemicals available in the

market, only limited research has been performed on effectiveness of use of these


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chemicals as stabilizing agent. Proper investigation is very much essential to

determine the potential of Terrabind in improving the geotechnical properties of soil.

Objectives of the present investigation are:

1) The general objective of this investigation is to study the engineering properties of

black cotton soil treated with a Terrabind Stabilizer. The influence of applying

this stabilizer has been examined via various laboratory tests.

2) To study the suitability of the commercial stabilizer for stabilizing BC soil.

3)

To Study the fatigue behavior of stabilized soil under repeated load condition.4) To determine the durability of the treated and untreated BC soil.

5) To study the swelling characteristics of treated soil.

6) To determine the chemical composition of untreated and treated soil.

1.9 SCOPE OF WORK

To meet the above mentioned objectives, BC soil obtained from Gadag district

situated in North Karnataka is used for the study. Laboratory experiments are

performed to evaluate the geotechnical properties of the soil. To find the variation in

strength properties, soil is blended with commercially available chemical called

Terrabind and further Terrabind + fly ash combination is also tried on the soil and its

strength properties were determined. The performance of Terrabind treated soil is

investigated for different curing period. To study the performance of soil (untreated

and treated) under repeated load condition, fatigue test has been conducted under

different load condition and its performance at different curing period is studied.

Swell pressure test and free swell index test is conducted on treated and untreated soil

to determine the improvements in swelling properties of treated soil. Chemical

composition of soil is determined by performing various laboratory chemical tests.

Further freeze-thaw and wet-dry test is performed to determine the durability of the

stabilized soil.


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CHAPTER 2

LITERATURE REVIEW

2.1 GENERAL

For centuries humankind has wondered at the instability of earth materials, especially

expansive soil. One day they are dry and hard, and the next day wet and soft.

Expansive soil has always presented problems for lightly loaded structures,

pavements, by consolidating under load and by changing volumetrically along with

seasonal moisture variation. The results are usually excessive deflections and

differential movements resulting in damage to foundation systems, structural

elements, and architectural features. In a significant number of cases the structures

become unusable or uninhabitable. Even when efforts are made to improve these

soils, the lack of appropriate improvements sometimes results in volumetric changes

that are responsible for billions of dollars of damage each year. (Warren and Kirby

2004).Therefore, we need to do more to develop our knowledge of proven methods to

deal with expansive soil, support research for further improvement of these methods,

and work towards better quality control and quality assurance for their application.

Expansive soil has a high potential for shrinking or swelling due to change of

moisture content. The primary problem that arises with regard to expansive soil is that

deformations are significantly greater than the elastic deformations and they cannot be

predicted by the classical elastic or plastic theory. Movement is usually in an uneven

pattern and of such a magnitude to cause extensive damage to the structures resting on

them. Expansive soil can be found on almost all the continents on the Earth.Destructive results caused by this type of soil have been reported in many countries.

2.2 IDENTIFICATION AND CLASSIFICATION OF SWELLING SOILS

For identification of swelling soils, some laboratory tests are available. Clay minerals

can be known by microscopic examination, X-ray diffraction and differential thermal

analysis. From clay minerals by the presence of montomorillonite, the expansiveness


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of the soil can be judged. Another simple way of finding out expansiveness in

laboratory is free-swell test.

It is reported that good grade high swelling commercial Bentonite will have a free

swell values 1200% to 2000%. Soil having free swell values as low as 100% may

exhibit considerable volume change, when wetted under light loading, and should be

viewed with caution. Where soils is having free swell values below 50% seldom

exhibit appreciable volume changes, even under very light loadings. But these limits

are considerably influenced by the local climatic conditions (Holtez and Gibbs

1956).

The free swell test should be combined with the properties of the soil. A liquid limit

and plasticity index, together pointers to swelling characteristic of the soil for large

clay content. Also the shrinkage limit can be used to estimating the swell potential of

a soil. A low shrinkage limit would show that a soil could have volume change at low

moisture content. Weather a soil with high swelling potential will actually exhibit

swelling characteristics depends on several factors. That of greatest importance is

difference between field soil moisture content at the time the construction is under

taken and the equilibrium moisture content that will finally be achieved under the

conditions associated with the complicated structure. If the equilibrium moisture

content is considerable and higher than field moisture content, then the soil is of high

swelling capacity, vigorous swelling may occur by upward heaving of soil or structure

by the development of large swelling pressure.

Potentially expansive soils are usually recognized in the field by their fissured or

shattered condition, or obvious structural damage caused by such soils to existing

buildings. The potential expansion or potential swell or the degree of expansion is aconvenient term used to classify expansive soils from which soil engineers ascertain

how good or bad the potentially expansive soils are. Many criteria are available to

identify and characterize expansive soils, such as liquid limit, plasticity index, free

swell index (Sridharan and Prakash 2000) .The following table gives the various

criteria proposed for classifying expansive soils.


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Table 2.1 Classification of swelling soils as per (IS: 1498)

Degree of

expansion

L.L

(%)

P.I

(%)

FSI

(%)

Degree of

severity

Low 20-35 < 12 < 50 Non critical

Medium 35-50 12-23 50-100 Marginal

High 50-70 23-32 100-200 Critical

Very high 70-90 > 32 > 200 Severe

2.3 BLACK COTTON SOIL

In India, large tracts are covered by expansive soil known as black cotton soil. Black

cotton soil occurs mostly in the central and western parts and covers an area of about

5.4 lakh square kilometers and thus form about 20% of the total area of India, which

extends over the states of Maharashtra, Madhya Pradesh, Karnataka, Andhra Pradesh,

Tamil Nadu and Uttar Pradesh as shown in the Fig. 2.1. The major area of their

occurrence is the south Vindhyachal range covering almost the entire Deccan Plateau

(Muthyalu et al. 2012). Deposits of BC soil in the field show a general pattern of

cracks during the dry season of the year. Cracks measuring 70 mm wide and over 1 m

deep have been observed and may extend up to 3m or more in case of high deposits .

As a result of wetting and drying process, vertical movement takes place in the soil

mass. All these movements lead to failure of pavement, in the form of settlement,

heavy depression, cracking and unevenness. Black cotton soil has a high percentage

of clay minerals and iron oxide, some calcium carbonate, and a low organic content.

They are predominantly rich in montmorillonitic clays of high base exchange capacity

which generally ranges from 50 to 70 equiv/100g. These soils have presented serious

problems to vehicular traffic during the rainy season as the natural subgrade soil

becomes wet and sticky, and so soft that its bearing capacity becomes almost nil.

Even when stone boulders are laid as pavement over the natural subgrade soil, during

rains the stone has a tendency to sink into the soft subgrade. Because of the extensive

occurrence of this soil, it is not economically feasible to replace it by a better

subgrade material.


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Figure 2.1: Distribution of black cotton soil in India

2.4 STABILIZATION TECHNIQUES

Broadly, soil stabilization takes the following forms.

1. Mechanical stabilization

2.

Chemical stabilization

2.4.1 Mechanical stabilization

Mechanical soil stabilization refers to either compaction or the introduction of fibrous

and other non-biodegradable reinforcement to the soil. This practice does not require

chemical change of the soil, although it is common to use both mechanical and


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chemical means to achieve specified stabilization. There are several methods used to

achieve mechanical stabilization:

Compaction: Compaction typically employs a heavy weight to increase soil density

by applying pressure from above. Machines are used for this purpose; large soil

compactors with vibrating steel drums efficiently apply pressure to the soil, increasing

its density to meet engineering requirements. Operators of the machine must be

careful not to over compact the soil, for too much pressure can result in crushed

aggregates that lose their engineering properties.

Soil Reinforcement: Soil problems are sometimes remedied by utilizing engineered

or non-engineered mechanical solutions. Geo-textiles and engineered plastic mesh are

designed to trap soil and help control erosion, moisture conditions and soil

permeability. Larger aggregates, such as gravel, stones, and boulders, are often

employed where additional mass and rigidity can prevent unwanted soil migration or

improve load-bearing properties.

Addition of graded aggregate materials: A common method of improving theengineering characteristics of a soil is to add certain aggregates that lend desirable

attributes to the soil, such as increased strength or decreased plasticity. This method

provides material economy, improves support capabilities of the sub grade, and

furnishes a working platform for the remaining structure.

2.4.2 Chemical Stabilization

One method of improving the engineering properties of soil is by adding chemicals or

other materials to improve the existing soil. Generally, the role of the stabilizing

(binding) agent in the treatment process is either reinforcing of the bounds between

the particles or filling of the pore spaces. It includes mixing or injecting additives

such as lime, cement, sodium silicate, calcium chloride, bituminous materials and

resinous materials with or in the soil to increase stability of the soil. This technique is

generally cost effective: for example, the cost of transportation, and processing of a


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stabilizing agent or additive such as soil cement or lime to treat an in-place soil

1material will probably be more economical than importing aggregate for the same

thickness base course. The selection of the type and the determination of the

percentage of the additive to be used are dependent upon the soil classification and the

degree of improvement in soil quality desired. In general, smaller amounts of

additives are required when it is simply desired to modify soil properties such as

gradation, workability, and plasticity. When it is desired to improve the strength and

durability significantly, larger quantities of additive are used. After the additive has

been mixed with soil, spreading and compaction are achieved by conventional means.

Soil modification refers to the chemical stabilization process that results in

improvements of some properties of the soil for improved constructability, but does

not provide the designer with a significant increase in soil strength and durability.

Additives can be mechanical, meaning that upon addition to the parent soil their own

load-bearing properties bolster the engineering characteristics of the parent soil.

Additives can also be chemical, meaning that the additive reacts with or changes the

chemical properties of the soil, thereby upgrading its engineering properties. Placing

the wrong kind or wrong amount of additive or, improperly incorporating the additive

into the soil can have devastating results on the success of the project. So, in order to

properly implement this technique, an engineer must have:

1. A clear idea of desired result.

2. An understanding of the type(s) of soil and their characteristics on site.

3. An understanding of the use of the additive(s), how they react with the soil

type and other additives, and how they interact with the surrounding

environment.4. An understanding of and means of incorporating (mixing) the additive.

5. An understanding of how the resulting engineered soil will perform.


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2.5.3 Fly ash

Coal burning electric utilities annually produce million tons of fly ash as a waste

byproduct and the environmentally acceptable disposal of this material has become an

increasing concern. Efforts have always been made by the researchers to make

pertinent use of fly ash in road constructions in the localities which exists in the

vicinity of thermal power stations. One of the most promising approaches in this area

is use of fly ash as a replacement to the conventional weak earth material will solve

two problems with one effort i.e. elimination of solid waste problem on one hand and

provision of a needed construction material on other. Also, this will help in achievingsustainable development of natural resources.(Koteswara et al. 2012)

Fly ash, a chemical additive consisting mainly of silicon and aluminum compounds, is

a by-product of the combustion of coal. Fly ash can be mixed with lime and water to

stabilize granular materials with few fines, producing a hard, and cement like mass.

Its role in the stabilization process is to act as a pozzolan and/or as a filler product to

reduce air void. Fly-ash reduces the potential of a plastic soil to undergo volumetric

expansion by a physical cementing mechanism, which cannot be evaluated by the

plasticity index. Fly ash controls shrink- swell by cementing the soil grading together

much like a Portland cement bonds aggregates together to make concrete. By bonding

the soil grains together, soil particle movements are restricted. Fly ash is a pozzolan.

It has been successfully used with granular and fine grained materials to improve soil

characteristics, providing adequate support for pavements and improving working

conditions where undesirable soil are encountered. Fly ash and other ash such as

bottom ash and boiler ash have been widely used in application with source. The

factors that most readily influence the quality and reactivity of fly ashes are the source

of the coal, the degree of pulverization of coal, the efficiency of the burning operation

and the collection and storage method of the ash (Pankaj et al. 2012).


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2.6 REVIEWS ON RESEARCH FINDINGS ON STABILIZATION OF SOIL

USING TRADITIONAL ADMIXTURES

The weak subgrade of cohesive soils, having low shear strength and low stiffness,

require improvement in their properties before using them as construction material.

(Tastan et al. 2011) .Chemical stabilization for these soils is a popular method,

widely used to improve their shear strength as well as stiffness. In general, it consists

of blending lime with cohesive soils or mixing Portland cement with non-cohesive

soils. This technique is widely used in road rehabilitation or in reprocessing of road

base materials for increasing life of the structure. Chemical stabilization, used todecrease the potential for local shear failure of subgrade, eliminates surface pumping

or rutting and extends the life of pavement structure. It also results in the increase of

stiffness and thus, the designer can have advantage of strength and stiffness .

Many studies have been carried out regarding stabilization of soil using various

traditional stabilizers like lime, cement, fly ash etc. Following are the few reviews of

literature on stabilization of soil using traditional stabilizers. The microstructure of

cement-treated marine clay has been investigated using XRD, SEM, and Laser

diffractometric measurement. Results indicate that the magnitude of changes in the

properties and behavior of cement-treated marine clay is due to the interaction of four

underlying microstructural mechanisms. These mechanisms are the production of

hydrated lime by the hydration reaction which causes flocculation of the illite clay

particles, preferential attack of the calcium ions on kaolinite rather than on illite in the

pozzolanic reaction, surface deposition and shallow infilling by cementitious products

on clay clusters, as well as the presence of water trapped within the clay clusters

(Chew et al. 2004).

A lot of studies have been carried out regarding stabilization of soil treated with fly

ash. Soils are either treated only with fly ash or are used in combination with any

other stabilizer. Some of the studies reviewed in this paper are as follows. The

effectiveness of using various percentages of high calcium fly ash and cement in

stabilising fine-grained clayey soil has been studied by conducting uniaxial


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compression, in indirect (splitting) tension and flexure and 90-day soaked CBR test.

Further analysis of Pavement structures for construction traffic and for operating

traffic incorporating subgrades improved by in situ stabilisation with fly ash and

cement were made which showed very good results compared to conventional flexible

pavements without improved subgrades (Kolias et al. 2005). Similarly BC soil

stabilized by adding different percentages of fly ash (i.e., 5, 8, 10, 12, and 15%) and

Rice Husk Ash (RHA) (i.e., 3, 6, 9 11, 13, and 15%) were subjected to various

laboratory studies. Results indicate that, addition of fly ash and RHA reduces the PI

and specific gravity of the soil. The moisture and density curves indicate that addition

of RHA results in an increase in OMC and decrease in MDD, while these values

decrease with addition of fly ash. UCS and CBR values were increased indicating the

improvement in the strength properties of the stabilized soil (Laxmikant et al. 2011).

(Pankaj et al. 2012) evaluated BC soil properties by adding different quantities of

Lime and fly ash (% by weight). The result showed that the use of Lime and fly ash

increases the CBR values. It was concluded that thickness of pavement can be

decreased by 66% as the CBR value was increased considerably after stabilization and

in combination; the admixtures are beneficial for lower plasticity and higher silt

content soil. In terms of material cost, the use of less costly fly ash can reduce the

required amount of lime

The geo-engineering properties such as Atterberg limits, grain size distribution, linear

shrinkage, swelling pressure, compaction characteristics, UCS and CBR of highly

plastic commercial clay were stabilized using different proportion of fly ash i.e. at 0,

20, 40, 60, 80, and 90 % and the results were evaluated. It was observed that PI of

clay-fly ash mixes decreased with increase in fly ash content i.e. addition of fly ash

made expansive soil less plastic and increased its workability by colloidal reaction

and changing its grain size. The FSI value and SP decreased with increase in fly ash

content. OMC reduced with increase in fly ash content but the MDD increased upto

an fly ash content of 20%, thereafter, the same decreases with further increase in fly

ash content. UCS of clay-fly ash mixes were found to be maximum at 20% fly ash

content and thereafter it reduced with further increase in fly ash content. This shows


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that there exists an optimum fly ash content that gives better compressive strength. It

was also observed that the CBR values of clay-fly ash mixes, tested under un-soaked

conditions, showed peaks at 20% and 80% fly ash content (Bidula 2012). Similarly

(Tastan et al. 2011)studied the effectiveness of fly ash in the stabilization of organic

soil and the factors that are likely to affect the degree of stabilization. It was found

that the unconfined compressive strength of organic soil can be increased using fly

ash. Resilient moduli of the soil showed significant improvement. It was observed that

strength and stiffness are attributed primarily to cementing caused by pozzolanic

reactions, and the reduction in water content is due to the addition of fly ash. The

pozzolonic effect appears to diminish as the water content decreases. Soil organic

content is a detrimental characteristic for stabilization. Increase in organic content of

soil indicates that strength of the soilfly ash mixture decreases exponentially.

Many by-products other than fly ash have been used in the stabilization of various

soils and its effectiveness has been reported and discussed. Clayey soil stabilized

using various dosages of cement kiln dust, volcanic ash and their combinations have

beenevaluated through Atterberg limits, standard proctor compaction, UCS, splitting

tensile strength, modulus of elasticity and CBR tests. The durability properties of 14

stabilized soil mixtures were also investigated by studying the influence of water

immersion on strength, water absorbtivity and drying shrinkage. Developed stabilized

soil mixtures showed satisfactory strength and durability (Hossain and Mol 2011).

Mill scale, a waste product found in metal industry which mainly contains iron oxide

was treated with BC soil in varying proportions and its mechanical properties were

evaluated. It was found that mixing mill scale in varying proportions increases the

permeability of the soil, strength characteristics and decreases the plasticity. The CBR

value of BC soil mixed with 15% mill scale was increased by three times that of plain

BC soil. The permeability value of BC soil increased manifolds by increasing the

percentage of mill scale and the plasticity of the BC soil was decreased from 35.71%

to 30.60% by adding 12% of mill scale (Murthy et al. 2012).

(Rao et al. 2012)conducted a laboratory studies to stabilize BC soil using Cement

kiln dust (CKD)as an admixture with and without adding polymer fibers .This study


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revealed that the fiber reinforcement improves the soil properties in terms of

improved stress-strain patterns and progressive failure in place of quick post peak

failure of plain samples. It was observed that the UCS of Clay soil increased by 7

times with admixture stabilization and 9 times for admixture with fiber modification

with respect to plain samples. The shear strength parameters of clay soil significantly

increased upon admixture stabilization and admixture with fiber treatment. The CBR

value was increased significantly even for soaked CBR tests. By addition of CKD the

LL and PI of the mixture was decreased by 23 % and 57% respectively, where as

plastic limit was increased by 41%.

2.7 REVIEWS ON RESEARCH FINDINGS ON STABILIZATION OF SOIL

USING NON TRADITIONAL ADMIXTURES

Nontraditional stabilization additives have become increasingly available for

commercial and military applications. These products were divided into 7 categories:

salts, acids, enzymes, lignosulfonates, petroleum emulsions, polymers, and tree resins.

Many of these stabilizers are advertised as requiring lower material quantities,

reduced cure times, higher material strengths, and superior durability compared to

traditional stabilization additives. Unfortunately, little research has been completed to

distinguish between products that deliver enhanced performance and those that do not.

The nature of soil stabilization dictates that products may be soil-specific and/or

environment-sensitive. In other words, some products may work well in specific soil

types in a given environment, but perform poorly when applied to dissimilar materials

in a different environment. The rapid evolution of existing products and introduction

of new stabilizers further complicate the process of defining the performance

characteristics of the various nontraditional soil stabilization additives.

A review of the literature indicates that there has been a large quantity of research

completed regarding the application of traditional stabilization additives such as lime,

cement, and fly ash. However, little independent research has been documented

pertaining to the use of nontraditional stabilization additives. A large quantity of

advertisements, pamphlets, and videos has been distributed testifying to the benefits

of a particular stabilization additive. Unfortunately, most of the information disclosed


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in these media is subjective and nontraditional engineering properties are poorly

documented. Following are the few reviews of literature on stabilization of soil using

nontraditional stabilizers.

(Gopal and Singh 1983)studied the effectiveness of urea-formaldehyde (UF) and its

copolymers when treated with dune sand.It was found that the maximum unconfined

compressive strength of 165 kg/sq.cm (density= 1.68 gm/cc) of the standard

specimen, made by a novel technique using this resin (9%), catalyst (0.3%) and sand

(90.7%), was higher than the strengths ranging from 11.3 to 105 kg/sq. cm reported

by earlier workers using UF and other modified phenol formaldehyde resins.(Majebi

et al. 1991) tested a poorly graded clay-silt by treating it with several organic

additives of which the two-part epoxy system bisphenol A/epichlorohydrin resin plus

a polyamide hardener showed the best dry CBR results . (Estabragh et al. 2011)

investigated the soil-cement mixture by adding different percentage of acrylic resin to

improve the engineering properties of the soil for construction. The results showed

that by increasing the cement content in the soil-cement mixture, MDD increases and

OMC decreases in compaction tests. Compressive strength tests on soil-cement

showed that the increase in strength depends on the cement content and the curing

time. The results also indicated that the strength of soil-cement is increased

considerably by adding acrylic resin as an additive material. It was observed that for

given cement content, the increase in shear strength is a function of curing time and

amount of resin.(Thyagaraj 2012)made an attempt to study the precipitation of lime

in the soil by successive mixing of CaCl2and NaOH solutions with the expansive soil

in two different sequences. Experimental results indicated that in-situ precipitation of

lime in the soil by sequential mixing of CaCl2 and NaOH solutions with expansivesoil developed strong lime modification and soil-lime pozzolanic reactions. The lime

modification reactions together with the poorly developed cementation products

controlled the swelling potential, reduced the plasticity index and increased the

unconfined compressive strength of the expansive clay cured for 24 hours. Both lime-

modification reactions and well developed crystalline cementation products (formed

by lime-soil pozzolanic reactions) contributed to the marked increase in the


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unconfined compressive strength of the expansive soil that were cured for periods of

7-21 days.

Some of the soil stabilization studies were based on improvement in strength

properties only and few papers have investigated on both strength and the swelling

properties of soil. Following are some of reviews based on improvement in swelling

properties of soil.

(Cai et al. 2006)worked on reducing the brittleness of soil stabilized by lime only by

mixing the soil with a newly proposed mixture of polypropylene fibre. Nine groups of

treated soil specimens were prepared and tested at three different percentages of fibrecontent (i.e. 0.05%, 0.15%, 0.25% by weight of the parent soil) and three different

percentages of lime (i.e. 2%, 5%, 8% by weight of the parent soil). It was observed

that increase in lime content resulted in an initial increase followed by a slight

decrease in unconfined compressive strength, cohesion and angle of internal friction

of the clayey soil and it led to a reduction of swelling and shrinkage potential.

Increase in fibre content caused an increase in strength and shrinkage potential but

brought on the reduction of swelling potential and increase in curing duration

improved the unconfined compressive strength and shear strength parameters of the

stabilized soil significantly. (Bose et al. 2009)studied the performance expansive soil

when treated with different percentages of gypsum (2.5%, 5%, 7.5%, and 10% by

mass) (bentonite) by means of swell potential and strength. Atterberg limits, FSI and

UCS tests were performed on treated and untreated samples, after a curing period of 7

days. Appropriate curing time for optimum improvement was determined by

obtaining the swell percent variation with cure time up to 2 months using the

considered maximum gypsum content (10% by mass) for the mixture. It was found

that the most important change quickly occurred in the first week, and curing period

of 7 days was accepted as a cure time for optimum improvement in this study. There

was a valuable decrease in liquid limit and plasticity index of the treated soil which

indicated that gypsum can be used as a stabilizing agent for expansive clay soil,

effectively. (Manchikanti et al. 2011) conducted field studies on expansive soil

subgrades by treating it with KCl, CaCl2 and FeCl3 because of their ready


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dissolvability in water and supply of adequate cations for ready cation exchange.

Moreover, they can be applied to the ground in the form of electrolyte solution.

Results of heave recorded from the untreated and treated test tracks were compared. It

was observed that FeCl3treated test track showed the best performance. Results

showed that there was reduction in maximum heave by 22%, 30%, 43%, respectively

for KCl-treated, CaCl2-treated, FeCl3- treated with respect to the untreated test track

and the time taken to attain the maximum heave for FeCl3-treated test track is nearly

one-half, of the time taken by the untreated test track to attain its maximum heave,

better than the other treatments. From the test results, it was concluded that FeCl3 is

the best treatment to reduce the heave.

2.8 DURABILITY STUDIES

Variations in climatic conditions have been recognized by pavement engineers as a

major factor affecting pavement performance. These variations resulting from freeze

thaw (F-T) and wetdry (W-D) actions, or a combination of these actions, have been

presented in a number of previous studies. Importance of climatic conditions has also

been emphasized by AASHTO (2005) and by(Little et al. 2005), among others. The

influence of such actions on a pavement structure indicates possible changes in the

engineering properties of associated pavement materials. To this end, several studies

have been undertaken to evaluate the performance of pavement materials under these

actions. Specifically, during the last few decades increased emphasis has been placed

by transportation agencies and researchers to better understand the behavior of

stabilized aggregate bases and subgrade soil under freezethaw and W-D cycles. This

research area, however, is still not fully explored and additional studies are needed

(Little et al. 2005). (Homoud et al. 1995) investigated the effect of cyclic wetting

and drying on the expansive characteristics of clays. For this purpose six expansive

soils were obtained from various locations in Irbid (a city in northern Jordan). After

each cycle the swell potential and swell pressure were measured. The experimental

data indicated that upon repeated wetting and drying the soil showed sign of fatigue

after every cycle resulting in decreased swelling ability. Furthermore it was noted that

the first cycle causes the most reduction in swelling potential. As the number of


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cycles increases additional reduction was observed until an equilibrium state is

reached. Scanning electron micrographs clearly showed a continuous rearrangement

of particles during cyclic wetting and drying. This led to lower structural element

orientation due to the integration of structure along the bedding resulting in

correspondingly lower water absorption thus reducing swelling ability. Cyclic wetting

and drying results in particle aggregation as demonstrated by the reduction in clay

content and plasticity (LL and PI) between the initial and final cycles. This inevitably

caused a reduction in swelling characteristics.

2.9SUMMARY

From the above literature reviews it can be observed that the soil stabilized using both

traditional and nontraditional stabilizers have given good results. Traditional

stabilizers are usually required in large quantity and are uneconomical compared to

nontraditional stabilizers. It has been observed that most of the papers have

concentrated on improvement in strength parameters and very less study has been

made on improvements in swelling properties of soil which is one of the important

properties of expansive soils and very fewer studies have been made on durability of

stabilized soil. Admixtures like locally available industrial wastes, by products etc

have given good results. It is also observed that in many papers FA used in

combination with other stabilizers have given better results compared to the use of

only one stabilizer. Limited efforts are made to use of nontraditional liquid stabilizers

to stabilize the soil. Taking all this in note the following study is based on stabilizing

BC soil which is one of the problematic expansive soils found abundantly in North

Karnataka region by a liquid stabilizer called Terrabind and later Terrabind is used in

combination with FA. Improvement in strength, changes in swelling properties and

durability of the treated soil is studied and discussed.


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CHAPTER 3

CHEMICAL ANALYSIS

3.1 GENERAL

Chemical analysis has been performed on untreated and treated soil sample to

determine its composition. The tests are conducted as per IS 2720 (Part-26).This

chapter briefly describes the procedure of various laboratory chemical tests conducted

on soil samples.

3.1.1 SOIL SPECIMEN

The soil sample received from the field is prepared in accordance with IS: 2720 (part -

1)1983.All aggregation of particles is broken down so that the soil sieved on 425

IS sieve retains only discrete particles.

3.2 pH OF SOIL BY ELECTROMETRIC METHOD

Procedure

1. 30 gms of soil sample prepared as per IS: 2720 (part-1) is taken in a 100 ml

beaker.

2. 75 ml of distilled water is added to it and stirred for few seconds.

3. Then the beaker is covered with a cover glass and allowed to stand for one

hour with occasional stirring. The solution is stirred again immediately before

testing

4. The pH meter is calibrated by means of the standard buffer solution following

the procedure recommended by the manufacturer.

5. The electrode is first washed with distilled water dried with help of an

ordinary filter paper and then immersed in the soil specimen.

6. Three readings of the pH of the soil suspension are taken with brief stirring in

between each reading.


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7. The pH readings of the soil suspension are taken when a constant value is

reached and the electrode is removed from the suspension immediately and

washed with distilled water.

8. Calibration of the pH meter is checked with one of the standard buffer

solutions.

9. pH meter directly provided the pH values.

3.3 CONDUCTIVITY OF SOIL BY ELECTROMETRIC METHOD

Buffer solutions:following buffer solutions are used for the test.

1. Buffer solution pH 4.0 (at 250c) -5.106 gms of potassium hydrogen

phthalate dissolved in distilled water and diluted to 500ml with distilled

water.

2. Buffer solution pH 9.2 (at 250c) - 9.54 gms of sodium tetraborate (borax)

dissolved in distilled water and diluted to 500 ml.

Procedure

1. 30 gms of soil prepared as per IS: 2720 (part-1) is taken in a 100 ml

beaker.

2. 75 ml of distilled water is added to it and the suspension is stirred for a few

seconds.

3. The beaker is then be covered with a cover glass and allowed to stand for

one hour with occasional stirring .the suspension is stirred again

immediately before testing.

4. The pH meter is calibrated by means of the standard buffer solution

following the procedure recommended by the manufacturer.

5. The electrode is washed with distilled water dried with help of an orginary

filter paper and then immersed in the soil specimen.

6. Two or three readings of the pH of the soil suspension are made with brief

stirring in between each reading.


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7. The pH readings of the soil suspension are taken when a constant value is

reached. Then the electrode is removed from the suspension immediately

and washed with distilled water.

8. In calibration of the pH meter is again checked with one of the standard

buffer solutions.

9. pH meter directly provides the conductivity values.

3.4 SILICA CONTENT IN SOIL BY GRAVIMETRIC METHOD

Reagents:The following Reagents are used for the test.

i. Concentrated Hydrochloric acid (HCl).

Procedure

1. About one gram of the dried soil sample accurately weighed is taken in a 500

ml beaker.

2. About 10 ml of distilled water and 10 ml of concentrated hydrochloric acid

(HCl) is added to the beaker and is mixed and grounded with a glass rod to

dissolve.

3. The whole mass is allowed to evaporate to dryness by keeping it on a hotplate

till whole of the hydrochloric acid disappeared.

4. The residue is baked in oven for 01 hour and then allowed to cool.

5. Further 10 ml of distilled water and 10 ml of concentrated hydrochloric acid

(HCl) is added to it and is mixed with the help of glass rod till it dissolves.

6. The solution is then heated to boiling and after one minute it is removed from

flame and 20 ml of hot distilled water is added.

7. The solution is later filtered through Whatman filter paper no. 42 and the

whole of silica along with filter paper is placed in a preweighed crucible.

8. The crucible was placed in a Bunsun Burner for 25 minutes and ignited at a

temperature of 80 to 1000c.

9. The crucible is then removed from Bunsun Burner, it is then cooled and

weighed.


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10.The weight of the silica is calculated by subtracting the empty weight of the

crucible.

11. The passing of Whatman filter paper 42 i.e., filtrate is used for the calculation

of R2O3 (Al2O3+Fe2O3) by making the volume up to 100 ml in a 100 ml

Nesslers tube

Calculations

% silica oxide (SiO2) = (w3/w) x 100

Where, W3 = Weight of SiO2(in mgs)

W = Weight of soil sample taken (in mgs) (1 gm. = 1000 mgs)

3.5 IRON OXIDE (Fe2O3) IN SOIL BY COLORIMETRIC METHOD

Reagents:The following Reagents shall are used for the test.

i. Ammonium Chloride (NH4Cl).

ii. Potassium thiocyanate.

iii. Concentrated Hydrochloric acid.

Solutions

i. 5% Potassium thiocyanate

5 gms of Potassium thiocyanate is added into a 100 ml beaker and distilled

water is added to make 100 ml of solution

ii. 4N Hydrochloric acid (4N HCl)

For 1N of 1000 ml solution -- required 83 ml of concentrated HCl +

distilled water is added to make it 1000 ml of solution.

For 4N of 100 ml solution -- required 33.20 ml of concentrated HCl +

distilled water is added to make it 100 ml of solution.

Procedure

1. 50 ml of distilled water is added toNesslers tube of 100 ml capacity.

2. 5 ml of 5% potassium thiocyanate and 4 ml of 4N HCl are added and the

solution is made to 100 ml with distilled water.


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3. About 0.05 ml of filtrate is added to the nesslers tube of 100 ml solution to

get light red colour.

4. The Spectrometer is caliberated and set to method no. 900.

5. After calibration 10 ml sample is taken in a Cuvette and placed in

spectrometer. Readings are recorded as Fe in mg/lt for 5 mg of soil and Fe 2O3

is calculated for 100 mg of soil.

Calculations:

1000 mg of soil taken / 100 ml -------------- 0.05 ml / 100 ml

100 ml / 1000 mg -------------- 0.50 mg of soil / 100 ml

1 ml / 10 mg -------------- 5 mg of soil / 1000 ml (1Lt)

5 mg of soil ------------------------ -- mg / Lt Fe

100 mg of soil ---------------------- -- x 100 / 5 = X mg as Fe

For Fe2O3 multiplied by constant 1.4297

X x 1.4297 = Y % Fe2O3

3.6 R2O3(Al2O3+ Fe2O3) IN SOIL BY GRAVIMETRIC METHOD

Reagents:The following Reagents are used for the test.


ii. Rosolic acid solution (few drops) or Methyle red indicator (2 drops)

iii. Dilute ammonia --- add 50 ml Ammonia and make it to 100 ml with

distilled water.

Procedure

1. Half of the filtrate (50 ml from collected 100 ml in Nesslers tube) is taken for

estimation of R2O3(Al2O3+ Fe2O3) Aluminium and Iron oxide.

2. To the first 50 ml filtrate about 4 gms of ammonium chloride (NH4Cl) and two

drops of methyle red is added and heated to boiling and is removed from the

flame after one minute.


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3. Dilute ammonia is added to the solution until the precipitation starts and the

solution is filtered through Whatman no 42 filter paper.

4. The precipitates along with the filter paper is then placed in a weighed

crucible and the crucible is ignited in the Bunsun Burner or (Muffle furnace)

or any other suitable arrangements.

5. The final weight of the crucible is noted.

6. The total weight of (Al2O3+ Fe2O3) is obtained by subtracting from the final

weight, the weight of the empty crucible.

Calculations

% R2O3 = (w3/w) x100

Where, W3 = Weight of R2O3obtained (in mg)

W = Weight of soil sample taken (in mg) (0.50 gm = 500 mg)

3.7 CHLORIDE CONTENT IN SOIL BY ARGENTOMETRIC

METHOD

Reagents: The following Reagents are used for the test.

i. Silver nitrate (Ag No3)

ii. Potassium Chromate (5%)

Solutions

i. Standard Silver Nitrate solution (0.0141N)

2.395 gms of Silver Nitrate (AgNO3) is dissolved in distilled water and

diluted to 1000 ml.

ii. Potassium Chromate (5%)

5 gms (K2Cr O4) Potassium Chromate is dissolved in distilled water

.silver nitrateis added to the solution until a definite red precipitate is

formed and is allowed to stand for 12 hours. Then the solution is filtered

and diluted to 100 ml with distilled water.


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Procedure

1. 1:4 soil suspension is prepared i.e., 25 gms of soil is taken in 100 ml of aerated

distilled water and is shaked for about one hour.

2. The suspension is heated in a hot plate up to boiling and is removed from the

flame and allowed to cool down.

3. The suspension is then filtered through Whatman No. 50 filter paper using

Buchner funnel and vaccum pump.

4. Later 25 ml of soil solution is taken and 10 drops of Potassium Chromate (5%)

indicator is added till light yellow colour develops.

5. The sample is titrated using Standard Silver Nitrate Titrant (0.0141N) solution.

6. The volume of standard silver nitrate solution (0.0141N) in ml is recorded

when the colour changes from yellow to brick red colour.

3.8 CALCIUM AND MAGNESIUM OXIDE IN SOIL BY TITRIMETRIC

METHOD

Reagents: The following Reagents are used for the test.


ii. Glacial acetic acid.

iii. Concentrated Ammonium hydroxide (NH4OH).

iv. Magnesium salt of E.D.T.A.

v. Sodium hydroxide (NaOH)

vi. Murexide

vii. Ethylenediaminetetraacetate dehydrate (tetra acetic acid disodium salt

E.D.T.A)

Solutions

i. Ammonium Acetate solution

[57 ml of glacial acetic acid is diluted to 800 ml with distilled water &

then neutralized to pH 7.0 with concentrated Ammonium Hydroxide

(NH4OH) and the final volume is made to 1000 ml (1 ltr.).]


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[28.5 ml of glacial acetic acid is diluted to 400 ml with DW & then

neutralized to pH 7.0 with conc. NH4OH and the final volume is made to

500 ml]

ii. Buffer solution

For 250 ml Buffer solution

[16.90 gms ammonium chloride (NH4Cl) is dissolved in 143 ml of conc.

Ammonium hydroxide (NH4OH), 1.25 gm magnesium salt of EDTA is

added and diluted to 250 ml with distilled water.]

For 100 ml Buffer solution

[6.76 gms ammonium chloride (NH4Cl) is dissolved in 57.20 ml of conc.

Ammonium hydroxide (NH4OH), and 0.50 gm magnesium salt of EDTA

is added and diluted to 100 ml distilled water]

iii. Standard EDTA titrant ( 0.01M)

For 1000 ml titrant,3.723 gms analytical reagent-grade disodium EDTA

dehydrate is weighed, also called (ethylenedimitrilo) tetraacetic acid

disodium salt (EDTA) and dissolved in distilled water and diluted to 1000

ml.

For 500 ml titrant, 1.8615 gm analytical reagent-grade disodium EDTA

dehydrate is weighed , also called (ethylenedimitrilo) tetraacetic acid

disodium salt (EDTA) and dissolved in distilled water and diluted to 500

ml.

iv. Erichrome Black T indicator

Sodium salt of 1- (1-hydroxy -2 napthylazo) -5-nitro-2-naphthol-4

sulfonic acid: no 203 in the colorindex. 0.50 gm dye is dissolved in 100gof triethanolamine or ethylene glycol monomethyl ether. 2 drops per 50 ml

solution is added for titration.

v. Sodium hydroxide solution (1N)

4 gms of sodium hydroxide pallets is dissolved in 100 ml of distilled water

vi. Murexide


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Procedure for the estimation magnesium oxide

1. About 50 gms of the dried sample accurately weighed is taken in a 500 ml

beaker and about 100 ml of Ammonium acetate solution is added.

2. The suspension is stirred and kept overnight and later the water sample is

collected from the solution.

3. Concentration of magnesium oxide is determined following the EDTA

method.

4. 100 ml of sample from solution is taken in a conical flask and 1 ml of Buffer

solution and 3 drops of Erichrome Black T indicator is added to get light

yellow colour.

5. The sample is titrated using EDTA titrant.

6. Volume of EDTA solution is recorded when colour changes from light yellow

to light pink or green or blue.

7. Measure the concentration Magnesium oxide.

Procedure for Estimation of Calcium oxide

1. About 50 gms of the dried sample accurately weighed is taken in a 500 ml

beaker and 100 ml of Ammonium acetate solution is added directly to it.

2. The suspension is stirred and kept overnight and later the water sample is

collected from the solution.

3. The concentration of calcium oxide is determined following the EDTA

method.

4. 100 ml of sample is taken from the solution in a conical flask and 2 ml of

Sodium hydroxide solution and 1 pinch Murexide is added and sample

changes to light yellow colour.

5. The sample is titrated using EDTA titrant.

6. Volume of EDTA solution is recorded when colour changes from light yellow

to light pink or green or blue.

7. Measure the concentration of Calcium oxide.


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3.9CHEMICAL ANALYSIS RESULTS ON UNTREATED AND

TREATED BC SOIL

Table 3.1 shows the chemical composition of untreated and treated BC soil. It can

be observed that there is an increase in SiO2, CaO content and pH value and

decrease in Fe2O3, MgO, chloride and sulphate content in treated soil when

compared with untreated soil. Since a clear trend is not observed, the changes in

composition of soil before and after treating with Terrabind and FA cannot be

explained clearly.

Table 3.1: Chemical composition of untreated and treated BC soil

Oxides (%) BC BC+Terrabind BC+Terrabind+FA

SiO2 57.12 58.29 58.89

R2O3 14.13 12.45 10.22

Fe2O3 6.08 2.71 2.18

Al2O3 8.05 9.75 8.04

Chloride 0.085 0.11 0.17

Sulphate 0.091 0.025 0.052

CaO 0.0045 0.012 0.016

MgO 0.013 0.017 0.015

pH

8.22 8.5 8.43

Conductivity(millisiemens/cm) 1.17 1.16 1.22

TDS(PPm) 188 186 187

LOI 14.67 - -


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CHAPTER 4

MATERIALS AND METHODOLOGY

4.1 GENERAL

This chapter deals with details of experimental investigation carried out on Black

cotton soil. Experiments are conducted to determine the geotechnical and engineering

properties of the soil. All the tests are performed as per the relevant codes. Changes in

their properties are studied by blending the soil sample with Terrabind chemical and

FA.

4.2 MATERIALS USED

4.2.1 Soil

Black cotton soil which is abundantly available in Gadag district (North Karnataka) is

used for the investigation. The soil sample is obtained from a depth of 2 meter below

the ground surface. The collected sample is first air dried and then oven dried beforeusing it for the tests.

Figure 4.1: Black cotton soil


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4.3 TESTS CONDUCTED ON SOIL

Soil samples collected from site are tested for their geotechnical properties andstrength characteristics. The various tests conducted are given below.

1. Specific gravity test

2. Grain size analysis test

3. Atterbergs limits tests

4. Compaction tests

5. Unconfined compressive strength test

6. California Bearing Ratio test

7. Triaxial compression test

8. Free swell index

9. Swell pressure

10.Durability test

11.Fatigue test

4.3.1 Specific Gravity test

Specific gravity test is performed on untreated soil using Standard test equipment and

procedure available as per IS: 2720 (part 3)-1980, Determination of specific gravity

of fine grained soils. Three trials are conducted and the average value is reported.

The test results are depicted in Table 5.1.

4.3.2 Grain size analysis test

Sieve analysis and sedimentation analysis tests are conducted on untreated soil to

determine the grain size distribution. The sedimentation analysis is done by

hydrometer method using sodium hexa metaphosphate as the dispersing agent. The

test is conducted as per IS 2720 (part4) 1985. The results are tabulated in Table 5.1.

4.3.3 Consistency limits test

Liquid limit (LL) and plastic limit (PL) of the soil are determined as per the

procedure available in IS: 2720 (part 5)-1985. The tests are conducted on treated and

untreated soil. Treated soils are tested at different curing periods. Standard


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Casagrandes apparatus is used to find out LL. The consistency limits of untreated soil

samples are tabulated in Table: 5.1.

Figure 4.2: Casagrande apparatus for determination of liquid limit.

Figure 4.3: Samples prepared for the determination of plastic limit.

4.3.4 Compaction tests

Compaction test is conducted to determine the maximum dry density and optimum

moisture content of treated and untreated soil using Standard test equipment and

procedure available in IS: 2720 (part 7)-1980,Determination of water content Dry

density Relation using Light compaction for light compaction and IS: 2720 (part 8)-


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Whereas, treated soil is tested only for heavy compaction density for soaked and

unsoaked condition. Results of tests on untreated soil smaple are tabulated in Table

5.1.

Figure 4.5: Determination of CBR

4.3.7 Triaxial compression test

Tri axial compression test is performed to determine the shear strength parameters (C

and ) of soil at consolidated undrained condition for treated and untreated soil

specimens. The tests are conducted using standard equipments and procedure

available as per IS: 2720 (Part 11)-1971, Determination of shear parameters by

triaxial test.


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Figure 4.6: Triaxial compression testing setup

4.3.8 Free swell index

The free swell index test is conducted to determine the amount of swelling in treated

and untreated soil. The procedure followed is as per IS: 2720 (part-10)-1977. The

procedure involves in taking two oven dried soil samples (passing through 425 IS

sieve), 10g each which are placed separately in two 100ml graduated soil sample.

Water is filled in one cylinder and kerosene (non-polar liquid) in the other cylinder up

to 100ml mark. The final volume of soil is read after 24hours to calculate free swell

index.

The free swell index of the soil shall be calculated as follows:

Free swell index, percent = ((Vd-Vk)/Vk)*100

Where, Vd= the volume of soil specimen read from the graduated cylinder containing

distilled water, and Vk= the volume of soil specimen read from the graduated cylinder

containing kerosene.


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Figure 4.7: Free swell index setup

4.3.9 Swell pressure

Swell pressure of treated and untreated soil is determined using swell pressure

apparatus.the test is conducted as per IS: 2720(part 11)-1977. The swell test apparatus

is designed to determine the swelling pressure developed by expansive soil specimens

moulded to desired densities at known moisture contents when soaked in water. The

load applied to restrain the change in volume caused by the expansive nature of the

soil, on coming into contact with water, is transferred to a load measuring proving

ring through a perforated swell plate and a load transfer bar. The maximum load

indicated on the proving ring in kilograms divided by the area of the specimen gives

the swelling pressure in kg/cm2. Both treated and untreated soil is tested to determine

its swell pressure. Treated soils are tested after 7 and 28 days of curing.

4.3.10 Durability

Durability can be defined as the ability of a material to retain its stability and integrity

over years of exposure to the destructive forces of weathering. Durability of stabilized


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soil is essential in defining the final mixture because it serves as an indicator of its

resistance to the destructive forces of environment.

Wet and dry cycle: The durability test for wet and dry cycle is performed in

accordance with ASTM D559 (ASTM 1994). Briefly, this test consisted of exposing

the soilcement specimens to 12 cycles and each cycle consisted of wetting the

specimen by submerging it in water at room temperature (25 +1.5C) for 5 h after

moist curing at 21 + 1.7C and 100% humidity, and drying for 42 h at a temperature

of 71C. The specimens are brushed parallel, weighed and measured after each cycle

to obtain soil cement losses, moisture changes and volume changes (swelling and

shrinkage). After the 12 cycles, specimens are dried to a constant weight at a

temperature of 110C and weighed to determine the oven-dry weight of the

specimens. The data are used to calculate the volume and moisture changes of the soil

specimens.

Freeze and thaw cycle: Durability test procedure for freeze and thaw is followed

according to S. A. Shihata and Z. A. Baghdadi (2001). Triplicate sets of samples of

compacted chemical treated soil are prepared and tested for its durability using, in

which, after the 7 days of curing, the specimens are placed in water-saturated felt pads

and stood on carriers in a freezer at a temperature not higher than -10C for 22 h. On

removal, the specimens are kept in a moisture room for 22 h. After that the specimens

are weighed. This procedure is repeated until the specimens have gone through 12

cycles of freezing and thawing. Then the specimens are dried at 110C for 48 hours

and their final weight is taken. This test gives the percent mass loss of samples after

12 wet-dry or freeze-thaw cycles.


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Figure 4.8: Samples prepared for freeze-thaw & wet-dry cycle test

Figure 4.9: Samples prepared for freeze-thaw and wet-dry cycle test

4.3.11 Fatigue test

Fatigue life is the number of load cycles corresponding to the failure of the specimen

under repeated loading or number of loading. To investigate fatigue behavior of

terrabind stabilized soils, specimens are exposed to the repeated loading in the

laboratory. For this purpose the laboratory experiments are conducted in a fatigue

testing apparatus and the specimens are subjected to number of repeated loads. The


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number of loading cycles varied depending upon curing period, amount of load etc.

This section describes the methodology adopted for this purpose.

a) Specimen Preparation and curing

The type of specimen tested for fatigue capacity of the Terrabind stabilized specimen

is similar to the one tested for their unconfined compression test. A cylindrical

specimen of length to diameter ratio of 2 is used and the treated soil samples are

tested for 7 and 28 days curing.

The Fatigue test equipment that is capable of applying the repeated loads at a

frequency 0 to 12 Hz is used in the present investigation. The equipment is procured

from SPANTROICS, Bangalore.

The main components of the test set-up are:

I. Loading system including loading frame and load sensing device

nit surathkal terrabind review

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