Final Report WORK - Send 2(2)

8/4/2019 Final Report WORK - Send 2(2)

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USE OF FLY ASH AS AN ALTERNATIVE LANDFILL LINER

MATERIAL

Submitted in partial fulfillment of the requirements for the degree of

MASTER OF TECHNOLOGYIn

GEOTECHNICAL ENGINEERING

By

Soumyadip Chowdhury

Under the guidance of

Dr. Anil Kumar Mishra

Department of Civil Engineering

INDIAN INSTITUTE OF TECHNOLOGY GUWAHATI

Guwahati 781039, India

July 2011


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Certificate

This is to certify that the project work entitled Use of Fly ash as an Alternative Liner

Materialbeing submitted by Mr. Soumyadip Chowdhury(Roll No. 09410441), for the partial

fulfillment of the requirement for the award of Master of Technology is a record of bonafide

work carried out under my supervision. The content of this project work has not been submitted

to any other institute or university for award of any degree.

Dr. Anil Kumar Mishra

Assistant ProfessorDepartment of Civil Engineering

Indian Institute of Technology, Guwahati


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Acknowledgement

I would like to express my sincere gratitude and hearty thanks to my advisor Dr. Anil Kumar

Mishra for his guidance, encouragement and gracious support throughout my work. His vast

knowledge and expertise in soils has motivated me to do my best and for that, I am forever

grateful. And his support at every stage proved very much helpful in successful completion of

this work.

My thanks are due to all faculty members, laboratory staff of civil engineering especially Mr.

Upadhay who has helped me a lot for doing experiments in the laboratory.

I am also thankful to all my friends for their kind co-operation and specially, Mr Srikant

Vadlamudi, Mr Pawan Kumar Shah, Mr Pravudatta Pradhan and Mr Amol Shivdas. Without

their charming company, my small endeavor could not have been so pleasurable.

I am indebted a lot to my parents for their whole hearted moral support and constant

encouragement towards the fulfillment of the degree and throughout my life. Above all, its the

most gracious and the most merciful Almighty God for his help to enable me to complete this

research work.

Soumyadip Chowdhury


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Abstract

Landfill liners are used for the efficient containment of waste materials generated from different

sources. In the absence of impermeable natural soils, compacted mixtures of expansive soil and

sand have found wide applications as landfill liners. It is to be noted that, in case, these materials

are not locally available, the cost of the project increases manifold due to its import from

elsewhere. Also, sand has become an expensive construction material due to its limited

availability. With this in view, the present study attempts to explore a waste material such as fly

ash as a substitute for sand. The major objective of this study is to maximize the use of fly ash

for the said application. Different criteria for evaluating the suitability of material for landfill

liner have been studied in this study. However, further investigations are required with different

source of fly ash and alternative material to generalize the findings.

Keywords: Landfill liner, Design criteria, Fly ash, Cement, Bentonite, Hydraulic conductivity,Compressibility


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TABLE OF CONTENTSPage No.

CERTIFICATE 2ACKNOWLEDGEMENT 3

ABSTRACT 4

CONTENT 5

LIST OF FIGURES 7

LIST OF TABLES 8

Chapter-1: Introduction 9

1.1.1. Prevention and Reduction 9

1.1.2. Recycling 9

1.1.3. Composting 10

1.1.4. Sanitary Landfilling 11

1.2. Containment System 12

Chapter-2 14

2.1. Types of Liner 14

2.1.1. Single Liner 14

2.1.2. Single Composite 15

2.1.3. Double Liner 15

2.1.4. Double Composite Liner 15

2.2. Design Criteria for Landfill Liner 16

2.2.1. Standard Design 17

2.2.1. Alternative Design 17

2.2.3. Equivalent Design 18


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2.2.4. Arid Design 18

2.3. Selection of Liner Material 18

2.4. Type of Landfill Liner Material 20

2.4.1. Bentonite Liner 20

2.4.2. Asphalt Liner 20

2.4.3. Soil Asphalt Liner 21

2.4.4 Soil Cement Liner 22

2.4.4.1. Dry Mix Soil Cement 23

2.4.4.2. Plastic Soil Cement Mix 23

2.5. Necessity for the Requirement of a Alternative Liner Material 24

Chapter-3 28

3.1. Materials 28

3.2. Method 28

3.2.1. Consolidation Test 28

3.3. Determination of hydraulic conductivity and compressibility 31

Chapter-4 33

4.1 General 33

4.1.1. Compaction properties of the mixtures 33

4.1.2. Hydraulic Conductivity 34

4.1.3. Compressibility 35

4.1.4. Co-efficient of consolidation 38

4.2. Scope of future Work 38

5.0. References 39-40


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LIST OF FIGURES

Fig. No. Name Page No.

Fig.1. Cross section of different liner system 11

Fig. 2. Acceptable water content and dry density for compacted soil 13

Fig.3. Relation between void ratio and hydraulic conductivity for the 34

three mixtures

Fig.4. Relation between void ratio and over burden pressure for the three 36

mixtures

Fig.5. Relation between pressure and co-efficient of compressibility 37

Fig.6. Relation between coefficient of consolidation and over burden 39

pressure for the three mixtures


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LIST OF TABLE

Table No. Name Page No.

Table 1. Past research and Result 26-27

Table 2. OMC and MDD values of fly ash- cement mix with 33

different proportion

Table 3. Values of compression index and expansion index 31

Table 4. Classification of Potential Expansion of Soils Using EI 38


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Chapter-1

1.1 INTRODUCTION

The high population and rapid industrialization in the last few decades have led to the generation

of huge quantities of hazardous wastes, which have further aggravated the environmental

problems in the country by depleting and polluting natural resources. Therefore, rational and

sustainable utilization of natural resources and its protection from toxic releases is vital for

sustainable socio-economic development. Indias garbage generation stands at 0.2 to 0.6

kilograms of garbage per head per day. Also, it is a well known fact that land in India is scarce.

There are several methods of treatment and disposal of solid waste-

1.1.1. Prevention and Reduction:

The best method of managing waste is prevention and reduction, which can be achieved in a

number of ways like recycling and making use of second-hand items.

1.1.2. Recycling:

Recycling involves processing used materials (waste) into new products to prevent waste of

potentially useful materials, reduce the consumption of fresh raw materials, reduce energy usage,

reduce air pollution (from incineration) and water pollution (from land filling) by reducing the

need for "conventional" waste disposal, and lower greenhouse gas emissions as compared to

virgin production. Recycling is a key component of modern waste reduction and is the third

component of the "Reduce, Reuse, and Recycle" waste hierarchy. Recyclable materials include

many kinds of glass, paper, metal, plastic, textiles, and electronics. Although similar in effect,

the composting or other reuse of biodegradable waste such as food or garden waste is not

typically considered recycling. Materials to be recycled are either brought to a collection center

or picked up from the curbside, then sorted, cleaned, and reprocessed into new materials bound


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for manufacturing. In a strict sense, recycling of a material would produce a fresh supply of the

same material, for example; used office paper would be converted into new office paper, or used

foamed polystyrene into new polystyrene. However, this is often difficult or too expensive

(compared with producing the same product from raw materials or other sources), so "recycling"

of many products or materials involve their reuse in producing different materials (e.g.,

paperboard) instead. Another form of recycling is the salvage of certain materials from complex

products, either due to their intrinsic value (e.g., lead from car batteries, or gold from computer

components), or due to their hazardous nature (e.g., removal and reuse of mercury from various

items).Some disadvantages are-

a) It is a very expensive procedure.b) Some waste cannot be recycled.c) Technological know-how is very essential for this process.d) Separation of useful material from waste is very difficult job.

1.1.3. Composting:

Compost is composed of organic materials derived from plant and animal matter that has been

decomposed largely through aerobic decomposition. Organic matter constitutes 35%-40% of the

municipal solid waste generated in India. This waste can be recycled by the method of

composting. The process of composting is simple and practiced by individuals in their homes,

farmers on their land, and industrially by cities and factories. The compost itself is beneficial for

the land in many ways, including as a soil conditioner, a fertilizer, addition of vital humus or

humic acids, and as a natural pesticide for soil. In ecosystems, compost is useful for erosion

control, land and stream reclamation, wetland construction, and as landfill cover. The process

occurs naturally and is a critical component to soil health. After plants and animals die, bacteria


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go to work decomposing the remains. Once the decay process is complete, the original matter is

no longer recognizable and a rich, dark, soil-like substance remains. The living organisms

involved in the decay process thrive in an environment of the right combination of air, water,

nitrogen, and carbon. The better the conditions, the faster the compost process. Composting of

organic materials from the solid waste stream not only provides a valuable benefit to nutrient

deficient soils, but also reduces the amount of waste that ends up in landfills or incinerators.

Other benefits of composting organic matter include the increase in beneficial soil organisms

such as worms and centipedes, suppression of certain plant diseases, the reduced need for

fertilizers and pesticides, prevention of soil erosion and nutrient run-off, and assistance in land

reclamation projects. Material resulting from the composting of bio-solids and yard waste is used

primarily as an organic soil conditioner and partial fertilizer. It is applied to agricultural lands,

recreational areas such as parks and golf courses, mined lands, highway medians, cemeteries,

home lawns and gardens.

1.1.4. Sanitary Land filling:

The term "sanitary landfill" was first used in the 1930s to refer to the compacting of solid waste

materials. Initially adopted by New York City and Fresno, California, the sanitary landfill used

heavy earth-moving equipment to compress waste materials and then cover them with soil. The

practice of covering solid waste was evident in Greek civilization over 2,000 years ago, but the

Greeks did it without compacting. Sanitary landfills involve well-designed engineering methods

to protect the environment from contamination by solid or liquid wastes. A necessary condition

in designing a sanitary landfill is the availability of vacant land that is accessible to the

community being served and has the capacity to handle several years of waste material. In

addition, cover soil must be available. Today, the sanitary landfill is the major method of


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disposing waste materials in India and other developed countries, even though considerable

efforts are being made to find alternative methods, such as recycling, incineration, and

composting. Among the reasons that landfills remain a popular alternative are their simplicity

and versatility. For example, they are not sensitive to the shape, size, or weight of a particular

waste material. Since they are constructed of soil, they are rarely affected by the chemical

composition of a particular waste component or by any collective incompatibility of co-mingled

wastes. By comparison, composting and incineration require uniformity in the form and chemical

properties of the waste for efficient operation.

Out of all these methods, sanitary land filling is generally used for the waste disposal.

1.2. CONTAINMENT SYSTEM

The design of sanitary land filling typically involves some form of barrier that separates the

waste from the general ground water system. This barrier is intended to minimize the migration

of contaminants from the facility, thus the environmental impact of the facility is intimately

related to its design and long term performance. Natural clayey deposits or compacted clayey

liners frequently represent a key component of these barriers.

These days, barriers are usually includes one or more of the following types:

(i) Natural clayey soils such as lacustrine clay or clayey till;

(ii) Compacted clayey liners;

(iii) Cut-off walls;

(iv) Natural bedrock;

(v) Composite liner system consisting of geomembranes.

Out of the above mentioned types generally compacted clayey liners and composite liner system

with geomembranes are used on the waste disposal site.


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Compacted clay liners have been the subject of debate with respect to both the hydraulic

conductivity which can be achieved in the field and the potential impact of soil-leachate

interaction on hydraulic conductivity. However, the experienced has shown that with good

engineering practice and quality control, good quality, low hydraulic conductivity liners can be

constructed. Compacted clay liner can be designed with or without a leachate collection system.

The liner may be required for one or two reasons. Firstly, if the natural soil is fractured clayey

soil then the liner may be required to retard movements of contaminant along the fractures. The

second reason for constructing a clay liner is that, while intact, the surroundings natural soil does

not have a low enough hydraulic conductivity to provide an adequate barrier. There are some

situations where the conceptual designs may not provide sufficient confidence that there will be

negligible effect on ground water quality. Under these circumstances, an additional level of

engineering in the form of a secondary leachate collection system or hydraulic control layer may

be provided.


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Chapter-2

2.1. TYPES OF LINER

The different types of architecture used for landfill liners are as follows: single liner (clay or

geomembrane), single composite (with or without leak control), double liner, and double

composite liner.

2.1.1. Single Liner

A single liner system includes only one liner, which can be either a natural material (usually

clay), Figure 1a, or a single geomembrane, Figure 1b. This configuration is the simplest, but

there is no safety guarantee against the leakage, so a single liner may be used only under

completely safe hydro geological situations.

Figure 1. Cross section of different liner system


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A leachate collection system, termed as LCS (soil or geosynthetic drainage material), may be

placed above the liner to collect the leachate and thus decrease the risk of leakage.

2.1.2. Single Composite

A single composite liner system, Figure 1c, includes two or more different low-permeability

materials in direct contact with each other. Clayey soil with a geomembrane is the most widely

recommended liner.

Geotextile - Bentonite composites are often used as substitutes for mineral liners (liners using

stones or rocks as material) for application along slopes, even though many engineers prefer clay.

One of the main advantages of composite liners over single liners is the low amount of leakage

through the liner, even in the presence of damage, such as holes in the geomembrane.

2.1.3. Double Liner

A double liner system, Fig 1d, is composed of two liners, separated by a drainage layer called the

leakage detection system. A collection system may also be placed above the top liner. Double

liner systems may include either single or composite liners. Nowadays, regulations in several

states require double liner systems for MSW landfills. A clay layer may be placed under a double

liner made of membranes as shown in Figure 1e.

2.1.4. Double Composite Liner

Double composite liners are systems made of two composite liners, placed one above the other,

Fig 1f. They can include a LCS above the top liner and an LDS between the liners. Obviously,

the more components in the liner system, the more efficient is the system against leakage.

2.2. DESIGN CRITERIA FOR LAND FILL LINER

Solid waste land fill liners are design to prevent the movement of potentially harmful pollutants

beyond the boundaries of the landfill. The design criteria of a soil liners involves many facets


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such as selection of proper material, assessment of its chemical compatibility, analysis of slope

stability, consideration of the cracking due to desiccation of the material etc. Most of the

environmental agency requires a hydraulic conductivity value of less than 10-7

cm/sec for the

clay liners used to contain hazardous, industrial and municipal solid waste. Since the hydraulic

conductivity of a compacted soil depends upon its initial dry density and compaction water

content (Lambe, 1953), the field compaction conditions for a soil liner is generally taken into

account for verifying the proper compaction of the soil. In order to achieve this, the soil liner is

required to be compacted within a specified range of water content and a given dry density.

Figure 2. Acceptable water content and dry density for compacted soil

An acceptable zone which represents the combination of the zone of acceptable water content

and dry density is required for practice. The soil is generally required to be compacted at a

percentage P of the dry density and w of optimum moisture content. Previous research had


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shown that the value of P is usually 95% of dry density and w is 5% wet of optimum water

content.

There are four types of liner design-

2.2.1. Standard Design

In case of standard design we need minimum 4 ft. thick layer of re-compactedclay or other material with permeability of less than 10

-7cm/sec.

Finished liner must be sloped at 2%. This method is not suitable where large quantity of liner material is not easily

available on site or nearby site.

2.2.2. Alternative Design

This is the most desirable liner system because of the reduced permeability and thickness

requirement. It is feasible for areas with no available silt or clay material. The added cost

of synthetic liner is often out-weighted by cost reduction in clay material.

Alternative design provides a liner which consists of two liners. The thickness ofupper liner should be 50 mm and for lower liner 2 ft.

Upper liner should be made of synthetic material and lower liner of compactedclay. The hydraulic conductivity (k) of lower liner should be 10-6 cm/sec

The finish layer should be sloped at 2%2.2.3. Equivalent Design

Equivalent design is consist of some specific criteria like double liner and very deep natural

deposits of material with higher permeability than the standard case. It should be approved and

justify for the situation of the particular site.


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2.2.4. Arid Design

In that case liners are not required in arid areas like Rajasthan. In those places annual rainfall is


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operating life of landfill (i.e. construction purpose) and of liner after closer of the landfill. Soil

properties of nearby side are needed to be investigated. Hydrology and hydro-geology of the land

fill construction site is very helpful information for design of the landfill liner. Permeability and

different environment factor is very important for success of the landfill. Reliability of materials

such as seams and joint of geosynthetic membrane or material is very important. The following

items are some of the criteria that should be considered during the initial selection stage:

The selected site should be conformed to land use planning of the area. The selected site should have easy access to vehicles during the operation of the landfill. The site area should have adequate quantity of earth cover material that is easily handled

and compacted.

Landfill operation will not detrimentally impact surrounding environment. The selected site should be large enough to hold community waste for a reasonable length

of time.

2.4. TYPE OF LANDFILL LINER MATERIAL

Now a days several materials is being used for landfill liner material. Some of this is discussed

below;

2.4.1. Bentonite-Soil Liner

Bentonites and bentonite containing sealing materials are used for many years for sealing

purposes in foundation, dike construction, hydraulic engineering and landfill construction,

especially for encapsulation of old waste deposits. Because of their exceptional physical,

structural and chemical properties, bentonites are offering manifold possibilities to protect the

environment against the negative effects of dumping grounds. Often the observance of legal

regulations for waste dumping or for the encapsulation of contaminated areas is possible only by


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using bentonite containing sealing systems. Sodium Bentonite is easily available in powder form

that can be mixed with soil. Bentonite soil liner typically used in lifts 4 to 6 inches thick. For

Bentonite soil liner Plasticity Index (PI) should be greater than 15% and percentage finer should

be greater than 30%. For horizontal technical base liners the adsorption ability, the ion exchange

capacity and the swelling behavior of bentonite is important. For cut-off walls bentonite controls

the rheological behavior of the slurry and is responsible for the low permeability of the hardened

bentonite-cement-wall.

2.4.2. Asphalt Liner

The asphalt landfill liner has a number of advantages, the most important of which is increased

environmental safety. The asphalt liner can have a hydraulic conductivity that is 100 to 1,000

times lower than traditional compacted soil liners. Hydraulic conductivity describes how a liquid

flows through a material, and is important when preventing leakage from landfills. Landfills with

traditional soil liners may have a flow rate of about 140 gallons per acre per day. With asphalt

alone, the flow rate decreases to about nine gallons per acre per day. After completing the liner

with a layer of sprayed asphalt and a geosynthetic fabric on top, the flow is almost immeasurable.

Another environmental safety advantage of the asphalt liner is that it is more flexible and pliable

than traditional soil liners. This allows it to handle deformations without cracking, which

sometime happens with traditional soil liners. In addition, the layer of sprayed asphalt on the

liner's surface has the ability to seal itself against punctures, a feature traditional plastic

membranes do not possess. Asphalt liner is used as a mix which is known as Hydraulic Asphalt

concrete (HAC). HAC is a control hot mix of asphalt and a high quality mineral aggregate that is

compacted into a dense layer in order to achieve max permeability


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Asphalt landfill liners also take up less space. Traditional soil liners are more than two feet thick,

but asphalt liners are between four and six inches thick. Because the liner takes up less space, the

landfill can hold more trash. . Landfills that hold petroleum wastes, hydrocarbon wastes or

organic solvents could not use asphalt because these wastes could degrade the liner. He added

that installation costs are comparable between asphalt and traditional liners.

2.4.3. Soil Asphalt Liner

Asphalt is a dark brown to black cementious material, solid or semisolid in consistency, in which

the predominating constituents are bitumens (i.e., high molecular-weight hydrocarbons) that

occur in nature as such or are obtained as residual in the refining process (Yen, 1990).

Incorporation of affected soil as an ingredient to produce an asphaltic product is achieved by

stabilization, solidification and encapsulation. Stabilization is where chemical fixation

techniques render a waste less toxic or harmful to the environment. The hazard potential of what

was once considered a waste is subsequently reduced. Generally soil asphalt liner is mix of a

liquid asphalt and an aggregate of poorer quality than HAC. Typically the preferred soil type is

silty, generally soil with 10%-25% fines. In the areas of temperature variation asphalt liner is not

good.

2.4.4. Soil Cement Liner

Soil-cement linings are constructed with mixtures of sandy soil, cement and water, which harden

to a concrete-like material. The cement content should be from 2-8% of the soil by volume.

Permeability of mix can be achieved up to 10-6

cm/sec by compaction. However, larger cement

contents are used. For the construction of soil-cement linings two methods are in general use: (1)

the dry-mix method and (2) the plastic mix method. For erosion protection and additional

strength in large channels, the layer of soil-cement is sometimes covered with coarse soil. It is


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recommended the soil-cement lining should be protected from the weather for seven days by

spreading approximately 50mm of soil, straw or hessian bags over it and keeping the cover

moistened to allow proper curing. Water sprinkling should continue for 28 days following

installation. Soil-cement linings are often a viable alternative to channel lining if locally

available materials are not suitable for compressed earth or clay earthen lining. A great

advantage of this technique is that practically all types of soil normally encountered in earthen

channels can be used. For lining the beds of large channels this type of lining is considered ideal

from its combination of cost, efficiency and adequate results.

2.4.4.1. Dry-Mix Soil-Cement

The cement is distributed by hand-raking or by mechanical cement spreaders to a uniform depth.

While the cement is being mixed into the soil with a rotary tiller, water is added simultaneously

to the mixture from a tank truck or hose. After the cement and soil are thoroughly mixed and the

moisture content determined to be proper, the mixture is compacted by rubber-tyred road

compactors or heavily loaded trucks to approximately 100 mm thickness, within one hour of the

cement being spread. The soil mixture is usually cured for several days with intermittent

sprinkling. The durability and water tightness of the dry-mix soil-cement lining depends on the

soil used. Tests indicate that for ease of mixing, placement and using a low cement content, the

soil should be a well-graded, sandy, gravelly material. If it is poorly graded then the cement

content required is higher and cost increases. Material mixing for standard soil-cement is best

accomplished by travelling mixing machines or stationary plants. Mixing in place in the channel

and on side slopes has been found to be satisfactory.


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2.4.4.2. Plastic Soil-Cement Mix

Plastic soil-cement has higher water and cement content than dry-mix and a consistency

comparable to that of concrete used for slip-form lining. The soil is mixed with cement and water

in a paver or mixer traveling along the channel or in a stationary plant. The mix is then poured by

hand or by slip form on the sub-grade to produce the lining. Thickness ranges from 75-150 mm.

It is recommended that joints similar to those of concrete linings be provided. Installations of

soil-cement linings in the United States have shown that the greater the cement content of the

plastic mixture, the more durable the liner. All of the linings installed continue to be effective at

reducing both seepage and erosion. The sections with higher cement contents were made

serviceable for many years with reasonable maintenance.

2.5. NECESSITY FOR THE REQUIREMENT OF AN ALTERNATE LINERMATERIAL

The reviewed literature highlights that the liner is the most important element of a waste disposal

landfill that minimizes the migration of harmful contaminants to groundwater. Several

researchers have proposed different criteria for the design of different type of liners. In terms of

design there are two important factors: (1) thickness of the liner and (2) the mix design of soil

used in the liner. It is observed that the most significant factor affecting the performance of liner

is hydraulic conductivity and hence there is universally accepted guideline for minimum

hydraulic conductivity for liners. Hydraulic conductivity is found to depend on various factors

such as soil mix, water content, type of cement, dry density, degree of saturation, desiccation and

freezing. Some studies also report that hydraulic conductivity depends on the lift thickness, type

and weight of roller, number of passes and coverage and also the size of the clods. Several

empirical relationships and predictive correlations have been proposed for determining optimum


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water content, dry density and hydraulic conductivity of the soil based on easily measurable soil

properties.

In particular, hydraulic conductivity, compressibility and strength of the liners are crucial for

construction of the liners. However, no definite guidelines have been laid down for liner design

in terms of compressibility and strength. Also, no guideline exists to account chemical

interaction of liner-contaminant, which also plays a very important role in contaminant

migration. It is believed that this factor would help to reduce the thickness of the liners and

thereby make the project cost-effective.

There are different studies that deal with the use of variety of soil-admixture combinations for

liner construction. The details of all these studies and their result have been tabulated in Table 1.

From these studies it is found that one such material is fly ash which has a high utility potential

in these geo-environmental projects. Past and recent research has established the potential of fly

ash for use in a variety of construction applications. However, its utility in geo-environmental

projects still need to be explored in detail. To enhance its utility, the various criteria for liner

design need to be defined for fly ash type of materials. There are not many studies that deal with

the characterization of fly ash-cement mix that can be used for liners. Most of the studies deal

with strength and compressibility of the mix. The reviewed literature clearly suggest that a lot of

systematic studies are still required in terms of physical, chemical and geotechnical

characterization of fly ash-soil mix so that its mass utility can be enhanced in geo-environmental

projects like landfills.

The aim of this current research is it to evaluate the effective use of the mixtures fly ash and

cement as the liner material.


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Table 1. Past research and result

Sn Title Author Materials used

Hydrauli

conductivi

(cm/sec)

1 Feasibility of mudstone material as anatural landfill liner

Sheu et al.(1998) Mudstone material.


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Sn Title Author Materials used Hydraulicconductivity

(cm/sec)

10 Liners for waste containment

constructed with class F and C fly

ashes

Palmer et al. (1999) Class F and Class C fly

ash.

11 Stabilised fly ash use as lowpermeability barriers

Bowders et al. (1987) Class F fly ash, lime orcement

7.2x10-6

12 Permeability and leachate

characteristics of stabilized class F

fly ash.

Bowders et al. (1990) Class F fly ash,

bentonite, cement or

lime

Addition of

bentonite did

not affect k.

Permeation with 5%methanol with lime and

lime bentonite.

Decrease inhydraulic

conductivity.

Permeatition with 5%methanol.with cement

and cement bentonite

Increase in k.

Permeation with 3.2%

acetic acid solutionwith all specimen

except with 10%bentonite

Lowered thek.

13 Permeability and leaching

characteristics of fly ash liner

material.

Creek and Shackelford

(1992)

Class F fly ash, sand,

bentonite and cement.

1.2x10-4 to

4.5x10-7

14 Constant flow and constant

gradient permeability on sand-bentonite-fly ash mixtures.

Shakelford and Glade

(1992)

Sand bentonite fly ash

mixture

kupto

bentonitecontent up to

18% and

increasedlater.

15 Permeability of fly ash and alyash-sand mixtures

Vesperman et al.(1985)

Fly ash with sand (0 to90 %)


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Chapter-3

3.1. MATERIALS

In the first phase of this project was pure fly ash used. The specific gravity of the fly ash is 2.04.

To improve the hydraulic conductivity of the liner 43 grade Ordinary Portland cement with pure

fly ash was used. In order to study the effect of the cement content on the linear shrinkage,

hydraulic and compressibility behavior of the mixtures, tests were carried out for the five

different mixtures, i.e. 100 % fly ash, 98 % fly ash + 2 % cement, 95 % fly ash + 5 % cement,

93 % fly ash + 7 % cement and 90 % fly ash and 10 % cement. In order to get better idea,

mixture of fly ash and bentonite was also in the different proportions i.e. 95 % fly ash + 5 %

bentonite and 90 % fly ash + 10 % bentonite.

3.2. METHODS

3.2.1 Consolidation test

Consolidation test was carried out in order to assess the hydraulic conductivity and

compressibility of the mixture. Indirect determination of the hydraulic conductivity from

consolidation tests has several advantages and disadvantages over permeability tests, which are

in the following.

(i) can apply vertical pressures simulating those in field;

(ii) can measure vertical deformations;

(iii) can test sample under a range of vertical stresses;

(iv) can test compacted specimens and undisturbed samples;

(v) thin samples permits short testing time;

(vi) cost effective method for obtaining hydraulic conductivity data over a range sample states;

However it has also some disadvantages over other methods. Those are,


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(i) Some soil types may be difficult to trim into consolidation ring;

(ii) Thin samples may not be representative;

(iii) Potential for side wall leakage;

Despite of some disadvantages, the consolidometer permeability test is potentially the most

useful among the other methods viz. rigid wall permeameter and flexible wall (triaxial)

permeameter because of the flexibility which it offers for testing specimens under a range of

confining stresses and for accurate determination of the change in sample thickness as a result of

both seepage forces and chemical influence on the soil structure. Furthermore, the thinner

samples relative to the other test type means that the pore fluid replacement can be achieved in a

short time for a given hydraulic gradient.

The hydraulic conductivity can be calculated from the consolidation test results by fitting

Terzaghis theory of consolidation (Terzaghi, 1923) to the observed laboratory time-settlement

observation and extracting the hydraulic conductivity from calculated coefficient of

consolidation. The fitting operation was carried out using Taylors square root method. A

question may arise, how the hydraulic conductivity calculated by Terzaghis theory is

comparable to that determined directly by permeability tests. Terzaghi (1923) made such

comparison when he first developed the theory; he found satisfactory agreement. Casagrande and

Fadum (1944) reported that they always found satisfactory agreement provided that there was a

distinct change in curvature when the primary settlement curve merged with the secondary

settlement curve. Taylor (1942) presented comparison for remolded specimens of Boston blue

clay, based on the square root fitting method, and showed that the measured hydraulic

conductivity generally exceeded the calculated values. He attributed this difference in hydraulic

conductivity to Terzaghis assumption that the sole cause of delay in compression in the time


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required for the water to be squeezed out, i.e. to the hydraulic conductivity of the clay. Taylor

(1942) concluded that the structure of clay itself possessed a time dependent resistance to

compression so that the total resistance to volume change came partly from the structural

resistance of the clay itself. By attributing all of the resistance to low hydraulic conductivity,

Terzaghis theory must inevitably lead to an underestimate of the hydraulic conductivity. On the

based of several experiments Mesri and Olson (1971) concluded that the calculated hydraulic

conductivity was low only by 5 to 20 % for both remoulded and undisturbed clay provided the

clay is normally consolidated at the time of determination.

In regards to the determination of the hydraulic conductivity of clayey soil, the consolidation test

has been widely used (Newland and Alley, 1960; Mesri and Olson, 1971; Budhu, 1991;

Sivapullaiah et al., 2000). This test generally provides the hydraulic conductivity comparable

with the permeability test (Terzaghi, 1923; Casagrande and Fadum, 1944) although slightly

underestimates the hydraulic conductivity compared with the permeability test (Taylor, 1942;

Mitchell and Madson, 1987). Consolidation tests were carried out to determine the hydraulic

conductivity of the mixtures.

The test was carried out on the sample of 60 mm diameter and 20 mm thickness according to

ASTM D 2435 using standard consolidometers. The samples were prepared by adding water to

the different fly ash - cement mixtures (with cement content of 0 %, 2 %, 5 %, 7 %, and 10 %),

and fly ash-bentonite mixtures (with bentonite content of 5 % and 10 %). Then the mixtures were

mixed with water to obtain the optimum moisture content (OMC). Then the sample was kept in a

humidity controlled desiccator for 24 hours in order to attain the moisture equilibrium. The

inside of the ring was smeared with a very thin layer of silicon grease in order to avoid friction

between the ring and soil sample. Filter paper was placed at the bottom and top of the sample. A


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top cap with a porous stone was placed above the soil sample. Then the mixtures were

compacted in the consolidation ring to its maximum dry density (MDD). The entire assembly

was placed in the consolidation cell and positioned in the loading frame. The consolidation ring

was immersed in the water. Then the consolidation cells were allowed to equilibrate for 24 hours

prior to commencing the test. All the samples were initially loaded with a stress of 0.5 kg/cm2,

increasing by an increment ratio of 1 (i.e. 0.1, 0.2, 0.5, 1, 2 kg/cm2

etc) to a maximum pressure

of 8 kg/cm2.

3.2.2. Linear Shrinkage test

Linear shrinkage, as used in this test method, refers to the change in linear dimensions that has

occurred in test specimens after they have been subjected to soaking heat for a period of 24 hours

and then cooled to room temperature.

Most insulating materials will begin to shrink at some definite temperature. Usually the amount

of shrinkage increases as the temperature of exposure becomes higher. Eventually a temperature

will be reached at which the shrinkage becomes excessive. With excessive shrinkage, the

insulating material has definitely exceeded its useful temperature limit. When an insulating

material is applied to a hot surface, the shrinkage will be greatest on the hot face. The differential

shrinkage which results between the hotter and the cooler surfaces often introduces strains and

may cause the insulation to warp. High shrinkage may cause excessive wrap age and thereby

may induce cracking, both of which are undesirable.

The test was carried out on the sample of 25 mm diameter and 125 mm thickness according to

using standard mould confirming to IS 12979: 1990. Soil sample weighing about 150 g from the

thoroughly mixed portion of the material passing 425 micron IS Sieve [IS 460 (Part 1): 1985]

obtained in accordance with IS 2720 (Part 1): 1983 was taken for the test specimen.


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About 150 g of the soil sample passing 425 micron IS Sieve was placed on the flat glass plate

and thoroughly mixed with distilled water, using the palette knives, until the mass becomes a

smooth homogeneous paste, with moisture content approximately 2 % above the liquid limit of

the soil. In the case of clayey soils, the soil paste shall be left to stand for a sufficient time (24

hours) to allow the moisture to permeate throughout the soil mass. The thoroughly mixed soil-

water paste was placed in the mould such that was slightly proud of the sides of the mould. The

mould was then gently jarred to remove any air pockets in the paste. Then the soil was leveled

off along the top of the mould with the palette knife. The mould was placed in such way that the

soil-water mixture (paste) can air dry slowly, until the soil was shrunk away from the walls of the

mould. Drying was completed first at a temperature of 60 to 65 C until shrinkage has largely

ceased and then at 105 to 110 C to complete the drying. Then the mould and soil was cooled

and the mean length of soil bar measured because the specimen was become curved during

drying.

3.3. DETERMINATION OF HYDRAULIC CONDUCTIVITY AND COMPRESSIBILITY

For each pressure increment the change in the thickness of soil sample was measured from the

readings of the dial gauge. Then the change in the void ratio corresponding to an increase in the

overburden pressure was calculated by the Eq. 1,

e= H(1+e)/H (Eq. 1)

Where, H = Change in the thickness of sample due to increase in pressure

H = Initial thickness of the sample, e = Initial void ratio

From the calculated void ratios, a plot of void ratio, e vs log of pressure, p, was plotted. The

compression index (Cc) was calculated from the slope of this curve, or

Compression index (Cc) = - ji

ji

pp

ee

/log

(Eq. 2)


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Where,

ei = Void ratio corresponds to a consolidation pressure ofpi

ej = Void ratio corresponds to a consolidation pressure ofpj

From the consolidation test result, a time-settlement curve was obtained at each pressure

increment. The coefficient of consolidation cvwas obtained using Taylors square root time (T)

method.

The co-efficient of volume change can be calculated by the formula,

mv= av /(1+e) (Eq. 3)

where, av = coefficient of compressibility

= /e where,

= Change in pressure

e = Change in void ratio

The hydraulic conductivity, k, was calculated using the Eq. 4 for various pressure increments

using the cv

, and coefficient of volume change, mv

k= cvm

v

w(Eq. 4)

where, w

is the unit weight of the pore fluid

3.3.1. DETERMINATION OF LINEAR SHRINKAGE

The linear shrinkage of the soil shall be calculated as a percentage of the original length of the

specimen from the following formula:

Linear Shrinkage (LS), (%)= (1 - Ls/ L) 100%

Where,

L = Length of the mould (mm)

Ls = Length of the of the oven dry specimen (mm)


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Chapter-4

RESULTS AND DISCUSSION

4.1. General

The results of different tests carried out on various fly ash-cement mixes and fly ash-bentonite

mixes are presented in this chapter.

4.1.1 Compaction properties of the various fly ash-cement mixtures

Compaction test is carried out for the five different fly ash-cement mixtures, i.e. pure fly ash,

98 % fly ash + 2 % cement, 95 % fly ash + 5 % cement, 93 % fly ash + 7 % cement, 90 % fly ash

+ 10 % cement. The optimum moisture content (OMC) and maximum dry density (MDD) for all

the five mixtures has been tabulated in Table 2. The data in the table shows that the OMC and

MDD for the mixtures increase with the increase in the cement content of the mixtures.

Table 2. OMC and MDD values of fly ash cement mix with different proportion

Mixing Combination Optimum Moisture Content

(OMC), %

Maximum Dry Density

(MDD)

kg/m3

Pure fly ash 17.0 131998 % fly ash + 2 % cement 18.2 1339

95 % fly ash + 5 % cement 19.3 1339

93 % fly ash + 7 % cement 19.9 1368

90 % fly ash + 10 % cement 20.4 1377

4.1.1.1. Hydraulic conductivity

Hydraulic conductivity is one of the most important criteria for soil to be used as a liner material

at the waste disposal site. Most of the regulatory authority in the world has recommended that

the material to be used as a liner material must have a minimum value of hydraulic conductivity

of 10-6 cm/sec compacted at MDD and OMC. Result of the hydraulic conductivity for all the five

mixtures shows that all mixtures satisfy the hydraulic conductivity criteria required for a landfill

liner. Result shows that the hydraulic conductivity value for the five mixtures decreased with a

decrease in the void ratio. The decreases in the hydraulic conductivity with the decrease in the


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void ratio was quite steep at the beginning, however, with a further decrease in the void ratio

there was a marginal decrease in the hydraulic conductivity.

In a comparison among the five mixtures, it can be seen that with the increase in the cement

content the hydraulic conductivity decreases. In other words, at the same void ratio mixture withhigher cement content exhibits a lower hydraulic conductivity. When the cement content

increases and it comes in contact with the water, it holds the fly ash particles on its surface and

gets solidify and in turn blocks the flow path thereby reducing the hydraulic conductivity.

Figure 3. Relation between void ratio and hydraulic conductivity for the five mixtures

1.E-08

1.E-07

1.E-06

1.E-05

0.44 0.46 0.48 0.5 0.52 0.54 0.56 0.58

Void ratio

Hydrauliccond

uctivity(cm/sec

100% fly ash

98% fly ash + 2% cement





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4.1.1.2. Compressibility

Figure 4 shows the relation between the pressure and void ratio for the five mixtures. The result

shows that with an increase in the overburden pressure the void ratio of the mixture decreases.

The increase in the overburden pressure on the five mixtures can be correlated with the increase

in the pressure on the liner due to the increase in the weight of the overburden weight due to

dumping of more and more waste material. The result shows that the decrease in the void ratio

with an increase in the pressure is quite marginal in the beginning. However, with an increase in

the load the mixtures get compressed significantly. Result shows that the mixture with a higher

fly ash content possessed a lower void ratio at any given overburden pressure. This can be

attributed to the presence of the higher amount of fine particles in the fly ash. With the increase

in the fine content of the mixture the void ratio decreases.

Figure 4. Relation between void ratio and over burden pressure for the five mixtures

0.42

0.44

0.46

0.48

0.5

0.52

0.54

0.56

0.58

0.01 0.1 1 10Pressure (kg/cm

2)

Voidratio

100% fly ash






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Compression index (Cc) and expansion index (EI) for all the five mixtures was determined from

the Fig. 4 and tabulated in Table 3. The data in Table 3 shows the compression index of the

mixture gets affected marginally by the presence of the cement. However, the expansion index

gets affected significantly due to cement content. The expansion index decreases with an

increase in the cement content. The increase in the cement makes the mixture more cementitious

and it gets hardened due to the increase in the over burden pressure. With the removal of the over

burden pressure it re-bounced less significantly in comparison to the pure fly ash.

From the values of expansion index we can say that for all five type of mix the potentiality of

expansion is very low because all three values are in between 0-20.

SL.

NO.

Mixing Composition Compression Index

(Cc)

Expansion Index (EI)

1 Pure fly ash 0.077138 9.4

2 98 % fly ash + 2 % cement 0.077032 6.33 95 % fly ash + 5 % cement 0.095965 2.5

4 93 % fly ash + 7 % cement 0.025885 1.9

5 90 % fly ash + 10 % cement 0.081374 1.5

Expansion Index (EI) Potential Expansion

0-20 Very Low21-50 Low

51-90 Medium

91-130 High

>130 Very High

Table 3. Values of com ression index and ex ansion index of fl ash-cement mix

Table 4. Classification of Potential Ex ansion of Soils Usin EI


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4.1.1.3. Linear Shrinkage

Liner shrinkage for all the five type of fly ash-cement mixtures was found to be zero. The length

and the diameter of all the five mixtures did not reduce after keeping in oven for 24 hours.

4.1.4. Co-efficient of consolidation(cv)

The coefficient of consolidation (cv) signifies the rate at which a saturated soil sample undergoes

one dimensional consolidation when subjected to an increase in the vertical consolidation

pressure. A large value ofcv indicates a faster rate of consolidation whereas a low value indicates

a slower rate of consolidation. Figure 5 shows the plot between co-efficient of consolidation (cv)

against the vertical consolidation pressure for the five mixtures. The result for the five mixtures

0

0.005

0.01

0.015

0.02

0.025

0.03

0.035

0.04

0.045

0.01 0.1 1 10pressure (kg/cm

2)

Co-efficientofcompressibility,mv(cm2/kg)

100% fly ash


95% fly ash + 5% cement93% fly ash + 7% cement


Figure 5. Relation between co-efficient of compressibility and over burden pressure forthe five mixtures


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shows that cv decreases with the increase in the over burden pressure. Result also shows that the

value ofcv differs significantly initially, however, with the increase in the pressure the difference

in the value ofcv for the five mixtures decreases significantly.

Figure 6. Relation between coefficient of consolidation and over burden pressure for the

five mixtures

0

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

0.09

0.1

0.01 0.1 1 10

Pressure (kg/cm2)

Co-efficientofconsolidation(cm2/sec)

100% fly ash






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4.2.1. Compaction properties of the mixtures

Compaction test was carried out for the three different fly ash and bentonite mixtures, i.e. pure

fly ash, 95 % fly ash + 5 % bentonite, and 90 % fly ash + 10 % bentonite. The optimum moisture

content (OMC) and maximum dry density (MDD) for all the three mixtures has been tabulated in

Table 5. The data in the table shows that the OMC and MDD for the mixtures increase with the

increase in the bentonite content of the mixtures.

Table 5. OMC and MDD values of fly ash- bentonite mix with different proportion

Mixing Combination Optimum Moisture Content

(OMC)

Maximum Dry Density

(MDD) kg/m3

Pure Fly ash 17.0 % 1319

95% Fly ash + 5% Bentonite 18.0 % 1398

90% Fly ash + 10% Bentonite 19.8 % 1412

4.2.2. Hydraulic conductivity

In case of fly ash and bentonite mix result of hydraulic conductivity shows that all three mixtures

satisfy the hydraulic conductivity criteria require for a liner material. For all the mixtures the

value of hydraulic conductivity was found to be less than 10 -6 cm/sec, the limiting criteria for the

use of a landfill liner material. From Fig. 7 shows that the hydraulic conductivity value for the

three mixtures decreased with a decrease in the void ratio. The decrease in the hydraulic

conductivity with the decrease in the void ratio was quite steep at the beginning for the pure fly

ash and 95 % fly ash + 5 % bentonite mixtures. However, the hydraulic conductivity of the 90 %

fly ash + 10 % bentonite decreased uniformly with the decrease in the void ratio.


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In a comparison among the three mixtures, it can be seen that with the increase in the bentonite

content the hydraulic conductivity increases. In other words, at the same void ratio mixture with

higher bentonite content exhibits a higher hydraulic conductivity. Generally, the hydraulic

conductivity tends to decreases with the increase in the bentonite content (Chapuis, 1990). This

opposite trend can be explained in terms of the presence of various salts in the fly ash (Ohtsubo

et al., 2004). When fly ash-bentonite mixtures comes in contact with water, the various cations

such as Na+, Ca2+ leached out from fly ash and react with the bentonite present in the mixture.

Because of these cations the repulsive force of the bentonite decreases and the bentonite becomes

flocculated (van Olphen, 1977). As the bentonite gets flocculated, the flow path becomes open

and the hydraulic conductivity increases (Benson and Daniel, 1990).

1.E-08

1.E-07

1.E-06

1.E-05

0.39 0.41 0.43 0.45 0.47 0.49 0.51 0.53 0.55 0.57

Void ratio

Hydraulicconductivity(cm

/sec

90% Fly ash + 10% Bentonite


100 % Fly ash

Figure 7. Relation between void ratio and hydraulic conductivity for the three mixtures


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4.2.3. Compressibility

Figure 8 shows the relation between the pressure and void ratio for the three mixtures. The result

shows that with an increase in the overburden pressure the void ratio of the mixture decreases.

From the figure we can say that lower bentonite content gives higher void ratio with the increase

overburden pressure. The result shows that the decrease in the void ratio with an increase in the

pressure is quite marginal in the beginning. However, with an increase in the load the mixtures

get compressed significantly.

0.3

0.35

0.4

0.45

0.5

0.55

0.6

0.1 1 10

Pressure (kg/cm2)

Voidratio

90% Fly ash + 10 % Bentonite


100% Fly ash

Figure 8. Relation between void ratio and over burden pressure for the three mixtures


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Figure 9. Relation between pressure and co-efficient of compressibility

Compression index (Cc) and expansion index (EI) for all the two mixtures was determined from

the Fig. 7 and tabulated in table 6. The data in table 6 shows the compression index of the

mixture gets affected by the presence of the bentonite. The increase in the bentonite results in

increase in compression index (Cc). However, the expansion index gets affected marginally due

to bentonite content. From the values of expansion index we can say that for all three type of mix

the potentiality of expansion is very low because all three values are in between 0-20. The

0

0.01

0.02

0.03

0.04

0.05

0.06

0.1 1 10

Pressure (kg/cm2)

Co-efficientofcompressibility,mv(cm2/kg)



100% Fly ash


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expansion index increases with an increase in the bentonite content. This behavior of the mixture

is due to the excessive swelling potentiality of bentonite and With the removal of the over burden

pressure it re-bounced very significantly in comparison to the pure fly ash. The data in table 6

also shows that linear shrinkage of fly ash and bentonite mixture increases with the increase in

the bentonite content. This is due to the swelling potentiality of bentonite because after drying

swelling of the mixture decreases, eventually to zero. As a result the mixture shrunk.

Table 6. Values of compression index, expansion index and linear shrinkage of fly ash and

bentonite mix

Sl. No. Mixing Composition Compression Index

(Cc)

Expansion

Index(EI)

Linear

Shrinkage %1 Pure Fly Ash 0.077139 9.4 0

2 95 % Fly ash + 5 %

Bentonite

0.114449 11.4 1.6

3 90 % Fly ash + 10 %

Bentonite

0.332663 17.7 3.2


In case of fly ash and bentonite mix the values of Co-efficient of consolidation is very large atthe beginning. Figure 10 shows the plot between co-efficient of consolidation (cv) against the

vertical consolidation pressure for the three mixtures. The result for the three mixtures shows

that cv decreases with the increase in the over burden pressure. Result also shows that the value

ofcv differs significantly initially.

4.3. Comparisons between cement and bentonite mix with fly ash (5% and 10%)

4.3.1. Optimum moisture content and maximum dry density

All the values of optimum moisture content and maximum dry density are tabulated below. From

Table 7 it is clear that bentonite mix gives higher value of optimum moisture content and

maximum dry density for both the 5 % and 10 % mixtures.


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Figure 10. Relation between coefficient of consolidation and over burden pressure for the fly ashand bentonite mixtures

4.3.2. Hydraulic conductivity

It is recommended that the material to be used as a liner material must have a minimum value of

hydraulic conductivity of 10-6 cm/sec compacted at MDD and OMC. In Fig.10 a graphical

relation between void ratio and hydraulic conductivity for 5 % and 10 % cement and bentonite

content has been established. Result shows that hydraulic conductivity value for the four

mixtures decreased with a decrease in the void ratio. The figure shows that 95% fly ash and 5%

cement mixture gives lower value of hydraulic conductivity.

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.1 1 10

Pressure (kg/cm2)

Co-efficiento

fconsolidation,cv(cm

2/sec)



100% Fly ash


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Table 7. values of OMC and MDD 5 % and 10 % cement and bentonite respectively

Sl. No. Mixing CombinationOptimum Moisture

Content (OMC)

Maximum Dry Density

(MDD) kg/m3

1 95% fly ash + 5% cement 19.3 % 1339

2 95% fly ash + 5% bentonite 18.0 % 13983 90% fly ash + 10% cement 20.4 % 1368

4 90% fly ash + 10% bentonite 19.8 % 1412

1.E-07

1.E-06

1.E-05

0.35 0.4 0.45 0.5 0.55 0.6

Void ratio

HydraulicConductivity(cm/sec


95% fly ash + 5% bentonite

90% fly ash +10% bentonite


Figure 10. Relation between void ratio and hydraulic conductivity for 5 % and 10 % cement and

bentonite content


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4.3.3. Compressibility

Figure 11 shows the relation between pressure and void ratio for the four mixtures. The result

shows that the both 5 % and 10 % cement content gives higher value than 5 % and 10 %

bentonite content. Whereas 90 % fly ash and 10 % bentonite gives lowest value of void ratio.

The increase in the overburden pressure on the four mixtures can be correlated with the increase

in the pressure on the liner due to the increase in the weight of the overburden pressure because

of more waste material.

In Fig.12 A relationship between pressure and co-efficient of compressibility for 5 % and 10 %

cement and bentonite content has been plotted. From the figure it is clear that the characteristic

of both 5 % and 10 % bentonite is parabolic. Whereas in case of cement the values of co-

efficient of compressibility are higher at the beginning then it decreases with the increase in

overburden pressure.

0.35

0.4

0.45

0.5

0.55

0.6

0.01 0.1 1 10

Pressure (kg/cm2)

Voidratio





Figure 11. Relation between pressure and void ratio for 5% and 10% cement and bentonite content


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0

0.01

0.02

0.03

0.04

0.05

0.06


2)

Co-e

fficientofcompressibility





Figure12. Relation between pressure and co-efficient of compressibility for 5% and 10%cement and bentonite content


48/53

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Figure13 shows the plot between pressure and co-efficient of consolidation for 5 % and 10 %

cement and bentonite content. Result shows that for 5 % and 10 % bentonite content co-efficient

of consolidation decreases greatly at the beginning and after 0.5 kg/cm2

pressure it maintains

almost a linear stability. In case of 5 % and 10 % cement content compression index of the

mixture gets affected marginally by the presence of the cement. Result also shows that the value

ofcv differs significantly initially, however, with the increase in the pressure the difference in the

value ofcv for the four mixtures decreases significantly.

0.01

0.06

0.11

0.16

0.21

0.26

0.31

0.36


2)

Co-efficientofcons

olidation(cm2/sec)





Figure13. Relation between pressure and co-efficient of consolidation for 5% and 10%

cement and bentonite content


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5. CONCLUSIONS

From the series of experimental data it is clear that fly ash has a bigger role in the application of

geo-environmental engineering especially in landfill liner design. The data from compaction test

shows that both optimum moisture content and maximum dry density increases with increase in

the use of bentonite and cement with fly ash. With further laboratory testing likely consolidation

test reveals that hydraulic conductivity for both fly ash-cement and fly ash-bentonite is less than

10-6 cm/sec. It also shows that co-efficient of consolidation and co-efficient of compressibility

both decreases with the increase in the overburden pressure. But on the other hand from linear

shrinkage data it is clear that fly ash-cement mixture is not showing any sign of shrink because

of cement hardening. In case of fly ash-bentonite mix it shows considerable amount of shrink

which increases with the increase in bentonite content. From the pressure-void ratio curve it can

be concluded that with the increase in the fine content of the mixture results in the decrease in

the void ratio. So at the end it can be concluded that 95 % fly ash + 5 % cement and 95 % fly ash

+ 5 % bentonite is suitable to use in landfill liner.

.

6. SCOPE FOR THE FUTURE WORK

Based on the result presented above, further studies can be carried out:

I. To determine the shear strength of different proportion of fly ash + cement and fly ash +bentonite mixture.

II. Determination of compaction, strength, compressibility and permeability characteristicsof alternative material.

III. To develop a new setup for locally available soil.


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IV. To evaluate the suitable fly ash-expansive soil mix that can be used as landfill liner.V. To propose different combination of parameters as design criteria for fly ash-expansive

soil mix.


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REFERENCES

ASTM (2000). Standard Test Methods for Laboratory Compaction Characteristics of Soil Using

Standard Effort, D 698. Philadelphia,American Society for Testing and Materials.

ASTM (1996). Standard Test Method for One-Dimensional Consolidation Properties of Soils, D2435. Philadelphia,American Society for Testing and Material.

Benson, C.H. and Daniel, D.E. (1990). Influence of clods on hydraulic conductivity ofcompacted clay,Journal of Geotechnical Engineering, 116(8), 1231-1248.

British Standards (1990). Methods of test for soils for civil engineering purposes: classificationtests 1377-2.

Budhu, M. (1991). The permeability of the soils with organic fluids. Canadian Geotechnical

Journal, 28, 140-147.

Casagrande, A. and Fadum, R.E. (1944). Notes on Soil Testing for Engineering Purposes: Soil

Mech. Series No.8, Harvard Graduate School of Engineering

Chapuis, R.P. (1990). Sand-bentonite liner: predicting permeability from laboratory test,Canadian Geotechnical Journal, 27, 47-57.

Cowland, J.W. and Leung, B.N. (1990), A field trial of a bentonite landfill liner, Civil

Engineering Services Department, 9th Floor Empire Centre, 68 Mody Road, Kowloon, Hong

Kong.

Dietrich Koch (Applied Clay Science 21 (2002) 1 11)Bentonites as a basic material fortechnical base linersand site encapsulation cut-off walls IBECO Bentonit-Technologie GmbH,Ruhrorter Strae 72, D-68219 Mannheim, Germany.

Felhendler, R., Shainberg I., and Frenkel, H. (1974). Dispersion and hydraulic conductivity of

soils in mixed solution.In International Congress of Soil Science, Transaction, 10th

(Moscow), 1,103-112.

Hoeks, J., Glas, H., Hofkamp, J. and Ryhiner, A.H. (1997) Bentonite liners for isolation of wastedisposal sites, Waste Management & Research, 5, 93-105.

Horpibulsuk, S., Bergado, D. T. and Lorenzo, G. A. (2003) Compressibility of cement-admixed

clays at high water content, School of Civil Engineering, Suranaree University of Technology,Thailand.

Lambe, T.W. (1953). The structure of inorganic soil, Journal of soil mechanics and foundationdivision, 79, 1-49


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52

Lundgran, T. and Soderblom, R. (1984). Clay barrier not fully examined possibility, SweedishGeotechnical Institute, Linkoping (sweeden)

Mesri, G., and Olsen, R.E. (1971). Mechanisms controlling the permeability of clays. Clay andClay Minerals, 19,. 151-158.

Mitchell, J.K., and Madson, F.T. (1987). Chemical effects on the clay hydraulic conductivity. In

Geotechnical practice for waste disposal. American Society for Civil Engineers, New York, 87-

116.

Newland, P.L., and Alley, B.H. (1960). A study of consolidation characteristics of a clay.Geotechnique, 10, 62-74.

Ohtsubo M, Li LY, Yamaoka S, Higashi T (2004) Leachibility of heavy metals and salt from

bottom ash. 5th Geoenvironmental Engineering Symposium, Japanese Geotechnical Society,

169174.

Olson, R.E., and Daniel, D.E. (1981). Measurement of hydraulic conductivity of fine grained

soils.In Permeability and ground water contaminant transport.American Society for Testing and

Materials, STP 746, 18-60.

Pandian, N.S., Nagaraj, T.S., and Narasimha Raju, P.S.R. (1995). Permeability andcompressibility behaviour of bentonite-sand/soil mixes. Geotechnical Testing Journal,18(1), 86-

93.

Reddy, K.R., Stark, T.D. and Marella, A. (2008) Clogging potential of tire shred drainage layerin landfill cover systemInternational Journal of Geotechnical Engineering 2, 407 -418

Shenbaga R. Kaniraj and V. Gayathri (2003) Factors Influencing the Strength of Cement Fly

Ash Base Courses,Journal of transportation engineering, 129(5), 538-548.

Shenbaga, R., Kaniraj, R. and V. Gayathri, V. (2004). Permeability and consolidation

characteristics of compacted fly ash,Journal Energy Engineering, 130(1), 18-43

Sivapullaiah, P.V., Sridharan, A., and Stalin, V.K. (2000). Hydraulic conductivity of bentonite-

sand mixtures. Canadian Geotechnical Journal, 37,. 406-413.

Taylor, D.W. (1942). Research on Consolidation of Clays,Serial 82, Massachusetts Institute of

Technology, Department of Civil Engineering, Cambridge.

Terzaghi, K.T. (1923). Die Berechnung der Durchlassigkeitsziffer des Tons aus dem Verlauf der

hydrodyanamicschen Spannungserscheinungen. Akademie der Wissenschaften in Wien.Sitzungsberichte, Mathematischnaturwissenschaftliche Klasse-IIa, 132: 125-138.

van Olphen (1977).An introduction to clay colloidal chemistry: for clay technologists, geologists,

and soil scientists, John Wiley and Sons.


53/53

Warith, M.A. and Rao, S.M. (2006). Predicting the compressibility behaviour of tire shredsamples for landfill applications, Waste Management, 26, 268276.

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