Subgrade Soil Stabilization by Using Flyash and Lime

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A PROJECT REPORT

ON

“SUBGRADE SOIL STABILIZATION BY USING FLYASH AND LIME” Submitted to Vikash College of Engineering for Women, Bargarh

In Partial Fulfillment of the requirements

For the degree of Bachelor of Technology

In Civil Engineering By

SUMAN PATEL (1121337003)

DEPARTMENT OF CIVIL ENGINEERING

VIKASH COLLEGE OF ENGINEERING FOR WOMEN

BARGARH


BARGARH

ODISHA

SESSION: 2010-2014



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CERTIFICATE

This is to certify that the project on the subject “SUBGRADE SOIL STABILIZATION

BY USING FLYASH AND LIME” has been successfully completed and delivered by

SUMAN PATEL (1121337003) belonging to 7th semester, Civil Engineering. This project

development and presentation was accomplished under my supervision.

Mr. NABEEN BAGE

Project supervisor


BARGARH- 768028, ODISHA

SESSION: 2010-2014



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CERTIFICATE OF APPROVAL

This project report entitled

“SUBGRADE SOIL STABILIZATION BY USING

FLYASH AND LIME” submitted by SUMAN PATEL (1121337003) of 7th

semester Civil

Engineering to VCEW, Bargarh has been examined by us. The project report is found fit and

approved for the award of the degree of BACHELOR OF TECHNOLOGY in Civil Engineering

EXTERNAL EXAMINER



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ACKNOWLEDGEMENT

This is to acknowledge the help and encouragement that we received from various persons andsources during our project work. In this connection we would like to the name of our project

guide Mr. NABEEN BAGE, who was a constant source of valuable instruction and constant

encouragement. We are indebted to our guide for providing his valuable time, constant

guidance, co-operation and scrupulous supervision to complete this project report. His untiring

effort, availability in spite of his preoccupations and friendly behavior needs special mention

.We are extremely grateful to all the faculty members of civil engineering department who

shared not only their vast knowledge with us, but also lent their valuable time.

Finally, we are saluting to all those websites those need worth mentioning for sufficing us with

some hard found materials.

SUMAN PATEL (1121337003)



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CONTENTS

CERTIFICATE

ACKNOWLEDGEMENT……………………………………………………………………..Page no

ABSTRACT…………………………………………………………………………………………… 1

CHAPTER 1 2-3

INTRODUCTION……………………………………………………………………………………. .2

GENERAL……………………………………………………………………………………………… .2

SCOPE OF THE OBJECT…………………………………………………………………………. 3

OBJECTIVES OF THE PROJECT………………………………………………………………..3

CHAPTER 2: 4-10

LITERATURE REVIEW

2.1:RECENT RESEARCHES………………………………………………………………………4

2.2:GENERAL……………………………………………………………………………………….’.6

2.3:SOIL STRUCTURE…………………………………………………………………………… .6

2.5:QUALITY IMPROVEMENT………………………………………………………………. 7

2.6:STABILIZATION TECHNIQUES………………………………………………………… 7

2.7.1 STABILIZATION WITH LIME…………………………………………………………………………… 7

2.7.2 STABILIZATION WITH FLY ASH……………………………………………………………… 10



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CHAPTER 3: 11-14

EXPERIMENTAL PROGRAMME

3.1: INTRODUCTION………………………………………………………………………………….11

3.2: MATERIALS USED………………………………………………………………………………………….11

3.3: LAB TESTING……………………………………………………………………………………………….. ..12

3.4: SOIL PREPARATION……………………………………………………………………………………… ..12

3.5: STANDARD PROCTOR TEST………………………………………………………………………….…13

3.6: CBR TEST…………………………………………………………………………………………………………………………..13

3.7: SPECIFIC GRAVITY……………………………………………………………………………………………………………..14

3.8: LIQUID LIMIT………………………………………………………………………………………………………………………14

CHAPTER 4: 15-18

RESULT AND DICUSSION………………………………………………………………………….15

CHAPTER 5: 19-20

SUMMARY AND CONCLUSION………………………………………………………………..19

REFERNCES……………………………………………………………………………………………..20

LIST OF TABLES:

Table 1-PROPERTIES OF SOIL USED IN THE STUDY

Table 2-VARIATION OF MDD & OMC & CBR VALUE WITH FLYASH

CONTENT



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Table 3-VARIATION OF MDD & OMC & CBR VALUE WITH LIME

CONTENT

ABSTRACT

Subgrade is basic foundation for any civil engineering structures. It is

required to bear the loads without failure. In some places, soil may be

weak which cannot resist the upcoming loads. In such cases, subgrade

soil stabilization is needed. Numerous methods are available in the

literature for subgrade soil stabilization. But sometimes, some of themethods like chemical stabilization, lime stabilization etc. Adversely

affects the chemical composition of the subgrade soil.

In the study, flyash and lime were mixed with subgrade soil to

compaction. The effect of flyash and lime on the geotechnical

characteristics subgrade-flyash and subgrade-lime mixtures was

investigated by conducting standard proctor compaction tests. The test

were performed as per Indian standard specifications.

The following materials were used for preparing the samples:

Subgrade soil

Flyash

Lime

The subgrade soil used for these experiments was brought from a site,

near Bargarh. The physical property of the subgrade were determined as

per IS specifications.

In this test programmed, without additive subgrade was tested to find the

optimum moisture content, bearing strength. Flyash and lime were added



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in varying percentages and that fraction for which maximum strength is

obtained was found out.

CHAPTER 1

INTRODUCTION:

GENERAL

Transport in the Republic of India is an important part of the nation’s

economy. Roads are the vital lifelines of the economy making possible

trade and commerce. They are the most preffered modes of

transportation and considered as one of the cost effective modes. An

efficient and well-estabilished network of roads is desired for promoting

trade and commerce in any country and also fulfils the needs of a sound

transportation system for sustained economic development. To provide

mobility and accessibility, all weather roads should connect every nook

and corner of the country. To sustain both static and dynamic load, the

pavement should be designed and constructed with utmost care. The

performance of the pavement depends on the quality of materials used in

road construction.

Subgrade is in situ material upon which the pavement structure is

placed. Although there is a tendency to look at pavement performance interms of pavement structures and mix design alone, the subgrade soil

can often be the overriding factor in pavement performance. The

construction cost of pavements will be considerably decreased if locally

available low cost materials are used for construction of lower layer of

pavements such as subgrade, sub base etc. If the stability of local soils is



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not adequate for supporting for the loads, suitable methods to enhance

the properties of soil need to adopt. Soil stabilization is one such

method.

This report contains a summary of the performance of lime and flyashused with subgrade.

Flyash are finely divided residue resulting from aluminium plant.

Lime is another additive used, which is locally available, to improve

subgrade characteristics. It is obtained by heating limestone at elevated

temperatures.

SCOPE OF THE PROJECT

The soil used in the study is subgrade soil brought from a site, near

Bargarh. Pavement subgrade over there is composed of natural soil

whose bearing capacity is sufficient. This proves to be economic for

road construction. Soil stabilization can be done using different

additives, but use of flyash which is a waste material from aluminium

plant at the same time difficult to dispose material will be much

significant.

OBJECTIVE OF THE PROJECT

The major objectives of the project are:

1. To explore the possibility of using flyash in road construction

program.

2. To study the effect of lime and flyash on proctor’s density and

OMC of subgrade soil.



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3. To study the effect of lime and flyash on the liquid limit of

subgrade soil.

4. To stu

5.

dy the changes in bearing strength of soil by addition of lime andflyash.

CHAPTER 2

LITERATURAL REVIEW

The losses due to extensive damage to highways running over expansive

soil subgrades are estimated to be in billions of dollars all over the world

(Jones and Holtz, 1973; Steinberg, 1992). Various remedial measures

like soil replacement (Snethen et al, 1979; Chen, 1988), prewetting

(Bara, 1969; Rao and Satyadas, 1980), moisture control (Mohan and

Rao, 1965; Marienfeld and Bakeras 1999), lime stabilization (Holtz and

Gibbs, 1956; Thompson and Robnett, 1976; Bansal et al, 1996) have

been practiced with varied degree of success. However, these technique

suffer from certain limitations respect to their adaptability like longer

time periods required for prewettting the highly plastic clays, (Felt,1953;

Steinberg,1977), difficulty in constructing the ideal moisture barriers

(Snethen et al,1979; Chen,1988), pulverization and mixing problems in

case of lime stabilization (Holtz,1969; Ramana Murty,1998) and high

cost for hauling suitable refill material for soil replacement (Snethen et

al,1979; Chen,1988)etc.

In India there are about 82 thermal power plants, which are currently

producing about 100 million tons of flyash per annum (Dhar, 2001). In

order to utilize fly ash in bulk quantities, ways and means are being

explored all over the world to use it for construction of embankments

and roads (Hausmann, 1990; Veerendra Singh et al, 1996; Boominathan



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and Ratna Kumar, 1996; Murthy, 1998). According to the latest

MORHT specifications, several types of gravel are found to be

unsuitable for road construction in view of higher finer fraction and

excessive plasticity properties.

Krupavaram had made attempt to use lime stabilized flyash subbase

course in model field pavement stretches. Standard proctor test and CBR

tests were conducted on flyash subbase and lime stabilized fly ash

subbase stretches constructed on different subgrades(i.e expansive soils

& sand) and observed that lime stabilized flyash stretch showed better

performance in load carrying capacity and reduction of heave laid on

expansive soil subgrade.

In another investigation an attempt was made to use cement stabilized

flyash subbase course in field pavement stretches and compared

performance with flyash subbase. Standard proctor test and CBR test

were conducted in flyash subbase and cement stabilized flyash subbase

stretches constructed on different subgrades (i.e sand &expansive

soil)and found that cement stabilised flyash stretch had shown better

performance in load carrying capacity and reduction of heave compared

to conventional stretch, laid on expansive soil subgrade.

Kumar et al had conducted on experimental program to study the effect

of lime stabilization of geotechnical characterstics of flyash soil-mixture.

From results it was observed that the expansive soil can be successfully

stabilized by the combined action of lime and flyash.

Zha et al studied the potential use and the effectiveness of stabilization

of expansive soil using flyash and flyash-lime admixture.The test results

showed that the plasticity index, activity, free, swell, potential, swelling pressure and axial shrinkage percent decreased with an increased flyash

or flyash – lime content.



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Rao et al carried out a study on the performance of lime stabilized flyash

cushion and found that it was quite effective in arresting volume changes

in expansive soils.

GENERAL

Stabilization is the process of blending and mixing materials with asoil

to improve certain properties of the soil. The process may include the

blending of soils to achieve a desired gradation or the mixing of

commercially available additives that may alter the gradation, texture or

plasticity, or act as a binder for cementation of the soil.

The process of reducing plasticity and improving the texture

of a soil is called modification. Monovalent cations such as sodium and

potassium are commonly found in sugrade soil and these cations can beexchanged with cations of higher valencies such as calcium which are

found in lime and flyash. This ion exchange process takes place almost

rapidly, within a few hours. The calciumcations replace the sodium

cations around the clay particles, decreasing the size of bound water

layer, and enable the clay particle to flocculate. The flocculation creates

a reduction in plasticity, an increase in shear strength of subgrade soil

and improvement in texture from a cohesive material to more granular,

sand-like soil. The change in structure causes a decrease in the moisture

sensitivity and increase the workability and constructability of soil. Soil

stabilization includes the effect from modification with a significant

additional strength.



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SOIL STRUCTURE

Soil structure refers to the gross arrangement of the soil particles intoaggregates. A soil may have either a simple or a compound structure.

Sands and gravels, examples of soils with a simple structure, have very

little cohesion, plasticity, and consistency, the resistance of the particles

in the soil to separation. Simple-structured soils are usually composed of

materials that are relatively resistant to weathering, such as quartz sand.

They, are also said to have a single-grain structure. As the liquid limit

greater than 35 and less than 50 with medium compressibility the soil

can classified as fine grained soil, which is under inorganic clay (CI).

USES OF STABILIZATIONPavement 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 through densification. As thequality 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 IMPROVEMENTThe most common improvements achieved through stabilization include

better soil gradation, reduction of plasticity index or swelling potential,

and increases in durability and strength. In wet weather, stabilizationmay also be used to provide a working platform for construction

operations. These types of soil quality improvement are referred to as

soil modification.

STABLIZATION WITH LIME



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Lime stabilization is done by adding lime to soil. This is

useful for the stabilization of subgrade soil. When lime reacts with soil

there is exchange of cations in the adsorbed water layer and a decrease

in the plasticity of the soil occurs. The resultant material is more friable

than the original natural soil, and is more suitable as subgrade. Lime is produced by burning of limestone in kiln. The quality of lime obtained

depends on the parent material and the production process. And there are

basically 5 types of limes.

1. High calcium, quick lime (CaO)

2. Hydrated high calcium lime [Ca(OH)2]

3. Dolomitic lime [CaO+MgO]

4.

Normal, hydrated Dolomitic lime [Ca(OH)2+MgO]5. Pressure, hydrated Dolomitic lime [Ca(OH)2+MgO2]

The two primary types of lime used in construction today are quick lime

(calcium oxide) and hydrated lime (calcium hydroxide). Heating lime

stone at elevated temperatures produce quick lime and addition of water

to quick lime produces hydrated lime.

Equation shows the relation that occurs when limestone is heated to

produce quick lime with carbon dioxide as by-product.

CaCO3 + heat → CaO + CO2

Addition of water to quick lime produces hydrated lime along with heat

as product:

CaO + H2O → Ca(OH)2 + heat

For stabilization with lime, soil conditions and mineralogical properties

have a significant effect on the long term strength gain.

MECHANISM



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For soil stabilization with lime, soil conditions and

mineralogical properties have a significant effect on the long-term

strength gain. A pozzolanic reaction between silica and alumina is the

soil particles and calcium from the lime can form a cemented structure

that increases the strength of the stabilized soil. Residual calcium mustremain in the system to combine with the available silica or alumina to

keep the pH high enough to maintain the pozzolanic reaction. Soil that

should be consider for lime treatment include soil with a PI that exceeds

10 and have more than 25 percent passing the #200 sieve.

In lime stabilization the liquid limit of soil generally decrease

but the plastic limit increases. Thus the plasticity index of the soil

decreases. The strength of lime stabilized soil is generally improved. It is partly due to the formation of cementing material. Increase in the

unconfined compressive strength is as high as 60 times. The modulus of

elasticity of the soil also increases substantially.

Addition of lime causes a high concentration of calcium ions in

double layer. It causes a decrease in the tendency of attraction of water.

Consequently, the resistance of soil to water absorption, capillary rise

and volume changes on wetting or drying is substantially increased. The

lime-stabilized bases or subbases form a water resistant barrier which

stops penetration of rain water. There is an increase in optimum

moisture content and a reduction in maximum density. In swampy areas

where the water content is above the optimum, application of lime to soil

helps in drying of soil. Cyclic freezing and thawing can causes a

temporary loss of strength, but because of subsequent healing action,

there is no loss of strength in long run. Construction method used in lime

stabilization are similar to those used in cement stabilization.

However, the following points are to be noted.

1. As the reaction in the case of lime is low, there is no maximum

time limit between the addition of lime to the soil and the



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completion of compaction. However, care should be taken to avoid

carbonation of lime in the process.

2. Lime may be added in form of slurry instead of dry powder.

3. A rest period of 1 to 4 days is generally required for spreading lime

mixing of lime and soil.4. The soil lime is compacted to the required maximum dry density.

After compaction, the surface is kept moist for 7 days and then

covered with a suitable wearing coat. Sometimes, the wearing coat is

applied soon after the compaction to help hold the moisture.

STABILIZATION WITH FLYASH

Class C flyash is an industrial by product generated at coal fieldelectricity generating power plants that contains silica, alumina and

calcium based minerals.Upon exposure to water, these calcium

compounds hydrate and produce cementious products similar to the

formed during the hydration of Portland cement. It is therefore more

desirable to mix and compact flyash as quickly as practical.

The hydration property depends on coal source ,boiler design and the

type of ash collection system. The coal source governs the amount andtype of organic matter present in it.Eastern coal source contain small

amount of calcium. This class F flyash does not exhibit self-cementing

characteristics. Western coal contain higher amount of calcium(about

20%-35%)and are classified as class C flyash.

The amount of calcium oxide in flyash is lower than that of lime and

much of it is combined with silicate and aluminates,soflyash has less

effect on plasticity than lime.

Boiler design and operations depends on the rate at which the hydration

occurs .During combustion the inorganic matter is fused consequently

rapid cooling of fused particles occur. So the flyash particles are non-

crystalline in nature.

Compaction time after mixing is crticalto achieve maximum density and

strength. When compaction delayed hydration products begin to bond



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with loose particles and disruption of these aggregations is required to

density the material. So a portion of compactive energy is utilized in

overcoming cementation and maximum densities are reduced.

In flyash the high loss in ignition is due to the presence of unburnt

carbon. The combined amount of silica alumina and ironoxide(84.6%)indicate its suitability as a pozzolanic material .Flyash is

no-plastic in nature. Its moisture condition does not predominantly affect

the dry density. The flyash has high angle of internal friction.

From the grain size distribution on flyash, it is found that it is a fine

grained material and about 86% of the sample passes through 75 micron

sieve indicating that flyash is essentially a silt size material.



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CHAPTER 3

EXPERIMENTAL PROGRAMME

INTRODUCTIONIn this chapter , a brief review of experiments conducted using natural

soil and the stabilized with lime and flyash is explained.

MATERIALS USED

1. Natural soil Soil is brought from near a construction side of Bargarh. Soil over

there is less plastic soil. Therefore the strength of pavement sub

grade needs to be ascertained to withstand the compressive load

Table 1-Properties of soil used in the study:Sl No Properties Values

1 Max. dry density 1517 kg/m3

2 Optimum moisture 23.15

3 Liquid limit 40.1%

4 Plasticity limit 14.67%

5 Plasticity index 25.43

2. Additives The additives used for stabilization and modification include lime

and flyash. The soils were mixed with each of these additives for

which there were reasonable expectations of improved engineering



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properties. The amount of additive used was determined based on

testing the strength for addition of varying percentages and

selecting the one with greatest strength. The lime percentage was

fixed at 8% and flyash 12%.

Physical properties and chemical composition of flyash

Physical properties

Specific gravity 2.36Chemical composition

Silica (SiO2) 58.3%

Aluminium (Al2O3)+Iron oxide (Fe2O3) 26.3%

Calcium oxide (CaO) 2.2%

Magnesium oxide (MgO) 0.3%

LAB TESTINGThe various tests conducted on the sample are the following:

1. Atterberg limits

2. Specific gravity

3. Proctor compaction test

4. CBR Test

Firstly the above tests were conducted on plane soil sample to determine

its properties. Thereafter, certain percentages of lime and flyash areadded to the soil sample to stabilize it. And the percentages of the above

additives which produce the optimum strength to the soil.

Soil preparation





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Specific gravity

The specific gravity of solid particles is defined as the ratio of the mass

of a given volume of solids to the mass of an equal volume of water at

4degree centigrade. Specific gravity of normal soils is between 2.6 to

2.80.Specific gravity of soil mass indicates the average value of all the

solid particles present in the soil mass. Also it is an important parameter

used for the determination of void ratio and particle size. The specific

gravity of the supplied soil was 2.6.

Consistency limits

The consistency of fine grained soil is the physical state in which it

exists. It is used to denote the degree of firmness of soil. The water

content at which soil changes from one state to another is known as

consistency limits.

A soil containing high water in the liquid state. It has no resistance and

can flow like liquid. As the water content is reduced, the soil becomes

stiffer and starts developing resistance to shear deformation. The water

content at which soil changes from liquid state to plastic state is known

as liquid limit. The liquid limit is finding out by Casagrande’s liquid

limit devices. The number of blows of this device is finding out at

0

0.5

1

1.5

2

2.5

0 10 20 30

dry density

dry density



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different water content. Flow curve is plot with number of blows on X-

axis and water content on Y-axis. The water content corresponding to 25

blows is the liquid limit.

Plastic limit is the water content below which the soil stops behaving as plastic material. It begins to crumble when rolled into a thread of soil of

3mm diameter. At this water content, the soil loses its plasticity and

passes to the semi-solid state. The liquid limit, plastic limit and

plasticity index of the soil sample was found to be 36%, 21%, and 15%

respectively.

CHAPTER 4

RESULTS AND DICUSSION

Table 2 Variation of MDD and optimum moisture content and CBR

value with flyash content.

Sl no. Flyashcontent

(%)

MDD(gm/cc) OMC(%) Max.CBR(%)

1 4 1.96 17.5 2.65

2 8 1.94 20.22 10.4

3 12 1.92 23.89 37.06

4 16 1.89 25 24.90

5 20 1.85 28.34 15.1

Table 3 Variation of MDD and optimum moisture content and CBR

value with lime content.

Sl. no Lime

content

MDD

(gm/cc)

OMC

(%)

Max.CBR

(%)



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(%)

1 4 1.73 16.9 2.8

2 8 1.70 19.2 11.6

3 12 1.68 21.37 36.71

4 16 1.63 23.97 26.635 20 1.60 26.63 17.96

GRAPH 1- FLYASH CONTENT VS MDD

GRAPH 2- FLYASH CONTENT VS OMC

1.84

1.86

1.88

1.9

1.92

1.94

1.96

1.98

0 5 10 15 20 25

MDD

MDD



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GRAPH 3- FLYASH CONTENT VS CBR VALUE

GRAPH 4- LIME CONTENT VS MDD

0

5

10

15

20

25

30

0 5 10 15 20 25

OMC

OMC

0

5

10

15

20

25

30

35

40

0 5 10 15 20 25

CBR VALUE

CBR VALUE



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GRAPH 5- LIME CONTENT VS OMC

GRAPH 6- LIME CONTENT VS CBR VALUE

1.58

1.6

1.62

1.64

1.66

1.68

1.7

1.72

1.74

0 5 10 15 20 25

MDD

MDD

0

5

10

15

20

25

30

0 5 10 15 20 25

OMC

OMC



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SUMMARY AND CONCUSIONBased on laboratory tests, the following conclusion have been made:

1. As the locally available borrow soil has generally low plasticity, it

was good to use for construction. The test carried out with

difference proportion of flyash indicated that the workability is

maximum with 12% flyash. Also the dry density observed is

maximum for 12% flyash.

2.

The natural soil used for construction shall be dried with moisturecontent below 4%. If soil has more moisture it is difficult to mix

with flyash. Such soil shall spread on surface and allowed to dry

before construction.

3. It was observed that the addition of lime and flyash greatly reduce

the plasticity characteristics and plasticity index.

0

5

10

15

20

25

30

35

40

0 5 10 15 20 25

CBR

CBR



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4. It was also found that the addition of lime and flyash increases the

bearing capacity of the soil sample.

5. The maximum dry density of soil decreases with lime content may

be due to light weight of lime and soil replaced by lime.

REFERENCES

1.Alhassan, M. (2008). “Potentials of fly Ash for Soil Stabilization”. AU

J.T. 11(4): 246-250

2.Murty A V S R, utilization of fly ash for embankment construction,

proc of experience sharing meet on use of fly ash in roads and

embankment, CRRI New delhi, 1998, 15-20

3.Veerendrasingh, Narendrakumar & Devendramohan, Use of fly ash

stabilization for roads, proc IGC-96,Madras 1996, 411-414

4.Bhoominathan, A. and Ratnakumar, j.(1996), “Lime treated fly ash as

embankment material”, preceeding of Indian Geotechnical conference,

[IGC-96, Madras, pp. 523-526]



5.Eades and Grim, “A quick test to determine lime requirement for lime

stabilization”., Highway research record No-139, Highway research

board, Washington D.C, 1969

Documents

Subgrade Soil Stabilization by Using Flyash and Lime