UNIT-IV-STEERING, BRAKES AND SUSPENSION SYSTEMS.pptx
Stabilization of Soil Using Fly Ash and Lime
1. A
SEMINAR REPORT ON
STABILIZATION OF SOIL USING
N.B. NAVALE SINHGAD COLLEGE OF ENGINEERING
Punyashlok Ahilyadevi Holkar Solapur University
Submitted By
PATIL BALAJI ASHOK
Under The Guidance of
Prof.P.P.Waychal
In Partial Fulfillment of
Bachelor of Civil Engineering
Department of Civil Engineering
NBNSCOE
2023-2024
2. ii
N.B. NAVALE SINHGAD COLLEGE OF ENGINEERING
Certificate
This is to certify that
Mr. Balaji Ashok Patil
Of final year B.Tech in Civil Engineering has successfully
completed the Seminar Report,
Prof.P.P.Waychal Dr. P. P. Tapkire Dr. S. D. Navale
Guide H.O.D Principal
3. iii
ACKNOWLEDGEMENT
I would like to express my sincere gratitude and regards to seminar guide Prof.P.P.Waychal
Sir Department of Civil Engineering ,NBNSCOE for his consistent support and guidance.
I would also like to take this opportunity to thank Dr.P.P.Tapkire Head of CivilEngineering
Department, NBNSCOE for providing us this platform.
I also thank all the Faculties of Civil Engineering Department and my batch matesfor their
support and coordination.
4. ABSTRACT
Soil is the 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
oncoming loads.In such cases,soil stabilization is needeed.Numerous methods are
available in the literature for soil stabilization.But sometimes,some of the methods
like chemical stabilization,lime stabilization etc. adversly affects the chemical
composition of the soil.
In this study,fly ash and lime were mixed with clay soil to investigate the relative
strength gain in terms of unconfined compression,bearing capacity and
compaction.The effect of fly ash and lime on the geotechnical characteristics of
clay-fly ash and clay-lime mixtures was investigated by conductiung standard
Proctor compaction tests,unconfined compression tests,CBR tests and permeability
test.The tests were performed as per Indian Standard specifications.
The following materials were used for preparing the samples:
❖ Clayey soil
❖ Fly ash
❖ Lime
The soft clay used for these experiments was brought from a site,near
Kumarakom.The physical properties of the soil were determined as per IS
specifications.
Fly ash for the study was brought from Hindustan Newsprints,Piravam.it is finely
divided residue resulting from the combustion of ground or powdered coal from
electric generating plants. It has high water absorption capacity.
1
5. Lime for the study is locally available.it imparts much strength to the soil by
pozzolanic reaction which is explained later in the report.
In this test programme,without additives clay was tested to find the optimum
moisture content ,CBR value ,plasticity index and unconfined compression
strength.Fly ash and lime were added in varying percentages and that fraction for
which maximum strength is obtained was found out.The mixture is cured for 3,7 and
14 days.
2
6. 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 preferred modes of transportation and considered as one of the
cost effective modes. An efficient and well-established network of roads is desired
for promoting trade and commerce in any country and also fulfills 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.
Sub grade is the in situ material upon which the pavement structure is placed.
Although there is a tendency to look at pavement performance in terms of pavement
structures and mix design alone, the subgrade soils can often be the overriding factor
in pavement performance. The construction cost of the 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 not adequate for supporting the loads, suitable methods to
enhance the properties of soil need to be adopted. Soil stabilization is one such
method. Stabilizing the subgrade with an appropriate chemical stabilizer (such as
3
7. Quicklime, Portland cement, Fly Ash orComposites) increases subgrade stiffness
and reduces expansion tendencies, it performs as a foundation (able to support and
distribute loads under saturated conditions). This report contains a summary of the
performance of lime and fly ash used with clay.
Fly ashes are finely divided residue resulting from the combustion of ground or
powdered coal from electric generating plants.
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 natural clay brought from Kumarakom.Pavement
subgrade over there is composed of clayey soil whose bearing capacity is extremely
low.Due to this reason ,the roads require periodic maintenance to take up repeated
application of wheel loads.This proves to be costly ,and at the same time, conditions
of raods during monsoon seasons is extremely poor.Therefore, a thought on how to
enhance the stability of roads by chaper means demands appraisal.
Soil stabilization can be done using different additives ,but use of fly ash which is a
waste material from thermal power plants,at the same time difficult-to-dispose
material will be much significant.
4
8. OBJECTIVES OF THE PROJECT
The major objectives of the project are:
1. To explore the possibility of using flyash in road construction programme.
2. To study the effect of lime and flyash on proctor’s density and OMC of clayey
soil.
3. To study the effect of lime and flyash on the consistency limits of clayey soil.
4. To study the changes in CBR of soil by the addition of lime and fly ash
5. To study the effect of curing period on the properties of clayey soil.
5
9. CHAPTER 2
LITERATURE REVIEW
General
Stabilization is the process ofblending and mixing materials with a soil to
improve certain properties of the soil. The process may include the blending of soils
to achieve adesired gradation or the mixing of commerciallyavailable additives that
may alter the gradation, texture or plasticity, or act as a binder for cementationof the
soil.
The process of reducing plasticity and improving the texture of a soil is called soil
modification. Monovalent cations such as sodium and potassium are commonly
found in expansive clay soil and these cations can be exchanged with cations of
higher valenciessuch as calcium which are found in lime and flyash. This ion
exchange process takes place almost rapidly, within a few hours. The calcium
cations 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 clayey soil and improvement
in texture from a cohesive material to a more granular, sand-like soil. The change in
the structure causes a decrease in the moisture sensitivity and increase the
workability and constructability of soil. Soil stabilization includes the effects from
modification with a significant additional strength.
6
10. Soil structure
The clay particles in the soil structure are arranged in sheet like structures composed
of silica tetrahedral and alumina octahedra. The sheets form many different
combinations, but there are three main types of formations .the first is
kaolinite,which consists of alternating silica and alumina sheets bonded together.
This form of clay structure is very stable and does not swell appreciably when wetted
.the next form is montmorillonite, which is composed of two layers of silica and one
alumina sheet creating aweak bond between the layers. This weak bonding between
the layers allows water and other cations to enter between the layers,resulting in
swelling in the clay particle. The last type is illite, which is very similar to
montmorillonite ,but has potassium ions between each layer which help bond the
layers together. Inter layer bonding illite is therefore stronger than for
montmorillonite,but weaker than kaolinite.
Clay particles are small in size but have alarge to mass ratio,resulting in alarger
surface area available for interaction with water and cations.the clay particles have
negatively charged surfaces that attract cations and polar molecules,including water
forming a boundwater layer around the negatively charged clay particles. The
amount of water surrounding the clay particles is related to the amount of water that
is available for the clay particle to take in and release. This moisture change around
the clay particles causes expansion and swelling pressures within clays that are
confined .
7
11. Uses of stabilization
Pavement design isbased on the premise that minimum specifiedstructural quality
will be achieved for each layerof material in the pavement system. Each layermust
resist shearing, avoid excessive deflectionsthat cause fatigue cracking within the
layer or inoverlying layers, and prevent excessive permanentdeformation through
densification. As the qualityof a soil layer is increased, the ability of that layerto
distribute the load over a greater area isgenerally increased so that a reduction in
therequired thickness of the soil and surface layersmay be permitted.
Quality improvement.
The most common improvementsachieved through stabilization includebetter soil
gradation, reduction of plasticity indexor swelling potential, and increases in
durabilityand strength. In wet weather, stabilizationmay also be used to provide a
working platformfor construction operations. These types of soilquality
improvement are referred to as soil modification.
Thickness reduction.
The strength and stiffnessof a soil layer can be improved through theuse of additives
to permit a reduction in designthickness of the stabilized material compared withan
unstabilized or unbound material.
8
12. STABILIZATION TECHNIQUES
Stabitization with portland cement
Portland cement can be used either to modify or improve the quality of the soil into
a cemented mass with increased strength and durability. The amount of cement used
will depend upon whether the soil is to be modified or stabilized.
Cement stabilization is most commonly used for stabilizing silt, sandy soils with
small quantities of silt or clayey fractions stabilization of soil with cement has been
extensively used in road construction. Mixing the pulverized soil and compact the
mix to attain a strong material does this stabilization. The material thus obtained by
mixing soil and cement is known as ‘soil cement’. The soil content becomes a hard
and durable structural material as the cement hydrates and develops strength. The
cementing action is believed to be the result of chemical reaction of cement with the
siliceous soil during hydration.
Stabilization with bitumen
Stabilization of soils and aggregates with asphalt differs greatly from cementand
lime stabilization. The basic mechanism involved in asphalt stabilization of fine
grained soils is a water proofing phenomenon. Soil particles soil agglomerates are
coated with asphalt that prevents or slows the penetration of water, which could
normally result in a decrease in soil strength. In addition, asphalt stabilization can
improve durability characteristics by making the soil resistant to the detrimental
effects of water such as volume. In non-cohesive material such as sand and gravel,
crushed gravel, and crushed stone, two basic mechanisms are active: water proofing
9
13. and adhesion. The asphalt coating on the cohesion less materials provides a
membrane, which prevents or hinders the penetration of water and thereby reduces
the tendency of the material to lose strength in the presence of water. The second
mechanism has been identified as adhesion. The aggregate particle adheres to the
asphalt and the asphalt acts as a binder or cement. The cementing effect thus
increases the shear strength by increasing adhesion. Criteria for design of bituminous
stabilized soils and aggregates are based almost entirely on stability and gradation
requirements. Freeze-thaw and wet durability test are not applicable for asphalt-
stabilized mixtures.
Stbilization with lime-cement and lime-bitumen
The advantages in using combination stabilizers are that one of the stabilizers in the
combination compensates for the lack of effectiveness of the other in treating a
particular aspect or characteristics of a given soil. For instance in clay areas devoid
of base material, lime have been used jointly with other stabilizers notably Portland
cement or asphalt, to provide acceptable base courses. Since Portland cement or
asphalt cannot be mixed successively with plastic clays, the lime is incorporated into
the soil to make it friable, thereby permitting the cement or asphalt to be adequately
mixed. While such stabilization might be more costly than the conventional single
stabilizer methods, it may still prove to be economical in areas where base aggregate
costs are high. Two combination stabilizers are considered in this section.
1. lime-cement
2. lime-asphalt
Lime-cement
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14. Lime can be used as an initial additive with Portland cement or the primary stabilizer.
The main purpose of lime is to improve workability characteristics mainly by
reducing the plasticity of soil. The design approach is to add enough lime to improve
workability and to reduce the plasticity index to acceptable levels. The design lime
content is the minimum that achieves desired results.
Lime-asphalt
Lime can be used as an initial additive with asphalt as the primary stabilizer. The
main purpose of lime is to improve workability characteristics and to act as an anti-
stripping agent. In the latter capacity, the lime acts to neutralize acidic chemicals in
the soil or aggregate, which tend to interfere with bonding of the asphalt. Generally,
about 1-2 percent lime is all that is needed for this objective.
Stabilazation by geo-textiles and fabrics
Introducing geo-textiles and fabrics that are made of synthetic materials, such as
polyethylene, polyester, and nylon, can stabilize the soil. The geo-textile sheets are
manufactured in different thickness ranging from 10 to 300 mils (1mil=0.254mm).
The width of sheet can be upto 10m. These are available in rolls of length upto about
600m.
Geotextiles are permeable. Their permeability is compared to that of fine sand to
course sand and they are strong and durable.
11
15. STABILIZATION WITH LIME
Lime stabilization is done by adding lime to soil. This is useful for the stabilization
of clayey 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 orginal clay, 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 limestone at elevated
temperatures produce quick lime and addition of water to quick lime produces
hydrated lime.
Equation shows the reaction that occurs when limestone is heated to produce quick
lime with carbon dioxide produced as by-product.
CaCO3+heat CaO+CO2
Addition of water to quick lime produces hydrated lime along with heat as
byproduct:
CaO+H2O Ca (OH)2+Heat
12
16. For stabilization with lime,soil conditions and mineralological properties have a
significant effect on the long term strength gain.
Mechanism
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 in the clay particles and calcium from the lime can form a
cemented structure that increases the strength of the stabilized soil. Residual calcium
must remain 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
considered for lime treatment include soils 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 decreases but the plastic limit
increases. Thus the plasticity index of the soil decreases. The strength of the lime
stabilized soil is generally improved. It is partly due to the decrease in the plastic
properties of the soil and 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 sub bases form a water
resistant barrier which stops penetration of rain water. There is an increase in
optimum water content and a reduction in maximum density. In swampy areas where
13
17. the water content is above the optimum, application of lime to soilhelps 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 methods 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 completion of
compaction. However ,care should be taken to avoid carbonation of lime
in the process.
2. Lime may be added in the form of slurry instead of dry powder.
3. A rest period of 1 to 4 days is generally required for spreading lime over
heavy clay before final mixing is done. This facilitates proper 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.
14
18. STABILIZATION WITH FLYASH
Class C flyash is an industrial byproduct generated at coal fired electricity generating
power plants that contains silica,alumina and calcium based minerals.Upon exposure
to water,these calcium compounds hydrate and produce cementitious products
similar to the products formed during the hydration of Portland cement.The rate of
hydration for flyash is much more rapid than 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 and type of organic matter
present in it. Eastern coal source contain small amount of calcium. This class F
flyash does not exhibitself-cementing characteristics. Western coals 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 silicates and aluminates, so flyash has less effect on plasticity than
lime.
Boiler design and operation 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 critical to achieve maximum density and strength.
When compaction is delayed hydration products begin to bond with loose particles
and disruption of these aggregation is required to densify the material. So a portion
of compactive energy isutilized in overcoming cementation and maximum densities
are reduced.
In fly ash the high loss on ignition is due to the presence of unburnt carbon. The
combined amount of silica alumina and iron oxide (84.6%) indicate its suitability as
15
19. a pozzolanicmaterial.fly ash is no-plastic in nature.its moisture condition does not
predominantly affect the dry density. The fly ash has high angle of internal friction.
The grain size distribution of is shown if fig 2. Fly ash is a fine grained material
.about 86% of the sample passes through 75 micron sieve indicating that fly ash is
essentially a silt size material.
16
20. CHAPTER 3
EXPERIMENTAL PROGRAMME
INTRODUCTION
In this chapter, a brief review of various experiments conducted using clay and the
same stabilized with lime and flyash are explained.
MATERIALS USED
1. Clayey soil
Soil is brought from a paddy field in kumarakom.Soil over thereis highly
plastic clay. Therefore the strength of pavement subgrade needs to be
ascertained to withstand the compressive loadunder traffic.
Properties of clay usedin the study:
Sl No: Properties Values
1 CBR value 4.3%
2 Max.dry density 1517 kg/m3
3 Optimum moisture
content
20%
4 Liquid limit 36%
5 Plastic limit 26%
6 Plasticity index 10
17
21. 2.Additives
Theadditives used for stabilization and modification include lime and flyash.
The soils weremixed with each of these additives for which there were
reasonable expectations of improved engineering 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 10% and flyash 14%.
0
20
40
60
80
100
120
0.001 0.01 0.1 1
Particle size distribution for clayey soil
percentage
passing
(%)
18
22. Physical properties and chemical composition of flyash
Physical properties
Specific gravity 2.27
Loss on ignition 11.8%
Chemical composition
Silica (SiO2) 58.3%
Alumina (Al2O3)+Iron oxide
(Fe2O3)
26.3%
Calcium oxide (CaO) 2.2%
Magnesium oxide (MgO) 0.3%
LAB TESTING
The various tests conducted on the sample are the following:
1.Atterberg limits
2. Specific gravity
3. Direct shear test
4. Proctor compaction test
5. CBR test
6. Unconfined compression test(UCS)
19
23. Firstly the above tests were conducted on plane clay sample to determine its
properties.UCS test is conducted to evaluate it strength. Thereafter, certain
percentages of lime and flyash are added to the clay sample to stabilize it. And the
percentages of the above additives which produce the optimum strength to the soil
are chosen by conducting UCS test on them.
Soil preparation
The soil was collected from site in large sacks. It is brought to the lab and is dried
in oven for 24 hours in large pans. This soil due to loss of water formed big lumps
which is broken to smaller pieces or even fine powder and is sieved according to
the needs of different experiments.
Compaction test
Compaction is the densification of soil by reduction of air voids. The purpose of a
laboratory compaction test is to determine, the quantity of water to be added for
field compaction of soil and resultant density expected. When water is added to
dry fine grained soil, the soil absorbs water. Addition of more water helps in
sliding of particles over each other. This assists the process of compaction. Up to a
certain point, additional water helps in reduction of air voids,but after a relatively
high degree of saturation is reached, the water occupies the space ,which could be
filled with soil particles, and the amount of entrapped air remains essentially
constant.Therfore,there is an optimum amount of water for a given soil and
compaction process, which give rise to maximum dry density.
Compaction of clay,clay-lime and clay-flyash mixtures were carried out using
standard proctor test with three layers on each 25 blows. Samples for conducting
20
24. compaction tests were prepared using moulds of dimensions 10 cm diameter and 15
cm height. In this study, lime is added for about 10% and cured for 3, 7, and 14
days. Also,flyash is added for about 14% and is cured for 3,7 and 14 days. The
values of optimum moisture content and maximum dry density are obtained in a
plot of dry density versus moisture content.
Unconfined compression test
This test is conducted on undisturbed or remoulded cohesive soils that are
normally saturated.This test may be considered as a special case of triaxial
compression test when the confining pressure is zero and the axial compressive
stress only is applied to the cylindrical specimen. The stress may be applied and the
deformation and load readings are noted until the specimen fails. The area of cross
section of specimen for various strains may be corrected assuming that the volume
of the specimen remains constant and it remains cylindrical. The following
equations were used:
Axial strain (𝜀) =∆L/L0
L0=initial length of sample (cm)
Corrected area of cross section (A) =A0/1-𝜀
A0=initial area of cross section of the sample (cm2
)
Axial stress (qu) =P/A (kg/cm2
)
P=axial load (kg)
Graphs are plotted between axial strain(𝜀) Vs axial stress(qu),% of flyash and
lime Vs axial stress and curing period VS axial stress. The maximum value of axial
stress is the unconfined compressive strength of soil sample.
21
25. Samples for conducting unconfined compression test were prepared using
moulds of dimensions 10cm diameter, 20cm height. Soil sample without additives
were tested to find out the optimum moisture content based on compressive stress.
In this study flyash is added in 12% and 14% and lime 5% and 10% respectively.
The stress is applied and the deformation and load readings are noted until the
specimen fails. The maximum axial strain is noted.
California bearing strength
Califonia state highway department developed the California bearing ratio test
,(CBR)test in 1938 for evaluating soil subgrade and base course materials for
flexible pavements. Just after World War 2,the U.S corps of Engineers adopted the
CBR test for use in designing base courses for airfield pavements.
California bearing ratio(CBR) is the ratio of force per unit area required to
penetrate a soil mass with a standard circular piston at the rate of 1.25 mm/min to
that required for corresponding penetration in the standard material. Load that has
been obtained from the test in crushed stone(Standard material) is called standard
load. The standard material is said to have a CBR value of 100%.Smooth curves are
plotted between penetration (mm) Vs load (kg).The curve in most cases is concave
upwards in the initial portions.A correction is applied by drawing a tangent to the
curve at the point of greatest slope from the corrected load penetration graph
obtained the loads at 2.5mm and 5mm penetration. The standard loads for these
penetrations can be taken from he table below:
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26. Standard loads for CBR tests
Penetration depth (mm) Standard load (kg) Unit load (kg/cm2
)
2.5 1370 70
5.0 2055 105
7.5 2630 134
10 3180 162
12.5 3600 183
CBR value= (Test load/Standard load) X100
Samples for conducting CBR tests were prepared using moulds of dimensions
15cm diameter and 17.5cm height. The weight of soil used is 5kg passing through
20mm sieve. The samples were prepared at OMC and varying lime and flyash.In
this study, lime is added at 10% and fly ash at 14%.
Direct shear test
The shear strength of a soil is its maximum resistance to shear stresses just before
the failure. Shear failure of a soil mass occurs when the shear stresses induced due
to the applied compressive loads exceed the shear strength of the soil. Failure in soil
occurs by relative movements of the particles and not by breaking of particles.
23
27. Shear strength is the principal engineering property which controls the stability of
the soil mass under loads. Shear strength determines bearing capacity of soils,
stability of slopes of soils, earth pressure against retaining structure etc.
Direct shear test is conducted on a soil specimen in a shear box which can split into
two equal halves and is covered with porous grid plates on either sides. Normal load
is applied for a constant stress and shear load is applied at a constant rate of 0.02
mm/minute. The test is repeated for different stress and failure stress is noted.
A failure envelope is obtained by plotting shear stress with different normal stress
and is joined to form a straight line from which angle of shear resistance and
cohesion is obtained.
Specific gravity
The specific gravity of solid particles is defined as the ratio of the mass of a given
volume of solids to the mess of an equal volume of water at 40
C. Specific gravity
of normal soils is between 2.65 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.
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 is in the liquid state. It has no shear resistance
and can flow like liquid. Therefore the shear strength is equal to zero. 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
24
28. state is known as liquid limit. The liquid limit is find out by Casagrande’s liquid
limit device. The number of blows of this device is find out at 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 stop behaving as a 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
shear strength at the plastic limit ,is about 100 times that at the liquid limit.
25
29. CHAPTER 4
RESULTS AND DISCUSSIONS
The following chapter covers the results of the testing programmes. The
results that are presented include soil properties admixture percentages and the
various testing results for the soil additive combinations .
Native soil properties and admixture percentages
Soil chacterstics were determined using atterberg limits ,hydrometer analysis,
specific gravity, standard proctor compaction and unconfined compression tests.
The test results is shown the table
Sl No: Properties Values
1 CBR value 4.3%
2 Max.dry density 1517 kg/m3
3 Optimum moisture
content
20%
4 Liquid limit 36%
5 Plastic limit 26%
6 Plasticity index 10
26
30. The grain size dirtribution curve for the soil used is shown in figure.
The percentage of lime and fly ash for stabilization is determined from the
unconfined compression test. The test results are shown.
The native soil has an unconfined compression of 400kpa. This increased by the
addition of lime and fly ash. The maximum strength is obtained by the addition of
10% lime and 14% fly ash.Atterberg limits
0
20
40
60
80
100
120
0.001 0.01 0.1 1
Particle size distribution for clayey soil
percentage
passing
(%)
400
1950
2250
1800
1950
native soil lime 5% lime 10% fly ash 12% flyash 14%
27
31. The atterberg limit test results with various soil additive combination at different
curing period are presented in the table and graphs showing variation of atterberg
limits with curing period is plotted for different soil-additive combination.
Atterberg test results on clay-flyash-lime mixture
Curing period Liquid limit Plastic limit Plasticity index
Native soil 36 26 10
Lime:3 days 25 15 10
7 days 23 18 10
14 days 22 20 5
Flyash:3 days 35 19 16
7 days 35 23 12
14 days 35 26 9
0
5
10
15
20
25
30
0 5 10 15
liquid limit
plastic limit
plastcity index
curing period (days)
water
content
(%)
clay-lime mixture
28
32. The native liquid limit and plasticity index of the soil were 36 and 10. The PI
values were reduced when they are mixed with small amout of lime and became
nonplastic with the addition of more lime.For clay-lime mixture, the 3 day liquid
limit is 25, it reducese to 23 for 7days and it becomes 22 at 14days. The plastic
limit is increases from 15 at 3day to 20 at 14 days.As the liquid limit decreases and
plastic limit increases the plasticity index decreases from 10 to 5 with curing
period.
For fly ash had more limited effect on the plasticity ofthese soils.The liquid limit
remains constant with curing period for the fly ash-clay mixture.The plastic limit
increases from 19 at 3day to 26 at 14days, as a liquid limit remains constant and
plastic limit increases, the plasticity index values decreases from 16 at 3days to 9 at
14 days.
0
5
10
15
20
25
30
35
40
0 5 10 15
liquid limit
plastic limit
plasticity index
water
content
(%) clay-fly ash mixture
29
33. MAXIMUM DENSITY AND OPTIMUM MOISTURE CONTENT
Optimum moisture content and maximum density for native soil and each of the
soil additive combination at different curing period is presented in the table and the
variation of maximum density and optimum moisture content is plotted
Sl no: Water content Dry density
1
18 1490
2
20 1517
3
22 1467
4
24 1427
Moisture-density relationship for clay-flyash mixtures
3 days curing 7 days curing 14 days curing
Water
content
Dry density Water
content
Dry density Water
content
Dry density
17.1 1370 14.8 1260 13.3 900
17.6 1420 15.3 1300 14 1130
18.9 1490 16 1350 14.9 1000
20.1 1380 17.2 1310 15.6 870
20.5 1360 18 1250 15.9 900
30
34. Moisture-density relationship of clay-lime mixtures
3 days curing 7 days curing 14 days curing
Water
content
Dry density Water
content
Dry density Water
content
Dry density
22 450 24 390 24 150
23 590 25 410 26 200
24 645 26 445 28 235
25 555 27 390 30 200
26 490 28 300 32 159
0
500
1000
1500
2000
2500
0 10 20 30 40
native soil
flyash 3days
flyash 7days
flyash14days
ZAV
water content(%)
dry
density(kg/cm
3
)
moisture-density relationship for flyash
clay mixture
31
35. The maximum density and optimum moisture content for the native soil are
1517 kg/m3
and 20%. When mixed with fly ash the optimum moisture content and
the maximum density is decreased.The maximum density is 1490 kg/m3
at an
optimum moisture content of 18.9 % at 3 days.It is reduces to 1000kg/m3
at an
optimum content of 14.9% in 14 days. So both the maximum density and optimum
moisture content decreases for fly ash-clay mixture.
When mixed with lime, the optimim moisture content is increased and the
maximum dry density is decreased.The maximum density is 645 kg/m at an
optimum moisture content of 24% in 3 days.In 7days the maximum density is 445
kg/m3
at an optimum moisture content of 26%.The maximum density is decreased
to 235 kg/m3
and optimum moisture content increased to 28%.
0
500
1000
1500
2000
2500
0 10 20 30 40
native soil
lime 3 days
lime 7 days
lime 14 days
ZAV
water content(%)
moisture-density relationship for
lime-clay mixture
32
36. DIRECT SHEAR TEST-FLYASH
3 days
curing
7 days
curing
14 days curing
Normal
stress
(kg/cm2
)
Shear
stress
(kg/cm2
)
Shear
stress
(kg/cm2
)
Shear stress (kg/cm2
)
Native soil
0.5 0.497
1 0.789
1.5 0.99
Lime:
0.5 0.569 .72 0.99
1 .897 1.074 1.24
1.5 1.2 1.33 1.45
Fly ash:
0.5 0.569 0.581 0.695
1 0.91 0.998 1.01
1.5 1.07 1.264 1.314
0
0.2
0.4
0.6
0.8
1
1.2
1.4
0 0.5 1 1.5 2
3 days curing
7 days curing
14 days curing
Native soil
shear
stress
(kg/cm
2
)
direct shear test:
fly ash
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
0 0.5 1 1.5 2
3 days
curing
7 days
curing
14 days
curing
normal stress
(kg/cm2)
shear
stress
(kg/cm
2
)
33
37. The direct shear stresses of native soil for normal stress 0.5 kg/cm2
is
0.497kg/cm2
.When mixed with fly ash the direct shear stress increases to 0.569 for
3days curing, 0.581 for 7days curing and 0.695 kg/cm2
for 14days curing.
When mixed with lime, the direct shear stress increases to 0.569 for 3days
curing, 0.72 for 7days curing and 0.99kg/cm2
for 14 days curing.
CALIFORNIA BEARING RATIO TEST
Load penetration graph for native soil is given below:
Penetration (mm) Load (kg)
0
0
0.5
3.39
1
8.48
1.5
21.2
2
38.16
2.5
59.36
3
69.536
4
82.256
5
86.496
7.5
107.696
10
117.872
12.5
124.656
34
40. CHAPTER 5
CONCLUSION
1. Lime acts immediately and improves various property of soil such as
carrying capacity of soil, resistance to shrinkage
2. during moist conditions, reduction in plasticity index, increase in
CBR value and subsequent increase in the
3. compression resistance with the increase in time.
4. The reaction is very quick and stabilization of soil starts within few
hours.
5. The graphs presented above give a clear idea about the improvement in
the properties of soil after adding lime.
REFERENCES
1. Chaddock, B. C. J., (1996), “The Structural Performance of Stabilized
Road Soil in Road Foundations,” Lime stabilization.
a. Thomas Telford.
2. Evans, P., (1998). “Lime Stabilization of Black Clay Soils in
Queensland, Australia,” Presentation to the National Lime Assoc iation
Convention,
3. San Diego, California.
4. Graves, R. E., Eades, J. L., and Smith, L. L., (1988). “Strength Developed
from Carbonate Cementation of Silica-Carbonate Base Course
Materials,”
5. Transportation Research Record No.1190
37
