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THESIS SUBMITTED IN THE PARTIAL FULFILLMENT OF THE REQUIREMENT FOR THE AWARD OF THE DEGREE
OF
MASTER OF CIVIL ENGINEERING
IN SOIL MECHANICS AND FOUNDATION ENGINEERING.
By
GOURHARI BISWAS
EXAM ROLL NO- M4CIV10-12.
Under The guidance of
Prof. S.Chakborti &
Prof. S.P.Mukherjee
Department of Civil Engineering Faculty of Engineering & Technology
Jadavpur University Kolkata-700032
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Department of Civil Engineering Faculty of Engineering & Technology
Jadavpur University
CERTIFICATE OF APPROVAL* The foregoing thesis is hereby approved as a creditable study of an
engineering subject carried out and presented in a manner satisfactory to
warrant its acceptance as a pre-requisite to the degree for which it has been
submitted. It is understood that by this approval the undersigned do not
necessarily endorse or approve any statement made, opinion expressed or
conclusion drawn therein, but approve the thesis only for the purpose for
which it is submitted.
FINAL EXAMINATION FOR 1.
EVALUATION OF THESIS
2.
3.
(Signatures of Examiners)
*Only in case the thesis is approved.
Department of Civil Engineering
Faculty of Engineering & Technology
Jadavpur University
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Certificate
We hereby recommend that the thesis prepared under our supervision by
Gourhari Biswas, entitled SOME STUDIES ON STABILIZATION OF
SUBGRADE OF FLEXIBLE PAVEMENT WITH RICE HUSK, RICE HUSK ASH AND
LIME be accepted in partial fulfillment of the requirement for the Degree
of Master of Civil Engineering in Soil Mechanics & Foundation
Engineering from Jadavpur University.
In-Charge of Thesis
Countersigned:
Head of the Department:
(Civil Engineering Department)
Dean:
(Faculty of Engineering & Technology)
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ACKNOWLEDGEMENTACKNOWLEDGEMENTACKNOWLEDGEMENTACKNOWLEDGEMENT
I am extremely thankful and indebted to Prof. S.Chakraborti, Head, Civil Engineering
Department and Prof. S.P.Mukherjee, Section-in-Charge, Soil Mechanics & Foundation
Engineering Division of Civil Engineering Department, Jadavpur University, for their
valuable guidance, constant support and encouragement throughout my thesis work.
I also express my gratitude to all the faculty members of civil engineering department of
Jadavpur University for their encouragement and moral support extended throughout my
thesis work.
I sincerely acknowledge the help from Mr. Rabin Pal, Mr. Apurba Banerjee and Mr. Ranjit
Kushari, Laboratory Technical staffs of Soil Mechanics Laboratory and Mr. Debasis of
Road Materials Laboratory and laboratory attendants Brindaban Naskar and Basudev
Goari of soil Mechanics laboratory of Civil Engineering Department, Jadavpur University,
Kolkata.
I am grateful to my family members, specially my wife and my sons for being with me in
the hard time that was needed to complete this thesis.
Last but not the least, I express my heartfelt thanks to all of my classmates, Soil Mechanics
and Foundation Engineering section, whose friendship, cooperation, and suggestions
have helped me to complete this thesis work .
Kolkata
GOURHARI BISWAS (ROLL NO 000810402013).
EXAM. ROLL NO : M4CIV-10-12.
DEPARTMENT OF CIVIL ENGINEERING.
FACULTY OF ENGINEERING &TECHNOLOGY.
JADAVPUR UNIVERSITY
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Abstracts
With the increase in road construction activities under different Govt.
schemes, an intense need has been arisen to economize the cost of
construction. As the subgrade supports the road pavements and the load
coming from the moving vehicles, improving the quality of natural weak
subgrade to enhance its strength and load bearing capacity and other
engineering properties as well will be a most essential part of economizing
construction activities.
The quality of a pavement depends on the strength of its sub-grade. The
subgrade, the layer of soil on which the pavement is built, acts as a support
for the entire pavement system. In case of the flexible pavement the sub-
grade must be uniform in terms of geotechnical properties like shear
strength, compressibility etc. Materials selected for use in the construction of
sub-grade must have to be of adequate strength and at the same it must be
economical for use. The materials selected must also be ensured for the
quality and compaction requirements. If the natural soil is very soft it needs
some improvement to act as a sub-grade. It is, therefore, needed to replace
the natural soil by stabilization with improved strength and compressibility
characteristics.
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The paper highlights the effect of stabilization of low strength cohesive
soil with admixture of different materials like Rice Husk Ash, lime etc, which
are cheap and easily available.
The present investigation has been carried out with agricultural waste
materials like Raw Rice Husk (RRH) and Rice Husk Ash (RHA) individually
mixed with soil and also in combination with different percentage of Hydrated
Lime with several mix proportions to study improvement of weak road
subgrade. 5,10,15 and 20 percentages of RHA were mixed with soil
stabilized with 3,6,9,12 and 15 percentage of lime in different combinations
and also 2,3,4,5 and 6 percentage of RRH were mixed with soil stabilized
with 6,9 and 12 percentage lime in several combinations and compacted at a
water content of OMC+5% and tested for California Bearing Ratio(CBR) and
Unconfined Compressive Strength(UCS) tests. The results show marked
improvement in CBR & UCS values of the mixed soils in comparison with that
of the original soil. The high percentage of siliceous materials present in RHA
promises it to be used as a potential ground stabilizing/improving materials.
The effect of curing of specimens were also investigated. It has been found
that with increase in curing period UCS values as well as CBR value of lime
RHA stabilized soil as well as lime RRH stabilized soil are increasing
remarkably.
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.
The main testing parameters selected for evaluation of improvement
and or comparison with that of the original properties of soil
were CBR tests (both soaked and unsoaked) and Unconfined Compressive
strength test as the CBR values give the most reliable information about the
quality of subgrade and its strength characteristics and UCS values give the
information about the effectiveness of stabilization. As a general rule for a
given type of stabilization, the higher the compressive strength and CBR
values the better is the quality of stabilized and compacted materials
The results of the test experiments promise not only RRH and RHA may be
used as a potential ground improving materials but also to reduce partially
the disposal hazard of waste material like RRH and RHA.
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CONTENTS
TOPICS PAGES
Chapter One: Introduction 1-2
Chapter Two: Review of Literature 3-9 2.0 General 3
2.1 Literature Review on use of Rice Husk Ash 3 2.2 Literature Review on Use on Raw Rice Husk (RRH) 8
Chapter Three : Materials Used 10-15 3.1 Soil 10
3.2 Lime 11 3.3 Rice husk 12
3.4. Rice husk ash 14
Chapter Four : Objective and scope of the work 16-17 4.1 Objectives 16
4.2. Scopes 16
Chapter Five : Test program 20-23 5.0 General 20 5.1 Test Program 20
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Chapter Six : Test procedures 24-25 6.0- General 24 6.1 Name of the tests and the relevant IS code 24
Chapter Seven : Presentation of test results 26-145 7.0 General 26 7.1- Evaluated geotechnical properties of Original Soil 26 7.2. Results for Characterization test of stabilized soil 28 7.3 Compaction characteristics of Unstabilized and
stabilized soil 38
7.5 Strength characteristics of soil 65
7.6 Comparison of CBR test results with cured and
uncured specimens 139
7.7 Effect of curing on strength properties of soil 141
Chapter Eight : Interpretation of test results 146-164 8.0 General 146 8.1- Characteristics of original Soil 146
8.2 Characterization of unstabilized as well as
stabilized soils 147
8.3 Compaction Characteristics of Stabilized Soil- 150
8.3.1 Effect of Lime addition on Compaction
Characteristics of soil 150
8.3.2 Effect of RHA addition on Compaction
Characteristics of soil 151
8.3.3Effect of Lime and RHA addition on
CompactioCharacteristics of soil 151
8.3.4 Effect of RRH addition on Compaction
Characteristics of soil 151
8.3.5 Effect of Lime and RRH addition on
Compaction Characteristics of soil 152
8.4 Strength characteristics of Stabilized soil 152
8.4.0-General
8.4.1 Effect of Lime addition on strength
characteristics of soil 153
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8.4.1.1-Effect on CBR 153
8.4.1.2-Effect on UCS 153
8.4.2 Effect of RHA addition on strength
characteristics of soil 154
8.4.2.1-Effect on CBR 154
8.4.2.2-Effect on UCS 155
8.4.3 Effect of RHA Lime addition on strength
characteristics of soil 155
8.4.3.1-Effect on CBR 155
8.4.3.2-Effect on UCS 156
8.4.4 Effect of RRH addition on strength
characteristics of soil 157
8.4.4.1-Effect on CBR 157
8.4.4.2 Effect on UCS 158
8.4.5 Effect of RRH Lime addition on strength
characteristics of soil 158
8.4.5.1 Effect on CBR 158
8.4.5.2. Effect on UCS 160
8.5 Effect of Curing on Strength properties of soil 161
8.5.1 Effect of Curing of specimens on CBR values
8.5.2 Effect of Curing of specimens on UCS values 161
8.6 Comparison of test results and evaluation
of Improvement 162
8.7Effect of admixtures on deformation
pattern of specimens 164
Chapter nine : Summary and conclusion 165-168 9.0; - General 165 9.1 Summary 165 9.2 Conclusions 166 9.2.1- Use of Lime 166 9.2.2-Use of Rice Husk Ash (RHA) 166 9.2.3 Use of Raw Rice Husk (RRH) 167
9.3- Addition of Lime with RHA and RRH 167
9.3.1. Addition of Lime with RHA 168
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9.3.2. Addition of Lime with RRH 168
Chapter Ten : Scope of future work 170-171 10.1 General 170
10.2 Scopes for future work 170
References 172-174
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CHAPTER ONE
INTRODUCTION
Soils are deposited or formed by nature under different environmental conditions. Man
does not have any control on the process of soil formations. As such soil strata at a site
are to be accepted as they are and any construction has to be adapted to suit the subsoil
conditions. The existing soil conditions at a given site may not be suitable for supporting
the desired facilities such as buildings, bridges, dams, roads and so on because the safe
bearing capacity of a soil may not be to support the given load. Here comes the need to
explore possibilities for improving the existing soft/weak ground by adopting different
artificial means.
Geotechnically soil improvement could either be by modification or stabilization or both.
Soil modification is the addition of a modifier (lime, cement etc.) to a soil to
change/improve its engineering properties, while soil stabilization is the treatment of soils
to enable their strength and durability to be improved such that they become totally
suitable for construction beyond their original classification.
Ground improvement in soil in soil has five major functions:
To increase the bearing capacity of weak soil
To control deformations and accelerate consolidations
To provide lateral stability
To form seepage cut-off and environment control
To increase resistance against liquefaction
These functions can be accomplished by modifying the grounds character with or without
the addition of foreign materials. Improving the ground at the surface is Usually easy to
accomplish and relatively inexpensive. When at depth, however, the task becomes more
difficult, usually requiring more rigorous analysis and the use of specialized equipments
and construction procedures.
Several methods of soil improvement using pozzolanic materials have been developed
and used successfully in practice. It has been applied in a variety of civil engineering
works, like in the construction of base courses where good materials are not economically
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available, for reducing the permeability and compressibility of soils in hydraulic and
foundation works, for stabilization of slopes, embankments and excavations. Due to rapid
industrialization throughout the world the production of huge quantity of waste materials
create not only the environmental problem but also depositional hazards. Safe disposal of
the same is a very vital issue and such situation can be addressed by the bulk utilization
of these materials mainly in the field of civil engineering applications. In recent years the
use of various waste products in civil engineering construction has gained considerable
attention in view of the shortage and high costs of conventional construction materials, the
increasing costs of waste disposal and environmental constraints. A considerable amount
of research works concerning stabilization of soil with additives such as cement, lime, fly
ash bitumen etc is available in the literature. But soil stabilization with lime and rice husk
ash or lime and raw rice husk is relatively a new method, specially lime and raw rice husk
stabilization a completely new idea.
In recent times the demand for suitable subgrade materials has increased due to
increased constructional activities in the road sector and also the paucity of nearby lands
to allow to excavate fill materials for making subgrade .Again soft soil deposits are
problematic and needs large scale displacement to facilitate road construction works.
Such mass replacement methods which are cost and labour intensive can be avoided if
the poor soil is being improved or modified in situ and reused as road construction
materials. Different alternative generated waste materials which cause not only
environmental hazards but also the depositional problems. Some of these materials can
be economically and suitably used as admixtures or stabilizers for improving soft or weak
soil so as to make it fit for use as road subgrade materials. The modified soft to be used
for road construction work should be in line with the practice of engineering in an
environment friendly and sustainable way.
Over the years the two main materials for stabilizing, lime and cement have rapidly
increased in costs. The over dependence on the industrially manufactured soil improving
additives (cement, lime etc.) have kept the cost of construction of stabilized road
financially high. The use of agricultural wastes (such as Rice Husk, Rice Husk Ash etc.)
will considerably reduce the cost of construction and also the environmental and disposal
hazards they cause.
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CHAPTER TWO
REVIEW OF LITERATURE
2.0 General:-
In this chapter an attempt has been made to present a review of past works carried out so
far by different researchers on the relevant topic. The works on Rice Husk Ash and Raw
Rice Husk ash as soil stabilizing materials are reported in the following section in
chronological order. Although a number of researchers have attempted soil stabilization
with Rice Husk Ash but soil stabilization with Raw Rice Husk is almost an unexplored field
specially the combined use of raw rice husk and lime for soil stabilization.
2.1 Literature Review of Use on Rice Husk Ash (RHA)
Brooks et al (2009) carried out experiments to study the effect of mixing RHA and fly ash
with expansive soil in an effort to upgrade it as a construction material. He investigated the
potential of RHA-fly ash blend as a swell reduction layer between the footing of a
foundation and road subgrade. A cost comparison was also made for the preparation of
the sub base of a highway project with and without the admixture stabilizers. From his
experimental work he came to the following conclusion:
1. Stress strain behavior of unconfined compressive strength showed that failure stress
and strains increased by 106% and 50% respectively when the flyash content was
increased from 0 to 25%.
2. When the RHA content was increased from 0 to 12%, Unconfined Compressive Stress
increased by 97%.
3. When the RHA content was increased from 0 to 12%, CBR improved by 47%.
4. The optimum RHA content was found at 12% for both UCS and CBR tests.
Okafor et al (2009) performed laboratory experiments to study the effects of RHA on
some geotechnical properties of a lateritic soil to be used for subgrade. Their investigation
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included evaluation of properties such as compaction, consistency limits and strength of
the soil with RHA content of 5%, 7.5%, 10%, and 12.5%y soil. They concluded as follows:
1. The soil was classified to be A-2-6(0) or well-graded sand (SW).
2. RHA increased the OMC but decreased the MDD of the soil.
3. The increase in RHA content decreased the plasticity index of the soil. This confirms
that
the activity of the mixture reduced with the addition of RHA.
4. The addition of RHA increased the volume stability of the soil.
5. The addition of RHA improved the strength property (CBR) of the soil.
6. 10% RHA content was observed to be the optimum content for the lateritic soil.
7. From the foregoing investigation it would appear that RHA perform satisfactorily as a
cheap stabilizing agent for lateritic soil for sub-grade purposes.
Alhassan(2008) carried out extensive laboratory experiments to investigate the effect of
lime and RHA on permeability and strength properties of lateritic soils. In his experiments
A-7-6 lateritic soil(CH) was treated at British Standard Light (BSL) compaction energy with
upto 8% lime content (by dry weight of soil) at 2% variations and each was admixed with
upto 8% RHA at 2% variations. Effects of the ash on the soil lime mixtures were
investigated with respect to Unconfined Compressive Strength (UCS) and coefficient of
permeability. The UCS of the specimens increased with increasing RHA content at
specified lime contents to their maximum values at 6% RHA and also the coefficient of
permeability of cured specimens decreased with increase in ash content to their minimum
values at 6% RHA content and beyond this point the permeability rises slightly. His
findings indicate that no more than 6% RHA can be used to increase UCS and reduce
permeability of lateritic soil.
Alhassan(2008) again carried out experiments to study the effect of stabilizing A-7-6
lateritic soil(CH) with 2-12% RHA by weight of dry soil. CBR and UCS tests were
conducted for the soil RHA composites. The results obtained indicate a general decrease
in the maximum dry density and increase in optimum moisture content. There was also
slight improvement in the CBR and UCS values with increase in RHA content. Peak UCS
values were recorded at between 6-8% RHA content, indicating a little potential of using 6-
08% RHA for strength improvement of A-7-6 lateritic soil.
Roy et al (2008) carried out experiments to study the effectiveness of utilization of RHA
and pond ash for improving subgrade for road construction. They have conducted tests on
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mixed soils with different proportion of pond ash to find out the effect of mixing RHA on
CBR values of mixed soil. Their findings were as follows : addition of pond ash or RHA
shows a considerable effect on compaction characteristics of alluvial soil. MDD of mixed
soil decreases with increase in added percentage of either of pond ash or RHA and OMC
increases. Soaked CBR increases to a very high value i.e. about three times when RHA
and pond ash is mixed with virgin soil at the rate of 20% respectively.
From their experimental studies on effect of mixing various percentage of pond ash and
RHA to an alluvial soil they have concluded that when 20% of pond ash and 20% RHA
are mixed to the virgin soil by weight composite mix shows the maximum increase in CBR
values by around 200% with simultaneous maximum decrease in plasticity index.
Roy et al (2008) made an experimental study to explore the possibility of improving the
engineering properties of alluvial soil utilizing waste materials like pond ash and rice husk
ash and a little quantity of cement. Their experimental results indicated that significant
improvements in the index properties and CBR values specially soaked CBR value of
alluvial soil can be achieved by mixing alluvial soil with pond ash and rice husk ash and
the most cost effective proportion to the above mix was found to be 20:40:40.Further
experiment with addition of cement to the mix of above combination in 20:60:20 can
improve the soaked CBR to the largest increase and this proportion can use maximum
alternative materials attaining soaked CBR value the highest degree.
Hussain(2008) carried out research work on Influence of pozzolans on mechanical
properties of cement column. Ground settlement is one of the major crisis in Bankok due
to low bearing capacity of soft clay soil, causing problems of low stability and high
settlement. This problem can be overcome by cement columns when part of the port land
cement was replaced by pozzolans. His research also focuses on finding an effective mix
design that may be used on construction of cement columns by slurry mixing with
optimum water cement ratio.
The test results showed that soft clay treated with cement and a combination of cement-
pozzolans improved the stability and settlement of the ground by increasing the bearing
capacity and shear strength of the treated soil. The unconfined compressive strength has
improved with replacing definite amount of cement by pozzolans at higher binder contents
(200kg/m3) while showed a decreasing strength with increasing pozzolans percentage at
lower binder content (100 kg/m3). The setting times of cement column were found to be
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significantly delayed as compared with those of cement paste. Moreover soil-cement
treatment with pozzolans used in this study further delayed the setting times. The highest
strength was achieved by replacing 25% of cement to rice husk ash type-I at a binder
content of 200kg/m3, while cement-fly ash combination was found to be the most
economical binder for deep mixing methods giving 30-40% replacement of cement to fly
ash at binder content of 200 kg/m3. The mechanical properties of treated clayey soil were
greatly influenced by the presence of pozzolans. Different pozzolans gave different
strength at different percentage replacement of cement. Cement in combination with fly
ash was found to be the most economical binder for deep mixing methods.
Jha et al(2006) carried out series of experiments to evaluate the effectiveness of using
RHA as a puzzuolanae to enhance the lime treatment of soil. They studied the influence of
different mix proportions of lime and RHA on compaction, strength properties, CBR values
and durability characteristics of soil. Their results show that addition of RHA enhances not
only the strength development but also the durability of lime stabilized soil. They have
also found that addition of lime and RHA to soil increases the OMC of mixed soil and
reduces the MDD. Adding RHA enhances the development of UCS of lime stabilized soil.
Curing period and temperature has a significant effect on on development of UCS when
RHA ios added to lime stabilized soil. As the curing time and temperature increases the
rate of strength gain is intensified by addition of RHA. Durability of lime stabilized soil is
enhanced by addition of RHA. Addition of RHA increases the CBR value considerably for
both soaked and unsoaked conditions.
Muntohar(2005) conducted laboratory experiments to study the influence of anount of
water available for the Lime RHA pozzolanic reaction. He founded that the strength gain of
stabilized soils is not only influenced by the type and proportion of the stabilizers and its
curing time, but also by the water content needed to maintain the reaction. The lime RHA
reaction being pozzolanic will be greatly influenced by the amount of water to react with
admixtures apart from the proportions of admixtures. His paper presents the results of a
laboratory study on the UCS of soils stabilized with lime and RHA compacted at OMC
and at wet and dry side of OMC. The results show that the water content determines the
UCS characteristics of stabilized and unstabilized soils. The UCS of unstabilized soil is
affected by the density or unit weight of the compacted soil and the molded moisture
content. The UCS of stabilized soil decreases with increasing molding water content but it
is still higher than that of the unstabilized soils. Higher lime content results to a higher
UCS value. Maximum strength of the stabilized soil is attained at Lime/RHA ratio of .
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The UCS of the stabilized soil increases significantly about 7-9 times to the unstabilized
UCS.
Muntohar(2002) carried out a series of laboratory experiments individually and in
combination of RHA and lime in stabilizing expansive soils in Indonesia. He found that the
geotechnical properties of expansive soils improved with addition of RHA and lime. RHA
and lime altered thew texture of clay soil by reducing the fine particles. The admixtures
also found to reduce the liquid limit, swelling [potential of expansive soils and also the
compressibility characteristics . The CBR value enhances with the addition of admixtures.
Ten percent lime content produced brittle failure under compression whereas soil treated
with combination of RHA and lime reveled a ductile behavior but the strength increased
marginally.
Sivapulliah et al(2004) investigated the possibility of using RHA as a cushion below the
footing in expansive soil. Placing a cushion below the expansive soil and foundation is an
attractive proposal for overcoming the problem associated with construction of structures
over expansive soils such as Indian black cotton soils. Extensive studies on cohesive non
swelling soil as a cushion have shown that it is ineffective over cycles of swelling and
shrinkage of soil. They have found that RHA stabilized with 3-9% of lime or 10% of
cement and cured for about a week develops the properties required for an effective
cushion material. Stabilized RHA reduces the bandwith of vertical movements of
expansive soil not only during the first cycle of swelling but also during the subsequent
cycles of swelling and shrinkage. The reduction increases with the thickness of the
cushion. They have also found that lime stabilized RHA is more effective than cement
stabilized RHA.
Ali et al (2004) carried out an investigation to study the influence of RHA and lime on
Atterberg limits, strength, compaction swell and consolidation properties of bentonite. The
results indicated that the plasticity properties of bentonite were significantly modified upon
the addition of RHA and lime. The RHA and lime have noticeable influence on
compaction, swell and consolidation properties of bentonite soil particularly at 15% RHA
and 8% lime contents individually and combinedly at 15% RHA +4% Lime.
Raju et al(1999) carried out a study on strength characteristics of expansive soils
stabilized with lime and RHA. They conducted UCS tests and soaked CBR tests for
different combinations of the stabilizing agents and concluded that 4% lime is very close to
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the optimum either as the sole additive or with any other secondary additive from the view
point of optimum efficiency.
Rahman(1997) conducted a study on the effects of varies cement RHA proportions on
the geotechnical properties of lateritic soils. The influence of different mix proportions of
cement and RHA on Atterberg Limits , compaction characteristics, unconfined
compressive strength, California bearing ratio and swelling of lateritic soils were studied.
Test results show that lateritic stabilized with cement RHA mixing can be used
successfully in highway construction. From the point of view of compressive strength,
CBR and economy his study recommends a mix proportion of 6% RHA+3% cement for
sub base materials and 6% RHA+6% cement for base materials for optimum results.
2.2 Literature Review of Use on Raw Rice Husk (RRH)
Roy (2010) examined the effect of mixing of Rice Husk (RH) with soil to be used as road
subgrade construction materials. He mixed RH with various proportions of 5%, 10% and
15% with and studied the effect of addition of RH on compaction characteristics and CBR.
His test results showed that the OMC changes slightly with addition of RH and the value
remains within the range of 23 to 26%. However MDD showed a general decreasing value
of 1.64 to 1.41 with increasing percentage of RH. He evaluated CBR for both freshly
mixed soil sample and 30 days cured samples for soaked and unsoaked conditions and
found that CBR of soil decreases when RH is mixed in increasing percentage from 0 to
15% in both unsoaked and soaked conditions. Test results showed that with addition of
RH at increasing percentage with the original soil unsoaked CBR decreases from 4.9 to
3% only, To check the effect of curing on CBR, similar samples were prepared and cured
for 30 days in desiccators. Test results of cured samples indicated the similar trends as
that of uncured samples. However curing for 30 days shown improvement of soaked CBR
compared to that of uncured samples for any proportion of RH.
Chan et al(2008) studied the effect of Rice Husk on unconfined compressive strength of
soft clay soil stabilized with small amount cement. Instead of using conventional materials
like aggregates as the main constituents, the soft soil itself was being modified and used
as substitute at various layers, simultaneously reducing cost and utilizing the subsoil
which would have been otherwise removed. A laboratory based approach was adopted in
his study, where the modified soil specimen were subjected to UCS test upon 14 days of
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curing. The specimen were prepared using small amount of cement only or cement
admixed rice husk. The test data indicates that alternative road construction material can
be produced from modified soft soil, where the initially weak and soft material was
significantly improved and strengthened. The test results show that for cement modified
specimens, 5% cement was able to increase the strength of clay by 25%, whereas 10%
cement addition increases the strength by almost 100%. For cement rice husk
specimens,5% cement addition displayed negligible improvement with UCS value,
bordering bat about 20KPa. This suggest that main binding effect resulted in strength
increase was dominated by cement content. On the other hand, UCS value of the cement
rice husk specimens with 10% of cement were markedly improved to as high as 150KPa.
They thus have concluded that for a given cement content there seemed to have an
optimum percentage of rice husk required to achieve high strength.
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CHAPTER THREE
MATERIALS USED
3.1 Soil
Soil used in the present investigation has been collected from a pond of near Jadavpur
University. On visual inspection it was found to be light grey clayey silt. Evaluated
properties of the soil are shown in table-3.1 below. Based on L.L. and P.I. the soil may be
classified as CI.
Table-3 .1- Evaluated properties of original soil
Sl. No Characteristics Value
1 Specific Gravity 2.63
2 Particle Size Distribution(%)
a)Sand
b)Silt
c)Clay
9
81
10
3 Liquid Limit(%) 48
4 Plastic limit (%) 26
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5 Plasticity Index(%) 22
6 Classification of soil CI
7 Maximum Dry Density
(gm/cc)
1.61
8 Optimum Moisture
Content(%)
20
9 Unconfined Compressive
strength(KN/m2)
390
10 Unsoaked CBR(%) 8.3
11 Soaked CBR(%) 3.36
12 Swelling Index(%) 14
3.2 Lime
Until the invention of Portland cement, lime was used as the chief cementing material in
the construction field. Usually lime in free state is not found in nature. The raw material for
the manufacture of lime (CaO) is calcium carbonate which is obtained by the calcinations
of lime stone.
Quick Lime-It is the lime obtained after the calcinations of lime stone.
Hydrated Lime- When the quick lime is sprinkled with water it slakes within 10 minutes
and becomes powder and the fine powder obtained in the process is called hydrated lime.
The process is known as hydration of lime.
CaO + H2O --------- Ca(OH)2 + 15.6 kcal
On addition of lime to soil two main types of chemical reactions occur:-
Alteration in the nature of absorbed layers through base exchange phenomenon
Cementing or pozzolanic action.
Lime reduces the plasticity index of highly plastic soils making them more friable and easy
to be handled and pulverized. It also reduces the shrink swell properties of expansive soil.
The plasticity index of soils of low plasticity generally increases. There is generally an
increase in Optimum Moisture Content and decrease in Maximum Dry Density but the
strength and durability increases. Hydrated (slaked) lime is very useful /effective in
-
23
treating heavy, plastic clayey soils. Lime may be used alone or in combination with
cement, bitumen, fly ash, or other pozzolanic materials like rice husk ash etc. Sandy soils
may also be stabilized with these combinations. Lime has been mainly used for stabilizing
the road bases and sub grades. Lime is an unparrelled aid in the modification and
stabilization of soil beneath road and similar construction projects. Using lime can
substantially increase the stability, impermeability and load bearing capacity of the
subgrade. And lime is a proven solution for soil modification and stabilization in USA
where more than one million metric tons of lime is used annually for this purposes.
gains. The key to pozolanic reactivity and stabilization is a reactive soil, a good mix design
protocol, and a reliable construction practices.
Characteristics of Lime
Lime possesses good plasticity and is easy to work with
It stiffens easily and is resistant to moisture
It has excellent cementitious property
The shrinkage on drying is small because of its high water retentivity.
Constituents Wt%
SiO2 4.11
Al2 O3 3.11
Fe2 O3 2.70
Ca CO3 3.80
CaO 63.70
CaSO4 19.26
MgO 1.62
Loss on ignition 1.70
Table-3.2, Chemical composition of Hydrated Lime
(Source- Dr. H. Katebi, Lime stabilization of Calcareous Soil)
-
24
3.3 RICE HUSK
Rice husk is a major agricultural by product obtained from food crop paddy. It is a most
commonly available lignocellulosic materials that can be converted into different kinds of
fuels and chemical feedstocks through a variety of thermochemical conversion processes.
Generally it was considered earlier a worthless by product of the rice mills. For every four
tons of rice one ton of husk is produced. The husk is disposed of either by dumping in an
open heap near the mill site or on the road site to be burnt. Its bulk density ranges from 86
to 114 Kg/m3. It has high ash content, generally 15 to 24% and the ash has high silica
content. The silica content of the available ash ranges from 90 to 97%. Rice husk has a
chemical composition as follows:-
Sl. No Constituents % by weight
1. Cellulose 40 - 45
2. Lignin 25 - 30
3. Ash 15 - 24
4. Moisture 8 - 15
Table-3.3- Chemical composition of Rice Husk
(Source-Utilization of uncontrolled Burnt Rice Husk Ash in Soil Improvement,
Agus Setyo Muntohar. Sept. 2002)
Raw rice husk was collected from a nearby mini rice mill and it was used as they were
without further processing. This was to ensure minimal preparation procedure for cost and
labour saving in actual application.
Using natural materials like rice husk for ground improvement is not a novel idea but
practiced by early civilization too. Straws, for instance, were mixed and compacted with
mud to make walls and pathways in olden days. The artificial fibres were included to
enhance the strength and durability of the earth as construction materials.
-
25
3.4. RICE HUSK ASH
Rice Husk Ash is predominantly a siliceous material annually generated about 4.73
million tons after burning raw rice husk in a boiler or in open fire. The normal method of
conversion from rice husk to rice husk ash is by incineration. Burning rice husk generates
about 15-20% of its weight as ash. Many industries use rice husk as a relatively cheap
fuel. Concomitantly abundance of the ash (RHA) can be a potential waste product.
Indonesia produces paddy annually around 50 million tons. The amount of rice husk ash is
about 12.5 million tons and the ash (RHA) production is about 4 million tons. The ash
being very light easily is carried by wind and water by in its dry state. It is difficult to
coagulate and thus contribute to air and water pollution. Cumulative generation of ash
requires a large space for disposal. Utilization of rice husk ash by exploiting its inherent
properties is the only way to solve the environmental and disposal problem of rice husk
ash.
Chemically RHA consists of 82-87 % of silica, exceeding that of fly ash. Materials
containing high reactive silica (SiO2) is suitable to be used as lime-pozolana mixes and as
substitution of port land cement. The high percentage of siliceous materials in the RHA
makes it an excellent material for soil stabilization. The silica content in the rice husk ash
(RHA) is dependent on the following:- a) the variety of the rice, b) soil and climate
conditions, c) prevailing temperature and d) agricultural practices ranging from application
of fertilizers and insecticides etc.
A number of researchers has studied the physical and chemical properties of rice husk
ash (RHA). Rice husk ash can not be used alone for stabilizing soil because of the lack of
the cementitious properties. The high percentage of siliceous material in RHA indicates
that it has potential pozzolanic properties. The normal method of conversion of husk to
ash is incineration. The properties of RHA depend whether the husks have undergone
complete destructive combustion or have been partially burnt. The RHA has been
classified into high carbon char, low carbon ash and carbon free ash. The composition
and properties of rice husk ash is presented in table nos 3.4 and 3.5 below.
-
26
Sl. No Components % present in RHA
1. SiO2 93.2
2. Al2O3 0.59
3. Fe2O3 0.22
4. CaO 0.51
5. MgO 0.41
6. K2O 2.93
7. Loss in Ignition 1.19
Table-3.4 Composition of Rice Husk Ash(RHA) Used
Sl. No Property Value
1. Specific Gravity 1.95
2. Max. Dry Density 8.5
3. Optimum Moisture
Content
31.8
4. Angle of Internal Friction 38
5. Unsoaked CBR(%) 8.75
6. Soaked CBR(%) 8.15
Table 3.5- Properties of Rice Husk Ash (RHA)
Rice husk ash for the present investigation was obtained from a local rice mill at
Chandpara, North 24 Parganas the properties of which have been listed above.
-
27
CHAPTER FOUR
OBJECTIVES AND SCOPE OF THE WORK
4.1 OBJECTIVES
The objectives of the present study are as follows:-
To determine the applicability, effectiveness and suitability of lime and some locally
available agricultural waste materials e.g. Raw Rice Husk(RRH) and Rice Husk
Ash(RHA) in isolation and in different combinations as soil stabilizing materials for
use in road subgrade.
To characterize both the unstabilized and stabilized soil by conducting routine
laboratory tests like specific gravity, Atterberg Limits, grain size analysis etc.
To determine engineering properties e.g. optimum moisture content (OMC),
maximum dry density (MDD), California Bearing Ratio (CBR), both unsoaked and
soaked for both unstabilized and stabilized soil for assessing the improvement of
soil with stabilization in terms soil strength.
To find out the best possible design mix proportion of soil and admixtures which
gives maximum strength of stabilized soil compared to that of the original soil.
4.2. SCOPES:-
The scopes of work for the present study is summarized below :-
Procurement of soft soil, Rice Husk, Rice Husk Ash and lime.
Conducting routine laboratory tests of original soil, e.g. Liquid Limits, Plastic Limit,
grain size analysis, specific gravity, bulk density field moisture content, swelling
index etc. for characterizing the soil.
Preparation of soil admixtures mixes by percentage of dry weight with appropriate
preselected proportion as shown in tables 4.1 and 4.2 below.
-
28
Table4.1- Details of Mix Proportions of Lime and RHA with Soil
Mix No Soil (%) Lime (%) RHA (%)
1.
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
29
30
31
100
97
94
91
88
85
95
90
85
80
92
87
82
77
89
84
79
74
86
81
76
71
83
78
73
68
80
75
70
65
0
3
6
9
12
15
0
0
0
0
3
3
3
3
6
6
6
6
9
9
9
9
12
12
12
12
15
15
15
15
0
0
0
0
0
0
5
10
15
20
5
10
15
20
5
10
15
20
5
10
15
20
5
10
15
20
5
10
15
20
-
29
Table -4.2 Details of Mix Proportions of Lime and RRH with Soil
Mix No Soil (%) Lime (%) RRH (%)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
100
98
97
96
95
94
92
91
90
89
88
89
88
87
86
85
86
85
84
83
82
0
0
0
0
0
0
6
6
6
6
6
9
9
9
9
9
12
12
12
12
12
0
2
3
4
5
6
2
3
4
5
6
2
3
4
5
6
2
3
4
5
6
Conducting routine laboratory tests with different mix proportions as tabulated above.
Conducting Standard Proctor Test as per IS: 2700(Part-VII),1980/87 on both
unstabilized and stabilized soil mixes to determine their individual OMC and MDD.
Conducting Laboratory CBR tests on both unstabilized and stabilized soil mixes as
tabulated above to find out the CBR value for each of them corresponding to
2.5mm and 5.0mm penetration after compacting the soil at moisture content 5%
more than their respective OMC.
Conducting Unconfined Compressive Strength (UCS) Tests on samples obtained
by compacting each of the unstabilized and stabilized soil samples at OMC+ 5%
moisture content in Standard Proctor Mould.
-
30
Conducting soaked as well as unsoaked CBR tests on few stabilized soil samples
after curing for 7 days.
Conducting UCS tests for all stabilized soil samples after 7 days and 28 days
curing.
Comparison of test results and evaluation of improvement of weak soil in terms of
CBR and UCS value.
-
31
CHAPTER FIVE
TEST PROGRAM
5.0 General:
Detailed experimental study was under taken to investigate the characteristics and
behavior of typical locally available soil mixed with lime and waste materials like Raw
Rice Husk(RRH) and Rice Husk Ash (RHA) in different percentage and in several
combinations from the view point of applicability of such materials in road subgrade.
In view of the above the present experimental study has been aimed at to investigate the
behavior of soils with additions of alternative materials as detailed below:
Typical locally available soil
Typical locally available soil and lime
Typical locally available soil and RHA
Typical locally available soil, lime and RHA
Typical locally available soil and RRH
Typical locally available soil, RRH and lime
5.1 Test Program
5.1.1 Routine tests for characterization such as Liquid Limit, Plastic Limit, Specific gravity,
Free swell index test etc., compaction characteristics and strength properties of
unstabilized soil.
5.1.2 Relevant tests for characterization, compaction characteristics and strength
properties (CBR and UCS) of stabilized soil.
-
32
Detailed test program of the present study has been reported in this section in tables 5.1
and 5.2 below.
Table-5.1, Detail test program for Lime RHA mixed soil
Sl.
No
Tes
t
No
Mis
Proportions
L.
L
P.
L
UCS CBR CBR(after 7
days curing)
Soil
(%)
Li
me
(%)
RH
A(%
)
0d
ay
cu
rin
g
7
day
s
curi
ng
28
days
curin
g
unso
aked
soa
ked
Unso
aked
soake
d
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
100
97
94
91
88
85
95
90
85
80
92
87
82
77
89
84
79
74
86
81
76
71
83
78
0
3
6
9
12
15
0
0
0
0
3
3
3
3
6
6
6
6
9
9
9
9
12
12
0
0
0
0
0
0
5
10
15
20
5
10
15
20
5
10
15
20
5
10
15
20
5
10
-
33
25
26
27
28
29
30
25
26
27
28
29
30
73
68
80
75
70
65
12
12
15
15
15
15
15
20
5
10
15
20
Table-5.2- Detail test program for Lime RRH mixed soil
Sl.
No
Te
st
No
Mis Proportions L.
L
P.
L
UCS CBR CBR(after 7
days curing)
Soil(
%)
Li
me
(%)
RR
H(%
)
0d
ay
cu
rin
g
7
day
s
curi
ng
28
days
curin
g
unso
aked
soa
ked
Unso
aked
soake
d
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
100
98
97
96
95
94
92
91
90
89
88
89
88
87
86
85
0
0
0
0
0
0
6
6
6
6
6
9
9
9
9
9
0
2
3
4
5
6
2
3
4
5
6
2
3
4
5
6
-
34
17
18
19
20
21
17
18
19
20
21
86
85
84
83
82
12
12
12
12
12
2
3
4
5
6
-
35
CHAPTER SIX
TEST PROCEDURES
6.0- General:-
In this chapter detailed test proc17edures have been presented. All the tests for
unstabilized soil as well as stabilized soil were carr18ied out as per the procedures laid
out in the relevant IS code of practice.1920
6.1 Name of the tests and the relevant IS code followed, have been presented in this
section in tabular form as below.
Table-6.1- Name of tests performed and Relevant IS Code followed.
25Sl. No Name of tests Relevant IS code
followed
126 Specific Gravity IS : 2720, Part-3, 1980
227 Atterberg Limits IS ; 2720, Part -5,1985
3 Classification and Identification of
soil
IS : 2720, Part-1498,1970
4 Grain size analysis IS : 2720, Part-4,1985
5 Water content determination IS : 2720, Part -2, 1973
6 Free swell Index of soil IS : 2720, Part-40,1977
7 Unconfined Compressive Strength IS : 2720, Part-10,1973
8 Laboratory CBR IS :2720, Part-16,1979
9 Water content Dry density
Relationship using light compaction
IS :2720, Part-7, 1980
10 Unconfined compressive strength
test for stabilized soil
IS :4332, Part-V, 1970
-
36
All the tests of original soil were carried out as per the standard practice as laid out in the
relevant IS code of practice. For tests of specimens of mixed/stabilized soils , specimens
were prepared by thoroughly mixing the required quantity of soil and stabilizers in
preselected proportion in dry state and then required quantity of water was sprinkled and
mixed thoroughly to get a homogeneous and uniform mixture of soil and admixtures. To
maintain the homogeneity and uniformity in mix proportions, specimens for both the
Unconfined compressive strength tests and California Bearing Ratio tests were prepared
simultaneously, so as to ensure uniformity in materials and water content. Specimens for
UCS tests were collected from Standard Proctor mould after compacting the same in the
mould at a moisture content equal to respective OMC plus 5%. For every combinations, 9
samples were prepared. Three were tested on the same day of preparation of specimens
and another six specimens were kept in dessicator after putting the specimens in sealed
plastic bag for 7 days and 28 days testing to investigate the effect of curing.
For laboratory CBR tests, specimens were prepared in the CBR mould as per the
standard practice. Immediately after preparation of specimen the same tested for
unsoaked condition and then it was submerged for four days for soaked tests. Same
specimens were used for both unsoaked and soaked tests. For every combination of soil
and stabilizers, two specimens were kept in closed dessicator after covering the same by
plastic sheet for 7 days. Thereafter the specimens were tested for unsoaked and four days
soaked tests to investigate the effect of curing.
For Atterberg limit tests on mixed soils, specimens were prepared by mixing soil and
stabilizers in dry state as per the preselected proportions thoroughly and then water was
added as per the standard practice. To investigate the effect of mixing RHA, RHA lime
combination and also RRH and RRH Lime combination with the original soil to be used for
construction of road subgrade, RHA was mixed in various proportions of 5%,10%, 15%,
20% and RRH was mixed in proportions of 2%,3%,4%,5%,and 6% with soil in isolation
and in combination of lime in the proportions of 3%,6%,9%,12%,15%,with each of the
percentage of RHA and 6%,9%,12%,respectively with each of the percentage of RRH. To
determine the moisture content dry density relation ship, CBR and UCS of stabilized soil ,
Standard Proctor Test (IS 2720, Part-7, 1980) was carried out. Specimens for CBR tests
was compacted at moisture content equal to OMC plus five percent and for UCS tests
specimens were collected from Standard Proctor Mould after compacting it at moisture
content equal toOMC+5%.
-
37
CHAPTER SEVEN
PRESENTATION OF TEST RESULTS
7.0 - General:-
In this chapter the results of all the tests carried out have been presented in the following
sections.
7.1- Evaluated geotechnical properties of soil
In this section the evaluated geotechnical properties of the original soil have been
presented in tabular form in table 6.1 below and the necessary graphs have been
presented thereafter.
Table-7.1- Evaluated geotechnical properties of Original Soil
Sl. No Characteristics Value
1 Specific Gravity 2.63
2 Particle Size Distribution(%)
a)Sand
b)Silt
c)Clay
9
81
10
3 Liquid Limit(%) 48
4 Plastic limit(%) 26
5 Plasticity Index(%) 22
6 Classification of soil CI
7 Maximum Dry Density (gm/cc) 1.61
8 Optimum Moisture Content(%) 20
-
38
9 Unconfined Compressive strength(KN/m2) 390
10 Unsoaked CBR(%) compacted at OMC 8.3
11 Soaked CBR(%) compacted at OMC 3.36
12 Unsoaked CBR(%) compacted at moisture
content OMC+5%.
4.3
13 Soaked CBR (%) when compacted at
moisture content OMC+ 5%
2.6
14 Swelling Index(%) 14
Original Soil
0
0.5
1
1.5
2
0 10 20 30 40
water content(%)
Dry
density(g
m/c
c)
Fig 7.1(a)-Dry density moisture content relationship of original
Grain Size Distribution of Soil
0
20
40
60
80
100
120
0.001 0.01 0.1 1 10
Grain Size ( mm)
Fig 7.1(b)- Grain size distribution curve of original soil
-
39
Unsoaked CBR Test of Soil at 35% water Content
0
20
40
60
80
100
120
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14
Penetration (mm)
Lo
ad
(K
g)
Fig 7.1(c) Unsoaked CBR of original soil
Fig 7.1(d) Soaked CBR of original soil
6.2. Results for Characterization test of stabilized soil
Results of laboratory tests for Liquid Limit, Plastic Limit, Plasticity Index properties of
different mixes of soil with varying percentage of Lime, RHA, Lime and RHA , Raw Rice
Husk(RRH) and RRH plus Lime for characterization of Unstabilized and Stabilized Soil
have been presented in this section.
Soaked CBR Test of Soil at 30% Water Content
0
20
40
60
80
100
120
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14
Penetration (mm)
Load (Kg)
-
40
6.2.1. Consistency limits of soil with varying percentage of Lime are presented in this
section along with necessary graphical representation.
Table -7.2, Consistency limits of soil with varying percentage of Lime
% of Lime Liquid Limit(%) Plastic Limit(%) Plasticity
Index(%)
0 48 26 22
3 55.5 35.2 20.3
6 56.3 35.9 20.4
9 58.5 38.3 20.2
12 59.7 39.2 19.8
15 60.3 41.5 18.8
Variation of Plastic Limit with varying
percentage of lime
0
10
20
30
40
50
0 5 10 15 20
% of Lime
Pla
sti
c lim
it(%
)
Plastic Limit(%)
Fig -7.1(e)
-
41
Variation of Liquid Limt with varying
percentage of Lime
0
10
20
30
40
50
60
70
0 5 10 15 20
% of Lime
Liq
uid
Lim
it(%
)
Liquid Limt
Fig 7.1(f)
Variation of Plasticity Index(%) with varying % of
Lime
18
19
20
21
22
23
0 5 10 15 20
% of Lime
Pla
sti
cit
y In
dex(%
)
Plasticity Index(%)
Fig 7.1 (g)
7.2.2 Consistency Limits of soil with varying percentage of Rice Husk Ash have been
presented in this section along with graphical representations.
-
42
Table-7.3, Consistency Limits of soil with varying percentage of RHA
% of RHA Liquid Limit(%) Plastic Limit(%) Plasticity Index(%)
0 48 26 22 5 56.6 37.2 19.4 10 58.3 39.4 18.9 15 61.7 43.95 17.75 20 63.5 45.69 17.81
Variation of Liquid Limit with varying % of RHA
0
10
20
30
40
50
60
70
0 5 10 15 20 25
% of RHA
Liq
uid
Lim
it(%
)
Liquid Limit
Fig 7.1(h)
Varyiation of Plastic Limit(%) with varying % of
Lime
0
10
20
30
40
50
0 5 10 15 20 25
% of Lime
Pla
sti
c L
imit
(%)
Plastic Limit(%)
-
43
Fig7.1 (i)
Variation of Plasticity Index with varying % of
RHA
0
5
10
15
20
25
0 5 10 15 20 25
% of RHA
Pla
sti
cit
y In
dex(%
0Plasticity Index
Fig 7.1(j)
7.2.3 Consistency Limits of soil with lime and RHA addition have been presented in this
section along with graphical representations
Table-7.4, Consistency Limits of soil with varying percentage of Lime and RHA
Soil(%) Lime(%) RHA(%) L.L(%) P.L.(%) P.I(%) 100 0 0 48 26 22 92 3 5 56.5 38.2 18.3
87 3 10 57.3 39.3 18 82 3 15 58.5 41.1 17.4 77 3 20 60.4 42.4 18 89 6 5 57.5 38.6 18.9 84 6 10 59.3 39.2 20.1 79 6 15 61.5 41.3 20.2
74 6 20 62.5 43.2 19.3 86 9 5 59.6 41.1 18.5 81 9 10 60.4 42.5 17.9 76 9 15 61.3 43.2 18.1
-
44
71 9 20 63.2 43.6 19.6 83 12 5 59.3 41.5 17.8 78 12 10 61.5 42.9 18.6
73 12 15 63.5 43.2 20.3 68 12 20 64.3 44.5 19.8 80 15 5 60.4 42 18.4 75 15 10 62.6 42.8 19.8 70 15 15 64.5 43.7 20.8 65 15 20 66.2 45.2 21
Variation of Liquid Limit with varying % of RHA
for a given % of Lime
0
10
20
30
40
50
60
70
0 10 20 30
% of RHA
Liq
uid
Lim
it(%
)
L.L. for 3% Lime
content
L.L for 6% Lime
L.L. for 9% Lime
content
L.L. for 12% Lime
content
L.L.for 15% Lime
content
Fig 7.2(a)
-
45
Variation of Plastic Limit with varying % of RHA
for a given % of Lime
0
10
20
30
40
50
0 10 20 30
% of RHA
Pla
sti
c L
imit
(%)
P.L. for 3% Lime
content
P.L.for 6% Lime
content
P.L.for 9% Lime
content
P.L for 12% Lime
content
P.L.for 15% Lime
content
Fig 7.2(b)
Variation of Plasticity Index of soil with varying
% of RHA for a given % of Lime
0
5
10
15
20
25
0 10 20 30
% of RHA
P.I.(
%)
P.I. for 3% Lime
content
P.I.for 6% Lime
content
P.I.for 9% Lime
content
P.I.for 12% Lime
content
P.I. for 15% Lime
content
Fig 7.2(c)
7.2.4- Consistency Limits of soil with varying percentage of Raw Rice Husk(RRH)
addition have been presented in this section along with necessary graphical
representation.
Table-7.5- Consistency Limits of Soil with varying percentage of Raw
Rice Husk
-
46
% RRH L.L(%) P.L.(%) P.I(%)
0 48 26 22
2 59.2 37 22.2
3 60.5 38.2 22.3
4 62.2 39.4 22.8
5 63 40.3 22.7
6 64.4 42.1 22.3
Variation of Liquid Limit with varying % of RRH
0
10
20
30
40
50
60
70
0 2 4 6 8
% OF RRH
Liq
uid
Lim
it(%
)
Liquid Limit
Fig 7.3(a)
-
47
Variation of Plastic Limitwith varying % of RRH
0
5
10
15
20
25
30
35
40
45
0 2 4 6 8
% OF RRH
Pla
sti
c lim
it(%
)Plastic Limit
Fig7.3 (b)
Variation of Plasticity Index with varying % of
RRH
21.8
22
22.2
22.4
22.6
22.8
23
0 2 4 6 8
% of RRH
Pla
sti
cit
y In
dex(%
)
Plasticity Index(%)
Fig 7.3(c)
7.2.5 Consistency Limits of soil with varying percentage of Lime and RRH addition have
been presented in this section along with necessary graphical representation.
Table-7.6, Consistency Limits of soil with varying percentage of Lime and RRH
-
48
Soil(%) Lime(%) RRH(%) L.L.(%) P.L.(%) P.I.(%)
100 0 0 48 26 22
6 2 56 39 17
6 3 57.2 39.4 17.8
6 4 58.1 41.2 16.9
6 5 59 42 17
6 6 59.3 39.5 19.8
9 2 58 41.9 16.1
9 3 58.8 41.8 17
9 4 59.2 42.4 16.8
9 5 60.7 43 17.7
9 6 62.2 42.9 19.3
12 2 62 43.3 18.7
12 3 62.9 44.3 18.6
12 4 63.4 45.1 18.3
12 5 64.2 46 18.2
12 6 65.6 46.6 19
Variation of Liquid Limit with varying % of RRH
for a given % of Lime
0
10
20
30
40
50
60
70
0 2 4 6 8
% of RRH
Liq
uid
Lim
it(%
) L.L.for 6% Lime
content
L.L.for 9% of Lime
content
L.L. for 12% Lime
content
Fig 7.4(a)
-
49
9
Variation of P.L. for varying % of RRH for a
given % of Lime
0
10
20
30
40
50
0 2 4 6 8
% of RRH
P.L
(%
)
P.L. for 6% of Lime
P.L. for 9% of Lime
P.L. for 12% of
Lime
Fig 7.4(b)
Variation of P.I. for varying % of RRH with a
given % of Lime
0
5
10
15
20
25
0 2 4 6 8
% of RRH
P.I.(
%)
P.I. FOR 6% of Lime
P.I. for 9% of Lime
P.i. FOR 12% OF
lIME
Fig 7.4 (C)
7.3 Compaction Characteristics of Unstabilized and Stabilized Soil
In this section results of Compaction Characteristics of unstabilized and Stabilized Soil
obtained from Standard Proctor tests have been presented in tables and graphs.
7.4.1 Compaction characteristics of Unstabilized soil
-
50
Fig 7.5(a)
7.4.2 Compaction characteristics of Soil with varying percentage of Lime have been
presented in this section along with necessary graphical representation in table 6.7.
Table -7.7 Compaction characteristics of soil with varying percentageof Lime
Sl. No % of Lime O.M.C(%) Max.Dry Density(gm/cc)
1 0 20 1.61
2 3 22 1.51
3 6 22.5 1.46
4 9 23 1.45
5 12 25 1.43
6 15 26.2 1.42
-
51
Fig 7.5(b)
Soil +6% Lime
1.2
1.25
1.3
1.35
1.4
1.45
1.5
0 5 10 15 20 25 30
Water Content (%)
Dry
Density(g
m/c
c)
Fig 7.5(c)
-
52
OMC+15% Lime
1.25
1.3
1.35
1.4
1.45
0 10 20 30 40
Water Content (%)
Dry
density(g
m/c
c)
Soil + 9% Lime
0
0.5
1
1.5
2
0 10 20 30 40
Water Content(%)
DR
Y
DE
NS
ITY
(gm
/cc)
Fig 7.5(d)
Soil +12% Lime
1.3
1.32
1.34
1.36
1.38
1.4
1.42
1.44
0 10 20 30 40
Water Content(%)
Dry
Density(g
m/c
c)
Fig 7.5(e)
Fig7.5(f)
-
53
7.4.3. Compaction characteristics of soil with varying percentage of RHA
Compaction Characteristics of Soil with varying percentage of RHA have been presented
in this section along with necessary graphical representation in table 7.8.
Table- 7.8, Compaction characteristics of Soil with varying percentage of RHA
Sl.No %of RHA OMC(%) Max.Dry Density(gm/cc)
1 0 20 1.61
2 5 23.5 1.43
3 10 25.4 1.39
4 15 28.3 1.35
5 20 30.8 1.29
Soil + 5% RHA
1.3
1.35
1.4
1.45
0 10 20 30 40
Water Content (%)
Dry
density(g
m/c
c)
Fig 7.6(a)
-
54
Soil +10% RHA
1.15
1.2
1.25
1.3
1.35
1.4
0 10 20 30 40
Water Content (%)
Dry
density
(gm
/cc)
Fig7.6 (b)
OMC +15% RHA
1.15
1.2
1.25
1.3
1.35
0 10 20 30 40 50
Wqater Content (%)
Dry
de
nsity(g
m/c
c)
Fig 7.6(c))
Soil +20% RHA
1.1
1.15
1.2
1.25
1.3
0 10 20 30 40 50
Water Content (%)
Dry
de
nsity(g
m/c
c)
-
55
Fig 7.6 (d)
7.4.4 Compaction Characteristics of soil with varying combination of Lime and RHA have
been presented in this section in table 7.9 along with necessary graphical representation.
Table -7.9, Compaction charactertistics of Soil with varying percentage of Lime and
RHA
Sl No Soil(%) Lime(%) RHA(%) OMC(%0 Mdd(gm/cc)
1 3 5 25 1.41
2 3 10 27.2 1.38
3 3 15 29.1 1.33
4 3 20 30.9 1.29
5 6 5 26 1.39
6 6 10 27.5 1.36
7 6 15 30.2 1.32
8 6 20 32.4 1.28
9 9 5 28 1.39
10 9 10 29.5 1.36
11 9 15 31.2 1.3
12 9 20 32.8 1.26
13 12 5 28.9 1.37
14 12 10 30.7 1.34
15 12 15 31.9 1.29
16 12 20 33.1 1.25
17 15 5 29.3 1.35
18 15 10 30.9 1.31
19 15 15 32.1 1.27
20 15 20 33.6 1.23
-
56
Soil+3% Lime +5% RHA
1.28
1.3
1.32
1.34
1.36
1.38
1.4
1.42
0 10 20 30 40
Water Content (%)
Dry
De
nsity(g
m/c
c)
Fig 7.7(a)
Soil+3 %Lime+ 10% RHA
1.2
1.25
1.3
1.35
1.4
0 10 20 30 40
Water Content (%)
Dry
density(g
m/c
c)
Fig 7.7 (b)
-
57
Soil+3% Lime +15% RHA
1.15
1.2
1.25
1.3
1.35
0 10 20 30 40
Water Content (%)
Dry
de
nsity(g
m/c
c)
Fig 7.7(c)
Soil+3% Lime+20% RHA
1.1
1.15
1.2
1.25
1.3
0 10 20 30 40
Water Content (%)
Dry
de
nsity(g
m/c
c)
Fig 7.7 (d)
Soil+6% Lime+5% RHA
1.26
1.281.3
1.32
1.34
1.361.38
1.4
0 10 20 30 40
Water Content(%)
Dry
de
nsity(g
m/c
c)
Fig 7.7(e)
-
58
Soil +6% Lime+10% RHA
1.2
1.25
1.3
1.35
1.4
0 10 20 30 40
Water Content (%)
Dry
de
nsity(g
m/c
c)
Fig 7.7(f)
Soil+6% Lime+15% RHA
1.21.221.241.261.28
1.31.321.34
0 10 20 30 40
Water Content (%)
Dry
de
nsity(g
m/c
c)
Fig7.7(g)
Soil+6% Lime+20% RHA
1.1
1.15
1.2
1.25
1.3
0 10 20 30 40
Water Content (%)
Dry
de
nsity(g
m/c
c)
Fig 7.7 (h)
-
59
Soil+9% Lime+5% RHA
1.25
1.3
1.35
1.4
0 10 20 30 40
Water Content (%)
Dry
de
nsity(g
m/c
c)
Fig 7.7(i)
Soil+9% Lime+10% RHA
1.2
1.25
1.3
1.35
1.4
0 10 20 30 40
Water Comtent (%)
Dry
de
nsity(g
m/c
c)
Fig 7.7(j)
Soil+9% Lime+15% RHA
1.15
1.2
1.25
1.3
0 10 20 30 40 50
Water Content (%)
Dry
den
sit
y(g
m/c
c)
Fig 7.7(k)
-
60
Soil+9% Lime+20% RHA
1.121.141.161.181.2
1.221.241.261.28
0 10 20 30 40 50
Water Content (%)
Dry
den
sit
y(g
m/c
c)
Fig 7.7(l)
Soil+12% Lime+5% RHA
1.2
1.25
1.3
1.35
1.4
0 10 20 30 40
Water Content(%)
Dry
den
sit
y(g
m/.cc)
Fig 7.7(m)
Soil+12% Lime+10% RHA
1.2
1.22
1.24
1.26
1.28
1.3
1.32
1.34
0 10 20 30 40
Water Content (%)
Dry
dfe
nsit
y(g
m/c
c)
Fig 7.7(n)
-
61
Soil+12% Lime+15% RHA
1.16
1.18
1.2
1.22
1.24
1.26
1.28
1.3
0 10 20 30 40
Water Content (%)
Dry
den
sit
y(g
m/c
c)
Fig 7.7(o)
Soil+12% Lime+20% RHA
1.14
1.16
1.18
1.2
1.22
1.24
1.26
0 10 20 30 40 50
Water Content (%)
Dry
den
sit
y(g
m/c
c)
Fig 7.7(p)
Soil+15% Lime+5% RHA
1.221.241.261.281.3
1.321.341.361.38
0 10 20 30 40
Water Content (%)
Dry
den
sit
y(g
m/c
c)
Fig7.7(q)
-
62
Soil+15% Lime+10% RHA
1.15
1.2
1.25
1.3
1.35
0 10 20 30 40
Water Content (%)
Dry
den
sit
y(g
m/c
c)
Fig 7.7(r)
Soil+15% Lime+15% RHA
1.16
1.18
1.2
1.22
1.24
1.26
1.28
0 10 20 30 40
Water Content (%)
DR
Y D
EN
SIT
Y(g
m/c
c)
Fig 7.7(s)
Soil+15% Lime+20% RHA
1.11.121.141.161.181.2
1.221.24
0 10 20 30 40
Water Content (%)
Dry
den
sit
y(g
m/c
c)
Fig7.7 (t)
-
63
7.4.5 Compaction Characteristics of soil with varying percentage of RRH have been
presented in this section in table 6.10 along with necessary graphical representation.
Table- 7.10- Compaction characteristics of soil with varying percentage of Raw Rice
Husk
Sl. No % of RRH OMC(%) MDD(gm/cc)
1 0 20 1.61
2 2 23.2 1.47
3 3 24.3 1.43
4 4 25.3 1.38
5 5 26.5 1.34
6 6 28 1.31
Soil+2% RRH
1.36
1.38
1.4
1.42
1.44
1.46
1.48
0 10 20 30 40
Water Content (%)
Dry
den
sit
y(g
m/c
c)
Fig 7.8(a)
-
64
Soil+3% RRH
1.34
1.36
1.38
1.4
1.42
1.44
0 10 20 30 40
Water Content (%)
Dry
density(g
m/c
c)
Fig 7.8 (b)
Soil+4% RRH
1.28
1.3
1.32
1.34
1.36
1.38
0 10 20 30 40
Water Content (%)
Dry
de
nsity(g
m/c
c)
Fig 7.8 (c)
Soil+5% RRH
1.221.241.261.281.3
1.321.341.36
0 10 20 30 40
Water Content (%)
Dry
density(g
m/c
c)
-
65
Fig 7.8(d)
Soil+6% RRH
1.18
1.2
1.22
1.24
1.26
1.28
1.3
1.32
0 10 20 30 40
Water Content (%)
Dry
density9gm
/cc)
Fig 7.8 (e)
7.4.6 Compaction Characteristics of soil with varying percentage of Lime and RRH have
been presented in this section in table 6.11 along with necessary graphical representation.
Table-7.11- Compaction characteristics of soil with varying percentage of Lime and
RRH
Sl. No Soil(%) Lime(%) RRH(%) OMC(%) MDD(gm/cc)
1 100 0 0 20 1.61
2 6 2 24 1.43
3 6 3 25 1.4
4 6 4 26.1 1.37
5 6 5 27.5 1.35
6 6 6 28.9 1.32
7 9 2 25.1 1.4
8 9 3 26.3 1.36
9 9 4 27.5 1.33
10 9 5 28.7 1.31
11 9 6 30.3 1.29
12 12 2 26.5 1.36
-
66
13 12 3 28.7 1.33
14 12 4 29.6 1.3
15 12 5 30.8 1.28
16 12 6 32.2 1.25
Soil+6% Lime+2% RRH
1.25
1.3
1.35
1.4
1.45
0 10 20 30 40
Water Content (%)
Dry
de
nsity(g
m/c
c)
Fig 7.9(a)
Soil+6% Lime+3% RRH
1.3
1.32
1.34
1.36
1.38
1.4
0 10 20 30 40
Water Content (%)
Dry
density(g
m/c
c)
Fig 7.9(b)
-
67
Soil+6% Lime+4% RRH
1.26
1.28
1.3
1.32
1.34
1.36
1.38
0 10 20 30 40
Water Content (%)
Dry
density(g
m/c
c)
Fig 7.9(c)
Soil+6% Lime+5% RRH
1.2
1.25
1.3
1.35
0 10 20 30 40
Water Content (%)
Dry
de
nsity(g
m/c
c)
Fig 7.9(d)
Soil+6% Lime+6% RRH
1.15
1.2
1.25
1.3
1.35
0 10 20 30 40
Water Content (%)
Dry
density(g
m/c
c)
Fig 7.9 (e)
-
68
Soil+9% Lime+2% RRH
1.3
1.32
1.34
1.36
1.38
1.4
0 10 20 30 40
Water Content (%)
Dry
density(g
m/c
c)
Fig 7.10(a)
Soil+9% Lime+3% RRH
1.2
1.25
1.3
1.35
1.4
0 10 20 30 40
Water Content (%)
Dry
de
nsity(g
m/c
c)
Fig 7.10 (b)
Soil+9% Lime+4% RRH
1.221.241.261.28
1.31.321.34
0 10 20 30 40
Water Content (%)
Dry
de
nsity(g
m/c
c)
-
69
Fig 7.10(c)
Soil +9% Lime+5% RRH
1.1
1.151.2
1.251.3
1.35
0 10 20 30 40
Water Content (%)
Dry
de
nsity(g
m/c
c)
Fig 7.10(d)
Soil+9% Lime+6% RRH
1.1
1.15
1.2
1.25
1.3
0 10 20 30 40
Water Content (%)
Dry
de
nsity(g
m/c
c)
Fig7.10 (e)
Soil+12% Lime+2% RRH
1.15
1.2
1.25
1.3
1.35
1.4
0 10 20 30 40
Water Content (%)
Dry
density(g
m/c
c)
Fig 7.11(a)
-
70
Soil+12% Lime+3% RRH
1.15
1.2
1.25
1.3
1.35
0 10 20 30 40
Water5 Content (%)
Dry
density(g
m/c
c)
Fig 7.11(b)
Soil+12% Lime+4% RRH
1.1
1.15
1.2
1.25
1.3
1.35
0 10 20 30 40
Water Content (%)
Dry
density(g
m/c
c)
Fig 7.11(c)
Soil+12% Lime+5% RRH
1.1
1.15
1.2
1.25
1.3
0 10 20 30 40
Water Content (%)
Dry
density(g
m/c
c)
Fig 7.11(d)
-
71
Soil+12% Lime+6% RRH
1
1.05
1.1
1.15
1.2
1.25
1.3
0 10 20 30 40
Water Content (%)
Dry
density(g
m/c
c)
Fig 7.11(e)
Variation of O.M.C. with Lime content
0
5
10
15
20
25
30
0 5 10 15 20
% of Lime
O.M
.C(%
)
O.M.C(%)
Fig 7.12(a)
-
72
Variation of M.D.D.(gm/cc) with Lime
content
1.4
1.45
1.5
1.55
1.6
1.65
0 10 20
% of Lime
M.D
.D.(
gm
/cc)
M.D.D.(gm/cc)
Fig 7.12(b)
Variation of O.M.C with RHA content
0
5
10
15
20
25
30
35
0 10 20 30
% of RHA
O.M
.C.(
%)
O.M.C
Fig 7.12(c)
-
73
Variation of M.D.D.(gm/cc) with RHA content
0
0.5
1
1.5
2
0 5 10 15 20 25
% of RHA
M.D
.D.(
gm
/cc)
M.D.D.(gm/cc)
Fig 7.12(d)
Variation of OMC for Lime RHA mixed soil with
Lime
0
5
10
15
20
25
30
35
40
0 5 10 15 20
% of Lime
OM
C(%
) OMC for RHA 5%
OMC for RHA10%
OMC for RHA15%
OMC for RHA20%
Fig7 .12(e)
-
74
Variation of MDD for Lime RHA mixed soil with
Lime
1.2
1.25
1.3
1.35
1.4
1.45
0 5 10 15 20
%of Lime
MD
D(g
m/c
c)
MDD for RHA 5%
MDD for RHA 10 %
MDD for RHA 20%
"MDD for RHA 15%"
Fig 7.12(f)
Variation of OMC(%) WITH RRH content
0
5
10
15
20
25
30
0 2 4 6 8
% of RRH
OM
C(%
)
OMC(%)
Fig 7.12(g)
-
75
Variation of MDD(gm/cc) with RRH content
0
0.5
1
1.5
2
0 2 4 6 8
% of RRH
MD
D(K
N/m
3)
MDD(KN/m3)
Fig 7.12(h)
7.5 Strength characteristics of soil
The strength characteristics (CBR and UCS) of both stabilized and unstabilized soil have
been presented in this section.
7.4.6.1 Strength characteristics of mixed soil with varying percentage of Lime have been
presented in this section with graphical representations.
Table -7.11 Strength Characteristics of soil with varying percent of lime
Sl No % of
Lime
CBR(%),
(compacted at
OMC+5% moisture
content)
CBR(%) after 7
days
curing(compacted
at OMC + 5%
moisture content)
UCS(KN/m2 ),
(Specimens compacted
at OMC+5%)
Unsoaked Soaked Unsoaked Soaked 0day
curing
7 days
curing
28
days
curing
1 0 4.3 2.6 130
2 3 6.8 11.6 135 210 226
-
76
3 6 8.93 12.9 155 222 235
4 9 10.12 13.65 12.8 14.3 170 234 248
5 12 11.9 15.2 14.5 16 182 230 255
6 15 12.75 17.3 190 251 276
-
77
-
78
-
79
-
80
-
81
-
82
-
83
SOIL+6% LIME+10% RHA
0
100
200
300
400
500
600
0 2 4 6 8 10 12
PENETRATION(mm)
LO
AD
(kg)
UNSOAKED
SOAKED
-
84
-
85
-
86
-
87
-
88
-
89
-
90
-
91
-
92
UCS(SOIL+6% LIME)
0
50
100
150
200
250
0 0.05 0.1 0.15 0.2 0.25
STRAIN(%)
ST
RE
SS
(kg
/cm
2)
0-DAYS
7-DAYS
28-DAYS
-
93
-
94
UCS(SOIL+10% RHA)
0
50
100
150
200
250
0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1
STRAIN(%)
STR
ESS
(kg/c
M2)
0-DAYS
7-DAYS
28-DAYS
-
95
-
96
-
97
-
98
-
99
-
100
-
101
-
102
-
103
-
104
-
105
-
106
-
107
-
108
-
109
-
110
-
111
-
112
-
113
-
114
-
115
-
116
Variation of CBR with Lime content
at moisture content equal to OMC +
5%
0
5
10
15
20
0 10 20
% of Lime
CB
R(%
)Unsoaked
C.B.R(%)
Soaked
C.B.R.(%)
Fig 7.13(a)
Variation of UCS with varying % of Lime
content compacted at moisture content
OMC + 5%
0
50
100
150
200
250
300
0 5 10 15 20
% of Lime
UC
S(K
N/m
2)
UCS(Kpa) 0
day curing
UCS(Kpa) 7
days curing
UCS(Kpa) 28
days curing)
Fig 7.13(b)
7.4.6.2 Strength characteristics of mixed soil with varying percentage of RHA have been
presented in table 6.12 with graphical representation.
-
117
Table 7.12-Strength Characteristics of soil with varying percentage of RHA
Sl No % of
RHA
CBR(%)(compacted
at OMC+5%
moisture content
CBR(%) after 7
days curing
(compacted at
OMC+5% moisture
content
UCS(KN/m2 )
(Specimens compacted
at OMC+5%)
Unsoaked Soaked Unsoaked Soaked 0day
curing
7 days
curing
28
days
curing
1 0 4.3 2.6 130
2 5 7.35 4.8 93 175 212
3 10 7.9 6.2 11.2 8.6 99 166 195
4 15 8.2 7.9 12.25 10.3 125 235 185
5 20 8.8 10.6 143 220 168
Variation of CBR with varying % of RHA content
(compacted at moisture content OMC+5%)
0
2
4
6
8
10
12
0 10 20 30
% of RHA
CB
R(%
)
Unsoaked CBR(%)
Soaked CBR(%)
Fig 7.14(a)
-
118
Variation of UCS with varying % of RHA
content(compacted at moisture content OMC+5%)
0
50
100
150
200
250
0 10 20 30
% of RHA
UC
S(K
N/m
2)
UCS(Kpa) 0 day
curing
UCS(Kpa) 7 days
curing
UCS(Kpa) 28 days
curing
Fig 7.14(b)
7.4.6.3 Strength characteristics of mixed soil with varying percentage of Lime and RHA
have been presented in table 6.13 along with graphical representation.
Table-7.13 Strength characteristics of soil with varying percentage of Lime and
RHA
Sl
N
o
Mix proportion(% by
dry weight)
CBR(%)(%)(c
ompacted at
OMC+5%
moisture
content)
CBR(5) after
7 days curing
compacted at
OMC+5%
moisture
content)
UCS(KN/m2 )
(Specimens
compacted at OMC+5%
Soil(
%)
Lime(
%0
RHA(
%)
Unsoa
ked
Soa
ked
Unsoa
ked
Soa
ked
0
day
curi
ng
7
day
s
curi
ng
28 days
curing
0 0 4.3 2.6 130
3 5 8 12.5 9.2 13.1 155 178 230
-
119
3 10 12.85 17 205 244 260
3 15 12 12 13.3 14 106 116 190
3 20 12.4 11.4
5
90 98 145
6 5 9.26 15 11.2 16 158 236 332
6 10 12.95 17.4 146 205 210
6 15 14.4 20 16.3 19.8 110 175 196
6 20 12.6 15.6 87 150 166
9 5 9.8 15.4 13.2 17.2 172 164 260
9 10 12.4 23.1
8
175 242 296
9 15 11.53 20.6
5
14.3 22.3