Stabilization of Expansive Soils using Alkali Activated Fly Ash A thesis

Stabilization of Expansive Soils using Alkali Activated Fly Ash  A thesis
Stabilization of Expansive Soils using Alkali Activated
Fly Ash
A thesis
Submitted by
Partha Sarathi Parhi
(212CE1479)
In partial fulfillment of the requirements
for the award of the degree of
Master of Technology
In
Civil Engineering
(Geotechnical Engineering)
Department of Civil Engineering
National Institute of Technology Rourkela
Odisha -769008, India
May 2014
1
Stabilization of Expansive Soils using Alkali Activated
Fly Ash
A thesis
Submitted by
Partha Sarathi Parhi
(212CE1479)
In partial fulfillment of the requirements
for the award of the degree of
Master of Technology
In
Civil Engineering
(Geotechnical Engineering)
Under the Guidance of
Dr. S.K Das
Department of Civil Engineering
National Institute of Technology Rourkela
Odisha, -769008, India
May 2014
2
Dedicated to my Grandfather
Late Shri. Udaya Narayan Parhi,
who has been a constant inspiration for me.
3
DEPARTMENT OF CIVIL ENGINEERING
NATIONAL INSTITUTE OF TECHNOLOGY
ROURKELA, ODISHA-769008
CERTIFICATE
This is to certify that the thesis entitled, “Stabilization of Expansive
Soils using Alkali Activated Fly Ash” is submitted by PARTHA
SARATHI PARHI, bearing Roll No. 212CE1479 in partial
fulfillment of the requirements for the award of Master of Technology
degree in Civil Engineering with specialization in “Geotechnical
Engineering” during 2012-2014 session at the National Institute of
Technology, Rourkela is an authentic work carried out by him under
my supervision and guidance.
To the best of my knowledge, the matter embodied in the thesis has
not been submitted to any other University/Institute for the award of
any degree or diploma.
Date: 26-May-2014
Place: NIT, Rourkela, Odisha
Dr. S.K Das
Department of Civil Engineering
National Institute of Technology,
Rourkela
I
ACKNOWLEDGEMENTS
It would not have been possible to complete the thesis without the
help and support of the kind people around me, to only some of whom
it is possible to give particular mention here.
First and foremost, I would like to express my gratitude and
sincere thanks to my esteemed supervisor Dr. Sarat Kumar Das for
his consistent guidance, valuable suggestions and encouragement
throughout the work and in preparing this thesis.
His inspiring words always motivated me to do hard labour which
helped me to complete my work in time.
I am grateful to the Dept. of Civil Engineering, NIT Rourkela,
for giving me the opportunity to execute this project, which is an
important part of the curriculum in M.Tech programme.
I also thank my friends who have directly or indirectly helped in
my project work. Many special thanks to my senior Lasyamayee
Garnayak and my friend Rupashree Sahoo for their help & cooperation with me in my work.
I would also like to thank all the Laboratory staff of Geotechnical
engineering, Environmental Engineering and Physics Dept., for their
help, without which this work would not have been possible to
execute.
Last but not the least I would like to thank my family for
providing me this platform for study and their support as and when
required.
PARTHA SARATHI PARHI
ii
ABSTRACT:-
This research work presents the efficacy of sodium based alkaline activators and class F fly
ash as an additive in improving the engineering characteristics of expansive Black cotton
soils. Sodium hydroxide concentrations of 10, 12.5 and 15 molal along with 1 Molar solution
of sodium silicate were used as activators. The activator to ash ratios was kept between
between 1 and 2.5 and ash percentages of 20, 30 and 40 %, relatively to the total solids. The
effectiveness of this binder is tested by conducting the Unconfined compressive strength
(UCS) at curing periods of 3,7 and 28 days and is compared with that of a common fly ash
based binder, also the most effective mixtures were analysed for mineralogy with XRD.
Suitability of alkaline activated fly ash mix as a grouting material is also ascertained by
studying the rheological properties of the grout such as, setting time, density and viscosity
and is compared with that of common cement grouts. Results shows that the fluidity of the
grouts correlate very well with UCS, with an increase in the former resulting in a decrease in
the latter.
iii
Table of Contents
CERTIFICATE .......................................................................................................................... I
ACKNOWLEDGEMENTS .......................................................................................................ii
ABSTRACT:- .......................................................................................................................... iii
Table of Contents…………………………………………………………………………….IV
LIST OF TABLES .................................................................................................................... V
LIST OF FIGURES .................................................................................................................VI
Chapter -1................................................................................................................................... 1
Introduction ................................................................................................................................ 1
1.1 Expansive soils:- .............................................................................................................. 2
1.2 Fly Ash ............................................................................................................................. 4
1.2.1 Fly ash Generation and Disposal ............................................................................... 5
1.2.2 Fly Ash Utilization .................................................................................................... 7
1.2.3 Classification of Fly Ash ........................................................................................... 9
1.3 Alkali Activated Fly ash ................................................................................................. 11
1.3.1 Reaction Mechanism ............................................................................................... 12
1.3.2 Applications for alkali-activated fly ash .................................................................. 15
1.4 Justification of the Research .......................................................................................... 16
1.5 Objective and Scope ....................................................................................................... 16
1.6 Thesis Outline ................................................................................................................ 17
Chapter -2................................................................................................................................. 19
Literature Review..................................................................................................................... 19
2.1 INTRODUCTION .......................................................................................................... 20
2.1.1 Stabilization using fly ash........................................................................................ 20
2.1.2 Stabilization using quarry dust ................................................................................ 24
2.1.3 Stabilization using rice husk ash ............................................................................. 25
2.1.4 Stabilization using Copper Slag (CS) ..................................................................... 27
2.1.5 Stabilization using silica fume (SF)........................................................................ 28
2.1.6 Stabilization using other industrial wastes ............................................................ 29
2.1.7 Alkali activated Fly Ash: ......................................................................................... 43
Chapter -3................................................................................................................................. 46
Materials and Methodology ..................................................................................................... 46
3.1 Materials ......................................................................................................................... 47
iv
3.1.1 Expansive Soil:-....................................................................................................... 47
3.1.2 Fly ash:- ................................................................................................................... 49
3.1.3 Activator solution .................................................................................................... 51
3.2 Methodology Adopted:- ................................................................................................. 51
Chapter -4................................................................................................................................. 58
Results on stabilization of expansive soils with fly ash ........................................................... 58
4.1 Introduction: ................................................................................................................... 59
4.2 Results ............................................................................................................................ 60
Chapter -5................................................................................................................................. 67
Results on stabilization of expansive soils with activated fly ash ........................................... 67
5.1 Introduction: ................................................................................................................... 68
5.2 Results ................................................................................................................................ 68
Chapter -6................................................................................................................................. 88
Comparison of results .............................................................................................................. 88
Chapter - 7................................................................................................................................ 98
Study of rheological properties of alkali activated fly ash ...................................................... 98
7.1 Setting time .................................................................................................................... 99
7.2 Viscosity ......................................................................................................................... 99
Chapter - 8.............................................................................................................................. 100
Conclusions and Future Scope ............................................................................................... 100
8.1 Summary ...................................................................................................................... 101
8.2 Conclusions: ................................................................................................................. 101
8.3 Scope for future study. ................................................................................................. 102
References:- ........................................................................................................................... 103
LIST OF TABLES
Table 1.1 Production and utilization of fly ash in different country…………………………..8
Table 1.2 Utilization of fly ash for different purpose Data source……………………………9
Table 1.3 Chemical requirement of Class C and Class F fly ashes…………………………..10
Table 2.1 Comprehensive study on the stabilization of Expansive soil
using industrial waste………………………………………………………….35-42
v
Table 3.1 Geotechnical properties of expansive soil…………………………………………47
Table 3.3 Details of Alkali activated fly ash mixed soil specimens……………………...53-54
Table 3.4 Details of fly ash mixed soil specimens…………………………………………...56
Table 4.1 UCS results of F-15-20, F-15-30, F-15-40…………………………………….…..60
Table 4.2 UCS results of F-20-20, F-20-30, F-20-40………………………………………...61
Table 4.3 UCS results of F-25-20, F-25-30, F-25-40……………………………………..….62
Table 4.4 UCS results of all Fly ash Samples……………………………………………..…63
Table 5.1 UCS results of AF-100-20-15, AF-100-30-15, AF-100-40-15……………………65
Table 5.2 UCS results of AF-100-20-20, AF-100-30-20, AF-100-40-20……………………66
Table 5.3 UCS results of AF-100-20-25, AF-100-30-25, AF-100-40-25……………………67
Table 5.4 UCS results of AF-125-20-15, AF-125-30-15, AF-125-40-15……………………68
Table 5.5 UCS results of AF-125-20-20, AF-125-30-20, AF-125-40-20…………………...69
Table 5.6 UCS results of AF-125-20-25, AF-125-30-25, AF-125-40-25……………………70
Table 5.7 UCS results AF-150-20-15, AF-150-30-15, AF-150-40-15……………………...71
Table 5.8. UCS results AF-150-20-25, AF-150-30-25, AF-150-40-25……………………...72
Table 5.9. UCS results of all 10 molal sample……………………………………………….74
Table 5.10. UCS results of all 12.5 molal sample……………………………………………75
Table 5.11. UCS results of all 15 molal sample……………………………………………...76
Table 5.12 UCS results of all AAFA Samples……………………………………………….77
Table 6.1 Comparison of UCS results of 15% water or activator containing samples…...….79
Table 6.2 Comparison of UCS results of 20% water or activator containing samples………80
Table 6.3 Comparison of UCS results of 25% water or activator containing samples………81
Table 7.1 Density and Viscosity of cement and alkaline grouts……………………………..83
LIST OF FIGURES
Figure 1.1 Major Soil Types in India……………………………………………………….. 3
vi
Figure 1.2 Schematic view of a typical coal based thermal power plant
(data source Prakash and Sridharan 2007)…………………………………………… 6
Figure 1.3 Conceptual model for alkaline activation processes……………………………..14
Figure 1.4 Descriptive model of the alkaline activation processes of fly ash………………..15
Figure 1.5 Basic outline of the thesis………………………………………………………...18
Figure 3.1 Grain size distribution curve of Soil……………………………………………...48
Figure 3.2 Standard proctor curve……………………………………………………………48
Figure 3.3 XRD analysis of Expansive soil………………………………………………….49
Figure 3.4 XRD analysis of fly ash…………………………………………………………..50
Figure 3.5 Photographic image of Samples wrapped in cling film…………………………..52
Figure 3.6 Experimental Setup of Marsh Funnel Viscometer………………………………..57
Figure 4.1 Photographic image showing test setup of UCS………………………………….59
Figure 4.2 UCS results of F-15-20, F-15-30, F-15-40……………………………………….60
Figure 4.3 UCS results of F-20-20, F-20-30, F-20-40……………………………………….61
Figure 4.4 UCS results of F-25-20, F-25-30, F-25-40……………………………………….63
Figure 4.5 UCS results of all Fly ash Samples……………………………………………….65
Figure 4.6 Bar chart showing the UCS results of Fly ash Samples after 3 days of curing….64
Figure 4.7 Bar chart showing the UCS results of Fly ash Samples after 7 days of curing….65
Figure 4.8 Bar chart showing the UCS results of Fly ash Samples after 28 days of curing..65
Figure 5.1 UCS results of AF-100-20-15, AF-100-30-15, AF-100-40-15…………………...69
Figure 5.2 UCS results of AF-100-20-20, AF-100-30-20, AF-100-40-20…………………...70
Figure 5.3 UCS results of AF-100-20-25, AF-100-30-25, AF-100-40-25…………………...71
Figure 5.4 UCS results of AF-125-20-15, AF-125-30-15, AF-125-40-15…………………...72
Figure 5.5. UCS results of AF-125-20-20, AF-125-30-20, AF-125-40-20…………………..73
Figure 5.6 UCS results of AF-125-20-25, AF-125-30-25, AF-125-40-25…………………...74
Figure 5.7 UCS results of AF-150-20-15, AF-150-30-15, AF-150-40-15…………………...75
VII
Figure 5.7 UCS results AF-150-20-20, AF-150-30-20, AF-150-40-20……………………...77
Figure 5.8. UCS results AF-150-20-25, AF-150-30-25, AF-150-40-25……………………..78
Figure 5.9. UCS results of all 10 molal sample……………………………………………...79
Figure 5.10. UCS results of 10 molal sample (3 Days curing)………………………………81
Figure 5.11. UCS results of 10 molal sample (7 Days curing)………………………………81
Figure 5.12. UCS results of 10 molal sample (28 days curing)……………………………...81
Figure 5.13. UCS results of all 12.5 molal sample…………………………………………..82
Figure 5.14. UCS results of 12.5 molal sample (3 Days curing)…………………………….83
Figure 5.15. UCS results of 12.5 molal sample (7 Days curing)…………………………….83
Figure 5.16. UCS results of 12.5 molal sample (28 Days curing)…………………………...83
Figure 5.17 UCS results of all 15 molal Samples…………………………………………...84
Figure 5.18. UCS results of 15 molal sample (3 Days curing)………………………………84
Figure 5.19. UCS results of 15 molal sample (7 Days curing)………………………………85
Figure 5.20. UCS results of 15 molal sample (28 Days curing)……………………………..85
Figure 6.1 Comparison of UCS results of fly ash treated and AAFA treated soil samples,
containing 15% water or activator……………………………………………………………90
Figure 6.2 Comparison of UCS results of fly ash treated and AAFA treated soil samples,
containing 15% water or activator (3 Days Curing Period)………………………………….91
Figure 6.2 Comparison of UCS results of fly ash treated and AAFA treated soil samples,
containing 15% water or activator (3 Days Curing Period)………………………………….91
Figure 6.4 Comparison of UCS results of fly ash treated and AAFA treated soil samples,
containing 15% water or activator (28 Days Curing Period)………………………………...92
Figure 6.5 Comparison of UCS results of fly ash treated and AAFA treated soil samples,
containing 20% water or activator……………………………………………………………93
VIII
Figure 6.6 Comparison of UCS results of fly ash treated and AAFA treated soil samples,
containing 20% water or activator (3 Days Curing Period)………………………………….93
Figure 6.7 Comparison of UCS results of fly ash treated and AAFA treated soil samples,
containing 20% water or activator (7 Days Curing Period)………………………………….94
Figure 6.8 Comparison of UCS results of fly ash treated and AAFA treated soil samples,
containing 20% water or activator (28 Days Curing Period)………………………………...94
Figure 6.9 Comparison of UCS results of fly ash treated and AAFA treated soil samples,
containing 25% water or activator……………………………………………………………95
Figure 6.10 Comparison of UCS results of fly ash treated and AAFA treated soil samples,
containing 25% water or activator (3 Days Curing Period)………………………………….96
Figure 6.11 Comparison of UCS results of fly ash treated and AAFA treated soil samples,
containing 25% water or activator (7 Days Curing Period)………………………………….96
Figure 6.12 Comparison of UCS results of fly ash treated and AAFA treated soil samples,
containing 25% water or activator (28 Days Curing Period)………………………………...97
IX
Chapter -1
Introduction
1
1.1 Expansive soils:Expansive soils also known as swelling soils or shrink-swell soils are the terms applied to
those soils, which have a tendency to swell and shrink with the variation in moisture content.
As a result of which significant distress in the soil occurs, causing severe damage to the
overlying structure. During monsoon‟s, these soils imbibe water, swell, become soft and their
capacity to bear water is reduced, while in drier seasons, these soils shrinks and become
harder due to evaporation of water. These types of soils are generally found in arid and semiarid regions of the world and are considered as a potential natural hazard, which if not treated
well can cause extensive damages to not only to the structures built upon them but also can
cause loss of human life. Soils containing the clay minerals montomorillonite generally
exhibit these properties. The annual cost of damage to the civil engineering structures caused
by these soils are estimated to be ₤ 150 million in the U.K., $ 1,000 million in the U.S. and
many billions of dollars worldwide.
Expansive soils also called as Black soils or Black cotton soils and Regur soils are mainly
found over the Deccan lava tract (Deccan Trap) including Maharashtra, Madhya Pradesh,
Gujarat, Andhra Pradesh and in some parts of Odisha, in the Indian sub-continent. Black
cotton soils are also found in river valley of Tapi, Krishna, Godavari and Narmada. In the the
north western part of Deccan Plateau and in the upper parts of Krishna and Godavari, the
depth of black soil is very large. Basically these soils are residual soils left at the place of
their formation after chemical decomposition of the rocks such as basalt and trap. Also these
type of soils are formed due to the weathering of igneous rocks and the cooling of lava after a
volcanic eruption. These soils are rich in lime, iron, magnesia and alumina but lack in the
phosphorus, nitrogen and organic matter.
2
Their colour varies from black to chestnut brown, and basically consists of high percentage of
clay sized particles. On an average, 20% of the total land area of our country is covered with
expansive soils. Because of their moisture retentiveness, these soils are suitable for dry
farming and are suitable for growing cottons, cereals, rice, wheat, jowar, oilseeds, citrus fruits
and vegetables, tobacco and sugarcane.
During the last few decades damage due to swelling action has been clearly observed in the
semiarid regions in the form of cracking and breakup of pavements, roadways, building
foundations, slab-on-grade members, channel and reservoir linings, irrigation systems, water
lines, and sewer lines.
Figure 1.1 Major Soil Types in India
3
1.2 Fly Ash
Fly ash is a waste material, which is extracted from the flue gases of a coal fired furnace.
These have close resemblance with the volcanic ashes, which were used as hydraulic cements
in ancient ages. These volcanic ashes were considered as one of the best pozzolans used till
now in the world.
Now a day due to rapid urbanization and industrialization the demand of power supply has
been grown up, this results in setting up of a numerous number of thermal power plants.
These thermal power plants use coal to produce electricity and after the coal is burnt,
whatever mineral residue is left is called as Fly ashes. These fly ashes are collected from the
Electro static precipitator (ESPs) of the plants.
Safe disposal and management of fly ash are the two major issues concerned with the
production of fly ash. Generally the wastes which are generated from the industries possess
very complex characteristics and are very hazardous, therefore it is necessary to safely and
effectively dispose these wastes, so that it will not disturb the ecological system and will not
cause any catastrophe to natural and human life. There should be provision of pre-treatment
of these industrial wastes before its disposal and storage; otherwise it will cause
environmental pollution.
Generally the fly ashes are micro sized particles which essentially consist of alumina, silica
and iron. These particles are generally spherical in size, which makes them easy to flow and
blend, to make a suitable mixture. The fly ash contains both amorphous and crystalline nature
of minerals. Its composition varies according to the nature of the coal burned and basically is
a non-plastic fine silt. At present, the generation of fly ash is far in excess of its utilization.
Fly ash is also a potential material for waste liners. In combination with lime and bentonite,
fly ash can also be used as a barrier material
4
1.2.1 Fly ash Generation and Disposal
For generation of steams, generally coal is used as a fuel in thermal power plants. In the past
coal in the forms of lumps were used to generate steam from the furnaces of boilers, but that
method proves to be non-energy efficient. Hence to optimize the energy from coal mass, the
thermal power plants use pulverized coal mass. Firstly the pulverized coal mass is injected
into combustion chamber, where it burns efficiently and instantly. The output ash is known as
fly ash, which consists of molten minerals. When the coal ash moves along with the flue
gases, the air stream around the molten mass makes the fly ash particle spherical in shape.
The economizer is subjected, which recovers the heat from fly ash and stream gases. During
this process, the temperature of fly ashes reduced suddenly. If the temperature falls rapidly,
the fly ashes are resulting amorphous or glassy material and if the cooling process occurs
gradually, the hot fly ashes becomes more crystalline in nature. It shows that the implements
of economizer, improves its reactivity process.
When fly ash is not subjected to economizer, it forms 4.3% soluble matter and pozzolanic
activity index becomes 94%. When it subjected to economizer, it forms 8.8% soluble matter
and pozzolanic activity index becomes 103%. Finally, the fly ashes are removed from the flue
gases by mechanical dust collector, commonly referred to electrostatic precipitator (ESPs) or
scrubbers. The flue gases which are almost free from fly ashes are subjected to chimney into
the atmosphere.
5
Atmosphere
Flue Gas
Electrostatic
Precipitator
Coal
Boiler
Mechanical
Dust
Collector
Stack
Fly Ash
Air
Bottom
Ash
Slag
Tank
Scrubber
Fly Ash
Makeup
Water
Hopper of
Mechanical
Collector
Hopper of
Electrostatic
Precipitator
Slurry
Lake or
River
Ash Pond
Over
flow
Fig1.2 Schematic view of a typical coal based thermal power plant (data source Prakash and Sridharan
2007)
The ESPs have the more efficiency about 90% - 98% for the removal of lighter and finer fly
ash particles. Generally ESPs consists of four to six hoppers, which are known as field and
the fineness of fly ash particles are proportional to number of fields available. Hence, if fly
ashes are collected from first hopper, the specific surface area found to be 2800 cm2/gm,
where the collection is from last hopper, it is high about 8200 cm2/gm. The pulverized coal
being burnt, 80% of coal ashes are removed from flue gases and it recovers as fly ashes, next
20% of coal ashes, if coarser in size, and then collected from bottom of the furnace. This
material is called as bottom ash. This can be removed in dry form or it can be collected from
water filled hopper, from the bottom of the furnace. When sufficient amount of bottom ash
filled the hopper, it can transferred by water jets or water sluice to a disposal pond, where it is
6
called as pond ash. Fig1.1 gives the idea of systematically idea of disposal of coal ash, in a
coal base thermal power plant.
1.2.2 Fly Ash Utilization
Utilization of fly ash in particular, can be broadly grouped into three categories.

The Low Value Utilizations includes, Road construction, Embankment and dam
construction, back filling, Mine filling, Structural fills, Soil stabilization, Ash dykes
etc.

The Medium Value Utilizations includes Pozzolana cement, Cellular cement,
Bricks/Blocks, Grouting, Fly ash concrete, Prefabricated building blocks, Light
weight aggregate, Grouting, Soil amendment agents etc.

The High Value Utilizations includes Metal recovery, Extraction of magnetite, Acid
refractory bricks, Ceramic industry, Floor and wall tiles, Fly ash Paints and
distempers etc.
Instead of these, there is large wastage of fly ash material, so large number of technologies
developed for well management of fly ashes. This utilization of fly ash increased to 73 MT
upto the year 2012. Fly ash has gained acceptance from the year 2010-12. The present
production of fly ashes in the country India are about 130 MT per year and expected to
increase by 400 MT by year 2016-17 by 2nd annual international summit for FLYASH
Utilization 2012 scheduled on 17th & 18th January 2013 at NDCC II Convention Centre,
NDMC Complex, New Delhi.
7
Table1.1 Production & Utilization of fly ashes in different country
Ref: Alam and Akhtar , Int Jr of emerging trends in engineering and development , Vol.1 [2] (2011)
Country
Annual ash production,
Ash utilization in %
MT
India
131
56
China
100
45
Germany
40
85
Australia
10
85
France
3
85
Italy
2
100
USA
75
65
UK
15
50
Canada
6
75
Denmark
2
100
Netherland
2
100
From the above Table1.1, the fly ash utilization in India is 56% for the country during the
year 2010-12, hence rest of the fly ashes are waste material. Now, it‟s necessary to use all of
fly ash, considering its adverse effect on environment. Lots of effort has been made to utilize
the fly ash upto 100%. For this mission, energy foundation announces 2nd international
summit on 2013 for fly ash utilization. The mission is also gathering some knowledge,
information about solution for development of suitable utilization of fly ash. The well
planned coal utilization, concentrated on its bulk utilization. This is possible only when, we
8
make geotechnical applications such as back filling, embankment construction, and pavement
construction like this. We can utilize more than 60% fly ash for low value applications, if
execution is proper.
From, present scenario, India depend 65-70% production of electricity with coal based power
plant, in which the fly ash production in India is, 110 MT/year. Table 1.2 shows the current
ash utilization in India.
Table 1.2 Utilization of fly ash for different purpose Data source: Ministry of Environment & Forests
Mode of Fly Ash Applications
% Utilization
Dykes
35
Cement
30
Land Development
15
Building
15
Others
5
1.2.3 Classification of Fly Ash
After Pulverizations, the fuel ash extract from flue gases, by electrostatic precipitator is called
fly ash. It is finest particles among Pond ash, Bottom ash and Fly ash. The fly ashes are
extracted from, high stack chimney. Fly ash contains non-combustible particulate matter,
with some of unburned carbon. Fly ashes are generally contains silt size particles. Based on
lime reactivity test, fly ashes are classified in four different types, as follows:

9
Cementitious fly ash

Cementitious and pozzolanic fly ash

Pozzolanic fly ash

Non-pozzolanic fly ash
The fly is called cementitious, when it has free lime and negligible reactive silica. A
pozzolanic fly ash is one which has reactive silica and negligible free lime content. The
cementitious and pozzolanic fly ash contains, both free lime and reactive silica
predominantly. Non-pozzolanic fly ash contains neither of free lime nor of reactive silica.
The non pozzolanic fly ash do not take part in self cementing or pozzolanic reactions. Main
difference is that, cementitious material hardens, when come in contact with water and
pozzolanic fly ash hardens only after , get in contact with activated lime with water. The
second and third category of fly ashes found widely.
Another way of classification of fly ash is that, class C and class F category of fly ashes,
based upon chemical composition. Class C category of fly ashes obtained from burning
lignite and sub-bituminous type of coal, which contains more than 10% of calcium oxide.
Class F category of fly ashes obtained from, burning bituminous and anthracite type of coal,
which contains less than 10% of calcium oxide. The chemical compositions of any fly ashes,
which are categorize into class C or class F fly ashes are as follows in Table 1.3:
Table 1.3 Chemical requirement of class C and class F fly ashes (data source: ASTM C618-94a)
Fly ash
Particulars
Class F
Class C
SiO2 + Al2O3 + Fe2O3
% minumum
70.0
50.0
SO3
% maximum
5.0
5.0
MC
% maximum
3.0
3.0
LOI
% maximum
6.0
6.0
10
1.3 Alkali Activated Fly ash
The alkali activation of waste materials has become an important area of research in many
laboratories because it is possible to use these materials to synthesize inexpensive and
ecologically sound cement like construction materials. Alkali activated fly ashes is the cement for
the future. The alkali activation of waste materials is a chemical process that allows the user to
transform glassy structures (partially or totally amorphous and/or metastable) into very compact
well-cemented composites.
Alkaline activation is a chemical process in which a powdery alumina-silicate such as fly ash
is mixed with an alkaline activator to produce a paste capable of setting and hardening within
a reasonably short period of time.
The alkaline activation of fly ash is consequently of great interest in the context of new and
environmentally friendly binders with properties similar to or that improve on the
characteristics of conventional materials.
In general terms, alkaline activation is a reaction between alumina-silicate materials and
alkali or alkali earth substances, namely: ROH, R(OH)2), R2CO3, R2S, Na2SO4, CaSO4.2H2O,
R2.(n)SiO2, in which R represents an alkaline ion like sodium (Na) or potassium (K), or an
alkaline earth ion like Ca. It can be described as a poly-condensation process, in which the
silica (SiO2) and alumina (AlO4) tetraedrics interconnect and share the oxygen (O) ions. The
process starts when the high hydroxyl (OH) concentration of the alkaline medium favours the
breaking of the covalent bonds Si–O–Si, Al–O–Al and Al–O–Si from the vitreous phase of
the raw material, transforming the silica and alumina ions in colloids and releasing them into
the solution. The extent of dissolution depends upon the quantities and nature of the alumina
11
and silica sources and the pH levels. In general, minerals with a higher extent of dissolution
will result in higher compressive strength after the process is complete.
At the same time, the alkaline cations Na+, K+ or Ca2+ act like the building blocks of the
structure, compensating the excess negative charges associated with the modification in
aluminium coordination during the dissolution phase.
1.3.1 Reaction Mechanism
A highly simplified diagram of the reaction mechanism in alkaline activation process is
shown in figure 1.3 which outlines the key processes occurring in the transformation of a
solid aluminosilicate source into a synthetic alkali aluminosilicate (N-A-S-H) gel.
For the sake of simplicity, the figure does not show the grinding or heating of raw materials
required to vary the reactivity of aluminium in the system. Though presented linealy, these
processes essentially occur concurrently. The dissolution of the solid aluminosilicate source
by alkaline hydrolysis (consuming water) yields aluminate and silicate species. The surface
dissolution of solid particles and the concomitant release of (very likely monomeric) alumina
and silica into the solution have always been assumed to be the mechanism responsible for
the conversion of the solid particles during alkaline activation.
Once dissolved, the species released are taken up into the aqueous phase, which may contain
silica, a compound present in the activating solution. A complex mix of silicate, aluminate
and aluminosilicate species is thereby formed, whose equilibrium in these solutions has been
studied extensively. Amorphous aluminosilicate dissolves rapidly at high pH, quickly
generating a supersaturated aluminosilicate solution. In concentrated solutions this leads to
the formation of a gel as the oligomers in the aqueous phase condense into large networks.
This process releases the water that was nominally consumed during dissolution. Water then
plays the role of a reaction medium while nonetheless residing inside gel pores. This type of
12
gel structure is commonly referred to as biphasic, the two phases being the aluminosilicate
binder and water.
The time required for the supersaturated alumionosilicate solution to form a continuous gel
varies considerably, depending on raw material processing conditions, solution composition
and synthesis condition. After the gel forms, rearrangement and reorganisation continue in
the system as intra-connectivity increases in th gel network. The end result is the 3-D
aluminosilicate network commonly attributed to N-A-S-H gels. This is depicted in Figure 1.3
in the form of multiple „gel‟ stages, consistent with recent experimental observations. And
numerical modelling for fly ash based materials. Figure 1.3 describes the activation reaction
as the outcome of two successive, process-controlling stages. The first, nucleation or
dissolution of the fly ash and the formation of polymeric series, is highly dependent on the
thermodynamic and kinetic parameters. Growth is the stage during which the nuclei reach a
critical size and crystals begin to develop. These structural reorganisation processes
determine the microstructure and pore distribution of the material, which are critical to
determining many physical properties.
When the fly ashes are submitted to the alkaline solution, a dissolution process of the Al and
Si occurs. Then the higher molecules condense in a gel (polymerization and nucleation) and
the alkali attack opens the spheres exposing small spheres on the inside which will be also
dissolved until the spheres, became almost dissolved with the formation of reaction products
inside and outside the sphere (Fig 1.4).
13
Fig 1.3 Conceptual model for alkaline activation processes
14
Fig 1.4 Descriptive model of the alkaline activation processes of fly ash
1.3.2 Applications for alkali-activated fly ash
The most recent research findings have confirmed the following:

Concretes made with these materials can be designed to reach compressive strength
values of over 40 Mpa after short thermal curing times.

Concrete made with alkali-activated fly ash performs as well as traditional concrete
and even better in some respects, exhibiting less shrinkage and a stronger bond
between the matrix and the reinforcing steel.

In addition to its excellent mechanical properties, the activated fly ash is particularly
durable and highly resistant to aggressive acids, the aggregate-alkali reaction and fire.

15
This family of materials fixes toxic and hazardous substances very effectively.
1.4 Justification of the Research
In India, almost 20% of the total area is covered by expansive soil, now due to rapid
industrialization and huge population growth of our country, there is a scarcity of land, to
meet the human needs. And also the cost of rehabilitation and retrofitting of the civil
engineering structures founded over these soils are increasing day by day. On the other hand,
the safe disposal of fly ash from thermal power industries has been a challenging issue
demanding urgent solution because of the decline effect of these materials on the
environment and the hazardous risk it pose to the health of humanity. However, production of
cement require lime-stone and with the rate with which we are utilising cement, the day is not
so far when the lime stone mines will get depicted, and this is a matter of fact that for every 1
kg of cement manufacturing, 1 kg of carbon dioxide is released into the atmosphere, which in
turn increases the carbon foot print and also possess serious threat to the global warming.
Thus there is a need to find out alternative binder, which is environmental friendly as well as
depended like cements.
Hence, this research is justifiable in the use of alkali-activated fly ash to stabilize Black
Cotton soil.
1.5 Objective and Scope
The objective of the current research work is to ascertain the suitability of alkali-activated fly
ash as a soil stabilizing agent.
SCOPE:.
 Preparation of alkali-activated fly ash by using sodium silicate and 10, 12.5 and 15
molal sodium hydroxide solutions.
 Evaluation of unconfined compressive strength of fly ash treated soil on an interval of
3, 7 and 28 days (mixed with 20, 30 and 40% fly ash with total solid to water ratio
ranging from 0.15 to 0.25)
16
 Evaluation of unconfined compressive strength of alkaline activated fly ash treated
soil on an interval of 3, 7 and 28 days (mixed with 20, 30 and 40% fly ash with total
solid to activator ratio ranging from 0.15 to 0.25).
 Rheological Study for assessment of alkali-activated solution as a grouting material.
This research is focused on stabilizing black cotton soil treated with various percentages
of Fly Ash (20%, 30% and 40 by dry weight of soil, and water content varying from 15%
to 30%) and alkali-activated fly ash (containing 20%, 30% and 40 by dry weight of soil,
activator to total solids ratio varying from 15% to 25%).
1.6 Thesis Outline
This thesis consists of eight chapters and the chapters has been organised in the following
order. After brief introduction in chapter 1, the Literature review is presented in the chapter 2
and the materials and methodology are described in the chapter 3.
Chapter 4 and 5 describes the results of stabilisation of expansive soils with application of
Fly ash and alkali-activated fly ash and a comparison is made between the results of the two
admixtures is also presented in chapter 6. In Chapter 7, the rheological studies of alkaliactivated fly ash has been presented, while in chapter 8 conclusions drawn from various
studies and scope for the future studies are presented. The general layout of the thesis work
based on each chapter is presented in a flow diagram as shown below.
17
CHAPTER 1
INTRODUCTION
CHAPTER 2
LITERATURE REVIEW
CHAPTER 3
MATERIALS AND
METHODOLOGY
CHAPTER 4
CHAPTER 5
CHAPTER 6
CHAPTER 7
CHAPTER 7
Figure 1.5 Basic outline of the thesis.
18
RESULTS ON
STABILIZATION OF
EXPANSIVE SOILS WITH
FLY ASH ONLY
RESULTS ON
STABILIZATION OF
EXPANSIVE SOILS WITH
ALKALI ACTIVATED FLY
ASH.
COMPARISION OF RESULTS
STUDY OF RHEOLOGICAL
PROPERTIES OF ALKALI
ACTIVATED FLY ASH
CONCLUSIONS AND SCOPE
FOR THE FUTURE STUDY
Chapter -2
Literature Review
19
2.1 INTRODUCTION
Stabilization is one of the methods of treating the expansive soils to make them fit for
construction. Variety of stabilizers may be divided into three groups (Petry 2002): (a)
traditional stabilizers (lime, cement etc.), (b) by-product stabilizers (fly ash, quarry dust,
phosphor-gypsum, slag etc.) and (c) non-traditional stabilizers (sulfonated oils, potassium
compounds, polymer, enzymes, ammonium chlorides etc.). Disposal of large quantities of
industrial by products as fills on disposal sites adjacent to industries not only requires large
space but also create a lot of geo-environment problems. Attempts are being made by various
organizations and researchers to use them in bulk at suitable places. Stabilization of
expansive soil is one way of utilization of these by products. Some of the research work
conducted by earlier researchers on the above has been described below.
2.1.1 Stabilization using fly ash
Sharma et al. (1992) studied stabilization of expansive soil using mixture of fly ash,
gypsum and blast furnace slag. They found that fly ash, gypsum and blast furnace slag in the
proportion of 6: 12: 18 decreased the swelling pressure of the soil from 248 kN/m 2 to 17
kN/m2 and increased the unconfined compressive strength by 300%.
Srivastava et al. (1997) studied the change in micro structure and fabric of expansive soil due
to addition of fly ash and lime sludge from SEM photograph and found changes in micro
structure and fabric when 16% fly ash and 16% lime sludge were added to expansive soil.
Srivastava et al. (1999) have also described the results of experiments carried out to study the
consolidation and swelling behaviour of expansive soil stabilized with lime sludge and fly
ash and the best stabilizing effect was obtained with 16% of fly ash and 16% of lime sludge.
20
Cokca (2001) used up to 25% of Class-C fly ash (18.98 % of CaO) and the treated specimens
were cured for 7 days and 28 days. The swelling pressure is found to decrease by 75% after 7
days curing and 79% with 28 days curing at 20% addition of fly ash.
Pandian et al. (2001) had made an effort to stabilize expansive soil with a class –F Fly ash
and found that the fly ash could be an effective additive (about 20%) to improve the CBR of
Black cotton soil (about 200%) significantly.
Turker and Cokca (2004) used Class C and Class F type fly ash along with sand for
stabilization of expansive soil. As expected Class C fly ash was more effective and the free
swell decreased with curing period. The best performance was observed with soil , Class C
fly ash and sand as 75% , 15% and 10% respectively after 28 days of curing.
Satyanarayana et al. (2004) studied the combined effect of addition of fly ash and lime on
engineering properties of expansive soil and found that the optimum proportions of soil: fly
ash: lime should be 70:30:4 for construction of roads and embankments.
Phani Kumar and Sharma (2004) observed that plasticity, hydraulic conductivity and swelling
properties of the expansive soil fly ash blends decreased and the dry unit weight and strength
increased with increase in fly ash content. The resistance to penetration of the blends increased
significantly with an increase in fly ash content for given water content. They presented a statistical
model to predict the undrained shear strength of the treated soil.
Baytar (2005) studied the stabilization of expansive soils using the fly ash and desulphogypsum obtained from thermal power plant by 0 to 30 percent. Varied percentage of lime (0
to 8%) was added to the expansive soil-fly ash-desulphogypsum mixture. The treated samples
were cured for 7 and 28 days. Swelling percentage decreased and rate of swell increased with
increasing stabilizer percentage. Curing resulted in further reduction in swelling percentage
21
and with 25 percent fly ash and 30 percent desulphogypsum additions reduced the swelling
percentage to levels comparable to lime stabilization.
Amu et al. (2005) used cement and fly ash mixture for stabilization of expansive clayey Soil.
Three different classes of sample (i) 12% cement, (ii) 9% cement + 3% fly ash and (iii)
natural clay soil sample were tested for maximum dry densities (MDD), optimum moisture
contents (OMC), California bearing ratio (CBR), unconfined compressive strength (UCS) and
the undrained Triaxial tests. The results showed that the soil sample stabilized with a mixture
of 9% cement + 3% fly ash is better with respect to MDD, OMC, CBR, and shearing
resistance compared to samples stabilized with 12% cement, indicating the importance of fly
ash in improving the stabilizing potential of cement on expansive soil.
Sabat et al. (2005) observed that fly ash-marble powder can improve the engineering
properties of expansive soil and the optimum proportion of soil: fly ash: marble powder was
65:20: 15
Punthutaecha et al. (2006) evaluated class F fly ash, bottom ash, polypropylene fibers, and
nylon fibers as potential stabilizers in enhancing volume change properties of sulfate rich
expansive subgrade soils from two locations (Dallas and Arlington) in Texas, USA. Ash
stabilizers showed improvements in reducing swelling, shrinkage, and plasticity
characteristics by 20–80% , whereas fibers treatments resulted in varied improvements. In
combined treatments, class F fly ash mixed with nylon fibers was the most effective treatment
on both soils. They also discussed the possible mechanisms, recommended stabilizers and
their dosages for expansive soil treatments.
Phanikumar and Rajesh (2006) discussed experimental study of expansive clay beds
stabilized with fly ash columns and fly ash-lime columns. Swelling was observed in clay beds
of 100 mm thickness reinforced with 30 mm diameter fly ash columns and fly ash-lime
22
column. Heave decreased effectively with both fly ash and fly ash-lime columns, with, limestabilised fly ash yielded better results.
Wagh (2006) used fly ash, rock flour and lime separately and also in combination, in different
proportion to stabilize black cotton soil from Nagpur Plateau, India. Addition of either rock-flour or
fly ash or both together to black cotton soil improve the CBR to some extent and angle of shearing
resistance increased with reduced cohesion. However, in addition to rock-flour and fly ash when
lime is mixed to black cotton soil CBR value increases considerably with increase in both cohesion
and frictional resistance.
Phani Kumar and Sharma (2007) studied the effect of fly ash on swelling of a highly plastic
expansive clay and compressibility of another non-expansive high plasticity clay. The swell
potential and swelling pressure, when determined at constant dry unit weight of the sample
(mixture), decreased by nearly 50% and compression index and coefficient of secondary
consolidation of both the clays decreased by 40% at 20% fly ash content.
Kumar et al. (2007) studied the effects of polyester fiber inclusions and lime stabilization on
the geotechnical characteristics of fly ash-expansive soil mixtures. Lime and fly ash were
added to an expansive soil at ranges of 1–10% and 1–20%, respectively. The samples with
optimum proportion of fly ash and lime content (15% fly ash and 8% lime) based on
compaction, unconfined compression and split tensile strength, were added with 0, 0.5, 1.0,
1.5, and 2% plain and crimped polyester fibers by weight. The MDD of soil-fly ash-lime
mixes decreased with increase in fly ash and lime content. The polyester fibers (0.5–2.0%)
had no significant effect on MDD and OMC of fly ash-soil-lime-fiber mixtures. However, the
unconfined compressive strength and split tensile strength increased with addition of fibers.
23
Buhler et al. (2007) studied the stabilization of expansive soils using lime and Class C fly
ash. The reduction in linear shrinkage was better with lime stabilization as compared to same
% of Class C fly ash.
2.1.2 Stabilization using quarry dust
The quarry dust/ crusher dust obtained during crushing of stone to obtain aggregates causes
health hazard in the vicinity and many times considered as an aggregate waste.
Gupta et al. (2002) made a study on the stabilization of black cotton soil using crusher dust a waste
product from Bundelkhand region, India and optimal % of crusher dust(quarry dust) found to be
40%. There was decrease in liquid limit (54.10% to 24.2%), swelling pressure (103.6 kN/m2 to 9.4
kN/m2 ) and increases in shrinkage limit(12.05% to 18.7%), CBR value (1.91 % to 8.06% ), UCS
value (28.1 kN/m2 to 30.2 kN/m2 ) with 40% replacement of expansive soil with crusher dust.
Stalin et al. (2004) made an investigation regarding control of swelling potential of expansive
clays using quarry dust and marble powder and observed that LL and swelling pressure
decreased with increase in quarry dust or marble powder content.
Gulsah (2004) investigated the swelling potential of synthetically prepared expansive soil
(kaolinite and bentonite mixture), using aggregate waste (quarry dust), rock powder and lime.
Aggregate waste and rock powder were added to the soil at 0 to 25% by weight with lime
varying from 0 to 9% by combined weight. There was reduction in the swelling potential and
the reduction was increased with increasing percent stabilizers and days of curing.
Jain and Jain (2006) studied the effect of addition of stone dust and nylon fiber to Black
cotton soil and found that mixing of stone dust by 20% with 3% randomly distributed nylon
fibers decreased the swelling pressure by about 48%. The ultimate bearing capacity increased
and settlement decreased by inclusion of fiber to stone dust stabilized expansive soil.
24
2.1.3 Stabilization using rice husk ash
Rice husks are the shells produced during dehusking operation of paddy, which varies from
20% (Mehta 1986) to 23% (Della et al. 2002) by weight of the paddy. The rice husk is
considered as a waste material and is being generally disposed of by dumping or burning in
the boiler for processing paddy. The burning of rice husk generates about 20% of its weight
as ash (Mehta 1986). The silica is the main constituent of rice husk ash (RHA) and the quality
(% of amorphous and unburnt carbon) depend upon the burning process (Nair et al. 2006).
The RHA is defined as a pozzolanic material (ASTM C 168 ASTM 1997) due to its high
amorphous silica content (Mehta 1986).
Rajan and Subramanyam (1982) had studied regarding shear strength and consolidation
characteristics of expansive soil stabilized with RHA and lime and observed that RHA
contributes to the development of strength as a pozzolanic material when used as a secondary
additive along with lime and cement. Under soaked conditions, the soil stabilized with rice
husk ash had low strength. The RHA, lime combination also decreased the compression
index of stabilized soil.
Bhasin et al. (1988) made a laboratory study on the stabilization of Black cotton soil as a
pavement material using RHA, bagasse ash, fly ash, lime sludge and black sulphite liquor
with and without lime. The bagasse ash and black sulphite liquor are found to be not effective
as a stabilizing agent. The addition of lime sludge alone to black cotton soil improves the
CBR values marginally but reduces the UCS values. Lime sludge in combination with lime
improves the strength parameters of black cotton soil sufficiently for its use as a sub-base
material. The rice-husk ash causes greater improvement than that caused by fly ash and
bagasse ash due to presence of higher % of reactive silica in rice-husk ash in comparison to
25
fly ash and bagasse ash. In conjunction to lime both rice husk ash and fly ash improves the
properties of black cotton soil sufficiently meriting its use as a sub-base material.
Muntohar and Hantoro (2000) used rice husk ash and lime for stabilization of expansive soil
by blending them together. The RHA used were 7.5%, 10% and 12.5% and lime as 2%, 4%,
6%, 8%, 10% and 12% as replacement of expansive soil. Their PI (plasticity index) decreased
from 41.25% to 0.96% and swell potential decreased from 19.23% to insignificant with 1212.5% of RHA-lime mixture. There was also increase in CBR value (3 % to 16 %), internal
friction angle (5
0
to 240) and cohesion (54.32 kN/m2 to 157.19 kN/m2), there by increased
bearing capacity to 4131 kN/m2 from 391.12 kN/m2
Chandrasekhar et al. (2001) presented the results of laboratory and field investigations
carried out to understand the characteristics of black cotton soil with stabilizing agents like
calcium chloride and sodium silicate in comparison with conventional RHA-lime
stabilization. The RHA-lime stabilization resulted in maximum improvement and strength
compared to all other treatment. Calcium chloride treated road stretch showed maximum
reduction in ground heave compared to lime, sodium silicate and RHA stabilized stretches, but
maximum reduction in shrinkage is observed in lime treated stretch, when additives are used
individually. When additives are used in combination, Calcium chloride – sodium silicate treated
stretched showed maximum reduction in heave compared to RHA– lime and calcium chlorideRHA stabilized stretches whereas highest reduction in shrinkage is observed in RHA- lime
stabilized stretch.
Ramakrishna and Pradeep Kumar (2006) had studied combined effect of rice husk ash
(RHA) and cement on engineering properties of black cotton soil. RHA up to 15% in steps
of 5% and cement up to 12% in steps of 4% were added. RHA and cement reduced the
plasticity of the expansive soil. The dry density of soil increased marginally with increase in
26
OMC after 4% cement addition. MDD of soil decreased and OMC increased with the increase in
the proportion of RHA- cement mixes. The UCS of Black cotton soil increased linearly with
cement content up to 8% and at 12%, strength rate reduced. The soaked CBR of the soil was found
to be increased with cement and RHA addition. Similar trends to that of UCS were observed with
the increase in CBR rate. At 8% cement content, CBR value of soil was 48.57% and with
combination of RHA at 5%, 10% and 15%, the values were 54.68%, 60.56% and 56.62%,
respectively.
Sharma et al.(2008) had studied the engineering behavior of a remolded expansive clay
blended with lime, calcium chloride and Rice-husk ash . The amount of RHA, lime and
calcium chloride were varied from 0 to 16%, 0 to 5% and 0 to 2% respectively by dry weight
of soil . The effect of additives on UCS & CBR was found. The stress–strain behavior of
expansive clay improved upon the addition of up to 5% lime or 1% calcium chloride. A
maximum improvement in failure stress of 225 & 328% was observed at 4% lime & 1%
calcium chloride. A RHA content of 12% was found to be the optimum with regard to both
UCS & CBR in the presence of either lime or calcium chloride. An optimum content of 4% in
the case of lime and 1% in the case of calcium chloride was observed even in clay – RHA
mixes.
2.1.4 Stabilization using Copper Slag (CS)
Copper slag is produced as a by product of metallurgical operations in reverberatory furnaces. It is
totally inert material and its physical properties are similar to natural sand.
Al-Rawas et al. (2002) made an investigation regarding the effectiveness of using cement bypass dust, copper slag , granulated blast furnace slag, and slag-cement in reducing the
swelling potential and plasticity of expansive soils from Al-Khod
(a town located in
Northern Oman). The soil was mixed with the stabilizers at 3, 6 and 9 % of the dry weight of
27
the soil. The treated samples were subjected to liquid limit, plastic limit, swell percent and swell
pressure tests. The study showed that copper slag caused a significant increase in the swelling
potential of the treated samples. The study further indicated that cation exchange capacity and the
amount of sodium and calcium cations are good indicators of the effectiveness of chemical
stabilizers used in soil stabilization.
Saravan et al. (2005) stabilized the expansive soil using 0%, 10%, 20%, 30%, 40%, 50%,
60%, 70% and 80% of dry weight of copper slag. The MDD increased, OMC decreased with
increase in CS content and free swell index decreased by 60% corresponding to soil + 70%
CS. However, the soaked CBR improved only after addition of 2% of cement and the
expansive soil found to be suitable as a sub-grade material by utilizing 50% copper slag
waste along with 2% cement.
2.1.5 Stabilization using silica fume (SF)
Silica fume, a co-product from the production of silicon or ferrosilicon metal, is an
amorphous silicon dioxide - SiO2 which is generated as a gas in submerged electrical arc
furnaces during the reduction of very pure quartz. This gas vapor is condensed in bag house
collectors as very fine powder of spherical particles that average 0.1 to 0.3 microns in
diameter with a surface area of 17 - 30 m²/g
Dayakar et al. (2003) conducted laboratory investigation for stabilization of expansive soil
using silica fume and tannery sludge with percentage of solid wastes varying from 0, 10, 20,
30, 40, 50, 60- 70%. The addition of wastes did not improve the index properties &
maximum dry density but there was gain in strength of the expansive soil with both tannery
sludge and silica fume up to 15%.
El-Aziz et al. (2004) investigated the effect of the engineering properties of clayey soils when
blended with lime and Silica Fume (SF). Based on a series of laboratory experiments with
28
lime percentage varying from 1%, 3%, 5%, 7%, 9% and 11% and SF at 5%, 10% and 15%,
the plasticity Index and swell potential decreased from 40.25% to 0.98% and from 19.0% to
insignificant, respectively, at 11% lime and 15% of SF.
There was considerable
improvement in CBR value (3.0% to 17.0%), angle of internal friction (60 to 250) and
cohesion (55.52 kN/m2 to 157.54 kN/m2). The consolidation settlement was lowered from
0.025 to 0.007m.
Khare et al. (2005) observed that addition of silica fume and aluminum sludge did not
improve the index properties and maximum dry density of the expansive soil, but UCS values
increased up to 10%. As the above wastes/ stabilizing agent have cementitious components,
curing further increased its UCS value.
Kalkan and Akbulect (2004) studied the effect of silica fume on the permeability, swelling
pressure and compressive strength of natural clay liners. The test results showed that the compacted
clay samples with silica fume exhibit quite low permeability, swelling pressure and significantly
high compressive strength as compared to raw clay samples.
2.1.6 Stabilization using other industrial wastes
Srinivasulu and Rao (1995) studied the effect of baryte powder as a soil stabilizer and added
up to 20% of baryte powder to expansive soil. The PI, OMC and cohesion decreased and
MDD, angle of internal friction and CBR values increase with increase in baryite powder and
hence can be effectively used for any pavement construction in cohesive soil zones and for
rural roads at minimum cost.
Swami (2002) had made the feasibility study for utilization of marble dust in highway sector. The
marble dust was added up to 60% by an increment of 15% and found the optimum proportion of
expansive soil: marble powder as 75:25. Plasticity Index decreased from 25.1% to 7% with 35%
marble dust PI value at 15% and 25% marble powder were observed to be 15.37 %and 8.3%
29
respectively. The dry density increased from 17.56 kN/m3 to 18.34 kN/m3 with 45% marble dust,
but CBR value increased (4.59 to 6.81%) upto 25% marble dust and decreased with further
increase in marble powder.
Mishra and Mathur (2004) studied the stabilization of expansive soil with phosphogypsum (a
waste product from phosphoric acid industry) and observed that soil mixed with different
proportions of phosphogypsum reduces its liquid and plasticity limit thereby making the soil
more workable. The free swell of the soil reduced considerably and the CBR value of the soil
increased from 2% to 9 %, when 40% phosphogypsum was added. When the proportion of
phosphogypsum was increased beyond 40%, the mix could not be compacted properly.
Wagh et al. (2004) added sludge‟s from three type of industry textile industry, paper mill and
sugar factory, by 10%, 15%, 20% and 25% for improvement in soil properties of expansive
soil. With addition of textile industry sludge the free swell index (FSI) decreased and MDD
and UCS increased. Adding paper mill sludge UCS increased but decrease in MDD and no
considerable effect on FSI. The FSI and MDD decreased and UCS increased with addition of
sugar factory sludge.
Parsons et al. (2004) presented a summary of the performance of a wide range of soils (CH,
CL, ML, SM, and SP) treated with cement kiln dust (CKD), to improve the texture, increase
strength and reduce swell characteristics. Treatment with cement kiln dust was found to be an
effective; strength and stiffness were improved and plasticity and swell potential were
substantially reduced. Durability of CKD treated samples in wet-dry testing was comparable
to that of soil samples treated with the other additives, while performance was not as good in
freeze thaw testing. CKD treated samples performed very well in leaching tests and in many
cases showed additional reductions in plasticity and some strength gains after leaching..
Koyuncu et al. (2004) used three types of ceramic waste, namely, ceramic mud wastes (CMW),
30
crushed ceramic tile wastes (CCTW) and ceramic tile dust wastes (CTDW) for stabilization of
expansive soil with Na-bentonite. Swelling pressure and swelling percent of Na-bentonite clay
mixed with 40% CCTW decreased 86% and 57%, respectively.
Al-Rawas (2004) investigated the physical, engineering, chemical and microfabric
characteristics of two soils from Oman treated with incinerator ash produced at Sultan
Qaboos University. The soils were mixed with the incinerator ash at 0%, 10%, 15%, 20%,
25% and 30% by dry weight of the soils. The results showed that the incinerator ash used was
a non-hazardous waste material. All treated samples showed a reduction in swell percent and
cohesion, and an increase in angle of internal friction with the addition of incinerator ash for
all curing periods and 20% and 30% additive showed reduction of swell percent of the soils
Amu et al. (2005) studied the effect of eggshell powder (ESP) on the stabilizing potential of
lime on an expansive soil. Based on different engineering tests the optimal percentage of
lime-ESP combination was attained at a 4% ESP + 3% lime. But, MDD, CBR value, UCS and
undrained triaxial shear strength values indicated that lime stabilization at 7% is better than the
combination of 4% ESP + 3% lime.
Mughieda et al. (2005) studied the feasibility of using composed olive mills solid by product
(COMSB), a solid byproduct which causes environmental problems, in stabilization of expansive
soil. With addition of COMSB by 2%-8% by weight, the PI, DD and UCS decreased. It was also
found that the swell potential was reduced by 56%-65% and the swelling pressure reduced by 56%72% corresponding to untreated soil. Slow direct shear test indicated that the stabilizing agent
decreased the cohesion intercept while the angle of internal friction was increased by 45%-65%.
Nalbantoglu and Iawfin (2006) studied the stabilizing effect of Olive cake residue on expansive
Soil. Olive cake residue is a by-product after olives have been pressed and olive oil extracted. Olive
cake residue was heated up to 550 OC about 1 hour and the ash produced as a result of heating was
31
added into the soil with 3, 5 and 7% by dry weight of soil. With olive cake residue upto 3%, there
was reduction in plasticity, volume change, and an increase in unconfined compressive strength, but
with further increase in olive cake residue UCS decreased and compressibility increased.
Red mud is a waste material generated by the Bayer Process widely used to produce alumina from
bauxite throughout the world. Approximately, 35% to 40% per ton of bauxite treated using the
Bayer Process ends up as red mud waste. Kalkan (2006) studied utilization of red mud as a
stabilization material for the preparation of clay liners. The test results showed that compacted clay
samples containing red mud and cement–red mud additives have a high compressive strength and
decreased hydraulic conductivity and swelling percentage as compared to natural clay samples.
Degirmenci et al. (2007) investigated phosphogypsum with cement and fly ash for soil stabilization.
Atterberg limits, standard Proctor compaction and unconfined compressive strength tests were
carried out on cement, fly ash and phosphogypsum stabilized soil samples. Treatment with cement,
fly ash and phosphogypsum generally reduces the plasticity index with increase in MDD with
cement and phosphogypsum contents, but decreased as fly ash content increased. The OMC
decreased and UCS increased with addition of cement, fly ash and phosphogypsum.
Seda et al. (2007) used waste tyre rubber for stabilization of highly expansive clays. The index
properties and compaction parameters of the rubber, expansive soil, and expansive soil-rubber
(ESR) mixture were determined. While the ESR mixture is more compressible than the untreated
soil, both the swell percent and the swelling pressure are significantly reduced by the addition of
rubber to the expansive soil. Attom et al. (2007) investigated the effect of shredded waste tire on the
shear strength, swelling and compressibility properties of the clayey soil from northern part of
Jordan. The shredded tires passed US sieve number 4 were added to the soil at 2%, 4%, 6%, and
8% by dry weight of soil. The test results showed that increasing the amount of shredded waste tires
32
increased the shear strength and decrease plasticity index, maximum dry density, permeability,
swelling pressure, swell potential and the compression index of the clayey soil.
Okagbue (2007) evaluated the potential of wood ash to stabilize clayey soil. Results showed that the
geotechnical parameters of clay soil are improved substantially by the addition of wood ash.
Plasticity was reduced by 35%, CBR, UCS increased by 23–50% and 49–67%, respectively,
depending on the compactive energy used. The highest CBR and strength values were achieved at
10% wood ash.
Peethamparan and Jain (2008) studied four CKD with different chemical and physical
characteristics in stabilizing Na-Montmorillonite Clay. All CKDs considerably decreased the
plasticity index, thereby improving the workability of the clay, while they also considerably
increased the initial pH value of clay, providing a favourable environment for further chemical
pozzolanic reaction. The addition of CKDs and subsequent compaction substantially increased the
UCS and the stiffness of the clay, thus improving its structural properties. The extent of
improvement of the clay characteristics was found to be a function of the chemical composition of
the particular CKD, specifically its free lime content. It was also found that the length of curing
period after compaction had a major role in the stabilization process
Cokca et al. (2008) had utilized granulated blast furnace slag (GBFS), and GBFS -Cement
(GBFSC) to overcome or to limit the expansion of an artificially prepared expansive soil sample
(Sample A). GBFS and GBFSC were added to Sample A in proportions of 5 to 25 percent by
weight. Effect of these stabilizers on grain size distribution, Atterberg‟s limits, swelling percentage
and rate of swell of soil samples were determined. Effect of curing on swelling percentage and rate
of swell of soil samples were also determined. Leachate analysis of GBFS, GBFSC and samples
stabilized by 25 percent GBFS and GBFSC was performed. Use of stabilizers successfully
decreased the amount of swell while increasing the rate of swell. Curing samples for 7 and 28 days
33
resulted in less swell percentages and higher rate of swell. He had concluded that GBFS and
GBFSC should not be used to stabilize expansive soils in regions near to the drinking water wells.
A concise literature review as above is presented in Table 2.1. From the studies of the available
literature it is observed that various efforts have been made to study the possible utilisation of
different industrial wastes for stabilisation of expansive soil.
34
Table 2.1
SL.No
Comprehensive study on the stabilization of expansive soil using Industrial Wastes
Types of waste
Investigation
Findings
Reference
1
Fly ash, Lime and Gypsum
SP and UCS
SP reduced and UCS of the soil increased
Sharma et al. (1992)
2
a)Fly ash and Lime sludge
a)Microstructure and
Fabric
a)Remarkable change in micro structure and fabric,
a)Srivastava etal.(1997)
b)Srivastava et al. (1999)
b)Fly ash and Lime sludge
b) Improvement in consolidation and reduction in SP
b)Consolidation and SP
3
Class-C fly ashes
SP
75% decrease in SP with 7 days curing and 79% decrease
in SP with 28 days curing
Cocka. (2001)
4
Class F Fly ash
CBR
20% addition of fly ash increased the CBR by 200%
Pandian etal.(2001)
5
Fly ash and randomly
distributed Coir fibre
CBR
CBR values are improved and fibre inclusion increases
both the strength and stiffness of the mix
Sivarama Krishna, K., et al
.(2002)
6
Class C and F fly ash with
sand
Swelling test
decrease in free swell
Turker et al. (2004)
7
Class F Fly ash and Lime
UCS, CBR and SP
UCS, CBR increased SP decreased.
SatyaNarayan et al.
(2004)
8
Class F Fly ash
PI, K, SP, MDD, resistance PI, K, SP, decreased MDD and resistance to penetration
to penetration
increased.
Phani Kumar et al.(2004)
9
Class F Fly ash and
desulphogypsum
Swelling percentage and Swelling percentage and rate of swell decreased
rate of swell
Bayter (2005)
35
SL.No
Types of waste
Investigation
Findings
Reference
10
Fly ash and cement
Compaction, CBR, Shear
Improvement in MDD, OMC, Bearing Capacity and
Shearing Resistance
Amu et al.(2005)
11
Fly ash and marble powder
UCS,CBR,SP
decrease in SP and increase in UCS and CBR
Sabat et al (2005)
12
Class F Fly ash, bottom ash, Swelling, shrinkage and Swelling and plasticity decreased , shrinkage limit
polypropylene fibers and
plasticity
increased
Nylon fiber
Punthutaecha et al.
Fly ash columns and Fly
ash –Lime column
Sp
Phani Kumar et al.
14
Fly ash, Lime and rock flour
CBR
15
Fly ash
13
(2006)
CBR increased
Sp, SP, Cc and coefficient Sp, SP, Cc and coefficient of secondary consolidation
of
secondary decreased.
consolidation.
16
Fly ash ,lime and polyster
fiber
17
Class C fly ash, Lime
Linear shrinkage
18
Crusher dust
PI, SL, CBR, UCS ,
and FSI
19
Quarry dust and Marble
powder separately
SP, Sp, LL,
36
Sp decreased
(2006)
UCS,CBR
Wagh(2006)
Phani Kumar et al.
(2007)
Increase in strength and stiff ness
Kumar et al (2007
Linear shrinkage reduced
Buhler et al.(2007)
SP PI, SP, FSI decreased, SL, CBR, UCS increased
Ps, Sp, LL decreased
Gupta et al (2002)
Stalin et al.(2004)
SL.No
Types of waste
Investigation
Findings
20
Aggregate waste, rock
powder and lime
Particle size, PI,
Swelling potential
21
Saw Dust
Atterberg’s limits, DFSI, Increased the LL, PL,, and SL,t but reduced the DFSI, CBR
value both Soaked and Unsoaked increased by almost
CBR, Shear and K
100%, a marginal increase in shear strength and increase
in K was also found.
Jain et al.(2006)
22
Rice Husk Ash (RHA) and
Lime
Consolidation, and Shear
strength
RHA slightly increased the Cv. In combination with lime it
further increased Cv. RHA in combination with lime
considerably decreases Cc
Rajan et al.(1982)
23
RHA, Fly ash, bagasse ash,
Black sulphite liquor, Lime
sludge with and without
lime
UCS and CBR
UCS and CBR increased up to addition of certain %
waste and lime and then decreased. However Black
sulphite liquor, and bagasse ash did not improved the
strength.
Bhasin et al.(1988)
24
Rice husk ash and Lime
PI, CBR, Sp Consolidation. PI, Sp, decreased, CBR,Ф, C, increased, consolidation
Shear
settlement decreased
Muntohar et al.(2000)
25
Cacl2, lime , Sodium
Field and laboratory
Investigation. UCS and
CBR(lab) In-situ heave
test & In-situ strength test
Chandrasekhar et al.
Silicate (Na2Sio3) RHA ,
Lime + RHA,
Cacl2+RHA,
(Cacl2)+ (Na2Sio3)
37
SL,
Increase in particle size and SL, reduction in PI and
swelling potential,
Reference
Lime –RHA treatment resulted in maximum improvement
in strength and highest reduction in shrinkage.
Gulsah et al.(2004)
(2001)
SL.No
26.
Types of waste
Rice husk ash and lime
Investigation
UCS and CBR
Findings
UCS and CBR values change with changes in molding
water content
Reference
Ramakrishna et al.
(2008)
27.
28.
29.
Rice husk ash , cacl2 and
lime
UCS and CBR
Cement by-pass dust,
copper slag, granulated
blast furnace slag, and
slag-cement
Sp and PI,
Copper slag, Cement
FSI,CBR
Improvement in UCS and CBR values
Sharma et al.
(2008)
Copper slag caused a significant increase in the Sp, Other
stabilizers reduced the Sp and plasticity at varying
degrees.
Al-Rawas
FSI decreased ,CBR increased
Sarvan Kumar et al.
et al.(2002)
(2005)
30.
Silica fume ,Tannery
sludge(separately)
Index
properties, Index properties and MDD did not improved.UCS
increased up to 10% addition of waste, curing further
Compaction, and UCS
increased strength
31.
Silica Fume and lime
PI, SP , CBR and Shear
32.
Silica fume
K,SP,, UCS, and lechate K, SP, decreased, UCS increased and lechate did not
test
affect.
38
Dayakar(2003)
PI, Sp, and Consolidation settlement was decreased CBR El-Aziz et al.(2004)
value, Internal friction angle and Cohesion increased.
Kalkan(2004)
SL.No
Types of waste
Investigation
Findings
Reference
33.
Silica fume, aluminium
sludge
Index properties, MDD & Index properties and MDD did not improve. UCS
UCS
increased up to 10% addition of sludge.
Khare(2005)
34.
Baryte powder
P.I. ,Compaction, shear, PI, DFS, OMC decreased, MDD, CBR increased.
UCS, CBR, DFS
Srinivasulu
PI, Compaction,
PI decreased ,MDD and
Swami et al (2002)
CBR
CBR increased
35.
Marble dust
36.
Phosphogypsum
PI. Free Swell percentage, The plasticity index of the soil goes decreasing up to 40%
UCS, Soaked CBR, Direct addition, The free swell of the soil reduced considerably
and the CBR value of the soil increased from a value of
Shear
2%, to a value of 9 %, when 40% phosphogypsum was
added.
37.
Textile industry paper mill
& sugar factory sludge
FSI,MDD,UCS
(i) Textile industry sludge -FSI decreased , MDD & UCS
increased
(1995)
Mishra(2004)
Wagh(2004)
ii)paper mill sludge- No considerable effect on FSI , UCS
increased but MDD decreased
iii)sugar factory sludge -FSI,MDD decreased but UCS
increased
38.
Cement Kiln dust
Strength ,swell, durability Improvement in properties were found but performance
and leaching
was not good in freeze –thaw cycles.
Person(2004)
39.
Crushed ceramic tile
Sp and SP
Koyuncu(2007)
39
Sp and SP of Na-bentonite clay mixed with 40%
crushed ceramic tile wastes (CCTW) decreased 86%
SL.No
Types of waste
Investigation
wastes
Findings
Reference
and 57%, respectively.
40.
Incinerator ash
LL,,PL,, Sp,, direct shear, Increase in PL, Reduction in LL, Sp, and C, and an increase
curing for 1, 7 and 14 days in Ф with the addition of incinerator ash for all curing
periods. The use of 20% and 30% additive showed clearly
and SEM
the development of aggregations that contributed to
reduction of swell per cent of the soils
41.
Eggshell Powder(ESP)
Compaction, UCS,CBR
42.
Composted olive mills
solid by product(COMSB)
Atterberg’s limits, UCS,, Decrease in PI, MDD, UCS. Sp was reduced by up to 56%
direct shear strength, to 65% and the SP was reduced by up to 55% to 72%,
standard Proctor density, decrease in C and Ф was increased by up to 45% to 67%.
and Ps
Mugheida
43.
Olive Cake residue
PI, UCS, Consolidation
An addition only 3% burned olive waste in the soil
causes a reduction in Plasticity, volume change, and
an increase in UCS, a greater amount than 3% caused
a decrease in UCS , increase in compressibility.
Nalbantoglu (2006)
44.
Red mud
PI , K, UCS, Sp
The test results show that compacted clay samples
containing red mud and cement–red mud additives have
a high compressive strength and decreased the hydraulic
conductivity and Sp as compared to natural clay samples.
Kalkan et al.(2006)
and Cement
45.
Phosphogypsum with
cement and fly ash
Atterberg’s
standard
MDD, CBR, UCS and Undrained triaxial shear strength
test all indicated that lime stabilization at 7% is better
than the combination of 4% ESP + 3% lime.
limits, Reduced the PI. , MDD increased as cement and
Proctor phosphogypsum contents increased, but decrease as
fly ash content increases. Generally optimum
40
Al-Rawas(2004)
Ammu (2005)
et al.(2005)
DegirMenci
et al.(2006)
SL.No
46.
47.
Types of waste
Waste tire rubber
Waste tire rubber
Investigation
Findings
compaction and UCS
moisture contents of the stabilized soil samples
decrease with addition of cement, fly ash and
phosphogypsum. UCS of untreated soils was in all
cases lower than that for treated soils. The cement
content has a significantly higher influence than the
fly ash content.
a) Sp and SP
a) Sp and SP both decreased.
b) PI, compaction. Ps, Sp,
consolidation
b) Increasing the amount of shredded waste tires will
increase the shear strength and decreased, PI,
MDD,K, Sp and SP and Cc
a) Sp and SP
a) Sp and SP both decreased.
b) PI, compaction. Ps, Sp,
consolidation
b) Increasing the amount of shredded waste tires will
increase the shear strength and decreased ,PI,
MDD,K, Sp and Ps and Cc
Reference
Seda et al. (2007)
Attom et al. (2007)
48.
Wood ash
PI, CBR
PI was reduced and CBR and strength increased by 23–
50% and 49–67%, respectively, depending on the comp
active energy used. The highest CBR and strength values
were achieved at 10% wood ash. Curing improved the
strength of the wood ash-treated clay.
Okagbue(2007)
49.
Cement kiln dusts
PI, Compaction, UCS
Decreased the PI, increased the UCS and the stiffness
Peethamparan
et al.(2008)
50.
41
Granulated Blast Furnace
Slag (GBFS), GBFS -Cement
Grain size distribution, Decreased the amount of swell while increasing the rate
Atterberg’s limits, Swelling of swell. Curing samples for 7 and 28 days resulted in less
Cokca et al. (2008)
SL.No
Types of waste
(GBFSC)
42
Investigation
Findings
percentage and Rate of swell percentages and higher rate of swell
swell. Effect of curing on
swelling percentage and
rate of swell, Leachate
analysis
Reference
2.1.7 Alkali activated Fly Ash:
Under replacement of 30% and 60% cement by gypsum activated class F fly ash (addition of
gypsum is 3% and 6% respectively); strength is gradually increased which is comparable
with no activated fly ash- cement paste (Aimin and Sarkar 1991). Compressive strength is
directly related to NaOH concentration and curing temperature i.e. fly ash activated by 4M
NaOH concentration has maximum compressive strength that cured under 90°C temperature
(Katz 1998) and it is concluded that activation of fly ash in blended cement depends on - i)
pH of activating material, ii) ratio between activator and fly ash. By author (Fan et al. 1999)
AFA behaves as setting as well as hardening accelerator and its pozzolanic reactivity is
higher than that of FA in both earlier and longer hydration periods. It is concluded that
strength becomes higher at 1 day by adding 5 to 10 % of AFA in cement paste which is
continue the same level for 3 days and 28 days of testing. Mechanical strength is affected by
temperature of curing and type of activator used. But for class F fly ash that activated by
combination of sodium hydroxide and sodium silicate has highest compressive strength at
85°C temperature of curing that maintain for 2hr duration (Palomo et al. 1999). Again
author invented that alkali activated fly ash is smooth, glassy, and shiny in nature having
good workability condition at very low liquid/solid ratio, but strength is much smaller for
24hr duration of curing. Strength of the fly ash/slag cement which is activated by 10M of
sodium hydroxide is higher under 25˚C temperature of curing but it becomes lower at the
longer ages of curing (Puertas et al. 2000). Strength of blended cement formed by
combination of 47% Portland cement clinker, 50% activated fly ash developed after sintering
at 1260°C of pellet of size less than 15mm size (pellet = 75% FA+ 10% LS +10% clay + 5%
coke breeze powder + water) and 3% gypsum is observed as like as 33 grade cement (Behera
et al. 2000), but it can be satisfactory as per BIS specification up to 40% replacement of that
activated fly ash having superior quality than ordinary Portland cement. Brough et al. (2001),
43
it is observed that calcium silicate hydrate (C-S-H), the binding phase normally formed by
hydrating cements but zeolites is formed during adiabatic curing up to 90°C. They found the
spacing of C-S-H phase in OPC system is 1.1 nm which is more crystalline in nature with
longer chain length and higher aluminum content. Again short term mineralogy is greatly
affected by changing the curing condition and long term mineralogy is affected by final
curing temperature. At last it is concluded that after 14 days of hydration, compressive
strength is reduced due to recrystallization of the calcium silicate hydrate or C-S-H gel or its
conversion to zeolites. Activation by sodium silicate and potassium hydroxide, kaolinite at
different ratio, it is observed that- Ca & Mg salt shorten the setting time through
heterogeneous nucleation effect but K salt retard the setting time only to the cement when the
initial solution for solid activation is low in soluble silicate concentration (Lee & Deventer
2002). C-S-H product formed by Ca/Si ratio (1.4 approx.) of fly ash-CH paste activated by
0.2 M sodium hydroxide is lower than hydrated of Portland cement (William et al. 2002) but
rate of hydration is directly depend on the content of CH-fly ash in the mixture. That
activated fly ash possess the mineral phase of calcium bearing complex silicate containing
quartz as major and mullite as minor phase (Behera et al. 2002). By same author it is
concluded that strength and deformation characteristics of sintered fly ash aggregate concrete
is similar to concrete with natural granite aggregate (Behera et al. 2004). Compressive
strength of alkali activated fly ash cement paste (i.e. 10% cement + 10% NaOH + 15%
sodium silicate + 5% MnO2 + 60% fly ash) is higher i.e. 33.9 MPa which is cured at room
temperature after 24hr of moisture curing at 50˚C and compressive strength of concrete using
alkali activated fly ash light weight aggregate is 26.47MPa (Jo et al. 2007). Calcium is the
major source of expansive nature that formed during gel formation created by alkali-silica
reaction and this expansion is less than ordinary Portland cement (Lodeiro et al. 2007).
Activated fly ash has better mechanical strength due to formation of amorphous sodium
44
aluminosilicate gel and that zeolite formation is directly related to curing age under the
temperature 85°C (Criado et al. 2007). Mechanical activation fly ash has capable to enhanced
blended cement, extensively variation of geopolymer products like high strength geopolymer
cements (i.e. Up to 120 MPa), self-glazed geopolymer tiles, geopolymer pavement tile
(Kumar et al. 2007).
Amorphous gel formation is observed from primary reaction of alkali activated fly ash whose
Si/Al ratio depends on curing time and nature of alkaline activator (Criado et al. 2008).
However they invented that structure, composition, kinetics of that amorphous gel is caused
due to silica which is stable initially by cyclic silicate trimmers which retard the latter
reaction of fly ash. Two supplementary materials i.e. Zeolite gives highest strength with best
sulfate resistance and bentonite behaves as filler creating more compact structure in alkali
activated fly ash (Mingyu et al. 2009). High mechanical strength with low permeability,
porosity and water demand is observed in alkali activated fly ash binders by using modified
nanosilica as activator (Rodriguez et al. 2013). Mortar formed by fly ash and slag that
activated with combination of sodium hydroxide pellet and sodium silicate solution has
highest compressive strength and flexural strength than OPC mortar with lower water
absorption (Chi & Huang 2013). Pore structure of alkali activated fly ash is lower with
increase of curing time and it is caused due to increase the amount of silica and alkali content,
but it can be develop with extending the curing time and temperature (Ma et al. 2013). Also
author invented that water permeability of activated fly ash is higher at later ages but that
become lower with progress of curing time, temperature, and higher content of silica at later
ages.
45
Chapter -3
Materials and Methodology
46
3.1 Materials
3.1.1 Expansive Soil:In the present investigation, expansive black cotton soil was procured from a site having
coordinates as N 21° 12‟ 34.03” and S 79° 09‟ 29.09”, Khairi, Kanli road, Nagpur,
Maharashtra. The black cotton soil was collected by method of disturbed sampling after
removing the top soil at 500 mm depth and transported in sacks to the laboratory. Little
amount of the sample was sealed in polythene bag for determining its natural moisture
content. The soil was air dried, pulverized and sieved with 4.75 mm Indian as required for
laboratory test. The various geotechnical properties are shown in Table 3.1
Table 3.1 Geotechnical Properties of Expansive soil
SL.NO
PROPERTIES
CONFIRMING TO IS CODE
VALUE
1
Coefficient of uniformity (Cu)
IS 2720 : Part 4 : 1985
2.43
2
Coefficient of curvature (Cc)
IS 2720 : Part 4 : 1985
0.51
3
Specific gravity (G)
IS 2720 : Part 3 : Sec 1 : 1980
2.64
4
Maximum dry density (MDD)
IS 2720 : Part VII : 1980
1.55 gm/cc
5
Optimum moisture content (OMC)
IS 2720 : Part VII : 1980
23.31%
6
Natural moisture content
IS 2720 : Part 2 : 1973
7.11%
7
Free swell index
IS 2720 : Part XL : 1977
100%
8
Liquid limit
IS 2720 : Part 5 : 1985
72%
9
Plastic limit
IS 2720 : Part 5 : 1985
21%
10
Swelling pressure
IS 2720 : Part XLI : 1977
6 kg/cm2
11
Classification
IS 1498
CH
47
Particle size Distribution Curve
100
Percent Finer (N)
80
60
40
20
0
1E-3
0.01
0.1
1
10
100
Particle Size (mm)
Figure 3.1 Grain size distribution curve of Soil
Standard proctor Curve
1.56
1.54
Dry density (gm/cc)
1.52
1.50
1.48
1.46
1.44
1.42
1.40
1.38
16
18
20
22
24
26
28
30
Water content (%)
Figure 3.2 Standard proctor curve
48
32
34
I - Illite
Q - Quartz
M - Magnesium Oxide
m - Montmorillonite
m
Q
120000
100000
Intensity
m
M
Q
Q
80000
60000
m
40000
Q
m
Q
M
Q Q I Q
m
m
I
m
20000
M
QM
mQ
Q
QQ
0
0
10
20
30
40
50
60
70
80
90
2 theta (Degree)
Fig 3.3 XRD analysis of Expansive soil
3.1.2 Fly ash:The fly ash is light weight coal combustion by product, which result from the combustion of
ground or powdered bituminous coal, sub-bituminous coal or lignite coal. Fly ash is generally
separated from the exhaust gases by electrostatic precipitator before the flue gases reach the
chimneys of coal-fired power plants. Generally this is together with bottom ash removed
from the bottom of the furnace is jointly known as coal ash. The fly ash is highly
heterogeneous material where particles of similar size may have different chemistry and
mineralogy. There is variation of fly ash properties from different sources, from same source
but with time and with collection point (Das and Yudhbir, 2005). Fly ash contains some unburnt carbon and its main constituents are silica, aluminium oxide and ferrous oxide. In dry
disposal system, the fly ash collected at the bottom of the mechanical dust collectors and
ESPs. From the dry storage silos also fly ashes are collected in closed wagons or moisture
49
proof bags or metallic bins, if the quality of the fly ash is good. The dry fly ash so collected is
then transported to the required locations where it is subjected to further processing before its
use in many non-geotechnical applications such as cement industry, brick manufacturing and
the like. In the present study fly ashes were collected from the captive power plant of
National Aluminium Company Ltd, Angul, Odisha. After procuring, the fly ash samples were
screened through 2 mm IS sieve, to separate out the vegetative and foreign material. To get a
clear homogeneity, the samples are mixed thoroughly and heated in an oven maintained at
105-110 0 C for 24 hours and then is stored in an air tight container, for subsequent use.
A
S
Q
140000
Q = Quartz (SiO2)
M = Mullite (Al6Si2O13)
S = Sillimanite (Al2SiO5)
120000
A = Aluminum Phosphate (AlPO4)
Intensity
100000
80000
S
A M
S S
S Q
SM
M
M
SM A
M QQ Q
60000
40000
20000
A
SS
S
MM
Q
A Q MQ
Q
0
0
10
20
30
40
50
60
70
Angle (2 Theta)
Figure 3.4 XRD analysis of fly ash
Table 3.2 Compounds present in Fly ash
50
Compounds
Composition (%)
SiO2
41.65
Al2O3
22.38
Fe2O3
15.04
MgO
4.76
CaO
4.75
80
90
K2O
5.82
Na2O
4.72
3.1.3 Activator solution
The alkaline activator solution used was a combination of sodium silicate and sodium
hydroxide. The sodium silicate was originally in powder form and is procured Loba Chemie,
Thane Maharashtra, having molecular weight of 284.20 gm/mole and specific gravity of 1.5.
While the sodium hydroxide was originally in flake form with a molecular weight of 40
gm/mole, and specific gravity of 2.13 at 20º C and 95-99% purity. The sodium hydroxide
pellets were procured from Merck specialities Pvt. Ltd. Mumbai, Maharashtra, India.
1 mole of Sodium silicate solution was prepared by adding 284.20 gm of sodium silicate
powder to 1 litre of distilled water. NaOH of different concentrations of 10, 12.5, 15 molal
were prepared before testing. The ratio of sodium silicate to sodium hydroxide solution by
mass was kept as 2. This value was chosen not only because the silicate is considerably
cheaper than the hydroxide, but also because several studies that have analysed the influence
of the activator composition concluded that higher ratios resulted in higher strength levels.
3.2 Methodology Adopted:To evaluate the effect of the ash/soil ratio (by dry mass) on mechanical strength, three
different fly ash percentages, regarding the total solids (soil + ash) weight, were used: 20, 30
and 40 %, corresponding to ash/soil ratios of 0.25, 0.43 and 0.67, with activator/total solids
ratios of 0.15, 0.2 and 0.25. The details of the experimental specimens are shown in Table 3.3
The soil and the ash were previously homogenised before the activator was added to the
mixture. After mixing for 3 min, the samples were cast into 50-mm moulds by tapping the
moulds on the lab counter, which were then left in a sealed container. Since the behaviour of
51
the mixtures was that of a viscous fluid, no density control was used during the preparation of
the samples. However, when removed from the moulds, every sample was weighted, and an
average unit weight of 20 kN/m3 was obtained, regardless of the fly ash percentage in the
mixture. The 15 molal mixtures showed a very high viscosity which made the preparation
and handling process more difficult than with the remaining concentrations, to a point where
this factor should be considered when designing future studies and/or applications. This
effect is related to the SiO2 : Na2O mass ratio of the silicate + hydroxide solution which, for
the 15 molal activator, is approximately 1, making the metasilicate solution very unstable and
favouring crystallisation. This SiO2 : Na2O mass ratio was, in the original silicate solution,
approximately 2, but the addition of the hydroxide solution reduced it significantly, especially
in the 15 molal mixtures. After 48 h, the samples were removed from the moulds and
wrapped in cling film and left at ambient temperature and humidity conditions (50–60 % RH
and 32-35º C). Immediately before testing, at the ages of 3, 7 and 28 days, the samples were
trimmed to 100 mm long and tested for unconfined compressive strength (UCS) on an Aimil
hydraulic testing machine. Every single result obtained was the average of 3 tested samples.
The details of the alkaline activator mixed soil specimens are shown in Table 3.3
Figure 3.5 Photographic image of Samples wrapped in cling film.
52
Sl No
Name of the specimen
Particular of the mix
1
AF-100-20-15
Soil + 20% fly ash by weight of total solids + 10 molal 15% alkali activator by weight of total solids.
2
AF-100-30-15
Soil + 30% fly ash by weight of total solids + 10 molal 15% alkali activator by weight of total solids.
3
AF-100-40-15
Soil + 40% fly ash by weight of total solids + 10 molal 15% alkali activator by weight of total solids.
4
AF-100-20-20
Soil + 20% fly ash by weight of total solids + 10 molal 20% alkali activator by weight of total solids.
5
AF-100-30-20
Soil + 20% fly ash by weight of total solids + 10 molal 20% alkali activator by weight of total solids.
6
AF-100-40-20
Soil + 20% fly ash by weight of total solids + 10 molal 20% alkali activator by weight of total solids.
7
AF-100-20-25
Soil + 20% fly ash by weight of total solids + 10 molal 25% alkali activator by weight of total solids.
8
AF-100-30-25
Soil + 20% fly ash by weight of total solids + 10 molal 25% alkali activator by weight of total solids.
9
AF-100-40-25
Soil + 20% fly ash by weight of total solids + 10 molal 25% alkali activator by weight of total solids.
10
AF-125-20-15
Soil + 20% fly ash by weight of total solids + 12.5 molal 15% alkali activator by weight of total solids.
11
AF-125-30-15
Soil + 30% fly ash by weight of total solids + 12.5 molal 15% alkali activator by weight of total solids.
12
AF-125-40-15
Soil + 40% fly ash by weight of total solids + 12.5 molal 15% alkali activator by weight of total solids.
13
AF-125-20-20
Soil + 20% fly ash by weight of total solids + 12.5 molal 20% alkali activator by weight of total solids.
14
AF-125-30-20
Soil + 20% fly ash by weight of total solids + 12.5 molal 20% alkali activator by weight of total solids.
15
AF-125-40-20
Soil + 20% fly ash by weight of total solids + 12.5 molal 20% alkali activator by weight of total solids.
53
16
AF-125-20-25
Soil + 20% fly ash by weight of total solids + 12.5 molal 25% alkali activator by weight of total solids.
17
AF-125-30-25
Soil + 20% fly ash by weight of total solids + 12.5 molal 25% alkali activator by weight of total solids.
18
AF-125-40-25
Soil + 20% fly ash by weight of total solids + 12.5 molal 25% alkali activator by weight of total solids.
19
AF-150-20-15
Soil + 20% fly ash by weight of total solids + 15 molal 15% alkali activator by weight of total solids.
20
AF-150-30-15
Soil + 30% fly ash by weight of total solids + 15 molal 15% alkali activator by weight of total solids.
21
AF-150-40-15
Soil + 40% fly ash by weight of total solids + 15 molal 15% alkali activator by weight of total solids.
22
AF-150-20-20
Soil + 20% fly ash by weight of total solids + 15 molal 20% alkali activator by weight of total solids.
23
AF-150-30-20
Soil + 20% fly ash by weight of total solids + 15 molal 20% alkali activator by weight of total solids.
24
AF-150-40-20
Soil + 20% fly ash by weight of total solids + 15 molal 20% alkali activator by weight of total solids.
25
AF-150-20-25
Soil + 20% fly ash by weight of total solids + 15 molal 25% alkali activator by weight of total solids.
26
AF-150-30-25
Soil + 20% fly ash by weight of total solids + 15 molal 25% alkali activator by weight of total solids.
27
AF-150-40-25
Soil + 20% fly ash by weight of total solids + 15 molal 25% alkali activator by weight of total solids.
Table 3.3 Details of alkali-activated fly ash mixed soil specimens
54
For the fly ash based mixtures, water to solid of 15, 20, 25 and 30% were tested. In terms of
fly ash percentage in the mixtures, values of 20, 30 and 40 % of the total dry weight were
used. These values are used so as to have a direct comparison with the activated ash could be
established. The details of the mix prepared is as shown in Table 3.4
55
Sl No
Name of the specimen
Particular of the mix
1
F-15-20
Soil + 20% fly ash by weight of total solids + 15% water by weight of total solids.
2
F-15-30
Soil + 20% fly ash by weight of total solids + 15% water by weight of total solids.
3
F-15-40
Soil + 20% fly ash by weight of total solids + 15% water by weight of total solids.
4
F-20-20
Soil + 20% fly ash by weight of total solids + 20% water by weight of total solids.
5
F-20-30
Soil + 20% fly ash by weight of total solids + 20% water by weight of total solids.
6
F-20-40
Soil + 20% fly ash by weight of total solids + 20% water by weight of total solids.
7
F-25-20
Soil + 20% fly ash by weight of total solids + 25% water by weight of total solids.
8
F-25-30
Soil + 20% fly ash by weight of total solids + 25% water by weight of total solids.
9
F-25-40
Soil + 20% fly ash by weight of total solids + 25% water by weight of total solids.
Table 3.4 Details of fly ash mixed soil specimens
56
The rheological studies include measurement of density and viscosity of both cement and
alkali-activated grouts and comparison between the two, with the purpose of determining
how much time is available before mixing with the soil. For this Marsh funnel viscometer
confirming to IS 14343:1996 was used to calculate the viscosity of both the grouts. By using
this viscometer we can measure the time taken for a known volume of liquid to flow from the
base to the bottom end of the inverted funnel. The liquid was poured through the top,
saturating the voids in the sand until it reached the top level, which used approximately 1.5
litres. The bottom exit was then released and the liquid flowed into a measuring container,
while the time spent was recorded.
Setting time was ascertained by using Vicat‟s apparatus. Each grout was poured in the mould
in the view point of calculating its initial and final setting time.
Figure 3.6 Experimental Setup of Marsh Funnel Viscometer
57
Chapter -4
Results on stabilization of
expansive soils with fly ash
58
4.1 Introduction:
This chapter presents the results of stabilization of expansive black cotton soil, with fly ash.
The increase in strength criteria is ascertained by conducting unconfined compression test on
samples, at 3, 7 and 28 days curing. The samples, casted were of 50 mm diameter and 100
mm height, thereby ensuring L/D ratio as 2. These samples contains fly ash in 20, 30 and
40% by weight of dry mass and water to total solid ratio is varied from 15, 20 and 25%. All
the samples were covered with cling film, after casting and are kept in a air tight container for
48 hours. After 48 h, the samples were removed from the moulds and wrapped in cling film
and left at ambient temperature and humidity conditions (50–60 % RH and 32-35º C).
Immediately before testing, at the ages of 3, 7 and 28 days, the samples were trimmed to 100
mm long and tested for unconfined compressive strength (UCS) on an Aimil hydraulic testing
machine at constant strain rate of 1.2 mm/min. Every single result obtained was the average
of 3 tested samples.
Figure 4.1 Photographic image showing test setup of UCS
59
4.2 Results
Following are the test results obtained:Table 4.1 UCS results of F-15-20, F-15-30, F-15-40
Curing Time
Unconfined compressive strength (kPa)
(Days)
Specimen
F-15-20
F-15-30
F-15-40
3
104.97
98.58
82.6
7
283.22
219.64
144.68
28
363.65
279.93
254.9
Name
Unconfined compressive strength (Kpa)
400
F-15-20
F-15-30
F-15-40
350
300
250
200
150
100
50
0
5
10
15
20
25
30
Curing time (Days)
Figure 4.2 UCS results of F-15-20, F-15-30, F-15-40
It is evident from the Table 4.1, that the mix F-15-20, is giving more strength at 3, 7 and 28
days than the other two. The 3 day strength of F-15-20 is 6 % more than that of F-15-30 and
27 % more than that of F-15-40. Similarly the 7 day strength of F-15-20 is 29% more than
that of F-15-30 and is about 96% more than that of F-15-40. Moreover the 28 day strength of
60
mix F -15-20 is nearly 30% more than that of F-15-30 and is 43 % more than that of F-15-40.
The variations of strength of the mixes are shown in Figure 4.2. and it can be stated as the
strength of the mix is directly proportional to the curing period and is inversely proportional
to the fly ash content in the mix. Thus it can be concluded that for a constant water to total
solid ratio, the strength increases with the curing period and also with the decreased fly ash
content.
Table 4.2 UCS results of F-20-20, F-20-30, F-20-40
Curing Time
Unconfined compressive strength (kPa)
(Days)
Specimen
F-20-20
F-20-30
F-20-40
3
85.69
120.5
91.7
7
113.98
131.5
101.77
28
141.93
156.25
125.94
Name
Unconfined compressive strength (Kpa)
160
F-20-20
F-20-30
F-20-40
150
140
130
120
110
100
90
80
0
5
10
15
20
25
Curing time (Days)
Figure 4.3 UCS results of F-20-20, F-20-30, F-20-40
61
30
Table 4.2 shows the UCS values of the samples F-20-20, F-20-30, F-20-40, obtained after 3,
7 and 28 days curing. It is evidient from the results depicted in table 4.2 that the mix F-20-30
is giving more strength at 3, 7 and 28 days than the other two. The 3 day strength of F-20-30
is 40 % more than that of F-20-20 and is 31.4 % more than that of F-20-40. Similarly the 7
day strength of F-20-30 is 15.37% more than that of F-20-20 and is about 29.21% more than
that of F-20-40. Moreover there is a slight increase in the 28 day strength of mix F-20-30
which is about 10% more than that of F-20-20 and is 24 % more than that of F-20-40. The
variations of strength of the mixes are shown in Figure 4.3.
Table 4.3 UCS results of F-25-20, F-25-30, F-25-40
Curing Time
Unconfined compressive strength (kPa)
(Days)
Specimen
F-25-20
F-25-30
F-25-40
3
45.13
41.91
38.38
7
52.69
49.88
47.28
28
115.69
98.63
88.27
Name
It is evident from the Table 4.3, that the mix F-25-20, is giving more strength at 3, 7 and 28
days than the other two. There is a slight variation in the 3, 7 and 28 day strength of F-25-20
and F-25-30 which is about 7%, 5% and 17%, but the variation between the 3, 7 and 28 day
strength of F-25-20 and F-25-40 is about 18%, 11 % and 31%. The variations of strength of
the mixes are shown in Figure 4.4, and it can be stated as the strength of the mix is directly
proportional to the curing period and is inversely proportional to the fly ash content in the
62
mix. Thus it can be concluded that for a constant water to total solid ratio, the strength
increases with the curing period and also with the decreased fly ash content.
F-25-20
F-25-30
F-25-40
Unconfined compressive strength (Kpa)
120
110
100
90
80
70
60
50
40
30
0
5
10
15
20
25
30
Curing time (Days)
Figure 4.4 UCS results of F-25-20, F-25-30, F-25-40
Table 4.4 UCS results of all Fly ash Samples
Curing time
Unconfined compressive strength
(Days)
(kPa)
F-15-20 F-15-30 F-15-40 F-20-20 F-20-30 F-20-40 F-25-20 F-25-30 F-25-40
3
104.97
98.58
82.6
85.69
120.5
91.7
45.13
41.91
38.38
7
283.22
219.64
144.68
113.98
131.5
101.77
52.69
49.88
47.28
28
363.65
279.93
254.9
141.93
156.25
125.94
115.69
98.63
88.27
63
Unconfined compressive strength (Kpa)
400
350
300
250
F-15-20
F-15-30
F-15-40
F-20-20
F-20-30
F-20-40
F-25-20
F-25-30
F-25-40
200
150
100
50
0
5
10
15
20
25
30
Curing time (Days)
Figure 4.5 UCS results of all Fly ash Samples
10
F-15-20
F-15-30
F-15-40
F-20-20
F-20-30
F-20-40
F-25-20
F-25-30
F-25-40
Unconfined compressive
Y Axis Titlestrength (kPa)
120
8
100
80
6
60
4
40
2
20
0
0
2
4
3
6
8
10
Curing time = 3 Days
Figure 4.6 Bar chart showing the UCS results of Fly ash Samples after 3 days of curing
64
F-15-20
F-15-30
F-15-40
F-20-20
F-20-30
F-20-40
F-25-20
F-25-30
F-25-40
Unconfined compressive strength (kPa)
300
250
200
150
100
50
0
7
Curing time = 7 Days
Unconfined compressive strength (kPa)
Figure 4.7 Bar chart showing the UCS results of Fly ash Samples after 7 days of curing
350
300
250
F-15-20
F-15-30
F-15-40
F-20-20
F-20-30
F-20-40
F-25-20
F-25-30
F-25-40
200
150
100
50
0
28
Curing Time = 28 Days
Figure 4.8 Bar chart showing the UCS results of Fly ash Samples after 28 days of curing
Table 4.4 shows the UCS values of all samples treated with fly ash, obtained after 3, 7 and 28
days curing. It is evident from the results depicted in table 4.4 that the mix F-20-30 is giving
more 3 day strength as compared to other mixes. But the mix F-15-20 is giving more strength
65
at 7 day and 28 day curing as compared to others. Strength of the mix F-25-40 obtained after
3, 7 and 28 days curing is the least among all others. The 3 day strength of F-20-30 is near
about 2.2 times more than that of F-25-40. Similarly the strength obtained after 7 day and 28
day curing of the mix F-15-20 is about 5 times and 3 times more than that obtained from mix
F-25-40. The variations of strength of the mix obtained with the days of curing are shown in
a bar chart graph in figure 4.6, 4.7 and 4.8.
66
Chapter -5
Results on stabilization of
expansive soils with activated
fly ash
67
5.1 Introduction:
This chapter presents the results of stabilization of expansive black cotton soil, with alkliactivated fly ash. The increase in strength criteria is ascertained by conducting unconfined
compression test on samples, at 3, 7 and 28 days curing. The samples, casted were of 50 mm
diameter and 100 mm height, thereby ensuring L/D ratio as 2. These samples contains fly ash
in 20, 30 and 40% by weight of dry mass and activator to total solid ratio is varied from 15,
20 and 25%. All the samples were covered with cling film, after casting and are kept in a air
tight container for 48 hours. After 48 h, the samples were removed from the moulds and
wrapped in cling film and left at ambient temperature and humidity conditions (50–60 % RH
and 32-35º C). Immediately before testing, at the ages of 3, 7 and 28 days, the samples were
trimmed to 100 mm long and tested for unconfined compressive strength (UCS) on an Aimil
hydraulic testing machine at constant strain rate of 1.2 mm/min. Every single result obtained
was the average of 3 tested samples.
5.2 Results
Table 5.1 UCS results of AF-100-20-15, AF-100-30-15, AF-100-40-15
Curing time
Unconfined compressive strength
(Days)
68
(kPa)
AF-100-20-15
AF-100-30-15
AF-100-40-15
3
195.46
175.95
140.51
7
253.32
179.24
131.41
28
436.63
195.23
128.9
Unconfined compressive strength (Kpa)
500
AF-100-20-15
AF-100-30-15
AF-100-40-15
450
400
350
300
250
200
150
100
0
5
10
15
20
25
30
Curing time (Days)
Figure 5.1 UCS results of AF-100-20-15, AF-100-30-15, AF-100-40-15
It is evident from the Table 5.1, that the mix AF-100-20-15, is giving more strength at 3, 7
and 28 days than the other two. The 3 day strength of AF-100-20-15 is 11 % more than that
of AF-100-30-15 and 39 % more than that of AF-100-40-15. Similarly the 7 day strength of
AF-100-20-15 is 41% more than that of AF-100-30-15 and is about 92 % more than that of
AF-100-40-15. Moreover the 28 day strength of mix AF-100-20-15 is nearly 2.23 times than
that of AF-100-30-15 and is 3.38 times more than that of AF-100-40-15. The variations of
strength of the mixes are shown in Figure 5.1. and it can be stated as the strength of the mix is
directly proportional to the curing period and is inversely proportional to the fly ash content
in the mix. Thus it can be concluded that for a constant activator to total solid ratio, the
strength increases with the curing period and also with the decreased fly ash content.
69
Table 5.2 UCS results of AF-100-20-20, AF-100-30-20, AF-100-40-20
Curing time
Unconfined compressive strength
Unconfined compressive strength (Kpa)
(Days)
(kPa)
AF-100-20-20
AF-100-30-20
AF-100-40-20
3
311.58
392.7
322.8
7
350.83
462.64
546.88
28
407.7
580.62
810.02
AF-100-20-20
AF-100-30-20
AF-100-40-20
800
700
600
500
400
300
0
5
10
15
20
25
30
Curing time (Days)
Figure 5.2 UCS results of AF-100-20-20, AF-100-30-20, AF-100-40-20
Table 5.2 shows the UCS values of the samples AF-100-20-20, AF-100-30-20, AF-100-4020, obtained after 3, 7 and 28 days curing. It is evident from the results depicted in table 5.2
that the mix AF-100-30-20 is giving more strength after 3 days curing than the other two,
while the strength after 7 and 28 days curing is more in case of mix AF-100-40-20. This can
be probably related to necessary time period required for the nucleation phase to occur,
during which the products resulting from the dissolution of the raw silica and alumina
accumulate before precipitation. The variations of strength of the mixes are shown in Figure
5.2.
70
Table 5.3 UCS results of AF-100-20-25, AF-100-30-25, AF-100-40-25
Curing time
Unconfined compressive strength
(Days)
(kPa)
AF-100-20-25
AF-100-30-25
AF-100-40-25
3
103.97
94.71
85.42
7
130.13
146.92
112.03
28
238.77
215.77
232.77
Table 5.3 shows the UCS values of the samples AF-100-20-25, AF-100-30-25, AF-100-4025, obtained after 3, 7 and 28 days curing. It is evident from the results depicted in table 5.3
that the mix AF-100-20-25 is giving more strength after 3 days and 28 days curing than the
other two, while the strength after 7 days curing is more in case of mix AF-100-30-25 The
variations of strength of the mixes are shown in Figure 5.3.
AF-100-20-25
AF-100-30-25
AF-100-40-25
Unconfined compressive strength (Kpa)
240
220
200
180
160
140
120
100
80
0
5
10
15
20
25
30
Curing time (Days)
Figure 5.3 UCS results of AF-100-20-25, AF-100-30-25, AF-100-40-25
71
Table 5.4 UCS results of AF-125-20-15, AF-125-30-15, AF-125-40-15
Curing time
Unconfined compressive strength
(Days)
(kPa)
AF-125-20-15
AF-125-30-15
AF-125-40-15
3
114.59
158.87
187.08
7
220.1
152.8
250.27
28
364.32
221.54
399.24
AF-125-20-15
AF-125-30-15
AF-125-40-15
Unconfined compressive strength (Kpa)
400
350
300
250
200
150
100
0
5
10
15
20
25
30
Curing time (Days)
Figure 5.4 UCS results of AF-125-20-15, AF-125-30-15, AF-125-40-15
Table 5.4 shows the UCS values of the mixes, casted from 12.5 molal activator solution.
From the table it is evident that the mix AF-125-40-15 is giving more strength than that of
others, obtained after 3, 7 and 28 days curing. The variations of strength of the mixes are
shown in Figure 5.4
72
Table 5.5 UCS results of AF-125-20-20, AF-125-30-20, AF-125-40-20
Curing time
Unconfined compressive strength
(Days)
(kPa)
AF-125-30-20
AF-125-40-20
3
307.85
196.93
287.42
7
230.35
293.98
419.2
28
548.78
590.78
977.09
Unconfined compressive strength (Kpa)
AF-125-20-20
1050
1000
950
900
850
800
750
700
650
600
550
500
450
400
350
300
250
200
150
AF-125-20-20
AF-125-30-20
AF-125-40-20
0
5
10
15
20
25
30
Curing time (Days)
Figure 5.5. UCS results of AF-125-20-20, AF-125-30-20, AF-125-40-20
Similarly, Table 5.5 shows the UCS values of the mixes AF-125-20-20, AF-125-30-20, AF125-40-20, casted from 15 molal activator solution. From the table it is evident that the mix
AF-125-20-20 is giving more strength than that of others, obtained after 3days of curing,
73
while mix AF-125-40-20, is giving more strength than the other two at 7 and 28 days curing.
The variations of strength of the mixes are shown in Figure 5.5.
Table 5.6 UCS results of AF-125-20-25, AF-125-30-25, AF-125-40-25
Curing time
Unconfined compressive strength
(Days)
(kPa)
AF-125-30-25
AF-125-40-25
3
128.77
114.93
113.76
7
154.83
179.89
192.29
28
317.55
555.47
852.17
Unconfined compressive strength (Kpa)
AF-125-20-25
900
850
800
750
700
650
600
550
500
450
400
350
300
250
200
150
100
50
AF-125-20-25
AF-125-30-25
AF-125-40-25
0
5
10
15
20
25
30
Curing time (Days)
Figure 5.6 UCS results of AF-125-20-25, AF-125-30-25, AF-125-40-25
It is evident from the Table 5.6 that the 3 days strength of the mix AF-125-20-25, is more
than the rest, while in case of 7 and 28 days strength the mix AF-125-40-25 is giving better
results than the rest. The variations of strength of the mixes are shown in Figure 5.6.
74
Table 5.7 UCS results AF-150-20-15, AF-150-30-15, AF-150-40-15
Curing time
Unconfined compressive strength
(Days)
(kPa)
AF-150-20-15
AF-150-30-15
AF-150-40-15
3
288.17
247.41
160.75
7
339.7
428.28
503.98
28
579.28
603.32
643.86
Unconfined compressive strength (Kpa)
700
AF-150-20-15
AF-150-30-15
AF-150-40-15
650
600
550
500
450
400
350
300
250
200
150
100
0
5
10
15
20
25
30
Curing time (Days)
Figure 5.7 UCS results of AF-150-20-15, AF-150-30-15, AF-150-40-15
Table 5.7 shows the UCS values of the mixes, casted from 15 molal activator solution. From
the Table 5.7, it can be concluded that the 3 days UCS is more in case of mix AF-150-20-15,
whose magnitude is about 79 % more than that of mix AF-150-40-15. But in case of strength
75
obtained after 7 and 28 days curing, AF-150-40-15 outperforms all. The variations of strength
of the mixes obtained as are shown in Figure 5.7.
Table 5.7 UCS results AF-150-20-20, AF-150-30-20, AF-150-40-20
Curing time
Unconfined compressive strength
(Days)
(kPa)
AF-150-20-20
AF-150-30-20
AF-150-40-20
3
207.72
239.99
171.61
7
361.06
450.03
503.98
28
396.93
715.4
643.86
Similarly, Table 5.7 shows the UCS values of the mixes AF-150-20-20, AF-150-30-20, AF150-40-20, casted from 15 molal activator solutions. From the table it is evident that the mix
AF-150-30-20 outperforms all in the aspect of gaining more strength at 3, 7 and 28 days of
curing. The variations of strength of the mixes are shown in Figure 5.7.
76
AF-150-20-20
AF-150-30-20
AF-150-40-20
Unconfined compressive strength (Kpa)
750
700
650
600
550
500
450
400
350
300
250
200
150
0
5
10
15
20
25
30
Curing time (Days)
Figure 5.7 UCS results AF-150-20-20, AF-150-30-20, AF-150-40-20
Table 5.8. UCS results AF-150-20-25, AF-150-30-25, AF-150-40-25
Curing time
Unconfined compressive strength
(Days)
77
(kPa)
AF-150-20-25
AF-150-30-25
AF-150-40-25
3
111.24
98.43
75.63
7
138.52
181.89
256.55
28
182.15
465.24
296
Unconfined compressive strength (Kpa)
500
AF-150-20-25
AF-150-30-25
AF-150-40-25
450
400
350
300
250
200
150
100
50
0
5
10
15
20
25
30
Curing time (Days)
Figure 5.8. UCS results AF-150-20-25, AF-150-30-25, AF-150-40-25
Similarly, Table 5.8 shows the UCS values of the mixes AF-150-20-20, AF-150-30-20, AF150-40-20, after 3, 7 and 28 days of curing. From the table it is evident that the mix AF-15020-25 is giving more strength after 3 days of curing as compared to others, mix AF-150-4025 is giving more strength after 7 days of curing as compared to mix AF-150-20-25 and mix
AF-150-30-25. In case of 28 days strength mix AF-150-30-25, outperforms all.
variations of strength of the mixes are shown in Figure 5.8.
78
The
850
AF-100-20-15
AF-100-30-15
AF-100-40-15
AF-100-20-20
AF-100-30-20
AF-100-40-20
AF-100-20-25
AF-100-30-25
AF-100-40-25
Unconfined compressive strength (Kpa)
800
750
700
650
600
550
500
450
400
350
300
250
200
150
100
50
0
5
10
15
20
25
30
Curing time (Days)
Figure 5.9. UCS results of all 10 molal sample
Table 5.9 shows the variation of strength obtained for 10 molal activator content and 20, 30
and 40% fly ash content mixed soil samples, after 3, 7 and 28 days curing periods.
The
variations are also shown in Figure 5.9. Figure 5.10, 5.11 and 5.12 shows the gain in strength
of all 10 molal mixes after 3, 7 and 28 days respectively in bar graph form. From the tables
and graphs it is evident that the 3 days strength is more in case of mix AF-100-30-20, while
the 7 & and 28 days strength is more in case of mix AF-100-40-20. The least 3 and 7 days
strength is exhibited by mix AF-100-40-25, while mix AF-100-30-25 exhibit least 28 days
strength.
79
Table 5.9. UCS results of all 10 molal sample
Curing time
(Days)
3
7
28
AF-100-20-15
195.46
253.32
436.63
AF-100-30-15
175.95
179.24
195.23
AF-100-40-15
140.51
131.41
128.9
Unconfined compressive strength
(kPa)
AF-100-20-20 AF-100-30-20 AF-100-40-20
311.58
392.7
322.8
350.83
462.64
546.88
407.7
580.62
810.02
AF-100-20-25
103.97
130.13
238.77
AF-100-30-25
94.71
146.92
215.77
AF-100-40-25
85.42
112.03
232.77
Table 5.10. UCS results of all 12.5 molal sample
Curing time
(Days)
Unconfined compressive strength
(kPa)
AF-125-20-15
AF-125-30-15
AF-125-40-15
AF-125-20-20
AF-125-30-20
AF-125-40-20
AF-125-20-25
AF-125-30-25
AF-125-40-25
3
114.59
158.87
187.08
307.85
196.93
287.42
128.77
114.93
113.76
7
220.1
152.8
250.27
230.25
293.98
419.2
154.83
179.89
192.29
28
364.32
221.54
399.24
548.78
590.78
977.09
317.55
555.47
852.17
Table 5.11. UCS results of all 15 molal sample
Curing time
(Days)
3
7
28
80
Unconfined compressive strength
(kPa)
AF-150-20-15
AF-150-30-15
AF-150-40-15
AF-150-20-20
AF-150-30-20
AF-150-40-20
AF-150-20-25
AF-150-30-25
AF-150-40-25
288.17
339.7
579.28
247.41
428.28
603.32
160.75
503.98
643.86
207.72
361.06
396.93
239.99
450.03
715.4
171.61
503.98
643.86
111.24
138.52
182.15
98.43
181.89
465.24
75.63
256.65
296
AF-100-20-15
AF-100-30-15
AF-100-40-15
AF-100-20-20
AF-100-30-20
AF-100-40-20
AF-100-20-25
AF-100-30-25
AF-100-40-25
Unconfined compressive strength (kPa)
400
350
300
250
200
150
100
50
0
3
Curing Time = 3 Days
Figure 5.10. UCS results of 10 molal sample (3 Days curing)
AF-100-20-15
AF-100-30-15
AF-100-40-15
AF-100-20-20
AF-100-30-20
AF-100-40-20
AF-100-20-25
AF-100-30-25
AF-100-40-25
Unconfined compressive strength (kPa)
550
500
450
400
350
300
250
200
150
100
50
0
7
Curing Time = 7 Days
Unconfined compressive strength (kPa)
Figure 5.11. UCS results of 10 molal sample (7 Days curing)
AF-100-20-15
AF-100-30-15
AF-100-40-15
AF-100-20-20
AF-100-30-20
AF-100-40-20
AF-100-20-25
AF-100-30-25
AF-100-40-25
800
700
600
500
400
300
200
100
0
28
Curing Time = 28 Days
Figure 5.12. UCS results of 10 molal sample (28 days curing)
81
Unconfined compressive strength (Kpa)
1050
1000
950
900
850
800
750
700
650
600
550
500
450
400
350
300
250
200
150
100
50
AF-125-20-15
AF-125-30-15
AF-125-40-15
AF-125-20-20
AF-125-30-20
AF-125-40-20
AF-125-20-25
AF-125-30-25
AF-125-40-25
0
5
10
15
20
25
30
Curing time (Days)
Figure 5.13. UCS results of all 12.5 molal sample
Table 5.10 shows the variation of strength obtained for 12.5 molal activator content and 20,
30 and 40% fly ash content mixed soil samples, after 3, 7 and 28 days curing periods. The
variations are also shown in Figure 5.13. Figure 5.14, 5.15 and 5.16 shows the gain in
strength of all 12.5 molal mixes after 3, 7 and 28 days respectively in bar graph form. From
the tables and graphs it is evident that the 3 days strength is more in case of mix AF-125-2020, while the 7 & and 28 days strength is more in case of mix AF-125-40-20. The least 3 days
strength is exhibited by mix AF-125-40-25, while mix AF-125-30-15 exhibit least 7 days
strength and mix AF-125-40-15 exhibit least strength after 28 days curing.
82
Unconfined compressive strength (kPa)
AF-125-20-15
AF-125-30-15
AF-125-40-15
AF-125-20-20
AF-125-30-20
AF-125-40-20
AF-125-20-25
AF-125-30-25
AF-125-40-25
320
300
280
260
240
220
200
180
160
140
120
100
80
60
40
20
0
3
Curing Time = 3 Days
Figure 5.14. UCS results of 12.5 molal sample (3 Days curing)
AF-125-20-15
AF-125-30-15
AF-125-40-15
AF-125-20-20
AF-125-30-20
AF-125-40-20
AF-125-20-25
AF-125-30-25
AF-125-40-25
Unconfined compressive strength (kPa)
450
400
350
300
250
200
150
100
50
0
7
Curing Time = 7 Days
Figure 5.15. UCS results of 12.5 molal sample (7 Days curing)
Unconfined compressive strength (kPa)
1000
800
AF-125-20-15
AF-125-30-15
AF-125-40-15
AF-125-20-20
AF-125-30-20
AF-125-40-20
AF-125-20-25
AF-125-30-25
AF-125-40-25
600
400
200
0
28
Curing Time = 28 Days
Figure 5.16. UCS results of 12.5 molal sample (28 Days curing)
83
Unconfined compressive strength (Kpa)
750
700
650
600
550
500
450
400
350
AF-150-20-15
AF-150-30-15
AF-150-40-15
AF-150-20-20
AF-150-30-20
AF-150-40-20
AF-150-20-25
AF-150-30-25
AF-150-40-25
300
250
200
150
100
50
0
5
10
15
20
25
30
Curing time (Days)
Figure 5.17 UCS results of all 15 molal Samples
AF-150-20-15
AF-150-30-15
AF-150-40-15
AF-150-20-20
AF-150-30-20
AF-150-40-20
AF-150-20-25
AF-150-30-25
AF-150-40-25
Unconfined compressive strength (kPa)
300
250
200
150
100
50
0
3
Curing Time = 3 Days
Figure 5.18. UCS results of 15 molal sample (3 Days curing)
84
AF-150-20-15
AF-150-30-15
AF-150-40-15
AF-150-20-20
AF-150-30-20
AF-150-40-20
AF-150-20-25
AF-150-30-25
AF-150-40-25
Unconfined compressive strength (kPa)
500
450
400
350
300
250
200
150
100
50
0
7
Curing Time = 7 Days
Unconfined compressive strength (kPa)
Figure 5.19. UCS results of 15 molal sample (7 Days curing)
AF-150-20-15
AF-150-30-15
AF-150-40-15
AF-150-20-20
AF-150-30-20
AF-150-40-20
AF-150-20-25
AF-150-30-25
AF-150-40-25
700
600
500
400
300
200
100
0
28
Curing Time = 28 Days
Figure 5.20. UCS results of 15 molal sample (28 Days curing).
85
Table 5.12 UCS results of all AAFA Samples
Name
Qu (kPa)
Name
Qu (kPa)
Name
Qu (kPa)
AF-100-20-15-3D
195.46
AF-100-20-15-7D
253.32
AF-100-20-15-28D
436.63
AF-100-30-15-3D
175.95
AF-100-30-15-7D
179.24
AF-100-30-15-28D
195.23
AF-100-40-15-3D
140.51
AF-100-40-15-7D
131.41
AF-100-40-15-28D
128.9
AF-100-20-20-3D
311.58
AF-100-20-20-7D
350.83
AF-100-20-20-28D
407.7
AF-100-30-20-3D
392.7
AF-100-30-20-7D
462.64
AF-100-30-20-28D
580.62
AF-100-40-20-3D
322.8
AF-100-40-20-7D
546.88
AF-100-40-20-28D
810.02
AF-100-20-25-3D
103.97
AF-100-20-25-7D
130.13
AF-100-20-25-28D
238.77
AF-100-30-25-3D
94.71
AF-100-30-25-7D
146.92
AF-100-30-25-28D
215.77
AF-100-40-25-3D
85.42
AF-100-40-25-7D
112.03
AF-100-40-25-28D
232.77
AF-125-20-15-3D
114.59
AF-125-20-15-7D
220.1
AF-125-20-15-28D
364.32
AF-125-30-15-3D
158.87
AF-125-30-15-7D
152.8
AF-125-30-15-28D
221.54
AF-125-40-15-3D
187.08
AF-125-40-15-7D
250.27
AF-125-40-15-28D
399.24
AF-125-20-20-3D
307.85
AF-125-20-20-7D
230.25
AF-125-20-20-28D
548.78
AF-125-30-20-3D
196.93
AF-125-30-20-7D
293.98
AF-125-30-20-28D
590.78
AF-125-40-20-3D
287.42
AF-125-40-20-7D
419.2
AF-125-40-20-28D
977.09
AF-125-20-25-3D
128.77
AF-125-20-25-7D
154.83
AF-125-20-25-28D
317.55
AF-125-30-25-3D
114.93
AF-125-30-25-7D
179.89
AF-125-30-25-28D
555.47
AF-125-40-25-3D
113.76
AF-125-40-25-7D
192.29
AF-125-40-25-28D
852.17
AF-150-20-15-3D
288.17
AF-150-20-15-7D
339.7
AF-150-20-15-28D
579.28
AF-150-30-15-3D
247.41
AF-150-30-15-7D
428.28
AF-150-30-15-28D
603.32
AF-150-40-15-3D
160.75
AF-150-40-15-7D
503.98
AF-150-40-15-28D
643.86
AF-150-20-20-3D
207.72
AF-150-20-20-7D
361.06
AF-150-20-20-28D
396.93
AF-150-30-20-3D
239.99
AF-150-30-20-7D
450.03
AF-150-30-20-28D
715.4
AF-150-40-20-3D
171.61
AF-150-40-20-7D
503.98
AF-150-40-20-28D
643.86
AF-150-20-25-3D
111.24
AF-150-20-25-7D
138.52
AF-150-20-25-28D
182.15
AF-150-30-25-3D
98.43
AF-150-30-25-7D
181.89
AF-150-30-25-28D
465.24
AF-150-40-25-3D
75.63
AF-150-40-25-7D
256.55
AF-150-40-25-28D
296
86
The variation of strength obtained for 15 molal activator content and 20, 30 and 40% fly ash
content mixed soil samples, after 3, 7 and 28 days curing periods is shown in Table 5.11.
The variations are also shown in Figure 5.17. Figure 5.18, 5.19 and 5.20 shows the gain in
strength of all 15 molal mixes after 3, 7 and 28 days respectively in bar graph form. From the
tables and graphs it is evident that the 3 days strength is more in case of mix AF-120-20-15,
while the 7 & and 28 days strength is more in case of mix AF-150-40-15 and mix AF-15040-20. The least 3 days strength is exhibited by mix AF-150-40-25, while mix AF-125-20-25
exhibit least strength after 7 and 28 days of curing.
Table 5.12 gives the details of the activated mix casted and their corresponding strengths
attained after 3, 7 and 28 days of curing. Among all the highest strength obtained after 3 days
of curing was attained by the mix AF-150-30-20-3D, while the strength attained by mix AF150-40-20-7D after 7 days of curing is more than all others. The mix AF-150-40-20-28D
outperforms all in respect of strength attained after 28 days of curing.
87
Chapter -6
Comparison of results
88
Table 6.1 Comparison of UCS results of 15% water and activator containing samples
Curing
time
(Days)
Unconfined compressive strength
(kPa)
F-15-20
F-15-30
F-15-40
AF-100-2015
AF-100-3015
AF-100-4015
AF-125-2015
AF-125-3015
AF-125-4015
AF-150-2015
AF-150-3015
AF-150-4015
3
104.97
98.58
82.6
195.46
175.95
140.51
114.59
158.87
187.08
288.17
247.41
160.75
7
283.22
219.64
144.68
253.32
179.24
131.41
220.1
152.8
250.27
339.7
428.28
503.98
28
363.65
279.93
254.9
436.63
195.23
128.9
364.32
221.54
399.24
579.28
603.32
643.86
Table 6.2 Comparison of UCS results of 20% water and activator containing samples
Curing
time
(Days)
Unconfined compressive strength
(kPa)
F-20-40
AF-100-2020
AF-100-3020
AF-100-4020
AF-125-2020
AF-125-3020
AF-125-4020
AF-150-2020
AF-150-3020
AF-150-4020
85.69 120.5
91.7
113.98 131.5 101.77
141.93 156.25 150.94
311.58
350.83
407.7
392.7
462.64
580.62
322.8
546.88
810.02
307.85
230.25
548.78
196.93
293.98
590.78
287.42
419.2
977.09
207.72
361.06
396.93
239.99
450.03
715.4
171.61
503.98
643.86
AF-150-2025
AF-150-3025
AF-150-4025
111.24
138.52
182.15
98.43
181.89
465.24
F-20-20
3
7
28
F-20-30
Table 6.3 Comparison of UCS results of 25% water and activator containing samples
Curing
time
(Days)
F-25-20
F-2530
F-2540
AF-100-2025
AF-100-3025
3
7
28
45.13
52.69
115.69
41.91
49.88
98.63
38.38
47.28
88.27
103.97
130.13
238.77
94.71
146.92
215.77
89
Unconfined compressive strength (kPa)
AF-100-4025
85.42
112.03
232.77
AF-125-2025
AF-125-3025
128.77
154.83
317.55
114.93
179.89
555.47
AF-125-4025
113.76
192.29
852.17
75.63
256.65
296
700
Unconfined compressive strength (kPa)
650
600
550
500
450
400
F-15-20
F-15-30
F-15-40
AF-100-20-15
AF-100-30-15
AF-100-40-15
AF-125-20-15
AF-125-30-15
AF-125-40-15
AF-150-20-15
AF-150-30-15
AF-150-40-15
350
300
250
200
150
100
50
0
5
10
15
20
25
30
Curing time (Days)
Figure 6.1 Comparison of UCS results of fly ash treated and AAFA treated soil samples, containing 15%
water or activator.
The variation of strength obtained for 10, 12.5 and 15 molal activator content, 20, 30 and
40% fly ash content and containing 15% fluid by weight of dry mass (water or activator)
mixed soil samples, after 3, 7 and 28 days curing periods is shown in Table 6.1.
The
variations are also shown in Figure 6.1. Figure 6.2-6.4 shows the gain in strength of all
mixes after 3, 7 and 28 days respectively in bar graph form. From the tables and graphs it is
evident that the 3 days strength is more in case of mix AF-120-20-15, while the 7 and 28 days
strength is more in case of mix AF-150-40-15. The least 3, 7 and 28 days strength is
exhibited by mix F-15-40. The 3 days maximum strength of AAFA treated soil sample is 3.5
times higher than the minimum strength acquired by fly ash treated sample, while the 7 and
28 days maximum strength of AAFA treated soil sample are 3.5 and 2.5 times higher than the
minimum strength acquired by fly ash treated sample respectively.
90
Unconfined compressive strength (kPa)
300
280
260
240
220
200
180
160
F-15-20
F-15-30
F-15-40
AF-100-20-15
AF-100-30-15
AF-100-40-15
AF-125-20-15
AF-125-30-15
AF-125-40-15
AF-150-20-15
AF-150-30-15
AF-150-40-15
140
120
100
80
60
40
20
0
3
Curing Period = 3 Days
Figure 6.2 Comparison of UCS results of fly ash treated and AAFA treated soil samples, containing 15%
water or activator (3 Days Curing Period) .
Unconfined compressive strength (kPa)
500
450
400
350
F-15-20
F-15-30
F-15-40
AF-100-20-15
AF-100-30-15
AF-100-40-15
AF-125-20-15
AF-125-30-15
AF-125-40-15
AF-150-20-15
AF-150-30-15
AF-150-40-15
300
250
200
150
100
50
0
7
Curing Period = 7 days
Figure 6.2 Comparison of UCS results of fly ash treated and AAFA treated soil samples, containing 15%
water or activator (3 Days Curing Period) .
91
Unconfined compressive strength (kPa)
650
600
550
500
450
400
F-15-20
F-15-30
F-15-40
AF-100-20-15
AF-100-30-15
AF-100-40-15
AF-125-20-15
AF-125-30-15
AF-125-40-15
AF-150-20-15
AF-150-30-15
AF-150-40-15
350
300
250
200
150
100
50
0
28
Curing Period = 28 days
Figure 6.4 Comparison of UCS results of fly ash treated and AAFA treated soil samples, containing 15%
water or activator (28 Days Curing Period) .
The variation of strength obtained for 10, 12.5 and 15 molal activator content, 20, 30 and
40% fly ash content and containing 20% fluid by weight of dry mass (water or activator)
mixed soil samples, after 3, 7 and 28 days curing periods is shown in Table 6.2.
The
variations are also shown in Figure 6.5. Figure 6.6-6.8 shows the gain in strength of all
mixes after 3, 7 and 28 days respectively in bar graph form. From the tables and graphs it is
evident that the 3 days strength is more in case of mix AF-100-20-20, while the 7 and 28 days
strength is more in case of mix AF-100-40-20 and AF-125-40-20 respectively. The least 3, 7
and 28 days strength is exhibited by mix F-15-40, F-20-40 and F-20-20 respectively. The 3
days maximum strength of AAFA treated soil sample is 3.4 times higher than the minimum
strength acquired by fly ash treated sample, while the 7 and 28 days maximum strength of
AAFA treated soil sample are 5.3 and 5.7 times higher than the minimum strength acquired
by fly ash treated sample respectively.
92
Unconfined compressive strength (kPa)
1050
1000
950
900
850
800
750
700
650
600
550
500
450
400
350
300
250
200
150
100
F-20-20
F-20-30
F-20-40
AF-100-20-20
AF-100-30-20
AF-100-40-20
AF-125-20-20
AF-125-30-20
AF-125-40-20
AF-150-20-20
AF-150-30-20
AF-150-40-20
0
5
10
15
20
25
30
Curing Period (Days)
Figure 6.5 Comparison of UCS results of fly ash treated and AAFA treated soil samples, containing 20%
water or activator
Unconfined compressive strength (kPa)
400
350
300
F-20-20
F-20-30
F-20-40
AF-100-20-20
AF-100-30-20
AF-100-40-20
AF-125-20-20
AF-125-30-20
AF-125-40-20
AF-150-20-20
AF-150-30-20
AF-150-40-20
250
200
150
100
50
0
3
Curing Period = 3 Days
Figure 6.6 Comparison of UCS results of fly ash treated and AAFA treated soil samples, containing 20%
water or activator (3 Days Curing Period) .
93
Unconfined compressive strength (kPa)
500
400
F-20-20
F-20-30
F-20-40
AF-100-20-20
AF-100-30-20
AF-100-40-20
AF-125-20-20
AF-125-30-20
AF-125-40-20
AF-150-20-20
AF-150-30-20
AF-150-40-20
300
200
100
0
7
Curing Period = 7 Days
Unconfined compressive strength (kPa)
400
350
300
250
F-20-20
F-20-30
F-20-40
AF-100-20-20
AF-100-30-20
AF-100-40-20
AF-125-20-20
AF-125-30-20
AF-125-40-20
AF-150-20-20
AF-150-30-20
AF-150-40-20
Figure 6.7 Comparison of UCS results of fly ash treated and AAFA treated soil samples, containing 20%
200
150
100
50
water or activator (7 Days Curing Period) .
0
3
Curing Period = 3 Days
Unconfined compressive strength (kPa)
1000
800
F-20-20
F-20-30
F-20-40
AF-100-20-20
AF-100-30-20
AF-100-40-20
AF-125-20-20
AF-125-30-20
AF-125-40-20
AF-150-20-20
AF-150-30-20
AF-150-40-20
600
400
200
0
28
Curing Period = 28 Days
Figure 6.8 Comparison of UCS results of fly ash treated and AAFA treated soil samples, containing 20%
water or activator (28 Days Curing Period) .
94
Unconfined compressive strength (kPa)
900
850
800
750
700
650
600
550
500
450
400
350
300
250
200
150
100
50
F-25-20
F-25-30
F-25-40
AF-100-20-25
AF-100-30-25
AF-100-40-25
AF-125-20-25
AF-125-30-25
AF-125-40-25
AF-150-20-25
AF-150-30-25
AF-150-40-25
0
5
10
15
20
25
30
Curing Period (Days)
Figure 6.9 Comparison of UCS results of fly ash treated and AAFA treated soil samples, containing 25%
water or activator.
The variation of strength obtained for 10, 12.5 and 15 molal activator content, 20, 30 and
40% fly ash content and containing 20% fluid by weight of dry mass (water or activator)
mixed soil samples, after 3, 7 and 28 days curing periods is shown in Table 6.3.
The
variations are also shown in Figure 6.9. Figure 6.10-6.12 shows the gain in strength of all
mixes after 3, 7 and 28 days respectively in bar graph form. From the tables and graphs it is
evident that the 3 days strength is more in case of mix AF-125-20-25, while the 7 and 28 days
strength is more in case of mix AF-150-40-25 and AF-125-40-25 respectively. The least 3, 7
and 28 days strength is exhibited by mix F-25-40. The 3 days maximum strength of AAFA
treated soil sample is 3.35 times higher than the minimum strength acquired by fly ash treated
sample, while the 7 and 28 days maximum strength of AAFA treated soil sample are 5.4 and
9.65 times higher than the minimum strength acquired by fly ash treated sample respectively.
Thus it can be concluded that AAFA treated soil samples exhibit more strengths than fly ash
treated soil samples.
95
Unconfined compressive strength (kPa)
130
120
110
100
90
80
F-25-20
F-25-30
F-25-40
AF-100-20-25
AF-100-30-25
AF-100-40-25
AF-125-20-25
AF-125-30-25
AF-125-40-25
AF-150-20-25
AF-150-30-25
AF-150-40-25
70
60
50
40
30
20
10
0
3
Curing Period = 3 days
Figure 6.10 Comparison of UCS results of fly ash treated and AAFA treated soil samples, containing 25%
water or activator (3 Days Curing Period) .
Unconfined compressive strength (kPa)
260
240
220
200
180
160
F-25-20
F-25-30
F-25-40
AF-100-20-25
AF-100-30-25
AF-100-40-25
AF-125-20-25
AF-125-30-25
AF-125-40-25
AF-150-20-25
AF-150-30-25
AF-150-40-25
140
120
100
80
60
40
20
0
7
Curing Period = 7 Days
Figure 6.11 Comparison of UCS results of fly ash treated and AAFA treated soil samples, containing 25%
water or activator (7 Days Curing Period) .
96
Unconfined compressive strength (kPa)
900
800
700
600
F-25-20
F-25-30
F-25-40
AF-100-20-25
AF-100-30-25
AF-100-40-25
AF-125-20-25
AF-125-30-25
AF-125-40-25
AF-150-20-25
AF-150-30-25
AF-150-40-25
500
400
300
200
100
0
28
Curing Period = 28 days
Figure 6.12 Comparison of UCS results of fly ash treated and AAFA treated soil samples, containing 25%
water or activator (28 Days Curing Period).
97
Chapter - 7
Study of rheological properties
of alkali activated fly ash
98
7.1 Setting time
This parameter was impossible to determine due to the very slow setting of the mixtures used,
which is known to be significantly slower than the setting time of cement based grouts.
During the tests it was possible to conclude that the setting process is not homogenous, since
the upper layer of the grout mass was hardening at a significant higher rate than the
remaining volume.
This was discovered when the Vicat‟s needle was able to puncture the upper layer of the
grout, exposing the fresh material underneath. The puncture would allow the upper harden
layer to mix with the fresh grout, which would result in the loss of the already achieved
hardness. Therefore, this test does not seem to be the most appropriate to evaluate this
parameter in activated fly ash grouts.
7.2 Viscosity
The results in Table 7.1 show that the viscosity of the alkaline grout is higher than that of the
cement grout. The higher viscosity can be a factor in the grout/soil mixing levels, which can
be overcome by increasing the water percentage in the activator. However, in so doing, the
activator/ash ratio is increased, while the Na2O/ash ratio is kept constant, therefore justifying
the study of the effects on strength.
Table 7.1 Density and Viscosity of cement and alkaline grouts
Binder
Density (gm/cm3)
Marsh Funnel (S)
Cement grout
1.58
39
Alkaline grout, 10 m (activator/ash = 0.89)
1.64
80
Alkaline grout, 12.5 m (activator/ash = 0.89)
1.76
95
Alkaline grout, 15 m (activator/ash = 0.89)
1.88
150
99
Chapter - 8
Conclusions and Future Scope
100
8.1 Summary
The stabilization of expansive soil has drawn attention to avoid its disastrous effect on
infrastructural components like road, building etc. In this work a new idea of stabilizing the
expansive soil using alkali activated fly ash was discussed. The chemical sodium hydroxide
and sodium silicate were used as a chemical activator for the fly ash. The method of sample
preparation, proportion of chemical additive, curing of sample and changes in basic
geotechnical properties of expansive soil is discussed.
8.2 Conclusions:
Based on the obtained results and discussion thereof following conclusions can be made.

The unconfined compressive strength soil is found to vary with concentration of
chemical in the activated fly ash and curing period.

10 molal samples are giving better 3 and 7 days strengths than 12.5 and 15 molal
samples, which make it economical as compared to 12.5 and 15 molal samples.

Long term strength is more in case of 12.5 molal samples.

Maximum 3 day strength attained by activated sample is 392.7 kPa, which is 3.25
times more than that attained by fly ash treated samples.

Maximum 7 day strength attained by activated sample is 546.88 kPa, which is 2 times
more than that attained by fly ash treated samples.

Maximum 28 day strength attained by activated sample is 977.09 kPa, which is 2.7
times more than that attained by fly ash treated samples.

There is a strong dependency between the activator/ash ratio and mechanical strength.
Results showed that it is advantageous to reduce this ratio since it has a positive effect
on strength results, which has also a positive effect on final cost.
101

Lowering the viscosity of the grout mixtures to similar values to that of cement grout
can have a negative effect on final strength, since it demands an increase in the
activator/ash ratio. Therefore, it is recommended that a compromise is made between
an optimum viscosity level and the lowest activator/ash ratio possible, whenever the
viscosity is a key issue for a particular application.

Alkali-activated fly ash can be used effectively as a chemical stabiliser for stabilising
expansive soils.
8.3 Scope for future study.

Efforts should be made to reduce the cost of operation, by searching other natural
alkaline materials.
102

Field application of this method, by using suitable technology.

Application of AAFA for stabilization of other low strength high compressible clay.

Use of other alkalis like Potassium and Lithium, to study their effect on Fly ash.
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