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International Journal of Engineering Trends and Technology (IJETT) – Volume 35 Number 10 - May 2016
ISSN: 2231-5381 http://www.ijettjournal.org Page 477
Engineering Properties of Black cotton soil
Modified with Fly ash and Cement Jaya Prakash Babu.V
#1, Satyanarayana.P.V.V
*2, Surya Manikantha
#3 Abdul Moin
#4
#1PG Student,
#2Professor,
#3,#4PG students &Civil eng. department& Andhra University
Visakhapatnam, India
Abstract: Black cotton soil is a typical volume
change soil which loses its strength on wetting due
to increase in its volume and in absence of water it
shows multiple cracks due to decrease in its
volume. This volume change behavior causes
distress when structures located on these soils and
also these soils can be used as construction
material.. Present paper describes the strength
behavior of Black cotton soil treated with fly ash as
stabilizer. Fly ash is a fine powder obtained from
burning of coal during the production of electricity.
Disposal of Fly ash is a big problem. To minimize
the disposal of Fly ash onto large land areas, it can
be used as a construction material in civil
engineering works. In this an attempt is made for
the utilization of Fly ash in bulk quantities by
adding it to expansive soil at various percentages
of cement and tests like plasticity, swell,
compaction and CBR tests were performed. From
the test results it is identified that addition of Fly
ash and cement decreases plasticity and improves
strength characteristics. Addition 32-40% Fly ash
and 6-8% cement attains higher CBR values and
improved swell characteristics.
Key words: Expansive soil, Fly Ash,
cement, CBR
1.0 INTRODUCTION:
Black cotton soils accounts about 20% of land area
in India and are predominantly located in the
Deccan trap covering the states. Most Indian Black
cotton soils are rich in Montmorillonate, this
mineral is responsible for swell-shrink behavior of
the soil. It is highly sensitive to moisture changes;
Katti(1979)2 has given properties of Black cotton
soils which have Liquid limit 40%-100%, Plastic
limit 20%-60%, Differential Free Swell index 20%-
100%.Structures located on these soils subjected to
differential settlements due to moisture variations
(Bala Subramanyam et.al 1989)1. Hence the
subgrade and its undesirable characteristics to be
modified using a suitable stabilization technique.
Stabilization involves the methods used for
modifying the properties of a soil to improve its
engineering performance. Keeping in this view
investigation carried out with fly ash. In India,
about 120 million tonns of coal ash is produced
annually.Coal-ash management poses a serious
environmental problem for India and requires a
mission-mode approach. Disposal of wastage
requires costly land at thermal power plants and the
transport of flyash to the ash ponds entail heavy
expenditure. some researchers
P.V.V.Satyanarayana et.al (2013)11
studied on the
Strength characteristics of Expansive soil-Fly ash
mixes at various moulding water contents,Kiran
B.Biradar et.al (2014)3 studied the Influence of
steel slag and Fly ash on Strength Properties of
Clayey soil, Ramakrishnan, A.K. et.al(2001)10
Stabilization of Annamalainagar Clay with lime-
Fly ash,Nalbantoglu, Satyanarayana.P.V.V et.al
(2013)12
studied the Bulk utilization of flyash lime
sodium silicate mixes in geotechnical
applications,Satyanarayana.P.V.V et.al(2016)13
studied on the Engineering Properties of Expansive
Soil Stabilized with Fly ash and Lime Mixes,
Prabakar, J.et.al (2003)9 studied Influence of fly
ash on strength behavior of typical soils,Sridharan,
A.et.al (1998)15 studied Use of Fly ash to improve
the CBR of soil, Pandian, N.S. et.al (2002)7 studied
California bearing ratio behavior of cement
stabilized fly ash-soil mixes, Kolias, S. et.al
(2005)4 studied Stabilization of Clayey soils with
high calcium fly ash and cement, Phanikumar, B.R.
et.al (2007)8 studied Volume changes Behaviour of
fly ash-stabilized clay, Pandian, N.S. et.al (2002)6
studied The pozzolanic effect of fly ash on the CBR
behaviour of black cotton soil.
In present investigation various percentages of Fly
ash and cement mixes are added to expansive soils
and effect of these mixes was studied in terms of
plasticity, compaction, swell and strength
characteristics.
2.0. MATERIALS:
To study the performance of Fly Ash and Cement
mixes on expansive soil, which is obtained from
delta areas of Godavari River in Bhimavaram,
Andhra Pradesh, India and Fly Ash was collected
from NPTC, Parawada of Visakhapatnam
district,Andhra Pradesh, India and cement of OPC
43 grade obtained from local markets.
2.1. Black cotton soil:
International Journal of Engineering Trends and Technology (IJETT) – Volume 35 Number 10 - May 2016
ISSN: 2231-5381 http://www.ijettjournal.org Page 478
Expansive soils in India are popularly known as
Black cotton soils. Expansive soil under study was
collected dried and pulverized into the required
sizes and tested for properties like gradation
,compaction, strength as per IS2720 and the results
are shown in table-1 and fig-1
Table.1.Geotechnical properties of Black cotton
soil
Fig-1: Gradation curve of Black Cotton soil
From the test results it is identified that it contains
fines (less than 75µm) of 95% .shows alluvial
origin out of which 40% of silt and 55% as clay
particles. The presence of fines contributed for high
liquid limit ( wL ) of 74% and plasticity index of
45% can be classified as CH soil based on IS1498
1970 It also exhibited high swelling characteristics
with FIS as 100 and swell pressure as 90kpa and
attained very low strength values under soaking in
terms of CBR as 1%.
2.2Fly ash: Fly ash was collected from National Thermal
Power Corporation (NTPC), which is located at
Parawada, Visakhapatnam, Andhra Pradesh. The
collected dried Fly Ash was subjected to various
geo-technical characterizations such as gradation,
compaction, strength, permeability etc., and the test
results are shown in table -2 and Fig 2(a),2(b)
Table 2. Geotechnical Characterizations of Fly ash
Fig-2: Gradation curve of Fly ash
Table 3. Chemical Composition of Flyash
From the test results it is identified that, it has 72%
fine particles (<75µm) and all these particles are
silt ranges. It is non-plastic and incompressible
material. It has low specific Gravity and attained
less dry Density with high Moisture Contents due
to nature of Flyash particles. From the chemical
composition it isd identified that it has less
percentage of CaO (1.74<15%) classified under
0
20
40
60
80
100
120
0.0001 0.001 0.01 0.1
% F
iner
Grain size (mm)
0
20
40
60
80
100
120
0.001 0.01 0.1 1
Fin
er (
%)
Particle size (mm)
Property Values
Gravel (%) 0
Sand (%) 4
Fines (%) 96
a) Silt 50
b) Clay 46
Liquid Limit (%) 74
Plastic Limit (%) 29
Plasticity Index (IP) 45
IS Classification CH
Optimum moisture content (OMC) (%) 26
Maximum dry density (MDD) (g/cc) 1.52
California bearing ratio (%) (CBR
Soaked) 1.0
Angle of shearing resistance (Ø)
15
Cohesion (t/m2)
10
Property Values
Gravel (%) 0
Sand (%) 28
Fines (%) 72
a. Silt (%) 72
b. Clay(%) 0
Liquid Limit (%) 28
Plastic Limit (%) NP
Specific gravity 2.1
Optimum moisture content (OMC) (%) 21
Maximum dry density (MDD) (g/cc) 1.28
California bearing ratio (CBR) (%) 4
Coefficient of uniformity (Cu) 28.89
Coefficient of curvature (Cc) 2.13
Compound Formula Percentage
SiO2 59.83
Al2O3 30.48
CaO 1.74
MgO 0.86
TiO2 6.91
V2O5 0.09
ZnO 0.09
International Journal of Engineering Trends and Technology (IJETT) – Volume 35 Number 10 - May 2016
ISSN: 2231-5381 http://www.ijettjournal.org Page 479
class F flyash (ASTM) and presence of high
percentages of sio2 and Al2O3 (90%) make the
Flyash Pozzolanic with addituion of Lime, Cement
and other additives.
3.0 RESULTS AND DISCUSSIONS
3.1 Effect of Fly ash on Engineering
Properties of Expansive Soils To study the effect of Fly ash on Expansive soil,
various percentage of fly ash i.e. 0,20,…50% by dry
weight of soil were added and effectively mixed and
tested for characteristics like consistency,
compaction, CBR and swell as per IS2720,as the
results are shown in table-4 and fig-3(a)-3(e)
Table 2. Various characteristics of soil-Fly ash
mixes
Fig 3(a).Consistency limits
Fig 3(b).OMC Vs FLY ASH (%)
Fig 3. MDD Vs FLY ASH (%)
Fig 3. FSI Vs FLY ASH (%)
Fig 3. CBR Vs FLY ASH (%)
From the consistency test data, it is identified that
as the percentage of fly ash is increasing liquid
limit and plasticity index values are decreasing and
plastic limit values are increasing. This
phenomenon is continued up to 30% after it
became non-plastic. The decrease in liquid limit is
due to the decrease in diffused double layer by
replacement of clay particles by fly ash particles
and increase in plastic limit is due to the
development of shear resistance at inter particle
level and the particles in soil-fly ash matrix require
more water to mobilize for rolling.
From the compaction test data it is
identified that with increasing the percentage of fly
ash OMC values are increasing and MDD values
are decreasing. This increase in OMC values are
0
10
20
30
40
50
60
70
80
0 10 20 30 40 50
Wat
er c
onte
nt
(%)
Fly ash (%)
Liquid limit
Plastic limit
Plasticity index
25
26
27
28
29
30
31
32
0 10 20 30 40 50 60
OM
C (
%)
Fly ash (%)
OMC
1.38
1.4
1.42
1.44
1.46
1.48
1.5
1.52
1.54
0 10 20 30 40 50 60
MD
D (
g/c
c)
Fly ash (%)
MDD
0
20
40
60
80
100
120
0 10 20 30 40 50 60
FS
I
Fly ash (%)
FSI
0
1
2
3
4
5
6
7
8
0 10 20 30 40 50 60
CB
R
Fly ash (%)
CBR
FLYASH
%
WL
%
WP
%
IP
%
OMC
%
MDD
g/cc
FSI
%
CBR
%
0 74 29 45 26 1.52 100 1
10 66 30 36 27 1.5 80 2.5
20 55 32 23 28 1.48 56 4
30 40 34 6 29 1.46 30 6
40 24 NP NP 30 1.43 15 7
50 NP NP NP 31 1.4 0 6.5
International Journal of Engineering Trends and Technology (IJETT) – Volume 35 Number 10 - May 2016
ISSN: 2231-5381 http://www.ijettjournal.org Page 480
due to the development of flocculated structure
which resists the compaction effort and the
particles in the soil-fly ash matrix requires more
water to mobilize and less solids occupied in the
given volume and low dry densities are also due to
nature and low specific gravity of fly ash particles
compared to clay particles.
It is also observed that with increasing
percentage of fly ash free swell values are
decreasing. At a dosage of 40% it became low
swelling and at 50% it is non-swelling. The
decrease in swelling characteristics is due to
decrease of the amount of repulsion between clay
particles due to replacement of clay by fly ash
particles.
From the test results of CBR it is identified
that as the percentage of Fly ash is increasing CBR
values are also increasing up to 40% and then
decreasing. Fly ash –Clay blend offers more
resistance compared to individual Fly ash particles
and clay particles.
3.2 Effect of Cement on Fly ash Stabilized
Expansive soil
To study the effect of Cement on
Fly ash stabilized expansive soil, various
percentage of cement i.e. 2,4,6,….10% by dry
weight of soil were added and effectively mixed
and tested for characteristics like compaction,
strength and swell as per IS2720,and the results are
shown in below.
Table.5.Various Characteristics of Lime Stabilized
Expansive soil fly ash mixes
Fig 4(a).FSI (%) Vs CEMENT (%)
Fig 4(a).OMC (%) Vs CEMENT (%)
-10
0
10
20
30
40
50
60
0 2 4 6 8 10
FS
I
CEMENT (%)
20% Fly ash
30% Fly ash
40% Fly ash
20
25
30
35
40
0 2 4 6 8 10
OM
C (
%)
CEMENT (%)
20% Fly ash
30% Fly ash
40% Fly ash
CEMENT
(%)
FLY ASH (%)
20 30 40
OMC
(%)
MDD
(g/cc)
FSI
%
CBR
%
OMC
(%)
MDD
(g/cc)
FSI
% CBR
%
OMC
(%)
MDD
(g/cc)
FSI
%
CBR
%
0 28 1.48 56 4 29 1.46 30 5 30 1.43 15 6
2 28.5 1.47 40 10 35 1.48 10 12 31.5 1.45 0 15
4 29 1.46 15 20 32 1.5 0 26 33 1.47 0 30
6 29.8 1.45 0 34 33.5 1.52 0 48 34.5 1.49 0 54
8 31 1.44 0 52 35 1.54 0 68 36 1.51 0 80
10 32 1.43 0 74 37 1.55 0 84 37.5 1.53 0 90
International Journal of Engineering Trends and Technology (IJETT) – Volume 35 Number 10 - May 2016
ISSN: 2231-5381 http://www.ijettjournal.org Page 481
Fig 4(a).MDD (g/cc) Vs CEMENT (%)
Fig 4(a).CBR (%) Vs CEMENT (%)
Compaction test data shows that with
increasing the percentage of fly ash & cement OMC
values are increasing & MDD values are decreasing.
Increase in OMC values are due to increase in
cement concentration in pore water makes the
particle further flocculate and more pore water is
needed to mobilize the particle against compaction
effort and hydration of cement is also responsible.
Decrease in MDD values are due to occupation of
solids contributed less weight due to replacement of
clay particles by Fly ash particles and acceleration of
flocculated structure by cement particles.
From the test results it is also identified
that as the percentage of Fly ash and cement
increases Differential Free Swell Index values
decreases. At 4% dosage of cement with respective
to all Fly ashes the soil became non-swelling.
Addition of cement makes the soil-Fly ash matrix
move repultant against swelling due to absorption
of calcium particles on to the surface of clay
particles.
CBR test data shows the increase in
percentage of cement increases the CBR values of
soil-Fly ash matrix and attained high CBR values at
dosage of 8% of cement. Addition of cement to
soil-Fly ash blends offers more resistance against
compression is due to development of cementitious
compounds and became crystalline over a period of
time.
APPLICATIONS:
1. Addition of 40% Fly ash to Black cotton
soil attained CBR value of 7% with non-
plastic and low swelling can be used as
Sub-Grade material.
2. Addition of 4% cement and 30-40% Fly
ash to the Black cotton soil attained CBR
values 26-30% can be used as Sub-Base
material.
3. Addition of 8-10% cement and 32-40% of
Fly ash to the Black cotton soil attained
CBR value 80% can be used as Base
course material.
CONCLUSIONS:
High Expansive Black cotton soil can be
effectively utilized as a Geo technical material by
addition of 30-40% fly ash and 6-10% cement. At
these dosage of admixtures the Black cotton soil
can be behaves non-plastic and non-swelling can
reduce the problems of volume change. Bulk
utilization of Fly ash reduces its deposal problem.
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c0
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International Journal of Engineering Trends and Technology (IJETT) – Volume 35 Number 10 - May 2016
ISSN: 2231-5381 http://www.ijettjournal.org Page 482
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