International Journal of Engineering Trends and Technology (IJETT) – Volume 28 Number 1 - October 2015
Effect of Modified Compaction on Grain Size Distribution
and Permeability of Flyash-Granular Soil Mixtures
Ratna Prasad, R1.
2
Darga Kumar, N2.
1
Research Scholar, JNTU Kakinada and Professor of Civil Engineering, VVIT, Guntur, AP, India.
Professor of Civil Engineering College of Engineering, Science and Technology (CEST), Fiji National University (FNU)
Abstract — Use of self-cementitious fly ash in
stabilizing the gravel roads to form a stable base for
hot mixed asphalt layer is of great interest. A
comprehensive idea on grain size distribution of fly
ash-granular soil mixtures when subjected to modified
compaction is essential to estimate the quantity and
cost of granular soil to be used in the pavement
construction. In this paper, the results pertinent to the
gradation changes of fly ash-granular soil mixtures
due to the modified compaction were brought out. The
fly ash used in the investigation was obtained from
Vijayawada Thermal Power Station (VTPS)
Vijayawada and the granular soil was collected from
Chekuru Village, Guntur, AP, and India. The
proportions of fly ash used are 0%, 5%, 10%, 15%,
20%, 25% and 30% by dry weight of the granular soil.
The granular soil compacted at 5% of fly ash showed
higher dry density compared to all other proportions
of fly ash. The grain size distribution of fly ash granular soil mixtures, before subjecting them to the
modified compaction were seen that as the percentage
of fly ash increases from 0% to 30%, the percentage
fine fraction passing over 0.075mm size sieve is
increased from 0.35% to 1.8%. The same mixtures
where fly ash content varied from 0% to 30%, when
subjected to modified compaction revealed that there
is a change in the grain size distribution of fly ash
granular soil mixtures and the percentage fine
fraction passing through 0.075mm size has increased
from 1.8% to 6.67%. Increased fine fraction due to the
modified compaction has to be necessarily accounted
in the estimation of cost of granular soil to be used in
the pavement construction.
Keywords: Granular soil, fly ash, compaction effort,
grain size, OMC, MDD, permeability, coefficient of
permeability.
I. INTRODUCTION
Fly ash can be used for construction of road and
embankment very effectively. This utilization has
many advantages over conventional methods such as:
(i) Saves top soil which otherwise is conventionally
used (ii) Avoids creation of low lying areas (by
excavation of soil to be used for construction of
embankments), (iii). Avoids recurring expenditure on
excavation of soil from one place for construction and
filling up of low lying areas thus created, (iv) Does not
deprive the nation of the agricultural produce that
would be grown on the top soil which otherwise
ISSN: 2231-5381
would have been used for embankment construction,
(v).
Reduces
the demand
of land
for
disposal/deposition of fly ash that otherwise would not
have been used for construction of embankment and
(VI). Controls the source of pollution. There are many
investigations carried out towards utilization of fly ash
especially in stabilizing the swelling soils (Kate, 1998;
Erdal Cokca, 2001; Pandian et al, 2002; Phani Kumar
and Sharma, 2004; Rao and Shivananda, 2005; Prasad
et al, 2010; Sivapullaiah and Arif, 2011). There are
few studies available in the literature relevant to the
utilization of fly ash along with granular soils in the
road construction. The present study is focused mainly
to understand the effect of modified compaction on
Grain size distribution of fly ash granular soil
mixtures. Fly ash consists of often hollow spheres of
silicon, aluminium and iron oxides and un-oxidized
carbon. Expansive soils can be potentially stabilized
effectively by cation exchange using fly ash.
Utilization of fly ash towards engineering applications
can solve two major issues: (i). environmental
pollution problem and (ii). Wastage of land due to its
dump on the agricultural land. Nicholson presented a
number of patents (1977, 1982) for a series of
investigations on cement kiln dust (CKD) and fly ash
mixtures for producing sub base materials with
different aggregates. CKD was used up to 16% by
weight of the mixture, producing a durable mass by
reacting with water at ambient temperatures. The most
widely used application for self-cementing fly ash is
in increasing the strength of unsuitable or unstable
subgrade materials. Generally, clay soils have soaked
CBR values from 1.5% to 5% (Rollings and Rollings
1996), which provides very little support to the
pavement structure. Addition of 16% self-cementing
fly ash increases the soaked CBR values of heavy clay
soils into the mid-30s, which is comparable to gravelly
sands (Rollings and Rollings 1996). Prasanna Kumar
(2011) studied the cementitious compounds formation
using pozzolans and their effects on stabilization of
soils such as black cotton soils and red earth soils for
varied proportions of fly ash. The findings reveals that
the maximum dry density of the BC soil increased
from 13.6 to 15.2kN/m3 for addition of 40% fly ash
obtained from Nyveli (NFA). For Red earth MDD
changed from 14.6 to 17.8kN/m3 for NFA addition.
Pozzolanic fly ash has shown considerable
improvement in compressive strength from 310kPa to
1393kPa for BC soil and from 590kPa to 2342kPa for
Red Earth, for addition of 30% of Fly ash, NFA. But a
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International Journal of Engineering Trends and Technology (IJETT) – Volume 28 Number 1 - October 2015
comprehensive idea about geotechnical aspects of fly
ash – gravelly sand mixtures for various engineering
applications especially for pavement construction have
not yet understood clearly.
II. EXPERIMENTAL STUDY
A. Soil
The gravelly sand used in the present study was
collected from Chekuru village near Guntur, Andhra
Pradesh state, India. The soil collected was kept in
controlled conditions in the laboratory and was used
for testing as per the Indian Standard specifications
given in the respective test codes. For this soil, the
basic tests were conducted in the laboratory for its
characterization. As per the basic properties of soils
are concerned, it indicates that the soil is greyish to
brown in colour and has soil proportions of gravel,
sand and little fine fraction. The soil has 0.35% slit
and clay, 92% sand and 7% gravel fractions. The grain
size distribution curve of the soil is presented in Fig.1.
The various basic properties of soil are presented in
the Table.1
B. Fly Ash
The fly ash used in this investigation was collected
from Vijayawada Thermal Power Station (VTPS)
Vijayawada, Andhra Pradesh, India. The fly ash
sample collected was stored in the air tight containers.
The grain size distribution curve [IS: 2720 (Part 4)1985] for fly ash is presented in the Fig.1 The various
properties of the fly ash obtained from the Vijayawada
Thermal Power Station (VTPS), Vijayawada, AP state,
India are presented in the Table.2. The fly ash
proportions adopted in the study by dry weight of soil
are 0%, 5%, 10%, 15%, 20% , 25% and 30%.
Table.1 Basic properties of soil
Property
Specific gravity
Optimum Moisture Content, OMC (%)
- Light Compaction
Optimum Moisture Content, OMC (%)
-Modified Compaction
Maximum Dry Density, MDD (kN/m3)
- Light Compaction
Maximum Dry Density, MDD (kN/m3)
- Modified Compaction
% Gravel
% Coarse Sand
% Medium Sand
% Fine Sand
% Silt & Clay
Effective Diameter, D10 (mm)
Coefficient of Uniformity, cu
Coefficient of Curvature, cc
Soil Classification
Value
2.62
09.36
08.00
19.52
19.90
07.50
12.50
42.10
37.25
00.35
00.21
04.28
00.76
SW
Table.2 Properties of fly ash
Property
Specific Gravity
Optimum Moisture Content OMC(%}
-Light Compaction
Optimum Moisture Content OMC (%)
-Modified Compaction
Maximum Dry Density, MDD (KN/m3)
- Light Compaction
Maximum Dry Density, MDD (KN/m3)
– Modified Compaction
% Gravel
% Sand
% Silt and Clay
Value
1.97
19.5
18
12.85
13.80
0.0
97.5
2.5
100
90
80
% Passing
70
SOIL
C. Tests Conducted
FLYASH
The fly ash proportions adopted in the study along
with the gravelly sand are 0%, 5%, 10%, 15%, 20%,
25% and 30% by weight of dry soil. The tests such as
Modified Compaction test [IS: 2720 (Part 7)-1980],
the grain size distribution test was conducted as per
the specifications given in the IS: 2720 (Part 4)-1985.
The modified compaction tests are adopted because
the majority highway pavements are designed for high
volume traffic loading.
60
50
40
30
20
10
0
0.01
0.1 Particle Size1 (mm)
Fig.1 Grain size distribution curve for soil and fly ash
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10
D. Grain Size Distribution
The grain size distribution test was conducted as per
the specifications given in the IS: 2720 (Part 4)-1985.
The graphs plotted between percent passing vs.
particle size for the various proportions of
flyash in granular soil.
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International Journal of Engineering Trends and Technology (IJETT) – Volume 28 Number 1 - October 2015
E. Compaction Test
120
F. Permeability Test
This test is conducted to find out the permeability
values of flyash-soil mixtures using variable head. The
tests have been carried out as per IS: 2720 of (Part
17)-1986. The tests were conducted on soil flyash
mixes prepared at their optimum moisture contents
(OMC) corresponding to flyash mixtures of 0%, 5%,
10%, 15%, 20%, 25% and 30%.
0% FA
5% FA
10% FA
15% FA
20% FA
25% FA
30% FA
100
% Passing
IS light and modified compaction tests have been
conducted on the soil with different percentages of
flyash such as 5%, 10%, 15%, 20%, 25% and 30%
and determined the Optimum Moisture Content (OMC)
and Maximum Dry Density (MDD) as per IS:2720
(Part 7)-1980
80
60
40
20
0
0.01
0.1 Particle Size (mm)
1
10
Fig 2: Grain size distribution curves for flyash mixed granular soil
before modified Compaction
III Results and Discussions
The grain size distribution tests were conducted as per
the specifications given in the IS: 2720 (Part 4)-1985.
Fig.1 presents the grain size curves for untreated
gravelly sand and pure flyash. The grain size
distribution curves for flyash gravelly sand mixtures
mixed at different proportion of flyash such as 0%,
5%, 10%, 15%, 20%, 25% and 30% are presented in
Fig.2. These curves are concerning to flyash granular
soil mixtures without subjecting to modified
compaction. Fig.3 presents the grain size distribution
curves for flyash–granular soil mixtures prepared at
0%, 5%, 10%, 15%, 20%, 25% and 30% of flyash and
subjected to modified compaction, to know the effect
of compaction on the gradation response. From the
figures 2 &3 it is observed that as percentage of
addition of flyash increasing from 0% to 10% ,the
percentage finer fraction increases from 0.35% to
1.39% and decreases for 10% to 20% flyash soil
mixture from 1.39% to 0.6% and increases for 20% to
30% flyash soil mixture from 1.34% to 1.8% ,
whereas sieve analysis conducted on the gravel soil
mixture which was subjected to modified compaction
reveals that the percentage finer fraction decreases for
0% to 10%
120
0% FA
5% FA
10% FA
15% FA
20% FA
25% FA
30% FA
100
80
% Passing
A. Grain Size Characteristics of Flyash- Granular
Soil
60
40
20
0
Fig 3: Grain size distribution curves for flyash mixed granular soil
after modified Compaction
Table 3 Grain size distribution of fly ash mixed
granular soil before subjected to modified compaction
%Proportion
0%
FA
5%
FA
10%
FA
15%
FA
20
%
FA
25%
FA
30
%
FA
Gravel
7.5
13.6
2.0
7.81
7.21
4.74
6.67
Coarse Sand
12.5
10.56
7.57
7.87
6.98
Medium Sand
42.1
37.64
46.43
35.02
31.68
7.23
28.8
2
Fine Sand
37.25
36.97
42.6
48.1
8.46
32.5
1
50.3
2
54.4
54.8
Silt & Clay
0.35
0.98
1.39
0.74
0.6
1.34
1.8
Table 4 Grain size distribution of fly ash mixed
granular soil after subjected to modified compaction
ISSN: 2231-5381
% Proportion
0%
FA
5%
FA
10%
FA
15%
FA
20%
FA
25%
FA
30%
FA
Gravel
11.5
14.69
13.5
7.18
5.84
5
4
Coarse Sand
11.65
12.31
8.9
9.82
8.52
7.81
6.32
Medium Sand
41.15
42.2
40.6
Fine Sand
28.8
24.8
29.2
4
39.5
3
34.3
2
Silt & Clay
1.8
1.65
3.28
4.25
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36.64
39.34
4.91
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33.9
9
43.8
7
5.84
29.68
46
6.67
International Journal of Engineering Trends and Technology (IJETT) – Volume 28 Number 1 - October 2015
flyash soil mixture from 1.8% to 1.65% and then
increases for 10% to 30% flyash soil mixture from
1.65% to 6.67% .From this we can concluded that as
addition of percentage of flyash in soil increases,
percentage fines in soil increases after compaction.
The Grain Size distribution of flyash mixed granular
soil before and after compaction are given in tables 3
and table 4.
B. Compaction Characteristics
In case of pure gravelly sand as the compactive effort
increases the water content is reducing and the
maximum dry density is increasing. Due to the
increase in compactive effort the maximum dry
density is increased from 19.95kN/m³ to 20.9kN/m³
similarly the optimum moisture content is decreased
from 8 to 7.5%. Similarly in the case of pure flyash as
the compaction effort increases the MDD of fly ash is
increasing from 12.65 to 13.85kN/m³ and the OMC of
fly ash is decreasing from 19.5 to 18 %. The
compaction curves of gravelly sand are placed high as
compared to the compaction curves of flyash shown in
fig.4. It can be attributed that the fly ash has low
specific gravity and is a light weight material. Fig. 5
presents the compaction curves for different
proportions of flyash added to the gravelly sand and
tested under modified compaction. From this figure, it
can be noticed that the compaction curves are
following the typical trend of granular soils.
As the compactive efforts increases, the reduction in
OMC is found to be 4 to 7% for the flyash proportions
of 0% to 25%. This reduction in OMC is little higher
for the flyash proportions of 0 to 10% and thereafter
the reduction in OMC seems to be lower. From this
trend, it can be understand that the influence of
compaction effort may not be present for higher
percentages of fly ash. When the percentages of flyash
increases the MDD is increasing up to about 10% of
flyash and thereafter there is a reduction in MDD with
further increasing of flyash content. The higher MDD
values are noticed under the modified compaction.
Values of OMC and MDD with the Percentage of
flyash are shown in the tables 5 & 6
Table 5 Values of OMC with the % of Flyash
Optimum Moisture Content
% Flyash (OMC, %)
Modified Compaction
0.0
08.00
0.5
08.15
10
08.35
15
09.25
20
10.00
25
10.10
30
10.30
100
17.90
Dry Density (kN/m3)
22
Table 6 Values of MDD with the % of Flyash
20
18
20
25
30
100
18.75
18.62
17.52
12.90
Light Compaction-Soil
16
Modified CompactionSoilL
Light Compaction- FA
14
12
Modfied CompactionFA
10
0
2
4
6
8 10 12 14 16 18 20 22 24
Wa ter Content (%)
Fig. 4 Compaction curves for gravelly sand and flyash subjected to
light and modified compaction
20.5
0% FA
5% FA
10% FA
15% FA
20% FA
25% FA
30% FA
20
19.5
Dry Density (kN/m3)
0.0
5.0
10
15
Maximum Dry Density (MDD)
(kN/m3)
Modified Compaction
19.9
19.6
19.58
18.85
% Flyash
19
18.5
18
17.5
17
C. Permeability Characteristics
To know the permeability characteristics of flyash
granular soil, falling head permeability test was
conducted with different proportions of flyash in
granular soil by weight. As percentage of flyash
increases from 0% to 15% the permeability decreases
and from 15% to 25%, the permeability values varies
slightly and for 25% to 30% flyash the permeability
values increases as shown in the figure 6.
16.5
16
0
2
4
6
8
10 12
% Wa ter Content
14
16
18
Fig.5 Compaction curves for flyash gravelly sand mixtures
subjected to modified compaction
ISSN: 2231-5381
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International Journal of Engineering Trends and Technology (IJETT) – Volume 28 Number 1 - October 2015
Permeability(x10 -5cm/s)
0
Flyash %
10 20 30 40 50 60 70 80 90 100
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
Permeability vs % Flyash
observations we conclude that the addition of fly ash
in soil increases % fines after compaction . As
percentages of fly ash increases from 0% to 15% the
permeability decreases and from 15% to 25% the
permeability values varies slightly and for 25% to
30% the values increases .So it can be suggested that
from 0% to 25% fly ash percentage can be used along
with granular soil.
V.REFERENCES
[1]
[2]
Fig 6 Variation of permeability of granular soil with %of flyash
[3]
Table 7 the values of permeability with percentage of
[4]
[5]
flyash
% Fly Ash
Coefficient of Permeability, k
(cm/sec)
(Falling Head Method)
0.0
5.0
10
15
20
25
30
100
[6]
[7]
-5
4.265 x10
1.173 x 10-5
0.239 x 10-5
0.034 x 10-5
0.163 x 10-5
0.0625x 10-5
1.125 x 10-5
5.710x10-5
[8]
[9]
[10]
[11]
From the table 7, it is observed that, as percentage of
flyash increases, the permeability decreases up to 15%
and slightly varies from 15% to 25% and then
increases from 25% to 30%.
[12]
[13]
[14]
IV. Summary and Conclusions
The MDD decreases drastically from 10% to15% and
25% to 30% in light compaction with increase of %
fly ash from 0% to 30%.But from 0% to 10% and 25%
to 30% fly ash, the MDD decreases slightly in
modified compaction. The addition of percentage Fly
ash in soil gravel mixture, OMC increases both in
light and modified compaction and increases slightly
from 0% to 10% and drastically increases from 10% to
25% and slightly increases from 25% to 30% in light
compaction and modified compaction. By increase of
addition of fly ash in gravel sand mixture, the water
holding capacity increases due to increase of silt
fraction. From 0% to 30%, the percentage fraction
passing over 75 micron sieves is increasing 0.35% to
1.8% when the flyash gravel soil mixtures without
subjecting to modified compaction. In modified
compaction , the percentage fraction passing over
75micron sieves is increasing from 1.8% to 6.67% as
the fly ash increases from 0% to 30%.From the above
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[16]
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[18]
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