The document studied the effect of bottom ash on soil properties through a series of experiments. Standard Proctor tests showed maximum dry densities increased with 8-12% bottom ash but decreased at 16%. Unconfined compressive strength peaked at 12% bottom ash but California bearing ratio values decreased with bottom ash. The optimum bottom ash content was determined to be 12% based on improving dry density and unconfined compressive strength while still providing adequate bearing capacity.

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International Journal of Civil Engineering and Technology (IJCIET)
Volume 8, Issue 2, February 2017, pp. 117–127 Article ID: IJCIET_08_02_012
Available online at http://www.iaeme.com/IJCIET/issues.asp?JType=IJCIET&VType=8&IType=2
ISSN Print: 0976-6308 and ISSN Online: 0976-6316
© IAEME Publication Scopus Indexed
EFFECT OF BOTTOM ASH ON THE SOIL
S. Saravanan
Student, School of Civil Engineering, SASTRA University,
Thanjavur, Tamilnadu, India
Sirigiri Manikanta
Student, School of Civil Engineering, SASTRA University,
Thanjavur, Tamilnadu, India
C. Venkatsubramanian
Faculty, School of Civil Engineering, SASTRA University,
Thanjavur, Tamilnadu, India
D. Muthu
Faculty, School of Civil Engineering, SASTRA University,
Thanjavur, Tamilnadu, India
ABSTRACT
Background/Objectives: The Effect of Bottom Ash over the Soil is carried out by
conducting Suitable Soil Experiments.
Methods/Statistical Analysis:
Experiments such as Standard Proctor Test (SPT), Unconfined Compressive strength
(UCS) and California Bearing Ratio (CBR) repeatedly over the soil for different percentages
of bottom as such as 8%, 12% and 16% by weights and the results are analyzed with respective
to the results obtained for the natural soil. The experiments are conducted as per Indian
standards of light compaction.
Findings: The results show the increasing values of maximum dry density and the UCS
values for treated sample and there is a decrease of CBR value with the addition of bottom ash.
The maximum dry densities obtained for natural soil, treated soil sample with 8%, 12% and
16% of bottom ash are 17KN/m3
, 21 KN/m3
, 22 KN/m3
and 20 KN/m3
respectively and thus a
maximum of 22 KN/m3
for 12% addition of bottom ash.
Improvements/Applications: Thus, the Optimum Moisture Content of 16% for natural soil
and 11.5%, 11% and 13% for the 8%, 12% and 16% of treated soil. Similarly, the UCS values
for the Natural soil, treated soil for 8%, 12% and 16% as 270 KN/m2
, 265 KN/m2
, 350 KN/m2
and 230 KN/m2
, thus having maximum for 12% of treated soil. But the CBR values are shown
poor results as 3.66% for natural soil and 2.18%, 2.35% and 1.98% for respective percentages
of treated soil for 8%, 12% and 16% of bottom ash.
Key words: Stabilization, Bottom Ash, CBR Test, SPT, Natural Soil

2. Effect of Bottom Ash on the Soil
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Cite this Article: S. Saravanan, Sirigiri Manikanta, C. Venkatsubramanian and D. Muthu,
Effect of Bottom Ash on the Soil. International Journal of Civil Engineering and Technology,
8(2), 2017, pp. 117–127.
http://www.iaeme.com/IJCIET/issues.asp?JType=IJCIET&VType=8&IType=2
1. INTRODUCTION
Stabilization of soil is given prior concern in Civil Engineering and for sub-grade to be served for long
life thus different techniques are been adopted for stabilization of soil. Some of the stabilization
techniques involve addition of different materials for different percentages to obtain the required
strength to the soil. Different stabilizers such as lime stone, cement, chemical components, bio
enzymes and wastes are used. Bottom ash addition significantly changes the soil properties of
cohesion and unconfined strength for the soil tested. The use of bottom ash must be balanced with the
specific soil to be used [1]
. The Resilient Modulus of the Bottom Ash varies depending on the physical
properties and unit weight of the bottom ash. Therefore, mixing the bottom ash with subgrade soil
showed increased resilient modulus [2]
.
Recently the studies are made over the soil by the use of different waste materials as the stabilizers
as they are environment friendly and economical if they are available locally. Several waste products
such as rice husk, fly ash, blast furnace slag, cement kiln dust etc., are been used as the stabilizer.
This project deals with the use of bottom ash a byproduct obtained from the thermal industries as
the stabilizing component for the soil and the effects over the soil are been studied.
2. METHODOLOGY
The local soil which is used for the minor works of back fill is been collected and the effects of
addition of the bottom ash over this soil are studied. Initially the index properties of the natural soil
such as specific gravity, sieve analysis, liquid limit and plastic limit are found by conducting
experiments over the soil and thus the natural soil is classified as Per the Indian standards. Next the
experiments such as SPT, UCS and CBR are been conducted to find the engineering properties of the
natural soil. Then the soil is treated with the bottom ash with respect to percentage weights such as
8%, 12% and 16% and the experiments such as SPT, UCS and CBR are repeatedly conducted for
different percentages of bottom ash and the results are being compared with the results that are
obtained for the natural soil. Thus, providing the conclusion on the effect of bottom ash over the
collected natural soil sample.
3. RESULTS AND DISCUSSION
3.1. Natural Soil Results
3.1.1. Specific Gravity (G)
The specific gravity of the natural soil is found by using Pyconometer (Figure 3.1a) and it is found to be 2.59.
Figure 3.1 (a) Pyconometer

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3.1.2. Sieve Analysis
Specific amount of the soil is taken and the passed through the sieves (Figure 3.1b) by means of sieve
shaker. A semi log graph is plotted with the obtained results by taking percentage finer along regular
scale and diameter of the particles along the log scale. The plotted graph is shown in Graph 3.1a
below.
Figure 3.1 (b) 2 IS Sieves
Graph 1 (a) Sieve Analysis
Thus, from the below graph, the results such as effective diameter (D10), D30 and D60 are found
to be 0.026mm, 0.1mm and 0.27mm respective. Thus, the co-efficient of uniformity (Cu) and Co-
efficient of curvature (cc) are found to be 10.3 and 1.3 respectively. Hence from the obtain results, and
the observation it is found to be Well Graded Sand (SW). But the percentages of the particles passing
through 75micron sieve are less than 2.5% thus the soil compresses dual properties which is obtained
from liquid limit and plastic limit of the soil.
3.1.3. Liquid Limit (wL)
Plastic limit of the soil is found by using Casagrande apparatus (Figure 3.1c) and the results are
obtained from the graph plotted between number of blows and percentage of moisture content in semi
log graph as shown in Graph 3.1.b below. Thus, the liquid limit of the soil is obtained to be 40%.

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Figure 3.1 (c) Casagrande apparatus
Graph 3.1 (b) Liquid Limit
3.1.4. Plastic Limit (wP)
The plastic limit of the soil is obtained by rolling the soil in to 3mm diameter treads and it is found to
be 19.5%. Thus, the plasticity index of the soil is wL – wP = 20.5%.
Thus, from the above results it is found to be medium plasticity clay (CI), thus as per Indian
Classification of soil the soil is classified as SW-CI.
3.1.5. Standard Proctor Test (SPT)
SPT on the soil is conducted as per Indian light compaction by standard proctor apparatus (Figure
3.1d) and the results are obtained from the graph plotted between dry density and moisture content as
shown in Graph 3.1c. Thus, the Optimum Moisture Content (OMC) and maximum dry density
obtained is 16% and 17 KN/m3
respectively.
Figure 3.1 (d) Standard Proctor Test Apparatus

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Graph 3.1 (c) SPT for Natural Soil
3.1.6. Unconfined Compressive Test (UCS)
UCS of the soil is sample is found by using unconfined compressive test machine (Figure 3.1e) and
the graph is plotted between stress and strain as shown in Graph 3.1.d. Thus, the Unconfined
Compressive Strength of the soil is obtained is 270 KN/m2
.
Figure 3.1 (e) UCS apparatus
Graph 3.1 (d) UCS for Natural Soil

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3.1.7. California Bearing Ratio (CBR)
CBR value of the soil is obtained by using CBR apparatus (Figure 3.1f). Thus, a graph is plotted from
the obtained results by taking penetration and Load along the axis as shown in Graph 3.1e. Thus, the
CBR value of the soil is found to be 3.66%.
Figure 3.1 (f) CBR Apparatus
Graph 3.1 (e) CBR for Natural Soil
3.2. Treated Soil Results
3.2.1. Standard Procter Test (SPT)
SPT on the soil is conducted with the addition of 8%, 12% and 16% of the bottom ash and the results
are obtained by the graph plotted between moisture content and dry density as shown in the graph
below. The resulted graph of SPT for 8%, 12% and 16% of addition of bottom ash is shown in Graph
3.2.1 a, 3.2.1 b, and 3.2.1 c respectively. Thus, the results obtained from the graph are, maximum dry
density of soil for 8%, 12% and 16% are 21 KN/m3
, 22 KN/m3
and 20 KN/m3
respectively, and
Optimum Moisture Contents are 11.5%, 11% and 13% respectively.

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Graph 3.2.1 (a) SPT for 8% Bottom Ash
Graph 3.2.1 (b) SPT for 12% Bottom Ash
Graph 3.2.1 (c) SPT for 16% Bottom Ash
Graph 3.2 Graph Showing Max. Dry Density & OMC with Different Percentage of Bottom Ash
0
5
10
15
20
25
Max Dry
Density
kN/m^3
OMC
8%
12%
16%

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3.2.2. Unconfined Compressive Strength (UCS)
The UCS of the soil treated with the bottom ash with 8%, 12% and 16% are obtained by plotting the
graph between the stress and strain as shown in graph below. Thus, the results obtained for 8%, 12%
and 16% are shown in Graph 3.2.2 a, 3.2.2 b and 3.2.2 c respectively. Thus, from the graph the UCS
of the soil treated with 8%, 12% and 16% are found to be 265 KN/m2
, 350 KN/m2
and 230 KN/m2
respectively.
Graph 3.2.2 (a) UCS for 8%Bottom Ash
Graph 3.2.2 (b) UCS for 12% Bottom Ash
Graph 3.2.2 (c) UCS for 16% Bottom Ash

9. S. Saravanan, Sirigiri Manikanta, C. Venkatsubramanian and D. Muthu
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0
50
100
150
200
250
300
350
400
UCS kN/m^2
8%
12%
16%
Graph 3.2.2 Showing UCS Results with Increasing Bottom Ash Content
3.2.3. California Bearing Ratio (CBR)
CBR values for the treat soil are shown in the Graph 3.2.3 a, 3.2.3 b and 3.2.3 c for addition of 8%,
12% and 16% of bottom ash respectively. The graph is plotted between penetration and load as shown
in the below graphs. Thus, the CBR value obtained are 2.18%, 2.35% and 1.98% for 8%, 12% and
16% addition of bottom ash respectively.
Figure 3.2.3 (a) CBR for 8% Bottom Ash
Figure 3.2.3 (b) CBR for 12% Bottom Ash

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1.6 1.8 2 2.2 2.4
CBR %
16%
12%
8%
Figure 3.2.3 (c) CBR for 16% Bottom Ash
Graph 3.2.3 Showing CBR Results with Increased Bottom Ash Content
4. CONCLUSION
From the experimental investigation carried out the following results were concluded.
 The OMC, Dry density, UCS and CBR Values of untreated natural soils are 16%, 17KN/m3,
270KN/m2 and 3.66% respectively.
 The OMC’s that are obtained by the addition of 8%, 12% and 16% bottom ash are 11.5%, 11% and
13% respectively.
 Thus, the dry densities that are obtained by the addition of 8%, 12% and 16% bottom ash are 21KN/m3
,
22KN/m3
and 20KN/m3
respectively, the Dry Density of the soil increased with the addition of bottom
ash and it is maximum for the addition of 12% bottom ash i.e., 22KN/m3
for OMC of 11%.
 The UCS values that are obtained by the addition of 8%, 12% and 16% bottom ash are 265KN/m2
,
350KN/m2
and 230KN/m2
respectively and obtained a maximum UCS of 350KN/m2
for addition of
12% bottom ash for which the values are higher than the values that are obtained for an untreated
natural soil sample.
 The CBR values that are obtained for addition of 8%, 12%, and 16% bottom ash are 2.18%, 2.35% and
1.98% respectively. Hence from the analysis it has been noticed that the CBR values have been
decreased with the addition of bottom ash.
As the CBR values are poor, this kind of stabilizer is not suitable for the stabilization of the above
classified soil and hence not advisable for the use of sub-grade for road pavements.

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