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PERPUSTAKAAN UMP
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THE EFFECTS OF RICE HUSK ON THE COMPACTION PROPERTIES OF PEAT SOIL
NUR FATIHAH BINTI MU}TAMAD
A Final Year Project report submitted in partial fulfillments of the requirements for the award of the degree of Bachelor of Civil Engineering
Faculty of Civil Engineering & Earth Resources UNIVERSITI MALAYSIA PAHANG
JUNE 2013
VII
ABSTRACT
Soil stabilization has been extensively used for the improvement of peat soils, in enhancing
the shear strength and limiting the deformation behaviour. Cement is widely used as a
stabilizing materials for soils, but the increasing price is causing economic concerns among
practitioners and clients alike. The quest for alternative cheaper stabilizing agents is
therefore more urgent than before. Rice husk is a major agricultural waste in Malaysia and
the common disposal method of open burning has notoriously contributed to environmental
pollution. The possibility of admixing rice husks with cement for stabilizing soft soils could
be a solution to both problems. This study was aimed to investigate the effect of rice husk
on the compaction properties of peat soil. Laboratory experiment were carried out on a
stabilized peat soil to determine the optimum water content, maximum dry density of the
soil and waste for various mixes of rice husk. Peat soil samples were collected from
Kampung Tanah Putih, Pekan, Pahang. The stabilized specimens were prepared with the
peat soil admixed with various quantities of rice husk and water content, then compacted
using Standard Proctor Test. The specimens were observed to undergo reduction in
compressibility and increase in strength highlighting the great potential of rice husk as an
alternative soil stabilizer.
VIII
ABSTRAK
Penstabilan tanah telah digunakan secara meluas untuk memperbaiki tanah gambut,
meningkatkan kekuatan ricih dan menghadkan tingkah laku ubah bentuk. Simen digunakan
secara meluas sebagai bahan penstabilan untuk tanah, tetapi dengan kenaikan harga simen
yang semakin meningkat menyebabkan kebimbangan ekonomi dalam kalangan pelanggan.
Usaha untuk menstabilkan ejen penstabil yang lebih murah, satu alternatif telah dilakukan
untuk menghasilkan ejen yang lebih efektif. Sekam padi adalah sisa pertanian utama di
Malaysia dan kaedah pelupusan pembakaran terbuka telah meluas dan menyumbang
kepada pencemaran alam sekitar. Kemungkinan campuran sekarn padi dengan simen untuk
menstabilkan tanah lembut boleh menjadi penyelesaian kepada kedua-dua masalah. Kajian
mi bertujuan untuk mengkaji kesan sekam padi terhadap sifat pemadatan tanah gambut.
Eksperimen makmal telah dijalankan ke atas tanah gambut untuk menentukan kandungan
air optimum, ketumpatan kering maksimum tanah dan sisa untuk pelbagai campuran sekam
padi. Sampel tanah gambut telah diambil dari Kampung Tanah Putih, Pekan, Pahang.
Spesimen tanah gambut yang telah dikeringkan dicampur dengan pelbagai kuantiti sekam
padi dan kandungan air, kemudian dipadatkan menggunakan Ujian Proctor Standard.
Melalui pemerhatian, specimen menjalani pengurangan kebolehmampatan dan peningkatan
kekuatan yang menonjolkan potensi besar sekam padi sebagai penstabil tanah alternatif.
TABLE OF CONTENTS
Page
SUPERVISOR'S DECLARATION 11
STUDENT'S DECLARATION
ACKNOWLEDGEMENT V1
ABSTRACT Vi!
ABSTRAK viii
TABLE OF CONTENTS ix
LIST OF TABLES xiii
LIST OF FIGURES xiv
LIST OF GRAPH xv
LIST OF SYMBOLS xvii
LIST OF ABBREVIATIONS xviii
CHAPTER 1 INTRODUCTION
1.1 Background of study 1
1.1.l Peat Soil 2
1.1.2 Rice Husk 4
1.1.3 Soil Improvement 6
1.2 Problem Statement 7
1.3 Aim and Objective 7
1.4 Scope of Study 8
CHAPTER 2 LITERATURE REVIEW
2.1 Introduction
2.2 Available reagents for soil stabilization
ix
2.2.1 Cement and lime to be primary reagent 10
2.2.2 Rice husk ash as a secondary reagent 12
2.3 Effect of rice husk ash in soil stabilization 13
2.3.1 Soft soil stabilization with deep mixing 13
2.3.2 The mixing process 14
2.4 Effect of rice husk ash in soil stabilization 15
2.5 Engineering performance of rice husk ash 17
2.5.1 Structural Integrity 17
2.5.2 Corrosion performance 18
2.5.3 Effect of humidity 18
CHAPTER 3 METHODOLOGY
3.1 Flow of work 20
3.2 Sampling of soil 21
3.2.1 Location 21
3.2.2 Sampler 21
3.3 Basic Test 23
3.3.1 Introduction 23
3.3.2 Moisture content 23
3.3.3 Sieve analysis 25
3.3.4 Specific gravity 27
3.3.5 Fiber content 29
3.3.6 Atterberg limit 29
3.3.6.1 Liquid limit 31
3.3.6.2 Plastic limit 33
3.4 Major work 35
3.4.1 Compaction test of Peat Soil 35
3.4.2 Compaction test mixing with rice husk 37
x
A
3.5
Observation 38
CHAPTER 4 DISCUSSION OF RESULT
4.1 Natural water content 39
4.2 Specific gravity 40
4.3 Fiber content 41
4.4 Atterberg limit 41
4.4.1 Liquid limit 41
4.4.2 Plastic limit 44
4.4.3 Plasticity index 45
4.5 Compaction test 46
4.5.1 Compaction test of peat soil 47
4.5.1.1 Optimum water content 47
4.5.1.2 Zero air voids line 49
4.5.2 Compaction test of peat soil with rice husk 50
4.6 Sources and errors 61
CHAPTER 5 CONCLUSION AND RECOMMENDATION
5.1 Conclusion 62
5.2 Recommendation 63
REFERENCES 65
APPENDICES
A Natural Moisture Content Test 68
B Specific Gravity Test 69
C Fiber Content Test 70
LIST OF TABLES
Table no. Title Page
1 Water Contents of Peat Materials Expressed as Per cent 3
of Oven-Dry Weight, Per Cent of Wet Weight, and Per
Cent of Volume
2 Peat Classification by Proportion of Fibre Size Larger 3
Than 0.1 mm
3 Decomposition degree's level 4
4 World Production Rate for Rice Paddy and Risk Husk 5
5 Chemical Composition of Rice Husk 12
6 Physical properties of mortar at an age of 1 year 18
7 General range of specific gravity of soil 40
8 Plasticity index classification AASHTO T 90 46
9 Zero air voids 49
XIII
LIST OF FIGURES
Figure no. Title Page
1.1 Rice husk 5
2.1 Effect of the addition of lime on the plasticity properties 11
of London Clay
2.2(a) Expansive soil with different additives, influence to 16
swelling
2.2 (b) Expansive soil with different additives, influence to the 16
unconfined compression strength
3.1 Location of peat soil taken 21
3.2 Method of sampling 22
3.3 Peat soil 23
3.4 Weighing balance 24
3.5 Moisture sample 25
3.6 Pyknometer was filled with half to three-fourth of the 28
substance
3.7 The sample was placed in the vacuum 28
3.8 The pyknometer was filled with distilled water only 29
3.9 Drop Cone Penetration 30
3.10 Peat soil was thoroughly mixed with distilled water 31
3.11 Mixed peat soiL was transferred into cylindrical cup of 32
cone penetration
3.12 Placing the cylindrical cup on the base of cone 33
penetration
3.13 Rolling the sample 34
3.14 Field determination of plastic limit. 34
3.15 Standard proctor test machine 37
<iv
LIST OF GRAPH
Graph no. Title Page
4.1 Samplel 42
4.2 Sample 2 43
4.3 Sample 3 44
4.4 Dry Unit Weight versus Moisture content Graph 48
4.5 Initial Optimum Moisture Content 50
4.6 The relationship between dry unit weight and moisture 51
content of 6% corresponding with various rice husk
proportions
4.7 The relationship between dry unit weight and moisture 52
content of 8% corresponding with various rice husk
proportions
4.8 The relationship between dry unit weight and moisture 53
content of 15.5% corresponding with various rice husk
proportions
4.9 The relationship between dry unit weight and moisture 54
content of 23.4% corresponding with various rice husk
proportions
4.10 The relationship between dry unit weight and moisture 55
content of 27% corresponding with various rice husk
proportions
4.11 The relationship between dry unit weight and moisture 56
content corresponding with 2% of rice husk proportions
4.12 The relationship between dry unit weight and moisture 57
content corresponding with 4% of rice husk proportions
4.13 The relationship between dry unit weight and moisture 58
xv
content corresponding with 6% of rice husk proportions
4.14 'The relationship between dry unit weight and moisture 59
content corresponding with 8% of rice husk proportions
4.15 The relationship of dry unit weight versus moisture 60
content corresponding to various proportion of rice husk
xv
LIST OF SYMBOLS
W = mass of wet soil (in gram)
Wd mass of dry soil (in gram)
00 = moisture content (in %)
Pw = dry density of water (kg/M3)
Pd = dry density (kg/m3)
Yd = dry unit weight (kN/m3)
Va = air voids
Gs = specific gravity
xvii
LIST OF ABBREVIATION
RH =r rice husk
RHA rice husk ash
OMC = optimum moisture content
MDD = maximum dry density
STP = standard proctor test
ZAV = zero air voids
xviii
CHAPTER 1
INTRODUCTION
1.1 Background of study
Soil is known as the basic construction material. It is an important medium that
can be used as a base for roads and buildings. However, there is soil that may not
suitable for the construction due to its poor bearing capacity and higher compressibility
or has an excessive swelling in case of expansive soils. The topic of will discuss about
improving a soil by mixing it with a stabilizing agent using certain test. For example,
peat soil is not suitable for the construction purposes because the characteristics of peat
which is low in shear strength and easily compressed make it considered as unsuitable
for the structure to be built on it. Therefore, an innovation has to be made in order to
improve the strength of the peat soil. The soil can be improved by mixing it with a
binding agent such as cement, rice husk, and lime. The incorporating of this binder into
the soil with the addition of water, additional mixture or less, generally in situ, will
obtain a material which is homogenous enough to possess new properties. Compaction
is one of technique used to test the chemical similarities of the soil and the mixture, as
opposed to a mechanical treatment only. In this topic, rice husk is used as a stabilizing
agent. Rice husk is obtained from the rice which is extremely prevalent in East and
South-East Asia because of the rice production in this area.
I
2
1.1.1 Peat Soil
Peat is a natural soil which consists of high organic material because it is formed
from the accumulation of soil residues from some rot plants and disintegration of plant
and organic matters. Peat soil can be found in various places. In Malaysia, the area
covered by peat deposit was about 3 million hectares or 8% of the total area of
Malaysia. The peat soil samples for these studies were collected at Kampung Tanah
Putih, Pekan, Pahang.
Peat has high compressive deformation, high void ratio and water content. Peat
can be categorized in problematic soil because it has low shçar strength and high
compressibility and not suitable for the construction purposes. Besides that, peat soil is
an extremely soft soil and often referred to as problematic soil by engineers. It's soft
texture and compressibility lead to excessive settlement which is a very serious
problem. Since land are very expensive and very limited nowadays, therefore it is
essential to find an alternative to improve the strength of the soil.
The physical properties of peat soil can be seen through its color and texture. A
series of test is conducted in order to determine the physical properties of the natural
peat soil. The physical properties of peat include water content, specific density, bulk
density, fiber content, and decomposition degree. The water content of peat can be
measures. The humidity and the saturated soil water content in Sphagnum peat are the
highest, and they are least in herbaceous-woody peat (Hu Jinming & Ma Xuehui, 2003).
When the water contents were expressed on either an oven-dry or wet weight basis, all
the organic materials appeared to contain much more water than the mineral soil as
shown in table 1.
3
Table 1: Water Contents of Peat Materials Expressed as Per cent of Oven-Dry Weight,
Per Cent of Wet Weight, and Per Cent of Volume
Water content as per cent of
Material Bulk density Oven-dry Wet Volume
(g/cc) weight weight
Peat
Sphagnum moss 0.02 2000 95 40
Herbaceous 0.16 250 71 40
Well decomposed 0.24 167 62 40
Mineral soil
Barnes loam 1.29 31 24 40
D. H. Boelter Northern Conifer Laboratory, North Central Forest Experiment Station,
Forest Service, U.S. Department of Agriculture, Grand Rapids, Minnesota 55744, U.S.A.
Den Haan (29) stated that the specific gravity of organic peat is affected by the
organic constituents. For example, cellulose and lignin are having lower specific gravity
which is 1.58 and 1.40 respectively. This causes the reduction in specific gravity of
peat. Consequently, the specific gravity of the peat depends on the organic and fiber
constituents. For fibre content, the increasing decomposition decreases the content of
the particles or fibres larger than a designated size. Farnham and Finney (1965) have
arbitrarily selected fibre greater than 0.1 mm as a criterion for classification of peats.
Their designations are as shown in Table 2.
Table 2: Peat Classification by Proportion of Fibre Size Larger Than 0.1 mm
Portion of the total mass consisting of fibres Designation of material
larger than 0.1mm
Less than one third Sapric (the most decomposed peat)
One-third to two-third Hemic (intermediate stage of decomposition)
More than two-thirds Fibric (the least decomposed peat)
D. H. Boelter Northern Conifer Laboratory, North Central Forest Experiment Station, Forest
Service, U.S. Department of Agriculture, Grand Rapids, Minnesota 55744, U.S.A.
rd
The decomposition degree of peat is the proportion of the matter which has lost its
cellular structure due to the decomposition of plant residues. Decomposition degree is
usually expressed as a percentage. Table 3 shows the three level of the decomposition
degree of peat soil.
Table 3: Decomposition Degree's Level, (Hu Jinming & Ma Xuehui, 2003).
Lowly decomposed peat Less than 20%
Moderately decomposed peat 20%-40%
Highly decomposed peat Higher than 40%
1.1.2 Rice Husk
Rice husk is the shell produced during dehusking of paddy. Rice is a heavy
staple in the world market since it is the primary source of food for billions of people
around the world. It has become the second largest amount of any grain produced in the
world. Rice can easily grow in tropical regions on any type of terrain. It is well-suited to
countries and regions with low labor cost and high rainfall, as it is very labor-intensive
to cultivate and requires plenty of water for cultivation (Wikipedia, Rice). The table
shown in Table 4 is the significant the amount of rice cultivated and the amount of rice
husk accumulated across the world.
Figure 1.1: Rice Husk
Table 4: World Production Rate for Rice Paddy and Risk Husk (Million Metric
Tons), courtesy of Hwang & Chandra
Country Rice Paddy Rice Husk
Bangladesh 27 5.4
Brazil 9 1.8
Burma 13 2.6
China 180 36.0
India 110 22.0
Indonesia 45 9.0
Japan 13 2.6
Korea 9 1.8
Philippines 9 1.8
Taiwan 14 2.8
Thailand 20 4.0
US 7 1.4
Vietnam 18 3.6
Others 26 5.2
Total 500 100
5
From the table, we can see that the production of rice paddy is around 500
million tons and 100 million tons of rice husks are produced, Hwang (185).
Furthermore, rice husk took a very long period to decompose and not appropriate for
composting or manure due to its low nutritional value. Therefore, the disposal of rise
husk has become important issue in those countries which cultivate large quantities of
rice. There were 100 million tons produced globally and this situation will begin to
impact the environment if it not disposed properly. Rice husk can be useful for many
things. One of the effective methods that can be used to rid planet from rice husk is by
using it as a binder or a stabilizing agent or use it to fuel kilns.
1.1.3 Soil Improvement
In order to propose a construction on any land-based structure, the foundation
has to be strong to support the entire structure. The soil around the foundation plays an
important role to make sure that the foundation is strong enough for that purpose.
Therefore, we need to study and gain knowledge about the properties of the soil and
investigate the factors which affect their behavior. A soil improvement process must be
done in order to achi0e the required properties of soil that needed for the construction
work. In this research, the soil improvement has been investigated by mixing the peat
soil with rice husk under compaction test. The improvement in the compressibility
parameter and comparative study have been carried out using different percentage and
proportion of moisture content and rice husk. The addition of rice husk to the soil will
enhance the workability and strength of the soil. Keeping in view of environmental
consideration, energy conservation, and economy, the using of rice husk will help the
disposal of rice husk properly.
7
1.2 Problem Statement
Nowadays, there is a high demand in construction purposes and the building
construction grows rapidly. Construction work requires soil as a base and important
foundation to enable the construction to construct. However, not all soil suitable for the
purposes because there is a soil that has been classified as weak soil such as peat soil.
Peat is known as one of the most problematic soil in the world. It can pose serious
problem in the construction industry due to its consolidation settlement. In future, the
soil will be limited and the construction work cannot be done. Therefore, we have to
treat and find an alternatives way to replaced the soil by improving the soil properties.
1.3 Aim and Objectives
The main objective of this research is to investigate the effect of rice husk in the
compaction of peat soil. Apart from that, the index properties such as natural water
content, fiber content, liquid limit, atterberg limit, specific gravity and density of peat
soil were obtained to establish suitable correlation.
The specific objectives of this research are:
1) To determine the optimum water content of the peat soil and waste for various
mixes of rice husk.
2) To determine the maximum dry density of the peat soil and waste for various
mixes of rice husk.
3) To determine the optimum peat soil and waste mix of rice husk which gives the
maximum compaction performance.
8
1.4 Scope of Study
In this research, peat soil will be used. The peat sample was tropical peat which
obtained from area of Kampung Tanah Putih Pekan, Pahang. There are two tests that
will be conducted in this research, which is minor test and major test. The minor test
includes the basic engineering properties of peat samples such as moisture content,
liquid limit, fiber content, specific gravity, and dry density. The major test in this
research will be compaction test by using standard proctor test equipment. Here, the soil
will be mixed with rice husk at various proportions varying from 0%, 2%, 4%, 6% and
8%. The rice husk was obtained from Bernas Factory at Bagan Serai, Perak.
CHAPTER 2
LITERATURE REVIEW
2.1 Introduction
The main topic of literature review is the review of compaction behavior of peat
soil mix with waste material such as rice husk. The properties of rice husk was stated in
the previous chapter. In this chapter, some review of the current work of the experiment
will be discussed. Soil stabilization using rice husk ash and lime has been more
attractive recently due to its promising results compared to other siliceous sources.
Overview about the methods and the basis of the rice husk ash utilization in this
application will be presented in this section. The common criteria and methods to
evaluate the activity of the rice husk ash will also be introduced and these will be the
basis for the evaluation of the rice husk ash in the next section.
2.2 Available Reagents for Soil Stabilization
Soil stabilization mentioned in the overview is the alteration of the current
properties of the soil to meet the specified engineering requirements, and using
chemical reagents is one of the main techniques. The mechanism which helps to
stabilize the soil is that the reagents create matrix within the soil mass, hence particles
are bonded together and the overall strength is increased while water absdrption is
reduced.
10
The matrix can be created by physical or chemical reactions. The most common
method of physical reaction for soil stabilization is bitumen in road construction. The
bitumen is made to be more fluid before operation, and it will come back to the viscous
semi-solid state inside the soil mass by temperature reduction and evaporation. By this
way, the soil particles are fixed in the bitumen matrix, nevertheless the bonding is
relatively weak.
Chemical reactions for soil stabilization can be either the reaction between
different reagents so that the matrix will cover the soil particles or the reactions between
the reagents with soil. The precipitation of calcium silicate from sodium silicate and
calcium chloride is an example for the case which the soil does not join into the reaction
but sinks into the product of the reaction.
When the soil joins into the reaction, hydrated lime is the typical reagent for this
case because of its intermediate affect in drying the soil and the pozzolanic reaction
with some clay minerals for long-term shear strength development of the soil mass.
Available reagents for soil stabilization are categorized into two groups. The
primary stabilizing reagents are the ones which they themselves can stabilize the soil.
So the reagents mentioned above, which are bitumen and lime are in this group. The
secondary stabilizing reagents need the lime or cement to be activated, and these are the
blast furnace slag or the pozzolanas such as fly ash or rice husk ash.
2.2.1. Cement and Lime To Be The Primary Reagent
The primary stabilizing reagent which are cement and lime are very well known
because they can work with wide range types of soil in various foundation conditions.
The main effect of the additives is modifying both the physical and chemical properties
of the soil in such a way that the strength, volume stability, durability and permeability
are improved.
11
*
Liquidiimit
I 4
- - -
V
Zoe,*
Plastic limit
I - Plasiticlty 'Index
Lime content (6)
Figure 2.1: Effect of the addition of lime on the plasticity properties of London Clay,
(Sherwood 1993)
When lime is added into the soil, the improvement mechanism can be separated
into two phases. With the present of clay minerals, the clay anion is immediately
isolated by the calcium cation Ca 2 in the lime from other weaker cations existing in the
soil, hence the soil texture is the changed. This ion exchange leads to flocculation in the
first phase and it dramatically reduces the plasticity of the soil as seen in Figure 2.1
(Sherwood 1993). For the clay whose water content is 35% and plastic limit is 25%, it is
plasticity and not preferred for construction. But by adding 2% of lime, the plastic limit
is upgraded to be 40%, consequently makes the soil be dry and possibly ready for
construction purposes.
The appearance of hydroxyl anion from lime increases the pH to about 12.4 and
helps to dissolve the silica existing in soil, hence the pozzolanic reaction happens.
Depends .on the mineral components of the soil that this stabilized matrix is strong or
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