NUR FATIHAH BINTI MU}TAMAD

PERPUSTAKAAN UMP

111111111111111111111111111111111111111111111 0000092680

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

XII

D Atterberg Limit Test

71

E Compaction test 75

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



proportions


content of 15.5% corresponding with various rice husk

proportions


content of 23.4% corresponding with various rice husk

proportions



proportions


content corresponding with 2% of rice husk proportions




xv


4.14 'The relationship between dry unit weight and moisture 59


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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NUR FATIHAH BINTI MU}TAMAD