soil cbr improvement by fly ash with relation to pavement …
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SOIL CBR IMPROVEMENT BY FLY ASH WITH RELATION TO PAVEMENT
THICKNESS, CASE STUDY IN LEPAR HILIR, KUANTAN
HASHIM BIN AHMAD
A thesis submitted in partial fulfillment of the requirements for the award of the
degree of Bachelor of Civil Engineering
Faculty of Civil Engineering & Earth Resources
Universiti Malaysia Pahang
NOVEMBER 2010
vi
MZWRMWI
Increasing rate of traffic load will influence the highway construction
technology revolution. It is because of continuation rapid growing in economic
activities and technology. Therefore it is necessary to produce high durability and
serviceability of road structure as the main of an objective. Subgrade layer is the most
important component which influences the stability of the road structure. The good
subgrade can influence the thickness of road structure, strength and the cost in
construction stage. California Bearing Ratio (CBR) is a commonly used indirect
method to assess the stiffness modulus and shear strength of subgrade in pavement
design work. Basically, subgrade must be stable in performance to carried load in any
weather. Method that used in strengthening the subgrade structure is soil stabilization.
The method used in this study is adding with fly ash as admixture to improve CBR
value. Hence, the thickness of pavement structure can be decrease when CBR value is
increase. As a result, the cost of construction a road pavement will decrease and more
economically.
TABLE OF CONTENTS
CHAPTER TITLE PAGE
DECLARATION
DEDICATION iv
ACKNOWLEDGEMENT v
ABSTRACT vi
TABLES OF CONTENT vii
LIST OF FIGURES xi
LIST OF TABLES xii
LIST OF SYMBOLS AND ABBREVIATIONS xiii
LIST OF APPENDICES xiv
1 INTRODUCTION
1.1 Introduction 1
1.2 Problem Statement 4
1.3 Objectives of the Study 5
1.4 Scope of Study 5
1.5 Significant of Study 6
vii
2
LITERATURE REVIEW
2.1 Pavement Components and Materials 7
2.1.1 Pavement Surfacing 7
2.1.2 Road-Base 8
2.1.3 Sub-Base 8
2.1.4 Sub-Grade 9
2.2 Particles Size Analysis 9
2.3 Atterberg Limits 11
2.4 Cohesive Soil 13
2.5 Shear Strength Of Cohesive Soil 14
2.6 California Bearing Ratio Test 16
2.6.1 Applications of CBR 17
2.6.2 Apparatus 18
2.6.3 Road Pavement Design Manuals and 20
Publications Using CBR Values
2.7 Fly Ash 21
3 METHODOLOGY
3.1 Introduction 23
3.2 Flow Chart 23
3.3 Collection of Samples 25
3.4 Soil Preliminary Testing 26
3.5 Soil Selection 27
3.6 Preparation of Remoulded Sampling 27
3.6.1 Dynamic Compaction 28
3.6.2 Static Compaction 28
3.7 Laboratory Soil Testing 28
3.8 Testing Method 29
3.8.1 Particles Size Analysis 29
3.8.2 Moisture Content 30
viii
4
3.8.3 Liquid Limit of The Soil 31
3.8.4 Plastic Limit and Plasticity Index 33
3.8.5 The Shrinkage Factors of Soils 35
3.8.6 Compaction Test 36
3.8.7 California Bearing Ratio (CBR) 38
3.9 Pavement Design Standard 40
3.9.1 Design Period 40
3.9.2 Traffic Estimation 40
3.9.3 Total Equivalent Standard Axle Load 41
(ESAL) Estimation
3.9.4 Mean Subgrade CBR Estimation 41
3.9.5 Pavement Design 42
3.9.6 Cross Section of a Flexible Pavement 46
Structural Layers
RESULT AND ANALYSIS
4.1 Introduction 47
4.2 Particles Size Analysis 47
4.3 Atterberg Limit 50
4.4 Compaction Test 51
4.5 California Bearing Ratio 51
4.6 Pavement Design 56
4.7 Pavement Costing 60
A
5 CONCLUSION AND RECOMMENDATIONS
5.1 Conclusion
5.2 Recommendations
REFERENCES
67
APPENDIX A
68
APPENDIX B
70
APPENDIX C
74
APPENDIX D
78
LIST OF FIGURES
xi
FIGURE NO. TITLE
1.1 Typical section of flexible pavement
2.1 Typical particle size distribution curves
2.2 Consistency relationship
2.3 Liquid and plastic for various soils
2.4 CBR apparatus
3.1 Flow chart of the study
3.2 Map of Gambang shows the location where samples
are taken
3.3 Taking the samples at Felda Lepar Hilir
3.4 Thickness design Nomograph
3.5 Cross-section of a Flexible Pavement
4.1 Grain size distribution curve for sample no. 1
4.2 Grain size distribution curve for sample no. 2
4.3 CBR test graph for sample no. 1 (plain)
4.4 CBR test graph for sample no. 1 (4% fly ash)
4.5 CBR test graph for sample no. 1 (8% fly ash)
4.6 CBR test graph for sample no. 2 (plain)
4.7 CBR test graph for sample no. 2 (4% fly ash)
4.8 CBR test graph for sample no. 2 (8% fly ash)
4.9 Thickness Design Nomograph
4.10 Cross-section of a flexible pavement
4.11 Thickness of each layer with materials used in
proposed road
PAGE
2
10
11
13
19
24
25
26
43
46
48
48
52
52
53
54
54
55
57
59
60
LIST OF TABLES
TABLE NO. TITLE PAGE
2.1 CBR's for commonly subgrade conditions 20
2.2 The physical properties and chemical composition of 22
fly ashes
3.1 Default values for ESAL 40
3.2 Pavement Structural Layer Coefficients 44
3.3 Minimum Layer of Pavement Thickness 45
3.4 Standard & Constructed Pavement Layer Thickness 45
3.5 Minimum Thickness of Bituminous Layer 45
4.1 Group classification of soil according to AASHTO 49
standard
4.2 Result of Atterberg Limit test 50
4.3 Result of Atterberg compaction test 51
4.4 Result of CBR test for sample no. 1 51
4.5 Result of CBR test for sample no. 2 53
4.6 Coefficient and thickness of materials by layer 58
xl'
LIST OF SYMBOLS AND ABBREVIATIONS
AASHTO - American Association of State Highway and Transportation
Officials
ADT - Average daily traffic
ASTM - American Society for Testing and Materials
CBR - California Bearing Ratio
CD - Consolidated drained
CU - Consolidated undrained
CU' - Consolidated undrained with pore water pressure measurements
ef - equivalence factor
ESAL - Total Equivalent Standard Axle Load
JKR - Jabatan Kerja Raya
LL - Liquid limit
n - Design period (years)
Li op - Optimum moisture content
Pc - Percentage of commercial vehicles
P1 - Plastic index
PL - Plastic limit
r - Estimate the rate of annual traffic growth
SSA - specific surface area
TA - Equivalent thickness
UU - Unconsolidated undrained
V - The total number of commercial vehicles
V0 - The initial yearly commercial vehicle traffic
Yd.max - Maximum dry density
KUTA
LIST OF APPENDICES
APPENDIX TITLE PAGE
A Data for particles size analysis 68
B Data for Atterberg limit test
70
C Data for compaction test 74
D Data for California Bearing Ratio (CBR) test 78
CHAPTER 1
INTRODUCTION
1.1 Introduction
Soil stabilization is the alteration of soil properties to improve the engineering
performance of soils. The properties most often altered are density, water content,
plasticity and strength. Modification of soil properties is the temporary enhancement
of subgrade stability to expedite construction. Soils must be compacted to their
maximum practical density to provide a firm base for overlying structures. For soils to
be compacted the moisture content must be controlled because of the -relationship
between soil density and moisture content. If the soil to be compacted is either to wet
or too dry, the moisture content must be adjusted to near optimum to achieve
maximum density. If a soil is too dry, moisture is simply added. If a soil is too wet, the
moisture content of the soil must be lowered.
A highway is a main road for travel by the public between important
destinations, such as cities, large towns, and states. Highway designs vary widely and
can range from a two-lane road without margins to a multi-lane, grade-separated
expressway, freeway, or motorway. Daily human activity is depending on the
highways. Highways are the most important part of the automobile industry. If there
were no roads or highways there would be any need for automobiles. Highways can
be large or small in the number of lanes available in each direction. Highways can
consist of tunnels, bridges and even ferries.
Geotechnical engineering has been critically to highway construction since
engineers realized that successful civil works depended on the strength and integrity
of the foundation material. Road design and construction over soft ground especially
over very soft and marine deposits are interesting engineering challenges to engineers
especially at the approaches to bridges and culverts. Many geotechnical options are
available for engineers' consideration. The soils are very soft and soft deposits of river
alluvium and marine deposits common in Southeast Asia. The river alluvium and
marine deposits normally consists of clay, silt clay and occasionally with intermittent
of sand lenses especially near a major river mouth and delta. The marine deposits in
Malaysia are encountered along the coast of the Peninsular, where they up to 20km in
width. Cross-section of a typical flexible pavement is illustrated in Figure 1.1.
IM "WrIll 3 101 [9161919) *1
MOOSENME
SURFACING
Figure 1.1: Typical section of flexible pavement (Rahim, 2007)
Pavement evaluation technique plays very important rules in determining the
flexible pavement condition. The choice of equipment, information quality
requirement, accuracy, method of analysis and techniques uses will contribute to the
accuracy of the findings, thus will also influence the decision in determining the
rehabilitation methods; Initial assessment of the physicalpavement condition can be
carried out through visual assessment on the flexible surface condition and drainage
assessment. Detailed assessment including sampling and fields test can be scheduled
as and when required depending on the nature of the failures.
Embankment design of roads needs to satisfy two important requirements
among others; the stability and settlement. The short term stability for embankment
over soft clay is always more critically than long term simply because the subsoil
consolidates with time under loading and the strength increases. In design, it is very
important to check for the stability of the embankment with consideration for different
potential failure surfaces namely circular and noncircular. It is also necessary to
evaluate both the magnitude and rate of settlement of the subsoil supporting the
embankment when designing the embankment so that the settlement in long term will
not influence the serviceability and safety of the embankment.
In many sub-tropical and tropical and regions of the world, marl soils (marls)
and lime or cement stabilization of marl soils are used as a convenient and expedient
means of developing foundation base courses and inexpensive wearing courses for
transport purposes. The failure of many of these natural and stabilized marls to
perform their function has been reported. Mechanical factors commonly used to
explain the causes of the foundation failures are unsatisfactory and have not been
accepted. This study uses physicochemical (reaction) factors to explain the general
basic causes of the deterioration of support capability for. these types of soils.
The presence of palygorskite and sepiolite in marl soil provides it with some
very unique features in its natural state, particularly when it is stabilized with lime or
cement. The formation of an expansive mineral, ettringite, as a transformation product
of palygorskite increases the swelling potential of the stabilized soil. A set of physic
chemical and mechanical experiments, which include slake durability, specific surface
area measurement (SSA), California bearing ratio (CBR), Atterberg limits testing
were performed.
4
1.2 Problem statement
Nowadays in Malaysia, there are so many constructions of highways. Since
highways also involve foundation, these means geotechnical aspects are also
important in the highway construction. Shear strength parameters are always
associated with the bearing capacity of the soil. However for highways engineers, they
always prefer to use CBR test to determine the suitable strength for designing road
pavement. In order to make the construction of highway is economical the engineer
must design the best thickness from lower layer of subgrade . to surface course.
The cost of materials is decrease from top to bottom which is from surface
coarse to subgrade. This means the engineer must design the less thickness for surface
coarse layer and more depth for subgrade layer. So that this study was carried out as to
find the improvement of CBR value in soil by using fly ash with relation to reduce
pavement thickness.
These are the real culprits of surface deterioration; the ultra-violet rays of the
hot sun cause oxidation and the aggregate material to protrude from the surface,
making the pavement rough. The surface becomes brittle, cracks develop and the
pavement deteriorates. Gasoline, oils, and fuels dissolve asphalt causing it to soften or
even worse fail. Water in the underlying soil may make it unable to resist even
ordinary loads. As the soil yields way, the pavement begins to crack and deteriorate.
As time goes by, freeze-thaw cycles widen the cracks, letting in even more water and
the problem continues to worsen at an accelerated pace.
J
1.3 Objectives of the study
The study is carried for the following objectives;
i. To determine the engineering soil properties in Lepar Hilir;
ii. To determine the optimum content of fly ash in soil that improve CBR
value;
iii. To determine the suitable thickness of pavement after added by fly ash,
based on JKR standard and cost of pavement.
1.4 Scope of study
The sample used in this research only involved soils from Lepar's areas. The
samples for this research are based on compaction sample. This study is done based
on the specified scope in order to ensure the precision of the study area. It is also done
in order to achieve the objective of the study. Therefore, its limit has been specific
scopes which are:
a) Location of site
The location of this study is limited in areas of Lepar which are soils taken
from Felda Lepar Hilir that near to main road and from Felda Lepar Hilir 2.
b) Scope of work
In this study, the aim is to measure the value of CBR and its effect to
pavement thickness. After adding fly ash as an admixtures in the soil samples,
test the sample to get its properties such Atterberg limit and maximum dry
density.
U
1.5 Significant of study
From this study, this research will narrow the gap of understanding on soil
strength for the geotechnical and highway engineer. Since these two different
disciplines in civil engineering have their own understanding on the use of the soil
parameters in design, it is appropriate some basis for interpretation of CBR in terms of
shear strength parameters and vice versa.
CHAPTER 2
LITERATURE REVIEW
2.1 Pavement components and materials
A flexible pavement is a layers consisting of the following components;
a) Pavement surfacing
b) Road base
c) Sub-base
d) Sub grade
2.1.1 Pavement surfacing
The surfacing is the upper layer of the pavement, which provides the following
functions;
a) To provide an even, non-skidding and good riding quality surface
b) To resist wear and shearing stress imposed by traffic
c) To prevent water from penetrating into the underlying pavement layers
o
d) To be capable of surfacing a large number of repeating loading without
distress
e) To withstand adverse environment condition
Bituminous surfacing consists of crushed mixed aggregate, bitumen and filler
and the most common type of plant mixed surfacing are asphaltic concrete or
bituminous macadam. Thick bituminous surfacing can provide additional strength to
the existing pavement structure but the thin resurfacing, which is less than 50mm
thickness does not give direct additional strength. It merely protects the pavement
from water infiltrate and improve skid resistant.
2.1.2 Road-base
The road-base is the main structural layer of the pavement, which spread the
load from heavy vehicles thus protecting the underlying layer. The function of this
layer is to reduce the compressive stress in the sub-grade and sub-base to an
acceptable level to avoid cracking on surfacing layer. The road-base is commonly
constructed using unbound crushed aggregate as this material is readily available in
most area in Malaysia.
2.1.3 Sub-base
The sub-base is the secondary load-spreading layer underlying the road-base.
The materials used for this layer is normally consists of lower grade granular materials
as compared to the road-base materials. This layer also serves as a separating layer
preventing contamination of the road-base by the sub-grade materials as well as a
drainage layer. Sand and laterites are commonly used as the sub-base and are easily
available.
2.1.4 Sub-grade
Sub-grade is referred to the soil under the pavement within a depth of
approximately 1.0 mater below the sub-grade. It can be either be natural undisturbed
soil or compacted soil obtained from elsewhere and placed as filled materials. The
strength of this layer is important in determining the thickness of the upper layers.
2.2 Particles size analysis
Particles size analysis is commonly known as sieving test or mechanical test.
This test can determine the range of size of particles in the soil sample and the
percentage of particles in each of the sizes between the maximum and minimum. In
this test, a series of standard test sieves by having different-size- opening are stacked
with the larger with the larger sized over the smaller. The soil sample in the sieving
aperture is vibrated mechanically with the minimum period of 10 minutes. In each
sieving apertures, the mass of retaining soil is determined and the percentage of mass
passing of each sieve id computed. A grading curved is plotted on a semi logarithmic
coordinates, where sieving aperture sizes is on horizontal logarithmic scale and the
percentage of soil mass passing is on vertical arithmetic scale. Normally, the grading
curves are obtained from dry and wet sieving methods.
10
The grading curves will render the characteristic of the soil samples, which
range the size particles from ëoarse-grained to fine grained sizes. The flatter the
distribution curve indicated the larger range the particles in the soils; the steeper curve
implies the smaller the size range.
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Figure 2.1: Typical particle size distribution curves (Jeremy, 2006)
Well-graded soil is a distribution of over relatively large range of sizes, which
no excess or deficiency of particles in any size range and no lacking of intermediate
size. Poorly graded is cited to the soil if a high proportion of the particles have narrow
limit (a uniform soil) or if of both large and small sizes are present but with a
relatively low proportion of particles of intermediate size (a gap-graded soil).
I
2.3 Atterberg Limits
Soil will display the properties of plasticity and cohesiveness if the containing
fines (silt and clay). This property depends on amount and mineralogy of the fines and
amount of water present, or moisture content. In remoulded state, the consistency of
clay varies in proportion to the water content, at high water content, the soil will be in
liquid state; at moderate water content, the volume of soil will be decrease and still
show the properties of a plastic; at still lesser water content, the soil becomes on semi-
solid state and finally as a solid.
JoltJmO
Liqu id
Semi V. V^
Solid Solid
SL PL LL Wa t ratnt
VV Water A ____
____ _____
S ) S) s s 3 0 Soil Solids
S,<100%P S100%
kWaIr Content Ueceasin -
I . - I I W -0 W = W w = w w = W E, VV > WE,
Figure 2.2: Consistency relationship (Jeremy, 2006)
12
There are three arbitraries limits which corresponding to changing moisture
content:
Liquid Limit (LL) = Water content at which the stops to be liquid and becomes
plastics
Plastics Limit (PL) = Water content at which the stops to be plastics and becomes a
semi-solid
Shrinkage Limit (SL) Water content at which drying-shrinkage at constant stress
Plastics Index (Ii,) is defined as the soil is in plastic . form in the range of water
content between PL and LL.
I = LL - PL
The greater the plastic index, the higher will be the interaction and attraction between
the soil particles and also greater the plasticity of the soil.
Since the plasticity of fines (silt and slay) gives significant impact in soil
engineering properties, such as shear strength and compressibility, the transition from
one state to the next physical state of soil characteristics at given moisture content,
must be identified carefully in order to produce accurate and reliable results.
Column chart as Table 2.1 was developed in United Kingdom and both liquid
and plastic could be determined from graph. Plastic index (Ii,) can serves as an
additional means to soil identification, citing Sandy loam, Sandy-clay loam, Silt, Silt
clay and clay as examples.
13
100
80
60
ff40 °- 20
0clays Liquid limit
— Plastic limit \_____
Plasticity index
Figure 2.3: Liquid and plastic for various soils (Jeremy, 2006)
2.4 Cohesive Soil
Cohesive soil is type of soil that small soil particles forms an d has higher water
content. Cohesive soils consist of silts, clay and organic materials. Clay is low
strength and high compressibility and many are sensitive. The clay is consisting of
several minerals. Silica Tetrahedron and Alumina Octahedrons are the basic units to
weathering and decomposition of feldspars, such as Orthoclase and Plagioclase and
compose the clay minerals. The size of clay is very small, which is less than 2.im and
electrochemically very active. Clay minerals are produces mainly from the chemical
some Mica.
-
—
INS -
F,I I,__ lm Nflf
14
2.5 Shear Strength of Cohesive Soil
Soil can be classified as being either non plastic or plastic. Shear strength of
non plastic soils known as cohesion less soils or granular soils. Shear strength of
plastic soils, known as cohesive soils. Cohesive soils have fines, which are silt and
clay size particles that give the soil a plasticity or ability to be moulded and rolled.
Typical types of cohesive soils are silts and clays. The shear strength of cohesive soil
is much more complicated than the shear strength of cohesion less soils. Also, in
general the shear strength of cohesive soil tends to be lower than the shear strength of
cohesion less soils. As s result, more shear induced failures occurs in cohesive soils,
such as clays, than in cohesion less soils.
The strength of cohesive soil can generally be divided into four broad groups:
1. Undrained shear strength
This is also known as the shear strength based on a total stress analysis. The
purpose of these laboratory tests is to obtain either the undrained shear strength
analysis. The purpose of these laboratory tests is to obtain either the undrained
shear strength of the soil or the failure envelope in terms of total stresses.
These types of shear strength tests are often referred to undrained shear
strength tests because there is no change in water content of the soil during
shear portion of the test.
2. Drained shear strength
This is also known as the shear strength of soil based on an effective stress
analysis. The purpose of these laboratory tests is to obtain the effective shear
strength of the based on the failure envelope in terms of effective stress. These