ABSTRACT
Proper disposal of waste has been a challenge in the world today due to its effect on the ecosystem, as the gases emitted to the atmosphere poses a huge problem to the ozone layer. In a bid to remediate this, several techniques have been developed which includes proper waste recycling and incineration methods. Studies have shown that Sawdust, a waste material from wood processing industries in its Ash form poses a certain percentage of cementitious properties, which can be used in re-engineering and improving the strength properties of problematic lateritic soils and hence this study is aimed at treating weak lateritic soil materials using sawdust ash and developing a mathematical model to predict the Unconfined Compressive Strength (UCS) and California Bearing Ratio (CBR) of the lateritic soil treated with sawdust ash for sustainable earthwork constructions. The geotechnical properties of the soil were examined, and the soil and saw dust ash were characterised using Scanning Electron Microscopy (SEM) and X-Ray Diffraction (XRD). The lateritic soil was stabilized using percentage saw dust ash of 0%, 2%, 4%, 8% and 10% and the UCS and CBR of the stabilized soil were examined. Multi-linear regression of the UCS and CBR of the stabilized soil was investigated using the historical design of Response Surface Methodology (RSM) in design expert software. The results indicated that the lateritic soil contains SiO2, Al2O3, Fe2O3, CaO, MgO, Na2O, K2O, SO2, P2O5 and MnO. The SEM result for the lateritic soil showed clumped particles made of Al2O3, SiO2, and Fe2O3, while the saw dust ash SEM indicated a brittle surface with a high surface area. The XRD patterns of the unstabilized of lateritic soil and saw dust ash indicated that quartz (Qz) is the predominant mineral. The highest CBR of 15.3% was achieved at 4% SDA content. The measure of the unconfined compressive strength cured after 7, 14 and 28days showed that an increase in the SDA increased the UCS of the soil with maximum value of 195.60 kN/m3, 197.92 kN/m3 and 202.48 kN/m3 UCS obtained at 7 days, 14 days and 28 days curing respectively. The multiple linear regression for the stabilization of the lateritic soil gave linear regression models with R-squared of 0.991852 with adjusted R-Squared of 0.97963 for CBR and an R-squared of 0.989856 with an adjusted R-Squared of 0.97464 for UCS. It was recommended that cement requirement for road work could be substantially reduced to an optimum level and partially replaced by sawdust ash for road work to reduce the cost of materials.
TABLE
OF CONTENTS
Title Page i
Declaration ii
Certification iii
Dedication iv
Acknowledgment v
Table of Content vi
List of Tables ix
List of Figures x
List of Plates xi
Abstract xii
CHAPTER
1: INTRODUCTION
1.1 Background of
Study 1
1.2 Statement of
Problem 2
1.3 Aim and
Objectives 3
1.4 Scope of Study 4
1.5 Significance
of Study 4
1.6 Limitations of
Study 5
CHAPTER
2: LITERATURE REVIEW
2.1 Soil
Stabilization using Additives 6
2.1.1 Soil
stabilization using sawdust ash 6
2.1.2 Soil
stabilization using rice husk ash 10
2.1.3 Soil
stabilization using other chemical and agro-industrial waste modifiers 12
2.2 Material
Characterization Test 16
2.2.1 Scanning
electron microscopy (SEM) test 16
2.2.2 X-ray
diffraction (XRD) test 18
2.3 Multiple
Linear Regression Analysis (MLR) 19
2.3.1 Mathematical
derivation of MLR 21
2.3.2 Application
of MLR in civil engineering 22
2.4 Influence on
the United Nations SDG 23
CHAPTER
3: MATERIAL AND METHODS
3.1 Materials 26
3.1.1 Preparation
of sawdust ash 26
3.2 Methods 27
3.2.1 Moisture
content test 27
3.2.2 Mechanical
analysis (sieve analysis) test 28
3.2.3 Atterberg
limits 30
3.2.4 Specific
gravity of solids 34
3.2.5 Compaction
test 35
3.2.6 CBR test
(un-soaked procedure) 37
3.2.7 Unconfined
compression strength (UCS) 38
3.3
Characterization Test 41
3.3.1 X-ray
diffraction test procedure 41
3.3.2 Scanning
electron microscopy test procedure 43
CHAPTER
4: RESULTS AND DISCUSSION
4.1 Results 46
4.1.1 Geotechnical
properties of the unstabilized lateritic soil 46
4.1.2 Properties
of the sawdust ash 47
4.1.3 Geotechnical
properties of the stabilized lateritic soil 48
4.1.4 Unconfined
compressive strength 48
4.1.5 California
bearing ratio 49
4.1.6 Data for the
prediction of the UCS and CBR of sawdust stabilized lateritic soil 49
4.2 Discussion 50
4.2.1 Geotechnical
properties of the lateritic soil 50
4.2.2 Characterization
of the raw materials 51
4.2.2.1 Chemical
composition of sawdust ash 51
4.2.2.2 Scanning
electron microscopy (SEM) analysis 51
4.2.2.3 X-ray
diffraction (XRD) analysis 53
4.2.3 Geotechnical
properties of the stabilized lateritic soil 55
4.2.3.1 Sieve
analysis 55
4.2.3.2 Specific
gravity 56
4.2.3.3 Atterberg
limits test 57
4.2.3.4 Compaction
test result 58
4.2.3.5 Characterization
of the stabilized lateritic soil 61
4.2.4 Strength
characteristics of the stabilized lateritic soil 62
4.2.4.1 California
bearing ratio (CBR) 62
4.2.4.2 Unconfined
compressive strength (UCS) 64
4.2.5 Multiple
linear regression 66
4.2.5.1 Analysis
of variance (ANOVA) for the california bearing ratio (CBR) 67
4.2.5.2 Analysis
of variance (ANOVA) for the unconfined compressive strength (UCS) 69
CHAPTER
5: CONCLUSION AND RECOMMENDATION
5.1 Summary 71
5.2 Recommendation 72
5.3 Contribution
to Knowledge 73
REFERENCES
APPENDIX
LIST
OF TABLES
4.1: Engineering
Properties of Lateritic Soil 46
4.2: Chemical
Composition of Sawdust Ash 47
4.3:
Summary of Geotechnical Properties of the Soil – SDA Blend 48
4.4: Actual and predicted values of the CBR and UCS
for the stabilized soil 49
4.5: ANOVA for
California Bearing Ratio (CBR) 68
4.6: ANOVA for
Unconfined Compressive Strength (UCS) 69
LIST
OF FIGURES
2.1: Schematic Diagram
of a Scanning Electron Microscope 17
3.1: Atterberg
Plasticity Chart 34
3.2: Principles of
X-ray Diffraction Test 41
3.3: XRD
Spectrometer 42
4.1: XRD Plot of
the Unstabilized Lateritic Soil 53
4.2: XRD Plot of
the Sawdust Ash 54
4.3: Particle Size Distribution of the Lateritic
Soil 55
4.4: Comparison of Specific Gravity with Varying Proportions of SDA 56
4:5:
Comparison of the Atterberg limits at different percentage of SDA 57
4.6: Variation of the Maximum Dry Density (MDD) and
proportions of SDA 59
4.7: Variation of OMC with different proportions of
SDA content 60
4.8: XRD plot for the stabilized lateritic soil 62
4.9:
Variation of CBR with addition of different percentage of saw dust ash 63
4.10:
Variation of UCS stabilized with saw dust ash at different curing days 65
4.11: Plot for the predicted versus actual values of the (a) CBR (b) UCS 67
LIST
OF PLATES
3.1: Picture of the (a) Sawdust and
(b) Sawdust Ash 27
4.1 SEM of the
Unstabilized Lateritic Soil 52
4.2 SEM of the
Sawdust Ash 52
4.3 SEM of the
Stabilized Lateritic Soil 61
CHAPTER 1
INTRODUCTION
1.1 BACKGROUND OF STUDY
The
stabilization of lateritic soils is of great importance to the geotechnical
engineer as most engineering soils are lateritic. Generally, lateritic soils
are tropical soils formed from the tropical weathering process and contain an
appreciable amount of clay content, making them very useful as pavement
materials in highway construction and foundation/fill materials in building
construction and earthworks. Depending on the field performance, they can be
problematic and unproblematic (Eberemu, 2015). High moisture content, high
liquid limits and low natural densities are evident characteristics of
problematic lateritic soils (Osinubi, 1998). Lateritic soil must be able to
meet the required specification to be used as a construction material for
either road, earth dams, embankments and bridge. This has led researchers to
investigate possible means of improving the strength properties of the soil by
modifying its properties using either chemical, agricultural or environmental
waste products (Onyelowe, 2017).
Sawdust
which is a by-product of timber is classified as an agro-industrial waste
product from sawmills. 93.3% of the total number of wood-based industries in
Nigeria are sawmill industries (Fuwape, 1998). The use of sawdust in poultry
farms, cooking and growth of mushrooms constitutes a minimum amount as compared
to the amount of sawdust waste produced in the country. The remaining sawdust
waste can be incinerated and instead of it being dumped back into the
environment, can be used in stabilizing weak lateritic soil, due to its rich
pozzolanic property, thereby creating an eco-friendly environment that is free
of such waste.
In
recent times, much research energy has gone into the improvement of lateritic
soils using different forms of materials and chemicals that poses pozzolanic
properties, which acts as a form of a binder when hydrated to strengthen the
clay mineral bonds. The effective use of Industrial and Agro-based wastes ash
to replace expensive chemical stabilizers has been the interest of most
researchers in developing countries (Osinubi et al., 2009; Oluremi et al.,
2012; Eberemu, 2015; Adedokun et al.,
2016) because of their availability and cost effectiveness. Waste ash such as
Sawdust Ash (SDA), Corn Cub Ash (CCA), Rice Husk Ash (RHA), Millet Husk Ash
(MHA), Coconut Husk Ash (CHA), Locust Bean Ash (LBA), Bagasse Ash (BA) have
proven to poses some high amount of pozzolanic properties which can possibly be
used as a to replacement chemical stabilizers such as cement which contribute
to the emission of C02 to the atmosphere. The use of these waste ash
as an alternative to cement-based stabilizers are more Ecofriendly and
beneficial due to the improvement in waste management, reduction in
environmental pollution and its cost effectiveness. In the course of this
research, varying percentages of Saw-Dust-Ash (SDA) were used as stabilizing
material to stabilize weak lateritic soil in other to form a basis to predict
the unconfined compressive strength and the California Bearing Ratio of the
stabilized soil.
1.2 PROBLEM STATEMENT
The increased population growth has
led to a great need for good assess roads and to connect communities and cities
for business and other activities needed for good living. Unfortunately, most
of the road networks in the country are in a very bad deplorable state and requires
attention. Since the colonial periods, failure of highway pavements have been
normal phenomenom in the Nigerian highway system (Jegede 2000). These failures
on the highway pavement have led to a series of accidents and great loss of
lives and properties of the communities and cities it links. However lateritic
soil which is forms a large amount of the formation soil of pavement structures
occurs in a loose, structured state and collapse easily due to loading or
wetting, resulting in a sudden settlement (Toll, 2012).
For
soils to be suitable for highway pavement design, ground/soil improvements
methods are employed to address the several ground condition problems, to
improve the engineering properties of the soil. Several methods of
stabilization have long been investigated to improve the strength properties of
lateritic soils, some of which include soil densification involving compaction
or preloading, a hydraulic modification which includes dewatering or
electro-osmosis, admixture stabilization which includes mechanical, chemical
and biological stabilization, geosynthetic reinforcement and structural
inclusion (Nicholson, 2015).
In
the course of this research, admixture stabilization involving the use of
Sawdust ash was used in the stabilization of the lateritic soil with more
emphasis on the unconfined compressive strength (UCS) and California Bearing
Ratio (CBR) which are the strength properties of the soil.
Also
as regards to easy and accurate prediction of the strength parameters of the
soil in the field by consulting engineers and contractors, the use of Multiple
Linear Regression was used to predict the strength achievement of the lateritic
soil as it relates to an increase in the percentage of SDA (Sawdust Ash)
content.
1.3 AIM AND OBJECTIVES
The
aim of this research is to accurately predict the Unconfined Compressive
Strength (UCS) and California Bearing Ratio (CBR) of lateritic soil treated
with sawdust ash for sustainable earthwork constructions. The following
objectives have been designed to achieve the primary aim of the project;
i.
To determine the
geotechnical properties of the soil and its suitability to be used as a highway
material.
ii.
To characterize the saw
dust ash and lateritic soil using Scanning Electron Microscopy (SEM) and X-Ray Diffraction (XRD).
iii.
To determine the
engineering properties of the stabilized lateritic soil.
iv.
To determine the UCS of
the stabilized lateritic soils.
v.
To determine the CBR of
the stabilized lateritic soil.
vi.
To predict the UCS and
CBR of the sawdust stabilized lateritic soils using multiple linear regression
(MLR)
1.4 SCOPE OF STUDY
This
work forms its basis on a rich review of relevant literature based on sawdust
re-engineering, following rigorous laboratory and experimental findings to
discover the best approach to be used in this regard. The lateritic soil is
stabilized with varying proportions of the sawdust ash which forms our system
data set for predicting the unconfined compressive strength and California
Bearing Ratio. From the results, we shall develop a working model for convenient
and easy prediction of the UCS and CBR of lateritic soils and also draw up
conclusions and recommendations that would be used for future reference
purposes.
1.5 SIGNIFICANCE OF STUDY
Sawdust
ash forms part of the environmental waste when found in large quantities at the
dumpsite of the wood processing factory. Due to its pozzolanic property, it can
react readily with water to form a paste that can be used in the
modification/re-engineering of weak lateritic soil deposits, which could be
viewed as waste recycling. The modified lateritic soil is of great importance
in highway engineering as laterite forms a larger amount of formation soils in
the country.
Moreover,
easy prediction of the UCS of the modified lateritic soil is achieved to help highway
contractors and quality control and quality assurance engineers on-site to
easily predict the strength attainment of sawdust modified lateritic soils on
site.
1.6 LIMITATIONS OF STUDY
This
research work only covers the prediction of the Unconfined Compressive Strength
(UCS) and the California Bearing Ratio (CBR) of Lateritic soils modified with
sawdust ash using Multiple Linear Regression. The effect of the sawdust on the
lateritic soil with time was not considered. Other predictive models such as Gene
Expression Programming and Artificial Neural Networks can also be employed in
the prediction of the UCS and CBR in order to compare models which can be used
in predicting the UCS and CBR of the lateritic soil.
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