ALEX ACHEAMPONG

268 Pages·2015·5.83 MB·English

KWAME NKRUMAH UNIVERSITY OF SCIENCE AND TECHNOLOGY,
KUMASI

SHEAR STRENGTH PROPERTIES OF STRUCTURAL LIGHTWEIGHT
REINFORCED CONCRETE BEAMS AND TWO-WAY SLABS USING
PALM KERNEL SHELL COARSE AGGREGATES

BY
ALEX ACHEAMPONG (BSc. Building Technology)

A Thesis submitted to the Department of Building Technology,
College of Art and Built Environment
in partial fulfillment of the requirements for the degree of
DOCTOR OF PHILOSOPHY in BUILDING TECHNOLOGY

NOVEMBER, 2015
DECLARATION
I hereby declare that this submission is my own work for the award of Doctor of Philosophy
degree in Building Technology and that, to the best of my knowledge, it contains no
materials previously published by another person or material which has been accepted for
the award of any other degree of the university, except where reference has been made in
the text.

Alex Acheampong ……………………… …………………………
(Student) Signature Date

CERTIFIED BY:

Prof. J. Ayarkwa ………………………. …………………………..
(1st Supervisor) Signature Date

Prof. C. K. Kankam ……………………….. …………………………..
(2nd Supervisor) Signature Date

Dr. B. K. Baiden ……………………….. ……………………………
Head of Department Signature Date
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ABSTRACT
In the last three decades, the use of Palm Kernel Shells (PKS) as coarse aggregate in
concrete has continuously received increasing attention among researchers, especially in
Africa. This is primarily due to its environmental and economic benefits. However, while
considerable amount of research has been carried out to assist in understanding its concrete
mix designs and associated mechanical properties, a limited amount of works have been
carried out to assist in the current understanding with respect to its shear resistance. The
main objective of this study was to investigate the shear strength properties of structural
lightweight reinforced concrete shallow beams and two-way slabs using PKS coarse
aggregates. A comparison between properties of PKS concrete and normal weight concrete
(NWC) was made. The effect of types of cement on the mechanical properties of both PKS
and NWC were also investigated. The materials phase of this research evaluated fresh
concrete properties such as slump, and the key mechanical properties of hardened concrete,
that is, compressive, flexural tensile strengths and density. The study employed a series of
trial mixes, which resulted in casting and testing 216 cubes and 180 modulus of rupture
beams at 7, 14, 21, 28, 56, and 90-days of curing, to obtain an optimum mix design. The
third phase of the study consisted of testing 46 reinforced concrete beams to evaluate the
flexural response of the reinforced PKS concrete and NWC beams, with and without shear
reinforcement. The 46 beams consisted of 19 beams without shear reinforcement (15 PKS
concrete and 4 NWC) and 27 beams with shear reinforcement (21 beams were cast with
PKS and 6 beams were cast with granite aggregates). The variables of the third phase were
the overall depth of the beams, longitudinal reinforcement, shear reinforcement, shear
span-to-depth ratio and modes of loading. The fourth phase of the study investigated the
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flexural response of eight two-way slabs (four slabs were cast with PKS and four were cast
with granite aggregates). The main variables were concrete strength and the modes of
loading. The study revealed that the physical and mechanical properties of the PKS
aggregate are satisfactory for producing structural lightweight aggregate concrete. The 28-
day air-dry density of PKS concrete was within the range for structural LWAC. The 28-
day compressive strength of the concrete produced in this study was found to satisfy the
minimum strength requirements of a structural concrete based on BS 8110-1 and ASTM
C330. It was found that PKS concrete beams with and without shear reinforcement
behaved in a similar manner to those of NWC beams based on the range of parameters
tested, including the cracking modes. PKSC two-way slabs mostly failed as a result of
punching shear. The study further revealed that the design equations of the British
Standards Institute, American Concrete Institute and Eurocode 2 can be used to safely
predict the shear capacity of PKS concrete beams with and without shear reinforcement. It
is further concluded that PKS aggregates can be used in the production of LWC for
structural applications in Ghana.

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TABLE OF CONTENT
DECLARATION.............................................................................................................. II
ABSTRACT ..................................................................................................................... III
TABLE OF CONTENT .................................................................................................... V
LIST OF TABLES ....................................................................................................... XIII
LIST OF FIGURES ....................................................................................................... XV
NOMENCLATURE ..................................................................................................... XIX
ACKNOWLEDGEMENT .......................................................................................... XXII
DEDICATION........................................................................................................... XXIII
INTRODUCTION..............................................................................................................1
1.1 BACKGROUND ........................................................................................................1
1.2 PROPERTIES OF REINFORCED LWC ...................................................................4
1.3 PROBLEM STATEMENT .........................................................................................7
1.4 AIM ..........................................................................................................................10
1.5 SPECIFIC OBJECTIVES .........................................................................................10
1.6 SIGNIFICANCE OF STUDY ..................................................................................11
1.7 OUTLINE OF THESIS ............................................................................................14
CHAPTER TWO .............................................................................................................16
LITERATURE REVIEW ...............................................................................................16
2.1 INTRODUCTION ....................................................................................................16
2.2 DIFFERENCE BETWEEN NWC AND LWAC ......................................................16
2.3 LIGHTWEIGHT AGGREGATE CONCRETE (LWAC) ........................................17
2.3.1 Key Hardened Properties of LWAC ................................................................18
2.3.1.1 Compressive strength ...........................................................................19
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2.3.1.2 Tensile Strength ..........................................................................................23
2.3.2 Constituents of Lightweight Concrete ...............................................................24
2.3.2.1 Cement ........................................................................................................25
2.3.2.2 Water ...........................................................................................................27
2.3.2.3 Admixtures ..................................................................................................28
2.3.2.4 Aggregates ..................................................................................................29
2.4 PROPERTIES OF LIGHTWEIGHT AGGREGATES .............................................32
2.4.1 Shape .................................................................................................................32
2.4.2 Flakiness and elongation indices .......................................................................34
2.4.3 Texture ...............................................................................................................35
2.4.4 Grading/ Particle size distribution .....................................................................36
2.4.5 Aggregate moisture content ...............................................................................38
2.4.6 Porosity and Water Absorption of Aggregates ..................................................40
2.5 PALM KERNEL SHELL CONCRETE ...................................................................43
2.5.1 Oil Palm Tree Species .......................................................................................43
2.5.2 Species in Ghana ...............................................................................................43
2.5.3 Make-up of Palm Kernel Shells .........................................................................44
2.5.4 Chemical composition of PKS ..........................................................................48
2.5.5 Mechanical Properties of PKS Concrete ...........................................................48
2.5.5.1 Compressive Strength of PKSC ..................................................................48
2.5.5.2 Modulus of rupture .....................................................................................50
2.5.6 Structural behaviour of PKS Concrete beams ...................................................52
2.5.6.1 Flexural strength behaviour of PKS beams ................................................52
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2.5.6.2 Shear strength of PKS concrete beams .................................................53
2.6 SHEAR TRANSFER MECHANISM IN BEAMS ...................................................55
2.6.1 Introduction .....................................................................................................55
2.6.2 Influencing factors on the failure mechanisms ................................................58
2.6.2.1 Effect of shear span-to-effective depth ratio, a/d .................................58
2.6.2.2 Effect of beam size ...............................................................................59
2.6.2.3 Concrete strength ........................................................................................60
2.6.2.4 Aggregate type ............................................................................................60
2.6.2.5 Percentage of Tension steel ........................................................................61
2.6.3 Behaviour of Lightweight Aggregate Concrete in shear ...................................61
2.6.4 Shear Cracking and crack width ......................................................................62
2.6.5 Code Provisions against Shear Failure for lightweight concrete .......................64
2.6.5.1 Provisions in BS 8110 (1997) ..............................................................64
2.6.5.2 Provisions in EC 2 (2004) ....................................................................65
2.6.5.3 Provisions in ACI 318 – 08 (2008) .......................................................66
2.7 FLEXURAL THEORY OF RC TWO-WAY SLABS .........................................68
2.6.6 Summary ............................................................................................................69
CHAPTER THREE .........................................................................................................70
MATERIALS AND METHODS ....................................................................................70
3.1 INTRODUCTION ...............................................................................................70
3.2 TEST MATERIALS ............................................................................................70
3.2.1 Cement .............................................................................................................70
3.2.2 Water ...............................................................................................................71
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3.2.3 Superplasticizer ...............................................................................................71
3.2.4 Normal weight aggregates ...............................................................................71
3.2.5 Palm kernel shell aggregates .............................................................................72
3.3 CHEMICAL PROPERTIES OF PKS .......................................................................73
3.4 PHYSICAL PROPERTIES OF THE COARSE AGGREGATES ............................73
3.4.1 Aggregate shape ................................................................................................74
3.4.2 Water absorption ................................................................................................74
3.4.3 Specific gravity ..................................................................................................74
3.4.4 Aggregate impact value (AIV) ..........................................................................75
3.4.5 Aggregate crushing value (ACV) ......................................................................75
3.3.6 Aggregate abrasion value (AAV) ......................................................................76
3.5 MECHANICAL PROPERTIES ...............................................................................76
3.5.1 Mix Design ........................................................................................................76
3.5.1.1 Mix Proportions ..............................................................................................77
3.5.2 Workability of concretes ...................................................................................79
3.5.3 Laboratory batching and mixing........................................................................79
3.6 COMPRESSIVE STRENGTH AND DENSITY OF CONCRETE MIXES ............80
3.6.1 Preparation of test Specimens ............................................................................80
3.6.2 Curing of concrete cubes ...................................................................................81
3.6.3 Testing of concrete cubes ..................................................................................81
3.7 FLEXURAL TENSILE STRENGTH (MODULUS OF RUPTURE) OF
PLAIN ............................................................................................................................82
3.7.1 Preparation of test specimens ............................................................................82
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3.7.2 Testing of beams for flexural tensile strength ...................................................83
3.8 REINFORCED CONCRETE BEAMS ...............................................................84
3.8.1 Design of the Reinforced Concrete Beam Specimens .......................................84
3.8.2 Reinforcement details ........................................................................................89
3.8.3 Reinforced Concrete Specimen Identification ...................................................90
3.8.4 REINFORCED CONCRETE SPECIMEN PREPARATIONS ......................92
3.8.4.1 Materials .....................................................................................................92
3.8.4.2 Reinforced Concrete Beam Preparation......................................................93
3.8.4.3 Test Setup and instrumentation ...................................................................94
3.9 REINFORCED CONCRETE TWO-WAY SLABS ............................................95
3.9.1 Specimen details ..............................................................................................95
3.9.2 Specimen Identification ...................................................................................96
3.9.3 Reinforced concrete specimen preparations ....................................................96
3.9.3.1 Materials .....................................................................................................96
3.9.4.2 Reinforced Concrete Slab Preparation ........................................................97
3.9.4.3 Test Setup and instrumentation ...................................................................98
CHAPTER FOUR ..........................................................................................................100
RESULTS AND DISCUSSION ....................................................................................100
4.1 INTRODUCTION ..................................................................................................100
4.2 PHYSICAL PROPERTIES OF PKS AND NORMAL WEIGHT
AGGREGATES ...........................................................................................................100
4.2.1 Particle size distribution ................................................................................100
4.2.2 Aggregate shape ..............................................................................................102
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4.2.3 Water absorption ..............................................................................................104
4.2.4 Specific gravity ................................................................................................104
4.2.5 Aggregate impact value (AIV) ........................................................................105
4.2.6 Aggregate crushing value (ACV) ....................................................................105
4.2.7 Aggregate Abrasion Value (AAV) ..................................................................106
4.3 DRY DENSITY OF CONCRETES ..................................................................107
4.4 EFFECT OF SUPERPLASTICIZER (SP) ON THE WORKABILITY OF PKS
CONCRETE .................................................................................................................109
4.5 COMPRESSIVE STRENGTH ...............................................................................113
4.5.1 Compressive strength with age of curing ......................................................113
4.5.2 Comparison of PKS-OPC and PKS-PLC concrete........................................114
4.5.3 Comparison of test results with minimum code provisions ............................116
4.5.4 Mode of failure of PKS concrete cubes .........................................................117
4.5.5 Compressive strength and density of the concrete cubes ................................120
4.6 TENSILE BEHAVIOUR OF THE CONCRETE ...................................................121
4.6.1 Tensile Failure beams ....................................................................................123
4.7 BEHAVIOUR OF REINFORCED CONCRETE BEAMS IN FLEXURE .......124
4.7.1 Details of PKS concrete and NWC (Control) Beams ....................................124
4.7.2 BEHAVIOUR OF BEAMS WITHOUT SHEAR REINFORCEMENT ......127
4.7.2.1 General load-deflection behaviour of the beams ................................127
4.7.2.2 Crack Development Patterns of the Beams ..............................................131
4.7.2.3 Effect of longitudinal reinforcement, 𝝆𝒘 on deflection and cracking of
PKS beams ............................................................................................................135
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