iii

FLEXURAL BEHAVIOR OF PERMANENT PRECAST FORMWORK BEAMS

NURULSIQQIN AISHAH BT MD YUSUF

A project report submitted in partial fulfillment of the

requirements for the award of the degree of Master of Civil Engineering (Civil – Structure)

Faculty of Civil Engineering

Universiti Teknologi Malaysia

JANUARY 2014

iii

Specially dedicated to my beloved

Family and friends

v

ACKNOWLEDGEMENT

Foremost, I would like to express my sincere gratitude to my supervisor, Dr

Roslli Noor Mohamed for the continuous support of my master project research, for

his patience, motivation, enthusiasm, and immense knowledge. His guidance helped

me in all the time of research and writing of this thesis. I could not have imagined

having a better supervisor and mentor for my master study.

My sincere thanks also go to all technicians at Material and Structure

Laboratory, Faculty of Civil Engineering who have provided assistance at various

occasions. Their views and guidance are useful indeed.

I thank my fellow lab mate, Shariwati Mansor, for the stimulating discussions, for

the sleepless nights we were working together before deadlines, and for all the fun

we have had in the last one and half years.

Last but not the least; I would like to thank my family supporting me

spiritually throughout my life.

vi

ABSTRACT

This study is to explore the flexural behaviour of permanent precast formwork beam.

The total three beams that have dimensions 150 mm x 300 mm x 3000 mm have

been casted and tested. Two beams are permanent precast formwork beam and one

beam as a control beam. The beam have been tested using America Society Testing

and Material (ASTM) C78 for testing flexural strength of concrete beams using a

four point bend test by the third-point method. The results show that the permanent

precast formwork beams exhibit increased flexural strength and higher bending

capacity compared to normal concrete beam.

vii

ABSTRAK

Kajian ini adalah untuk mengkaji kelakuan lenturan rasuk acuan kekal

pratuang. Tiga rasuk sebagai spesimen yang mempunyai dimensi 150 mm x 300 mm

x 3000 mm telah diuji. Dua rasuk pratuang adalah rasuk acuan kekal dan satu rasuk

sebagai rasuk kawalan. Rasuk telah diuji menggunakan America Society Testing and

Material (ASTM) C78 untuk menguji kekuatan lenturan rasuk konkrit menggunakan

kaedah ujian empat titik dengan kaedah tiga titik. Keputusan menunjukkan bahawa

rasuk pratuang acuan tetap menunjukkan peningkatan kekuatan lenturan dan

keupayaan lenturan yang lebih tinggi berbanding dengan rasuk konkrit biasa.

viii

TABLE OF CONTENTS

CHAPTER TITLE PAGE

DECLARATION ii

DEDICATION iii

ACKNOWLEDGEMENT iv

ABSTRACT v

ABSTRAK vi

TABLE OF CONTENTS vii

LIST OF TABLE x

LIST OF FIGURE xi

LIST OF SYMBOL xiii

1 INTRODUCTION

1.1 Introduction

1

1

1.2 Background of study 2

1.3 Problem Statement 8

1.4 Objectives of The Study 10

1.5 Scope of The Study 10

2 LITERATURE REVIEW 11

2.1 Introduction

2.2 Concrete Formwork

2.3 Mortar Mix

11

12

14

ix

2.4 Concrete Mix

2.5 Concrete Material

15

16

2.5.1 Cement 17

2.5.2 Aggregate 18

2.5.3 Water 20

2.6 Concrete Quality 20

2.7 Fiber-Reinforced Mortar 21

2.6 Flexural Behavior Of Concrete Beam

2.7 Glass Fibre

22

27

2.7.1Type of Glass Fibre 27

2.7.2 Properties of Glass Fibre 28

2.6 Glass Fibre Reinforced mortar 29

2.7 Stress and Strain Distribution in Concrete Beams 32

3 METHODOLOGY 34

3.1 Introduction 34

3.2 Types of Mix Design

3.3 The Material for the Mix Design

36

37

3.4 Beam Specimen 40

3.3 Experimental Work 41

3.3 Beam design 46

3.3 preparation of steel reinforcement 48

3.3 Preparations of Formwork 49

3.3 Method for mixing the concrete 51

3.3 Curing method 53

3.3Compression Strength Test 55

3.3 Flexural Strength Test on Mortar Prism 56

4 RESULTS AND DISCUSSIONS 57

4.1 Introduction 57

4.2 Optimum Content of Glass Fibre In Mortar Mix 58

x

4.3 Cube Test for Concrete

4.4 Flexural Strength Test of Beam

62

64

4.4.1 Load deflection analysis 65

4.4.2 Strain Distribution Across The Depth 69

4.4.3 Reinforcement Strain Analysis

73

5 CONCLUSION

5.1 Introduction

72

72

5.2 Conclusion 72

5.3 Recommendation

73

REFERENCES 75

APPENDICES

77

xi

LIST OF TABLES

TABLE

NO

TITLE PAGE

1.1 Properties of glass fibre reinforced concrete. 8

3.1 Weight required for mortar mix design 33

3.2 Steel reinforcement arrangement 44

4.1 Average Compression strength of glass fibre mortar cube 59

4.2 Compressive strength of concrete for design mix 61

4.3 Comparison in term of ultimate load and deflection 65

4.4

4.5

The value of x beam Result of splitting tensile test

Comparison between experimental and theoretical on ultimate

load and ultimate moment

69

70

xii

LIST OF FIGURES

FIGURE

NO

TITLE PAGE

1.1 Sample of permanent precast formwork 2

1.2 The view of site construction that uses traditional timber

formwork.

9

2.1 Permanent concrete formwork beam 12

2.2 Flexural behaviour of concrete beam 23

2.3 The reaction of the beam under un-cracked zone 24

2.4 The reaction of the beam under service load zone 25

2.5

3.1

The reaction of the beam under ultimate strength zone.

Ordinary Portland Cement

25

34

3.2 Sand 35

3.3 Various size of aggregate. 36

3.4 Glass Fibre Polymers 37

3.5 Strain gauge. 39

3.6 Linear Variable Differential Transformers (LVDT). 40

3.7 Hydraulic jack 41

3.8 Load cell. 41

3.9 Beam testing frame 42

3.10 The Third-Point Loading Flexural Strength Test (ASTM C78). 43

3.11 The location of the loading for ASTM C78. 43

3.12 The arrangement of reinforcement and link for the beam 45

3.13 Bar bend machine used to bend steel bars into desire shape 46

3.14 Beam ready for concreting 46

xiii

3.15 Formwork for normal concrete beam 47

3.16 (a),

(b)

The casting process of preparing permanent formwork 48

3.17 Permanent precast formworks 49

3.18 Compaction processes of cubes 50

3.19 The beam while been casted 50

3.20 The concrete was vibrated by vibrator poker 51

3.21 Curing of beam using wet gunny sacks 52

3.22 Curing process inside water tank for concrete cubes 52

3.23 The preparation of mortar cube 53

3.24 The compression test on mortar cube 53

3.25 The flexural test on mortar prism 54

3.26 The condition of the mortar prism after flexural test 54

4.1 (a),

(b)

Graph of Average Compressive Strength (Mpa) Versus

Percentage of Glass Fibre in Mortar Mix (%)

56

4.2 (a),

(b)

Graph of tensile stress (Mpa) versus deflection (mm) of mortar

prism

57

4.3

4.4

4.5

4.6

4.7

4.8

4.9

4.10 (a)

4.10 (b)

4.10 (c)

4.11 (a)

Optimum content of glass fibre in mortar mix design

Graph of load (kN) versus deflection (mm) for mortar

Graph of Compressive strength (MPa) versus age (day

Failure mode of concrete cube after compression test

The arrangement of flexural strength test on beam

Damage at glass fibre permanent precast formwork beam

Graph of load (kN) versus deflection (mm) for beam

The condition of the beam after flexural test done for Normal

concrete beam

The condition of the beam after flexural test done for glass

fibre permanent precast formwork beam

The condition of the beam after flexural test done for wire mesh

permanent precast formwork beam

Concrete strain distributions for normal concrete beam

59

60

61

62

63

64

65

66

66

66

68

xiv

4.11(b)

4.12

Concrete strain distributions for glass fibre permanent precast

formwork beam

Graph of load (kN) versus reinforcement strain

66

71

xv

LIST OF SYMBOLS

As - Area of tension reinforcement

av - Shear span

b - Width of beam

bv - Width of beam, to be taken as b for a rectangular beam

d - Effective depth

E - Elastic modulus

Es - Modulus of elasticity of steel

εo - Concrete strain when peak stress is reached

εcu - Ultimate concrete strain at compression = 0.0035

εy - Design yield strain

Fcc - The resultant compressive force in the concrete

Fst - The resultant tensile force in the reinforcing steel

fcu - Characteristic strength of concrete

fy - Characteristic strength of reinforcement

h - Overall depth of beam

M - Bending moment

sv - Longitudinal spacing of link reinforcement

V - Shear force

v - Design shear stress

vc - Design shear stress for concrete

x - Neutral axis depth

γs - surface energy

Φ - Curvature

xvi

LIST OF EQUATIONS

EQUATION NO. PAGE

Equation 2.1 15

Equation 2.2 15

Equation 4.1 73

Equation 4.2 73

Equation 4.3 73

1

CHAPTER 1

INTRODUCTION

1.1 Introduction

Formworks as temporary structures are an important elements of the overall

construction plan. A temporary structure in construction affects the safety of the

workers on the job and the general public and there is also the relationship of the

temporary structure to the finished structure.

Temporary structures are sometimes incorporated into the finished work or

are removed at the end of the conclusion of their usefulness. In either case, the

contractor will have to deal with supervision work, code requirements, contract and

legal requirements, and perhaps disputes with others over the work being performed.

As far as design, drawings and specifications are concerned, they depend on the

temporary structure under consideration.

2

In the new era of construction, a more efficient and advantageous type of

formwork is widely used by growing numbers of contractors, which is the permanent

precast formwork. Permanent precast formworks have been widely used in nowadays

construction because it can develop innovative, it is more economical, and more

efficient method in construction compared to the usage of temporary formwork. By

using a permanent precast formwork, the construction of building can be more

efficient; the speed of the construction can be increased as well as the cost of the

construction, and can also reduce the manpower needed at the construction site.

Figure 1.1 Sample of permanent precast formwork

1.2 Background of Study

Formwork development has paralleled the growth of concrete construction

throughout the 20th century. The increasing acceptance of concrete as a major

construction material presents the form builder a new range of problems in the

development of appropriate sheathing materials and maintenance of rigid tolerances.

3

Formwork is a mould including all supporting structures, used to shape and

support the concrete until it attains sufficient strength to carry its own weight. It

should be capable of carrying all imposed dead and live loads apart from its own

weight.

There are some requirements of a good formwork system, which are:

i. The way the formwork can be erected and de-shuttered fast

.

ii. The good concrete quality and surface finish can be achieved.

iii. The optimum stock of formwork required for the size of work force, the

specified time schedule and flow of materials.

iv. The overall cost savings that can be achieved using the right type of

formwork.

v. The safety that can be improved for the site personnel.

In order to successfully carry out its function, formwork must achieve a

balance of following requirements such as containment, strength, resistance to

leakage, accuracy, ease of handling, access for concerted and economy.

Containment of formwork mean formwork must be capable of shaping and

supporting the fluid concrete until it cures. Strength of formwork must be capable of

safely withstanding without distortion or danger the dead weight of the fluid concrete

is placed on it, labour weight, equipment weight and any environmental loadings.

4

Resistance to leakage for formwork can be defined with all joints in

formwork must be either close fitting of covered with form tape to make them grout

tight. If grout leakage occurs the concrete will leak at that point. Leakages cause

honeycombing of the surface. Formwork must be accurately set out so that the

resulting concrete product is in a right place and is of correct shape and dimensions.

The formwork must be easy to handle which form panels and units should be

designed so that their maximum size does not exceed that which can be easily

handled by hand or mechanical means. In addition all formwork must also be

designed and constructed to include facilities for adjustments, levelling, easing and

striking without damage to the form work or concrete.

Any formwork arrangement should provide access for placing of the

concrete. The extent of this provision will be depending on the ease of carrying out

the concrete operations.

The cost of formwork is very expensive. On average about 35% of the total

cost of any finished concrete unit or element can be attributed to its formwork, out of

this just over 40% can be taken for material for formwork and 60% for labour. The

formwork designer must therefore not only consider the maximum number of times

that any form can be reused, but also produce a design that will minimize the time

taken for erection and striking.

Traditionally, formwork requirements have been left to the construction stage

and the main contractor's temporary works designer, but this can lead to significant

loss of benefit unless the permanent works designer provides appropriate guidance.

Permanent formwork in construction defines the terminology relating to permanent

formwork, identifies where the responsibilities lie for its design and safe use and

outlines the regulations governing its use.

5

This study is all about of the application of permanent precast formwork

beam that can develop innovative, economical and efficient methods of construction

in reducing the application of temporary formwork. There are many advantages of

using permanent precast formwork beam such as:

i. The construction of building more efficient.

ii. It can increase the speed of construction time and reduce money.

iii. The construction site is cleaner.

iv. It also can reduce the manpower at construction site improved safety

and economy of construction,

v. Long-term durability, appearance and reduced maintenance costs in

civil engineering applications.

According to Kamran (2007), formwork can be defined as a structure, usually

temporary, but in some cases wholly or partly permanent used to contain poured

concrete to mould it to the required dimensions and support it until it is able to

support itself. It consists primarily of the face contact material and the bearers that

directly support the face contact material.

Permanent formwork can be classified into two groups which participating

and non-participating (Design Manual for Roads and Bridges, 1991).

i. Participating formwork

Precast concrete units incorporating a welded lattice projecting into and

providing shear connection with the overlying insitu concrete deck to form a

composite deck slab. This is the only type of participating permanent

formwork which has been used in bridges in recent years.

6

ii. Non-participating formwork

a. Glass fibre reinforced cement (GRC) consisting of hydraulic mortars

reinforced with alkali resistant glass is manufactured to give a range of

sections designed to support various deck slab thicknesses and spans. Single

skin panels, either flat sheet or corrugated, where the in-situ concrete is in

contact with the GRC over the full surface area of the panel, are acceptable

for use. The use of polystyrene formers in the corrugations is not permitted.

b. Profiled steel sheeting (PSS) is usually of the order of 1mm thick and is

protected by galvanising with an additional polyester coating. This material

has not been widely used, but in a few instances corrosion to untreated cut

edges and site damage to the coatings has been observed, although this has

not seriously impaired the structural performance. PSS should not contain

indentations which may form a shear connection with the in situ concrete,

since there is a risk of fatigue cracking initiating from this detail.

c. Glass reinforced plastic (GRP) is a flat laminated panel consisting of a resin

mortar filling between two thin sheets of glass reinforced plastic. One surface

of the panel has projecting steel reinforcing ribs on edge encased within the

GRP. Generally these have performed satisfactorily although there have been

isolated cases of corrosion of the steel ribs. This was due to incomplete

covering by GRP material and was exacerbated by poor storage conditions of

the steel prior to manufacturing the panels. Properly manufactured panels

should not suffer from this problem. GRP formwork should only be used

with the ribs projecting into the in-situ concrete deck slab. There should be

no filler materials such as expanded polystyrene placed between the ribs,

which would prevent full contact between the deck concrete and the surface

of the ribbed panels.

7

In this study, there are two types of permanent precast formwork beam that

were used which are glass fibre reinforced concrete and glass fibre reinforced

concrete with wire mesh. Besides that, normal beam is used to be a control beam.

The study is carried out to investigate the differences of flexural behaviour precast

permanent formwork beam with normal beam.

Glass fibre Reinforced Concrete (GRC) has been extensively used as

permanent formwork for the past twenty years, corrugated or flat to suit all

supporting beam design.

GRC formwork has excellent performance characteristics and its inherent

material properties provide the specified and contractor with a permanent surface

skin to the bridge deck concrete which:

i. Has a thin cross section, yet provides durability and steel protection

equal to much thicker concrete cover.

ii. has a high resistance to fire and will not emit toxic fumes

iii. Eliminates spalling of exposed faces.

iv. Provides flexibility for pouring sequences and concreting schedules,

which can reduce construction time.

v. Enables the final appearance of the deck structure to be assessed on-site

before concrete is poured.

The GRC shall be the following properties on completion of cure. The dry

density of the GRC should not be less than 1700 kg/m³

8

Table 1.1 Properties of glass fibre reinforced concrete.

Compressive Strength (tested to ASTM : C 109/C 109M : 2002)

Maximum Load 53269.7 N

Compressive Strength 21.31 N/mm²

Flexural Strength (tested to ASTM : C 580 – 98)

Flexural Strength 33.8 N/mm²

Modulus of Elasticity 6172.8 MPa

Charpy Impact Strength (tested to ASTM 10.5 µm/mºC

Coefficient of Thermal Expansion (tested

to ASTM E831 : 2000)

10.5 µm/mºC

Thermal Conductivity (tested to ASTM

C518 : 1991)

0.12258 w/mºK

1.3 Problem Statement

Generally, conventional formwork is widely used in the construction in

Malaysia because of its flexibility and easy to produce. The most common

material for conventional formwork is timber and plywood. Traditional Timber

formwork is widely used in the construction in Malaysia because of its flexibility

and easy to produce. Traditional timber formwork is built on site out of timber and

plywood or moisture-resistant particleboard. Although it is easy to produce, the

time-consuming for larger structures to be built is longer, and the plywood facing

has a relatively short lifespan. The formwork which is made of wood or timber

9

may have to be replaced after a few uses.

Figure 1.2 The view of site construction that uses traditional timber

formwork.

As compared to traditional timber formwork, permanent precast formwork is

manufactured at factory. The main advantages of this permanent precast formwork is

reducing the traditional site based trades like traditional timber formwork, brickwork,

and plastering and thus enabling the contractors to reduce the overall labour content

in the building construction. By using permanent precast formwork, the use of wood

formwork can be reduced. It is also can develop the economical method of

construction. However, it is still used extensively where the labour costs are lower

than the costs for procuring reusable formwork. Moreover, the unskilled labourer can

be easily trained to construct building using the permanent precast formwork and

provide faster construction and cost saving.

10

1.4 Objectives of Study

The objectives of this case study are:

i. To obtain an optimum content of glass fibre in glass fibre mortar mix

design.

ii. To investigate the flexural behaviour and bending capacity of

permanent precast formwork beams.

1.5 Scope of Study

This study is mainly focused on the testing of concrete beams with different

types of permanent precast formwork under the four point bend test. Design

calculation and laboratory work were carried out accordingly to achieve the

objectives of this study.

This study was conducted in the Material and Structure Laboratory. In the

laboratory work, three beams were casted and tested using the same grade of

concrete, steel bars reinforcement, and testing method. The results of this study are

used to determine the flexural behaviour of the beam and which types of formwork

have higher bending capacity under the four point bend test.

78

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