i

PSZ 19:16 (Pind. 1/97)

UNIVERSITI TEKNOLOGI MALAYSIA

BORANG PENGESAHAN STATUS TESIS JUDUL : APPLICATION OF POLYMER IN CONCRETE CONSTRUCTION

SESI PENGAJIAN: 2007/2008

Saya __________________ LEE ENG HING__________________________ (HURUF BESAR)

mengaku membenarkan tesis (PSM/Sarjana/Doktor Falsafah)* ini disimpan di Perpustakaan Universiti Teknologi Malaysia dengan syarat-syarat seperti berikut: 1. Tesis adalah hakmilik Universiti Teknologi Malaysia. 2. Perpustakaan Universiti Teknologi Malaysia dibenarkan membuat salinan untuk tujuan pengajian sahaja. 3. Perpustakaan dibenarkan membuat salinan tesis ini sebagai bahan pertukaran antara institusi pengajian tinggi. 4. **Sila tandakan ( ) (Mengandungi maklumat yang berdarjah keselamatan atau SULIT kepentingan Malaysia seperti yang termaktub di dalam AKTA RAHSIA RASMI 1972) TERHAD (Mengandungi maklumat TERHAD yang telah ditentukan oleh organisasi/badan di mana penyelidikan dijalankan) TIDAK TERHAD Disahkan oleh

____________________________ ____________________________ (TANDATANGAN PENULIS) (TANDATANGAN PENYELIA) Alamat Tetap: 30, JALAN 6/27D, PM DR. ABDUL RAHMAN MOHD. SAM WANGSA MAJU SEKSYEN 6, Nama Penyelia 53300, KUALA LUMPUR. Tarikh: 14th. November 2007 Tarikh: 14th. November 2007 CATATAN * Potong yang tidak berkenaan.

** Jika tesis ini SULIT atau TERHAD, sila lampirkan surat daripada pihak berkuasa/organisasi berkenaan dengan menyatakan sekali sebab dan tempoh tesis ini perlu dikelaskan sebagai SULIT atau TERHAD.

Tesis dimaksudkan sebagai tesis bagi Ijazah Doktor Falsafah dan Sarjana secara penyelidikan, atau disertasi bagi pengajian secara kerja kursus dan penyelidikan, atau Laporan Projek Sarjana Muda (PSM).

ii

APPLICATION OF POLYMER IN CONCRETE CONSTRUCTION

LEE ENG HING

A report submitted in partial fulfillment of the

requirements for the award of the degree of

Bachelor of Civil Engineering

Faculty of Civil Engineering

Universiti Teknologi Malaysia

NOVEMBER, 2007

iii

APLIKASI POLYMER DALAM PEMBINAAN KONKRIT

LEE ENG HING

Laporan ini dikemukakan sebagai memenuhi

Sebahagian daripada syarat penganugerahan

Ijazah Sarjana Muda kejuruteraan Awam

Fakulti Kejuruteraan Awam

Universiti Teknologi Malaysia

NOVEMBER, 2007

iv

I hereby declare that I have read this thesis and in my opinion this thesis is sufficient in

terms of scope and quality for the award of the Bachelor Degree of Civil Engineering.

Signature :

Name of Supervisor : Assoc. Prof. Dr. Abd. Rahman Mohd. Sam

Date : 14 November 2007

v

I declare that this thesis entitled the application of polymer in concrete construction is

the result of my own research except as cited in the references. The thesis has not been

accepted for any degree and is not concurrently submitted in candidature of any other

degree

Signature : .

Name : LEE ENG HING

Date : 14 November 2007

vi

ACKNOWLEDGEMENTS

I would like to take this opportunity to thank and acknowledgement certain

people, whom if not for their contribution and help, the completion of this thesis would

not be possible. I wish to express my sincere appreciation to my supervisor, Assoc. Prof.

Dr. Abdul Rahman Mohd. Sam. I am truly indebted for his advise and guidance. His

abundant knowledge in civil and construction field is a benefit for me. A word of thank

also to Dr. Norhazilan Mohd. Nor for his help and guidance during my course of study.

I would like to extend my gratitude to all my colleagues who have provided

assistance in various occasions. I truly value their assistance and valuable views.

Last but not least, my gratitude and thank goes to my family members for their

support and motivation. I would like to end by saying that the people mentioned above

will hold dear in my heart and will never be forgotten. Thank you all.

vii

ABSTRACT

Due to the low tensile strength of concrete, when structural concrete elements

deteriorate, are subjected to extreme loadings, or react to corroded reinforcing steel, a

portion of the concrete separates from the component and results in a void that needs to

be repaired. Although there have been numerous investigations on patching damaged

concrete, the majority of these focus on the high strength and rapid set time of the patch

material, neither of which guarantee the durability of a repair. This study evaluated the

application of polymer in concrete construction. The performance of the polymer as

repair materials in concrete construction was compared to data reported by

manufacturers. It was determined that the most important properties for durable concrete

repairs are modulus of elasticity and bond strength. To select an appropriate repair

material, an engineer must be aware of two factors: the repair materials compatibility

with the existing concrete, and the repair material application. Manufacturers use a wide

variety of tests to determine the strength of their product; this information can often

mislead engineers into using a material that is not appropriate for their situation.

Therefore, it is essential to understand the material properties that directly affect repairs

and the tests used to determine them.

viii

ABSTRAK

Disebabkan kekuatan tegangan konkrit yang rendah, apabila elemen konkrit

struktur merosot, ia mengalami beban yang besar, atau bertindak menyebabkan

pengaratan tertulang, sebahagian konkrit pecah daripada komponen dan menghasilkan

lompang yang memerlukan pembaikan. Walaupun terdapat banyak kajian dalam

pembaikan kerosakan konkrit, kebanyakannya menumpu kepada bahan kekuatan tinggi

dan masa set cepat, kedua-duanya tidak memberi jaminan dalam pembaikan yang

tahan lasak. Kajian ini menilai aplikasi polimer dalam pembinaan konkrit. Perlaksanaan

polimer sebagai bahan pembaikan dalam pembinaan konkrit telah dibanding dengan data

yang dilapor oleh pengeluar bahan. Ciri yang paling penting dalam menentukan tahan

lasak konkrit ialah modules keanjalan dan kekuatan lekatan. Untuk memilih bahan yang

sesuai, jurutera mesti memberi perhatian kepada dua faktor : keserasian bahan

pembaikan dengan konkrit sedia ada dan aplikasi bahan pembaikan. Pengeluar bahan

mengunakan ujikaji yang berbagai untuk menentukan kekuatan produk mereka ;

maklumat ini selalu mengelirukan jurutera dalam pengunaan bahan yang sesuai dengan

situasi. Oleh itu, amatlah perlu memahami ciri-ciri bahan yang akan mempengaruhi

kerja pembaikan serta ujian-ujian untuk menentukannya.

ix

TABLE OF CONTENT

CHAPTER TITLE PAGE

AUTHENTICATION THESIS i

TITLE ii

TITLE IN BAHASA MALAYSIA iii

DECLARATION FROM LECTURER iv

STUDENT DECLARATION v

ACKNOWLEDGEMENT vi

ABSTRACT vii

ABSTRAK viii

CONTENT ix

LIST OF TABLES xii

LIST OF FIGURES xiii

1 INTRODUCTION 1.1 Introduction 1

1.2 Problem Statement 2

1.3 Aim 3

1.4 Objectives 3

1.5 Scope of Research 4

2 LITERATURE REVIEW

2.1 Introduction 5

2.2 Concrete Problems 5

2.2.1 Construction Errors 7

x

2.2.2 Design Errors 8

2.2.3 Disintegration and Scaling 9

2.2.4 Spalling and Popouts 9

2.2.5 Steel Reinforcement Corrosion 10

2.3 Cracks in Concrete 11

2.4 Repair of Concrete Structures 13

2.4.1 Evaluation of Concrete 13

2.4.2 Selection of Repair System 14

2.4.3 Conventional repair materials and systems 15

2.5 Introduction to Polymers 17

2.6 Polymer Modified Concrete 18

2.6.1 Polymer Impregnated Concrete 20

2.6.2 Polymer Cement Concrete 22

2.7 Polymer Concrete 25

2.7.1 Nature and General Properties 25

2.7.2 Acrylic Polymer Concrete 28

2.7.3 Polyester Polymer Concrete 29

2.7.4 Epoxy Polymer Concrete 30

2.7.5 Furan Polymer Concrete 31

2.8 General Patch Behavior 31

2.8.1 Cleaning and Preparing Concrete 31

Before Repair31

3. METHODOLOGY 3.1 Introduction 36

3.2 Steps in Conducting Case Study 37

3.2.1 Problem Statement Foundation 37

3.2.2 Literature Review 37

3.2.3 Information and Data Collection 37

3.2.4 Data Analysis 37

3.2.5 Conclusion 37

xi

4. RESULTS AND DISCUSSION

4.1 Case Study 38

4.2 Project Solaris Dutamas 2 41

4.2.1 Nitomortar PE 43

4.2.2 Nitofil LV 44

4.2.3 Renderoc FC 45

4.2.4 Nitobond SBR 46

4.3 Mechanism of polymer coatings degradation 48

4.4 Rebounding and cracking of coatings 50

4.5 Problems in The Use of Polymer Based Materials 50

4.6 Property Mismatch and Composite Performance 51

4.6.1 Range of Polymer Properties 51

4.6.2 Temperature/Time relationship 52

4.6.3 Curing Conditions 52

5. CONCLUSION AND SUGGESTION

5.1 Introduction 54

5.2 Conclusions 54

5.3 Suggestions 55

REFERENCES 56

xii

LIST OF TABLES TABLE NO. TITLE PAGE 2.1 Causes of Distress and Deterioration of Concrete [2] 6

2.2 Composition of concrete repair systems [5] 16

2.3 Categories of systems for concrete patch repair [5] 17

2.4 Application methods and properties of concrete repair materials [5] 17

2.5 Typical Properties of Polymer-Containing Concrete Composites 19

and Portland Cement Concrete [8]

2.6 General Characteristics And Applications of 19

Polymer-Modified Concretes [8]

2.7 Typical Range of Properties of Common PC Products and 27

Portland Cement Concrete [9]

2.8 General Characteristics And Applications of 27

Polymer Concrete Products [9]

4.1 Projects using polymer in concrete construction 38

4.2 Repair system and repair purpose 41

4.3 Polymer material use in Solaris Dutamas 2 42

4.4 Properties of Nitomortar PE 44

4.5 Properties of Nitofil LV 45

4.6 Properties of Renderoc FC 46

4.7 Properties of Nitobond SBR 47

4.8 Advantages and Disadvantages of Polymer in Construction 47

4.9 Classification of degradation of polymer coatings [10] 49

xiii

LIST OF FIGURE

FIGURE NO. TITLE PAGE 3.1 Research out flow 36 4.1 The cause of concrete problem in the selected project sites 40 4.2 The application of polymer in concrete construction 40

4.3 The percentage of polymer product by locations 42

1

CHAPTER 1

INTRODUCTION 1.1 Introduction

Despite being thought of as a modern material, concrete has been in use for

hundreds of years. The word concrete comes from the Latin concretus, which means

mixed together or compounded. Concrete is an extremely popular structural material

due to its low cost and easy fabrication.

Concrete is made up of sand or stone, known as aggregate, combined with

cement paste to bind it. Aggregate can be of various sizes. It is broadly categorized as

fine (commonly sand) and coarse (typically crushed stone or gravel). The greater

proportion of concrete is aggregate which is bulky and relatively cheaper than the

cement.

As much of the constituents of concrete come from stone, it is often thought that

concrete has the same qualities and will last forever. Concrete has been called artificial

stone, cast stone, reconstructed stone and reconstituted stone. However, concrete must

be thought of as a distinct material to stone. It has its own characteristics in terms of

durability, weathering and repair.

Concrete is a relatively durable and robust building material, but it can be

severely weakened by poor manufacture or a very aggressive environment. A number of

2

historic concrete structures exhibit problems that are related to their date of origin. These

problems can be solved by application of polymer in concrete construction.

A polymer is a large molecule containing hundreds or thousands of atoms

formed by combining one, two or occasionally more kinds of small molecule (monomers)

into chain or network structures. The main polymer material used in concrete

construction are polymer modified concrete and polymer concrete.

Polymer modified concrete may be divided into two classes: polymer

impregnated concrete and polymer cement concrete. The first is produced by

impregnation of pre-cast hardened Portland cement concrete with a monomer that is

subsequently converted to solid polymer. To produce the second, part of the cement

binder of the concrete mix is replaced by polymer (often in latex form). Both have

higher strength, lower water permeability, better resistance to chemicals, and greater

freeze-thaw stability than conventional concrete.

Polymer concrete (PC), or resin concrete, consists of a polymer binder which

may be a thermoplastic but more frequently is a thermosetting polymer, and a mineral

filler such as aggregate, gravel and crushed stone. PC has higher strength, greater

resistance to chemicals and corrosive agents, lower water absorption and higher freeze-

thaw stability than conventional Portland cement concrete.

1.2 Problem Statement

Concrete does not necessary perform as we would like. A long-term ageing

effect caused by drying-out of the cement matrix in concrete will be evident and result in

reduced strength. A combination of dry and wet concrete may cause differential

shrinkage which in turn may well lead to cracking. These cracks shorten the service lives

of the structure and increase the cost for maintenance and repairs.

3

Issues such as cost, absence of design codes, lack of industry standardization,

poor understanding of construction issues by composites industry, lack of designers

experienced with polymer composite materials and civil/building construction are

commonly claimed to place these materials at a disadvantage when considered against

traditional construction materials.

The need for research is great as evidenced by the continuing history of cracking

and failure of concrete structures. This study is concerned with bonding at the interfaces

between phases, porosity and directional alignment of constituents in all of the

composite material.

1.3 Aim

The main aims of this research are to identify and present the application of

polymer in concrete construction.

1.4 Objectives

The objectives of this work are :

i) To study the application of polymer in concrete construction.

ii) To determine the advantage and disadvantage of polymer.

iii) To investigate the problems in the use of the polymer as repair materials in

concrete construction.

4

1.5 Scope of Research

The scope of research for this project involves the discussion of 3 case studies

conducted in Kuala Lumpur and Selangor areas. These cases are about the development

of medium and high rise buildings for commercial or residential purpose. The discussion

comprises of the site conditions, selection of polymer system, the polymer system used

and also some of the main issue in the cases. At later stage, comparisons between these

case studies are made. Conclusions are drawn from the literature reviews and case

studies conducted.

5

CHAPTER 2

LITERATURE REVIEW

2.1 Introduction

Concrete today is an indispensable part of the fabric of modern society, used for

everything from mundane road pavements and high rise building structures. Despite its

long history of use, our understanding of the material has only really developed in

very recent times, particularly with respect to its durability. There was common view

that concrete is a durable as well as a maintenance-free constructional material. In recent

years this concept has been changed. Many investigations have shown that concrete does

not perform as well as it was expected due to the effect of many factors which contribute

to or cause the deterioration of concrete structures. The causes of deterioration, repair

materials and techniques are described in brief in this section.

2.2 Concrete Problems

Concrete does not necessary perform as we would like. Common causes of

distress and deterioration of concrete are listed in Table 2.1. Causes of concrete

problems can be classified as:

i) Defects: design, materials, construction

ii) Damage: overload, fire, impact, chemical spill

6

iii) Deterioration: metal corrosion, erosion, freeze/thaw, sulfate attacks

When the concrete structure is newly taken into service there may occur damage

which is attributable to unsatisfactory construction practice. The damage may have an

immediate effect on the structural integrity, such as in the case of voids in walls of

which there may be no visible evidence - concealed defects. Poor construction usually

leads to reduced durability which will manifests itself in later years. The working life of

the structure may be reduced or extensive maintenance may be required as a result of

deterioration of materials, usually steel subject to corrosion attack or concrete subject to

aggressive chemicals. Evidence of this type of damage may appear after 15 or 20 years

and is strongly environment dependent. Corrosion may be detectable at an early stage

and prior to serious damage occurring to the extent that the functionality of the structure

is affected [1].

Table 2.1 : Causes of Distress and Deterioration of Concrete [2]

Causes of Distress and Deterioration of Concrete

Accidental Loadings Chemical Reactions Acid Attach

Aggressive-water attach Alkali-carbonate rock reaction Alkali-silica reaction

Miscellaneous chemical attach Sulfate attach Construction Errors

Corrosion of Embedded Metals Design Errors Inadequate structural design

Poor design details Erosion Abrasion

Cavitation Freezing and Thawing Settlement and Movement

Shrinkage Plastic Drying

Temperature Changes Internally generated Externally generated

Fire Weathering

7

2.2.1 Construction Errors

Poor construction practices and negligence can cause defects that lead to the

cracking and concrete deterioration. These include:

i) Scaling, crazing and dusting of concrete

ii) Improper alignment of formwork

iii) Improper consolidation

iv) Movement of formwork

v) Improper location of reinforcing steel

vi) Premature removal of shores or reshores

vii) Improper curing

Errors made during construction such as adding improper amounts of water to

the concrete mix, inadequate consolidation, and improper curing can cause distress and

deterioration of the concrete. Proper mix design, placement, and curing of the concrete,

as well as an experienced contractor are essential to prevent construction errors from

occurring. Construction errors can lead to some of the problems discussed later in this

section such as scaling and cracking. Honeycombing and bugholes can be observed after

construction.

Honeycombing can be recognized by exposed coarse aggregate on the surface

without any mortar covering or surrounding the aggregate particles. The honeycombing

may extend deep into the concrete. Honeycombing can be caused by a poorly graded

concrete mix, by too large of a coarse aggregate, or by insufficient vibration at the time

of placement. Severe honeycombing should be repaired to prevent further deterioration

of the concrete surface [1].

Bugholes is a term used to describe small holes (less than about 0.25 inch in

diameter) that are noticeable on the surface of the concrete. Bugholes are generally

caused by too much sand in the mix, a mix that is too lean, or excessive amplitude of

8

vibration during placement. Bugholes may cause durability problems with the concrete

and should be monitored [1].

2.2.2 Design Errors

The design errors can be broadly categorised into two types:

a) Inadequate structural design

The failure mechanism is due to over stressing the concrete beyond its capacity.

These defects will be manifested in the concrete either by cracking or spalling. If the

concrete experiences high compressive stresses then spalling will occur. Similarly if the

concrete is exposed to high torsional or shearing stresses then spalling or cracking may

occur and high tensile stresses will cause the concrete to crack. Such defects will be

present in the areas where high stresses are expected. Through visual inspection, the

engineer should decide whether to proceed for a detailed stress analysis. A thorough

petrographic analysis and strength evaluation will be required if rehabilitation is

considered to be necessary. These problems can be prevented with a careful review of

the design calculations and detailing [1].

b) Poor design details

An adequate design does not guarantee a satisfactory function without including

design detailing. Detailing is an important component of a structural design. Poor

detailing may or may not directly lead to a structural failure but it may contribute to the

deterioration of the concrete. In order to fix a detailing defect it is necessary to correct

the detailing and not to respond to the symptoms only [1]. Some of the general design

and detailing defects include:

i) Abrupt changes in section

ii) Insufficient reinforcement at reentrant corners and openings

iii) Inadequate provision for deflection

9

iv) Inadequate provisions for drainage

v) Inadequate expansion joints

vi) Material incompatibility 2.2.3 Disintegration and Scaling

Disintegration can be described as the deterioration of the concrete into small

fragments and individual aggregates. Scaling is a milder form of disintegration where

the surface mortar flakes off. Large areas of crumbling (rotten) concrete, areas of

deterioration which are more than about 3 to 4 mm deep (depending on the wall/slab

thickness), and exposed rebar indicate serious concrete deterioration. If not repaired, this

type of concrete deterioration may lead to structural instability of the concrete structure.

Disintegration can be result from many causes such as, chemical attack, and poor

construction practices. Concrete with the proper amounts of air, water, and cement, and

a properly sized aggregate, will be much more durable. In addition, proper drainage is

essential in preventing freeze-thaw damage. When critically saturated concrete (when

90% of the pore space in the concrete is filled with water) is exposed to freezing

temperatures, the water in the pore spaces within the concrete expand, damaging the

concrete [3].

2.2.4 Spalling and Popouts

Spalling is the loss of larger pieces or flakes of concrete. It is typically caused by

sudden impact of something dropped on the concrete or stress in the concrete that

exceeded the design. Spalling may occur on a smaller scale, creating popouts. Popouts

are formed as the water in saturated coarse aggregate particles near the surface freezes,

expands, and pushes off the top of the aggregate and surrounding mortar to create a

shallow conical depression. Popouts are typically not a structural problem [3].

10

2.2.5 Steel Reinforcement Corrosion

Corrosion presents a problem for reinforced concrete structures for two reasons:

i) As corrosion occurs, there is a corresponding drop in the cross-sectional area of

the steel reinforcement; and,

ii) The corrosion products occupy a larger volume than steel, and therefore exert

substantial tensile forces on the surrounding concrete.

The expansive forces caused by rebar corrosion can cause cracking and spalling

of the concrete, and therefore loss of structural bond between the rebar and concrete.

Thus, the structural safety of RC members will be reduced either by the loss of bond or

by the loss of rebar cross-sectional area.

Concrete typically is a very alkaline environment, with pH values between 12

and 13.5. Therefore, since concrete is a naturally passivating environment, rebar is very

well protected from corrosion in most reinforced concrete structures. Whether corrosion

occurs or not depends on a large number of factors, including the electrode potentials,

temperature, pH, concrete material properties, and the concentration and distribution of

moisture, oxygen, aggressive species (chlorides, carbon dioxide), reactants and products.

Corrosion occurs when the passivating environment of the concrete is destroyed. This is

most commonly caused by the presence of aggressive

species, such as carbon dioxide and/or chlorides [4].

a) Chloride-induced corrosion

The presence of chloride ions (Cl-) near steel rebar is generally believed to be the

main cause of premature corrosion in concrete structures. Chloride ions are very

common in nature, and are an extremely aggressive species. The diffusion of chlorides

into concrete from an external source is the major cause of rebar corrosion in most parts

of the world. It is believed that chloride ions destroy the protective passive film on the

surface of the rebar, thereby increasing susceptibility to corrosion. There is a chloride

11

threshold for corrosion, and it is typically approximated to a concentration of 0.4%

chlorides by weight of cement if chlorides are cast into the concrete, and 0.2% if the

chlorides diffuse into the concrete. The reason that a higher threshold exists with cast-in

chlorides is that many of these chlorides are bound into the structure of the cement paste,

and are unavailable to react. An often quoted threshold is one pound of chlorides per

cubic yard of concrete [4].

b) Carbonation-induced corrosion

Carbon dioxide in the air can cause corrosion of embedded steel through a

process known as carbonation. In this process, carbon dioxide gas dissolves in the pore

water to form carbonic acid, which in turn reacts with the hydroxides in the pore

solution which are alkaline. Once these hydroxides are consumed, the pH of the pore

solution will fall to a level (< 9) where corrosion of the steel can occur. Corrosion due to

carbonation is most common when the cover to reinforcement is low. It can occur at

greater depths if the pore structure is large and interconnected, allowing for easy

diffusion of carbon dioxide gas to the steel. Carbonation is most common on older

buildings constructed of concrete with a low cement content. Wet/dry cycling can

accelerate carbonation by allowing carbon dioxide in during the dry phase, and

providing the water to dissolve it during the wet phase. Rebar corrosion in reinforced

concrete balconies is often caused by carbonation, due to their thin cross-sections, and

high susceptibility for rain wetting [4].

2.3 Cracks in Concrete

All concrete structures crack. Cracks in concrete have many causes. They may

affect the appearance only or indicate significant structural distress or lack of durability.

The significance of cracks depends on the type of the structure. To properly repair

cracks, the cause of the problem must be addressed, otherwise only temporary solution

will be achieved [5].

12

Concrete can crack in any or in each of the following three phases of its life,

namely:

i) Plastic-phase while it has still not set

ii) Hardening-phase while if is still green

iii) Hardened-phase and in service

In its plastic-condition (before it has set), the concrete can crack due to

i) Plastic shrinkage

ii) Plastic settlement

iii) Differential settlement of staging supports

In its hardening-phase (three to four weeks after setting), concrete can crack due to:

i) Constraint to early thermal movement

ii) Constraint to early drying shrinkage

Differential settlement of supports

In its hardened-state and in service (after 28 days), the concrete can crack due to:

i) Overload

ii) Under-design

iii) Inadequate construction

iv) Inadequate detailing

v) Differential settlement of foundations

vi) Sulphate attack on cement in concrete

vii) Corrosion of steel reinforcement

(a) Chloride attack on reinforcement

(b) Carbonation effect on concrete

(c) Simple oxidation of reinforcement due to exposure to moisture

viii) Alkali-aggregate reaction

ix) Fabrication, shipment and handling cracks in precast concrete members

x) Crazing

xi) Weathering cracks

xii) Long term drying-shrinkage cracks

13

Cracks in the concrete may classified as structural or surface cracks. (i) Surface

cracks are generally less than a few millimeters wide and deep. These are often called

hairline cracks and may consist of single, thin cracks, or cracks in a craze/map-like

pattern. A small number of surface or shrinkage cracks is common and does not usually

cause any problems. Surface cracks can be caused by freezing and thawing, poor

construction practices, and alkali-aggregate reactivity. Alkali-aggregate reactivity occurs

when the aggregate reacts with the cement causing crazing or map cracks. The

placement of new concrete over old may cause surface cracks to develop. This occurs

because the new concrete will shrink as it cures. (ii) Structural cracks in the concrete are

usually larger than 3 mm in width. They extend deeper into the concrete and may extend

all the way through a wall, slab, or other structural member. Structural cracks are often

caused by overloads. The structural cracks may worsen in severity due to the forces of

weathering [5].

2.4 Repair of Concrete Structures

Repair of reinforced concrete involves treatment, after defects have occurred, to

restore the structure to an acceptable condition. Defects cause some compromise in

condition or function relative to the original, and this generally means that a process or

processes have resulted in movement, loss of material, and/or loss in materials properties.

Repairs are therefore mostly reactive, and initiated when evidence of deterioration

becomes apparent.

2.4.1 Evaluation of Concrete

A through and logical evaluation of the current condition of a concrete structure

is the first step in any repair project. The evaluation of the condition of concrete

structures (for the purpose of identifying and defining areas of distress) is possible by

14

following guidelines. However, following the guide does not eliminate the need for

intelligent observations and use of sound judgement.

Regular inspection and monitoring is essential to detect problems with concrete

structures. The structures should be inspected a minimum of once per year. It is

important to keep written records of the dimensions and extent of deterioration as

scaling, disintegration, efflorescence, honeycombing, erosion, spalling, popouts, and the

length and width of cracks. Structural cracks should be monitored more frequently and

repaired if they are a threat to the stability of the structure. Photographs provide

invaluable records of changing conditions. All maintenance and inspection records

should be kept.

2.4.3 Selection of Repair System

Once it has been agreed that repairs are needed to meet the remaining life

required of a structure, the types of repair that may be appropriate can be selected.

However, there is a large range of options dependant on what the repair is meant to do,

and how long it is to last. The purpose of a concrete repair system can be one of, or

combinations of, the following:

i) To restore structural integrity

ii) To arrest deterioration

iii) To prevent future deterioration

iv) To restore original profile

v) To restore integrity of sealed system e.g. waterproofing

vi) Aesthetic appearance

It is generally accepted that repair materials should be selected to provide the

best compromise of the properties required, and may be further influenced by the

15

funding available, availability of materials, and technical or other constraints such as

application techniques and environment of working [6].

2.4.4 Conventional repair materials and systems

There are many variables in past and present repair materials and systems. These

include the technique or form of repairs, material composition, method of application,

fresh properties and set properties. This project deals mainly with patch repair materials

for concrete substrates. For the purposes of this project, patch repairs are defined as

those applied to substrate concrete and contained within an element, and are typically

less than 1 m2 in area and less than 100mm in depth. However, where patch repair

systems include additional components such as bonding and finishing coats, these are

also considered. The components of a full repair system as below [6]:

i) Coating for reinforcing steel

ii) Bonding agent

iii) Repair mortar(s)

iv) Fairing coat (to level irregularities between the repair and the retained area of un-

repaired concrete)

v) Decorative/protective coating (to conceal the repair and create a uniform overall

appearance)

The generic types of concrete repair materials available are summarized in Table

2.2. The current range of generically different systems for patch repair as including resin

mortars, polymer modified cementitious mortars and cementitious mortars, as shown in

Table 2.3. Common properties of the materials are shown in Table 2.4. These generic

types of materials cover a multitude of proprietary materials.

Patch repair materials with cementitious-only binders can provide acceptable

protection to existing concrete structures. The set properties are strongly influenced by

16

the cement content and water/binder ratio. The performance or application parameters

are often enhanced with the addition of polymers.

Table 2.2 : Composition of concrete repair systems [5]

Component or type of

system

Type of material

Cement only systems

Polymer-modified

cementitious systems

Resin repair materials

Fibres

OPC, SRPC, RHPC, White Portland

Magnesium Phosphate

Others (alkali activated, gypsum-based cements)

Supplementary cementing materials (pfa, ggbs, sf, mk)

Synthetic rubbers, eg styrene butadiene rubber

Acrylic and modified acrylic latexes

Polyvinyl acetate latexes

Epoxy emulsions

Epoxy resins

Polyester resins

Acrylic resins

Glass

Steel wire (mild, stainless, hooked, crimped etc.)

Polypropylene (polypropylene or homopolymer resin).

Monofilament, fibrillated

Acrylic (monomers and monomer blends etc.)

17

Table 2.3 : Categories of systems for concrete patch repair [5]

Resinous materials Polymer modified

Cementitious materials

Cementitious materials

Epoxy mortar

Polyester mortar

Acrylic mortar

S.B.R modified

Vinyl acetate modified

Magnesium phosphate

modified

OPC/sand

HAC

Flowing

Table 2.4 : Application methods and properties of concrete repair materials [5]

Application method Properties

Hand trowelled

Hand packed

Poured in shuttering

Sprayed

Self-levelling

Self-compacting

Thixotropic

High build

Lightweight

Rapid set

2.5 Introduction to Polymers

Polymers are a large class of materials consisting of many small molecules

(called monomers) that can be linked together to form long chains, thus they are known

as macromolecules. A typical polymer may include tens of thousands of monomers.

Because of their large size, polymers are classified as macromolecules. Humans have

taken advantage of the versatility of polymers for centuries in the form of oils, tars,

resins, and gums [7].

However, it was not until the industrial revolution that the modern polymer

industry began to develop. In the late 1830s, Charles Goodyear succeeded in producing a

18

useful form of natural rubber through a process known as "vulcanization." Some 40

years later, Celluloid (a hard plastic formed from nitrocellulose) was successfully

commercialized. Despite these advances, progress in polymer science was slow until the

1930s, when materials such as vinyl, neoprene, polystyrene, and nylon were developed.

The introduction of these revolutionary materials began an explosion in polymer

research that is still going on today [7].

Unmatched in the diversity of their properties, polymers such as cotton, wool,

rubber and all plastics are used in nearly every industry. Natural and synthetic polymers

can be produced with a wide range of stiffness, strength, heat resistance, density, and

even price. With continued research into the science and applications of polymers, they

are playing an ever increasing role in society [7].

2.6 Polymer Modified Concrete

Although its physical properties and relatively low cost make it the most widely

used construction material, conventional Portland cement concrete has a number of

limitations, such as low flexural strength, low failure strain, susceptibility to frost

damage and low resistance to chemicals. These drawbacks are well recognized by the

engineer and can usually be allowed for in most applications. In certain situations, these

problems can be solved by using materials which contain an organic polymer or resin

(commercial polymer) instead of or in conjunction with Portland cement. These

relatively new materials offer the advantages of higher strength, improved durability,

good resistance to corrosion and reduced water permeability.

There are three principal classes of composite materials containing polymers:

polymer impregnated concrete; polymer cement concrete and polymer concrete. The

distinction between these three classes is important to the design engineer in the

selection of the appropriate material for a given application.

19

The typical properties of these polymer-containing composites are compared

with those of conventional Portland cement concrete in Table 2.5. Their general

characteristics and applications are summarized in Table 2.6.

Table 2.5 : Typical Properties of Polymer-Containing Concrete Composites And

Portland Cement Concrete [8]

Material Tensile

Strenght

(MPa)

Modulus

Of

Elasticity

(GPa)

Compressive

Strenght

(MPa)

Shear

Bond

Strenght

(KPa)

Water

Sorption

(%)

Acid

Resistance

Polymer

Impregnated

Concrete

10.5 42 140 - 0.6 10

Polymer

Cement

Concrete

5.6 14 38 >4550 - 4

Portland

Cement

Concrete

2.5 24.5 35 875 5.5 -

Table 2.6 : General Characteristics And Applications of Polymer-Modified Concretes [8]

Polymer Impregnated Concrete

General

Characteristics

Consists generally of a pre-cast concrete, which has been dried then

impregnated with a low viscosity monomer that polymerizes in situ

to form a network within the pores. Impregnation results in

markedly improved strength and durability in comparison with

conventional concrete.

20

Table 2.6 : ( Continued ) Principal

Applications

Principal applications include use in structural steel floors, food

processing buildings, sewer pipes, storage tanks for seawater,

desalination plants and distilled water plants, wall panels, tunnel

liners and swimming pools.

Remark The disadvantage is the relatively high cost, as the polymer is more

expensive than cement and the production process is more

complicated.

Polymer cement concrete

General

Characteristics

Products made with thermosetting polymers and polymer latex

have greater mechanical strength, markedly better resistance to

penetration by water and salt, and greater resistance to freeze-thaw

damage than Portland cement concrete; excellent bonding to steel

reinforcing and to old concrete.

Principal

Applications

Major applications are in floors, bridge decks, road surfacing and

compounds for repair of concrete structures. Latex modified mortar

is used for laying bricks, in prefabricated panels and in stone.

Remark The mixing and handling are similar to Portland cement concrete.

However, in the production process, air entrainment occurs without

the use of an admixture, and prolonged moist curing is not required.

2.6.1 Polymer Impregnated Concrete

Polymer impregnated concrete is made by impregnation of pre-cast hardened

Portland cement concrete with low viscosity monomers (in either liquid or gaseous form)

that are converted to solid polymer under the influence of physical agents (ultraviolet

21

radiation or heat) or chemical agents (catalysts). It is produced by drying conventional

concrete; displacing the air from the open pores (by vacuum or monomer displacement

and pressure); saturating the open pore structure by diffusion of low viscosity monomers

or a pre-polymer-monomer mixture (viscosity 10 cps; 1 x 10-2 Pas); and in-situ

polymerization of the monomer or pre-polymer-monomer mixture, using the most

economical and convenient method (radiation, heat or chemical initiation). The

important feature of this material is that a large proportion of the void volume is filled

with polymer, which forms a continuous reinforcing network. The concrete structure

may be impregnated to varying depths or in the surface layer only, depending on

whether increased strength and/or durability is sought. The main disadvantages of

polymer impregnated concrete products are their relatively high cost, as the monomers

used in impregnation are expensive and the fabrication process is more complicated than

for unmodified concrete [8].

Impregnation of concrete results in a remarkable improvement in tensile,

compressive and impact strength, enhanced durability and reduced permeability to water

and aqueous salt solutions such as sulfates and chlorides. The compressive strength can

be increased from 35 MPa to 140 MPa, the water sorption can be reduced significantly.

And the freeze-thaw resistance is considerably enhanced. The greatest strength can be

achieved by impregnation of auto-claved concrete. This material can have a

compressive-strength-to-density ratio nearly three times that of steel. Although its

modulus of elasticity is only moderately greater than that of non-autoclaved polymer

impregnated concrete, the maximum strain at break is significantly higher [8].

The monomers most widely used in the impregnation of concrete are the vinyl

type, such as methyl methacrylate (MMA), styrene, acrylonitrile, t-butyl styrene and

vinyl acetate. Acrylic monomer systems such as methyl methacrylate or its mixtures

with acrylonitrile are the preferred impregnating materials, because they have low

viscosity, good wetting properties, high reactivity, relatively low cost and result in

products with superior properties. By using appropriate bifunctional or polyfunctional

monomers (cross-linking agents) in conjunction with MMA, a cross-linked network is

22

formed within the pores, resulting in products with greatly increased mechanical

strength and higher thermal and chemical resistance. Improvement of these properties

will depend on the degree of cross-linking. A cross-linking agent commonly used with

vinyl monomers such as MMA and styrene is trimethylolpropane trimethacrylate [8].

Thermosetting monomers and pre-polymers are also used to produce polymer

impregnated concrete with greatly increased thermal stability (i.e. resistance to

deterioration by heat). These include epoxy pre-polymers and unsaturated polyester-

styrene. These monomers and pre-polymers are relatively viscous and, therefore, their

use results in reduced impregnation. Their viscosity can be reduced by mixing them with

low-viscosity monomers such as MMA [8].

Applications of concrete impregnated in depth in building and construction

include structural floors, high performance structures, food processing buildings, sewer

pipes, storage tanks for seawater, desalination plants and distilled water plants. Marine

structures, wall panels, tunnel liners, prefabricated tunnel sections and swimming pools.

Partially impregnated concrete is used for the protection of bridges and concrete

structures against deterioration and repair of deteriorated building structures, such as

ceiling slabs, underground garage decks and bridge decks [8].

2.6.2 Polymer Cement Concrete

Polymer cement concrete is a modified concrete in which part (10 to 15% by

weight) of the cement binder is replaced by a synthetic organic polymer. It is produced

by incorporating a monomer, pre-polymer-monomer mixture, or a dispersed polymer

(latex) into a cement-concrete mix. To effect the polymerization of the monomer or pre-

polymer-monomer, a catalyst is added to the mixture. The process technology used is

very similar to that of conventional concrete. Therefore, polymer cement concrete can be

23

cast-in-place in field applications, whereas polymer impregnated concrete has to be used

as a pre-cast structure [8].

The properties of polymer cement concrete produced by modifying concrete with

various polymers range from poor to quite favorable. Poor properties of certain products

have been attributed to the incompatibility of most organic polymers and monomers

with some of the concrete mix ingredients. Better properties are produced by using pre-

polymers, such as unsaturated polyester cross-linked with styrene or epoxies. To achieve

a substantial improvement over unmodified concrete, fairly large proportions of these

polymers are required. The improvement does not always justify the additional cost [8].

Modification of concrete with a polymer latex (colloidal dispersion of polymer

particles in water) results in greatly improved properties, at a reasonable cost. Therefore,

a great variety of latexes is now available for use in polymer cement concrete products

and mortars. The most common latexes are based on poly (methyl methacrylate) also

called acrylic latex, poly (vinyl acetate), vinyl chloride copolymers, poly (vinylidene

chloride), (styrene-butadiene) copolymer, nitrile rubber and natural rubber. Each

polymer produces characteristic physical properties. The acrylic latex provides a very

good water-resistant bond between the modifying polymer and the concrete components,

whereas use of latexes of styrene-based polymers results in a high compressive strength

[8].

Curing of latex polymer cement concrete is different from that of conventional

concrete, because the polymer forms a film on the surface of the product. Retaining

some of the internal moisture needed for continuous cement hydration. Due to the film-

forming feature, moist curing of the latex product is generally shorter than for

conventional concrete [8].

Generally, polymer cement concrete made with polymer latex exhibits excellent

bonding to steel reinforcement and to old concrete. Its flexural strength and toughness

24

are usually higher than those of unmodified concrete. The modulus of elasticity may or

may not be higher than that of unmodified concrete, depending on the polymer latex

used. For example, the more rubbery the polymer. Generally, as the polymer forms a

low modulus phase with the polymer cement concrete, the creep is higher than that of

plain concrete and decreases with the type of polymer latex used in the following order:

polyacrylate; styrene-butadiene copolymer; polyvinylidene chloride; unmodified cement

[8].

The drying shrinkage of polymer cement concrete is generally lower than that of

conventional concrete; the amount of shrinkage depends on the water-to-cement ratio,

cement content, polymer content and curing conditions. It is more susceptible to higher

temperatures than ordinary cement concrete. For example, creep increases with

temperature to a greater extent than in ordinary cement concrete, whereas flexural

strength, flexural modulus and modulus of elasticity decrease. These effects are greater

in materials made with elastomeric latex (e.g., styrene-butadiene rubber) than in those

made with thermoplastic polymers (e.g., acrylic). Typically, at about 45C, polymer

cement concrete made with a thermoplastic latex retains only approximately 50 percent

of its flexural strength and modulus of elasticity [8].

The main application of latex-containing polymer cement concrete is in floor

surfacing, as it is non-dusting and relatively cheap. Because of lower shrinkage, good

resistance to permeation by various liquids such as water and salt solutions, and good

bonding properties to old concrete, it is particularly suitable for thin (25 mm) floor

toppings, concrete bridge deck overlays, anti-corrosive overlays, concrete repairs and

patching [8].

25

2.7 Polymer Concrete

Polymer concrete (PC) is a composite material in which the binder consists

entirely of a synthetic organic polymer. It is variously known as synthetic resin concrete,

plastic resin concrete or simply resin concrete. Because the use of a polymer instead of

Portland cement represents a substantial increase in cost, polymers should be used only

in applications in which the higher cost can be justified by superior properties, low labor

cost or low energy requirements during processing and handling. It is therefore

important that architects and engineers have some knowledge of the capabilities and

limitations of PC materials in order to select the most appropriate and economic product

for a specific application [9].

2.7.1 Nature and General Properties

Polymer concrete consists of a mineral filler (for example, an aggregate) and a

polymer binder (which may be a thermoplastic, but more frequently, it is a thermosetting

polymer. When sand is used as a filler, the composite is referred to as a polymer mortar.

Other fillers include crushed stone, gravel, limestone, chalk, condensed silica fume

(silica flour, silica dust), granite, quartz, clay, expanded glass, and metallic fillers.

Generally, any dry, non-absorbent, solid material can be used as a filler.

To produce PC, a monomer or a pre-polymer (i.e., a product resulting from the

partial polymerization of a monomer), a hardener (cross-linking agent) and a catalyst are

mixed with the filler. Other ingredients added to the mix include plasticizers and fire

retardants. Sometimes, silane coupling agents are used to increase the bond strength

between the polymer matrix and the filler. To achieve the full potential of polymer

concrete products for certain applications, various fiber reinforcements are used. These

include glass fiber, glass fiber-based mats, fabrics and metal fiber. Setting times and

times for development of maximum strength can be readily varied from a few minutes to

26

several hours by adjusting the temperature and the catalyst system. The amount of

polymer binder used is generally small and is usually determined by the size of the filler.

Normally the polymer content will range from 5 to 15 percent of the total weight, but if

the filler is fine, up to 30 percent may be required [9].

Polymer concrete composites have generally good resistance to attack by

chemicals and other corrosive agents, have very low water sorption properties, good

resistance to abrasion and marked freeze-thaw stability. Also, the greater strength of

polymer concrete in comparison to that of Portland cement concrete permits the use of

up to 50 percent less material. This puts polymer concrete on a competitive basis with

cement concrete in certain special applications. The chemical resistance and physical

properties are generally determined by the nature of the polymer binder to a greater

extent than by the type and the amount of filler. In turn, the properties of the matrix

polymer are highly dependent on time and the temperature to which it is exposed [9].

The viscoelastic properties of the polymer binder give rise to high creep values.

This is a factor in the restricted use of PC in structural applications. Its deformation

response is highly variable depending on formulation; the elastic moduli may range from

20 to about 50 GPa, the tensile failure strain being usually 1%. Shrinkage strains vary

with the polymer used (high for polyester and low for epoxy-based binder) and must be

taken into account in an application [9].

A wide variety of monomers and pre-polymers are used to produce PC. The

polymers most frequently used are based on four types of monomers or pre-polymer

systems: methyl methacrylate (MMA), polyester pre-polymer-styrene, epoxide pre-

polymer hardener (cross-linking monomer) and furfuryl alcohol. The typical range of

properties of PC products made with each of these four polymers is presented in Table

2.7. General characteristics and principal applications are described in Table 2.8.

27

Table 2.7 : Typical Range of Properties of Common PC Products and Portland Cement

Concrete [9]

Type of

Binder

Density

(kg/dm)

Water

Sorption

(%)

Compressive

Strength,

(MPa)

Tensile

Strength

(MPa)

Flexural

Strength

(MPa)

Modulus

of

Elasticity

(GPa)

Poly(methyl

methacrylate) 2.0-2.4

0.05-

0.60 70-210 9-11 30-35 35-40

Polyester 2.0-2.4 0.30-1.0 50-150 8-25 15-45 20-40

Epoxy 2.0-2.4 0.02-1.0 50-150 8-25 15-50 20-40

Furan

polymer 1.6-1.7 0.20 48-64 7-8 - -

Portland

Cement

Concrete

1.9-2.5 5-8 13-35 1.5-3.5 2-8 20-30

Table 2.8 : General Characteristics And Applications of Polymer Concrete Products [9]

Poly (methylmethacrylate)

General

Characteristics

Low tendency to absorb water; thus high freeze-thaw resistance;

low rate of shrinkage during and after setting; very good chemical

resistance and outdoor durability.

Typical

Applications

Used in the manufacture of stair units, faade plates, sanitary

products for curbstones.

Polyester

General

Characteristics

Relatively strong, good adhesion to other materials, good chemical

and freeze-thaw resistance, but have high-setting and post-setting.

28

Table 2.8 : ( Continued ) Typical

Applications

Because of lower cost, widely used in panels for public and

commercial buildings, floor tiles, pipes, stairs, various precast and

cast-in applications in construction works.

Epoxy

General

Characteristics

Strong adhesion to most building materials; low shrinkage; superior

chemical resistance; good creep and fatigue resistance; low water

sorption.

Typical

Applications

Epoxy polymer products are relatively costly; they are mainly used

in special applications, including use in mortar for industrial

flooring, skid-resistant overlays in highways, epoxy plaster for

exterior walls and resurfacing of deteriorated structures.

Furan-based polymer

General

Characteristics

Composite materials with high resistance to chemicals (nost acidic

or basic aqueous media), strong resistance to polar organic liquids

such as ketones, aromatic hydrocarbons, and chlorinated

compounds.

Typical

Applications

Furan polymer mortars and grouts are used for brick (e.g. carbon

brick, red shale brick, etc.) floors and linings that are resistant to

chemicals, elevated temperatures and thermal shocks.

2.7.2 Acrylic Polymer Concrete

The most common acrylic polymer is poly (methyl methacrylate) (PMMA),

obtained by polymerization of methyl methacrylate (MMA). PC made with this acrylic

29

polymer as a binder is a versatile material, has excellent weathering resistance, good

waterproofing properties, good chemical resistance, and relatively low setting shrinkage

(0.01 to 0.1%); its coefficient of thermal expansion is equivalent to that of Portland

cement concrete. Because of its very low tendency to absorb water, acrylic PC has a

very high freeze-thaw resistance. The low flash point (11C) of the MMA monomer is a

disadvantage, however as it constitutes a safety problem [9].

Although the MMA monomer is more expensive than the prepolymer-monomer

used in the more popular polyester PC, its unique properties account for its use in a great

many diverse applications, including the manufacture of stair units, sanitary products,

curbstones, and faade plates. A highly successful development has been its use as a

rapid-setting, structural patching material for repairing large holes in bridge decks. The

material consists of a highway grade aggregate and a matrix produced by cross-linking

MMA with trimethylol propane trimethacrylate (TMPTMA) [9].

2.7.3 Polyester Polymer Concrete

Because of low cost, the most widely used polymer-binders are based on

unsaturated polyester polymer. In most applications, the polyester binder is a general

purpose, unsaturated polyester pre-polymer formulation. These formulations are

available in the form of 60 to 80 percent solutions of the pre-polymer in

copolymerizable monomers such as styrene and styrene-methyl methacrylate. During

hardening, the polyester pre-polymer and the monomer react through their unsaturated

groups (double bonds). The chemical reaction is called cross-linking, the production

process associated with it is referred to as curing, and the resulting polymer binder is a

thermosetting polymer [9].

Polyester PC has good mechanical strength, relatively good adhesion to other

materials, and good chemical and freeze-thaw resistance. It has, however large setting

30

and post-setting shrinkage (up to ten times greater than Portland cement concrete), a

serious disadvantage in certain applications. Polyester PC is used in various pre-cast and

cast-in place applications in construction works, public and commercial buildings, floor

tiles, sewer pipes and stairs [9].

2.7.4 Epoxy Polymer Concrete

Epoxy binder like polyester, is a thermosetting polymer The epoxy polymer can

be hardened with a variety of curing agents, the most frequently used being polyamines

(e.g., tertiary polyamines). The use of polyamine hardeners (curing agents) results in PC

products with the highest chemical resistance. Other curing agents are polyamides and

polysulfide polymers. Epoxy PC products cured with polyamides have greater flexibility,

better heat resistance, and reduced chalking tendency in outdoor exposure, but their

solvent and chemical resistance is lower than for similar products cured with polyamines.

The use of polysulfide polymers produces epoxy PC with even greater flexibility [9].

Epoxy PC exhibits high strength adhesion to most materials, low-setting and

post-setting shrinkage, high chemical resistance, and good fatigue and creep resistance.

Because they are relatively expensive, epoxy polymers have not been used very widely

as binders in PC products. Therefore, epoxy PC is used for special applications, in

situations in which the higher cost can easily be justified, such as mortar for industrial

flooring to provide physical and chemical resistance, skid-resistant overlays (filled with

sand, emery, pumice, quartz) in highways, epoxy plaster for exterior walls (e.g., in

exposed aggregate panels) and resurfacing material for deteriorated areas (e.g., in

flooring). Epoxy PC reinforced with glass, carbon or boron fibers is used in the

fabrication of translucent panels, boat hulls and automobile bodies [9].

31

2.7.5 Furan Polymer Concrete

Furan polymers are based on furfuryl alcohol, which is derived from agricultural

residues such as corn cobs, rice hulls, oat hulls or sugar cane bagasse. The furan pre-

polymer is usually cross-linked with furfuryl alcohol, furfuraldehyde or formaldehyde to

yield thermosetting polymers, highly resistant to most aqueous acidic or basic solutions

and strong solvents such as ketones, aromatics, and chlorinated compounds. The furan

polymers are used as binders in mortars and grouts to achieve chemically resistant brick

floors (e.g., carbon brick and red shale brick) and linings. In addition to exhibiting

superior chemical resistance, these floors have excellent resistance to elevated

temperatures and extreme thermal shock.

2.8 General Patch Behavior

The first step in determining the proper repair material and repair application

method is to determine the conditions that the patch and the existing concrete will

experience over the life of the structure. Important considerations are temperature range,

load magnitude and duration, chemical environment, and whether the patch is aesthetic

or structural. Different patches will perform better in different conditions depending on

the material properties of the patch material. There is no one magical repair material.

Material selection should be a balance between the material properties of the concrete

substrate and repair material and the service conditions the member will experience [10].

2.8.1 Cleaning and Preparing Concrete Before Repair

Once the service conditions have been determined and the repair material has

been selected, the existing surface needs to be prepared so that an adequate bond can be

achieved. Different manufacturers of repair materials often have a list of approved

32

contractors that have been trained in the application of their product. Additionally, the

manufacturer will usually provide a recommended application procedure that includes

surface preparations. Whenever possible, it is recommended to use the manufacturers

method to limit the engineers liability on the project. In addition to the surface

preparation instructions supplied by the manufacturer, there are industry guides and

standards that should be followed. The following lists the appropriate standards and

guidelines:

i) ACI Guidelines Guide to Durable Concrete (ACI 201.2R)

ii) Causes, Evaluation and Repair of Cracks in Concrete Structures (ACI 224.1R)

iii) International Concrete Repair Institute Guidelines

The major concern of surface preparation is surface contaminants. Contaminants

may be defined as material, either liquid or solid that has the potential to cause adhesion,

curing, and/or application-related problems with coatings or patching materials as

applied to concrete. When dealing with impact damaged concrete beams, unsound

concrete and dust are also concerns. All unsound concrete at the surface of the patch

must be removed to insure adequate repair material bond. Damaged concrete should be

removed with a hammer and chisel (larger pieces) or a sandblaster (smaller pieces).

Never use a jackhammer or a scabbler because these large, heavy impact machines can

cause microcracks, or bruising, in the concrete. Loose dust or dirt on the surface is most

effectively removed with vacuum cleaning or oil-free compressed air [5].

At this time it is necessary to distinguish between surface preparation and

cleaning. Cleaning refers to the process of removing solvents and dust. Surface

preparation involves removing weakened surface layers, removing laitance, and

applying any bonding agent recommended by the manufacturer to provide a surface

profile adequate to achieve a good adhesive bond. Cleaning should always be performed

before surface preparation and immediately before patch material application. The

sequence of the procedure should be i) pre-clean, ii) surface preparation, and iii) final

clean [5].

33

It is essential that the patch and existing concrete systems perform as required in

the given service environment. The factors that control whether the system will perform

as required are material properties and quality construction methods. As the engineer, it

is our job to select the proper repair materials based on the requirements of the patch

system. Due to the nature of the cementitious, pre-packaged repair materials on the

market (high early strength, quick set times, and easy to apply), initial application of the

material is not a problem. The key to repairing concrete is guaranteeing the durability of

the repair system. In order to do that, the engineer must select a repair material with

properties compatible with the substrate. The difficulty with determining the material

properties that will insure a durable patch is that manufacturers often do not reveal all of

the constituents of the prepackaged repair materials. This presents a problem because

different constituents have different material properties and successful repair material

selection requires a compromise between the desired material properties. The material

properties in question are shrinkage, coefficient of thermal expansion, modulus of

elasticity, flexural strength, bond strength, and to a much lesser degree, compressive

strength.

Many repair materials are sold to repair engineers based solely on the

compressive strength and the rapid set times. This can be explained by the fact that in

most situations compressive strength is the most important concrete property. However,

nearly all impact damage to concrete beams occurs at the bottom of the beam. Because

of the location of the damage, compressive strength of the patch only affects the

durability and overall effectiveness of the system indirectly. The compatibility of the

patch material and substrate, however, is of consequence. Compatibility can be defined

as the balance of physical, chemical and electrochemical properties and dimensions

between the repair phase and the existing substrate phase of a repair system. The

difficult decision is to decide what is meant by compatible. However this thesis will

not include a discussion of the chemical properties of the repair systems [11].

34

When there is a significant difference in the coefficient of thermal expansion

between the repair patch and the substrate, problems can occur. The problem is that the

two materials try to move relative to each other when there is a temperature change. This

movement induces internal stresses within each material. Internal stresses can cause the

bond to break and cracks in the substrate or patch. When cracking occurs, several

problems arise. Cracks in the repair system may allow water to penetrate to the

reinforcement. This water, which may contain chlorides from deicing salts, can cause

two problems. Water expands when it freezes, and when it is in concrete, may widen

existing cracks. These cracks will lead to the deterioration of the patch, and ultimately to

its failure. Water, especially water that contains chloride ions, will cause corrosion in the

reinforcement. When the reinforcement corrodes, it loses effective section and also

expands. The loss of section obviously decreases structural capacity. As the rust builds

on the reinforcement and the reinforcement expands, cracks are formed and the bond

between the concrete and the rebar is lost [7].

Patch longevity is also affected by shrinkage. When the fresh patch material is

applied, the concrete substrate has achieved dimensional stability. If the patch material

shrinks too much as it cures, large internal stresses can occur. This will break the bond

between the two materials. For this reason it is desirable to use a patch material that has

low shrinkage. Proper curing can minimize shrinkage. Many manufacturers recommend

either wet curing with burlap and a moisture barrier around the patch for 2 to 7 days or

using curing compound. Some patch materials, however, are incompatible with curing

compounds. Incompatibility is also a problem when there is a mismatch in the modulus

of elasticity between the repair and substrate. This is especially critical when the repair

material is stiffer than the substrate. The stiffer patch will attract a larger portion of the

load. A stiffer patch (higher modulus of elasticity) will not deform as much as the

substrate and cause redistribution of the load. The redistribution of the load will focus

the stress on the interface between the patch and the substrate. The high stress on the

interface will eventually lead to a bond failure of the patch. Ideally, the patch should not

be as stiff (lower modulus of elasticity) as the substrate, because it will be in the tension

portion of the beam. This will allow the patch to elongate with applied load and decrease

35

stress concentration at the interface. However, the modulus of elasticity of the patch

cannot be too low. If it is too low, the patch may sag or creep [2].

From the above discussion it is apparent that when a repair material is selected,

care should be taken to match the material properties of the repair and the substrate. It is

possible to use a repair material that has different material properties than the substrate

as long as the bond strength is not weakened by the induced internal stresses and no

durability problems arise from cracking. The key is to ensure that the internal stresses do

not exceed the tensile stresses of the substrate, repair material, or the bond strength of

the interface.

36

CHAPTER 3

METHODOLOGY 3.1 Introduction

This research will be carried out in several construction projects in Kuala

Lumpur and Selangor. The construction projects selected are divided into new structure

and existing structure. The companies selected are Aston Star Sdn. Bhd, Sunway

Construction Sdn. Bhd, IJM Corporation Berhad and WCT Engineering Bhd. Figure 3.1

shows the research flow for the whole work to be carried out.

Literature search on application of polymer in concrete construction

Study in research method to be used

Select construction site

Collect data from manufacturer

Develop method of interview and site visit

Result and discussion

Prepare Presentation

Write report

Figure 3.1 : Research out flow

37

3.2 Steps in Conducting Case Study

Below are 5 essential steps in conducting the study :

3.2.1 Problem Statement Foundation

i) Understanding the project title.

ii) To identified the present polymer material used.

3.2.2 Literature Review

i) To study from library, website, journal and the need to research topic.

ii) Empirical study such as interview and get the information from polymer

material supplier and manufacturer.

3.2.3 Information and Data Collection

i) Select interview method and conducted interview in selected site.

3.2.4 Data Analysis

i) To identify the facts and compared the result with objective.

3.2.5 Conclusion

i) To make a conclusion to meet the terms of objective.

38

CHAPTER 4

RESULTS AND DISCUSSION

4.1 Case Study

The case studies being carried out by site visit and interview. There are 8 projects

selected for the case study. Table 4.1 shows the projects using polymer in concrete

construction. Each project using polymer material from the same manufacturer. This

study is limited to focus on application of polymer as a concrete repair material at

project Solaris Dutamas 2 only.

Table 4.1 : Projects using polymer in concrete construction

Item Company Projects Name Application Remark 1 IJM

Corporation Berhad

Menara Commerce, Jalan Raja Laut, Kuala Lumpur

Repair of high rise building structure.

New Structure

2 IJM Corporation Berhad

Park 7 Condominium, Seksyen 58, Persiaran KLCC, Kuala Lumpur

Repair of high rise building structure.

New Structure

3

IJM Corporation Berhad

The Troika Condominium, Seksyen 63, Jalan Binjai, Mukim Kuala Lumpur, Wilayah Persekutuan

Repair of high rise building structure.

New Structure

39

Table 4.1 : ( Continued )

4 Aston Star Sdn. Bhd.

Solaris Dutamas 2 Repair of high rise and low rise building structure.

New Structure

5 WCT Engineering Berhad

Middle Ring Road II - Karak to Jalan Taman Melati

Skid-resistant overlays in highways, bridge decks, road surfacing.

Existing Structure

6 WCT Engineering Berhad

The Curve Shopping Mall

Repair of commercial building structure.

Existing Structure

7 Sunway Construction Berhad

New Expansion of Sunway Pyramid Shopping Mall

Repair of commercial building structure.

Existing Structure

8 Sunway Construction Berhad

Menara Sunway

Repair of high rise building structure.

Existing Structure

Figured 4.1 shows the cause of concrete problem in the selected project sites.

The most cause of concrete problem is improper curing after the concreting which

covered 32%. The second is premature removal of formwork which is 20%. About 15%

cause by both overloading and shrinkage and 18% cause by overloading. The result

indicate that improper curing occured especially when spray curing compound is used,

some of the concrete surface may not properly being spray with the curing compound.

Due to time constraint, the contractor remove the formwork at an early stage.

Overloading happened normally in rebar fabrication yard which was done on the newly

constructed floor level..

40

Cause of Concrete Problems

32%

20%15%

18%

15%Improper curing

Premature removal offormworkOverloading

Rusty rebar

Shrinkage

Figured 4.1 : The cause of concrete problem in the selected project sites

Figure 4.2 shows the application of polymer in concrete construction. Polymer

used in selected the project sites can be classified as new structure, existing structure and

bridge. The typical application of polymer is used to repair concrete defects on columns,

beam and slab. From the figure, the application of polymer are more on beam for new

structure. For the existing structure and bridge, the application of polymer are more on

slab.

15%

26%

12%

48%

31%

42%37%

43% 46%

0%

10%

20%

30%

40%

50%

60%

New Structure ExistingStructure

Bridge

ColumnBeamSlab

Figure 4.2 : The application of polymer in concrete construction

41

Table 4.2 shows the repair system using polymer material and repair purpose in

every case study. This table indicate that bonding agent, coating of reinforcing steel and

repair mortar were commonly used in the new structure for Case Study 1 to 5. For

existing structure, application of repair works were more on protective to prevent future

deterioration.

Table 4.2 : Repair system and repair purpose

Case

Study Repair System Repair Purpose

1 Polymer bonding agent To restore original profile

2 Polymer coating for reinforcing steel To arrest deterioration

3 Polymer repair mortar To restore integrity of sealed system

4 Polymer bonding agent To restore structural integrity

5 Polymer repair mortar To restore structural integrity

6 Polymer protective coating To prevent future deterioration

7 Polymer protective coating To prevent future deterioration

8 Polymer decorative coating To prevent future deterioration

4.2 Project Solaris Dutamas 2

Solaris Dutamas 2 is an on going project located at Mont Kiara, Kuala Lumpur.

The project consists of the following :

i) 4 blocks of 6 storey shop office

ii) 1 block of 21 storey shop office building

iii) 8 blocks of 8 storey shop office

iv) 2 blocks of 24 storey shop office and service apartment (244 unit per block)

v) 1 block of 24 storey shop office and service apartment (292 unit per block)

42

Figure 4.3 shows the percentage of polymer product by locations. According to

the result obtained, most of the polymer was applied at Basement which is 45%.

Secondly about 26% goes to Service Apartment and follow by 19% applied to Shop

Office Building. Only 10% of polymer was used at Shop office. Base on the results,

basement subjected to additional loading especially for on going project where

construction on the higher levels are subjected to live load. For high rise building like

Service Apartment also subjected to additional loading. For low rise building like Shop

Office, the use of polymer is low due to the structure is relatively simple.

10%

19%

26%

45%

Shop Office Shop Office Building Service Apartment Basement

Figure 4.3 : The percentage of polymer product by locations

The polymer products used in this project are supplied by Fosroc Sdn. Bhd.

Table 4.3 shows the product used in Solaris Dutamas 2.

Table 4.3 : Polymer material use in Solaris Dutamas 2

Name of

Product

Type of Product Product

Category

Nitomortar PE

High strength jointing and multi-purpose repair

compounds

Resin repair

motars

Nitofil LV

Low viscosity or thixotropic epoxy resin

injection grout

Crack injection

43

Table 4.3 : ( Continued )

Renderoc FC

Single component polymer modified

cementitious fairing coat

Cementitious

repair

Nitobond SBR Polymer Bonding Aid and Motar Additive

Ancillary

product

4.2.1 Nitomortar PE

Nitomortar PE products are based on a polyester resin system. There are two

grades. Nitomortar PE: The standard material for general purpose use. Nitomortar PE

Concrete: A special grade allowing users to add suitable aggregate, thereby substantially

reducing the cost of infilling larger voids. Winter versions of Nitomortar PE is available

which are faster setting at low ambient temperatures. Both grades of Nitomortar PE are

supplied as two-component products with pre-weighed quantities of liquid resin and

powdered hardener, ready for on-site mixing and use. The hardener system enables the

mix to be varied from a pourable consistency to a trowellable mortar without

significantly affecting the setting times or strengths achieved.

The polyester resin used in Nitomortar PE is formulated to reduce shrinkage to a

minimum. Linear shrinkage will be approximately 0.8%. No further shrinkage will occur

after the material has cured. Cured Nitomortar PE performs under temperatures as high

as 60C and down to sub-zero conditions. Table 4.4 shows the properties of Nitomortar

PE.

44

Table 4.4 : Properties of Nitomortar PE

Property at 20C

Nitomortar PE flowable

consistency

Compressive strength at 7 days (BS 6319, Pt 2)

100 N/mm

Flexural strength (BS 6319, Pt 3)

28 N/mm

Tensile strength (BS 6319, Pt 7)

14 N/mm

Youngs Modulus of Elasticity

16 kN/mm

Thermal conductivity

1.0 Watt/m/C

Coefficient of thermal expansion

30 x 106 per C

4.2.2 Nitofil LV

Nitofil LV Is a two pack low viscosity epoxy resin product for the repair of

cracked concrete and masonry by the injection process. Nitofil TH Is a two pack

thixotropic epoxy resin product for the repair of cracked concrete and masonry by the

injection process.

The following Table 4.5 shows the properties obtained for Nitofil LV at a

temperature of 20C.

45

Table 4.5 : Properties of Nitofil LV

Compressive strength (BS 6319, Pt. 2):

70 N/mm @ 7 days

Tensile strength (BS 6319, Pt. 7):

27 N/mm @ 7 days

Flexural strength (BS 6319, Pt. 3):

50 N/mm @ 7 days

Slant shear bond (BS 6319, Pt. 4)

To dry concrete:

To wet concrete:

50 N/mm @ 7 days

40 N/mm @ 7 days

4.2.3 Renderoc FC

Renderoc FC is designed for vertical and overhead use to infill honeycombing

and voids up to 3 mm deep in the surface of concrete. Renderoc FC is supplied as a

ready to use blend of dry powders which requires only the site addition of clean water to

produce a highly consistent cementitious fairing mortar. The material is based on a blend

of ements, graded aggregates, special fillers and chemical additives to provide a

material with good handling characteristics, while minimising water demand.

The following Table 4.6 shows the results obtained at a water : powder ratio of

0.3 :1 by weight or 1: 3 by volume and temperature of 20C.

46

Table 4.6 : Properties of Renderoc FC

Test method

Typical result

Coefficient of thermal

expansion:

7 to 12 x 106/C

Working life:

Approximately 20 minutes

Setting time (BS 4550):

30 minutes to 1 hour

Fresh wet density:

Approximately 2000 kg/m3

4.2.4 Nitobond SBR

Nitobond SBR is a modified styrene butadiene rubber emulsion which is

supplied as a ready to use white liquid. It is designed to improve the qualities of site-

batched cementitious mortars and slurries. Being resistant to hydrolysis, it is ideal for

internal and external applications in conjunction with cement.

Table 4.7 below shows the result achieved by assessing the mechanical

properties of a 3:1 sand:cement mortar containing Nitobond SBR in the proportions 10

litres per 50 kg cement against a 3:1 sand:cement control mortar. The test methods used

were in full accordance with BS 6319 at 28 days air cured.

47

Table 4.7 : Properties of Nitobond SBR

Test method

Typical result Control

Compressive strength

(BS 6319, Pt 2: 1983)

62 N/mm2

46 N/mm2

Tensile strength

(ASTM C-190-85)

3.3 N/mm2

2.7 N/mm2

Flexural strength

(BS 6319, Pt3: 1983)

9 N/mm2

7.9 N/mm2

Slant shear bond

(BS 6319, Pt 4: 1984)

53 N/mm2

11 N/mm2

The advantages and disadvantages for using polymer material are shown on in Table 4.8.

Table 4.8 : Advantages and Disadvantages of Polymer in Construction

Product Name Type of Polymer Advantages Disadvantages

Nitomortar PE Polyester Tough, Best chemical

resistance, Good

overlay material

Shrinks, Need

primers, Styrene odor,

Toxicity concerns

Nitofil LV Epoxy High strength, H