PERPUSTAKAAN UMP

111111111 11011111 0000092814

CONTROLLING CRACKS IN REINFORCED CONCRETE BEAM USING

POLYMER MODIFIED MORTAR BY DIFFERENT METHODS

WAN SYARIAH BINTI WAN JAMALUDDIN

A report submitted in partial fulfillment of the

requirements for the award of the degree of

B. Eng (lions) of Civil Engineering

Faculty of Civil Engineering and Earth Resources

Universiti Malaysia Pahang

2014

Vi

ABSTRACT

The most common defect in concrete structures is the cracks. Cracking in concrete will affect the appearance, workability and the strength of the concrete structures. It may indicate the occurrence distress of the structure or less of durability, thus it will make not safe for application. The structure that damaged must be repaired to bring back its structure strength. This research investigates the efficiency of polymer modified mortar as a material for repair cracks. For this study of controlling crack, three beams of grade 20 strength were casted and repaired by three different methods. All the beam samples were tested by one point load test until first crack appear. The repair methods covered for this study were using polymer modified mortar by injection, patching and underlay coating. The beams were tested for second time until failure to get the deflection, ultimate load and pattern of cracks. Between this three methods of repairing cracks in beam using polymer modified mortar, underlay coat method showed the less differences of load and deflection between repaired and initial beam which were 83.1% and 26.8% respectively. Patch method resulted the least of 69.9% of load and 3.4% of deflection differences while inject method indicated 78% and 8.6% of differences in load and deflection respectively between initial and repaired beam. Most of cracks happened at the same places after they were repaired in flexural and shear patterns. For this study, less of polymer modified mortar was used for remove cracks due to less than 1 mm width of cracks. However, in real situation of the structures are remaining under condition of permanent forces, polymer modified mortar will apply more into cracks for the good results.

VII

ABSTRAK

Masalah yang biasa berlaku pada struktur konkrit adalah keretakan. Masalah keretakan akan mengganggu ketahanlasakan,kebolehkerjaan dan penampilan struktur bangunan. Sesetengah kes keretakan yang serius akan menyebabkan sesebuah bangunan tidak sesuai untuk didiami. Oleh yang demikian, kerja-kerja pembaikan perlu dijalankan untuk memperkukuhkan semula struktur bangunan tersebut. Kajian mi adalah untuk mengetahui kesesuaian mortar terubahsuai berpolimer sebagai bahan baikpulih bagi keretakan. Untuk tujuan tersebut, tiga rasuk gred konkrit 20 disediakan di mana rasuk di baiki dengan kaedah tiga cara yang berbeza. Kesemua contoh rasuk di uji dengan kaedah satu titik beban sehingga retak pertama wujud. Kemudian, contoh rasuk di baiki dengan cara yang berbeza. Mortar terubahsuai berpolimer digunakan bagi kaedah penampalan, penyuntikan dan lapisan pelapik. Rasuk-rasuk kemudian akan di uji untuk kali kedua sehingga kegagalan untuk mendapatkan beban, kelenduran dan jenis keretakan Antara tiga kaedah membaiki retak menggunakan mortar terubahsuai berpolimer, kaedah lapisan pelapik menunjukkan kurang perbezaan beban dan kelenduran antara rasuk yang di baiki dengan rasuk awalan yang mana 83.1% dan 26.8% keduanya. Kaedah penampalan memberikan keputusan terendah iaitu perbezaan 69.9% beban dan 3.4% kelenduran sementara kaedah penyuntikan memberikan 78% dan 8.6% perbezaan dalam beban dan kelenduran antara awalan dan rasuk yang di baiki. Kebanyakkan retak yang berlaku di tempat yang sama selepas ia di baiki dalam keadaan lendut dan ricih. Untuk kajian mi, hanya sedikit mortar terubahsuai berpolimer telah digunakan untuk membuang keretakan yang kurang dari 1 mm lebar. Walau bagaimanapun, dalam situasi yang sebenar struktur di bawah keadaan beban tetap, mortar terubahsuai berpolimer akan digunakan lebih ke dalam retak untuk keputusan yang bagus.

VIII

TABLES OF CONTENTS

Page

SUPERVISOR'S DECLARATION

CANDIDATE'S DECLARATION

ACKNOWLEDGEMENTS v

ABSTRACT vi

ABSTRAK vii

TABLES OF CONTENTS viii

LIST OF TABLES xii

LIST OF FIGURES xiii

CHAPTER 1 INTRODUCTION 1

1.1 Introduction 1

1.2 Background 2

1.3 Problem Statements 3

1.4 Objectives of the Study 3

1.5 Scopes of Study 3

1.6 Research Significances 4

1.7 Conclusion 4

CHAPTER 2 LITERATURE REVIEW 6

2.1 Introduction 6

2.2 Types of Cracks 6

2.3 Factors of Cracks 8

2.3.1 Cracking of Plastic Concrete 9 2.3.1.1 Plastic Shrinkage Cracking 9 2.3.1.2 Settlement Shrinkage 10

2.3.2 Cracking of Hardened Concrete 11 2.3.2.1 Chemical Reactions 11 2.3.2.2 Corrosion of Embedded Metals 12 2.3.2.3 Drying Shrinkage 14 2.3.2.4 Thermal Distress 15 2.3.2.5 Design Errors and Construction Overloads 16

ix

2.4 Impacts of Cracks on RC Beams 17

2.5 Evaluation of Cracks on RC Beams 17

2.5.1 Determination of Location and Extent of Cracks 18 2.5.1.1 Visual Inspection 18 2.5.1.2 Non Destructive Testing 19

2.6 Selection of Repair Procedures 19

2.6.1 Post Tensioning 20 2.6.2 Polymer Impregnation 20 2.6.3 Epoxy Injection 21 2.6.4 Stitching and Doweling 22

2.7 Selection of Repair Material 23

2.8 Introduction of Polymer Modified Mortar 24

2.9 Mechanism of Polymer-Cement Co-Matrix Formation 25

2.10 Properties of Polymer Modified Mortar 26

2.10.1 Workability 27 2.10.2 Water Retention 28 2.10.3 Setting Time 28 2.10.4 Tensile and Flexural Strength 29 2.10.5 Compression Strength 29

2.11 Suitability of Polymer Modified Mortar as Cracks Repair Material 30

2.12 Hi-Bond (Universal) Pre-packaged Polymer Modified Mortar 31

2.13 Conclusion 32

CHAPTER 3 RESEARCH METHODOLOGY 33

3.1 Introduction 33

3.2 Preparation of Materials for RC Beams 35

3.2.1 Fine Aggregates 35 3.2.2 Coarse Aggregate 35 3.2.3 Water 36 3.2.4 Cement 36

3.3 Reinforced Concrete Beams Design (Under-Reinforced) 37

3.4 Trial Mix 38

3.5 Preparation of Formwork 40

3.6 Concreting and Curing 41

3.7 Preparation of Material for Repair 43

3.8 Patching Material

3.9 Installation Cracks

X

3.10 Preparation of Beam for Repair Process 45

3.10.1 Surface Preparation 45 3.10.2 Entry Ports 46

3.11 Crack Repair Process with Polymer Modified Mortar 46

3.11.1 Injection 47 3.11.2 Patching 48 3.11.3 Underlay Coating 49

3.12 Evaluation of Concrete Repair 50

3.12.1 Flexural Test for Repair Beams 50

3.13 Conclusion 53

CHAPTER 4 RESULT AND ANALYSIS 55

4.1 Introduction 55

4.2 Tensile Strength Test of Reinforced Bar 55

4.3 Compression Test for Cubes 57

4.4 Loading Test on Beams 58

4.4.1 Ultimate Load 59 4.4.2 Deflection 60 4.4.3 Load vs Deflection 61 4.4.4 Pattern of Cracks 64

4.5 Conclusion 68

CHAPTER 5 CONCLUSION 70

5.1 Introduction 70

5.2 Conclusion 70

5.3 Recommendation 71

REFERENCES

APPENDIX 76

Data of initial beam for patch method 76

Data of repaired beam for patch method 77

Data of initial beam for inject method 78

Data of repaired beam for inject method 79

Data of initial beam for underlay coat method 80

xi

Data of repaired beam for underlay coat method 81

XII

LIST OF TABLES

TABLE NO. TITLE PAGE

2.1 Crack pattern result due to loading on beams 14

2.2 Comparison of polymer modified mortar with ordinary mortar 27

3.1 Proportioning of ordinary concrete 39

3.2 Mass of material for concreting 40

4.1 Result of tensile test for reinforcement bar Y12 55

4.2 Result of compression strength test 57

4.3 Maximum load for initial and repaired beams 60

4.4 Differences of maximum load for initial and repaired beams 60

4.5 Maximum deflection for initial and repaired beams 61

4.6 Differences of maximum deflection for initial and repaired beams 61

4.7 Number of cracks in RC beams 64

XIII

LIST OF FIGURES

TABLE NO TITLE PAGE

2.1 Pattern cracking 7

2.2 Hairline cracking 8

2.3 D-cracking 8

2.4 Plastic shrinkage crack 10

2.5 Plastic settlement crack 11

2.6 Crack pattern due to percentage of fiber content 12

2.7 Crack caused by corrosion 13

2.8 Drying shrinkage crack 15

2.9 Thermal distress crack 16

2.10 Post tensioning 20

2.11 Epoxy injection 22

2.12 Procedures of epoxy injection 22

2.13 Stitching 23

2.14 Compressive strength versus temperature 30

3.1 Flow chart of laboratory work 34

3.2 Fine aggregate 35

3.3 Coarse aggregate 36

3.4 Ordinary portland cement, 37

3.5 Detailing of the Beam 37

3.6(a) Link use for reinforcement 38

3.6(b) Bar of size 12mm used in RC beam 38

3.7(a) Raw materials for formwork 41

xiv

3.7(b) Formwork, bar and link ready to use 41

3.8 Cross Section of the concrete beam 41

3.9(a) Preparation of concrete 42

3.9(b) Slump test for concrete 42

3.10(a) Concreting process using vibrator 43

3.10(b) Curing process 43

3.11 Polymer modified mortar 43

3.12 Intallation of crack by one point load test 45

3.13 Ready mix of polymer modified mortar 47

3.14 Injection process into the cracks 48

3.15 Beam after patched 49

3.16 Flexural test for beam 51

3.17 Data logger 51

3.18 Load cell 52

3.19 Tranducer 53

4.1(a) Tensile test for reinforced bar Y12 56

4.1(b) Tensile machine data collector 56

4.2 Steel bar was failed 57

4.3(a) Sample of compression strength test after tested 58

4.3(b) Sample of cube after test 58

4.4(a) Flexural test of initial beam 59

4.4(b) Flexural test of repaired beam 59

4.5(a) Load vs deflection of repaired beam for patch method 62

4.5(b) Load vs deflection of repaired beam for inject method 62

4.5(c) Load vs deflection of repaired beam for underlay coat method 63

xv

4.6 Load vs deflection of repaired beams 64

4.7(a) Patch beam before repaired

65

4.7(b) Inject beam before repaired

66

4.7(c) Underlay coat beam before repaired

66

4.8(a) Patch beam after repaired

67

4.8(b) Inject beam after repaired

67

4.8(c) Underlay coat after repaired

67

CHAPTER 1

INTRODUCTION

1.1 INTRODUCTION

This chapter will focus on the introduction, background, problem statements,

objectives, scopes and research significance. Its also introduce to the basic things of the

concrete, repair material and cracks due to relate with the chapter. Other view of this

chapter will discuss about the situation happened related to the topic and the main

objectives of this study. It is explained also about the scopes that will do in this research

to achieved the objectives.

Concrete is an important material in construction industry. Combination of

concrete with steel for reinforcement bar, a complete building structure material can be

created. The tensile strength is provided by reinforcement steel in the concrete structure

and some of the shear strength. Meanwhile, the strong compression of the concrete will

protect the steel and provide durability. Reinforced concrete also most frequently

applied structural material because its strength and durability which has been used for

many years to build a wide of structure construction from houses to bridges(Ahmad et.

a!, 2012)

Reinforced concrete structure often show its vulnerability to the time dependent

phenomena that is including weathering, well before reaching ' the service life of the

structure. This phenomenon is widely used in replacement of existing structures is not a

possible measure. Thus, interest in rehabilitation and strengthening of reinforced

concrete structural elements has been rapidly increase around the world. In this

2

situation, development and methods for improving the safety and reliability of existing

concrete structures are in researched.

The damage of structural component is needed to be repaired for effective use of

the structure. A crack may cause serious failure of the structure, therefore it must be

detected in the early state since it is small. Concrete repair is a complex process which

is very different field with the new concrete construction. In scope of the time and

environment, it should be able to concrete structures in the capability to endure the

exposures of use.

An important component of structure repair industry is crack repairing which

needs to be comprehensive. Occurrence of cracks in concrete structures is very

common. The durability and appearance of structure is affecting from the cracks. It is

important to study methods of controlling cracks to prevent further deterioration of

concrete structures. In this study, reinforced concrete beams will be focus on crack

repair.

1.2 BACKGROUND

Crack happened in concrete structure due to many factors. They may affect the

appearance only or indicate significant structural distress and lack of durability. The

effects of cracks depend on the type of structure and the nature frequency of the

cracking. Suitable crack method repair depends upon the knowledge on the causes of

cracking. It will influence the selection of repair procedures, repair materials and types

of repairing.

In this study of controlling crack for reinforced structural beam, polymer

modified mortar (PMM) was used. Polymer modified mortar is made by partially

replacing the cement hydrate binders of conventional cement mortar or concrete with

polymers such as polymeric admixture or cement modifiers and by strengthening the

binder with the polymer. The polymeric admixtures or cement modifiers include

latexes, emulsified polymers, redispersible polymer powders, water soluble po1jmers;

liquid resins and monomer.

3

Different types of repair crack are to find the serviceability aspects appear after

beam will be failed. The good repair method of the structure between their performance

and strengthening compared to the controlling crack behaviours. Proper guidance and

support should be emphasis in the selection of crack repair method and repair material

for preferable result in concrete crack repair.

1.3 PROBLEM STATEMENTS

Cracking and spatting are common phenomenon appears in concrete structure.

The appearances of cracks may cause the strength of the structural member such as

beam decreased. There are many methods to repair such fault likeinj ecting material and

underlay coating. Therefore, suitable repair technique of beam is important to restore its

strength. Polymer modified mortar is selected in controlling cracks and able to increase

the strength, stiffness and ductility of the structure. Besides, factors of drying shrinkage,

chemical reaction, and settlement are deterioration can cause cracks.

1.4 OBJECTIVES OF THE STUDY

To identify the performance of polymer modified mortar to control cracks in

reinforced concrete beam.

• To compare effectiveness between three methods of this study to repair damaged

reinforced concrete beam.

• To determine the load, deflection, and pattern of cracking to the reinforced concrete

beam.

1.5 SCOPES OF STUDY

The limitation of this research on controlling crack Works of reinforced concrete

beam by using polymer modified mortar. The scope of this research include prepare of 3

reinforced concrete beams for flexural test using concrete grade 20 and 2Y12 at bottom

bar. The length of the beam is 1500mm with cross section of 150 x 200 mm.

Preparation suitable proportion of patching materials using polymer modified mortar.

4

This study also include the repairing the cracks by using crack injection method

and patching method. Beam 1 repaired by using patching material of polymer modified

mortar into the cracks, beam 2 will patch with the injection and beam 3 will patch and

inject with the additional of an underlaying coating at the bottom of the beam.

Analysing the mechanicals properties of polymer modified mortar such as ultimate

strength, deflection and pattern of cracks.

1.6 RESEARCH SIGNIFICANCES

Nowadays, epoxy resin injection is widely use for repairing works of structural

concrete member such as beam and column. Flexural test on repaired reinforced

concrete beams have shown that the epoxy resin injection not only eliminates the

unsightly appearance of wide cracks but also increase the flexural strength and stiffness

of the repaired member higher than the original beam (H. W. Chung, 1981). In spite of

the advantages, economical of application epoxy resin injection is quite expensive.

Therefore, focusing on application of polymer modified mortar which is cheaper than

epoxy resin injection in this study.

Polymer modified mortar is environmental friendly and it is can be classified as

construction materials that support the sustainability aspects of construction (Ahmad,

Elahi, Barbhaiya & Farid, 2012). Ohama, 1995 also said that polymer modified mortar

(PMM) have superior properties such as high tensile and flexural strengths, excellent

adhesion, high waterproofness, high abrasion resistance and good chemical resistance

compared to ordinary cement mortar. There were many strong interests focused on the

suitability of polymer modified mortar as repair materials. Then, we need to identify the

most appropriate method to introduce polymer modified mortar into the cracks of the

reinforced structural beam.

1.7 CONCLUSION

This chapter was indicated the introduction of the title which is include the

background of the study, problem statement, objectives of the study, scopes of the study

5

and research significance. Three important objectives was discuss in order to finished

this research and achieved it at the conclusion.

Basically, the introduction of the polymer modified mortar as a controlling crack

in reinforced concrete bar was discussed in this chapter.The introduction of the main

title is to explain about why this research is done. Next chapter will tell the literature

review about this study. It will explain more specific and related about the title of this

study.

CHAPTER 2

LITERATURE REVIEW

2.1 INTRODUCTION

This chapter will provide the review from previous study that is related to the

final year project. It will explain about the controlling crack, repairing crack and repair

material. The fill understanding of the concept is important in order to choose the best

way of controlling cracks and types of method repairing cracks.

Besides, the explaination of polymer modified mortar as a suitable material for

controlling cracks in this chapter. The mechanism properties of polymer modified

mortar compare to another materials. Then, the selection of the best methods that can be

used will choose based on the literature review of this chapter.

2.2 TYPES OF CRACKS

Cracks in a structure can be broadly classified as either active or dormant. If they

are active, they show some movement in direction, width or depth over a measured

period of time. However, the crack of dormant or unactive crack, they remain unchange.

Some dormant cracks are not dangered but if left without repaired, cracks provide

channels for moisture penetration which can lead to future damage.

Cracks can be more specifically classified based on three factors which is

direction, width and depth of the crack. They may be longitudinal, transverse, vertical,

diagonal or random. Pattern cracking, checking, hairline cracking and d-cracking are

rA

some crack classifications. All these types of cracks may range in size form less than 1

mm for fine to between 1 and 2 mm in medium to over 2 mm wide.

For pattern cracking, it is commonly happened. In this pattern, fine openings in

common pattern which due to contant volume of concrete that near below to the surface.

It can be seen at Figure 2.1 clearly showed the pattern cracking in the structure.

Checking cracking happened when shallow openings, too close and not regularly

spaced. Small cracks and placed randomly in expose of areas is the hairline cracking.

Basically, it happened in flexural to the angle of shear pattern which is shown in Figure

2.2. Lastly, d-cracking is defined as fine cracks at near intervals in a progressive random

features. Figure 2.3 was showed the d-cracking pattern which it mostly in circle

pattern(U.S. General Services Administration, 2012).

.- .-.

• . .- ..... .

Figure 2.1: Pattern cracking

Source: U.S General Services Administration (2012)

.j

8

Figure 2.2: Hairline cracking

Source: Home Design Magz (2013)

* c ,

Figure 23: D-cracking

Source: Seal Green (2011)

2.3 FACTORS OF CRACKS

Most of concrete cracks usually happen due to not proper design and

construction works. Due to the construction process, cracks can occur in unhardened

concrete which is also called as plastic concrete and hardened concrete. National Ready

Mixed Concrete Associate, 1998 stated that for the concrete surfaces crack, there are

some factor crack iiappened:

a) Gap of contraction and isolation joints and not proper practices ofj ointing.

9

b) Inappropriate preparation of subgrade.

c) More slump concrete used or excessive addition of water on the task.

d) Unsuitable finishing.

e) Less or no curing

The use of concrete during construction can define that much variables involved

in the product of finished concrete which directly give impacts to strength and

appearance. Most important of these things likes kind of cements, ratio of water to

cement, size and type of aggregate, type and proportionate amount of materials mixture

and various situations or actions happening during the mixing, replacement, finishing

and curing process (Hall and Foreman, 2013). One advantages of using concrete as a

building materials are the fact that a certain amount of cracking is bound to occur.

2.3.1 Cracking of Plastic Concrete

A plastic cracking is a type of shrinkage crack that only happens in wet concrete.

It is often seen in the top of a structure as diagonal lines. It is usually caused by delays

in applying the curing process due to rapid drying of the surface. (U.S. General Services

Administration, 2012).

2.3.1.1 Plastic Shrinkage Cracking

Plastic shrinkage cracking is usually produced when fresh concrete in its plastic

state which is subjected to rapid moisture loss. Rdso (n.d) has indicated that plastic

shrinkage cracking caused by factors of combination that include concrete temperatures

and air, relative humidity and velocity of wind at the concrete surface . All this factors

can be combined to factor high rates of evaporation surface in either cold or hot

weathers

Figure 2.4 above shows the plastic shrinkage cracks pattern on the structure.

When evaporation of moisture form fresh placed concrete to the surface faster than it is

replaced by bleed water, then the surface concrete will shrink. When no bleed concrete Will shrink due to the provide of restraint by the concrete below the surface drying

10

layer, stress of tensile developed in the weak, stiffening plasticity of concrete, resulting

in shallow cracks of various depth that may form a random, polygonal features or may

be appeared as essentially parallel to the other.

Figure 2.4: Plastic shrinkage crack

Source: Foundation, concrete and earthquake engineering (n.d)

2.3.1.2 Settlement Shrinkage

After first placement of the concrete, vibration and finishing concrete has done

to continue the consolidate. During this time, the wet concrete may restraint locally by

steel reinforcement, initially placed to hard concrete or formwork. This local restraint

may be resulted in voids cracks above and under the obstruction.

When bound with steel reinforcement, plastic settlement cracking will increase

with rising bar sizes, bigger slump and lower cover. The angle of settlement cracking

may intens by vibration insufficient or by use of leaking or flexible forms highly. The

Figure 2.5 below shows the settlement cracks at the surface of the concrete structure

(Rdso, n.d.).

11

Figure 2.5: Plastic settlement crack

Source: Rdso (n.d)

2.3.2 Cracking of Hardened Concrete

Holcim, (2010) mentioned that hardened concrete crack happens the

performance of concrete for shape that no longer can be altered without damage. It tells

that the cracks factored by drying shrinkage which resulted from movements of

temperature that can be taken place in all materials exposed to the structures. Unless the

member concerned movements permits of its structures without development of

extensive cracking, excessive stresses rare may be occurred.

2.3.2.1 Chemical Reactions

Chemical reactions may cause cracking of the concrete. Rdso (n.d.) explained

the reactions of the materials used to make the concrete or materials which is coming to

contact with the concrete after it has being hardened. Concrete may be cracked with the

period of time as the produce of moderately developing high reactions between contain

aggregate active alkalis and silica which obtained from hydratin of cement, admixtures

or outer sources. The another sources likes water curing, ground water, solutions of

alkaline kept or used in the structure that finished.

12

The alkalinity of silica reactions resulted in the structure of a swelling gel, that

be inclined from another portions of the concrete to draw water. These will cause to

local accompanying and expansion stresses of tensile and may be resulted in the

complete defection of the concrete structure.

Some rocks of carbonate take part in reactions by alkalis, which is certain

ingrediants make cracking and detrimental expansion. They are mainly assisted with

argillaceous dolomite limestone. For the observed crack pattern, multiple fine cracks

were observed along the length of the reinforcement concrete beam. Kamal et. al (2008)

said that the number of cracks also depended on the fiber content of the material as

shown in Figure 2.6 below. The higher of fiber content in materials, then, higher cracks

will occur.

Figure 2.6: Crack pattern due to percentage of fiber content

Source: Kamal et. al (2008)

2.3.2.2 Corrosion of Embedded Metals

Corrosion of steel produces iron oxides and hydroxides, which have a volume

much greater than the volume of the original metallic iron. This can increase in volume

13

causes high radial bursting stresses around reinforcing bars and results in local radial

cracks.

These splitting cracks can propagate along the bar, resulting in the formation of

longitudinal cracks or spalling of the concrete. A broad crack may also form at a plane

of bars parallel to concrete surface resulting in delamination. Cracks is actually

provided not difficult enter by oxygen, chlorides and moisture then little splitting cracks

may create a situation in which cracking and corrosion are accelerated. Figure 2.7

shows one of the example of cracks caused by the corrosion.

. .,..

•_t_

*1

l

Figure 2.7: Crack caused by corrosion

Source: Corrosion Technology Laboratory (n.d)

Malumbela et. al (2010) was indicated that it is difficult to associate corrosion

crack patterns with level of sustained load. Table 2.1 below gives corrosion crack

patterns that were exhibited by beams in this research called as crack pattern A, crack

pattern B and crack pattern C. The three kinds of crack are different type of patterns

which unsjmjlar with the compressive strength of the concrete.

In crack pattern A, one crack that propagared parallel to the corroded steel

reinforcement bars was remarked on the face of tensile to a beam which corrosion

agents were produced into the concrete structure. In crack pattern B, initially a beam

cracked on its face of tensile as in crack pattern A. Besiaes, when the corrosion