passant master thesis

NOVEL DISPERSION TECHNIQUE OF CARBON

NANOTUBE IN COMBINATION WITH NANO SILICA IN

CEMENT COMPOSITES TO ENHANCE ITS MECHANICAL

PROPERTIES

By

Passant Ahmed Mohamed Mohamed Youssef

A Thesis Submitted to the

Faculty of Engineering at Cairo University

in Partial Fulfillment of the

Requirements for the Degree of

MASTER OF SCIENCE

in

Structural Engineering

FACULTY OF ENGINEERING, CAIRO UNIVERSITY

GIZA, EGYPT

2015




PROPERTIES

By






MASTER OF SCIENCE

in


Under the Supervision of

Asst. Prof. Dr. Mohamed I. Serag Dr. Muhammad S. El-Feky

Associate Professor of Strength of

Materials

Civil Department

Faculty of Engineering, Cairo University

Researcher

Civil Engineering Department

National Research Center


GIZA, EGYPT

2015




PROPERTIES

By






MASTER OF SCIENCE

in


Approved by the

Examining Committee

Prof. Dr. Ahmed Khedr Taha Mohamed (External Examiner) Professor and Vice Head of Civil Engineering Department - National Research Center

Prof. Dr. Ahmed Mahmoud Maher Ragab (Internal Examiner) Professor of Strength of Materials - Faculty of Engineering - Cairo University

Asst. Prof. Dr. Mohamed Ismail Abdul Aziz Serag (Thesis Main Advisor) Asst. Professor of Strength of Materials - Faculty of Engineering - Cairo University

Dr. Muhammad Samy Abdul Hakeem El-Feky (Advisor) Researcher in Civil Engineering Department - National Research Center


GIZA, EGYPT

2015

Engineer’s Name:


Date of Birth: 20/09/1990

Nationality: Egyptian

E-mail: [email protected]

Phone: 002-0128-521-9445

Address: No. 49, El-Oroba St., Haram, Giza, Egypt.

Registration Date: 01/10/2012

Awarding Date: …./…./……..

Degree: Master of Science

Department: Structural Engineering

Supervisors: Asst. Prof. Dr. Mohamed I. Serag

Dr. Muhammad S. El-Feky

Examiners: Prof. Dr. Ahmed Khedr Taha Mohamed (External

examiner)

Prof. Dr. Ahmed Mahmoud Maher Ragab (Internal

examiner)

Asst. Prof. Dr. Mohamed Ismail Abdul Aziz Serag

(Thesis main advisor)

Dr. Muhammad Samy Abdul Hakeem El-Feky (Advisor)

Title of Thesis:

NOVEL DISPERSION TECHNIQUE OF CARBON NANOTUBE IN

COMBINATION WITH NANO SILICA IN CEMENT COMPOSITES TO

ENHANCE ITS MECHANICAL PROPERTIES

Key Words:

Nano Silica; Carbon Nanotube; Sonication; Optimization; Novel Technique,

Agglomeration

Summary:

This thesis studied the influence of the method and duration of applying direct

or indirect sonication energy to disperse Nano silica as well as the influence of

the method and duration of applying direct or indirect sonication energy and/or

homogenizer to carbon Nanotubes to explain the inconsistency in the previous

researches about the behavior of these Nano materials. Secondly, the effect of

superplasticizer on the dispersion of Nano silica and carbon Nanotubes by

optimizing the compressive strength of cement pastes was studied. Finally, a

study was investigated in order to examine the coupled effect of Nano silica and

carbon Nanotubes on the mechanical properties of cement mortars.

i

Acknowledgments

First and above of all, I have to thank Allah for this great chance I have right now. I

thank God for providing me with the opportunity to meet such helpful and wonderful

people those who helped me from the start of this thesis. All praises to Allah for giving

me knowledge, strength, support and patience to present this work.

I would like to express my deepest sense of gratitude to my respectable supervisor;

Prof. Dr. Mohamed I. Serag; who offered me the honor to be one of his students. I

thank him for his continuous advice and encouragement throughout the course of this

thesis. I also thank him for the guidance, caring, patience, and great effort to provide

me with an excellent atmosphere for doing this research.

I would like to thank my supervisor; Dr. Muhammad S. El-Feky; for his

understanding, patience, support and extreme care about the work efficiency. He gave

me a lot of experience about Nanotechnology. He spends very much time instructing

me how to collect data and how to write my thesis, as well as providing useful

suggestions about the experimental program. I have been lucky to get the opportunity to

work under his supervision.

I am also thankful for the kind assistance and efforts done by technicians; Mr. Hamdy

Beheiry and Mr. Ahmed Said; who helped in conducting the thesis experimental work.

I would also like to express my deep thanks to my super mother; Mrs. Hanan; She was

always there inspiring me with her support, love and patience, cheering me up and

stood by me through the good and bad times.

For the living memory of my father; Mr. Ahmed; although I didn't get the chance to

live with you these moments, your presence is still felt in my heart and your character

imprinted in my personality.

Many thanks to my sister; Ms. Dina; my soul mate, for encouraging me to keep on

following our dreams together. My sister; Ms. Menna; thank you for caring about my

well-being and believing in me.

I would like to thank my grandfather and all my lovely family members. They were

always supporting me and encouraging me with their best wishes, guidance and

advices. I thank God for them.

I would like to thank my close friends. They are all my true treasure in my life starting

of my childhood right now.

I feel very lucky to be surrounded by great colleagues; I am thankful to Eng. Sarah

Ibrahim, Eng. Basem Hasan, Eng. Ahmed Yasien, Eng. Mohamed Sherif and Eng.

Rania Salah El-Din.

Finally, I would like to thank the National Research Center, not only for providing the

funding which allowed me to accomplish this research, but also for providing me with

the facilities and workman power to implement the research experimental plan.

ii

Dedication

To my Mother & father's soul,

The reason of what I become today,

Thank you for your love, support and care.

To my sisters,

I am really grateful to both of you,

you have been my inspiration and my soul mates.

To my family,

All the love and respect to you for your support.

iii

Table of Contents

ACKNOWLEDGMENTS .............................................................................................. I

DEDICATION ............................................................................................................... II

TABLE OF CONTENTS ............................................................................................ III

LIST OF TABLES ....................................................................................................... VI

LIST OF FIGURES .................................................................................................... VII

ABSTRACT .............................................................................................................. XIV

CHAPTER 1 : INTRODUCTION ................................................................................ 1

1.1. GENERAL ........................................................................................................ 1

1.2. MOTIVATION ................................................................................................. 3

1.3. OBJECTIVES................................................................................................... 4

1.4. SCOPE OF WORK .......................................................................................... 4

1.5. THESIS LAYOUT ........................................................................................... 5

1.5.1. CHAPTER 1: INTRODUCTION ................................................................................ 5

1.5.2. CHAPTER 2: LITERATURE REVIEW ...................................................................... 5

1.5.3. CHAPTER 3: EXPERIMENTAL PLAN ...................................................................... 5

1.5.4. CHAPTER 4: RESULTS AND DISCUSSION .............................................................. 6

1.5.5. CHAPTER 5: SUMMARY, CONCLUSION AND RECOMMENDATION ......................... 6

CHAPTER 2 : LITERATURE REVIEW .................................................................... 7

2.1. INTRODUCTION ............................................................................................ 7

2.2. THE USE OF NANO SILICA IN CONCRETE ........................................... 8

2.2.1. GENERAL............................................................................................................. 8

2.2.2. INFLUENCE OF NANO SILICA ADDITION ON CEMENT PASTES, AND MORTARS ....... 8

2.3. DIFFICULTIES FACING THE USE OF NANO SILICA IN CONCRETE

10

2.3.1. NANO SILICA AGGLOMERATION ......................................................................... 10

2.3.2. MIXING AND DISPERSION METHODS .................................................................. 12

2.3.3. SUPER PLASTICIZERS COMPATIBILITY ................................................................ 13

2.4. THE USE OF CARBON NANOTUBES IN CONCRETE ......................... 14

2.4.1. GENERAL........................................................................................................... 14

2.4.2. INFLUENCE OF CARBON NANOTUBES ADDITION ON CEMENT PASTES AND

MORTARS ..................................................................................................................... 15

2.4.3. INFLUENCE OF CARBON NANOTUBES ADDITION ON CONCRETE PROPERTIES ...... 19

iv

2.5. DIFFICULTIES FACING CNT USAGE IN CONCRETE ....................... 20

2.5.1. CARBON NANOTUBES AGGLOMERATION ........................................................... 20

2.5.2. MIXING AND DISPERSION METHODS .................................................................. 21

2.5.3. SUPERPLASTICIZERS COMPATIBILITY................................................................. 24

2.6. THE COUPLED EFFECT OF NS AND CNT ON CEMENT

COMPOSITES ............................................................................................................. 25

2.7. STATISTICAL FACTORIAL DESIGN IN CONCRETE RESEARCH . 26

CHAPTER 3 : EXPERIMENTAL PROGRAM ....................................................... 29

3.1. GENERAL ...................................................................................................... 29

3.2. OVERVIEW OF EXPERIMENTAL PROGRAM ..................................... 29

3.2.1. CHARACTERIZATION OF USED MATERIALS ....................................................... 32

3.2.2. CHARACTERIZATION OF USED EQUIPMENT ....................................................... 38

3.2.3. SAMPLES PREPARATION .................................................................................... 42

3.2.3.1. Optimizing the dispersion of materials (phase one) ............................. 42

3.2.3.2. Samples for studying the coupled effect of NS and CNT on cement

mortars behavior (phase two) .................................................................................. 48

3.2.4. CHARACTERIZATION, TESTING AND ANALYSIS ................................................. 50

3.2.4.1. Characterization .................................................................................... 50

3.2.4.2. Testing .................................................................................................. 54

3.2.4.3. Analysis ................................................................................................ 56

CHAPTER 4 : RESULTS AND DISCUSSION ......................................................... 57

4.1. INTRODUCTION .......................................................................................... 57

4.2. OPTIMIZING THE DISPERSION OF NANO SILICA AND CARBON

NANOTUBE (PHASE 1) ............................................................................................. 57

4.2.1. OPTIMIZING THE TYPE AND TIME OF SONICATION ON THE DISPERSION OF NANO

SILICA 57

4.2.1.1. The effect of sonication type on the dispersion of NS (stage 1) .......... 58

4.2.1.2. The effect of sonication time on the dispersion of NS (stage 2) .......... 61

4.2.2. OPTIMIZING THE TYPE AND TIME OF SONICATION ON THE DISPERSION OF CNT . 83

4.2.2.1. The effect of sonication type on the dispersion of CNT (stage 1) ........ 83

4.2.2.2. Introduce a novel technique for the dispersion of CNT (stage 2) ........ 88

4.3. OPTIMIZING THE COUPLE EFFECT OF NANO SILICA AND

CARBON NANOTUBE ON THE MECHANICAL PROPERTIES OF CEMENT

COMPOSITES (PHASE 2) ......................................................................................... 96

4.3.1. OPTIMIZING THE EFFECT OF DIFFERENT DOSAGES OF CNT ON THE MECHANICAL

PROPERTIES OF CEMENT MORTARS (STAGE 1)............................................................... 96

4.3.2. OPTIMIZING THE COUPLE EFFECT OF DIFFERENT DOSAGES OF NS AND CNT ON

THE MECHANICAL PROPERTIES OF CEMENT MORTARS (STAGE 2) ................................ 102

CHAPTER 5 : SUMMARY, CONCLUSION AND RECOMMENDATION ...... 128

v

5.1. SUMMARY ................................................................................................... 128

5.2. CONCLUSION ............................................................................................. 129

5.2.1. OPTIMIZING THE TYPE AND TIME OF SONICATION ON THE DISPERSION OF NANO

SILICA 129

5.2.1.1. The effect of sonication type on the dispersion of NS (stage 1) ........ 129

5.2.1.2. The effect of sonication time on the dispersion of NS (stage 2) ........ 129

5.2.2. OPTIMIZING THE TYPE AND TIME OF SONICATION ON THE DISPERSION OF CNT

129

5.2.2.1. The effect of sonication type on the dispersion of CNT (stage 1) ...... 129

5.2.2.2. Introduce a novel technique for the dispersion of CNT (stage 2) ...... 130

5.2.3. OPTIMIZING THE COUPLE EFFECT OF NANO SILICA AND CARBON NANOTUBE ON

THE MECHANICAL PROPERTIES OF CEMENT COMPOSITES (PHASE 2) ........................... 130

5.2.3.1. Optimizing the effect of different dosages of CNT on the mechanical

properties of cement mortars (stage 1) .................................................................. 130

5.2.3.2. Optimizing the couple effect of different dosages of NS and CNT on

the mechanical properties of cement mortars (stage 2) ......................................... 130

5.3. RECOMMENDATION ............................................................................... 132

REFERENCES ........................................................................................................... 133

APPENDIX A: MASTERSIZER 3000 RESULT SHEET (NS) ............................. 141

APPENDIX B: MASTERSIZER 3000 RESULT SHEET (CNT) .......................... 142

vi

List of Tables

Table ‎3.1: Properties of Portland cement (wt. %) .......................................................... 32

Table ‎3.2: Chemical composition of Nano silica (wt %) ............................................... 33

Table ‎3.3: Physical and chemical characteristics of the polycarboxylate admixture ..... 37

Table ‎3.4: Bath sonicator properties and specifications ................................................. 39

Table ‎3.5: Rotor-stator homogenizer properties ............................................................. 41

Table ‎3.6: Constituents of Nano silica preparation samples .......................................... 42

Table ‎3.7: The second stage mixtures composition (gm.) .............................................. 43

Table ‎3.8: Sonication time of carbon Nano tube dispersion samples for direct sonication

........................................................................................................................................ 44

Table ‎3.9: Sonication time of carbon Nano tube dispersion samples for indirect

sonication ........................................................................................................................ 44

Table ‎3.10: Mixtures composition (gm.) for 3 cubes 5*5*5 cm3 .................................. 45

Table ‎3.11: Second stage mixtures composition (gm.) .................................................. 46

Table ‎3.12 : Phase two / stage one mixes constituents in (gm.) ..................................... 48

Table ‎3.13: Phase two / stage two mixes constituents in (gm.) ...................................... 49

Table ‎3.14: Data entry on the testing machine for the compressive strength test .......... 54

Table ‎3.15: Data entry on the testing machine for the flexure strength test ................... 56

Table ‎4.1: 7 days compressive strength studying the effect of NS and superplasticizer

on CNT dispersion .......................................................................................................... 87

Table ‎4.2: Comparison between imported and locally produced CNT properties ......... 95

Table ‎4.3 : Specific surface area of different dosages of CNT .................................... 100

Table ‎4.4: Summary of compressive strength effect .................................................... 121

Table ‎4.5: Summary of compressive strength effect .................................................... 124

vii

List of Figures

Figure ‎2.1: SWCNT and MWCNT (48) ......................................................................... 15

Figure ‎2.2: Interaction between COOH-MWCNTs and water molecules during cement

hydration process.(49) .................................................................................................... 16

Figure ‎2.3: Effect of cement grains on CNTs/CNFs dispersion; the large grains create

zones that are absent of Nanotubes/Nanofibers even after hydration has progressed(51)

........................................................................................................................................ 17

Figure ‎2.4: Schematic representation of the arrangement of CNTs in a cement matrix:

advantageous (a and c) and disadvantageous (b and d) distribution of the mixed CNTs

and N-CNTs, respectively.(60)....................................................................................... 22

Figure ‎2.5: Overall schema for CNT breaking. CNTs near the bubble nucleus (green

region) align tangentially during bubble (blue) growth. During collapse, CNTs may

rotate radially and stretch or buckle depending on their length.(61) .............................. 23

Figure ‎3.1: TEM micrograph of SiO2 Nano particles .................................................... 33

Figure ‎3.2: X-ray diffraction (XRD) analysis of SiO2 Nano particles.......................... 34

Figure ‎3.3: TEM micrograph of local carbon Nano tubes particles ............................... 34

Figure ‎3.4: X-ray diffraction (XRD) of local carbon Nano tube particles. .................... 35

Figure ‎3.5: Scanning electron microscope (SEM) of local carbon Nano tube particles 35

Figure ‎3.6: Transmission electron microscope (TEM) micrograph of imported carbon

Nano tubes particles ....................................................................................................... 36

Figure ‎3.7: Zeta potential distribution of imported carbon Nano tube particles ........... 36

Figure ‎3.8: Sieve analysis for fine aggregates as compared to the limits of the Egyptian

code of practice............................................................................................................... 37

Figure ‎3.9: Probe Sonicator ............................................................................................ 38

Figure ‎3.10: Bath sonicator ............................................................................................ 40

Figure ‎3.11: high speed homogenizer ............................................................................ 41

Figure ‎3.12: Schematic diagram showing differences between mixing sequences ........ 43

viii

Figure ‎3.13: Schematic diagram showing mixing sequence of mixes in order to examine

the effect of superplasticizer on CNT dispersion ........................................................... 45

Figure ‎3.14: Schematic diagram showing differences between mixing sequences ........ 47

Figure ‎3.15: Schematic diagram showing the mixing sequence of samples contain CNT

only ................................................................................................................................. 48

Figure ‎3.16: Schematic diagram showing the mixing sequence of samples contain N.S.

and CNT ......................................................................................................................... 50

Figure ‎3.17: Particle size analyzer Mastersizer 3000 used for samples dispersion ........ 51

Figure ‎3.18: The transmission electron microscope (TEM) used for samples

characterization ............................................................................................................... 52

Figure ‎3.19: Zeta-Sizer 2000 .......................................................................................... 53

Figure ‎3.20: QUANTA scanning electron microscope used for analysis ...................... 53

Figure ‎3.21: Universal testing machine 1000 KN .......................................................... 55

Figure ‎3.22: Data on the machine's screen .................................................................... 55

Figure ‎3.23: Flexure test using three points beam method ............................................. 56

Figure ‎4.1: Particle size distribution of Nano silica particles size using direct sonication

method ............................................................................................................................ 59

Figure ‎4.2 : Cumulative density of Nano silica particles size using direct sonication

method ............................................................................................................................ 59

Figure ‎4.3: Particle size distribution of Nano silica particles size using indirect

sonication method ........................................................................................................... 60

Figure ‎4.4: Cumulative density of Nano silica particles size using indirect sonication

method ............................................................................................................................ 60

Figure ‎4.5: Specific surface area for Nano silica particles using direct sonication

method ............................................................................................................................ 61

Figure ‎4.6: Specific surface area for Nano silica particles using indirect sonication

method ............................................................................................................................ 61

Figure ‎4.7: 7 days compressive strength for cement mortars containing 1% NS under

the effect of sonication for 3, 6, 9 and 12 minutes ......................................................... 63

ix







Figure ‎4.11: Particle size distribution of 1% NS particles size dispersed in water under

the effect of sonication for 0, 3, 6, 9 and 12 minutes ..................................................... 65

Figure ‎4.12: Cumulative density of 1% NS particles size dispersed in water under the

effect of sonication for 0, 3, 6, 9 and 12 minutes ........................................................... 65

Figure ‎4.13: Particle size distribution of 2% NS particles size dispersed in water under

the effect of sonication for 0, 3, 6, 9 and 12 minutes ..................................................... 66

Figure ‎4.14: Cumulative density of 2% NS particles size dispersed in water under the

effect of sonication for 0, 3, 6, 9 and 12 minutes ........................................................... 66

Figure ‎4.15: Specific surface area for 1% NS dispersed in water under the effect of

sonication for 0, 3, 6, 9 and 12 minutes.......................................................................... 67


sonication for 0, 3, 6, 9 and 12 minutes.......................................................................... 67

Figure ‎4.17: 7 and 28 days compressive strength for cement mortars containing 0.5, 1,

1.5 and 2% NS under the effect of sonication for 3 minutes .......................................... 68

Figure ‎4.18: 7 and 28 days compressive strength for cement mortars containing 1, 1.5

and 2% NS under the effect of sonication for 6 minutes ................................................ 69

Figure ‎4.19: 7 and 28 days compressive strength for cement mortars containing 1, 2 and

2.5% NS under the effect of sonication for 12 minutes ................................................. 69

Figure ‎4.20: 28 days compressive strength for optimum NS sonication time for each

concentration .................................................................................................................. 70

Figure ‎4.21: Particle size distribution of optimum NS sonication time for each

concentration .................................................................................................................. 71

Figure ‎4.22: Cumulative density of optimum NS sonication time for each concentration

........................................................................................................................................ 71

Figure ‎4.23: Specific surface area for optimum NS sonication time for each

concentration .................................................................................................................. 72

x

Figure ‎4.24: Flexure strength for beams with 1% NS sonicated for 3, 6, 9 and 12

minutes compared by the control batch .......................................................................... 73


minutes compared by the control batch .......................................................................... 73

Figure ‎4.26: Comparison between compressive and flexure strength for beams with 1%

NS sonicated for 3, 6, 9 and 12 minutes compared by the control batch ....................... 74

Figure ‎4.27: Comparison between compressive and flexure strength for beams with 2%

NS sonicated for 3, 6, 9 and 12 minutes compared by the control batch ....................... 74

Figure ‎4.28: Comparison between compressive and flexure strength for beams with

different percentages of NS sonicated for 3 minutes ...................................................... 75


different percentages of NS sonicated for 6 minutes ...................................................... 76


different percentages of NS sonicated for 12 minutes.................................................... 76

Figure ‎4.31: SEM micrograph of the plain cement composite (a) as compared to

optimum cement mortar contained 2.5 wt.% NS sonicated for 12 minutes (b) ............. 78

Figure ‎4.32: XRD the plain cement composite .............................................................. 79

Figure ‎4.33: XRD the cement mortar containing 2.5% NS sonicated for 12 min

(NS2.5/12) ...................................................................................................................... 80

Figure ‎4.34: TGA of the plain cement composite .......................................................... 82

Figure ‎4.35: TGA the cement mortar containing 2.5% NS sonicated for 12 min

(NS2.5/12) ...................................................................................................................... 82

Figure ‎4.36: Cumulative density of CNT using direct method ...................................... 85

Figure ‎4.37: Cumulative density of CNT using indirect method ................................... 85

Figure ‎4.38: Specific surface area for CNT particles dispersed in water using direct


Figure ‎4.39: Specific surface area for CNT particles dispersed in water using indirect


Figure ‎4.40: 7 days compressive strength of cement pastes studying the effect of NS

and superplasticizer on CNT dispersion ......................................................................... 88

xi

Figure ‎4.41: Effect of different methods of CNT treatment on cement pastes 7 days

compressive strength ...................................................................................................... 89

Figure ‎4.42: Gain in 7 days compressive strength for cement pastes studying different

methods for CNT treatment as compared to cement paste containing superplasticizer

and CNT ......................................................................................................................... 90

Figure ‎4.43: Gain in 7 days compressive strength for cement pastes studying different

methods for CNT treatment as compared to cement paste containing superplasticizer

only. ................................................................................................................................ 90

Figure ‎4.44: Particle size distribution of as received and optimum method for CNT

treatment ......................................................................................................................... 91

Figure ‎4.45: Cumulative density of as received and optimum method for CNT treatment

........................................................................................................................................ 91

Figure ‎4.46: 3D graph between time of sonication and homogenizer and compressive

strength ........................................................................................................................... 92

Figure ‎4.47: Contour graph presents the relation between time of sonication and

homogenizer and compressive strength .......................................................................... 92

Figure ‎4.48: CNT immediately before and after treatment (a), after a week (b), after a

month (c) ........................................................................................................................ 93

Figure ‎4.49: SEM micrograph of the plain cement paste (a) as compared to optimum

CNT treatment method (S40H10) cement paste (b) ....................................................... 94

Figure ‎4.50: TEM micrograph of the as received CNT (a) as compared to optimum

CNT treatment method (S40H10) (b)............................................................................. 95

Figure ‎4.51: 7 days compressive strength for CNT mortars compared by the control

batch ............................................................................................................................... 97

Figure ‎4.52: 28 days compressive strength for CNT mortars compared by the control

batch ............................................................................................................................... 98

Figure ‎4.53: Particle size distribution of CNT dispersed in water in different

percentages ..................................................................................................................... 99

Figure ‎4.54: Cumulative density of CNT dispersed in water in different dosages ........ 99

Figure ‎4.55: Flexure strength for beams containing 0.01, 0.02 and 0.03% CNT by

cement weight compared by the control batch ............................................................. 100

Figure ‎4.56: TGA of the cement mortar containing 0.03% CNT (CNT0.03) .............. 101

xii

Figure ‎4.57: 7 days compressive strength for mortars containing 0.01% CNT and

different percentages of NS .......................................................................................... 104










different dosages of NS ................................................................................................ 106

Figure ‎4.63: Particle size distribution of samples containing 1% NS and 0.02% CNT

...................................................................................................................................... 108

Figure ‎4.64: Cumulative density of samples containing 1% NS and 0.02% CNT ....... 108


...................................................................................................................................... 109

Figure ‎4.66: Cumulative density of samples containing 2% NS and 0.02% CNT ....... 109

Figure ‎4.67: Specific surface area for solutions containing 1% NS and 0.02% CNT .. 110

Figure ‎4.68: Specific surface area for solutions containing 2% NS and 0.02% CNT .. 110

Figure ‎4.69: Flexure strength for beams containing 0.01% CNT and different

percentages of NS ......................................................................................................... 112





Figure ‎4.72: SEM micrograph of a plain cement composite (a) as compared to cement

mortar combined 1 wt.% NS and 0.02 wt.% CNT (b) ................................................. 114

Figure ‎4.73: SEM micrograph of a plain cement composite (a) as compared to cement

mortar combined 2 wt.% NS and 0.02 wt.% CNT (b) ................................................. 115

xiii

Figure ‎4.74: TEM micrograph of combined 2 wt.% NS and 0.02 wt.% CNT cement

mortar, (a) mono dispersed CNT, (b) agglomerated NS and CNT .............................. 116

Figure ‎4.75: XRD the cement mortar containing 0.02% CNT (CNT0.02) .................. 117

Figure ‎4.76: XRD the cement mortar containing 1% NS sonicated for 3 min (NS1/3)

...................................................................................................................................... 117

Figure ‎4.77: XRD the cement mortar containing 1% NS sonicated for 3 min combined

with 0.02% CNT (NS1/CNT0.02) ................................................................................ 118


(NS2.5/12) .................................................................................................................... 118


combined with 0.02% CNT (NS2.5/CNT0.02) ............................................................ 119

Figure ‎4.80: TGA the cement mortar containing 1% NS sonicated for 3 min combined

with 0.02% CNT (NS1/CNT0.02) ................................................................................ 120

Figure ‎4.81: Actual by Predicted Plot .......................................................................... 123

Figure ‎4.82: Prediction Profiler .................................................................................... 123

Figure ‎4.83: Relation between %NS, %CNT and compressive strength ..................... 124

Figure ‎4.84 : Actual by Predicted Plot ......................................................................... 126

Figure ‎4.85: Prediction Profiler .................................................................................... 126

Figure ‎4.86: Relation between %NS, %CNT and compressive strength ..................... 127

Figure ‎4.87: Contour line between %NS, %CNT and compressive strength ............... 127

xiv

Abstract

Lately, a various efforts were exerted to improve the environmental friendliness of

concrete‎ to‎make‎ it‎ suitable‎ as‎ a‎ “Green‎Building”‎material‎ and‎ improve‎ the‎ cement‎

composites tensile strength. Recently, nanotechnology has attracted considerable

scientific interest due to the new potential uses of particles in nanometer scale (<

100nm). Thus industries may be able to re-engineer many existing products that

function at unprecedented levels. Nano materials are needed with cement to react with

excess CH, produce additional C-S-H, refine the pore structure to densify the cement

matrix, reduce permeability of gases and water in concrete, solve corrosion problem in

the reinforcement, act as brides to Nano and micro cracks to increase the tensile

strength and replace cement to reduce CO2 emission. An appropriate dispersion of

carbon nano tubes (CNTs) is a prerequisite for their use in improving the mechanical

properties of cement-based composites as the major problem in utilizing Nano-particles

is that they are highly agglomerated particles which cause loss in their high-surface area

due to grain growth. The dispersion problem has been combated by methods like using

surfactants, usually in combination with sonication. The present study focuses on the

effectiveness of superplasticizers (high-range water-reducing admixtures) and

ultrasonic processing (direct/indirect) on the dispersion of carbon Nano tubes at first in

water and then in cement composites. A qualitative analysis using compressive and

flexure strength tests were conducted in order to investigate the effect of different

dispersion techniques on the mechanical properties of cement composites incorporating

CNT and nano silica particles with different percentages. In addition micro-structural

analysis was carried out to observe the surface morphology and microstructure of

cement composites with different amounts of Nano silica and CNT addition. Statistical

surface response model was introduced correlating the percentage of both, nano silica,

and CNT with the compressive strength of cement mortars, and the effects of studied

parameters will be characterized and analyzed using ANOVA and regression models,

which can identify the primary factors and their interactions on the measured

properties. Finally, the optimization software searches for the greatest overall desirable

percentages of the nano silica and CNT which enhances the cement matrix. The

investigational study results showed that the strength can be improved by the addition

of low concentrations of nano silica and/or CNT, the experimental program helped in

achieving about 55% gain in compressive strength of cement mortars incorporating

0.02% CNT, and 1% nano silica as compared with the control mix, and 100% gain in

flexure strength for mixes containing as low as 0.01% CNT and 0.5% nano silica. The

results from the thesis will be helpful for developing of new modified cementitious

construction materials with enhanced engineering properties.

Key Words:

Nano Silica; Carbon Nanotube; Sonication; Optimization; Novel Technique, Agglomeration

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Chapter 1 : Introduction

1.1. General

Lately, a various efforts were exerted to improve the environmental friendliness of

concrete‎ to‎make‎ it‎ suitable‎ as‎ a‎ “Green‎Building”‎material‎ and‎ improve‎ the‎ cement‎

composites tensile strength. Recently, nanotechnology has attracted considerable

scientific interest due to the new potential uses of particles in nanometer scale (<

100nm). Thus industries may be able to re-engineer many existing products that

function at unprecedented levels.

The cement industry is considered to be one of the most energy consuming industries,

with a high rate of carbon dioxide (CO2) emissions, 5% of these emissions are caused

by global manmade; 50% by chemical manufacturing processes and 40% due to

burning fuel. Extensive research efforts have been directed to reduce the effect of the

cement industry either by improving the efficiency of the cement manufacturing

process or by using supplementary cementitious materials (SCMs), which partially

replace ordinary cement such as fly ash, ground granulated blast furnace slag, natural

pozzolans, and silica fume. The supplementary cementitious materials have been

studied in concrete as pozzolanic materials to react with CH and get the additional C-S-

H; not only to improve the mechanical properties of concrete, but also its workability

and durability (1).

The cement paste phase of concrete is a quasi-brittle material which has low tensile

strength, low ductility, and early development and propagation of micro-cracks due to

shrinkage at early ages. Steel rebars are the commonly used reinforcement for concrete

elements. It is a great desire to tailor the tensile and flexural mechanical properties of

the concrete in order to improve the damage and fracture resistance. The cracks in

concrete structures are mainly due to alkali silica reaction, which is a chemical reaction

in the concrete. Apart from the above, permeability of gases through pores and nano

and micro-cracks in the concrete, which leads to corrosion problem in the

reinforcement of concrete causes further deterioration. In the last few decades,

reinforcing concrete with micro- and macrofibers took place have carried out on the

effects of in controlling the growth of cracks in cement composites, various Nano fibers

have raised the interest of researchers due to their mechanical properties and high

potential in reinforcing cement matrix. Typical reinforcement of cementitious materials

is usually done at the millimeter scale and/or at the micro scale using macro-fibers and

microfibers, respectively. Nano-scale and unique multifunction properties of carbon

Nanotubes (CNTs) make them promising reinforcements to many engineering materials

(2; 3; 4; 5).

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Nano materials are needed with cement to react with excess CH, produce additional C-

S-H, refine the pore structure to densify the cement matrix, reduce permeability of

gases and water in concrete, solve corrosion problem in the reinforcement, act as brides

to Nano and micro cracks to increase the tensile strength and replace cement to reduce

CO2 emission.

Nano silica is a Nano material which its particles are white powder and spherical. Its

average diameter is 30 nm and the density equals to 2.12 kg/m3. Nano silica acts as

nuclei for cement phases, promoting cement hydration due to its pozzolanic reaction

with calcium hydroxide specially at a very early age and increasing the production of)

C-S-H, thus making the interfacial transition zone (6; 7). It also acts as filler in the

Nano pores due to its fine particle size (there is no need to water to fill inter space),

decreasing the water absorption and thus increasing the durability of the matrix (Oscar

Mendoza et al. 2014). Nano silica helps to reduce the cement content in concrete mixes

as cement replacement; the addition of 1 kg of silica permits a reduction of about 4 kg

of cement and can be higher for NS (6) and improves compressive strength of cement

composites(8).

Carbon Nanotubes have been the subject of many investigations as reinforcement for

several composite applications due to its mechanical properties. They are also highly

flexible and capable of bending in circles and forming bridges crossing micro and Nano

cracks developed in the cement composites(9). Carbon Nanotubes are hollow tubular

channels, formed either by one wall (SWCNT) or several walls (MWCNT) of rolled

graphene sheets(10), having diameters ranging 4 to 100 nm for MWCNT. Their length

is not restricted and can reach micro or even millimeter range. Their Young's modulus

varies between 1000 to 5000 GPa while density is around 2000 kg/m3(9). CNTs exhibit

high aspect ratio (length-to-diameter ratio) ranging from 30 to more than many

thousands for fibers, they are expected to produce stronger and tougher cement

composites than traditional reinforcing materials (e.g. glass fibers or carbon fibers)(10).

Carbon Nanotubes increase the amount of heat released during the hydration of cement

as they act as nucleation spots for hydration product(11). They decrease the porosity as

a filler in cement composites improving the uniform pore size distribution(12). OH–

functional groups grafted onto the surface of the CNT are able to interact with the C–S–

H generating bridges crossing micro and Nano cracks developed in the cement

composites, so CNT help in increasing flexure strength of cement composites(11; 13).

The major problem in utilizing Nano silica and carbon Nanotubes is that they are highly

agglomerated particles which cause loses in their high-surface area due to grain growth.

Effective de-agglomeration and dispersion for Nano-particles is needed to overcome

the bonding forces after wetting the powder; the ultrasonic power breakup of the

agglomerate structures in aqueous and non-aqueous suspensions allows utilizing the

full potential of Nano-sized materials. The addition of proper chemical dispersing

http://www.hielscher.com/ultrasonics/disperse.htm

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admixtures like superplasticizers helps in the de-agglomeration of Nano-particles in

order to cause electrostatic repulsive forces, as well as cement mixtures compressive

strength as some investigators have first dispersed Nano materials in water by using

surfactants and sonication and then added the dispersied materials to cement

composites(14). The extensive use of superplasticizer improves the workability of

cement mixtures.

Dispersion of Nano scale materials, such as carbon Nanotubes (CNTs), has become

dependent on ultrasonic methods specially with chemical dispersing agents(15).

Ultrasound is used in a wide range of physical, chemical and biological processes.

Homogenizing and dispersing are examples for physical processes. Most of the

applications of high-intensity ultrasound are based on cavitation forces effect which

reduce particles size and break the agglomerates(16). Ultrasonication can be applied in

in two ways: directly or indirectly through the walls of the sample container. Direct

sonication is achieved through ultrasonic probes, which are immersed into sample,

performing ultrasonication directly over the solution without any barrier to be crossed

by the ultrasonication wave other than the solution itself. Indirect sonication is

performed using an ultrasonication bath. Ultrasonic probe can be applied by immersion

directly into the sample container. The difference between the two methods make each

system suitable for a different set of applications(17). The use of the double sonicator

system is advantageous not only in cutting down the processing time but also it allows

the use of a probe sonicator into the water bath, instead of immersing it in the fluid

where the CNT or such Nano materials are being dispersed(15).

1.2. Motivation

Since the CNTs increase the flexural strength of the matrix, and NS

particles increase the compressive strength of the matrix, a study is

recommended in order to investigate the combined effects of NS and CNT.

Examine the effect of superplasticizer on the dispersion of Nano silica and

carbon Nanotubes.

Facilitating CNT dispersion and improving the interfacial interaction

between the CNT and the cement matrix by adding NS.

Inconsistency in compressive strength results under the effect of adding

CNT to cement matrix.

Achieving effective dispersion of CNT remains a challenge due to its van

der Waals forces self attraction.

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1.3. Objectives

Considering the importance of the dispersion of Nano silica and carbon Nanotubes

powders with regards to their performance in cementitious mixes and the scarcity of

information on this subject, as well as the previous research observations that the NS

and CNT effect as cement substitution depends on their nature and treatment method,

and taking into account the reported effects on the ultrasound cavitations. The current

research aims to:

Optimize the dispersion of Nano silica particles with a new developed,

innovative process by applying either direct or indirect sonication energy.

Introduce a novel technique in dispersion of carbon Nanotubes particles by

physical and chemical methods.

Investigate the effect of dispersion on the mechanical properties of cement

composites incorporating Nano silica and CNT with different dosages.

1.4. Scope of Work

In order to achieve the previously mentioned goals, experimental, and statistical

research plan is to be implemented.

The influence of the method and duration of applying direct or indirect

sonication energy to disperse Nano silica will be studied. Particle size distribution

will be introduced to investigate the effect of sonication power on NS particles

dispersion. Characterization of the main properties of prepared cement mortars

containing Nano silica will be investigated using different techniques; design,

electron microscope (SEM), transmission electron microscope (TEM), X-Ray

diffraction (XRD), zeta potential and thermo gravimetric analysis (TGA)

measurements to show the effect of sonication power as well as optimize the

optimum content of NS by weight of cement.

The influence of the method and duration of applying direct or indirect

sonication energy and/or homogenizer to carbon Nanotubes will be studied in order

to show its effect to de-agglomerate and disperse CNT particles. Different process

parameters (homogenizer speed and sonication time) will be optimized

experimentally. Particle size distribution will be introduced to investigate the effect

of carbon Nanotubes optimum treatment method on its particles dispersion.

Characterization of the main properties of prepared cement mortars containing

carbon Nanotubes will be through using different techniques such as scanning

electron microscope (SEM), transmission electron microscope (TEM), X-Ray

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diffraction (XRD), zeta potential and thermo gravimetric analysis TGA

measurements.

Investigate the effect of superplasticizer on the dispersion of Nano silica and

carbon Nanotubes by optimizing the compressive strength of cement pastes.

Optimize the difference between local and imported carbon Nanotubes by

determine its particle size distribution to show the difference in particles

dispersion after treatment and compressive strength after 7 and 28 days.

Finally, investigate the coupled effect of Nano silica and carbon Nanotubes

on the compressive and flexure strength of mortars. A full factorial design

will be introduced. Characterization of the main properties of dispersed

Nano silica and carbon Nanotubes will be through using scanning electron

microscope (SEM), transmission electron microscope (TEM), X-Ray

diffraction (XRD), zeta potential and thermo gravimetric analysis TGA

measurements.

1.5. Thesis Layout

The proposed thesis will be designed in order to help the reader easily trace the

previously mentioned objectives as follows:

1.5.1. Chapter 1: Introduction

In the first chapter; an introduction to the Nano technology in concrete will be

presented, the main objectives, as well as the scope of work and the thesis layout.

1.5.2. Chapter 2: Literature Review

In the second chapter; literature review about Nano silica and carbon Nanotubes main

properties, as well as the reported factors affecting their behavior. In addition a review

about effect of sonication to solve the agglomeration produced due to mixing Nano

materials in water, as well as the effect of superplasticizer. The use of different

statistical methods in analyzing pastes and mortars behavior will be mentioned.

1.5.3. Chapter 3: Experimental plan

The third chapter will represent the experimental program, starting from the dispersion

techniques of the materials used, the equipments conducted in the experimental

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program, and ending with the detailed plan of work as well as the characterization

means used in evaluation of results. The utilization of Nano silica and carbon

Nanotubes in mortars, the preparation process using direct and indirect sonication, as

well as the test of mortars flexure strength after 28 days and compressive strength after

7 and 28 days, water curing, after adding Nano silica and carbon Nanotubes.

1.5.4. Chapter 4: Results and Discussion

The fourth chapter represents the results of the conducted experimental program, in

addition to the full discussion and the interpretation of the results.

1.5.5. Chapter 5: Summary, Conclusion and Recommendation

In the last chapter, a summary of the thesis will be introduced, as well as the major

conclusions and recommendations of the experimental plan. The outcome of the thesis

is to produce cement matrix with advanced new properties developed by the innovative

application of NS and CNT addition to the matrix.

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Chapter 2 : Literature Review

2.1. Introduction

Nanotechnology has changed our vision, expectations and abilities to control the

material world. The developments in Nano-science can also have a great impact on the

field of construction materials. Portland cement, one of the largest commodities

consumed by mankind, is obviously the product with great, but not completely explored

potential. Better understanding and engineering of complex structure of cement based

materials at Nano-level will definitely result in a new generation of concrete, stronger

and more durable, with desired stress-strain behavior and, possibly, with the whole

range of newly introduced smart properties(18).

Nano materials are defined as materials of size less than 100 nm (1 nm = 10–9 m)(19).

Nano silica and carbon Nanotubes are of the most effective Nano materials in the

improvement of cement composites mechnical properties. Their surface area is

increased by the reduction of the particle size; which causes a higher percentage of the

atoms interaction with other matter in consequence agglomeration blocks surface area.

Only well-dispersed or single dispersed particles help to get effective results. Good

dispersion causes reduction in the quantity of Nano materials needed to achieve the

same effects. Most Nano materials are still fairly expensive because of its high

importance for the formulation of some commercial products containing Nano

materials. Nano silica and carbon Nanotubes particles agglomerate during the wetting

so it is produced in a dry process. Although that the particles need to be mixed into

liquid to disperse well (16).

Nano silica and carbon Nanotubes can improve the bond between the aggregates and

cement paste. Studies on cement paste with NS and CNT are absolutely necessary to

understand their influence. Currently these types of Nano materials are being used for

the creation of new materials, devices and systems at molecular, Nano and micro-level.

Nano silica and carbon Nanotubes show unique physical and chemical properties that

can lead to the development of more effective materials than the ones which are

currently available. The extremely fine size of Nano-particles yields favorable

characteristics, because of their high surface area and excellent fire retardant properties;

they can be used in construction in many ways. Addition of NS and CNT to cement and

concrete can lead to significant improvements (20).

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In this MSc. project the effect of coupled Nano silica and carbon Nanotubes will be

tested on the compressive and flexure strength of cement mortars. In addition to this,

the aim of this research will be extended to find optimum method for the dispersion of

cement particles, cement, NS and CNT.

2.2. The use of Nano silica in concrete

2.2.1. General

Recently, Nano silica appears to be one of the attractive cement substitution alternatives

for researchers. There is some reports studied using Nano silica as cement-based

building material and other studied the mix with other Nano materials. Compared to

other Nano materials, Nano silica has a unique advantage in the potential pozzolanic

reaction with cement hydration products. Due to its ultra-fine particle size, it can

possess a distinct pozzolanic reaction at a very early age (16). One of the important

applications of Nano silica is to improve the hydration of cement blended with fly ash,

slag or other pozzolanic materials (21; 7; 22).

Some authors concluded that Nano silica can improve concrete workability and strength

(23; 24; 25). Also others concluded that when NS (wt.%) is mixed into the cement

mortar in the fresh state it has a direct influence on the water amount required in

cement mixtures, for that higher amounts of water or chemical admixtures are needed

to keep the workability of the mixture (26; 27; 16).

2.2.2. Influence of Nano silica addition on cement pastes, and mortars

Hui Li et al. (2003) studied the mechanical properties of cement mortars containing

Nano-Fe2O3 and Nano-SiO2. The results showed that the compressive and flexural

strengths of the cement mortars mixed with the Nano particles after 7 and 28 days were

higher than that the control batch of a plain cement mortar. Therefore, it is feasible to

add Nano-particles to improve the mechanical properties of concrete. The SEM study

of the microstructures between the cement mortar mixed with the Nano-particles and

the plain cement mortar showed that the Nano-Fe2O3 and Nano silica filled up the

pores and reduced Ca(OH)2 compound among the hydrates(21).

Ye Qing et al. (2005) studied the influence of Nano silica addition on properties of

hardened cement paste as compared with silica fume for measurement of compressive

and bond strengths, and by XRD and SEM analysis. Results indicated that NS made

cement paste thicker and accelerated the cement hydration process. Compressive and

bond strengths of paste–aggregate interface incorporating NS were higher than those

incorporating SF, especially at early ages. And when increasing the NS content, the rate

of bond strength increase was more than that of their compressive strength increase.

9

With 3% NS added, NS digested calcium hydroxide CH crystals, decreased the

orientation of CH crystals, reduced the crystal size of CH gathered at the interface and

improved the interface more effectively than SF. The results suggested that with a small

amount of added NS, the CH crystals at the interface between the hardened cement

paste and aggregate at early ages may be effectively absorbed in high performance

concrete (7).

Byung-Wan Jo et al. (2006) studied the properties of cement mortars with Nano silica.

The results showed that the compressive strengths of mortars with Nano silica particles

were all higher than those of mortars containing silica fume at 7 and 28 days. It is

concluded that the Nano-particles are more valuable in enhancing strength than silica

fume since strength increased as the Nano silica content increased from 3% to 12%.

However, they demonstrated that using higher content of Nano silica must be

accompanied by adjustments to the water and superplasticizer dosage in the mix in

order to ensure that specimens do not suffer cracking. Otherwise, using this much

quantity of Nano-SiO2 could actually lower the strength of composites instead of

improving it, although this finding was not observed in their study.

The continuous hydration progress was monitored by scanning electron micrograph

(SEM) observation, by examining the residual quantity of Ca (OH) 2 and the rate of

heat evolution. The results of these examinations indicate that Nano SiO2 behaved not

only as a filler to improve microstructure, but also as an activator to promote

pozzolanic reaction (28).

Tobón J. I. et al. (2010) studied some physical properties of Portland cement type III

replaced with Nano silica in percentages of 1, 3, 5 and 10%. Main determined

properties were fluidity, normal consistency, setting times, heat of hydration and

compressive strength on pastes and mortars. It was made also a comparative analysis

with samples substituted with commercial silica fume in percentages of 5, 10 and 15%.

Results showed that the Nano silica from 5% started to have a major positive influence

on the mechanical strength of mortars and with a 10% of substitution improvements in

compressive strength up to 120% with respect to the control sample for one day of

curing can be achieved. For longer curing time the improvement is decreased slightly,

to reach near 80% improvement in strength after 28 days of water curing (26).

Sayed Abd El-Baky et al. (2013) study investigated the influence of adding Nano-

silica particles on the properties of fresh and hardened cement mortar through

measurements of workability, compressive and flexure strengths in addition to

measuring by SEM analysis. Nano-silica particles with size of 19 nm had been used by

1, 3, 5, 7 and 10 % by weight of cement content. Results indicated that the cement

mortar workability decreased with increasing Nano-silica addition. On the other hand,

the percentage of 7 % of Nano-silica recorded as optimum percentage in compressive

and flexure strength measured for cement mortar. The improvement in compressive and

flexure strength measured as 55.7 % and 46.9 % respectively, compared with the

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control mortar, especially at early ages. In addition, the scanning electron microscope

(SEM) analysis of the microstructures showed that the Nano silica filled the cement

paste pores, more homogeneity for cement paste and interfacial zone, by reacting with

calcium hydroxide crystals forming more calcium silicate hydration(8).

Hongjian Du et al. (2014) investigated the durability properties of concrete containing

Nano-silica at dosages of 0.3% and 0.9%, respectively. This study experimentally

measured the properties related to durability of OPC concrete with the addition of

Nano-silica at 0.3% and 0.9%, respectively. The study concluded that in comparison

with the reference concrete, Nano-silica exhibited obvious pozzolanic reaction with the

Portlandite, even at a very early stage. This was verified by the reduced Portlandite

content and the increased compressive strength at 1 day. SEM observations found the

paste more homogeneous for concrete containing Nanosilica(29).

2.3. Difficulties facing the use of Nano silica in concrete

2.3.1. Nano silica agglomeration

When fine particles are added to cement, Nano materials have a strong tendency to

form agglomerates when it contacts with water. This phenomenon affects badly the

rheological behavior of the paste and the ultimate hardened properties. Thus, there is a

need to increase the repulsive forces between particles, by adding proper chemical

admixtures like superplasticizer or by adding extra water to disperse the solid particles

in aqueous solution (16).

Deyu Kong et al. (2012) investigated the influence of Nano-silica agglomeration on

microstructure and properties of the hardened cement-based material by using

precipitated silica with very large agglomerates and silica fume with much smaller ones

as Nano scale additives. The results showed that the addition of either PS or SF refines

pore structure of the hardened cement paste. However, the SEM observation showed

that the pozzolanic C–S–H gels from the agglomerates cannot function as binder. There

even exists interfacial transition zone between the agglomerates and the bulk paste. The

Nano-indentation test indicated that the large agglomerates may become weak zones

due to their low strength and elastic modulus. It is proposed that the microstructure

improvement have nothing to do with the seeding effect, but result from the water-

absorbing, filling, and pozzolanic effects. Through PS addition, compressive strength of

the mortars and their resistance to calcium leaching and chloride penetration were

enhanced. However, these improvements were less significant than those with FS

addition. The reason is that much more fillers are provided whereas much fewer weak

zones are introduced in the mortar with FS addition than that with PS(30).

Hesam Madani et al.(2012) studied the pozzolanic reactivity of mono dispersed Nano

silica hydrosols and their influence on the hydration characteristics of Portland cement.

11

Their study reveals that the Nano silica hydrosols with higher specific surface areas had

faster pozzolanic reactivity, especially at early ages; moreover, the results are indicative

of the accelerating influence of Nano silica and silica fume on the hydration of cement.

As compared with the Nano silica, silica fume had slower pozzolanic reactivity in lime

and cement pastes. The Nano silica hydrosols reduced the initial setting time of the

cement pastes. The use of Nano silica hydrosols with higher specific surface areas or

increasing the dosage of Nano silica led to shorter initial setting time of the pastes.

Shorter initial setting time seems to be due to shortening the induction period of the

pastes through accelerating the conversion of the first-stage C-S-H, surrounding the

cement particles, to the stable form, via fast pozzolanic reactivity. Silica fume did not

have significant pozzolanic reactivity at early ages; therefore, this material not only did

not reduce the initial setting time of the pastes but also delayed it due to less cement

content in its respective cement pastes.

The Nano silica and silica fume reduced the difference between the initial and final

setting times of the pastes, probably due to accelerating the hydration of cement

through providing additional surfaces by silica aggregates for early precipitation of

hydrate products. Nano silica hydrosols and silica fume accelerated early hydration of

cement at the first day. However, by progress of hydration and from 7 days, lower

hydration degree of cement in the pastes containing the Nano silica compared to the

plain paste was observed. Lower hydration degree of cement can be attributed to the

entrapment of some of mix water in the aggregates of Nano silica formed in cement

paste environment, making less water available for the progress of cement hydration.

The cement in paste containing silica fume had higher hydration degree compared to

the cement in pastes containing Nano silica. The pastes containing the Nano silica had

less workability compared to the plain paste and pastes containing silica fume. This is

believed to be due to considerable water absorption in the aggregates of Nano silica

(31).

Deyu Kong et al. (2013) investigated the influence of Nano-silica agglomeration on

fresh properties of the cement paste by using precipitated Nano-silica (PS) with very

large agglomerates and fumed Nano-silica (FS) with much smaller ones as Nano-

strengthening admixtures. The rheological tests revealed that addition of PS showed a

greater influence on rheological behavior of the paste than that of FS, because the very

large agglomerates in PS cannot act as fillers to release free water in the void space

originally contributing to fluidity, but absorb free water originally contributing to

fluidity in paste. Through monitoring the heat evolution, it is interestingly found that

addition of PS accelerated cement hydration more significantly than that of FS though

the latter provides much more seeds than the former, implying that the acceleration may

have nothing to do with the so-called seeding effect. The calcium-adsorption tests

confirmed that the accelerating effect is probably caused by the rapid calcium

absorption of Nano-silica, which can keep always under-saturation of calcium ions in

paste, enabling a higher dissolution rate of calcium and thus an increase of heat

evolution (32).

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Tina Oertel et al.(2013) studied primary particle size and agglomerate size effects of

amorphous silica in ultra-high performance concrete. The study focuses on the

influence of primary particle sizes and sizes of agglomerates of different amorphous

silica in UHPC. As a reference system, wet-chemically synthesized silica was used with

very high purity, defined particle sizes, narrow primary particle size distributions and

controllable agglomerate sizes. The obtained data were compared to silica fume. The

results indicate that non-agglomerated silica particles produce the highest strength after

7 d, but a clear dependence on primary particle sizes, as suggested by calculations of

packing density, was not confirmed. UHPC may be improved by incorporating an

ameliorated dispersion of silica e.g. through commercial silica sols. Ideal silica fume

dispersion by a common mortar mixing procedure might be impossible, but the

dispersion of silica fume in water using ultrasound leads to at least some improvements.

Furthermore, commercial silica should lead to higher strength if they provide particles

dispersed to their primary particle sizes (e.g. silica sols from ion exchange processes).

The impurity of silica fume seems to have no negative influence on the compressive

strength (33).

2.3.2. Mixing and dispersion methods

Li et al. (2004, 2007) studied the effect of 15 nm Nano silica on mortar and concrete.

To help in the dispersion of Nano silica, Firstly they mixed Nano silica powder with

water and superplasticizer using a mortar mixer for several minutes. However, the

extent of dispersion achieved was not determined (21).

Porro et al. (2005) investigated the effect of Nano SiO2 in powder form with average

particle sizes 5 to 20 nm on cement pastes properties. These researchers dry mixed

Nano silica powder with cement before adding water and did not study the state of

aggregation of the Nano silica (34).

Jo et al. (2007) and Naji Givi et al. (2011) studied pre mixed Nano silica with mixing

water to help with their dispersion and then added the resulting suspensions to the rest

of mix ingredients (28).

Qing et al. (2008) used a similar method to above researches in studying the effect of

Nano silica with particle size of 15 nm and specific surface area of 160 m2/g cement

pastes properties. These researchers also did not consider dispersion state of the Nano

silica used (35).

Amiri et al. (2009) studied the effect of pH varied from 2 to 8.5 on dispersion state of

suspensions of pyrogenic Nano silica with average particle size of 12 nm and specific

surface area of 200m2/g. They used considerable amount of energy included high shear

mixing of diluted Nano silica suspensions for 5 min, followed by sonication for 60 min.

They observed improvement in dispersion with increasing pH values. Average size of

Nano silica aggregates was 0.2 lm after dispersion at pH of 6(36).

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2.3.3. Super plasticizers compatibility

The addition of Nano silica (NS) improves the particle size distribution, reduces

porosity, and the pozzolanic reaction between NS and calcium hydroxide (CH) yielding

calcium silicate hydrates (C-S-H). These actions enhance mechanical strength (37; 38).

The filling of the inter-particle space composes a dense cement matrix and reduces the

water demand, so there is no need to fill the space with water. In this case, the use of a

superplasticizer is strongly recommended to guarantee the cement matrix workability

(39). When adding superplasticizer, workability at a constant water/cement ratio is

improved. Alternatively, the same plain cement paste workability can be reached with

reduction in water content. In this case, cement materials with higher mechanical

strengths can be obtained (40).

Consequently, admixtures may interact not only with cement but also with other

components. Nonetheless, very few studies have been conducted on the compatibility

of blended cements and PCE admixtures.

Magarotto et al. (2003) concluded that limestone-blended cements adsorb greater

amounts of PCEs and gain better workability than non-blended cements (41).

Alonso et al. (2005, 2007) concluded that the rheological changes induced by PCEs on

fly ash-blended cements are the same to the changes observed in non-blended cement

(42).

Li et al. (2006) found that the adsorption of PCEs on fly ash-blended cement pastes

(with 20% of fly ash) was less intense than non-blended cement pastes (43).

Sahmaran et al. (2006) studied the effect of replacing 15 to 30% of cement with fly

ash and limestone powder in self-consolidating mortars containing PCEs. The results

concluded that the fluidizing effect of used admixtures in the mortars made with

blended was greater than that of non-blended cement (44)

Palacios et al. (2009) concluded that PCEs induce greater flow-ability in pastes

containing slag than in unblended paste; by consequently this effect is enhanced with

the rising percentage of slag in the pastes (45).

Olga Burgos-Montes et al. (2012) studied the compatibility between superplasticizer

admixtures and cements with mineral additions, the investigation explored the effect of

limestone, fly ash and silica fume on Portland cement and the interaction of these

additions with naphthalene (PNS), melamine (PMS), lignosulfonate (LS) and

polycarboxylate (PCE) based admixtures. The results showed that cement–

superplasticizer compatibility was altered by the physical (specific surface) and

chemical (surface charge) characteristics of the mineral additions studied, in addition

limestone has considerable affinity for the polymer molecules, which adsorb onto the

14

surface of its particles, it tends to adsorb PCE admixtures more intensely than the other

additions studied. The steepest decline in yield stress is obtained in the presence of PCE

and PNS. They also conclude that fly ash exhibits greater affinity for PMS than the

other cements and mineral additions studied in this work, yielding similar results for

PMS and PNS. In the case of silica fume, with a high negative zeta potential (-16 mv)

the physical characteristics are dominant. Due to the high specific surface of silica

fume, CEM II/A-D pastes demanded high doses of superplasticizer to improve the

rheological behavior of fresh pastes. The study concluded that while the effects

generated by the traditional admixtures are probably the results of an electrosteric

mechanism, the PCE based superplasticizer stabilizes cement and addition particles by

a sterical mechanism, PCE is adsorbed less intensely and lowers yield stress more

effectively at lower dosages than the other admixtures(46).

J. M. Fernandez et al.(2013) studied the effect of individual and combined addition of

both Nano silica (NS) and polycarboxylate plasticizer (PCE) admixtures on aerial lime

mortars. The sole incorporation of NS increased the water demand, as proved by the

mini-spread flow test. An interaction between NS and hydrated lime particles was

observed in fresh mixtures by means of particle size distribution studies, zeta potential

measurements and optical microscopy, giving rise to agglomerates. On the other hand,

the addition of PCE to a lime mortar increased the flow ability and accelerated the

setting process. PCE was shown to act in lime media as a deflocculating agent,

reducing the particle size of the agglomerates through a steric hindrance mechanism.

Mechanical strengths were improved in the presence of either NS or PCE. The

optimum being attained in the combined presence of both admixtures that involved

relevant micro-structural modifications, as proved by pore size distributions and SEM

observations (47).

2.4. The Use of Carbon Nanotubes in Concrete

2.4.1. General

The most popular type of Nano-tubes is carbon Nano-tubes. In 1991, It was discovered

by the Japanese Scientist Sumio Iijima. A single layer Nano-tube was synthesized in

1993‎ by‎ mixing‎ metals‎ such‎ as‎ Cobalt‎ and‎ Graphite‎ electrodes.‎ In‎ 1996,‎ Smalley’s‎

group in Texas, USA developed a method to result single walled CNT with unusually

uniform diameters in high yield (48).

Carbon Nanotubes are a form of carbon having a graphene sheet rolled into a

cylindrical shape, its name coming from the Nanometer diameter size. The length of

SWNTs is not restricted and can reach micro or even millimeter range and can have one

layer or wall (single walled Nanotube) or more than one (multi walled Nanotube). Due

to the energetic requirements the preferable diameter of a single wall Nanotube

(SWNT) is about 1.4 nm, while SWNTs with diameters ranging from 0.4 nm and up to

15

2.5 nm have been synthesized. Multi-wall carbon Nanotubes (MWNTs) can be

represented as a family of SWNTs of different diameters, which are combined within a

single entity in the form of concentric type MWNTs (18).

Nanotubes are members of the fullerene structural family and exhibit extraordinary

strength and unique electrical properties, also being efficient as thermal conductors.

They‎have‎five‎times‎the‎steel‎Young’s‎modulus;‎it‎ranges from 270 to 3600 GPa and

theoretical predictions indicate that the modulus can be higher than 5000 GPa. Its

strength is eight times the strength of steel; The strength of very long (about 2 mm)

ropes is in the range of 1.72 ± 0.64 GPa(19; 48). In tension mode, the strain at failure is

higher than 12% and the strength varies from 10 to 63 GPa (48). Figure 2.1 shows the

difference between SWCNT and MWCNT.

Figure ‎2.1: SWCNT and MWCNT (48)

2.4.2. Influence of carbon Nanotubes addition on cement pastes and

mortars

Geng Ying Li et al. (2004) investigated the effect of adding H2SO4 and HNO3

solutions to multi-walled carbon Nanotubes in cement composites. The results showed

that the treated Nanotubes can improve the flexural strength, compressive strength, and

failure strain of cement composites; also the addition of carbon Nanotubes can improve

the pore size distribution and decrease porosity. The paper concluded that there are

interfacial interactions between carbon Nanotubes and the hydrations of cement (such

as C–S–H and calcium hydroxide), which will produce a high bonding strength

between the reinforcement and cement matrix. SEM showed that carbon Nanotubes act

as bridges across voids and micro and Nano cracks which is thought to be the reason of

improvement the tensile strength for the cement composites (13).

16

Giuseppe Ferro et al. (2011) studied the effect of adding CNT into cement paste and

its effect on its mechanical and electrical properties. They concluded that the high

amount of lattice defects and carboxylic groups can cause a strong hydrophilic behavior

that is probably responsible for the incomplete hydration of cement paste added with

carbon Nanotubes which initially retained the water during concrete preparation and

then released it progressively during air curing. Fidure 2.2 shows the interaction

between COOH-MWCNTs and water molecules during cement hydration process(49).

Figure ‎2.2: Interaction between COOH-MWCNTs and water molecules during

cement hydration process.(49)

Hamed Younesi Kordkheili et al. (2011) investigated the physical and mechanical

properties of cement composites by mixing multi-wall carbon Nanotubes (MWCNT)

and bagasse fiber. Three percentages 0.5 wt.%, 1 wt.% and 1.5 wt.% of MWCNT were

mixed with 10 wt.% and 20 wt.% of bagasse fiber in rotary type mixer. The paper

evaluated thickness swelling, bending characteristics, water absorption and impact

strength of the samples. The physical tests indicated that increasing MWCNT content

decreased maximum water absorption and thickness swelling content of bagasse fiber

in cement composites. Also the samples with 20% bagasse fiber exhibited higher water

absorption and thickness swelling values, increase in flexural modulus and decrease in

flexural strength as compared to those made from 10% bagasse fiber.

Tests indicated that carbon Nanotubes had positive effect on flexural modulus and

strength of the samples. Adding 0.5% carbon Nanotubes increased the un-notched

impact strength of bagasse fiber in cement composites but CNT in percentage from 1%

17

to 1.5% decreased such property. In general, the composites containing 10% bagasse

fiber displayed higher impact strength than those containing 20% fiber (50).

Bryan M. Tyson et al. (2011) studied the effect of adding carbon Nanotubes and

carbin Nanofibers to cement composites to enhance their effect on the mechanical

properties. Untreated CNTs and CNFs are added to cement matrix composites in

concentrations of 0.1 and 0.2% by weight of cement. The nanofilaments are dispersed

by using an ultrasonic mixer and then cast into molds. SEM micrographs showed that

CNF acts as bridging across mtcro cracks. CNTs or CNFs showed poor dispersion

within the cement matrix. What causes the poor dispersion was unknown; however, the

researchers proved that the writers feel that the size and agglomeration of cement grains

play a crucial role in the dispersion of nanofilaments within the cement matrix, as

illustrated in Figure 2.3(51).

Figure ‎2.3: Effect of cement grains on CNTs/CNFs dispersion; the large grains

create zones that are absent of Nanotubes/Nanofibers even after hydration has

progressed(51)

Rashid K. Abu Al-Rub et al. (2012) focused on the effect of flexural strength and

ductility in cement pastes for different concentrations of long multi-walled carbon

Nanotubes (MWCNT) with high length/diameter aspect ratios of 1250–3750, and short

MWCNT with aspect ratio of about 157. Flexural strength are evaluated for the

cement/CNT composites at ages of 7, 14, and 28 days. Results showed that the flexural

strength of short 0.2 wt.% MWCNT and long 0.1 wt.% MWCNT increased by 69% and

65%, respectively, compared to the control cement sample at 28 days. The optimum

increase in ductility at 28 days for the short 0.1 wt. % and 0.2 wt. % MWCNT was 86%

and 81%, respectively. It is concluded that Nano composites with long MWCNT with

low concentration give high mechanical performance to the Nano composites compared

to higher concentration of short MWCNT(5).

18

Sergey Petrunin et al. (2013) reported the effect of multi-wall carbon Nanotubes on

the strength and structure of Portland cement composites by addition of carboxylate.

The study concluded that the optimum compressive strength of 64 MPa (20% increase)

was observed in the composite with 0.13% (by the cement weight) of MWCNT. By

consequence, It was found that grafting of carboxylate on the surface of the Nanotubes

accelerates the hydration of Portland cement and improves early strength. The addition

of carboxylate MWCNT at a very low dosage (0.05% by the cement weight) increased

by 30% for 1-day compressive strength by compared to the control mix (52).

Babak Fakhim et al. (2013) predicted the impact of multiwalled carbon Nanotubes on

the cement hydration products and investigated improvement the quality of cement

hydration products microstructures of cement paste. They concluded from the

micrographs of TGA test that the cement hydration was enhanced in the presence of the

optimum percentage of MWCNT. Increase in MWCNTs while the water/cement ratio

of matrix was held constant, due to the presence of hydrophilic groups on the MWCNT

surfaces and consequently absorption of a non-negligible amount of water, caused

hampering of the hydration of the cement mortar and agglomerating MWCNTs in the

form of clumps(4).

H. K. Kim et al. (2013) presented the results of the effect of carbon Nano tubes on

mechanical and electrical properties of cement composites such as the flow, porosity,

and compressive strength by mixing it with silica fume. Three amounts of CNT (0%,

0.15%, and 0.3% by weight of cement) were added to silica fume in amounts of 0%,

10%, 20%, and 30% by weight of cement.

It concluded that the mix between silica fume and CNT achieved an effective

dispersion for CNT in the cement matrix, which effected well on the mechanical and

electrical properties of cement composites. In the case of the cement composites

without silica fume, the relative values of compressive strength were gain 2% and loss

7% for 0.15 wt. % and 0.3 wt. % CNT additions, respectively. These values were

increased to 32% gain and 12% gain when silica fume was added by 10%. Even when

20% of silica fume was added, the relative values of the compressive strength of

cement composites containing 0.15 wt. % and 0.3 wt.% of CNT were both 15% gain,

which is higher than those of cement composites without silica fume. However, when

silica fume addition was increased to 30%, the relative value of the compressive

strength of cement composites containing 0.3 wt.% caused 6% loss, while that of

cement composites containing 0.15 wt.% caused 16% gain. These results indicated that

the effect of silica fume improved the compressive strength of the cement composites in

addition to CNT. However, when a large amount of silica fume was added (more than

30%), most carbon Nano tubes agglomerations were dispersed densely in silica fume

fields and re-agglomerated as clumps(53).

Baomin Wang et al. (2013) investigated the flexural toughness of MWCNT reinforced

cement composites. The results showed that the addition of CNT improved Portland

19

cement pastes flexure toughness. It increased up to 57.5% for a 0.08 wt. % addition of

MWCNT by weight of cement. The porosity and pore size distribution results indicate

that cement paste containing MWCNT had lower porosity and a more uniform pore size

distribution. The morphological structure of samples showed that MWCNT act as

bridges across micro and Nano cracks and voids and form a network that transfers the

load in tension (12).

Rafat Siddique et al. (2014) presented an overview of some of the research published

on the use of CNT in concrete or mortars. It studied the effect of CNT on properties

such as compressive strength, tensile strength, modulus of elasticity, flexural strength,

porosity, electrical conductivity and shrinkage. The following conclusions had been

drawn from this investigation; CNT have excellent properties in medical, electrical and

construction fields. Cement pastes reinforced with CNT its Young's modulus found to

be higher than the control cement paste. From the SEM micrographs the CNT were

dispersed uniformly in the cement mortar and there was no CNT agglomeration. the

porosity of the pastes decreased also the shrinkage values were found to be lower than

the control pastes. Also there was good interaction between carbon Nanotubes and the

fly ash cement matrix which acts as filler resulting in a denser microstructure and gives

higher strength when compared to the reference fly ash mix without CNT.

Increase of fly ash mixes has been observed with increase in carbon Nanotubes content

with the highest strength achieved with CNT content of 1% by weight. Also the

compressive strength increases with the inclusion of CNT under high strain loading

rate. There was increase in flexure strength when adding CNT compared to the control

cement paste but with higher aspect ratio of CNT, flexural strength found to be

dependent on concentration of CNT. CNT were found to be better than carbon fibers in

enhancing flexure strength (54).

Although numerous papers have studied the influence of carbon Nanotubes on the

properties of cement composites, their effects have not been adequately characterized

yet, and some discrepancies and inconsistencies in compressive and flexure strength

results are witnessed.

2.4.3. Influence of carbon Nanotubes addition on concrete properties

R. Hamzaoui et al. (2012) studied the mechanical properties and microstructure of

mortar and concrete using Carbon Nanotubes (CNT) at 7, 14, 28 and 90 curing days.

Part of the formulation, CNT is dispersed in a liquid solution. Different concentrations

ranging from 0.01% to 0.06% and 0.003% up to 0.01% are used for mortar and

concrete, respectively. Mechanical testing of the modified materials reveals that

maximum compressive strength is obtained for CNT concentrations close to 0.01%wt

and 0.003%wt for mortar and concrete, respectively. The microstructural

characterization of the modified materials suggests that CNT act as bridges between

21

pores and micro and Nano cracks leading to a reduction in porosity and in turn an

increase of compressive strength. The outcomes of the work were:

For mortar, the following concentration were tested 0.01%, 0.02%, 0.03%, 0.06% CNT

of cement weight. it is found that the largest compressive strength when adding 0.01%

of CNT. Also, the gain in the compressive strength for the optimal CNT percentage at

90 days curing in water was 21.2% higher compared to the control batch. However,

further increasing of CNT degrades the compressive strength of mortar.

For concrete, CNT of percentages 0.003%, 0.006%, and 0.01% (by cement weight) was

added to the concrete at 90 days curing time. The maximum compressive strength was

reached for a CNT percentage of 0.003% by cement weight. The gain in compressive

strength was 17.65% with regards to the control batch. The same trend of strength

degradation was observed using a larger amount of CNT (55).

2.5. Difficulties facing CNT usage in concrete

2.5.1. Carbon Nanotubes agglomeration

Grigorij Yakovelv et al. (2006) studied the carbon Nanotubes, synthesized from

aromatic hydrocarbons and the possibilities of production and main technological

properties of Portland cement based foam concrete reinforced by dispersed carbon

Nanotubes. The method of stimulation of dehydropolycon-densation and carbonization

of aromatic hydrocarbons in chemical active environment (melts of aluminum, copper,

nickel, iron salts) was used for carbon Nanotubes synthesis. The results of investigation

of the synthesized carbon Nanotubes by X-ray photoelectron spectroscopy showed that

they contain (80 – 90) % of carbon. The examination of the carbon Nanotubes

microstructure by electron microscope showed that the Nanotubes have a cylindrical

form with diameter up to 100 nm and length up to‎ 20‎ μm.‎ The‎ Nanotubes‎ were‎

agglomerated‎due‎to‎van‎der‎Waals‎forces‎with‎a‎diameter‎up‎to‎30‎μm‎and‎a‎length‎up‎

to 10 mm. The carbon Nanotubes were used as a high strength dispersed reinforcement

for production of foam non-autoclave concrete produced on the base of Portland

cement. The results of the investigation of the reinforced non-autoclave cement foam

concrete showed that the use of 0.05% carbon Nanotubes by cement weight in

production of these concretes decreases its heat conductivity up to (12 – 20) % and

increases its compressive strength up to 70 %(56).

Jyoti Bharj et al. (2014) discussed the role of dispersion of multi walled carbon

Nanotubes (MWCNT) on the compressive strength of Portland cement paste. Cement-

MWCNT composites were prepared by adding 0.2% (by cement weight) of MWCNT

to Portland cement. Rectangle specimens of size approximately 40mm × 40mm

×160mm were prepared and curing of samples was done for 7, 14, 28 and 35 days.

Water cement ratio was 0.4.

21

The study concluded that due to van der Waals forces resulting from large surface area

of MWCNT, they tend to adhere together causing agglomeration in the cement

composites and it becomes extremely difficult to separate them. Powder mixing of

MWCNT and cement was not suitable for uniform and effective dispersion. The gain in

the compressive strength of cement MWCNT-cement composite was found to be

around 8.2% compared to pure cement composites. Good quality of the CNT water

dispersions significantly affected the mechanical properties of the composite materials.

In aqueous mixing method sonicator was used for mixing the MWCNT within DI water

and breaking the van der Waals forces between the tubes. An increase in compressive

strength up to 22% was observed when CNT were dispersed In DI water with

sonication compared to pure cement composites (9).

2.5.2. Mixing and dispersion methods

Maria S. Konsta-Gdoutous et al. (2008) studied the effect of dispersed MWCNT in

water on the properties of cement paste by applying ultrasonic energy with adding a

commercial surfactant. Results had been showed that ultrasonic achieved good

dispersion for CNT specially when adding the commercial surfactant to CNT with a

weight ratio (CNT to surfactant) within the range of 4 to 6.25(57).

G. T. Caneba et al. (2010) showed a double ultrasonic source to increase carbon

Nanotubes dispersion. In this study, nonlinear wave resonance concepts had been

proposed to contain explanations for the dramatic increase in dispersion performance,

and more specifically, the effect of intermittency chaos. Such a hypothesis was made

because of the similarity between the pressure wave pattern in the double sonication

system and sliding charge density wave with an A.C. electric field, which was cited to

exhibit intermittency behavior. The double ultrasonic source (bath and probe) had been

shown to efficiently disperse carbon Nanotubes, compared to using just the ultrasonic

bath or probe. Acoustics energy analysis based on wave superposition principle had

been shown to be inconsistent with such a dramatic increase in dispersion performance.

Resonance effects in the form of intermittency chaos had been proposed as the likely

theoretical reason for this behavior, which had actually been shown to occur in systems

with two interlocking waves (15).

Anastasia Sobolkina et al. (2012) studied the effect of the dispersion for two types of

carbon nanotubes having different morphologies to improve the mechanical properties

of cement composites. The first type was a mixture of single, double, and multiwalled

CNTs and the second type was aligned, nitrogen-doped, multi-walled CNTs (N-CNTs).

CNTs are difficult to disperse in water because of their strongly hydrophobic surface.

In order to reduce the surface tension and to improve the wetting of the CNTs, The

dispersion in water of two different types of CNTs was investigated by sonication in the

presence of the following surfactants (58; 59): an anionic sodium dodecyl sulfate (SDS)

and a nonionic polyoxyethylene laurylether (Brij 35) due to their good dispersive

22

capacity. The most effective dispersions could be produced with a CNT to surfactant

ratio of 1:1–1:1.5 and sonication time of 120 minutes. For the N-CNTs a combination

with the surfactant Brij 35 led to a particularly intensive deagglomeration, which can be

attributed to the good affinity between the Brij 35 molecules and the surfaces of the N-

CNTs and consequently a homogeneous coating of CNT-surfaces. CNTs were unable

to bond neighboring C–S–H clusters and to bridge the voids between them. Figure 2.4

shows the arrangement of CNTs in a cement matrix (60).

Figure ‎2.4: Schematic representation of the arrangement of CNTs in a cement

matrix: advantageous (a and c) and disadvantageous (b and d) distribution of the

mixed CNTs and N-CNTs, respectively.(60)

Guido Pagani et al. (2012) studied the dispersion of CNT into liquids using

ultrasonication. The study concluded that the propensity of a CNT to rotate into radial

alignment during bubble collapse depends on its length. There are 3 behaviors for CNT

under the effect of sonication as shown in figure 2.5; short CNTs rotate radially and

stretch, nearby CNTs align tangentially during growth of the bubble nucleus and long

CNTs remain tangentially and buckle(61).

23

Figure ‎2.5: Overall schema for CNT breaking. CNTs near the bubble nucleus

(green region) align tangentially during bubble (blue) growth. During collapse,

CNTs may rotate radially and stretch or buckle depending on their length.(61)

Dr. T. Ch. Madhavi et al. (2013) discussed the effect of multi-walled carbon

Nanotubes (CNT) on strength characteristics and durability of concrete. Sonication

process was carried out by adding MWCNT with surfactants (super plasticizers -

polycarboxylate 8H), 0.25% by weight of cement and also with water. 36 Specimens

with MWCNT of 0.015%, 0.03% and 0.045% of cement (by weight) were tested after

28 days of curing. Results showed an increase in compressive and splitting-tensile

strengths of the samples with increasing MWCNT. 0.045% of MWCNT had improved

the 28 days compressive strength by 27 % while the split tensile strength increased by

45%. Crack propagation was reduced and water absorption decreased by 17% at 28

days curing(62).

Wpływ Nanorurek Węglowych et al. (2014) investigated carbon Nanotubes effect on

the compressive strength of cement composites. The study reported that the biggest

problem in the preparation of cement composites containing CNT was their proper

dispersion in the composites. Ultra sonication method helped to resolve the problem of

dispersion and tendency to aggregation of carbon Nanotubes. The additive of amount

0.06% CNT by cement mass in cement mortars caused an increase in the compressive

strength almost 30%. The introduction of CNT into cement mortar caused a decrease in

the 7 day compressive strength. However, the significant increase in strength more than

68% for CNT content 0.06% by weight of cement was gained between 7th and 28th

days of curing(63).

24

2.5.3. Superplasticizers compatibility

The real effect of the superplasticizer is to maintain individual CNT separated by

electrostatic repulsion between SP negatively charged particles and negative functional

groups on CNT surface. The high amount of superplasticizer defects and carboxylic

groups can justify a strong hydrophilic behavior that is probably responsible for the

incomplete hydration of cement paste added with carbon Nanotubes which initially

retained the water during concrete preparation(64).

Frank Collins et al. (2011) reported the results of investigations of the dispersion,

workability, and strength of CNT aqueous and CNT–OPC paste mixtures, with and

without several generically different dispersants/surfactants that are compatible as

admixtures in the manufacture of concrete. These included an air entrained, styrene

butadiene rubber, polycarboxylates, calcium naphthalene sulfonate, and lignosulfonate

formulations. Aqueous mixtures were initially assessed for dispersion of CNT,

followed by workability testing of selected OPC–CNT-dispersant/surfactant paste

mixtures. The outcomes of the work were; CNT in aqueous solutions agglomerate

despite mechanical agitation by magnetic stirring and ultra-sonication. Ultra-sonication,

polycarboxylate and lignosulfonate admixtures provided good dispersion of CNT in

aqueous solutions. Styrene butadiene rubber and calcium naphthalene sulfonate

admixtures facilitated rapid agglomeration of CNT; SEM analysis confirmed the

presence of agglomerates of CNT which cause lower compressive strength.

Addition of CNT to OPC paste mixtures reduced consistency and strength. Cement

paste containing CNT consistency was improved in the case of polycarboxylate

admixture addition, with highly flow able mixtures achieved when w/c was lower than

0.35. At w/c of 0.35, the compressive strength of CNT-OPC-PC increased by 25%

higher than reference mixtures which was observed by SEM analysis. The active non-

polar groups within the polycarboxylate molecule disperse CNT (non-polar) while

polar groups disperse cement and water, thereby creating stable dispersions (65).

Oscar Mendoza et al. (2013) studied the effect of superplasticizer and Ca(OH)2 on the

stability of OH functionalized multi walled carbon Nanotube dispersed in water

produced via sonication. It was concluded that Ca(OH)2 affects the stability of

MWCNT dispersions because of its interaction with negative charges of the OH

functional groups, which prevents the electrostatic repulsion between MWCNT and

superplasticizer molecules, generating re-agglomeration of the MWCNT. Sonication is

an effective method for the dispersion of MWCNT to decrease its aspect ratio, but a

balance between the degree of damage induced by it and the dispersion level desired is

required to guarantee that the MWCNT has a convenient mechanical performance when

used in a cement matrix and exposed to tensile strengths. The real effect of the SP

particles is to maintain individual MWCNT separated by electrostatic repulsion

between SP negatively charged particles and negative functional groups on MWCNT

surface. A polycarboxilate super plasticizer or an anionic dispersant is not the most

25

adequate dispersant to generate stable MWCNT to be applied in Portland cement

matrixes, because the alkaline Ca(OH)2 rich environment generated during cement

hydration prevents the SP adsorption onto the MWCNT surface generating re-

agglomeration effects which hinders the electrostatic repulsion between MWCNT

functional groups and SP molecules that maintains individual MWCNT separated(66).

Tomáš Jarolím et al. (2014) aimed to disperse of carbon Nanotubes in aquaeous

solution with use of proper surfactant to produce efficient dispersion. Magnetic stirring

and ultra-sonication was used. The quality of dispersion was examined through

ultraviolet and visible spectroscopy and scanning electron microscopy. Samples of

cement mortar reinforced with carbon Nanotubes were made and their tensile and

compressive strength in the age of 7 and 28 days was tested. Conclusions of examined

physical-mechanical characteristics did not confirm increase in addition of CNT.

Experiments indicated that better compatibility of system superplasticizer, water and

CNT would happen when superplasticizer based on polycarboxylate will be used. This

paper recommended that other researchers should focus on find suitable surfactant and

methods of mixing suspension CNT and surfactant with bigger amount of water and its

influence to stability of whole system CNT-surfactant-water (67).

2.6. The coupled effect of NS and CNT on cement composites

Oscar Mendoza et al. 2014 studied the effect of the re-agglomeration process of Multi-

Walled Carbon Nanotubes (MWCNT) dispersions on the activity of silica Nano

particles at early ages when they were combined in cement matrix.

MWCNT/water/superplasticizer dispersions were produced via sonication and

combined with NS. The study concluded that the interaction of the OH– functional

groups (from the MWCNT) with the Ca(OH)2 re-agglomerated the MWCNT

dispersions, decreasing the surface area of the MWCNT and the NS available to work

as nucleation spots at early ages, and decreased the availability of Ca(OH)2 for the NS

to react with, to form additional C–S–H at latter ages. In general, the combination

between NS and MWCNT decreased the overall kinetics of the hydration reaction. The

combination of NS and MWCNT had an accelerating effect on the hydration reaction

during the first hour because the MWCNT worked as extra nucleation spots for the

hydration products. During the first 24 hours, the presence of individual MWCNT

worked as extra nucleation spots for the hydrates and enhanced the activity of the NS

especially when NS combined with low amount of MWCNT. After 24 hours, The

combination of NS and a high amount of MWCNT had negative effect on the hydration

reaction due to the re-agglomeration process of the MWCNT. By consequence, The

activity of the NS was accelerated, decelerated or completely inhibited depending on

the amounts of MWCNT. The combination of MWCNT with NS did not present any

significant positive effect on the flexural and compressive strengths of mortars after 1

and 3 days of hydration due to the re-agglomeration of MWCNT which decreased the

amount of C–S–H produced. For ANOVA analysis, the null hypothesis was that the

26

factors (MWCNT, NS and its interaction) had no effect on the flexural or compressive

strength of mortars. This indicated that the MWCNT did not work as Nano

reinforcement and affected the activity of the NS and the hydration of cement, at both

early and late ages (11).

Peter Stynoski et al. (201) studied the effect of micro silica additives on properties of

CNT-OPC mortar mixes. They concluded that the silica hindered an accelerating effect

of carbon Nanotubes during the first 24 h of cement hydration. The use of silica

increased the toughness of mixtures containing CNT, especially after 28 days of

hydration also improved the dispersion and bonding of CNTs in cement

composites(68).

2.7. Statistical Factorial Design in Concrete Research

Typically, a trial and error approach is used in selecting and testing a first trial batch,

evaluates the results, and adjusts the mixture proportions; based on deducted

relationships between the parameters (69), finally, re-test the chosen adjusted mixture.

This process is repeated until the required properties are achieved, which may involve

carrying out a large and unpredictable number of trial batches. Statistical experimental

design is an effective scientific and efficient approach for establishing a mixture while

minimizing the number of experimental data points (70). Models are valid for a wide

range of mix proportioning and have a predictive capability for the responses of other

points located within the experimental domain. This design approach was followed by

other authors for various purposes to design and optimize the mixtures, to compare the

responses obtained from various test methods, to analyze the effect of changes in the

parameters and to evaluate trade-offs between key mixture parameters and constituent

materials. Factorial design is widely used in experiments involving many factors. That

is, to study the joint effect of the parameters or factors on responses or dependent

variables, and, to develop models applicable to design and development of experiments

(16).

Soudki et al. (2001) presented the results of a statistical analysis objected to optimize a

concrete mix design for hot climates. A full factorial experiment was used with 3 · 4 x

4 · 3 treatment combinations (432 samples) of 48 mixes at three levels of temperature.

The influences of the water/cement ratio (0.40, 0.50, and 0.60), coarse aggregate/total

aggregate ratio (0.55, 0.60, 0.65, and 0.70), total aggregate/cement ratio (3.0, 4.0, 5.0,

and 6.0), and temperature (24, 38, and 52 o C) on compressive strength were analyzed

using polynomial regression. Polynomial models were developed for concrete strength

as a function of temperature and mix proportion. The optimum concrete mix for

different temperatures was found as well as the mix that is least sensitive to temperature

variations (71).

27

Al Qadi Arabi et al. (2009) used a statistical modeling to solve the influence of key

mixture parameters (cement, water to powder ratio, fly ash and super plasticizer) on the

hardened properties affecting the performance of SCC. The models were valid for a

wide range of mixture proportioning. The derived numerical models used to reduce the

test procedures and number of trials of mix proportioning of SCC. The researchers

concluded that full quadratic models in all the responses resulted the best models (72).

Luciano Senff et al. (2010) reported the effects of Nano silica (NS) and silica fume

(SF) on the compressive strength, water absorption, apparent porosity, and unrestrained

shrinkage and weight loss of mortars up to 28 days curing. Samples with NS (0–7

wt.%), SF (0–20 wt.%) and water/cement ratio (0.35–0.59), were modeled through

factorial design experiments. Nanosilica with 7 wt. % showed the fastest formation of

structures during the rheological measurements. The structure formation influenced

more yield stress than plastic viscosity and the yield stress related well with the spread

on table. Compressive strength, water absorption and apparent porosity showed a lack

of fit of second order of the model for the range interval studied. In addition, the

variation of the unrestrained shrinkage and weight loss of mortars did not follow a

linear regression model. The maximum unrestrained shrinkage increased 80% for NS

mortars (7 days) and 54% (28 days) when compared to SF mortars in the same periods

(73).

Fábio de Paiva Cota et al. (2012) studied the effect of adding carbon nanotubes on the

mechanical properties of polymer-cement composites. A full factorial design had been

performed on 160 samples to identify the contribution provided by the following

factors: polymeric phase addition, CNT weight addition and water/cement ratio. The

response parameters of the full factorial design were the bulk density, apparent

porosity, compressive strength and elastic modulus of the polymer-cement-based

nanocomposites. The study concluded that carbon Nanotubes caused reduction in the

bulk density, the mechanical strength and the modulus of elasticity of the cement

composites, and increased the apparent porosity. The microstructural analysis revealed

a good interface condition between the CNT cluster and cement phase besides the

presence of unhydrated cement grains(74).

M. Sonebi and M. T. Bassuoni (2013) investigated the effect of mixture design

parameters on concrete by statistical modeling. In this study, the effects of water-to-

cement ratio (W/C), cement content and coarse aggregate content on the density, void

ratio, infiltration rate, and compressive strength of Portland cement concrete (PCC)

were modeled by statistical modeling. Two-level factorial design and response surface

methodology (RSM) were used. The mixtures were made with w/c of 0.28–0.40,

cement content in the range of 350–415 kg/m3 and coarse aggregate content 1200–

1400 kg/m3. In addition, examples were given on using multi parametric optimization

to produce a desirability function for satisfying specified criteria including cost. The

results showed that w/c, cement content, coarse aggregate content and their interactions

are key parameters, which significantly affect the characteristic performance of the

28

mixtures. The statistical models in this study facilitated optimizing the mixture

proportions for target performance by reducing the number of trial batches needed (75).

29

Chapter 3 : Experimental Program

3.1. General

The major problem in utilizing Nano-particles is that they are highly agglomerated

particles which cause loss in their high-surface area due to grain growth. Effective de-

agglomeration and dispersion for Nano-particles is needed to overcome the bonding

Van Der Waals forces after wetting which results in the formation of agglomerations in

the form of entangled ropes and clumps that are very difficult to disentangle. The

dispersion problem has been combated by methods like using surfactants, usually in

combination with sonication.

The present study focuses on the effectiveness of superplasticizers (high-range water-

reducing admixtures) and ultrasonic processing (direct/indirect) for the purpose of

dispersing carbon Nano tubes in water and finally pastes. A qualitative analysis using

compressive and flexure strength tests will be conducted in order to investigate the

effect of dispersion on the mechanical properties of cement composites in corroborating

Nano silica and CNT with different dosages.

In addition TEM images, XRD analysis and zeta potential distribution will be carried

out to observe the surface morphology and microstructure of cement composites with

different amounts of Nano silica and CNT addition. Finally, statistical surface response

model will be introduced correlating the percentage of both, nano silica, and CNT with

the compressive strength of cement mortars, and the effects of studied parameters will

be characterized and analyzed using ANOVA and regression models, which can

identify the primary factors and their interactions on the measured properties. Finally

the optimization software searches for the greatest overall desirable percentages of the

nano silica and CNT which enhances the cement matrix.

3.2. Overview of Experimental Program

The experimental test program is designed to achieve the research objectives; the

experimental program is divided into two major phases:

In the first phase, the objective is to provide guidelines for optimizing the dispersion

process of Nano silica and carbon Nanotubes using direct and indirect sonication.

http://www.hielscher.com/ultrasonics/disperse.htm

31

A. For Nano silica, it consists of two stages:

The first stage is directed to determine the optimum sonication method of NS particles

dispersion out of direct or indirect sonication. 8 samples are conducted in order to study

the effect of the process parameters on the product quality. The first control sample is

chosen to study the particle sizes of Nano silica without sonication. Three samples

study the effect of direct sonication at 3 different times of sonication (1 min, 3 min, 6

min). The last 4 samples study the effect of indirect sonication at 4 different times (1

min, 3 min, 6 min, 9 min). All other sonication parameters are set for sonication power

100%, frequency 40 KHz and Nano silica/water concentration (1:5) constant for both

direct and indirect sonication. The test setup is a 20 gm. of Nano silica added to 100 ml

water in a flat base glass beaker, and then the beaker is put into the bath sonicator.

The second stage is dedicated testing the compressive and flexure strength after 7 and

28 days for 18 mortar mixes (5*5*5 cm3) by changing the sonication time (from 1.5 to

18 minutes) for different Nano silica amounts (0.5%, 1%, 1.5%, 2% and 2.5% by

cement weight). Cement content is 1 kg, sand is 2 kg, 0.4 w/c and 0.4 wt.%

superplasticizer. Mixes are prepared of cubes and prisms. Guidance and evaluation of

experimental program of the preparation of Nano silica particles are made through

particle size distribution, scanning electron microscope (SEM), X-ray diffraction

(XRD) and thermo gravimetric analysis (TGA).

B. For carbon Nanotubes dispersion, it consists of two stages:

The first stage is directed to determine the optimum sonication method of CNT

particles dispersion out of direct or indirect. The basic properties of carbon Nanotubes

are‎ extreme‎ tensile‎ strength‎ and‎Young’s‎modulus‎of‎ elasticity,‎ high‎aspect‎ ratio‎ and‎

huge specific surface area. Because of this, CNT tend to aggregation and cluster

formation. When load is applied on the composite, those clusters behave like filler with

very poor mechanical properties, causing decrease of both tensile and compressive

strength. Perfect dispersion of CNT is essential to avoid this problem (67). 10 samples

are conducted in order to study the effect of the process parameters on the product

quality. The first control sample is chosen to study the particle sizes of carbon

Nanotubes without sonication. Four samples study the effect of direct sonication at 4

different times of sonication (2 min, 3 min, 6 min, 9 min). The last 5 samples study the

effect of indirect sonication at 4 different times (3 min, 6 min, 9 min, 12 min, 18 min).

All other sonication parameters will be set for sonication power 100%, frequency 40

KHz and carbon Nanotubes/water concentration (1:500) constant for both direct and

indirect sonication. The test setup is a 0.1 gm. of carbon Nanotubes added to 50 ml

water in a flat base glass beaker, and then the beaker is put into the bath sonicator.

31

A study is conducted to improve CNT particles dispersion in water by adding NS and

superplasticizer. Some researchers study the effect of using superplasticizer or other

surfactants on the dispersion of CNT(65; 67). After determine the optimum time and

method of sonication for Nano silica and carbon Nanotubes; 3 samples are chosen, each

sample is a set of pastes cubes (5*5*5 cm3). The paste contained of 523 g cement,

water/cement ratio is 0.6, CNT% and NS% are 0.02% and 1% respectively of cement

weight. Cement, Nano silica and carbon Nanotubes are put in the bath sonicator each in a

separate glass beaker depending on its time of sonication. Then, all components are

mixed together and casted in molds 5*5*5 cm3 to examine the pastes compressive

strength after 7 days.

The second stage studies the optimum dispersion for CNT by adding superplasticizer to

optimize the optimum mixing sequence of CNT within cement matrix. Ten samples are

conducted to study different methods of treatment for carbon Nanotubes by examine

compressive strength of cement pastes.

8 samples of cement pastes are prepared of sets of cubes for each method (5*5*5 cm3).

The paste contained of 523 gm., water/cement ratio is 0.4, 0.02% CNT% of cement

weight and 0.4 wt. % SP. The first sample is chosen to study the compressive strength of

a paste contained of cement, water and SP. The second sample studies the compressive

strength of a paste by adding carbon Nanotubes without sonication and SP. The last 6

samples examine the compressive strength for different methods of carbon Nanotubes

dispersion in water using indirect sonication and homogenizer. The first method is 1 hr.

sonication; the second 1 hr. homogenizer, the third 40 min. sonication then 10 min.

homogenizer, the forth 10 min. homogenizer then 40 min. sonication, the fifth 40 min.

homogenizer then 10 min. sonication and the sixth 30 min. sonication then 30 min.

homogenizer.

In the second phase investigates the effect of dispersion on the mechanical properties

of cement composites incorporating Nano silica and CNT with different dosages, it

consists of two stages:

The first stage tests the effect of different amounts of CNT (0.01%, 0.02% and 0.03%

of cement weight) on 3 samples of cement mortar mixes and prisms. Cement content is

1 kg, sand is 2 kg, 0.4 w/c and 0.4 wt. % superplasticizer. Compressive and flexural

strength are evaluated for the samples after 7 and 28 days of water curing. The

optimum method of sonication for CNT is chosen from the previous studies. Guidance

and evaluation of experimental program of the dispersion of carbon Nanotubes particles

are made through particle size distribution, scanning electron microscope (SEM), X-ray

diffraction (XRD), transmission electron microscope (TEM) and thermo gravimetric

analysis (TGA).

32

The second stage studies the couple effect of NS and CNT on cement mortars after

determining the final time and method of sonication for each component. 15 mortar

mixes of different percent of Nano silica and carbon Nanotubes are chosen to prepare

cement mortars and test its compressive and flexural strength. Nano silica contents are

(0.5%, 1%, 1.5%, 2%, and 2.5%) by cement weight, carbon Nanotubes contents are

(0.01%, 0.02%, and 0.03%) by cement weight. Cement content is 1 kg, sand is 2 kg, 0.4

w/c and 0.4 wt.% superplasticizer. Set of cubes and prisms are prepared for testing

compressive and flexure strength after 7 and 28 days.

3.2.1. Characterization of Used Materials

Ordinary Portland Cement (OPC) conforming to ASTM C150 standard is to be

used as received. The chemical and physical properties of the cement are shown

in table 3.1.

Table ‎3.1: Properties of Portland cement (wt. %)

Element Sio2 Al2O3 Fe2O3 CaO MgO SO3 Na2O K2O L.O.I

Cement 20.13 5.32 3.61 61.63 2.39 2.87 0.37 0.13 1.96

Property Result

3 days Compressive strength 156.6 kg/cm2

7 days Compressive strength 195.7 kg/cm2

SiO2 amorphous and agglomerated Nano particles with average particle size of

30 nm and 45 m2/g Blaine fineness produced from WINLAB laboratory

chemicals, UK is to be used as received. The chemical properties of SiO2 Nano

particles are shown in table 3.2. Transmission electron micrographs (TEM) and

powder X-ray diffraction (XRD) diagrams of Nano silica particles are shown in

Figures 3.1 and 3.2.

33

Table ‎3.2: Chemical composition of Nano silica (wt %)

Element SiO2 Fe2O3 Al2O3 MgO CaO Na2O P2O5

NS 99.17 0.06 0.13 0.11 0.14 0.40 0.01

Figure ‎3.1: TEM micrograph of SiO2 Nano particles

34

.

Figure ‎3.2: X-ray diffraction (XRD) analysis of SiO2 Nano particles

Two types of multi walled (MWCNT) carbon Nanotubes (CNT) are to be used;

Imported CNT is to be used in the first phase, while local CNT is to be used in

the second phase. Transmission electron micrographs (TEM), X-ray diffraction

(XRD) and scanning electron microscope (SEM) of imported and local carbon

Nano tubes particles are shown in figures 3.3, 3.4, 3.5, 3.6 and 3.7.

Figure ‎3.3: TEM micrograph of local carbon Nano tubes particles

35

Figure ‎3.4: X-ray diffraction (XRD) of local carbon Nano tube particles.

Figure ‎3.5: Scanning electron microscope (SEM) of local carbon Nano tube

particles

36

Figure ‎3.6: Transmission electron microscope (TEM) micrograph of imported

carbon Nano tubes particles

Figure ‎3.7: Zeta potential distribution of imported carbon Nano tube particles

37

The sand used in mortars is free of alkali-reactive materials to insure producing

durable composites. Figure 3.8 shows the sieve analysis of fine aggregate as

compared to the Egyptian code of practice limitations.

The water used in the mix design is potable water from the water-supply

network system, free from suspended solid and organic materials, which can

affect the properties of the fresh and hardened concrete.

A polycarboxylate with a polyethylene condensate de-foamed based admixture

(Glenium C315 SCC) is used. Table 3.3 shows some of the physical and

chemical properties of polycarboxylate admixture used in this study. The

superplasticizer type is chosen for its electrostatic-steric behavior to be more

effective with Nano silica and carbon Nanotubes dispersion as mentioned in

different researches.

Table ‎3.3: Physical and chemical characteristics of the polycarboxylate admixture

Appearance Off white opaque liquid

Specific gravity @ 20°C 1.095 ± 0.02 g/cm3

PH-value 6.5 ± 1

Alkali content (%) Less than or equal to 2.00

Chloride content (%) Less than or equal to 0.10

Figure ‎3.8: Sieve analysis for fine aggregates as compared to the limits of the

Egyptian code of practice

38

3.2.2. Characterization of Used Equipment

A. Probe Sonicator,

Direct sonication is achieved through ultrasonic probe shown in figure 3.9, which is

immersed into sample, performing ultrasonication over the solution directly without

any barrier to be crossed by the ultrasonication wave other than the solution itself as

bath sonicator. This approach has several drawbacks. Sample contamination with

metals detaching from the probe can be expected. Although modern ultrasonic probes

are made from high purity titanium, contamination by metals such as Cr or Al has been

reported. Modern ultrasonic probes made from glass which highly reduces this

problem. Another disadvantage that most ultrasonic probes are used in open

approaches, that is, the sample container is not covered during sample treatment,

consequently, some volatile analytes can be lost (17; 76; 77).

Figure ‎3.9: Probe Sonicator

B. Bath Sonicator,

A modern ultra-sonication bath is used to perform the proposed study, the used bath

sonicator is produced by FALC instruments, Italy, see figure 3.10, and has the

properties, and specifications mentioned in table 3.4.

39

A bath sonicator full of water is set to the specified time, 40 KHz frequency and 100%

power‎of‎sonication.‎Temperature‎is‎set‎to‎20˚C‎and‎tank‎temperature‎not‎exceeds‎40˚C.‎

Water level should pass the heating level to avoid solution evaporation. A bath

sonicator with heater is recommended because a long time sonication increases the

liquid temperature. In a sonication bath (indirect sonication), the ultrasonic waves must

pass through the bath liquid and then the wall of the sample container before reaching

the suspension.

The shape of used beaker is critical for the correct application of ultra-sonication with a

bath. This is because, as with any other wave, some energy is reflected when the

ultrasonic wave crashes against any solid surface. If the base of the container is flat,

such as in a conical flask, the ultrasound reflected is a minimum. On the contrary, when

the base of the container is spherical the ultrasonic wave hits the container at an angle,

and a huge proportion of the ultrasonic wave is reflected away.

The solvent used to fulfill sample treatment with ultra-sonication must be chosen

carefully. In general, most applications are performed in water. However, other liquids,

such as some types of organics, can be used, depending on the destined purpose. Both

solvent viscosity and surface tension are required to prevent cavitation, as the higher

the natural cohesive forces acting within a liquid (e.g., high viscosity and high surface

tension) are difficult to attain cavitation.

The sonication intensity is proportional to the ultrasonic source vibration amplitude

and, as such, an increase in the vibration amplitude will lead to an increase in the

vibration intensity. A minimum intensity is required to achieve the cavitation threshold.

This means that higher amplitudes are not always necessary to obtain the desired

results. In addition, high amplitudes of sonication can lead to rapid deterioration of the

ultrasonic transducer, occurring in liquid agitation instead of cavitation and in poor

transmission of the ultrasound through the liquid. However, the amplitude increase is

strongly required when working with samples of high viscosity, such as blood, because

when the viscosity of the sample increases the resistance of the sample to the

movement of the ultrasonic device increases. Therefore, a high intensity is needed to set

the ultrasonic device to obtain the substantial mechanical vibrations to promote

cavitation in the sample.

Table ‎3.4: Bath sonicator properties and specifications

Capacity 3.5 liters

Drain with valve No

External dimension 320x170x230

Frequency KHz 40 - 59

41

Heating °C 20-80

Internal tank dimension 300x150x100

Peak Power 150 W

Absorbed Power 135 W

Power regulation 40-100 %

Timer 1-199 min

Weight 3.4 kg

Figure ‎3.10: Bath sonicator

C. High Speed Homogenizer,

Used in indirect sonication application, the ultrasonic wave needs first to cross the

liquid inside the ultrasonic device and then to cross the wall of the sample container.

Therefore, ultra-sonication intensity inside the sample container is lower than expected.

In order to overcome the mentioned problem, in the proposed study a mechanical

homogenizer shown in figure 3.11 will be used in addition to a modern bath sonicator

to perform production process in some samples.

The homogenizing has in common with ultra-sonication, that both methods generate

and use to some degree cavitation, although, in ultrasonic the object being moved is the

bath which is being vibrated at a very high rate of speed generating cavitation. In

homogenizing (rotor-stator), the blade (rotor) moves through the liquid at a high rate of

speed generating cavitation. The use of the homogenizer is thought to be as effective as

41

the conclusion reported by that the use of double cavitation sources (bath and probe)

has shown more efficiency in dispersing materials when compared to using the

ultrasonic bath or probe (15). The used homogenizer is a YELLOWLINE DI 25 basic,

manufactured by IKA, and having the properties in table 3.5.

Table ‎3.5: Rotor-stator homogenizer properties

Speed range (rpm) 8000 – 30000

Speed variation on load scale (%) < 1

Power consumption (Watt) 600

Power output (Watt) 350

Frequency (Hz) 50/60

Drive Dimensions WxHxD (mm) 77x66x221

Boom Dimensions (mm) Ø13/L160

Weight (Kg) 1.6

Perm. Ambient Temp (oC) 5 – 40

Perm. Humidity (%) 80

Perm. On time (drive unit) (%) 100

Figure ‎3.11: high speed homogenizer

42

3.2.3. Samples Preparation

The samples preparation is to be divided into four different phases complying with the

four main aims of the proposed thesis.

3.2.3.1. Optimizing the dispersion of materials (phase one)

The objective is to provide guidelines for optimizing the preparation process of cement,

carbon Nano tube and Nano silica using direct and indirect sonication to investigate the

best time and method of sonication. In order to do these different parameters are

studied; sonication power, sonication frequency, and sonication time.

A. Nano silica dispersion

The first stage; 8 Samples are prepared by adding 20 gm. of Nano silica in a glass

beaker to 100 ml of water for each time of sonication in a bath sonicator in case of

indirect sonication. Table 3.6 shows the constituents of Nano silica preparation

samples.

Table ‎3.6: Constituents of Nano silica preparation samples

SAMPLE SONICATION

METHOD

TIME

(min)

NS0 --- 0

NS1I Indirect 1

NS1D Direct

NS3I Indirect 3

NS3D Direct

NS6I Indirect 6

NS6D Direct

NS9I Indirect 9

Example:

NS1I: Nano silica/1 min/indirect sonication

NS16D: Nano silica/6 min/direct sonication

The second stage discusses the optimum method for Nano silica dispersion. Contents

of Nano silica used are (0.5%, 1%, 1.5%, 2% and 2.5%) by cement weight, and

sonicated for 1.5 min, 3 min, 4.5 min, 6 min, 7.5 min, 9 min, 12 min, 15 min and 18

min. Superplasticizer is 0.45% by cement weight and water cement ratio is 0.4. 18

mortar samples compose of cubes and prisms for compressive and flexure strength tests

after 7 and 28 days, water curing. Indirect sonication method is used. Table 3.7 shows

43

the constituents of the mixtures. The mixing sequence of the samples is mentioned in

figure 3.12.

Table ‎3.7: The second stage mixtures composition (gm.)

SAMPLE CEMENT SAND WATER S.P. N.S.%

SONICATION

TIME

NS 0/0 1000 2000 400

4.5 0 0

NS 0.5/1.5 1000 2000 400 4.5 0.5

1.5

NS 0.5/3 3

NS 1/3

1000 2000 400 4.5 1

3

NS 1/6 6

NS 1/9 9

NS 1/12 12

NS 1.5/3 1000 2000 400 4.5

1.5

3

NS 1.5/4.5 4.5

NS 1.5/6 6

NS 2/3

1000 2000 400 4.5 2

3

NS 2/6 6

NS 2/9 9

NS 2/12 12

NS 2.5/7.5

1000 2000 400 4.5 2.5

7.5

NS 2.5/12 12

NS 2.5/15 15

NS 2.5/18 18

Example:

NS 2/3: Nano silica 2% of cement weight / 3 min sonication

NS 2.5/15: Nano silica 2.5% of cement weight / 15 min sonication

Figure ‎3.12: Schematic diagram showing differences between mixing sequences

44

B. CNT dispersion

The first stage; 10 Samples are prepared by adding 0.1 gm. of carbon Nanotubes in a

glass beaker to 50 ml of water for each time of sonication in a bath sonicator in case of

indirect sonication. Tables 3.8 and 3.9 show the constituents of CNT preparation

samples

Table ‎3.8: Sonication time of carbon Nano tube dispersion samples for direct

sonication

SAMPLE SONICATION

METHOD

TIME

(min)

CNT0 --- 0

CNT2D Direct 2

CNT3D Direct 3

CNT6D Direct 6

CNT9D Direct 9

Table ‎3.9: Sonication time of carbon Nano tube dispersion samples for indirect

sonication

SAMPLE SONICATION

METHOD

TIME

(min)

CNT0 --- 0

CNT3I Indirect 3

CNT6I Indirect 6

CNT9I Indirect 9

CNT12I Indirect 12

CNT18I Indirect 18

Example:

CNT6D: carbon Nanotubes/6 min sonication/direct sonication

CNT3I: carbon Nanotubes/3 min sonication/indirect sonication

In order to improve the CNT dipersion, superplasticizer is added to mixes. 3 samples of

cement pastes are to be conducted in order to study this effect. Materials percentages

used in order to perform the mentioned investigation; carbon Nanotubes 0.02%, Nano

silica 1%, and superplasticizer 0.4% of the cement weight. Time and method of

45

sonication depends on the optimum obtained from stage 1. The constituents of the

mixtures are presented in table 3.10. Figure 3.13 shows the mixing sequence of the

samples.

Table ‎3.10: Mixtures composition (gm.) for 3 cubes 5*5*5 cm3

MIX CEMENT WATER SP N.S. CNT W/C

C/CNT 523 300 0 0 0.1 0.6

C/CNT/SP 523 300

2.3 0 0.1 0.6

C/CNT/NS 523 300

0 5.23 0.1 0.6

Where:

C: “cement”, S.P.: “super plasticizer", N.S.: "Nano silica", CNT: "carbon Nanotubes",

W/C: “water/cement ratio”.

Figure ‎3.13: Schematic diagram showing mixing sequence of mixes in order to

examine the effect of superplasticizer on CNT dispersion

46

The second stage discusses the dispersion of optimum mixing sequence of carbon

Nanotubes within cement matrix. Eight methods are used to examine the compressive

strength for cement pastes after 7 days; water curing. Superplasticizer is added to

carbon Nanotubes during sonication as it helps carbon Nanotubes particles to disperse

well. CNT % is 0.02% by cement weight and water/cement ratio is 0.4. Indirect

sonication method is used. Table 3.11 shows the constituents of the 6 mixtures. Figure

3.14 shows the mixing sequence of the samples.

A comparison between two types of CNT imported and locally produced is conducted

in order to choose the optimum type to complete the experimental plan in phase 2.

Compressive strength after 7 and 28 days test is investigated as well as particle size

distribution to determine the size of CNT particles, its span and diameter.

Table ‎3.11: Second stage mixtures composition (gm.)

MIX CEMENT WATER SP CNT

SONICATION/

HOMOGENIZER

TIME

C/SP 523 210

2.3 0.1

---

C/CNT/SP 523 210

2.3 0.1

---

S60 523 210

2.3 0.1 60 min CNT

sonication

H60 523 210

2.3 0.1 60 min CNT

homogenizer

S40H10 523 210

2.3 0.1

40 min sonication

then 10 min

homogenizer

H10S40 523 210

2.3 0.1

10 min

homogenizer then

40 min sonication

H40S10 523 210

2.3 0.1

40 min

homogenizer then

10 min sonication

S30H30 523 210

2.3 0.1

30 min sonication

then 30 min

homogenizer

Where:

C: “cement”, S.P.: "super plasticizer", CNT: "carbon Nanotubes", W/C:

“water/cement ratio”, H: “homogenizer”, S: “sonication”.

47

Figure ‎3.14: Schematic diagram showing differences between mixing sequences

48

3.2.3.2. Samples for studying the coupled effect of NS and CNT on cement mortars

behavior (phase two)

The first stage, 3 samples are conducted to study the effect of CNT only on cement motars.

the used CNT percentages was 0.01%, 0.02% and 0.03%. Indirect sonication method was

chosen. Compressive and flexural strengths were evaluated after 7 and 28 days of water

curing. Time and method of sonication depends on the optimum obtained from phase 1.

Figure 3.15 shows Schematic the mixing sequence of mortars contain CNT only. Table 3.12

shows the mixes constituents in (gm.) for 3 cubes 5*5*5 cm3.

Table ‎3.12 : Phase two / stage one mixes constituents in (gm.)

SAMPLE CEMENT SAND WATER S.P. N.S.% CNT%

CNT0 1000 2000 400

3.5 0 0

CNT0.01 1000 2000 400 3.5

0 0.01

CNT0.02 1000 2000 400 3.5

0 0.02

CNT0.03 1000 2000 400 3.5

0 0.03

Where:

CNT0.01: carbon Nanotubes/0.01% by cement weight

Figure ‎3.15: Schematic diagram showing the mixing sequence of samples contain CNT

only

49

The second stage; the objective of this phase is to choose the optimum percentage of Nano

silica and carbon Nanotubes on the compressive strength, and flexure strength of mortars. The

optimum time and method of sonication for cement, Nano silica and carbon Nanotubes of

Nano silica as well as the most desirable SP percentage are used in preparing the following

specimens. Mortar cubes of 50 mm*50 mm*50mm are casted for compressive strength test;

also prisms for flexure strength test. The specimens are de-molded after 24 hours and cured in

normal pure water at room temperature until the day of testing. The chosen contents of Nano

silica are (0%, 0.5%, 1%, 1.5%, 2%, and 2.5%) by cement weight and that of carbon

Nanotubes are (0%, 0.01%, 0.02%, and 0.03%) by cement weight. Time and method of

sonication depends on the optimum obtained from phase 1. The constituents of the mixture

are shown in table 3.13. Figure 3.16 shows the mixing sequence of samples contain N.S. and

CNT

Table ‎3.13: Phase two / stage two mixes constituents in (gm.)

SAMPLE CEMENT SAND WATER S.P. N.S.% CNT%

NS0 / CNT0 1000 2000 400 3.5 0 0

NS0.5 / CNT0.01 1000 2000 400 3.5 0.5 0.01

NS1 / CNT0.01 1000 2000 400 3.5 1 0.01

NS1.5 / CNT0.01 1000 2000 400 3.5 1.5 0.01

NS2 / CNT0.01 1000 2000 400 3.5 2 0.01

NS2.5 / CNT0.01 1000 2000 400 3.5 2.5 0.01

NS0.5 / CNT0.02 1000 2000 400 3.5 0.5 0.02

NS1 / CNT0.02 1000 2000 400 3.5 1 0.02

NS1.5 / CNT0.02 1000 2000 400 3.5 1.5 0.02

NS2 / CNT0.02 1000 2000 400 3.5 2 0.02

NS2.5 / CNT0.02 1000 2000 400 3.5 2.5 0.02

NS0.5 / CNT0.03 1000 2000 400 3.5 0.5 0.03

51

NS1 / CNT0.03 1000 2000 400 3.5 1 0.03

NS1.5 / CNT0.03 1000 2000 400 3.5 1.5 0.03

NS2 / CNT0.03 1000 2000 400 3.5 2 0.03

NS2.5 / CNT0.03 1000 2000 400 3.5 2.5 0.03

Figure ‎3.16: Schematic diagram showing the mixing sequence of samples contain N.S.

and CNT

3.2.4. Characterization, Testing and Analysis

In order to evaluate, analyze the results, a number of characterization techniques are to be

used.

3.2.4.1. Characterization

A. Particle Size Distribution

Particle size distribution is an effective method to optimize the optimum dispersion of Nano

particles in water. Mastersizer 3000 (shown in figure 3.17) is used to predict the particles size

is Laser light scattering. Data acquisition rate is 10 KHz. Its typical measurement time is less

than 10 seconds. Particle size varies from 0.01 to 3500 um. Appendix A and B show a sample

of results sheets for NS and CNT respectively.

51

Figure ‎3.17: Particle size analyzer Mastersizer 3000 used for samples dispersion

B. Transmission Electron Microscope (TEM)

Transmission electron microscopy (TEM) is a microscopic technique in which a beam

of electrons is transmitted through an ultra-thin specimen which interacts with the specimen

when it passes through. An image is formed from the interaction of the electrons transmitted

through the specimen. The image is enlarged and focused onto an imaging device, such as

a fluorescent screen located on a layer of photographic film, or being detected by a sensor

such as a CCD camera (78).

The evaluation of the Nano silica and carbon Nanotube production process is based on

determining the particle size distribution of the samples by transmission electron microscope

type JEM-1230 from JEOL CO, Japan, with energy from 40 up to 120KV on steps, line

Resolution of 0.3nm, and maximum magnification of 600Kx, shown in figure 3.18. The TEM

can yield information such as Nano particles size, distribution and morphology. The produced

images can be used to judge whether good dispersion or agglomeration has been achieved in

the sample.

Sample preparation for TEM analysis was done by taking one drop of the prepared solution

after being diluted in water, and then put onto a carbon film on a 3 mm grid of copper. Image

analysis on the Nano particles is carried out on various TEM images. The transformation of

the image files is performed using image analysis software Revolution v 1.60.

https://en.wikipedia.org/wiki/Microscope

https://en.wikipedia.org/wiki/Electron

https://en.wikipedia.org/wiki/Focus_(optics)

https://en.wikipedia.org/wiki/Fluorescent

https://en.wikipedia.org/wiki/Photographic_film

https://en.wikipedia.org/wiki/CCD_camera

52

Figure ‎3.18: The transmission electron microscope (TEM) used for samples

characterization

C. Zeta-Sizer 2000

Zeta potential is a property related to the electrical potential around a particle on the slip

surface within a double layer formed in the fixed layer of fluid attached to the dispersed

particle (79). The liquid layer surrounding the particle is constituted of two sections: the stern

layer where the ions are strongly bounded to the particle and the outer or dispersive layer

where they are less strongly attached. Zeta potential is an indicator of the stability of a

colloidal system. If the suspension has a large negative or positive zeta potential, particles will

repel each other and there will be no attraction between the particles to agglomerate.

However, if the particles have low zeta potential values there will be attraction between the

particles. The magnitude of the zeta potential is predictive of the colloidal stability. Nano

particles with Zeta Potential values more than +25 mV or less than -25 mV will have high

degrees of stability. Dispersions with a low zeta potential value will eventually aggregate due

to Van Der Waal inter particle forces attractions.

After optimizing the Nano silica or carbon Nano tube production process parameters, a

sample is prepared based on the suggested optimum conditions. Zeta potential is measured to

the sample by electrophoresis apparatus Malvern Instruments Zeta-sizer 2000 shown in figure

3.19, and the data reported corresponding to an average of three measurements. The sonicated

53

sample used in zeta potential test was previously mingled with filtered water and then injected

into an electrophoresis cell.

Figure ‎3.19: Zeta-Sizer 2000

D. Scanning Electron Microscope (SEM)

Scanning electron microscope (SEM) is used to is used to determine the Nano particles size

and distribution, characterize the concrete mixtures, and help interpreting the compressive

strength results of the samples after 28 days of curing in water. QUANTA FEG250 shown in

figure 3.20 was used to detect the images. The secondary electron images are to be obtained

in samples coated with Au and using a voltage of 20 kV.

Figure ‎3.20: QUANTA scanning electron microscope used for analysis

54

E. X-ray diffraction XRD

X-ray diffraction (XRD) is one of the best methods for detecting changes in hydration

reaction due to the addition of pozzolanic materials. A mineralogical study is conducted

employing the X-ray diffraction technique (XRD) to identify the formed phases before

and‎after‎exposure‎to‎600˚C.‎After‎performing‎the‎compressive‎strength‎test,‎the‎crushed‎

concrete cubes of each mix are finely ground and totally mixed. A representative sample

from each mix is undertaken and ground to a very fine powder that passes (75 lm) sieve

and is tested immediately after that.

F. Thermo-gravimetric analysis TGA

The TGA test is widely used for determining the effect of high temperature on hydrated

cement composites. Thermo-gravimetric analysis (TGA) is carried out in mortar or paste

mixes cured in water for 28 days. A TGA850 thermo balance from Mettler Toledo and

STARe software v8.10 was used. The samples are previously milled, washed with

acetone, filtered and then dried at 60 ± 2oC for approximately 30 min. Aluminum

crucibles of 100 mL are used and filled with 30 ± 1 mg of dried sample. Samples are

heated up to 600oC with a heating rate of 10

oC / min in a nitrogen atmosphere.

3.2.4.2. Testing

A. The Compressive Strength Test

The compressive strength test of the concrete samples is determined at 7, and 28 days of

moisture curing as per ASTM C39. The test is carried out using a universal testing machine

SHIMADZU 1000 KN shown in figure 3.21. Table 3.14 shows data entry on the testing

machine. Figure 3.22 shows data on the machine's screen.

Table ‎3.14: Data entry on the testing machine for the compressive strength test

RATE 0.25 N/mm2/sec.

SPECIMEN DIMENSIONS 50*50 mm2

FORCE RANGE (KN) 0 ~ 150

55

Figure ‎3.21: Universal testing machine 1000 KN

Figure ‎3.22: Data on the machine's screen

B. The flexure Strength Test

Flexural strength is a mechanical property for‎brittle‎material,‎defined‎as‎a‎material’s‎ability‎to‎

resist deformation under load. When an object formed of a single material is bent, it

experiences a range of stresses across its depth at the extreme fibers. Most materials, before

they fail under compressive stress, fail under tensile stress, so the flexural strength is the

maximum tensile stress value that can be reached before the beam fails(54). The test is

56

determined at 28 days of water curing as per ASTM C78. The test is carried out using a

universal testing machine SHIMADZU 1000 KN shown in figure 3.21. Table 3.15 shows data

entry on the testing machine. Figure 3.23 shows the flexure test using three points beam

method.

Table ‎3.15: Data entry on the testing machine for the flexure strength test

Figure ‎3.23: Flexure test using three points beam method

3.2.4.3. Analysis

Statistical experimental design is a more scientific and efficient approach for establishing an

optimized mixture for a given constraint, while minimizing the number of experimental data

points. the effects of studied parameters will be characterized and analyzed using ANOVA

and regression models, which can identify the primary factors and their interactions on the

measured properties. JMP SAS12 program is used to predict the full factorial and response

surface statistical models.

RATE 0.05 N/mm2/sec.

SPECIMEN DIMENSIONS 50*200 mm2

FORCE RANGE (KN) 0 ~ 10

57

Chapter 4 : Results and Discussion

4.1. Introduction

This chapter represents the outcome of the conducted experimental plan. the results will

be discussed and analyzed in order to find out the following:

Optimum dispersion method and time of Nano silica particles using the

proposed technique by applying either direct or indirect sonication energy.

Optimum dispersion method and time of carbon Nanotubes particles through

introducing a novel innovative technique that make use of both; chemical

properties of superplastecizer, and cavitational properties of sonicators ( Direct

and indirect) as well as homogenizer.

The coupled effect of well dispersed NS and CNT on the mechanical properties

of cement composites with different dosages.

Statistical and micro-structural analysis will be introduced in order to identify

the primary factors and their interactions on the measured properties. The

effects of studied parameters will be characterized and analyzed using the full

factorial and response surface statistical models.

4.2. Optimizing the dispersion of Nano silica and carbon

Nanotube (phase 1)

In this phase the effect of sonication methods and time were studied for the effective

dispersion of NS and CNT. The results were introduced using particle size distribution,

specific surface area, compressive and flexure strengths, SEM, TEM, TGA, XRD and

ANOVA statistical analysis.

4.2.1. Optimizing the type and time of sonication on the dispersion of

Nano silica

This step presented the effect of changing sonication time and method for the

dispersion of NS in the cement matrix. The results were introduced using particle size

distribution, specific surface area, compressive and flexure strengths, SEM, TEM, TGA

and XRD.

58

4.2.1.1. The effect of sonication type on the dispersion of NS (stage 1)

This stage presented the effect of changing sonication method either direct or indirect

for the dispersion of NS in the cement matrix. The results were introduced using

particle size distribution and specific surface area.

From the following figures (4.1-4.4);

The sonication time increased the sub-nanometric particle content to reach an

optimum value of 90% at 1 min and 3 min for direct sonication and indirect

sonication respectively instead of 70% for as received sample. While increasing

the indirect sonication time to 9 min decreased the sub-nanometric particle

content to 58%.

The optimum time of sonication for the direct and indirect sonication methods

were found to be 1 minute and 3 minutes respectively.

Increasing sonication time for both methods caused re-agglomeration for NS

particles.

The optimum specific surface area for direct sonication increased by 17% as

compared to as received sample.

Although The optimum specific surface area of the direct sonication method

was higher than that of the indirect method, as shown in figures (4.5-4.6). the

indirect sonication method was chosen as the optimum method for the reason

that the slight increase in the direct sonication time (from 1min to 3 min),

significantly affected the dispersion of the ns particles, while for the indirect

sonication the slight increase in time (from 3min to 6 min), showed less effect

on the NS dispersion as it can be noticed from the specific surface area results.

59

Figure ‎4.1: Particle size distribution of Nano silica particles size using direct sonication method

Figure ‎4.2 : Cumulative density of Nano silica particles size using direct sonication method

61

Figure ‎4.3: Particle size distribution of Nano silica particles size using indirect sonication method

Figure ‎4.4: Cumulative density of Nano silica particles size using indirect sonication method

61

Figure ‎4.5: Specific surface area for Nano silica particles using direct sonication

method

Figure ‎4.6: Specific surface area for Nano silica particles using indirect sonication

method

4.2.1.2. The effect of sonication time on the dispersion of NS (stage 2)

This stage presented the effect of changing sonication time for different dosages of NS

in the cement matrix. The results were introduced using compressive and flexure

strengths, SEM, TEM, TGA and XRD.

62

A. Compressive strength

Figures (4.7-4.10) showed the early and late age compressive strength for 1% and 2%

NS by cement weight sonicated for different times, the results were evaluated that :

For 1% NS, increasing sonication time increased both; the early and late

compressive strengths of the cement mortars as compared to the control mix.

Increasing the sonication time over 3 mins, decreased the early compressive

strength significantly to reach 266 kg/cm2 at 12 min instead of 394 kg/cm2 at 3

min. this can be attributed reduction in electrostatic forces, which promoted the

particle agglomeration with increasing sonication time and reduced dispersion.

Increasing sonication time for higher dosages of NS (2%) helped its particles to

disperse well, and consequently the early compressive strength increased for all

mixes as compared to the control mix, this can be attributed to the fact that

increasing NS dosage needed more sonication time to reach a well dispersed

condition.

The optimum specific surface area for 1% NS sonicated for 3 minutes was

approximately the same value of that of 2% NS sonicated for 12 minutes, which

confirm that increasing sonication time is required for higher dosages of NS for

an effective dispersion, shown in figures (4.15-4.16).

The optimum sonication time for 1% NS was 3 minutes which got a gain in 7

and 28 days compressive strength 84% and 37% respectively.

The cement mortar contains NS sonicated for 3 min gained most of its

compressive strength at the early age, as it reached 92% of its strength after 7

days of curing due to the observed increase in the sub nano metric particles after

3min of sonication.

The agglomerated particles of NS dispersed well in the latter ages, this was

observed from the difference of compressive strength for samples contained 1%

NS sonicated for more than 3 minutes and the optimum sample in the early and

late ages.

Particle size distribution showed in figures (4.11-4.14) confirmed the behavior of the

compressive strength;

Sub-nanometric content increased to reach an optimum value at 3 min

sonication as compared to control for 1%.

Specific surface area, shown in figures (4.15-4.16), for the optimum sonication

time for 1% NS is approximately the same value of the optimum time (12 min)

for 2% NS.

Specific surface area is the dominant factor to determine the optimum

dispersion for NS.

63

Figure ‎4.7: 7 days compressive strength for cement mortars containing 1% NS

under the effect of sonication for 3, 6, 9 and 12 minutes



64





65

Figure ‎4.11: Particle size distribution of 1% NS particles size dispersed in water under the effect of sonication for 0, 3,

6, 9 and 12 minutes

Figure ‎4.12: Cumulative density of 1% NS particles size dispersed in water under the effect of sonication for 0, 3, 6, 9

and 12 minutes

66

Figure ‎4.13: Particle size distribution of 2% NS particles size dispersed in water under the effect of sonication for 0, 3,

6, 9 and 12 minutes

Figure ‎4.14: Cumulative density of 2% NS particles size dispersed in water under the effect of sonication for 0, 3, 6, 9

and 12 minutes

67


sonication for 0, 3, 6, 9 and 12 minutes


sonication for 0, 3, 6, 9 and 12 minutes

68

Figures (4.17, 4.19 and 4.21) showed the early compressive strength for different NS

dosages sonicated for the same time 3, 6 and 12 minutes which concluded that:

Increasing NS dosage need more time of sonication and increasing sonication

time for the same dosage caused reduction in compressive strength. This was

attributed to re-agglomeration of NS particles and electrostatic repulsion

between particles.

The optimum dosages of NS for the sonication times 3, 6 and 12 minutes were

1%, 1.5% and 2.5% by cement weight.

The same behavior showed in the latter ages of compressive strength showed in

figures (4.18, 4.20 and 4.22).

Figure ‎4.17: 7 and 28 days compressive strength for cement mortars containing

0.5, 1, 1.5 and 2% NS under the effect of sonication for 3 minutes

69

Figure ‎4.18: 7 and 28 days compressive strength for cement mortars containing 1,

1.5 and 2% NS under the effect of sonication for 6 minutes

Figure ‎4.19: 7 and 28 days compressive strength for cement mortars containing 1,

2 and 2.5% NS under the effect of sonication for 12 minutes

71

Figures (4.23-4.24) showed the optimum dosages of NS and their optimum time of

sonication;

All dosages got approximately the same compressive strength with average gain

37.5% in 28 days compressive strength.

The optimum sonication time for 0.5%, 1%, 1.5%, 2% and 2.5% NS was found

to be 3, 3, 6, 12 and 12 minutes respectively.

Results displayed in figures (4.25-4.27), revealed that :

No matter the percentage used of ns and no matter the sonication time, the final

dispersion condition of ns particles within the cement matrix represented by the

specific surface area and the particle size distribution is the dominant factor in

determining the compressive strength.

Changing sonication time had the same effect on the different dosages of NS.

The optimum NS concentration by consequence time of sonication was 2.5% by

cement weight sonicated for 12 minutes using indirect sonication method. Gain

in compressive strength was 97% and 40% for 7 and 28 days respectively as

compared to the reference mortar.

Figure ‎4.20: 28 days compressive strength for optimum NS sonication time for

each concentration

71

Figure ‎4.21: Particle size distribution of optimum NS sonication time for each concentration

Figure ‎4.22: Cumulative density of optimum NS sonication time for each concentration

72

Figure ‎4.23: Specific surface area for optimum NS sonication time for each

concentration

B. Flexure Strength

Figures (4.27-4.28) showed that:

The flexure strength of cement mortars containing 1% and 2% NS of cement

weight, the optimum time of sonication for 1% NS was 3 minutes.

The sample contained 1% NS sonicated for 3 minutes (NS 1/3) got a gain 67%

in flexure strength.

The sample contained 2% NS sonicated for 3 minutes (NS 2/3) increased the

flexure strength for 100%.

The highest flexure strength was reached using 0.5 wt.% NS sonicated for 1.5

minutes or 2 wt.% NS sonicated for 3 minutes. The gain in flexure strength was

100% as compared to the reference beam.

73


minutes compared by the control batch


minutes compared by the control batch

74

Figues (4.26-4.37) noted that :

The agglomeration of NS increased the flexure strength, however well dispersed

NS decreased the amount of ettringite needles in the matrix.

Figure ‎4.26: Comparison between compressive and flexure strength for beams

with 1% NS sonicated for 3, 6, 9 and 12 minutes compared by the control batch


with 2% NS sonicated for 3, 6, 9 and 12 minutes compared by the control batch

75

Figures (4.28-4.30) showed the relation between the effect of NS on the compressive

and flexure strengths, they concluded that:

The flexure strength trend was opposed proportional with compressive strength

due to the reaction of NS in early ages so ettringite needles had the opportunity

to increase the flexure strength at the latter age.


with different percentages of NS sonicated for 3 minutes

76





77

C. Microstructure Analysis

SEM micrographs of the optimum cement mortar contained 2.5% NS sonicated

for 12 minutes as compared to plain cement mortar were showed in figure 4.35.

The Scanning Electron Microscope (SEM) images were taken to study the

micro-structure for the materials.

As for the SEM plates, the morphology structure in control samples, when

compared with nano silica system, is in agreement with the poor properties in

the fresh state and with the compressive results.

calcium silicate hydrate plates as well as Aft needles and calcium hydroxide

crystals were clearly identifiable in the control specimen as well as the porous

structure of paste as it can be seen in part (a). While for nano silica specimen

seen in part (b), the calcium silicate hydrate plates were clearly dominating with

a well compacted structure, as a conclusion nano silica presence contributed to

producing higher levels of calcium silicate hydrate, as the nano silica’s high

reactivity acted as a nucleating point to bind the hydration products together On

the other side; this phenomenon may explain the high strength of specimens

containing nano silica.

Nano-SiO2 can absorb the Ca (OH) 2 crystals, and reduce the size and amount

of the Ca (OH) 2 crystals, thus making the interfacial transition zone (ITZ) of

aggregates and binding paste matrix denser. The nano-SiO2 particles can fill the

voids of the C–S–H gel structure and act as nucleus to tightly bond with C–S–H

gel particles, making binding paste matrix denser, and long-term mechanical

properties and durability of concrete are expected to be increased.

78

Figure ‎4.31: SEM micrograph of the plain cement composite (a) as compared to

optimum cement mortar contained 2.5 wt.% NS sonicated for 12 minutes (b)

a

b

79

XRD results were presented in figures (4.32 and 4.33). XRD was performed to

detect changes in the hydration products due to the presence of nano silica. Due

to their crystalline nature, calcium hydroxide, calcium silicate and silica peaks

can clearly be detected in the XRD diagrams, while amorphous materials such

as calcium silicate hydrate cannot be directly detected using this technique.

Nano silica addition resulted in a significant decrease in the calcium hydroxide

peaks compared to control specimens. As it can be confirmed from the semi

quantitative analysis where the CH content decreased from 4 % for the CO Mix

to reach 1 %, in the sample contained 2.5% NS sonicated for 12 minutes and 2

%. While some peaks disappeared due to the high pozzolanic reactivity of nano

silica that produced higher amounts of calcium silicate hydrate, which in turn,

explains the high strength results for these specimens.

Figure ‎4.32: XRD the plain cement composite

81


(NS2.5/12)

Thermal analysis techniques such as thermogravimetric analysis (TGA) has

been used successfully to determine the changes in hydration products for

cement pastes after exposure to high temperatures vs. time. A number of studies

have shown that an increase in temperature in cement pastes causes the release

of physically absorbed water, chemically bonded water and the decomposition

of hydration products. Figures (4.34 and 4.35) showed TGA micrographs of

plain cement composite as compared to the mix containing 2.5% nano silica.

Through the DSC curves, three major endothermic peaks can be detected. The

first peak is between 80 C and 150 C, which resulted from the loss of the

physically absorbed water from the pastes. The second peak, between 400 C and

500 C corresponded to the de-hydroxylation of calcium hydroxide and the loss

of some of chemically bonded water from calcium silicate hydrate. The third

peak, between 700 C and 800 C, corresponded to the complete dehydration of

calcium hydroxide, which is also supported by the XRD results, and the

dehydration of calcium silicate hydrate. Moreover, the DSC curves show that

the specimens with nano silica showed more stable behavior during the

temperature increase compared to the control specimens. This phenomenon is

81

most likely due to the high amount of high-density calcium silicate hydrate in

these specimens that was not affected by high temperature exposure.

The same figures show the results of thermogravimetric analysis, which

represents the change in mass for the specimens before and after exposure to

high temperatures from 30 C to 900 C. Three main mass losses were observed at

150 C, 450 C and 750 C in the specimens. The specimens showed a dramatic

increase in mass loss starting at approximately 650 C. This result can be

accounted as a confliction point for the disintegration of the hydration products,

which explains the radical decrease in strength for specimens exposed to higher

temperature.

The loss in weight observed for the control Mix from 30 to 400 (13%) was

much higher than the mix containing nano silica (2%), this can be attributed to

the larger amount of CH in the control mix as compared to the mixes containing

nano silica. This is in good agreement with the compressive strength results.

82

Figure ‎4.34: TGA of the plain cement composite

Figure ‎4.35: TGA the cement mortar containing 2.5% NS sonicated for 12 min

(NS2.5/12)

83


CNT

The following part aims to reach an optimum dispersion level of CNT through the

introduction of different techniques including sonicators and homogenizers. The

dispersion level was evaluated through; particle size distribution, specific surface area,

cements pastes compressive strength, SEM, TEM and ANOVA statistical analysis. In

addition a comparison occurred between the properties of two types of CNT, imported

and locally produced.

4.2.2.1. The effect of sonication type on the dispersion of CNT (stage 1)

In this stage the effect of sonication type either; direct or indirect on the dispersion of

CNT was investigated through PSD and their specific surface area.

Particle size distribution represented in figures (4.36and 4.37) showed the following:

The application of either the direct or the indirect sonication methods enhanced

the dispersion of the CNT particles significantly.

No matter the time of application was, the dispersion of the CNT particles was

affected significantly by applying either of the sonication types.

As for the direct sonication; increasing the time of application increased the

dispersion level. the agglomerates size (D50) decreased significantly to reach

less than 25 micrometers after 3 min of application instead of the 100

micrometers of the as received CNT.

While for the indirect sonication; increasing the time of application increased

the dispersion level. the agglomerates size (D50) decreased significantly to

reach less than 20 micrometers after 6 min of application instead of the 100

micrometers of the as received CNT.

Increasing direct sonication time over 3 min caused re-agglomeration for CNT

particles. the agglomerates size (D50) increased to reach about 30 micrometers

after 9 min of application instead of the 25 micrometers reached after 3 min.

Increasing indirect sonication time over 6 min caused re-agglomeration for CNT

particles. the agglomerates size (D50) increased to reach about 25 micrometers

after 9 min of application instead of 20 micrometers after 6 min.

The optimum sonication time using direct and indirect sonication for CNT

dispersion was found to be 3 and 6 minutes respectively.

For 3 minutes sonication in both methods, the agglomerates size (DV50)

reached 25 um

84

The optimum method of dispersion was found to be the indirect method.

Specific surface area for both methods showed in figures (4.38and 4.39) concluded that

the optimum sonication method was the indirect sonication.

For direct method, the specific surface area increased till 3 minutes then

decreased for more than 3 minutes.

For indirect method, the specific surface area increased till 6 minutes

then decreased for more than 6 minutes.

The specific surface area for 6 minutes indirect sonication increased by

10% as compared to 3 minutes direct sonication.

85

Figure ‎4.36: Cumulative density of CNT using direct method

Figure ‎4.37: Cumulative density of CNT using indirect method

86

Figure ‎4.38: Specific surface area for CNT particles dispersed in water using

direct sonication method

Figure ‎4.39: Specific surface area for CNT particles dispersed in water using

indirect sonication method

87

Table (4.1) and figure (4.40) presented the effect of superplasticizer and Nano silica on

the dispersion of CNT within the cement paste, the results showed the following:

The use of CNT as received resulted loss in compressive strength (-15%) as

compared to plain cement paste.

The addition of superplasticizer to the CNT before being mixed with cement

increased the early age compressive strength of cement pastes by 40% as

compared to the one contained CNT only. this can be attributed to the

electrosteric-static behavior of the superplastecizer that increased the repulsion

between the CNT particles and consequently enhanced their dispersion.

Superplasticizer enhanced significantly the dispersion of CNT.

The addition of NS increased the compressive strength of the cement paste by

9% as compared to the one contained CNT only. This percentage was due to the

reaction of NS into the matrix however it didn't affect the dispersion of CNT

Table ‎4.1: 7 days compressive strength studying the effect of NS and

superplasticizer on CNT dispersion

% gain in compressive

strength

7 days compressive

strength (Kg/cm2) Sample

0 227 C/CNT

40 317 C/CNT/SP

9 248 C/CNT/NS

88

Figure ‎4.40: 7 days compressive strength of cement pastes studying the effect of

NS and superplasticizer on CNT dispersion

4.2.2.2. Introduce a novel technique for the dispersion of CNT (stage 2)

This stage presented a novel dispersion method for de-agglomeration of CNT particles.

The dispersion level was determined through evaluating the CNT particle size

distribution, specific surface area, and cement pastes compressive strength results. in

addition micro-structural will be introduced in order to expand our knowledge about the

used techniques and their effect on the dispersion level.

A. compressive Strength

Figures (4.41-4.43) showed the early age compressive strength of different CNT de-

agglomeration methods and their gain as compared to the control batches. The

following points were observed;

The application of either sonicator or homogenizer enhanced the dispersion of

CNT particles.

All methods increased the compressive strength of the cement paste as

compared to sample containing SP.

The method S30H30 (30 min sonication then 30 min homogenizer) got a loss in

the compressive strength as compared to the sample containing SP and CNT.

The optimum treatment method of CNT (S40H10, 40 minutes sonication then

10 minutes homogenizer).

89

The optimum method obtained a gain 18% in compressive strength as compared

to cement paste contained carbon Nanotube and superplasticizer (C/CNT/SP)

and 38% as compared to cement paste contained superplasticizer only (C/SP).

For the mix H60 (60 minutes homogenizer), the homogenizer increased the

compressive strength by 35% as compared to the mix containing SP. This can

be attributed to the homogenizer effect in decreasing the agglomerates but at the

same time it influenced the particle size distribution changing it to a narrower

distribution(16; 80), as it breaks the CNT particles into equal sizes which is not

recommended to act as bridges for different sizes of cracks into the matrix.

Gain in compressive strength as compared to C/CN/SP refers to the effect of

method of dispersion.

Particle size distribution shown in figures (4.44 and 4.45) noted that :

20% of particles in the size of nanometer varies between 0.01 to 0.1 um,

however 20% of particles for the as received sampled in the range of sizes 100

to 1000 um.

Figures (4.46and4.47), shows a 3D curve and its projection relating the sonicator

application times and the homogenizer times with the resultant compressive strength of

cement composites, while figure 4.48 shows the dispersion status of the carbon nano

tubes before and after applying the optimum dispersion technique. The figures reveal

that the proposed technique is highly effective not only in dispersing the CNT particles

but also in keeping it well dispersed for longer times.

Figure ‎4.41: Effect of different methods of CNT treatment on cement pastes 7 days

compressive strength

91

Figure ‎4.42: Gain in 7 days compressive strength for cement pastes studying

different methods for CNT treatment as compared to cement paste containing

superplasticizer and CNT

Figure ‎4.43: Gain in 7 days compressive strength for cement pastes studying

different methods for CNT treatment as compared to cement paste containing

superplasticizer only.

91

Figure ‎4.44: Particle size distribution of as received and optimum method for CNT treatment

Figure ‎4.45: Cumulative density of as received and optimum method for CNT treatment

92

Figure ‎4.46: 3D graph between time of sonication and homogenizer and

compressive strength

Figure 4.47: Contour graph presents the relation between time of sonication and

homogenizer and compressive strength

93

Figure ‎4.48: CNT immediately before and after treatment (a), after a week (b),

after a month (c)

B. Microstructure Analysis

SEM micrographs showed that:

The plain cement composite which contained a lot of voids as compared to

sample contained treated CNT which had lower voids and well dispersed carbon

Nanotubes, shown in figures (4.49).

TEM shown in figures (4.50) indicates a better dispersion performance for the CNT

sample after treatment using S40H10 method as compared to the as received sample.

a

a b c

94

Figure ‎4.49: SEM micrograph of the plain cement paste (a) as compared to

optimum CNT treatment method (S40H10) cement paste (b)

b

a

95

Figure ‎4.50: TEM micrograph of the as received CNT (a) as compared to

optimum CNT treatment method (S40H10) (b)

C. Comparison between local and imported CNT subjected to the optimum

dispersion method

A comparison was held between the Two types of CNT (imported and locally

produced) in order to investigate the differences between their properties on the

mechanical strength of cement mortars as shown in table (). Locally produced was

chosen in the second phase due to its low cost, high strength in the early and late ages

and large span of particles size.

Table ‎4.2: Comparison between imported and locally produced CNT properties

28 days

compressive

strength

(kg/cm2)

7 days

compressive

strength

(kg/cm2)

Span

(um)

Diameter

(nm) Type

351 246 0.64 39 CNT imported

419 300 1.5 23 CNT local

b

96

4.3. Optimizing the couple effect of Nano silica and carbon

Nanotube on the mechanical properties of cement

composites (phase 2)

In this phase the coupled effect of NS and CNT on the mechanical properties of cement

mortars was thoroughly investigated. dispersion level was determined through

evaluating particle size distribution, specific surface area, compressive and flexure

strengths, SEM, TEM, TGA, XRD and ANOVA statistical analysis.

4.3.1. Optimizing the effect of different dosages of CNT on the

mechanical properties of cement mortars (stage 1)

In this phase the effect of different dosages of CNT on the mechanical properties of

cement mortars was investigated. The dispersion level was determined through

evaluating compressive and flexure strengths, SEM, TEM, TGA and XRD.

A. Compressive Strength

Compressive strength results after 7 and 28 days was showed in figures (4.51-4.52),

they concluded that :

Difference between compressive strength values for 0.01% and 0.02% at the

early and late age was 8 % and 16% respectively. CNT acts as nucleation spots

in the cement matrix at the early age and bridging late age.

CNT gain most of its strength in the early age, as it acts as nucleation spots in

the matrix. 0.01%, 0.02% and 0.03% CNT gain 71%, 67% and 84% of its

compressive strength at the early age.

The higher amount of CNT (0.03%) increased the compressive strength for both

ages.

Within the studied different amounts of CNT, 0.03% CNT by cement weight is

the optimum percentage as compared to 0.01 and 0.02%.

The gain in compressive strength obtained for 0.03 wt.% CNT was 50% and

23% after 7 and 28 days respectively.

Particle size distribution shown in figures (4.53-4.54) noted that :

The particle size distribution for different dosages of CNT presented

agglomeration for 0.01% and 0.02% CNT more than 0.03% as well as specific

surface area showed in table (4.3).

97

As compared to 0.02% and 0.03% CNT, the specific surface area value, shown

in table (4.3), of 0.01% CNT is very low due to high amount of agglomerates.

The decrease of liquid to powder ratio helped in increasing the sub-nanometric

particles.

The sub-nanometric amount of 0.01% CNT is 0%, however the sub-nanometric

amount for 0.02% and 0.03% CNT is 20% and 40% respectively.

The optimum dispersion method (S40H10) is effective for 0.02% CNT or

higher dosages.

Figure ‎4.51: 7 days compressive strength for CNT mortars compared by the

control batch

98

Figure ‎4.52: 28 days compressive strength for CNT mortars compared by the

control batch

99

Figure ‎4.53: Particle size distribution of CNT dispersed in water in different percentages

Figure ‎4.54: Cumulative density of CNT dispersed in water in different dosages

111

Table ‎4.3 : Specific surface area of different dosages of CNT

Mix Specific surface area (m2/kg)

CNT0.01 235.4

CNT0.02 87330

CNT0.03 124600

B. Flexure Strength

Figures (4.55) showed the flexure strength for different dosages of CNT after 28 days,

they concluded that:

No matter the dosage used of CNT, the flexure strength increased significantly

by the presence of CNT.

The flexure strength increased significantly by 67% for all CNT mixes as

compared to the control beam.

Figure ‎4.55: Flexure strength for beams containing 0.01, 0.02 and 0.03% CNT by

cement weight compared by the control batch

111


Figure (4.56) showed TGA result of the mix containing 0.03% CNT. The loss in

weight observed for the control Mix from 30 to 400 (13%) was much higher

than the mix containing carbon nano tube (5.5%), this can be attributed to the

larger amount of CH in the control mix as compared to the mixes containing

carbon nano tube due to the behavior of the carbon nano tube as a nucleation

sites increasing the C-S-H production and consequently decreasing the CH

content in the mix. This is in good agreement with the compressive strength

results.

Figure ‎4.56: TGA of the cement mortar containing 0.03% CNT (CNT0.03)

112

4.3.2. Optimizing the couple effect of different dosages of NS and CNT

on the mechanical properties of cement mortars (stage 2)

In this stage the coupled effect of NS and CNT on the mechanical properties of cement

mortars will be represented. The results were introduced using particle size distribution,

specific surface area, compressive and flexure strengths, SEM, TEM, TGA, XRD and

ANOVA statistical analysis.

A. Compressive Strength

Compressive strength after 7 and 28 days for different dosages of NS and CNT

illustrated in figures (4.57-4.62) showed the following:

For mixes containing 0.01%, and 0.02% CNT, increasing NS content up to 1%

increased both; the early and late compressive strengths of cement mortars. The

gain in the late compressive strength reached 35% by the addition of 1% NS, as

compared to the control mix (0% NS, 0% CNT).

Increasing NS content higher than 1% decreased significantly the compressive

strength of mixes containing 0.01% (NS1/CNT0.01), and 0.02% CNT

(NS1/CNT0.02). The strength loss reached -22% after 28 days of curing by the

addition of 2.5% NS, as compared to the control mix (0% NS, 0% CNT).

The addition of NS to mixes containing 0.03% CNT decreased the compressive

strength of all mixes. The strength loss reached -16% after 28 days of curing by

the addition of 2.5% NS (NS2.5/CNT0.03), as compared to the control mix (0%

NS, 0% CNT).

The utilization of small amounts of NS (less than 1%) with small amounts of

CNT (less than 0.02%) helped in increasing the compressive strength of cement

mortars at both; the early and late ages, while by utilizing higher dosages of

CNT, significant strength loss has been observed. This can be attributed to the

following points;

a) The interaction of the OH– functional groups from the CNT with the

Ca(OH)2 re-agglomerates the CNT dispersions and the Ca(OH)2,

decreasing the surface area of the nano particles available to work as

nucleation spots at early ages, and decreases the availability of Ca(OH)2

for the NS to react with, to form additional C–S–H at latter ages. The

combination of these two effects decreases the overall strength of the

mixes(11).

b) The combination of NS and a low amount of CNT thought to be affecting

the hydration reaction due to the presence of individual CNT that works as

extra nucleation spots for the hydrates and enhance the activity of the NS.

113

c) The combination of NS and a high amount of CNT thought to be of a

negative effect on the hydration reaction due to the re-agglomeration

process of the CNT, which hinders the activity of the NS and affects

negatively the production of hydrates of the cement.

d) The effect of the re-agglomeration process of the CNT dispersions on the

activity of the NS and the hydration of the cement depends on the

concentration of CNT and the hydration time. A higher amount of CNT

will be more susceptible to re-agglomeration, and as hydration time

progresses the amount of Ca(OH)2 released in the matrix by the cement

will be higher, and the re-agglomeration will be accelerated.

e) The activity of the NS is accelerated, decelerated or completely inhibited

depending on the amounts of CNT and Ca(OH)2 present in the matrix.

The re-agglomeration process of the CNT will decrease the surface area

available for the particles to work as extra nucleation spots and eventually

will hinder the activity of the NS and affect the hydration of cement.

The utilization of high amounts of NS (more than 1%) with either small or high

amounts of CNT decreased the compressive strength of cement mortars at both;

the early and late ages. Adding 2.5% NS with 0.01% CNT (NS2.5/CNT0.01)

decreased the compressive strength by -20% as compared to cement mortar

containing 0.01% CNT only. While adding 2.5% NS with 0.02%

(NS2.5/CNT0.02) or 0.03% CNT (NS2.5/CNT0.03) decreased the compressive

strength for about -45% as compared to cement mortar containing 0.02% and

0.03% CNT respectively. This can be attributed to the previous mentioned

points in addition;

a) NS particles cannot easily disperse within the cement matrix due to their

high surface energy, they become more agglomerated and the voids

appear which affect the compressive strength gain (16).

b) The large agglomerates suck the mix water between its particles making

less water available for the progress of cement hydration.

The optimum compressive strength value was for the sample containing 0.02%

CNT adding to 1% NS (NS1/CNT0.02). The gain in compressive strength

reached 72% and 35% after 7 and 28 days respectively.

114


different percentages of NS



115





116




different dosages of NS

117

Figures (4.63-4.68) showed particle size distribution of low and high amounts of NS

(1% & 2%) combined with 0.02% CNT, the following can be noted :

After applying the optimum dispersion techniques for the 0.02% CNT and 1%

NS the sub-nanometric content (<100 nm) increased to reach 20% and 40%

respectively, while after being mixed, the overall sub-nanometric content

reached 50%, The rest of particles content (50%) ranged in size between 100

nm and 2 um.

After applying the optimum dispersion techniques for the 0.02% CNT and 2%

NS the sub-nanometric content (<100 nm) increased to reach 20% and 30%

respectively, while after being mixed, the overall sub-nanometric content

reached 20%, The rest of particles content (80%) ranged in size between 100

nm and 2 um.

The huge increase in the agglomeration size (20 um) after increasing the NS

dosage from 1% to 2%, was the main reason of why the compressive strength

decreased significantly with larger amounts of NS rather than with small

amounts.

The previous points confirmed that the high amounts of NS combined with

CNT increased the agglomerates amount and size. The large agglomerates

sucked the mix water and acted as large voids in the matrix.

Specific surface are shown in figures () noted that :

The specific surface area results reflected the increase in the agglomeration size

caused by increasing the ns dosage from 1% to 2%, as the overall specific

surface area decreased significantly by the addition of 2% ns to reach about

50% of its value after the addition of 1%.

the overall specific surface area of the mix containing 2% NS with 0.02% CNT

was less than the value of any of its individual components.

The specific surface area value of 1% NS combined with 0.02% CNT was

higher than the specific surface area of either NS or CNT individually.

the specific surface area and the particle size distribution results were in a good

agreement with the compressive strength results.

118


Figure ‎4.64: Cumulative density of samples containing 1% NS and 0.02% CNT

119


Figure ‎4.66: Cumulative density of samples containing 2% NS and 0.02% CNT

111

Figure ‎4.67: Specific surface area for solutions containing 1% NS and 0.02% CNT

Figure ‎4.68: Specific surface area for solutions containing 2% NS and 0.02% CNT

111

B. Flexure Strength

For the flexure strength, mortars which contained CNT and NS together, the results

represented in the figures (4.69-4.71) showed the following:

For mixes containing 0.01%, 0.02% and 0.03% CNT, increasing NS content up

to 1% increased the flexure strength of cement mortars.

The gain in the flexure strength reached about 83% by the addition of 1% NS,

as compared to the control mix (0% NS, 0% CNT).

Increasing NS content higher than 1% caused a significant drop in the flexure

strength of all CNT mixes.

The flexure strength loss reached about -20% after 28 days of curing by the

addition of 2.5% NS, as compared to the mixes containing 0.01%, 0.02% and

0.03% CNT only. This can be attributed to the presence of huge agglomerates of

CNT and NS in the mixes containing high amounts of NS as it was seen from

the particle size distribution and specific surface area results. the large

agglomerates increases the void ratio throughout the matrix, and consequently

decreases the mix strength.

Low amounts of CNT increased the flexure strength in addition with NS as

compared to high amounts. 0.5% NS combined with 0.01%, 0.02%, and 0.03%

CNT increased the flexure strength by 100%, 67% and 33%, as compared to the

control mix (0% NS, 0% CNT).

The optimum flexure strength value was for the sample containing 0.5% NS

sonicated for 3 minutes combined with 0.01% CNT by cement weight. The

optimum gain in flexure strength was found to be 100%.

112


percentages of NS


percentages of NS

113


percentages of NS


From the SEM and TEM micrographs the following can be observed:

Well dispersion of NS and CNT were observed for the combination between 1%

NS and 0.02% CNT, as shown in figures (4.72).

The matrix was observed to be more dense and contained fewer voids as

compared to plain cement matrix.

High agglomerates were observed for the combination between 2% NS and

0.02% CNT., as shown in figures (4.73).

The performance of the nano silica with the CNT during the mixing period as it

can be seen from the TEM figures (4.74) is highly different when a mono

dispersed CNT particle found the nano silica got attached to the nano tube in a

manner that helps the bonding between the nano tubes and the cement matrix,

while when agglomerated the nano silica particles got trapped between the CNT

particles and a huge agglomerated particle found which act as a voided area

within the matrix and consequently the compressive strength decreased.

114

Figure ‎4.72: SEM micrograph of a plain cement composite (a) as compared to

cement mortar combined 1 wt.% NS and 0.02 wt.% CNT (b)

a

b

115

Figure ‎4.73: SEM micrograph of a plain cement composite (a) as compared to

cement mortar combined 2 wt.% NS and 0.02 wt.% CNT (b)

agglomerated

NS and CNT

a

b

116

Figure ‎4.74: TEM micrograph of combined 2 wt.% NS and 0.02 wt.% CNT

cement mortar, (a) mono dispersed CNT, (b) agglomerated NS and CNT

XRD results were presented in figures (4.75-4.79). it was found predominance of the

same anhydrous phases and presence of ettringite and calcium aluminate hydrates (C–

A–H) as hydration products in both control and blended with nanoparticles. it was

found that neither CNT nor NS caused a change in the type of hydration products

generated, since diffraction peaks did not change their position. This is in good

agreement with the literature, where it has been found that the MWCNT have no

a

b

117

chemical interaction in the hydration process and the NS modifies the amount of C–S H

generated through its pozzolanic reaction, but not the nature of the hydration products.

Figure ‎4.75: XRD the cement mortar containing 0.02% CNT (CNT0.02)

Figure ‎4.76: XRD the cement mortar containing 1% NS sonicated for 3 min

(NS1/3)

118

Figure ‎4.77: XRD the cement mortar containing 1% NS sonicated for 3 min

combined with 0.02% CNT (NS1/CNT0.02)


(NS2.5/12)

119


combined with 0.02% CNT (NS2.5/CNT0.02)

Figure (4.80) showed TGA result of the mix containing 0.03% CNT. The loss in

weight observed for the control Mix from 30 to 400 (13%) was much higher than the

mix containing carbon nano tube and nano silica (6.7%), this can be attributed to the

larger amount of CH in the control mix as compared to the mixes containing carbon

nano tube due to the behavior of the carbon nano tube as an extra nucleation sites

beside the nano silica increasing the C-S-H production and consequently decreasing

the CH content in the mix. This is in good agreement with the compressive strength

results.

121

Figure ‎4.80: TGA the cement mortar containing 1% NS sonicated for 3 min

combined with 0.02% CNT (NS1/CNT0.02)

121

D. ANOVA Statistical analysis

Based on the above mentioned results, and conclusions, the effects of studied

parameters were characterized and analyzed using ANOVA and regression models,

which can identify the primary factors and their interactions on the measured

properties. To find out the best possible mixture under the condition of this research

concept for the desired workability, and mechanical characteristics, a multi-objective

optimization problem was defined and solved based on developed regression models.

Statistical design of experiments can be used for optimization of linear and non-linear

systems. When non-linear effects and interactions of several different variables

(factors) are anticipated, factorial designs as well as response surface designs provide

the minimum number of experiments needed to investigate those effects and combine

them into a property response model. Two models were made a full factorial model in

addition the response surface was chosen to represent the data.

In what follows, the effect of NS and CNT % on the compressive strength results will

be discussed statistically and the optimum percentages will be determined.

1. Full Factorial Design

The estimated coefficients for the multiple regression models are shown in Table 4.4.

The P values correspond to tests of the hypotheses that the coefficients are equal to

zero. Values of P less than 0.05 indicate statistically significant non zero coefficients at

a 95% confidence level.

For the full factorial design, the factors (CNT, NS*CNT and CNT*CNT) had no effect

on the compressive strength of mortars, NS had a significant effect.

Table ‎4.4: Summary of compressive strength effect

Term Estimate Std Error t Ratio Prob>|t|

Intercept 332.78571 9.176614 36.26 <.0001*

NS -31 6.268821 -4.95 0.0078*

CNT -15.83333 6.268821 -2.53 0.0650

NS*CNT 13.25 7.677706 1.73 0.1595

NS*NS 38.928571 10.05248 3.87 0.0180*

CNT*CNT -5.571429 10.05248 -0.55 0.6089

122

The normal probability plot the residuals, shown in Fig. 4.81, can be used to judge

whether the residuals could reasonably be considered to follow a normal distribution,

and may also be helpful in detecting outliers. The residuals fall fairly well along a

straight line, while no outliers can be observed.

Figures 4.82-4.83 introduce helpful design charts correlating NS, and CNT percentages

with actual and predicted compressive strengths respectively. The NS percentages for

the predicted results were chosen to be from 0% to 2.5% from total binder content. It

should be noted that results are constrained with the proposed experimental concrete

mix.

Optimization analysis for the performance characteristics of concrete can be performed

for a combination of factor levels that simultaneously satisfy the desired requirements

for each response. The simultaneous optimization for each response has a low and high

value assigned to each goal. The goal field for responses is one of five choices: none,

maximum, minimum, target, or within a specified range. Each goal is assigned a weight

on a scale ranging from one to five (one being least important and five being most

important).

Factors included in the optimization analysis can be within their design range, or as a

maximum/minimum of a target goal. The goals are then combined into an overall

desirability function, which reflects the desirability ranges for each response. The

desirable ranges are from zero to one for any given response of the numerical

optimization, and by using statistical software (jmp in the current study); the highest

overall desirability function can be obtained. The goal seeking begins at a random point

and proceeds up the steepest slope to a maximum value. There may be two or more

maxima because of the curvature of the response surfaces and their combination into

the desirability function. The value equal to one within the experimental domain

represents the ideal case and a zero may indicate that one or more responses fall outside

the desirable limits.

Finally based on the proposed mix constituents, and without exceeding the CNT

saturation dosage, the most desirable NS, and CNT percentages were introduced in

figure 4.82, as well as the corresponding predicted compressive strength value.

123

Figure ‎4.81: Actual by Predicted Plot

Figure ‎4.82: Prediction Profiler

124

Figure ‎4.83: Relation between %NS, %CNT and compressive strength

2. Response Surface Design

The estimated coefficients for the multiple regression models are shown in Table 4.5.

The P values correspond to tests of the hypotheses that the coefficients are equal to

zero. Values of P less than 0.05 indicate statistically significant non zero coefficients at

a 95% confidence level.

Using response surface analysis showed a significant effect for the factors (NS, CNT,

their polynomial and interaction).

Table ‎4.5: Summary of compressive strength effect

Term Estimate Std Error t Ratio Prob>|t|

Intercept 420 6.391927 65.71 <.0001*

NS -18.92462 6.391927 -2.96 0.0143*

CNT -28.29163 6.391927 -4.43 0.0013*

NS*CNT -4.5 9.03955 -0.50 0.6294

NS*NS -38.25 6.391927 -5.98 0.0001*

CNT*CNT -31.25 6.391927 -4.89 0.0006*

125

The normal probability plot the residuals, shown in Fig. 4.84, can be used to judge

whether the residuals could reasonably be considered to follow a normal distribution,

and may also be helpful in detecting outliers. The residuals fall fairly well along a

straight line, while no outliers can be observed.

Figures 4.85-4.87 introduce helpful design charts correlating NS, and CNT percentages

with actual and predicted compressive strengths respectively. The NS percentages for

the predicted results were chosen to be from 0% to 2.5% from total binder content. It

should be noted that results are constrained with the proposed experimental concrete

mix.

Optimization analysis for the performance characteristics of concrete can be performed

for a combination of factor levels that simultaneously satisfy the desired requirements

for each response. The simultaneous optimization for each response has a low and high

value assigned to each goal. The goal field for responses is one of five choices: none,

maximum, minimum, target, or within a specified range. Each goal is assigned a weight

on a scale ranging from one to five (one being least important and five being most

important).

Factors included in the optimization analysis can be within their design range, or as a

maximum/minimum of a target goal. The goals are then combined into an overall

desirability function, which reflects the desirability ranges for each response. The

desirable ranges are from zero to one for any given response of the numerical

optimization, and by using statistical software (jmp in the current study); the highest

overall desirability function can be obtained. The goal seeking begins at a random point

and proceeds up the steepest slope to a maximum value. There may be two or more

maxima because of the curvature of the response surfaces and their combination into

the desirability function. The value equal to one within the experimental domain

represents the ideal case and a zero may indicate that one or more responses fall outside

the desirable limits.

Finally based on the proposed mix constituents, and without exceeding the CNT

saturation dosage, the most desirable NS, and CNT percentages were introduced in

figure 4.82, as well as the corresponding predicted compressive strength value.

As shown in Fig. 4.85, the optimum values of NS and CNT with highest desirability of

0.81 with a corresponding compressive strength value of 420.0 kg/cm2. The elliptical

nature of the contour plots indicates that the interaction between the corresponding

variables is significant.

126

Figure ‎4.84 : Actual by Predicted Plot

Figure ‎4.85: Prediction Profiler

127

Figure ‎4.86: Relation between %NS, %CNT and compressive strength

Figure ‎4.87: Contour line between %NS, %CNT and compressive strength

128

Chapter 5 : Summary, Conclusion and Recommendation

5.1. Summary

Considering the importance of the dispersion of Nano silica and carbon Nanotubes

powders with regards to their performance in cementitious mixes and the scarcity of

information on this subject, as well as the previous research observations that the NS

and CNT effect as cement substitution depends on its nature and production method,

and taking into account the reported effects on the ultrasound cavitations as a mean of

generating Nano structured solid.

The current research studied Nano dispersed materials, Nano silica and carbon

Nanotubes particles, production with a new innovative process by applying direct and

indirect sonication energy and homogenizer power. The influence of the method and

duration of applying direct or indirect sonication energy to produce Nano structured,

well dispersed cement, Nano silica and carbon Nanotubes was studied. The different

process parameters (homogenizer time, sonication time and liquid/solid ratio) were

optimized; experimentally, and statistically. The optimum method and time of

sonication for cement, Nano silica and carbon Nanotubes were optimized by

consequence optimized its particle size distribution and specific surface area. The

resulted optimum sonication time, method and percentages of Nano silica and carbon

Nanotubes were combined in cement mortars to be compared to original mortars as

cement substitution in concrete production.

The coupled effect of Nano silica and superplasticizer was investigated on the

compressive strength of cement pastes, also the effect of Nano silica and

superplasticizer to improve the dispersion of carbon Nanotubes. The difference between

local and imported carbon Nanotubes was examined by determine its particle size

distribution and compressive strength after 7 and 28 days. In order to optimize the

utilization of the carbon Nanotubes as a cement substitution, an extensive experimental

study was conducted through investigating the effect of different de-agglomerating, and

dispersing techniques (sonication, homogenization) of carbon Nanotubes on the gain in

compressive strength.

Finally, mortars gain of compressive and flexure strength were examined by the

combination between Nano silica and carbon Nanotubes after choosing the best time of

sonication for each of them and the method of mix to evaluate the optimum

combination percentages between Nano silica and carbon Nanotubes using hardened

tests for mortars, statistical factorial design, electron microscope (SEM), transmission

electron microscope (TEM), X-Ray diffraction (XRD), zeta potential, atomic force

microscope (AFM) and thermo gravimetric analysis TGA measurements. A full

factorial and response surface design were introduced, and the effects of studied

parameters was characterized and analyzed, which identified the primary factors and

their interactions on the measured properties.

129

5.2. Conclusion


Nano silica

5.2.1.1. The effect of sonication type on the dispersion of NS (stage 1)

Nano silica dispersion using direct and indirect sonication was significantly

enhanced.

The optimum time of direct sonication was found to be 1 minute, while 3 minutes

were found to be the optimum dispersion time when using indirect sonication.

By comparing the specific surface area and particle size distribution for Nano silica

particles; the optimum sonication method was chosen to be the indirect sonication.

5.2.1.2. The effect of sonication time on the dispersion of NS (stage 2)

NS with different dosages increased the compressive strength at 3 min. sonication

till 1% and then re-agglomerated for the higher percentages, the same trend occurred

for 6 and 12 min.

Flexure strength trend is opposed proportional with compressive strength due to the

reaction of NS in early ages so ettringite needles had the opportunity to increase the

flexure strength at the latter age.

The optimum time of sonication for the following percentages of NS by cement

weight 0.5%, 1%, 1.5%, 2% and 2.5% was 3, 3, 6, 12 and 12 minutes respectively.

In general, the gain in compressive strength in early age was higher than that in latter

age because most of NS reacted with CH early.

The optimum NS concentration by consequence time of sonication was 2.5% by

cement weight sonicated for 12 minutes using indirect sonication method. Gain in

compressive strength was 97% and 40% for 7 and 28 days respectively as compared

to the reference mortar.

Specific surface area is the dominant factor to determine the optimum dispersion

time and dosage of NS.

The highest flexure strength was reached using 0.5 wt.% NS sonicated for 1.5

minutes or 2 wt.% NS sonicated for 3 minutes. The gain in flexure strength was

100% as compared to the reference beam.


CNT

5.2.2.1. The effect of sonication type on the dispersion of CNT (stage 1)

Sonication is an effective dispersion method for carbon Nanotubes but a balance

between the degree of damage induced by it and the dispersion level desired has to

be found to guarantee that the MWCNT will have an adequate mechanical

performance when introduced in a cement matrix and exposed to compressive and

flexure strengths.

Carbon Nanotubes improves the mechanical behavior of composite at the small

strain. This improvement disappears at relatively large strain because the completely

131

de-bonded Nanotubes behave like voids in the matrix and may weaken the

composite. The increase of interface adhesion between carbon Nanotubes and

polymer matrix may significantly improve the composite behavior at the large

strain(80).

The use of CNT as received resulted in loss of compressive strength (-15%).

The adding of SP helped the CNT to disperse well and increased the compressive

strength of cement pastes by 40% as compared to that one contained CNT only, so

SP enhanced significantly the dispersion of CNT.

5.2.2.2. Introduce a novel technique for the dispersion of CNT (stage 2)

The optimum treatment method of CNT (S40H10) obtained a gain 62% in

compressive strength.

Homogenizer (H60) breaks the CNT particles into equal sizes which is not

recommended to act as bridges for different sizes of cracks into the matrix.

5.2.3. Optimizing the couple effect of Nano silica and carbon Nanotube

on the mechanical properties of cement composites (phase 2)

5.2.3.1. Optimizing the effect of different dosages of CNT on the mechanical

properties of cement mortars (stage 1)

Within the studied different amounts of CNT, 0.03% CNT by cement weight is the

optimum percentage as compared to 0.01 and 0.02%.

The gain in compressive strength obtained for 0.03 wt.% CNT was 50% and 23%

after 7 and 28 days respectively.

No matter the dosage used of CNT to increase the flexure strength, the flexure

strength increased significantly by 67% for all CNT mixes as compared to the

control beam.

5.2.3.2. Optimizing the couple effect of different dosages of NS and CNT on the

mechanical properties of cement mortars (stage 2)

The combined effect of NS and CNT was examined on cement mortars. The

optimum combination was 0.02% CNT and 1% NS. Gain in compressive strength

obtained was 72% and 35% after 7 and 28 days.

As for the flexure strength, mortars which contained CNT and NS together, the

optimum content was 0.5% NS sonicated for 3 minutes combined with 0.01% CNT

by cement weight. The gain in strength was 100%.

The combination of NS with low amount of CNT had a positive effect on the

hydration reaction, presence of individual CNT worked as extra nucleation spots for

the hydrates and enhanced the activity of the NS.

The combination of CNT and a high amount of NS had negative effect on the

hydration reaction. NS sucks water between its particles and affect negatively the

production of hydrates of the cement due to its re-agglomeration.

The combination of NS and a high amount of CNT had negative effect on the

hydration reaction. Ca(OH)2 affected the stability of CNT dispersion due to its

interaction with negative charges of the OH functional groups, which caused

131

generated re-agglomeration of CNT and decreased the availability of Ca(OH)2 for

the NS to react with and produce more C-S-H.

As for the statistical analysis, the response surface model showed to represent the

CNT – NS coupled interaction effectively as compared to the full factorial model.

132

5.3. Recommendation

The research work achieved in this thesis has showed several areas where further

research is necessary. It is recommended that fulfillment should be made into the

following:

Study the effect of more dosages of NS and CNT on the mechanical properties of the

cement composites.

Study the effect of different types of fly ash, silica fume, micro silica etc. combined

with CNT.

Study the effect of specific surface area to get optimum compressive strength.

Higher percentages of CNT by cement weight combined to NS is strongly

recommended to study its effect.

Study the effect of adding different weights and types of superplasticizer on the

dispersion of CNT and the mechanical properties of cement composites by

combined to NS.

Introduce a technique for the dispersion of NS and CNT together.

133

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Appendix A: Mastersizer 3000 result sheet (NS)

142

Appendix B: Mastersizer 3000 result sheet (CNT)

مهخص انرسانه

ة "اجب اؼشفخ١خ اج١ئزالئ ػذ٠ذح زؾغ١ اخشعبخ غؼب بعجخ زذ عدا ف ا٢خ األخ١شح، ث

ب أ١خ ػ١خ وج١شح ثغجت رىع١ب ا ذعززثإاشذ. مبخ األعذىبد اخؼشاء" رؾغ١

اظبػبد لذ رى لبدسح ػ إػبدح رظ١ اؼذ٠ذ زبزش. اعزخذابد اغذ٠ذح غض٠ئبد ف طبق اإل

.د ٠غجك ب ض١ازغبد اؾب١خ از رؼ ػ غز٠ب

غبص صب أوغ١ذ إجؼبسطبلخ، غ اسرفبع غجخ عزالوب إاؽذح أوضش اظبػبد رؼزجش طبػخ األعذ

اىشث ثـغجت ػ١بد رظ١غ ااد اى١١بئ١خ ز١غخ ؾشق الد. لذ ر رع١ عد ثؾض١خ اعؼخ ؾذ

عزخذا ااد األعز١خ ازى١١خ از رؾ ئأ ث غ١ وفبءح ػ١خ رظ١ؼإب ػ ؽش٠ك رؾ األعذرؤص١ش طبػخ

اطج١ؼ١خ، غجبس اغ١١ىب. اجصال١خ اؼبد ض اشبد ازطب٠ش، ؽج١جبد خجش افش، ااد األعذعضئ١ب ؾ

١ذسوغ١ذ اىبغ١ بػ غلذ ر دساعخ ااد األعز١خ ازى١١خ ف اخشعبخ ااد اجصال١خ زف

.زشغ١ اؾظي ػ اد ١ذسار١خ زؾغ١ اخاص ا١ىب١ى١خ خشعبخ زبزب لبث١زب

ف اخشعبخىبػ إاظغ١شح ثغجت مبخ اشذ ازشبس اششؿ ف عز١خ بدح ذ٠ب ػؼفاأل ىبدا

اششؿ. اشمق ف اشآد ز زشبسإ مبخ اشذ اؾذ جىش. ٠غزخذ ؽذ٠ذ ازغ١ؼ ف رؾغ١ ف ع

فبر٠خ اغبصاد خالي رفبػ و١١بئ ف اخشعبخ. اغ١ىب ام، رفبػإ عدباخشعب١خ ٠شعغ

د ام١خ ٠ؤد إ طذأ ؽذ٠ذ ازغ١ؼ ٠غجت رذس اخشعبخ. ف اؼم باغب رض٠ذ اشمق ف اخشعبخ،

، أصبسد أ١بف غ١طشح ػ اشمق األعذ ىبدف األ١بف رؤص١ش ذساعخ األثؾبس رجذابػ١خ،

ؼب١خ ف رؼض٠ض ظففخ االعذ. ػبدح ب ٠ز ا ربخاطب ا١ىب١ى١خ لذس زب اجبؽض١ ظشا إاب اخزفخ

أبث١ت أ ءخشا عزخذا األ١بفئبق ١زش /أ ػ اغز اغضئ ثاد األعز١خ ف طرؼض٠ض رع ا

زش٠خ.اىشث اب

فاغب أل ١ذسار١خ، اد ززفبػ غ ١ذسوغ١ذ اىبغ١ إلزبط بن ؽبعخ إ اد اب غ األعذ

ثضبثخ خشعبخ، ؽ شىخ ازآو، اؼ ارم١ فبر٠خ اغبصاد ابء ف زىض١ف ظففخ األعذ،اشوجخ

ؾذ اعزجذاي األعذأخ١شا ،ض٠بدح لح اشذاظففخ ف ا١ىش اب م١بط ف شمقوجبس

.أوغ١ذ اىشث جؼبصبد صبإ

ش، وضبفزب رغب بز ٠٣م١بط اب. ٠جغ زعؾ لطشب وش٠خ ف غؾق أث١غ عض٠ئبر ب اغ١١ىب

عذ ثغجت ازفبػ ألا١ىب١ى١خ شاؽ األعذ، رؼض٠ض اخاصع١١ىب واح رؼ اب .٠ / وغ ٢١.١

ؼ أ٠ؼب ٠ا١ذسار١خ. وب ااد ص٠بدح إزبط اجصال غ ١ذسوغ١ذ اىبغ١ خظ١ظب ف ع جىشح عذا

اغبؽخ ئ خ )١غذ بن ؽبعخ إ ابء خ ثغجت ؽغ اغغ١بد اذل١ماشوجبد االعز١ وؾش غب ف

األعذ، اؾذ ازظبص ابء ب ٠ض٠ذ زبخ اشوجخ. رغبػذ اب اغ١١ىب ػ خفغ ؾز اج١١خ

٠ى ألعذاوغ ٤وغ اغ١١ىب رغؼ ثزخف١غ ؽا ٢عذ، إػبفخ ألطبد اخشعب١خ وجذ٠ ف اخ

.عز١خاأل شوجبدوب رؾغ مبخ اؼغؾ أ رى أػ

أب شخ أطجؾذ أبث١ت اىشث ابزش٠خ ػع اؼذ٠ذ اذساعبد ثغجت خظبئظب ا١ىب١ى١خ. وب

ف اشوجبدىش١ ا م١بط اب ؾبء ف اذائش رشى١ عغس ػجش اششؿ فغب٠خ لبدسح ػ اإل

عز١خ. أبث١ت اىشث اب٠خ لاد أجث١خ عفبء، شىذ إب ػ ؽش٠ك عذاس اؽذ أ ػذح عذسا ألا

ألبث١ت اىشث زؼذدح اغذسا اطي ٠ى أ بزش ٢٣٣-٤طؾبئف اغشاف١ ، ألطبسب رزشاػ ث١

وغ ١٣٣٣ع١غب ثبعىبي ف ؽ١ اىضبفخ ؽا ٠٣٣٣-٢٣٣٣ث١ رظ إ م١بط ا١زش. ؼب ٠غ ٠زشاػ

أل ١خ عزأإ أوضش ػذح آالف، ازلغ أ رزظ شوجبد ٠٣غجخ اطي إ امطش رزشاػ ب ث١ .٠ /

خالي اح بثخثضرؼ (. أبث١ت اىشث اب٠خ)ض أ١بف اضعبط أ أ١بف اىشث أشذ ااد ازم١ذ٠خ

ألب اخشعبخ . أب رم غب١خخالي ازفبػو١خ اؾشاسح اجؼضخ رض٠ذ األعذ زه ف ابء غ رفبػ

اغػبد اظ١ف١خ اطؼخ ػ اغب. ذ ؽغ١ؽررؾغ رص٠غ ١خ األعز خطخوبدح بئخ ف ارؼ

ف شؿر١ذ عغس ػجش اش ااد ا١ذسار١خ لبدسح ػ ازفبػ غعطؼ أبث١ت اىشث ابزش٠خ

بد٠خ ف ص٠بدح لح اض اشوجزشأبث١ت اىشث اب رغبػذ ، زه١خاالعز بداشوج فب م١بط ا

.١خاالعز

از خطب ثببء ب رزىز غب٠خ ػذاشىخ اشئ١غ١خ ف اعزخذا ب اغ١١ىب وشث األبث١ت اب٠خ أ

عزخذائذ ازىزالد ث١زشزفؼبخ مبزب. بن ؽبعخ رؼؼف ب اخشعبخ ف دبرغ٠ف رغجت عد

ثبعبد فق ازىزخ ١بوارفىه ،زغت ػ ل ازشاثؾ ابرغخ ازفبػ غ ابءاعبد فق اظر١خ

إػبفخ اخطبد .اؾغ ٠خ٠غؼ ثبالعزفبدح اإلىببد اىبخ اد بجبششح اغ١ش اجبششحاظر١خ

رغبػذ ذ ازىز ػ ؽش٠ك إؽذاس ل ازبفش اىشثبئ١رغبػذ ػ رشز از بداى١١بئ١خ ابعجخ ض اذ

ب لبا ثؼ١خ رشز١ذ ز ازىزالد ػ وب أ ثؼغ اجبؽض١ عبثم .أ٠ؼب ف مبخ اؼغؾ خطبد األعز١خ

ذبدعزخذا اىضف اإل أ ص إػبفخ اد فشلخ خطخ األعز١خ. وبرم١خ اعبد اظر١خ ؽش٠ك إعزخذا

.اخؾ ألعذ٠ؾغ لبث١خ

١ت اعبد فق اظر١خ ، ض األبث١ت اب٠خ اىشث١خ، أطجؾذ رؼزذ ػ أعب٠خ اؾغ بارشزذ ااد

غزخذ اعبد فق اظر١خ ف غػخ اعؼخ اؼ١بد اج١ع١خ رزفش٠ك اى١١بئ١خ. خظ١ظب غ اد ا

ذ ؼظ ازطج١مبد ػب١خ اىضبفخ زشز١ذ أضخ ػ اؼ١بد اف١ض٠بئ١خ. رغزاغبغخ ا .اف١ض٠بئ١خ اى١١بئ١خ

رم١خ اعبد فق رؤص١ش ام ازغ٠ف ب ٠م ؽغ اغغ١بد وغش اىز.عبد فق اظر١خ ػ

رزؾمك ازم١خ . ؼ١خ٠ى رطج١مب ف ثطش٠مز١: جبششح أ ثشى غ١ش جبشش خالي عذسا اؾب٠خ اظر١خ

ح غ١ش جبششا ازم١خرف١ز ٠ز. جبششح ف اػبء اؼ١خ ؽش٠ك غشجبششح ػ عبد فق اظر١خ اجبششح

ثبعبد فق اظر١خ. ز االخزالفبد رغؼ و ظب بعت غػخ خزفخ بئ عزخذا ؽبئث

اؼبغخ ى ف١ذ، ١ظ فمؾ ف خفغ لذضدط ا رم١خ اعبد فق اظر١خ ازطج١مبد. اعزخذا ظب

ف اغبئ ؽ١ش ٠ز رفش٠ك غشبف ؽب ابء، ثذال فق اظر١خرم١خ اعبد عزخذاإأ٠ؼب ألب رز١ؼ

. با٠خ أ اد زشاب اىشث أبث١ت

ىشث أبث١ت ا ب اغ١١ىب ا عض٠ئبد ذ١رؤص١ش اذ ازفق ػ رشز : ا٢ر إ دساعخ ب وب اؾبفز

لح رض٠ذ ب ع١١ىبا ، عغ١بدظففخ اضلح رض٠ذ بزش٠خىشث اأبث١ت اثب أ .ابزش٠خ

رغ١دساعخ ٠ى وب .ظففخ ا١ىب١ى١خ اضبئ ب ػ اخاص ازؤص١ش، ف اغزؾغ دساعخ اؼغؾ

فازؼبسة .١ىباب ع١ ثئػبفخ خظففخ األعز ف رؾغ١ رفبػب أبث١ت اىشث ابزش٠خ رشزذ

رؾم١ك .زؼض٠ض اظففخ أبث١ت اىشث ابزش٠خ لح اؼغؾ رؾذ رؤص١ش إػبفخ زبئظ اذساعبد اخزفخ

ازار. الجذبفب د٠ش فبي ظشا مح افؼبي ألبث١ت اىشث ابزش٠خ التشتت

أهذاف انبحث

رشز١ذ غبؽ١ك ب اغ١١ىب أبث١ت اىشث ابزش٠خ ف١ب ٠زؼك ثؤدائب ف اخطبد األعز١خ ظشا أل١خ

أبث١ت اىشث اب ع١١ىب ذسح اؼبد ؽي زا اػع، فؼال ػ األثؾبس اغبثمخ ذساعخ رؤص١ش

ألخز ثؼ١ اإلػزجبس أصش ازغب٠ف عبد ػالعب، ا ػ شوجبد األعذ ؽغت ؽج١ؼزب ؽش٠مخ ابزش٠خ

:فق اظر١خ وع١خ زشز١ذ ؽج١جبد اب. ٠ذف اجؾش اؾب إ

رؾغ١ رشز١ذ عض٠ئبد اب اغ١١ىب خالي رطج١ك رم١خ اعبد فق اظر١خ إب

.جبششح أ غ١ش جبششح

بزش٠خ ثبطشق اف١ض٠بئ١خ إدخبي رم١خ عذ٠ذح ف رشز١ذ عغ١بد أبث١ت اىشث ا

.اى١١بئ١خ

خالي دظ اب دساعخ رؤص١ش ازشز١ذ ػ اخاص ا١ىب١ى١خ شوجبد األعز١خ

.غ عشػبد خزفخ ع١١ىب أبث١ت اىشث ابزش٠خ

مه أجم تحقييق األهذاف انمشار إنيها سابقا :

ؽج١جبدغ١ش جبششح زفش٠ك اجبششح أ اظر١خ ا فق عبداع١ز دساعخ رؤص١ش ؽش٠مخ ذح رطج١ك

ذ عغ١بد ١رشز ظرخ ػا رص٠غ ؽغ اغغ١بد ذساعخ رؤص١شب ع١١ىب. ع١ز ػشع ا

ب اغ١١ىب ػ رؾز ١خ اغضح ازاألعز اشوجبداغ١١ىب. رط١ف اخظبئض اشئ١غ١خ

وزه رؾغ١ SEM, TEM, TGA XRD ض رم١بد خزفخعزخذائث ػب ع١ز ازؾم١ك

.األض ب ع١١ىب زص٠غا

أ اخبؾ غ١ش جبششح اجبششح أ اظر١خ ا فق اعبدع١ز دساعخ رؤص١ش ؽش٠مخ ذح رطج١ك/

ض ؼبالداإلخز١بس األ اغض٠ئبد. ذ١رشز ػ٠خ أع إظبس رؤص١شب زشألبث١ت اىشث اب

ثشى رغش٠ج. ع١ز ػشع رص٠غ ؽغ ع١ز إخز١بسب خزفخ )عشػخ اخبؾ الذ طرخ( ا

ذ. رط١ف ١اغغ١بد ذساعخ رؤص١ش أبث١ت اىشث اب٠خ أعة اؼالط األض ػ عض٠ئبد ازشز

اغش اإلىزش ابعؼ، خالي اعزخذا رم١بد خزفخ ض األعز شوجبداخظبئض اشئ١غ١خ

.اؾشاس٠خ م١بعبداغش اإلىزش ابفز، ؽ١د األشؼخ اغ١١خ، إىببد ص٠زب ازؾ١ اص

ؽش٠ك ػاىشث ابزش٠خ أبث١ت ذ ب اغ١١ىب ١ػ رشز اذ ازفقدساعخ رؤص١ش

.عذؼبع١ األاخزجبساد لح اؼغؾ

رص٠غ ؽغ رؾذ٠ذ ػ ؽش٠كزش٠خ اؾ١خ اغزسدح افشق ث١ أبث١ت اىشث اب خزجبسإ

.أ٠ب ١٢ ٧ذ اغغ١بد ثؼذ اؼالط لح اؼغؾ ثؼذ ١اغغ١بد إلظبس افشق ف رشز

اض ػ لح اؼغؾ ػبفخ ب اغ١١ىب أبث١ت اىشث ابزش٠خ ؼب إ، دساعخ رؤص١ش أخ١شا

ؽظبئ. رط١ف اخظبئض اشئ١غ١خ زفش٠ك إ ثزؾ١ ازبئظ عزؼشاعإ. ع١ز األعز١خ شوجبد

عزخذا اغش اإلىزش ابعؼ، إب اغ١١ىب اىشث األبث١ت ابزش٠خ ٠ى خالي

ازؾ١ اص بداغش اإلىزش ابفز، ؽ١د األشؼخ اغ١١خ، إىببد ص٠زب اؾشاس٠خ ام١بع

انتاني : انىحى عهى عهى خمسة فصم انرسانة وتشتمم

انفصم األول : انمقذمة ثبإلػبفخ إ رؼش٠ف األذاف اشئ١غ١خ رىع١ب اب ف اخشعبخ،عزؼشع مذخ إ ،ف افظ األي

.اجؾض طبق اؼ ػ رؾذ٠ذ ؼبغزب فؼال اجؾش ؽب از ٠ذس اشىخ

وانذراسات انسابقة انفصم انثاوي :انمراجع

٠خ ، فؼال زشاىشث اب أبث١ت ب اغ١١ىب اؽي خظبئض عبثمخ دساعبد شاعغ ،ف افظ اضب

فق اعبد. ثبإلػبفخ إ ره اعزؼشاػب ؽي رؤص١ش داخ اشوجخ عو ػػ اؼا از رؤصش

ااد اذ ازفق ػ رص٠غ رزظ ثغجت خؾ اد اب ف ا١ب، فؼال ػ رؤص١شؾ ازىز اظر١خ

رؤص١ش ابع١١ىب أبث١ت اىشث ذ . ع١ز روش اعزخذا األعب١ت اإلؽظبئ١خ اخزفخ ف رؾ١ابزش٠خ

.االعز١خ اشوجخ ابزش٠خ ف

انبحثية انفصم انثانث : انخطة

، اؼذاد از عز١خاشوجخ األ ف ذ ااد اغزخذخ١ رم١بد رشز ثذءا اضبش ٠ض ثشبظ ثؾضافظ

ئ اغزخذخ ف رم١١ ازبئظ. ، رز غ خطخ فظخ ؼ وزه رط١ف اعبف اجؾش خذذأعز

اظر١خ اعبد عزخذا رم١خئث اد اادوشث األبث١ت ابزش٠خ، ػ١خ إػذب عزخذا ب اغ١١ىإ

وشث ثؼذ إػبفخ ب اغ١١ىب ٠ب ١٢ ٧ثؼذ ا١ىب١ى١خ اجبششح اغ١ش اجبششح، وزه اخزجبس اخاص

.األبث١ت اب٠خ

انفصم انرابع : انىتائج وانمىاقشة

.إلػبفخ إ بلشخ وبخ رفغ١ش ازبئظعش٠ذ، ثب٠ض افظ اشاثغ زبئظ اجشبظ ازغش٠ج از أ

انفصم انخامس :انمهخص، اإلستىتاجات وانتىصيات

جؾش. زبئظ ااجؾض١خعززبعبد رط١بد اخطخ إػ ، فؼال شعبخف افظ األخ١ش، ع١ز ػشع خض

اىشث ابزش٠خ ب ع١١ىب أبث١ت ا ثئػبفخغ خظبئض عذ٠ذح زطسح األعذإلزبط ظففخ رذف

.االعز١خ شوجبدإ ا

:يهي اإلستىتاجات فيما تهخيص ويمكه

ػ لزائف ب االعذ. وب اغغ أبث١ت اىشث ابزش٠خ ع١١ىب ر فؾض ازؤص١ش اشزشن اب•

اؼغؾ از ر اؾظي ػ١ب ع١١ىب. اض٠بدح ف لح ٪ ب1 أبث١ت اىشث ابزش٠خ٪ 0.02األض

أ٠ب. 22 2٪ ثؼذ ٪33 22

ع١١ىب ؼب، وب اب أبث١ت اىشث ابزش٠خرؼذ از االعز١خ أب ثبغجخ مح اض شوجخ•

٪ 0.01غ دلبئك خطب 3ذح جبششح اغ١ش اعبد اظر١خ رؤص١ش رؾذ ع١١ىب ٪ اب0.3ؾز األض

CNT 100اض٠بدح ف امح ثبص االعذ. وبذ.٪

رؤص١ش إ٠غبث ػ سد فؼ ابء عد أبث١ت اىشث ابزش٠خع١١ىب غ و١خ ل١خ وب ض٠ظ اب•

.ا١ذسار١خ ااد و١خ و١خ صاددع١١ىب صاد شبؽ اب ، ؽ١شأبث١ت اىشث ابزش٠خ افشد

ع١١ىب اب ؽ١ش رؤص١ش عج. ع١١ىب و١خ ػب١خ اب غ أبث١ت اىشث ابزش٠خوب ض٠ظ •

رزض ابء ث١ اغض٠ئبد، رؤصش عجب ػ إزبط ١ذساد االعذ ظشا إلػبدح ازىز.

رشزذرؤص١ش عج. أصشد ػ بزش٠خأبث١ت اىشث اع١١ىب ػ و١خ ػب١خ وب ض٠ظ اب•

، ب رغجت OHثغجت رفبػ غ اشؾبد اغبجخ اغػبد اظ١ف١خ أبث١ت اىشث ابزش٠خ

إزبط ع١١ىب ابزفبػ غ اىبغ١ ١ذسوغ١ذ اخفبع رافش أبث١ت اىشث ابزش٠خإلػبدح رىز

١ذسار١خ.ا اض٠ذ ااد

ثغذ أؽذ ؾذ ؾذ ٠عف :ةذسـمهى

٢٠٠٣\٣٠\١٣ تاريخ انميالد:

ظش٠خ انجىسية:

١٣٢١\٢٣\٢ تاريخ انتسجيم:

..........\....\.... تاريخ انمىح:

اإلشبئ١خ اذعخ انقسم:

اؼ بعغز١ش انذرجة:

عشاط ػجذاؼض٠ض إعبػ١ ؾذ د...أ انمشرفىن:

ػجذاؾى١ افم عب ذد. ؾ

)ازؾ اخبسع( ؽ ؾذ د. اؽذ خؼش.أ انممتحىىن:

سعت )ازؾ اذاخ( أ.د. اؽذ

)اششف اشئ١غ( عشاط ػجذاؼض٠ض إعبػ١د. ؾذ .أ.

ػجذاؾى١ افم )ششف( عب د. ؾذ

عىىان انرسانة:

زؾغ١ اخاص اىشث ابزش٠خ ؽج١جبد اغ١١ىب ابزش٠خ ؽش٠مخ غزؾذصخ زص٠غ ابث١ت

ا١ىب١ى١خ شوجبد االعز١خ

انكهمات انذانة:

رىز. ع١١ىب، اعبد فق اظر١خ، األض، ؽش٠مخ غزؾذصخ، ، ابابث١ت اىشث ابزش٠خ

مهخـص انرسانة:

أداء اظر١خ اجبششح أ غ١ش جبششح زؾغ١ ش٠مخ ذح رطج١ك رم١خ اعبد فقدسط زا اجؾش رؤص١ش ؽ

ازم١خ اجبششح أ اغ١ش جبششح / أ رفش٠ك ؽج١جبد اب ع١١ىب فؼال ػ رؤص١ش ؽش٠مخ ذح رطج١ك ز

األثؾبس اغبثمخ ػ ف أعجبة ازبلؼبد ازوسح أع رػ١ؼ اخبؾ ألبث١ت اىشث اب٠خ ره

ز ااد. صب١ب، ر دساعخ رؤص١ش اذ ازفق ػ رشزذ ب اغ١١ىب اىشث األبث١ت ابزش٠خ عن

وال اب ؽش٠ك االعزفبدح اض لح اؼغؾ ؼبع١ اإلعذ. أخ١شا، ر دساعخ رؤص١ش دظ

اعزذد خزفخ ػ اخاص ا١ىب١ى١خ شوجبد األعز١خ وب ش٠خ ثغتع١١ىب أبث١ت اىشث ابز

اشوجبد االعز١خ. عن زفغ١ش اإلؽظبئ١خ إ أثشص االعب١ت اخزفخ اؼ١بد ث١ مبسخا ف اشعبخ

ؽش٠مخ غزؾذصخ زص٠غ ابث١ت اىشث ابزش٠خ ؽج١جبد اغ١١ىب ابزش٠خ

اخاص ا١ىب١ى١خ شوجبد االعز١خزؾغ١

اػذاد

ثغذ أؽذ ؾذ ؾذ ٠عف

عبؼخ امبشح –سعبخ مذخ إ و١خ اذعخ

وغضء زطجبد اؾظي ػ

دسعخ بعغز١ش اؼ

ف

اإلشبئ١خ اذعخ

٠ؼزذ غخ ازؾ١:

ازؾ اخبسع ؽ ؾذ أؽذ خؼشاذوزس:

ام جؾس اشوض -اذ١خ لغ اذعخ سئ١ظ بئت أعزبر

ازؾ اذاخ أؽذ ؾد بش سعتاذوزس:

عبؼخ امبشح -اذعخ و١خ - أعزبر دوزس مبخ ااد

اششف اشئ١غ عشاط ػجذاؼض٠ض اعبػ١ اذوزس: ؾذ

عبؼخ امبشح -اذعخ و١خ -دوزس مبخ ااد غبػذ أعزبر

ػؼ ػجذاؾى١ افم عب اذوزس: ؾذ

ام جؾس اشوض - اذ١خ اذعخ ثمغ ثبؽش

عبؼــخ امبــشح -و١ــخ اذعــخ

س٠ـخ ظـشاؼشث١ــخع -اغ١ـضح ١٣٢٠


زؾغ١ اخاص ا١ىب١ى١خ شوجبد االعز١خ

اػذاد

ثغذ أؽذ ؾذ ؾذ ٠عف

عبؼخ امبشح –سعبخ مذخ إ و١خ اذعخ



ف

اذعخ اإلشبئ١خ

رؾذ اششاف

ػجذاؾى١ افم عب د. ؾذ

عشاط ػجذاؼض٠ض اعبػ١ د. ؾذ.أ.

اذ١خ اذعخ ثبؽش ثمغ

ام جؾس اشوض

دوزس مبخ اادغبػذ أعزبر

عبؼخ امبشح -اذعخ و١خ

عبؼــخ امبــشح -ذعــخ و١ــخ ا

عس٠ـخ ظـشاؼشث١ــخ -اغ١ـضح ١٣٢٠


زؾغ١ اخاص ا١ىب١ى١خ شوجبد االعز١خ

اػذاد

٠عف ثغذ أؽذ ؾذ ؾذ

عبؼخ امبشح –اذعخ سعبخ مذخ إ و١خ



ف

اإلشبئ١خ اذعخ

عبؼــخ امبــشح -و١ــخ اذعــخ

عس٠ـخ ظـشاؼشث١ــخ -اغ١ـضح ١٣٢٠

passant master thesis

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Transcript of passant master thesis