P. SRINIVASANshodhganga.inflibnet.ac.in/bitstream/10603/45474/10/...honeycombs, voids created by the presence of PVC pipes and steel box, etc., has been demonstrated. For the determination

i

CONDITION ASSESSMENT AND EVALUATION OF

CONCRETE STRUCTURES BY ADVANCED

NON-DESTRUCTIVE METHODS

A THESIS

Submitted by

P. SRINIVASAN

for the award of the degree

of

DOCTOR OF PHILOSOPHY

DEPARTMENT OF CIVIL AND STRUCTURAL ENGINEERING

ANNAMALAI UNIVERSITY

ANNAMALAI NAGAR- 608 002

TAMILNADU, INDIA

APRIL 2013

ii

ACKNOWLEDGEMENTS

I express my sincere and hearty gratitude to my research guide

Dr. S. Thirugnanasambandam, Associate Professor, Department of Civil and

Structural Engineering, Annamalai University, Annamalainagar and my co-guide

Dr. K. Ravisankar, Chief Scientist and Head, Structural Health Monitoring

Laboratory, CSIR-Structural Engineering Research Centre, Chennai whose expert

guidance and inspirations helped me to carry out this research work successfully. Their

continuous encouragement and motivation helped me in completing the research work

in time.

I would like to thank Dr. Nagesh R. Iyer, Director, CSIR-Structural Engineering

Research Centre, Chennai, for his kind permission, support and encouragement in

carrying out the research work at Annamalai University and also for providing all the

infrastructure facilities for conducting the experimental work.

I would like to thank Vice-Chancellor, Registrar, Controller of Examinations, and

Dean, Faculty of Engineering and Technology, Annamalai University for their support

and encouragement during my course work. I sincerely thank

Dr. C. Antony Jeyasehar, Professor and Head, Department of Civil and Structural

Engineering, Annamalai University, for his full support and encouragement during the

entire tenure of this research work.

I also thank Dr. N. Lakshmanan, Former Director, CSIR-Structural Engineering

Research Centre, Chennai, for his kind permission to carry out this research work. I

thank Dr. K. Ramanajaneyulu for his support in the experimental work.

I would like to thank Mr. S.G.N. Murthy, Principal Scientist, CSIR-SERC and

Mr. S. Bhaskar, Principal Scientist for their support during the evaluation with

different NDT techniques.

My special thanks to Mrs. Sulochana Peethambaran, Sr. Technician(Concrete) for

her support during the experimental work and also in the typographical work of this

thesis.

My thanks are also due to Mr. V. Chellappan & Mr. S. Elumalai, former

Technicians, Advanced Concrete Testing and Evaluation Laboratory of CSIR-SERC,

Chennai for providing the assistance during the experimental investigations. Also, I

would like to thank my other scientist colleagues of Advanced Concrete Testing and

iii

Evaluation Laboratory, Structural Health Monitoring Laboratory and Advanced

Materials Laboratory for their support during the casting of large scale reinforced

concrete specimen and other help provided to me.

My thanks are also due to Mrs. Latha Balasundaram, Sr. Technician and project

assistants of drawing section in preparation of Autocad drawings. I also thank the

project assistants, post graduate students and skilled laborers of ACTEL who has

helped during the experimental work.

I thank Mr. A. Vengatachalapathy, Assistant Professor, Department of Civil

Engineering, Annamalai University for his moral support extended to me.

Special thanks are due to my wife, Dr. K. Kalaivani, and my children, S.Keerthana

and S.Gokul Ganesh, and my brothers and sister, and my in-laws for all their love and

support during the course of this work.

I would like to dedicate this thesis to my parents Mr. R. Parthasarathy (late) and

Mrs. G. Neelavathy for their love and affection and, for their deep interest to pursue

my studies to the highest level possible.

Finally, I bow to the Almighty for giving me everything in life. In response, my only

prayers are due to him.

Date: P. Srinivasan

iv

ABSTRACT

KEYWORDS : Concrete, Reinforcement, Non Destructive testing, Ground Penetrating

Radar, Ultrasonic Pulse Echo, Impact Echo, Thickness Measurement,

Voids, Ducts, Grouting

Reinforced and pre-stressed concrete are widely used for the construction of

infrastructures such as bridges, industrial structures, buildings, etc. Most of the time,

the quality of the concrete mix is assumed to be guaranteed but due to the congestion of

reinforcement and the quality control exercised during placing and vibrating,

honeycombs and voids are likely to be present in the hardened concrete. The presence

of voids leads to the early deterioration of concrete and corrosion also sets in. The

corrosion of reinforcement causes damage to the cover concrete and also section loss in

the area of steel. In the case of pre-stressed concrete members, the corrosion leads to a

catastrophic failure without any warning. Hence, it becomes necessary to evaluate the

condition of concrete using Non Destructive Techniques (NDT) and Partially

Destructive Techniques (PDT). The Ultrasonic Pulse Velocity (UPV) method which is

widely adopted till now gives the relative quality and integrity of concrete and is based

on the transit time. The rebound hammer gives the quality of concrete in the cover zone

based on the rebound number.

Most of the time, the structural details may not be available and it becomes necessary

for the engineer to evaluate the presence and to quantify the reinforcements in order to

evaluate the condition of the structure. It will also be useful for the future extension of

the structure and will also be highly helpful in retrofitting of reinforced concrete framed

structures to meet the high seismic demand. In addition, for the forensic analysis of

concrete structures, it becomes necessary to explore various features of the reinforced

concrete structure such as thickness, presence of reinforcement and ducts, PVC pipes,

embedments, honeycombs, etc., in a rapid manner.

v

In this study, the efficiency of the advanced non destructive techniques namely Ground

Penetrating Radar (GPR), Ultrasonic Pulse Echo (UPE) and Impact Echo (IE) methods

have been studied on different concrete specimens. The major advantage is that all are

one sided techniques and can be used from one side only and it can be carried out in a

rapid manner also. With the development in the signal processing, the details/features

such as thickness, reinforcements, voids, etc., can be seen in the form of images. The

cross sectional images namely B-scan and C-scan are obtained by processing the

reflected signals.

In the present work, a unique two storey large scale reinforced concrete specimen has

been constructed with various features such as thickness variations in the slabs,

different reinforcement percentages, inclusion of voids, PVC pipes, steel plates/box in

the structure. The efficiency of the advanced NDT techniques namely GPR, UPE and

IE have been studied extensively on this unique large scale reinforced concrete

structure constructed with various features. The UPV testing (IS:13311-Part-1 and

ASTM-C597) is a point based measurement and gives the quality of concrete based on

the velocity. The limitation of the ultrasonic pulse velocity method in identifying the

honeycombs, voids created by the presence of PVC pipes and steel box, etc., has been

demonstrated.

For the determination of minimum size of void that can be detected using GPR and

UPE and also the effect of reinforcement on the determination of void, experimental

studies were carried out with different sizes of voids kept at different locations i.e., at

different depths under the reinforcement. The 25 mm, 50 mm and 75 mm cubical voids

were introduced. The voids were created with Expanded Polystyrene (EPS) blocks and

the dielectric constant of EPS is 1.05 which is closer to air and the advantage of this is

taken in the simulation of voids. The effect of reinforcement on the determination of

vi

void in radar is to be explored because the signals from the radar is of electromagnetic

in nature, and reflected because of the metallic nature of the reinforcement. The

limitation of the UPV method in determining the honeycombs and voids have been

explained and demonstrated in this research work.

To study the evaluation of the presence of duct, influence of first layer of reinforcement

and the efficiency of grouting, two concrete specimens were cast, one with duct under

the reinforcement and the other specimen with the duct between the reinforcement.

One duct was fully grouted to half the length and the other half was partially grouted.

All the three methods namely radar, UPE and IE have been used for the evaluation of

different parameters. The size of the duct has been determined using GPR and UPE and

compared with the actual.

Comprehensive literature study has been carried out on the radar technique as a non

destructive tool for the evaluation of concrete structures. Not much information is

available on the minimum spacing of reinforcement that can be measured using radar

and also the determination of the second layer of reinforcement and also the

determination and influence of duct. Casting of large number of concrete specimen

requires more time and the profile inside the specimen cannot be shifted. So, in order to

collect more data with various profiles, a simulated specimen was constructed. Using

this specimen, various configurations of reinforcement meshes, with and without ducts,

different size of defects, have been studied in detail.

The need for a holistic approach in the evaluation of concrete structures has been

demonstrated in this study. In addition for the radar technique, the influencing

parameters with respect to the reinforcement and duct have been studied in detail and

guidelines are arrived.

vii

TABLE OF CONTENTS

CONTENTS Page

No.

ACKNOWLEDGEMENTS i

ABSTRACT iii

TABLE OF CONTENTS vi

LIST OF TABLES xii

LIST OF FIGURES xiv

NOTATION xxi

ABBREVATIONS xxii

CHAPTER 1 INTRODUCTION 1

1.1 GENERAL 1

1.2 IMPORTANCE OF NONDESTRUCTIVE TESTING 2

1.3 BASIC METHODS FOR NDT OF CONCRETE STRUCTURES 4

1.3.1 Rebound hammer test 4

1.3.2 Ultrasonic Pulse Velocity (UPV) Test 5

1.3.3 Penetration resistance test 6

1.3.4 Pull-out Test 7

1.3.5 Pull-off Method 7

1.3.6 Break-off test 8

1.3.7 Cover Measurement 8

1.3.8 Core Sampling and Testing 9

1.3.9 Half-cell electrical potential method 9

1.3.10 Resistivity Mapping 9

1.4 ADVANCED NDT METHODS FOR CONCRETE STRCTURES 10

1.4.1 Ground Penetrating Radar (GPR) 10

1.4.2 Impact-Echo Method (IE) 13

1.4.3 Ultrasonic Pulse Echo (UPE) 17

1.4.4 Additional Testing Methods 21

1.5 NEED FOR FURTHER RESEARCH 21

CHAPTER 2 LITERATURE REVIEW 24

2.1 GENERAL 24

2.2 GROUND PENETRAING RADAR (GPR) 24

viii

2.3 Ultrasonic pulse echo technique 31

2.4 Impact Echo method 33

2.5 Summary 39

CHAPTER 3 SCOPE AND OBJECTIVES 40

3.1 GENERAL 40

3.2 MOTIVATION FOR THE PRESENT STUDY 40

3.3 OBJECTIVES AND SCOPE OF THE PRESENT STUDY 41

CHAPTER 4 EXPERIMENTAL INVESTIGATION 42

4.1 GENERAL 42

4.2 ULTRASONIC PULSE VELOCITY METHOD 43

4.3 UNIQUE REINFORCED CONCRETE MULTISTORY SPECIMEN 43

4.3.1 Details of first floor slab 44

4.3.2 Details of second floor slab 44

4.3.3 Evaluation of the Reinforced Concrete Multistory Specimen

using Ultrasonic Pulse Velocity Method 51

4.4 CONCRETE PRISM SPECIMENS- STUDY ON SIZE OF VOIDS

AND INFLUENCE OF REINFORCEMENT 56

4.4.1 Details of the Voids and Reinforcement 57

4.4.2 Evaluation using ultrasonic pulse velocity method 63

4.5 Concrete Blocks With Duct-(TD1 AND TD2)- Study on the Effect of

Reinforcement on the Presence of Duct 77

4.5.1 Concrete specimen TD1 77

4.5.2 Concrete specimen TD2 78

4.5.3 Evaluation with Ultrasonic Pulse Velocity Method 80

4.6 CONCRETE BLOCKS WITH HONEYCOMBS 82

4.6.1 Evaluation with Ultrasonic Pulse Velocity 83

4.7 SUMMARY 84

CHAPTER 5 EXPERIMENTAL STUDIES ON

GROUND PENETRATING RADAR 86

5.1 GENERAL 86

5.2 PRINCIPLE OF GROUND PENETRATING RADAR (GPR) 87

5.3 EXPERIMENTAL PROCEDURE 89

5.3.1 Two dimensional data collection setup 90

ix

5.3.2 Three dimension data collection setup 91

5.3.3 Processing using RADAN Software 91

5.3.4 Data Visualization 92

5.3.5 Position correction (PC) 93

5.3.6 Migration 94

5.4 EVALUATION OF UNIQUE REINFORCED CONCRETE

MULTISTORY SPECIMEN

95

5.4.1 First floor slab 95

5.4.2 Second floor slab 97

5.4.3 Evaluation of Column and Beam 98

5.4.4 Analysis of test results 100

5.5 CONCRETE PRISMS CONTAINING DIFFERENT SIZES OF

VOIDS 100

5.5.1 Evaluation using Radar 100

5.5.2 Evaluation of specimen HC1 101








5.6 Concrete Blocks With Duct-(TD1 AND TD2)- Study on the Effect of

Reinforcement on the Presence of Duct 104

5.6.1 Concrete Specimen TD1 Tested from Top 105

5.6.2 Concrete Specimen TD1 Tested from Bottom Side 106

5.6.3 Concrete Specimen TD2 Tested from Top Side 107

5.6.4 Concrete Specimen TD2 Tested from Bottom Side 108

5.7 Concrete Blocks- Study on the presence of voids/honeycombs 109

5.8 Simulated Specimen for Parametric Study 110

5.8.1 Identification of Reinforcement Bars and its Spacing 112

5.8.1.1 Evaluation and Analysis of Data 113

5.8.2 Identification of Reinforcement Mesh for Minimum Spacing 117

x


5.8.3 Identification of reinforcement mesh with two layers 120


5.8.4 Study on the presence of duct and the influence of

reinforcement 122

5.8.4.1 Evaluation and analysis of data 122

5.9 SUMMARY 124

CHAPTER 6

EXPERIMENTAL STUDIES USING

ULTRASONIC PULSE ECHO

126

6.1 General 126

6.2 ULTRASONIC PULSE ECHO EQUIPMENT 126

6.2.1 FEATURES 127

6.2.1.1 A-scan form 127

6.2.1.2 BAND mode-(B-scan) 128

6.2.1.3 MAP mode 128

6.2.2 Making a Measurement 129

6.3 Ultrasonic Tomograph MIRA System 129

6.3.1 Synthetic aperture focusing technique (SAFT) and SAFT-C 131

6.4 Evaluation of the large scale reinforced concrete specimen. 132

6.4.1 Evaluation with A1220 monolith ultrasonic pulse echo

system 133

6.4.1.1 First floor slab results 134

6.4.1.2 Second floor slab results 135

6.4.2 Testing with MIRA ultrasonic tomograph 136

6.5 Beam Specimens- Study on sizes of voids 139

6.5.1 Beam specimen HC1 ( Voids with no reinforcements on top) 139

6.5.2 Beam specimen HC4 (Voids under 8 mm stirrup) 140

6.5.3 Beam specimen HC 7 (Voids under 16 mm reinforcement) 141

6.6 Concrete Blocks with duct 141

6.7 Concrete blocks with honeycombs 145

6.8 SUMMARY 147

xi

CHAPTER 7

EXPERIMENTAL STUDIES ON IMPACT ECHO

149

7.1 General 149

7.2 Instrumentation 149

7.3 Manual Impact Echo System 149

7.3.1 Data Acquisition and Processing 150

7.3.2 Surface Preparation 151

7.3.3 Material Parameters 151

7.3.4 Determination of P-Wave Speed 152

7.3.5 Data Acquisition 153

7.3.6 Data Processing 154

7.3.7 Data Interpretation 154

7.3.8 Data Visualisation 155

7.4 WHEEL BASED SCANNING TYPE IMPACT ECHO SYSTEM 155

7.5 EVALUATION OF THE UNIQUE REINFORCED CONCRETE

MULTISTORY SPECIMEN 156

7.5.1 Thickness Determination 157

7.5.2 Detection of Defects 159

7.5.3 Determination of Thickness with the Wheel based IE

Scanning 161

7.6 CONCRETE BLOCKS WITH DUCT 163

7.6.1 Determination of the duct (TD1) 163

7.6.2 Concrete specimen (TD2) 166

7.7 SUMMARY 169

CHAPTER 8 RESULTS AND DISCUSSIONS 171

8.1 General 171

8.2 UNIQUE REINFORCED CONCRETE MULTISTORY SPECIMEN 171

8.3 DETERMINATION OF VOIDS IN CONCRETE 173

8.4 DETERMINATION OF DUCT AND THE EFFICIENCY OF

GROUTING IN POST TENSIONED DUCTS 174

8.5 CONCRETE PRISMS WITH REAL HONEYCOMBS 175

xii

8.6 EXPERIMENTAL STUDIES WITH RADAR IN SIMULATED

SPECIMEN- PARAMETRIC STUDY 176

8.7 SUMMARY 176

CHAPTER 9 SUMMARY AND CONCLUSIONS 178

9.1 General 178

9.2 Summary 179

9.3 Conclusions 181

REFERENCES

183

LIST OF PAPERS SUBMITTED ON THE BASIS OF THIS THESIS 188

xiii

LIST OF TABLES

Table

No.

Title Page

4.1 Velocity Criterion for Concrete Quality Grading 43

4.2a Ultrasonic Pulse Velocity Values – Second Floor -Top & Bottom 54

4.2b UPV Values in km/sec at the location of steel box 55

4.2c Ultrasonic Pulse Velocity Values in the location of cracked beam

specimen

55

4.2d Ultrasonic Pulse Velocity Values in the location of Honey combs 55

4.2e Ultrasonic Pulse Velocity Values in the location of PVC pipes 56

4.3a Ultrasonic Pulse Velocity Values for HC-1 (along the width) 65

4.3b Ultrasonic Pulse Velocity Values for HC-1 (Top and Bottom) 65

4.3c Ultrasonic Pulse Velocity Values for HC-1 (along the length) 66


4.4b Ultrasonic Pulse Velocity Values for HC-2 (Top & Bottom) 67















4.9b Ultrasonic Pulse Velocity Values for HC-7(Top & Bottom) 74




xiv


4.11 Materials used for slab specimen TD1 and TD2 80

4.12a Ultrasonic Pulse Velocity Values in km/sec for TD1 (N-S

Direction)

82

4.12b Ultrasonic Pulse Velocity Values in km/sec for TD1 (E-W

Direction)

82

4.12c Ultrasonic Pulse Velocity Values in km/sec for TD2 (N-S

Direction)

82

4.13a Ultrasonic Pulse Velocity Values in km/sec for TD1 (at the centre

line of duct)

82

4.13b Ultrasonic Pulse Velocity Values in km/sec for TD2 (N-S

Direction)

82

4.13c Ultrasonic Pulse Velocity Values in km/sec for TD2 (along the

duct)

82

4.14a Ultrasonic Pulse Velocity Values in km/sec – Speciemn-3A 84

4.14b Ultrasonic Pulse Velocity Values in km/sec – Speciemn-3B 84

5.1 Typical material properties and velocity of propagation 88

5.2 Details of positioning of reinforcement bars in the simulated

specimen

113

5.3 Details of positioning of reinforcement bars in the simulated

Specimen

113

5.4 Details of reinforcement meshes in the simulated specimen 118

5.5 Experimental spacing of bars in the mesh 120

5.6 Details of lateral shift for two layers of mesh 120

5.7 Details of reinforcement mesh and duct location in the simulated

specimen

122

5.8 Details of reinforcement mesh and duct location in the simulated

specimen

122

8.1 Thickness estimation of slabs 172

8.2 Comparison of results obtained with radar and UPE 175

xv

LIST OF FIGURES

Figure No. Title Page

1.1 Principle of radar surveying 11

1.2 Trace (Radargram) 11

1.3 GPR equipment setup 13

1.4 Schematic of an impact echo test 14

1.5 Principle of frequency analysis 15

1.6 Impact echo instrument 17

1.7 Ultrasonic-echo testing for slabs with longitudinal waves 17

1.8

Concrete members and typical recordings for ultrasonic-

echo for (b) sound concrete member (c) void with

direct detection (upper part) and indirect detection (lower

part)

19

1.9 Ultrasonic Pulse Echo instrument - A1220 20

4.1 First floor slab-reinforcement details 46

4.2 Second floor slab-Bottom reinforcement details 47

4.3 Second floor slab-Top reinforcement details 48

4.4a Second floor slab details of the large scale specimen 49

4.4b Different inserts provided in the first floor slab 50

4.5 Unique reinforced concrete multistory specimen 50

4.6 Grid pattern of slab 52

4.7 UPV measurements on the slab 53

4.8 Typical cast concrete speciemen 57

4.9 Concrete Prism HC-1 59








4.17a Grid pattern for HC-1 to HC-8 63

4.17b Grid pattern for HC-1 to HC-8 64

xvi

4.18 Ultrasonic pulse velocity testing on HC2 specimen 64

4.19 Reinforcement details of Concrete Specimen –TD1 77

4.20 Cast concrete specimen with empty duct–TD1 78

4.21 Reinforemcnt and Duct details of Concrete Specimen –

TD2

79

4.22a Bottom Reinforcement in TD2 79

4.22b Top Reinforcement with duct 79

4.23 Cast concrete specimen TD2 with duct pre-stressed

strands

79

4.24 Grid Details for TD1 and TD2 81

4.25a Honeycombs in the cover concrete 83

4.25b View of the cast specimen with honeycombs 83

4.26 Grid lines for Blocks 3A and 3B 84

5.1 Principle of radar surveying 87

5.2 GPR equipment setup 89

5.3 GPR equipment system ready for scanning 90

5.4 Geometry and data collection window-GPR 91

5.5 B-scan image-GPR 93

5.6 C-scan image-GPR 93

5.7 Data after Position correction 94

5.8 Migrated data 94

5.9 Data collection with radar using 1.6 GHz antenna 95

5.10a Reinforcements before and after migration 96

5.10b Reinforcements before and after migration 96

5.11 Reinforcements in first floor slab – 3D 96

5.12 Radargram in sloping portion of first floor slab 97

5.13 C-scan at 45 mm from top face 97

5.14 C-scan at 70 mm from top face 98

5.15 Radargram in the second floor slab showing the presence

of the embedded steel

98

5.16 C-Scan of the column 99

5.17

C-Scan image of the beam 99

xvii

5.18 Cast Speciemen with grid marking for the collection of

radar data

101

5.19a C-scan at 50mm-HC1 101

5.19b C-scan at 60 mm-HC1 101

5.20a C-scan at 60 mm-HC2 102


5.20c C-scan at 150 mm-HC2 102









5.25a C-scan at 50 mmHC-7 104

5.25b C-scan at 90 mmHC-7 104


5.26b C-scan at 120 mmHC-8 104

5.27 Collection of radar data on the specimen TD1 105

5.28 Line scan and wiggle mode of 16mm diameter mesh after

Position Correction-TD1

105

5.29 Line scan and wiggle mode of 16mm diameter mesh after

migration-TD1

105

5.30 C-Scan image of 16mm diameter mesh @150mm in TD1

after migration

106

5.31 C-Scan image of duct at 125 mm from top surface in TD1 106

5.32 Scan image of 2nd layer of reinforcement mesh in TD1 106

5.33 Line scan and wiggle mode duct is placed at 11.30cm

depth from top surface in TD1 after Position correction.

107

5.34 Line scan and wiggle mode duct is placed at 11.48cm

depth from top surface in TD1 after migration.

107

5.35 Scan image of 8 mm mesh @ 150 mm spacing in TD1 107

xviii

5.36 C-Scan image of duct at 120 mm depth from bottom

surface in TD1

107

5.37 Line scan of 16mm diameter mesh TD2 after position

correction

108

5.38 Line scan and wiggle mode of 16mm diameter mesh and

duct of TD2 after migration

108

5.39 C-Scan image of 16mm diameter mesh of TD2 108

5.40 C-Scan image of duct at 9.2 cm depth from top surface in

TD2

108

5.41 Line scan of 8 mm and 6mm diameter mesh and duct in

TD2 after position correction

109

5.42 Line scan of 8 mm and 6mm diameter mesh in TD2 after

position correction

109

5.43 C-Scan image of duct is placed at 15.4cm depth from top

surface in TD2 after migration.

109

5.44 C-Scan image of reinforcement mesh placed at 22.5cm

depth from top surface in TD2 after Migration

109

5.45 Collection of radar data with 1.6 GHz antenna 110

5.46a Radargram for the solid specimen 3A 110

5.46b Radargram for the honeycomb specimen 3A 110

5.47 Simulated specimen setup 111

5.48 Radar data collection for parametric studies 112

5.49 Typical setup of the rods at 30 mm and 20mm (C6) 112

5.50 Line scan for spacing of 70 mm and 50 mm for B1 to B5 114

5.51 Line scan for spacing of 70 mm and 50 mm for B6 to B9 114

5.52 Line scan for spacing of 30 mm and 20 mm for C1 to C3 115



5.55 (a) to (i) C-scan for B1 to B9 116

5.56 (a) to (i) C-scan for C1 toC9 117

5.57 (a) 12 mm diameter mesh at 25 mm spacing (A1) 118

5.57(b)

12 mm diameter mesh at 150 mm spacing (A6) 118

xix

5.58 Line scan for spacing of 25 mm and 125 mm for A1 to

A5

119

5.59 (a) to (f) C-scan for B1 to B6 120

5.60 Typical line scan for two layers (E1) 121

5.61 (a) to (h) C-scan of top and bottom layer E1 to E4 121

5.62 Line scan for different position of duct G1 to G4 123

5.63 (a) to (d) C-scan for G1 to G4 123

5.64 Line scan for different position of duct H1 to H4 123

5.65 (a) to (d) C-scan images for H series specimen H1 to H4 124

6.1 A1220 MONOLITH – UPE equipment 127

6.2 Band Mode (Ultrasonic Pulse Echo) 128

6.3 MAP Mode (Ultrasonic Pulse Echo) 129

6.4 a Ultrasonic Tomograph MIRA System 130

6.4 b View of various dry point contact (DPC) transducers 130

6.5 SAFT-C processing of the signals from each set of DPC

modules

132

6.6 B- Scan image 132

6.7 Grid details of the first and second floor slab 133

6.8 Ultrasonic pulse echo test on second floor slab 134

6.9 B-scan and C-scan images of first floor slab S1 – 200 mm 134

6.10 B-scan and C-scan images of first floor slab S4- 300 mm 135

6.11 B-scan and C-scan images of first floor slab S4 – 400 mm 135

6.12 B-scan and C-scan images 136

6.13 B-scan and C-scan images of slab S1 136

6.14 Testing with MIRA Tomograph on the concrete slab 137

6.15 B-Scan showing the back wall of the slab (150 mm) 137

6.16 B-Scan showing the honeycombs (B) in the concrete slab

(150 mm)

137

6.17 B-Scan showing the reflection of steel plate in the

concrete slab (150 mm)

138

6.18 B-Scan showing the back wall thickness of concrete slab

(250 mm)

138

xx

6.19 B-Scan showing the honeycombs(C) in the concrete slab

(250 mm)

138

6.20 B-Scan showing the reflection of steel box in the

concrete slab (250 mm)

139

6.21 B-scan and C-scan image of HC-1(UPE) 140

6.22 B-scan and C-scan image of HC4 (UPE) 140

6.23 B-scan and C-scan image 75mm void HC8(UPE) 141

6.24a B- Scan obtained from (BAND Mode) – TD1 142

6.24b B- Scan obtained from (BAND Mode) – TD2 142

6.25 C-Scan image of TD1 showing duct 143

6.26 B-scan and C-scan image of TD2 (Partially Grouted) 143

6.27 B-scan and C-scan image of TD2 (Fully Grouted) 144

6.28 B-scans images for TD1 144

6.29 B-scans images for TD2 145

6.30 B-scans from UPE 145

6.31a B-scans and C-scans specimen 3A- Solid Specimen 146

6.31b B-scans and C-scans specimen 3B- Honeycombed

Specimen

147

7.1 Impact Echo System 150

7.2 Test with Impact Echo 153

7.3 Screenshot after testing (IE) 153

7.4 Typical B-scan image (IE) 155

7.5a Wheel based scanning type Impact Echo system 156

7.5b Wheel based impactor and sensor for pick up of signals 156

7.6 Typical frequency spectra at a point in 200 mm thick slab

portion

158

7.7 Typical frequency spectra at a point in 300 mm thick slab

Portion

158

7.8 B Scan Image along a typical grid line 159

7.9 (a) Frequency spectra at the honeycombed portion 160

7.9 (b) Frequency spectra in solid portion 160

7.10 B-scan image along a typical line passing over buried

pipes (along x-direction)

160

xxi

7.11 B-scan image along a line passing over buried pipes and

defects

161

7.12 Thickness plot for the first floor slab 162

7.13 Thickness plot for the second floor slab 162

7.14 Concrete Specimen- TD1 (IE) 163

7.15 Testing with the Impact Echo system (IE) 164

7.16 Thickness plot –reference(IE) 165

7.17(a) Shift in the thickness at the position of duct(IE) 165

7.17(b) Shift in the thickness at the position of duct(IE) 166

7.18a Grouted Side 167

7.18b cast concrete specimen TD2 167

7.19 Thickness plot along the duct 168



7.22 Concrete core showing the imperfection in grouting 169

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LIST OF NOTATIONS

GREEK SYMBOLS

ε Complex permittivity

ε’ Real part of complex permittivity

ε” Imaginary part of complex permittivity

v Propagation velocity of electromagnetic impulse; and

c Speed of light in vacuum (2.99792458 108 m/s).

ENGLISH SYMBOLS

c Known or estimated wave speed

Cp P wave speed through the thickness of the plate

d Calculated thickness / depth position

L Spacing between the transducers

t1 and t2 P-wave arrival times at the first and second transducers

t Measured transit time

T Thickness

V Velocity

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ABBREVIATIONS

DFA - Digitally Focused Array

DPC - Dry Point Contact

EPS - Expanded Polystyrene

GPR - Ground Penetrating Radar

IE - Impact Echo

NDT - Non Destructive Testing

PC - Position Correction

PUNDIT - Portable Ultrasonic Non-Destructive Digital Indicative Tester

PVC - Poly Vinyl Chloride

RCC - Reinforced Cement Concrete

SAFT - Synthetic Aperture Focusing Technique

SAFT-C - Synthetic Aperture Focusing Technique-Combinations

UPE - Ultrasonic Pulse Echo

UPV - Ultrasonic Pulse Velocity

P. SRINIVASANshodhganga.inflibnet.ac.in/bitstream/10603/45474/10/...honeycombs, voids created by the presence of PVC pipes and steel box, etc., has been demonstrated. For the determination

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