Presentation by Isaak Tsalicoglou, Head of Product Management of Proceq, at the UK Concrete Show 2018 in Birmingham. 1) Overview of traditional ground-penetrating radar (GPR) and the key trade-off between penetration depth and target resolution. 2) Stepped-frequency continuous-wave (SFCW) GPR and its first-ever implementation in a handheld structural-concrete scanning device, Proceq GPR Live. 3) Experimental setup of comparison between Proceq GPR Live and two conventional pulsed GPRs; validation of superior performance of SFCW in terms of data quality, penetration depth, target resolution. 4) Real-world examples of looking into concrete: various data processing views of concrete slab data for rebar location, transition between asphalt and concrete road sections, reinforced pillar with and without steel-reinforced concrete (SFRC), scan of long floor with grade, scan of thin concrete slab with two aligned layers of thin rebar, slanted concrete block with various metallic and non-metallic targets (rebars, ducts), 50%-downscaled neigboring reinforced walls and SFCW GPR jumping the air gap between them. 5) Observation and conclusions.

1. Looking into concrete with stepped-
frequency continuous-wave ground-
penetrating radar
The UK Concrete Show 2018
Birmingham – March 22, 2018
Isaak Tsalicoglou – Head of Product Management
Proceq SA, Switzerland
© Proceq 2018 1

2. 1
Overview
Traditional ground-penetrating radar (“GPR”) and the key trade-off
Stepped-frequency continuous-wave ("SFCW") GPR
Experimental setup and validation
Real-world examples
© Proceq 2018 Looking into concrete with stepped-frequency continuous-wave ground-penetrating radar 2
2
3
4
Observations and conclusions5

3. 1
Overview
Traditional ground-penetrating radar (“GPR”) and the key trade-off
Stepped-frequency continuous-wave ("SFCW") GPR
Experimental setup and validation
© Proceq 2018 Looking into concrete with stepped-frequency continuous-wave ground-penetrating radar 3
2
3
Real-world examples4
Observations and conclusions5

4. © Proceq 2018 Looking into concrete with stepped-frequency continuous-wave ground-penetrating radar 4
As-built
verification
Integrity
assessment
Hit prevention
(e.g. coring)
Ground-penetrating radar (GPR) is used for the
reliable detection of targets
• Targets: features, flaws
• In structural concrete:
 Metallic reinforcements
 Post-tensioning ducts
 Plastic pipes
 Air voids
 Object boundaries

5. © Proceq 2018 Looking into concrete with stepped-frequency continuous-wave ground-penetrating radar 5
The “dielectric contrast” at boundaries
determines how much energy is reflected
Concrete 2nd material
Reflection of a traveling wave:
• At a boundary (e.g., concrete-air)
• At an object surface (e.g., rebar)
• R is the percentage of energy that is reflected
• ε is the relative dielectric permittivity
 ε1: concrete
 ε2: second material
𝑅 =
𝜀1 − 𝜀2
𝜀1 + 𝜀2

6. © Proceq 2018 Looking into concrete with stepped-frequency continuous-wave ground-penetrating radar 6
GPR signals pass through a concrete-air boundary.
GPR signals are totally reflected at a concrete-steel boundary.
Quick calculations demonstrate what kind of
reflections we should expect
Interface ε1 ε2
Concrete-air 5 1 38%
Concrete-
steel
5 ∞ -100%
𝑅 =
𝜀1 − 𝜀2
𝜀1 + 𝜀2
Material
Relative dielectric
permittivity ε
Air 1
Concrete (dry) 3 – 7
Concrete (wet) 7 - 14
Steel ∞

7. © Proceq 2018 Looking into concrete with stepped-frequency continuous-wave ground-penetrating radar 7
GPR devices measure the strength and round-
trip travel time of reflections within concrete
Depth
Time
“hyperbola”
“Time of flight method”

8. © Proceq 2018 Looking into concrete with stepped-frequency continuous-wave ground-penetrating radar 8
Estimated locations and depths of targets are
represented in a B-scan
Non-migrated view Migrated view
Views shown and used real-time / live during the measurement

9. © Proceq 2018 Looking into concrete with stepped-frequency continuous-wave ground-penetrating radar 9
Your choice of traditional pulsed GPR device
locks you into a traditional trade-off
Center
frequency
Adverse signal
effects
Penetration
depth
Sensitivity
to contrast
Resolution

10. © Proceq 2018 Looking into concrete with stepped-frequency continuous-wave ground-penetrating radar 10
All traditional pulsed GPR devices suffer from the
resolution-vs.-depth trade-off
Detectable objectssmall large
Ultra wideband technologyPenetrationdepth
070cm
2.6 GHz 2.0 GHz 1.6 GHz 1.0 GHz
Frequency

11. 1
Overview
Traditional ground-penetrating Radar (“GPR”) and the key trade-off
Stepped-frequency continuous-wave ("SFCW") GPR
Experimental setup and validation
© Proceq 2018 Looking into concrete with stepped-frequency continuous-wave ground-penetrating radar 11
2
3
Real-world examples4
Observations and conclusions5

12. © Proceq 2018 Looking into concrete with stepped-frequency continuous-wave ground-penetrating radar 12
Stepped-frequency continuous wave (SFCW)
GPR is a “synthesized radar” technology
Image source: “Ground Penetrating Radar”, 2nd ed., edited by David J. Daniels
• Radiates a sequence of N
frequencies (“steps”)
• RX / acquisition time per
frequency step
• Data gathering in the
frequency domain
• Minimal post-processing
/ filtering required
• Much lower noise than
pulsed GPR

13. © Proceq 2018 Looking into concrete with stepped-frequency continuous-wave ground-penetrating radar 13
SFCW subsystem
SFCW GPR by Proceq resolves the traditional
trade-off between resolution and depth
• Ultrawideband range of
modulated frequencies
(nominal 0.2 … 4.0 GHz)
• Multiple (triple-digit)
frequency steps
Optimized electronics design
• Faster real-time inverse
Fourier transforms
• Maximum signal
acquisition time > 2x
• High signal-to-noise ratio
+ =

14. © Proceq 2018 Looking into concrete with stepped-frequency continuous-wave ground-penetrating radar 14
The choice of GPR antenna center frequency
becomes a moot point
“Looking into
concrete”
with a single
GPR device
Detectable objectssmall large
Ultra wideband technology
Penetrationdepth
070cm
2.6 GHz 2.0 GHz 1.6 GHz 1.0 GHz
Frequency
4.0 GHz 0.2 GHz
Combine all
frequency responses
“All the frequencies you’ll ever need”

15. © Proceq 2018 Looking into concrete with stepped-frequency continuous-wave ground-penetrating radar 15
Wireless probe and cloud connectivity solve
other chronic pain points of GPR use-cases
Share
SEGY
JPEG
User’s account on
Proceq Live
(unlimited storage)
Collaboration
Cloud storage
Proceq GPR Live Basic
Proceq GPR Live Pro
and Unlimited

16. 1
Overview
Traditional ground-penetrating Radar (“GPR”) and the key trade-off
Stepped-frequency continuous-wave ("SFCW") GPR
Experimental setup and validation
© Proceq 2018 Looking into concrete with stepped-frequency continuous-wave ground-penetrating radar 16
2
3
Real-world examples4
Observations and conclusions5

17. © Proceq 2018 Looking into concrete with stepped-frequency continuous-wave ground-penetrating radar 17
Validation of SFCW GPR involved systematic
testing with a clear, objective process
Concrete block design GPR scanning
Data export
(if available)
Data post-
processing
SEGY

18. © Proceq 2018 Looking into concrete with stepped-frequency continuous-wave ground-penetrating radar 18
Four different concrete blocks were designed to
represent realistic configurations
1 2
3 4

19. © Proceq 2018 Looking into concrete with stepped-frequency continuous-wave ground-penetrating radar 19
Hilti PS 1000
GSSI StructureScan
Mini XT
Proceq GPR Live
GPR technology Pulsed Pulsed SFCW
Nominal frequency 2.0 GHz 2.7 GHz 0.2 … 4.0 GHz
Acquisition time 6 ns 9 ns 20 ns
Raw data export  ✓ ✓
Data post-processing Hilti PROFIS Detection GPR-SLICE GPR-SLICE
The two traditional GPR devices are currently
seen as state-of-the-art

20. © Proceq 2018 Looking into concrete with stepped-frequency continuous-wave ground-penetrating radar 20
Case 1
• Five Ø 16 mm rebars
• Flat back wall at 60 cm
1

21. © Proceq 2018 Looking into concrete with stepped-frequency continuous-wave ground-penetrating radar 21
Case 1
Hilti PS-1000
All rebars detected; however, the back wall is out of range.
1

22. © Proceq 2018 Looking into concrete with stepped-frequency continuous-wave ground-penetrating radar 22
Case 1
GSSI StructureScan Mini XT
All rebars detected; however, the back wall is out of range.
1

23. © Proceq 2018 Looking into concrete with stepped-frequency continuous-wave ground-penetrating radar 23
Case 1
Proceq GPR Live
All rebars and the back wall detected.
1

24. © Proceq 2018 Looking into concrete with stepped-frequency continuous-wave ground-penetrating radar 24
Case 2
• No rebars
• Void 150 mm × 70 mm
• V-shaped back wall
2

25. © Proceq 2018 Looking into concrete with stepped-frequency continuous-wave ground-penetrating radar 25
Case 2
Hilti PS-1000
Void detected with spurious noise; back wall undetected.
2

26. © Proceq 2018 Looking into concrete with stepped-frequency continuous-wave ground-penetrating radar 26
Case 2
GSSI StructureScan Mini XT
Void detected, but most of the back wall remains out of range.
2

27. © Proceq 2018 Looking into concrete with stepped-frequency continuous-wave ground-penetrating radar 27
Case 2
Proceq GPR Live
All targets detected without any spurious noise.
2

28. © Proceq 2018 Looking into concrete with stepped-frequency continuous-wave ground-penetrating radar 28
Case 3
• Ø 16 mm rebar mesh
120 mm × 120 mm
• Void 150 mm × 70 mm
• V-shaped back wall
3

29. © Proceq 2018 Looking into concrete with stepped-frequency continuous-wave ground-penetrating radar 29
Case 3
Hilti PS-1000
Only the shallow rebar mesh was detected.
3

30. © Proceq 2018 Looking into concrete with stepped-frequency continuous-wave ground-penetrating radar 30
Case 3
GSSI StructureScan Mini XT
Beyond the rebar mesh, inexistent targets were falsely detected.
3

31. © Proceq 2018 Looking into concrete with stepped-frequency continuous-wave ground-penetrating radar 31
Case 3
Proceq GPR Live
All targets detected unambiguously.
3

32. © Proceq 2018 Looking into concrete with stepped-frequency continuous-wave ground-penetrating radar 32
Case 4
• Two mats of reinforcement
Ø 12 mm rebar mesh
150 mm × 150 mm
• Void Ø 120 mm
• PT duct
• Flat back wall at 50 cm
4

33. © Proceq 2018 Looking into concrete with stepped-frequency continuous-wave ground-penetrating radar 33
Case 4
Hilti PS-1000
Fails to reach the back wall and its rebar mesh, and to detect the void.
4

34. © Proceq 2018 Looking into concrete with stepped-frequency continuous-wave ground-penetrating radar 34
Case 4
GSSI StructureScan Mini XT
Covers a larger depth than the Hilti PS-1000, but ultimately with similar results.
4

35. © Proceq 2018 Looking into concrete with stepped-frequency continuous-wave ground-penetrating radar 35
Case 4
Proceq GPR Live
All targets detected, including the deep rebar mesh and the back wall.
4

36. © Proceq 2018 Looking into concrete with stepped-frequency continuous-wave ground-penetrating radar 36
Case 4 (extended)
Proceq GPR Live
First layer rebar
Duct
Defect
Back wall
Second layer rebar
Hidden area

37. 1
Overview
Traditional ground-penetrating Radar (“GPR”) and the key trade-off
Stepped-frequency continuous-wave ("SFCW") GPR
Experimental setup and validation
© Proceq 2018 Looking into concrete with stepped-frequency continuous-wave ground-penetrating radar 37
2
3
Real-world examples4
Observations and conclusions5

38. © Proceq 2018 Looking into concrete with stepped-frequency continuous-wave ground-penetrating radar 38
Match between reality and various views

39. © Proceq 2018 Looking into concrete with stepped-frequency continuous-wave ground-penetrating radar 39
Transition point between asphalt and concrete
road sections

40. © Proceq 2018 Looking into concrete with stepped-frequency continuous-wave ground-penetrating radar 40
Reinforced pillar with and without steel-fiber
reinforced concrete (“SFRC”)
No SFRC
SFRC

41. © Proceq 2018 Looking into concrete with stepped-frequency continuous-wave ground-penetrating radar 41
Long floor scan with grade

42. © Proceq 2018 Looking into concrete with stepped-frequency continuous-wave ground-penetrating radar 42
Thin slab with two aligned rebar layers

43. © Proceq 2018 Looking into concrete with stepped-frequency continuous-wave ground-penetrating radar 43
Slanted block scan with various targets

44. © Proceq 2018 Looking into concrete with stepped-frequency continuous-wave ground-penetrating radar 44
Two neighboring reinforced walls scaled to 50%

45. 1
Overview
Traditional ground-penetrating Radar (“GPR”) and the key trade-off
Stepped-frequency continuous-wave ("SFCW") GPR
Experimental setup and validation
© Proceq 2018 Looking into concrete with stepped-frequency continuous-wave ground-penetrating radar 45
2
3
Real-world examples4
Observations and conclusions5

46. © Proceq 2018 Looking into concrete with stepped-frequency continuous-wave ground-penetrating radar 46
Detection
capability
Traditional pulsed GPR devices SFCW GPR (Proceq GPR Live)
Penetration
depth
Shallow targets ✓ ✓
Deeper targets  ✓
Resolution,
accuracy, and
clarity
Weak reflectors  ✓
Spurious noise ✓ 
False positives ✓ 
SFCW GPR represents a major breakthrough in structural concrete inspection.
SFCW technology has proven to effectively
resolve the traditional GPR trade-off