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Looking into concrete with stepped-frequency continuous-wave ground-penetrating radar
The document discusses the advancements in stepped-frequency continuous-wave (SFCW) ground-penetrating radar (GPR) technology for inspecting concrete structures, highlighting its ability to overcome the resolution versus depth trade-off common in traditional GPR systems. Key features of SFCW GPR include higher resolution, enhanced signal-to-noise ratios, and effective detection of various targets within concrete. Validation results demonstrate that SFCW GPR, particularly Proceq's GPR Live, consistently outperformed traditional GPR devices in detecting targets, including rebar and voids.
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Looking into concrete with stepped-frequency continuous-wave ground-penetrating radar
- 1. Looking into concretewith 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 2018Looking 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 2018Looking 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 2018Looking 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 2018Looking 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 2018Looking 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 2018Looking 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 2018Looking 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 2018Looking 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 2018Looking 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 2018Looking 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 2018Looking 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 2018Looking 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 2018Looking 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 2018Looking 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 2018Looking 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 2018Looking 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 2018Looking 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 2018Looking 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 2018Looking 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 2018Looking 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 2018Looking 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 2018Looking 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 2018Looking 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 2018Looking 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 2018Looking 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 2018Looking into concrete with stepped-frequency continuous-wave ground-penetrating radar 31 Case 3 Proceq GPR Live All targets detected unambiguously. 3
- 32. © Proceq 2018Looking 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 2018Looking 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 2018Looking 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 2018Looking 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 2018Looking 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 2018Looking into concrete with stepped-frequency continuous-wave ground-penetrating radar 38 Match between reality and various views
- 39. © Proceq 2018Looking into concrete with stepped-frequency continuous-wave ground-penetrating radar 39 Transition point between asphalt and concrete road sections
- 40. © Proceq 2018Looking 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 2018Looking into concrete with stepped-frequency continuous-wave ground-penetrating radar 41 Long floor scan with grade
- 42. © Proceq 2018Looking into concrete with stepped-frequency continuous-wave ground-penetrating radar 42 Thin slab with two aligned rebar layers
- 43. © Proceq 2018Looking into concrete with stepped-frequency continuous-wave ground-penetrating radar 43 Slanted block scan with various targets
- 44. © Proceq 2018Looking 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 2018Looking 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