nondestructive evaluation of pavements – ultrasonic tomography
TRANSCRIPT
Nondestructive Evaluation of Pavements Ð Ultrasonic Tomography
Kyle Hoegh, Graduate Student Dr. Lev Khazanovich, Associate Professor Civil Engineering Department University of Minnesota Ð Twin Cities
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Outline
•!Ultrasonic Tomography Overview •!Georgia Example •!MnROAD
–!Joint Assessment –!Asphalt thickness and compaction
•!Conclusions/Goals moving forward
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Ultrasonic Methods: Pros and Cons •! Advantages
–! Multiple applications •! Thickness determination •! Inclusion locations •! Flaw detection
–! Real time initial analysis
•! Disadvantages –! Requires proper ground contact to achieve necessary penetration
depths –! Cannot take measurements at highway speeds –! Requires significant efforts for large scale application
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Introduction – Propagation Material
•! Effect of the concrete medium on measuring thickness or detecting inclusions or flaws.
–! No influence if isotropic, non-dispersive, and non-dissipative –! However, concrete is heterogeneous –! Wave loses energy depending on the relationship between the
scatterer and wavelength •! higher center frequency ! higher attenuation •! lower center frequency ! higher distance
Schickert, 2002
Schickert2003
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Introduction - Equipment •! Dry Point Contact (DPC) Low
Frequency Transducers –! Manufactured by Acoustic Control
Systems, Ltd, Moscow, Russia –! Do not require surface preparation –! Touch and measure devices with high
repeatability –! The transducers act on the test object
surface with oscillating piezoelectric elements for wave production and signal receivers •! out of phase for s-wave production •! in phase for p-wave production
Acoustic Control Systems, http://acsys.ru/eng
Shevaldykin, 2002
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New Ultrasonic Tomography Device •! Recently acquired a 40-probe low frequency
shear wave (s-wave) ultrasonic pulse-echo device for thickness and flaw detection in concrete Ð ! self-calibrating
MIRA: Ultrasonic Low
Frequency Tomograph
self-calibrating
45 pairs per measurement
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Imaging / Signal Interpretation •! Signal Interpretation
Ð ! Detect scatterer by changes in reflection intensity (color coded Ð blue to red)
Example: Mira B-scan Depth Measurement
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Measurements of pavement thickness and longitudinal rebar concrete cover for project suspected to have large variations from the specs (about 3 miles of testing in 50 ft intervals).
Field Application – Atlanta Georgia Continuously Reinforced Pavement
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Measurements of CRCP pavement thickness and longitudinal rebar concrete cover for project suspected to have large variations from the specs (about 5 km of testing in 15 meter intervals).
Field Application Ð Atlanta Georgia Continuously Reinforced Pavement
15 m interval measurement points
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Field Application Ð Atlanta Georgia CRCP
450 mm
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Field Application Ð Atlanta Georgia CRCP
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Field Application Ð Atlanta Georgia CRCP
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Field Application Ð Atlanta Georgia CRCP: Macro PE vs Core Concrete Cover
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Field Application – Atlanta Georgia CRCP
Longitudinal Bars
D e p t h
Pavement Depth
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Field Application Ð Atlanta Georgia reinforcement
left bar middle bar Òs hallowest barÓ
right bar
D e p t h
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Field Application Ð Atlanta Georgia CRCP: Northbound Lane 3 Concrete Cover Cover
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Automated Procedure
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Automated Procedure
October 20th, 2009 Current Research
Field Application Ð Atlanta Georgia CRCP: Macro PE vs Core Concrete Cover
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Field Application Ð Atlanta Georgia CRCP: Northbound Before Filtering
Position 2
Threshold 49.2
Circularity 0.80
Size 3000 pixels
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Field Application Ð Atlanta Georgia CRCP: Northbound After Filtering
Position 2
Threshold 49.2
Circularity 0.80
Size 3000 pixels
Threshold
Circularity
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Field Application Ð Atlanta Georgia CRCP
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Other Applications •! Joint deterioration •!AC thickness •!AC compaction
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delamination delamination
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MnROAD JPCP Trench
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Dowel
Backwall Reflection
Deteriorated Concrete
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Other Applications •! Joint deterioration •!AC thickness •!AC compaction
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AC - Thickness
•!Velocity: 2136 m/s
•!Thickness: 97 mm
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AC - Thickness
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Other Applications •! Joint deterioration •!AC thickness •!AC compaction
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Field Application – Atlanta Georgia CRCP
Distance from Beginning of Section, m
3 6 9 0
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Conclusions
•!Ultrasonic tomography is a promising technology for pavement condition assessment and QA/QC applications •!Data interpretation is still time
consuming for most cases and requires significant expertise •!University of MN is currently
working to improve the accuracy and efficiency of the data analysis
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Acknowledgements
•! Thomas Yu, FHWA •! Shongtao Dai, MnDOT
Thank You Questions?
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Techniques
•! Individual methods –! Visual inspection –! Dynamic Cone Penetrometer –! Falling Weight Deflectometer –! Magnetic Methods –! Ground Penetrating Radar –! Infrared Thermography –! Passive acoustic methods such as Acoustic emission (AE) –! Active mechanical sounding
•! Chain dragging •! impact echo
–! Ultrasonic Methods
•! Data fusion
5O Seminario International de lngenieria de Pavimentos, 31 de Marzo 2010
Techniques
•! Individual methods –! Visual inspection –! Dynamic Cone Penetrometer –! Falling Weight Deflectometer
–!Magnetic Methods –! Ground Penetrating Radar –! Infrared Thermography –! Passive acoustic methods such as Acoustic emission (AE) –! Active mechanical sounding
•! Chain dragging •! impact echo
–! Ultrasonic Methods •! Data fusion
5O Seminario International de lngenieria de Pavimentos, 31 de Marzo 2010
Magnetic Methods: Pros and Cons •! Advantages
–! Not affected by heterogeneous nature of PCC or asphalt –! Extremely precise location
•! Disadvantages –! Requires inclusion geometry input –! Cannot provide flaw analysis –! Complicated reinforcement is cannot be handled
5O Seminario International de lngenieria de Pavimentos, 31 de Marzo 2010
MIT Scan 2
5O Seminario International de lngenieria de Pavimentos, 31 de Marzo 2010
Techniques
•! Individual methods –! Visual inspection –! Dynamic Cone Penetrometer –! Falling Weight Deflectometer –! Magnetic Methods –! Ground Penetrating Radar –! Infrared Thermography –! Passive acoustic methods such as acoustic emission (AE) –! Active mechanical sounding
•! Chain dragging •! impact echo
–!Ultrasonic Methods •! Data fusion
5O Seminario International de lngenieria de Pavimentos, 31 de Marzo 2010
Introduction - Equipment
•! UK1401- 2-probe device for compression wave (p-wave) velocity measurements
UK1401 5O Seminario International de lngenieria de Pavimentos, 31 de Marzo 2010
Introduction - Equipment •! A1220 Monolith– 24-probe low frequency shear
wave (s-wave) ultrasonic pulse-echo device for thickness and flaw detection in concrete –! Requires s-wave velocity input
A1220 Monolith 5O Seminario International de lngenieria de Pavimentos, 31 de Marzo 2010
Introduction - Test Procedure
•! Use the UK1401 to measure the compression wave (p-wave) velocity of the test area
•! Plug the shear wave velocity (s-wave) into the A1220 Monolith , based on the measured p-wave velocity
•! Use the A1220 Monolith to measure thickness, locate inclusions, or detect flaws in the concrete locate inclusions, or detect flaws in the concrete
5O Seminario International de lngenieria de Pavimentos, 31 de Marzo 2010
•! Assuming an isotropic, elastic solid, the compression (p-wave) and shear (s-wave) velocities are defined: –! Vp is the compression wave
velocity –! Vs is the shear wave velocity –! E is the elastic modulus –! ", is Poisson’s ratio –! # is the density
•! By combining Vp and Vs, and using arithmetic to simplify, the ratio between the speed of the longitudinal and shear waves is found to be dependant only on Poisson’s ratio
•! Assuming the value of Poisson’s ratio in the concrete is 0.2, shear and compression wave velocities relationship can be estimated
Intro - P and S Wave Velocity relationship
Carino, 2001 5O Seminario International de lngenieria de Pavimentos, 31 de Marzo 2010
Imaging / Signal Interpretation •! Signal Interpretation
Ð ! Detect scattering center location by maximum value of the envelope
Ð ! Example signal interpretation of a round metal dowel embedded in an 8 in. thick concrete beam
Example A-Scan: Dowel location and Depth measurement
5O Seminario International de lngenieria de Pavimentos, 31 de Marzo 2010
Signal Classification Methods Ð Initial Application • A shear load was applied to dowels
embedded in an 8 in. beam •! The dowel was pulled until failure with shear
force and relative dowel displacement recorded
•! Pulse-echo measurements were made to assess the damage to the concrete around the dowel:
Ð ! Before the dowel was pulled in shear Ð ! After the dowel was pulled in shear up to 6.5
kips, Ð ! After the dowel was pulled in shear until macro
cracking was visible at the face of the beam. Ð ! After the dowel was pulled in shear until failure
5O Seminario International de lngenieria de Pavimentos, 31 de Marzo 2010
•! Rank 0: Sound Concrete Ð ! typical signal prior to testing
Signal Classification Methods Ð Initial Application
5O Seminario International de lngenieria de Pavimentos, 31 de Marzo 2010
•! Rank 1: Micro Cracking Ð !Typical signal after 6.5
kips of loading
Signal Classification Methods Ð Initial Application
5O Seminario International de lngenieria de Pavimentos, 31 de Marzo 2010
•! Rank 2: Macro Cracking Ð ! typical signal after crack
formulation
Signal Classification Methods Ð Initial Application
5O Seminario International de lngenieria de Pavimentos, 31 de Marzo 2010
•! Rank 3: Failure Ð ! typical signal after complete
crack formulation and concrete failure
Signal Classification Methods Ð Initial Application
5O Seminario International de lngenieria de Pavimentos, 31 de Marzo 2010
Application Ð Rigid Pavement Flaw Detection
Representative measurements of a I35W joint marked for full depth repair
5O Seminario International de lngenieria de Pavimentos, 31 de Marzo 2010
Conclusions •!Useful technique for evaluating
concrete pavement thickness and concrete cover in CRCP –! Development of an automated data
analysis system dramatically increases efficiency
5O Seminario International de lngenieria de Pavimentos, 31 de Marzo 2010