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
Outline! Ultrasonic Tomography Overview! Georgia Example! MnROAD!Joint Assessment!Asphalt thickness and compaction! Conclusions/Goals moving forward
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
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 Schickert2003 higher center frequency! higher attenuation lower center frequency! higher distance Schickert, 2002
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, acsys.ru/eng Shevaldykin, 2002
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 45 pairs per measurement
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
Field Application Atlanta Georgia Continuously Reinforced Pavement 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 Ð Atlanta Georgia Continuously Reinforced Pavement 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). 15 m interval measurement points
Field Application Ð Atlanta Georgia CRCP 450 mm
Field Application Ð Atlanta Georgia CRCP
Field Application Ð Atlanta Georgia CRCP
Field Application Ð Atlanta Georgia CRCP: Macro PE vs Core Concrete Cover
Field Application Atlanta Georgia CRCP D e p t h Longitudinal Bars Pavement Depth
Field Application Ð Atlanta Georgia reinforcement D e p t h left bar middle bar Òs hallowest baró right bar
Field Application Ð Atlanta Georgia CRCP: Northbound Lane 3 Concrete Cover
Automated Procedure
Automated Procedure October 20th, 2009 Current Research
Field Application Ð Atlanta Georgia CRCP: Macro PE vs Core Concrete Cover
Field Application Ð Atlanta Georgia CRCP: Northbound Before Filtering Position 2 Threshold 49.2 Circularity 0.80 Size 3000 pixels
Field Application Ð Atlanta Georgia CRCP: Northbound After Filtering Position 2 Threshold 49.2 Circularity 0.80 Size 3000 pixels
Field Application Ð Atlanta Georgia CRCP
Other Applications! Joint deterioration! AC thickness! AC compaction
delamination delamination
MnROAD JPCP Trench
Dowel Deteriorated Concrete Backwall Reflection
Other Applications! Joint deterioration! AC thickness! AC compaction
AC - Thickness!Velocity: 2136 m/s!thickness: 97 mm
AC - Thickness
Other Applications! Joint deterioration! AC thickness! AC compaction
Field Application Atlanta Georgia CRCP 0 3 6 9 Distance from Beginning of Section, m
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
Acknowledgements! Thomas Yu, FHWA! Shongtao Dai, MnDOT Thank You Questions?
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 5 O 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 5 O 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 5 O Seminario International de lngenieria de Pavimentos, 31 de Marzo 2010
MIT Scan 2 5 O 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 5 O Seminario International de lngenieria de Pavimentos, 31 de Marzo 2010
Introduction - Equipment! UK1401-2-probe device for compression wave (p-wave) velocity measurements UK1401 5 O 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 5 O Seminario International de lngenieria de Pavimentos, 31 de Marzo 2010 A1220 Monolith
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 5 O Seminario International de lngenieria de Pavimentos, 31 de Marzo 2010
Intro - P and S Wave Velocity relationship Carino, 2001 5 O 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:! V p is the compression wave velocity! V s is the shear wave velocity! E is the elastic modulus! ", is Poisson s ratio! # is the density By combining V p and V s, 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
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 5 O 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 5 O Seminario International de lngenieria de Pavimentos, 31 de Marzo 2010
Signal Classification Methods Ð Initial Application! Rank 0: Sound Concrete Ð!typical signal prior to testing 5 O Seminario International de lngenieria de Pavimentos, 31 de Marzo 2010
Signal Classification Methods Ð Initial Application! Rank 1: Micro Cracking Ð!Typical signal after 6.5 kips of loading 5 O Seminario International de lngenieria de Pavimentos, 31 de Marzo 2010
Signal Classification Methods Ð Initial Application! Rank 2: Macro Cracking Ð!typical signal after crack formulation 5 O Seminario International de lngenieria de Pavimentos, 31 de Marzo 2010
Signal Classification Methods Ð Initial Application! Rank 3: Failure Ð! typical signal after complete crack formulation and concrete failure 5 O 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 5 O 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 5 O Seminario International de lngenieria de Pavimentos, 31 de Marzo 2010