Nondestructive Evaluation of Pavements – Ultrasonic Tomography

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

http://pavementndt.weebly.com

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 •! higher center frequency ! higher attenuation •! lower center frequency ! higher distance

Schickert, 2002

Schickert2003


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


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


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


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


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


Field Application Ð Atlanta Georgia CRCP

450 mm






Field Application Ð Atlanta Georgia CRCP: Macro PE vs Core Concrete Cover


Field Application – Atlanta Georgia CRCP

Longitudinal Bars

D e p t h

Pavement Depth


Field Application Ð Atlanta Georgia reinforcement

left bar middle bar Òs hallowest barÓ

right bar

D e p t h


Field Application Ð Atlanta Georgia CRCP: Northbound Lane 3 Concrete Cover 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

Threshold

Circularity




Other Applications •! Joint deterioration •!AC thickness •!AC compaction


delamination delamination


MnROAD JPCP Trench


Dowel

Backwall Reflection

Deteriorated Concrete




AC - Thickness

•!Velocity: 2136 m/s

•!Thickness: 97 mm


AC - Thickness




Field Application – Atlanta Georgia CRCP

Distance from Beginning of Section, m

3 6 9 0


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

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


–! Ultrasonic Methods •! Data fusion


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


MIT Scan 2


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


–!Ultrasonic Methods •! Data fusion


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


•! 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


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


•! Rank 0: Sound Concrete Ð ! typical signal prior to testing

Signal Classification Methods Ð Initial Application


•! Rank 1: Micro Cracking Ð !Typical signal after 6.5

kips of loading



•! Rank 2: Macro Cracking Ð ! typical signal after crack

formulation



•! Rank 3: Failure Ð ! typical signal after complete

crack formulation and concrete failure



Application Ð Rigid Pavement Flaw Detection

Representative measurements of a I35W joint marked for full depth repair


Conclusions •!Useful technique for evaluating

concrete pavement thickness and concrete cover in CRCP –! Development of an automated data

analysis system dramatically increases efficiency


Date post:	04-Jan-2017
Category:	Documents
Upload:	buikhuong
View:	227 times
Download:	3 times

Nondestructive Evaluation of Pavements – Ultrasonic Tomography

Documents