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NDT Technologies for Pavement Evaluation:FHWA Directions and Initiatives
H. Thomas YuOffice of Asset Management, Pavement, and Construction
Federal Highway Administration
Content
Background Status Future
Background Deployment of innovative technologies is an
important mission of the Office of Pavement Technology Identify needs and opportunities Deploy promising technologies
Focused on available, near market-ready technology
Emphasis area: NDT technologies for pavement evaluation
NDT for Pavement Evaluation
Step-Frequency Ground-PenetratingRadar (SF-GPR)
Ultra-Sonic Testing Device: MIRA
SF-GPR Advantages
Wide detection range (0 to 20+ ft) Full coverage of a lane in 2 passes Continuous calibration Insensitive to external interference
Potential Applications Pavement layer thickness and structure Feature detection (voids, objects) Material property variations
• HMA density variations• In consistencies in PCC mix• Material degradation
Moisture detection Cover depth detection
History of SF-GPR Implementation
2008 – field demonstration on a forensic evaluation
2009 – equipment purchase, detailed evaluation, and validation testing
2010 – development of data analysis algorithms
2011 – refinements, validation, and field demonstrations; equipment upgrade
2012 – equipment upgrade; demonstrations
SF-GPR – scan images
Surface – no distress Layer interface showing inconsistent condition and presence of water
SF-GPR Status Several applications are ready for pilot
implementation Surface layer thickness for construction QA Pavement structure survey Feature detection Material property variations
SF-GPR could be customized for many applications Automation of data processing can be achieved Some expert interpretation will be needed,
depending on the maturity of the application
MIT Scan T2 targets
MIT Scan-T2 thickness vs. SF-GPR
R² = 0.9998
3.5
4.5
5.5
6.5
7.5
8.5
9.5
10.5
11.5
12.5
0 2 4 6 8 10 12
APE
Thic
knes
s Mea
sure
men
t (In
ches
)
MIT Scan Thickness Measurement (Inches)
Error Histogram (APE Measurement – MIT Mean)Day 1, First Lift, APE Test Run 1
σ = 0.04 inch
2σ = 0.07 inch
3σ = 0.11 inch
Meanerror = 0.02 inch1σ-1σ
-2σ-3σ
2σ3σ
-0.15 -0.1 -0.05 0 0.05 0.1 0.150
1
2
3
4
5
6
7
8
9
10
Measurement Error (inches)
APE Analysis DomainsSF-GPR Data in Frequency Domain
Data processing
-1.00E+00
-8.00E -01
-6.00E -01
-4.00E -01
-2.00E -01
0.00E+00
2.00E -01
4.00E -01
6.00E -01
8.00E -01
1.00E+00
0 500 1000 1500 2000 2500 3000
Frequency (MHz)
Am
pli
tud
e
Real
Imaginary
Time Domain Data
Layer plot
Data visualization
Feature detection
Bridge approach slab
T+10
T+30
T+58
T+107
T+127
T+191
T - Time water was added
Begin Collection
Frequency -196
Section 1
Section 2, 1st half
Section 2, 2nd half
HMA relative density
Section 1
Section 2, 1st half
Section 2, 2nd half
With interference filter
HMA relative density
Summary Several applications are well-suited for production
work and are ready for pilot implementation: Surface layer thickness HMA density variations (SHRP2 R06C) Rail-road ballast inspection Pavement structure Feature detection
FHWA Support Demonstrations and participations in pilot
implementations Enhancements of data analysis and visualization tools