NDT Technologies for
Pavement Evaluation:
FHWA Directions and Initiatives
H. Thomas Yu
Office 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-Penetrating
Radar (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
APE Thickness Measurement (Inches)
12.5
11.5
10.5
9.5
8.5
R² = 0.9998
7.5
6.5
5.5
4.5
3.5
0
2
4
6
8
10
MIT Scan Thickness Measurement (Inches)
12
Error Histogram (APE Measurement – MIT Mean)
Day 1, First Lift, APE Test Run 1
-3σ
-2σ
-1σ
1σ
2σ
10
3σ
Meanerror = 0.02 inch
9
σ = 0.04 inch
8
7
2σ = 0.07 inch
6
5
3σ = 0.11 inch
4
3
2
1
0
-0.15
-0.1
-0.05
0
0.05
0.1
Measurement Error (inches)
0.15
APE Analysis Domains
SF-GPR Data in Frequency Domain
Data processing
1. 00E +00
8. 00E -01
Amplitude
6. 00E -01
4. 00E -01
2. 00E -01
0. 00E +00
-2. 00E -01
0
500
1000
1500
2000
-4. 00E -01
-6. 00E -01
Real
-8. 00E -01
Im aginary
-1. 00E +00
Frequency (MHz)
Time Domain Data
2500
3000
Layer plot
Data visualization
Feature detection
Bridge approach slab
Frequency -196
T+10
T+30
T+58
T+107
T+127
T+191
Begin Collection
T - Time water was added
HMA relative density
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
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