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

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6

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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