1. NDT Technologies for Pavement Evaluation: FHWA Directions and Initiatives H. Thomas Yu Office of Asset Management, Pavement, and Construction Federal Highway Administration

2. Content  Background  Status  Future

3. 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

4. NDT for Pavement Evaluation Step-Frequency Ground-Penetrating Radar (SF-GPR) Ultra-Sonic Testing Device: MIRA

5. 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

6. 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

7. SF-GPR – scan images Surface – no distressLayer interface showing inconsistent condition and presence of water

8. 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

9. MIT Scan T2 targets

10. MIT Scan-T2 thickness vs. SF-GPR

11. 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 Mean error = 0.02 inch 1σ1σ-1σ -2σ -3σ 2σ2σ 3σ3σ

12. APE Analysis Domains SF-GPR Data in Frequency Domain

13. Data processing Time Domain Data

14. Layer plot

15. Data visualization

16. Feature detection

17. Bridge approach slab

18. T+10 T+30 T+58 T+107 T+127 T+191 T - Time water was added Begin Collection Frequency -196

19. Section 1 Section 2, 1 st half Section 2, 2 nd half HMA relative density

20. Section 1 Section 2, 1 st half Section 2, 2 nd half With interference filter HMA relative density

21. 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