1. 1 Field validation of constructed sub-grade and pavement John S. Popovics Jeffery Roesler Marshall Thompson David Lange Yi-Shi Liu John Ramirez Department of Civil & Environmental Engineering January 11, 2007

2. 2 Project Objectives The output data from the sensors will be used to infer long-term stress and movement of the slab owing to temperature and moisture gradients. Those responses will be used as input for other OMP research projects. The NDT findings will be used to develop new test methods that provide more appropriate and effective performance at the OMP site. Obtain response data and non-destructive test (NDT) test results from a test structure that replicates the nominal design to be used in the O’Hare modernization program.

3. 3 Instrumented test slab cast June 22 2006 10 inch pcc slab Saw-cut joints 16 inch dense compacted AC base

4. 4 Concrete pavement instrumentation Relative humidity (RH) and temperature (at a range of depths though the slab) Slab lift-off (at slab corners) Joint opening Three types of sensors are embedded in the concrete slab: On-site battery-powered data logger collects data

5. 5 Sensor layout (plan view) Data collected continuously from instrumented concrete slab since casting Only 4 lift-off gages survived casting Un-bonded, dowelled (Ub/D) Bonded, Un-dowelled (B/Ud)

6. 6 Joint opening strongly affected by dowelling; inter-layer bond condition has little or no effect. Un-dowelled Dowelled

7. 7 Joint opening related to temperature, as illustrated in the un-dowelled, un-bonded case Joint opening at ‘A’ Temperature (all sensors)

8. 8 Internal relative humidity shows general decrease over time, with relatively little daily fluctuation surface 7” depth 1/2” depth

9. 9 Site photos verify joint opening data: increased cracking at un-dowelled joints Ub/Ud B/Ud Ub/D B/D

10. 10 Slab lift-off strongly affected by dowelling Ub/Ud Ub/D

11. 11 Slab lift off also affected by interface bond at un-dowelled joint Ub/Ud B/Ud

12. 12 Site photos verify slab lift-off data: little or no interface cracking at bonded joints Lateral edge views of pcc/asphalt interface Ub/Ud case B/Ud case NDT (impact-echo) tests suggest no significant dis-bond throughout “bonded” region

13. 13 Sample core from bonded region demonstrates some physical bond between pcc and ac interface asphalt residue

14. 14 Work to date Conclusions Useful pavement response (to temperature and moisture variation) data continue to be collected. Doweling affects joint opening behavior. Doweling and pcc/ac interface bond condition affect slab (corner) lift off.

15. 15 Future work – pavement sensing  Continue sensing and data collection in trial slab to monitor longer term environmental effects, and share data with other OMP projects. Continue to evaluate observed trends.  Incorporate sensors (similar layout) in actual O’Hare slab cast in 2008 (R/W 9L section?); lift off sensor design must be improved.  Model ATREL slab using finite element method to confirm observations about joint opening and slab lift-off.

16. 16 FEM model of ATREL pavement 3-D model configuration Example deformation from moisture gradient

17. 17 Future work - NDE Evaluate new and existing NDT methods for estimation of layer properties and thickness for O’Hare pavement: standard impact-echo, modified impact-echo, SASW, MASW, GPR, etc.. Tests methods evaluated at ATREL, ultimately applied at O’Hare. Continue to monitor interface bond condition at pavement test site using impact-echo.