1. February 1, 20051 Analysis of Test Slab Failure Data David R. Brill FAA Airport Technology R&D Branch, AAR-410 William J. Hughes Technical Center, Atlantic City, NJ Airport Pavement Working Group Meeting Sheraton Atlantic City Convention Center Hotel February 2, 2005

2. AAR-410 February 1, 20052 Objectives u Quantify CC2 rigid test item performance and failure using the SCI concept. u Relate to historical rigid full-scale tests (Lockbourne, Sharonville, MWHGL etc.). u Compare with current failure model. u Analyze effects of test variables: u Support type (stabilized base vs. conventional). u 4-wheel vs. 6-wheel. u Traffic on outside lane.

3. AAR-410 February 1, 20053 CC2 Test Item Layout

4. Construction Cycle 2 – Trafficking MRC u MRC trafficking stopped on June 24, 2004 (north side after 12,675 passes and south side after 5,402 passes. u A total of 96 cracks were detected and 20 cores taken. NorthSouth

5. AAR-410 February 1, 20055 Construction Cycle 2: Trafficking Test Item MRG MRG After 31,020 Passes

6. AAR-410 February 1, 20056 MRG After 31,020 Passes

7. AAR-410 February 1, 20057 MRS After 30,996 Passes Construction Cycle 2: Trafficking Test Item MRS

8. AAR-410 February 1, 20058 MRS After 30,996 Passes

9. AAR-410 February 1, 20059 CC2 Test Items - Results u Full-scale traffic testing began on 4/27/04. u Trafficking ended 12/10/04. u Passes completed: u Top-down cracking has not been eliminated, but bottom-up longitudinal cracks have occurred in the lane receiving loading from both lines of tires.

10. AAR-410 February 1, 200510 Performance Monitoring u Visual Distress Surveys. u ASTM D 5340-93 and FAA AC 150/5380-6. u Daily up to 10,000 passes. Weekly after 10,000 passes. u Embedded Sensors. u Responses monitored for early indication of cracking. u Nondestructive Tests. u HWD every 15 wanders (990 passes) up to 10,000 passes. Every 30 wanders after 10,000 passes. u Destructive Testing. u Cores to investigate origin of cracks.

11. AAR-410 February 1, 200511 Structural Condition Index (SCI) u Rollings (1988) u SCI is structural component of rigid PCI. u Only load related distress types are considered (e.g., L/T/D cracks, corner breaks, shattered slab). u SCI is always equal to or higher than PCI for the same pavement feature. u Joint and corner spalling was excluded from the SCI computation for CC2 test items.

12. AAR-410 February 1, 200512 Micro PAVER Computations u Record structural distresses based on visual surveys. u Treat each test item (north side or south side) as a sample unit. u Follow ASTM procedures for counting distresses and assigning severity levels.

13. AAR-410 February 1, 200513 CC2 Test Item Distresses MRS North - Shattered SlabMRG North - Corner Spall MRG South - Longitudinal Crack Intersecting Corner Break MRS North - Long. & Diag. Cracks

14. AAR-410 February 1, 200514 SCI Versus Coverage Analysis u Plot SCI as a function of applied coverages. u P/C ratio is computed from wander pattern. u All slabs in sample unit versus inside traffic lane only. u Obtain linear regression of SCI versus log(C). u Intercept with SCI=100 line yields C O (cov. to 1st crack). u Intercept with SCI=0 line yields C F (cov. to full failure). u New rigid design concerned with coverages to SCI=80. u Lower portions of failure curve (below SCI = 80) are important for overlay designs.

15. AAR-410 February 1, 200515 Test Item MRC - SCI versus Coverages (All Distresses)

16. AAR-410 February 1, 200516 Test Item MRC - SCI versus Coverages (Center Traffic Lane Distresses Only)

17. AAR-410 February 1, 200517 Test Item MRS - SCI versus Coverage (Center Traffic Lane Distresses Only)

18. AAR-410 February 1, 200518 Test Item MRG - SCI versus Coverage (Center Traffic Lane Distresses Only) SCI = -246.96 log(C) + 935.11 R 2 = 0.9647 SCI = -247.03 log(C) + 941.57 R 2 = 0.9636

19. AAR-410 February 1, 200519 CC2 Test Strip - SCI versus Coverage (S Slab Distresses Only) S SLABSC SLABS

20. AAR-410 February 1, 200520 Summary of SCI vs. Coverage

21. AAR-410 February 1, 200521 Regression Data for SCI vs. Log of Coverages (preliminary)

22. AAR-410 February 1, 200522 Design Factor vs. Coverages u Design Factor (DF) = ratio of concrete flexural strength to maximum calculated bending stress. u LEDFAA model based on Rollings (1988) regression: u DF = 0.5234 + 0.3920 log (C O ) coverages to onset of cracking u DF = 0.2967 + 0.3881 log (C F ) coverages to full failure (SCI 0) u Recompute design factors for all test items using FEDFAA (3D-FEM) edge stress. u Evaluate parameters including 7 new NAPTF data points. u Preliminary analysis - design factors subject to change as we continue to characterize the material properties.

23. AAR-410 February 1, 200523 Recalculate Design Factors (Historic Full-Scale Test Data) Original Regression Recalculated Using FEDFAA Edge Stress

24. AAR-410 February 1, 200524 Design Factor vs. Coverages (Coverages to Complete Failure, SCI=0)

25. AAR-410 February 1, 200525 Design Factor vs. Coverages (Coverages to Onset of Failure, SCI=100 - )

26. AAR-410 February 1, 200526 Current Efforts u Finalize material characterization (e.g., concrete strength, subgrade properties) for design factor computation. u Finalize “best fit” parameters for FAARFIELD rigid failure model from full-scale test data. u Re-evaluate current base stiffness compensation model considering: u full-scale test results showing straight-line trend. u improved ability of 3D-FEM model to give accurate stresses for stabilized base structures.

27. AAR-410 February 1, 200527 Questions?