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Some Key Findings from NAPTF Testing of Unbonded PCC Overlays

Some Key Findings from NAPTF Testing of Unbonded PCC Overlays. IPRF Project 04-02: Improved Overlay Design Parameters for Concrete Airfield Pavements —The Baseline Experiment. IPRF Project 06-03: Evaluation of Design Parameters for Rigid Overlays —SCI Validation Study. Overview.

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Some Key Findings from NAPTF Testing of Unbonded PCC Overlays

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  1. Some Key Findings from NAPTF Testing of Unbonded PCC Overlays IPRF Project 04-02: Improved Overlay Design Parameters for Concrete Airfield Pavements —The Baseline Experiment IPRF Project 06-03: Evaluation of Design Parameters for Rigid Overlays —SCI Validation Study

  2. Overview

  3. Baseline Experiment—2006 (2007) 9 inch OL 7.5 inch OL 6 inch OL 10 inch SL 7.5 inch UL 6 inch UL Low-strength Subgrade Medium-strength Subgrade High-strength Subgrade SCI Validation Study—2007/2008 (2009) 7.5 inch OL 6 inch OL 10 inch SL 7.5 inch SL 9 inch OL 6 inch SL Low-strength Subgrade Medium-strength Subgrade High-strength Subgrade Full-Scale Testing at the NAPTF

  4. Longitudinal and Transverse Cross-Sections NORTH SOUTH 10 12.5 12.5 12.5 12.5 5 5 12.5 12.5 12.5 12.5

  5. 8.6-in PCC OL SCI Passes Date 08/01/06 2046 92 6 12 Final Passes OL SCI UL SCI 08/03/06 2574 80 08/04/06 2574 73 6.3-in PCC UL 5146 14 32 5 11 5.6-in Aggregate Base 08/10/06 2772 73 Subgrade k=135 pci 08/11/06 3234 68 10 4 08/24/06 3234 63 08/28/06 3234 57 10 Triple Dual Tandem 10 10 8 8 09/13/06 3234 46 6 6 54 in 4 4 09/14/06 3744 39 9 3 09/19/06 4552 31 09/22/06 5146 24 57 in 09/29/06 5146 19 2 8 57 in 10/02/06 5146 16 10/03/06 5146 14 50,000 lbs/wheel 230 psi tire pressure 1 7 -30 -17.5 -5 0 -25 -12.5 Test Item N1 UL SCI = 100

  6. 8.7-in PCC OL 08/04/06 3168 93 6 12 08/08/06 3432 85 Final Passes OL SCI UL SCI SCI Passes Date 08/09/06 3894 78 6.3-in PCC UL 08/10/06 4356 76 08/11/06 4818 67 12142 7 39 5 11 5.8-in Aggregate Base 09/13/06 5016 54 09/14/06 5526 51 Subgrade k=135 pci 09/19/06 8116 50 09/22/06 8116 46 4 10 09/26/06 9370 32 10 Dual Tandem 10 10 8 8 09/29/06 11020 22 6 6 54 in 4 4 10/02/06 11614 16 3 9 10/03/06 12142 7 57 in 10/31/06 12142 7 2 8 50,000 lbs/wheel 230 psi tire pressure 1 7 30 5 17.5 0 12.5 25 Test Item S1 UL SCI = 100

  7. Transition 1S-12U 1N-12U 1N-6U 1S-6U 02/20/07 1S-11U 1N-5U 1N-11U 1S-5U 1N-10U 1N-4U 1S-10U 1S-4U 1S-9U 1N-3U 1N-9U 1S-3U 1N-2U 1S-8U 1N-8U 1S-2U 1N-7U 1N-1U 1S-7U 1S-1U Transition 12/18/06 Structural Section 1

  8. 9.3-in PCC OL 12 6 4950 77 11/21/07 SCI Passes 3696 88 Date 11/14/07 7194 68 12/03/07 6.3-in PCC UL 4422 83 11/19/07 7986 55 12/05/07 5 11 5.6-in Aggregate Base 8712 51 12/07/07 9108 48 12/10/07 Subgrade k=135 pci 9504 42 12/11/07 4 10 11286 27 12/19/07 10 Triple Dual Tandem 10 10 8 8 13398 26 01/11/08 6 6 54 in 4 4 14850 24 01/16/08 9 3 15510 12 01/18/08 57 in 8 2 57 in 42.5k lbs/wheel 230 psi tire pressure 1 7 -30 -17.5 -5 0 -25 -12.5 Test Item N1 Underlay SCI Beginning 25 Final 3

  9. 9.3-in PCC OL 12 6 SCI Passes 33264 20328 27126 31350 32604 30756 24684 18 20 23 29 58 52 46 Date 03/26/08 03/11/08 03/21/08 03/05/08 04/02/08 03/24/08 02/25/08 6.3-in PCC UL 5 11 5.8-in Aggregate Base Subgrade k=135 pci 9966 88 12/13/07 10 4 10 Dual Tandem 10 10 8 8 6 6 54 in 4 4 30096 31 03/20/08 14850 80 01/16/08 3 9 16316 80 01/23/08 57 in 19008 70 02/01/08 2 8 19602 63 02/04/08 42.5k lbs/wheel 230 psi tire pressure 1 7 30 5 17.5 0 12.5 25 Test Item S1 Underlay SCI Beginning 23 Final 8

  10. SCI Gears Performance Measured Responses Layer Interactions Selected Summary of Goals and Findings

  11. 12 6 5 11 10 4 3 9 8 2 1 7 -30 -17.5 -5 A. Refine the relationship between underlying pavement effective modulus and SCI. SCI was calculated according to ASTM D 5340 “Standard Test Method for Airport Pavement Condition Index Survey.” The SCI value of a test item represents the crack types, crack density and crack severity that are distributed in the 12 slabs within a test item.

  12. Dr. Rollings’ Model • Observation on 6 slabs on subgrade at WES. • Cracks were introduced by dropping a headache ball. • Initial slab moduli were determined by BISDEF from FWD results. • Deteriorated slab moduli were determined by using BISAR to match the deflection under the center of the loaded plate. • Subgrade was assigned a constant value = 10000 psi. • SCI of slabs were calculated based on assumption that a single type of crack in one slab represents 50% of slabs within a test item having the same specific type of crack.

  13. Underlay SCI Investigation

  14. Comparison to Rollings Relationship

  15. Alternate Indicators of Structural Damage or Crack Density 10 X 10 grid in 12.5 ft X 12.5 ft slab

  16. Relationship between Underlay E-Ratio and Distress Density Intervals

  17. Finding: Rollings equation using SCI provides a reasonable fit to BAKFAA moduli from HWD testing for the underlay. • Recommendation: Continue use of the Rollings equation, with some modification.

  18. B. Improve understanding of how underlay condition affects overlay performance, and of the interaction between pavement layers. SCI Initial – Final (Passes) 42,500-lb wheel load 50,000-lb wheel load

  19. Baseline Experiment

  20. SCI Validation Study

  21. Baseline Experiment:Approximate Passes to SCI Values

  22. SCI Validation Study:Approximate Passes to SCI Values

  23. Finding: Considering load effects only, unbonded overlays over existing pavements with lower SCI values accumulated more passes to failure than anticipated. • Finding: Overlays of equal or less thickness to the existing pavement achieved the best performance, for the same overall total pavement thickness.

  24. Matched and Mismatched Transverse Joints • Examined on the basis of: • Overall performance • Intact slab life • Load transfer efficiency • Deflection basin area • Although matched and mismatched transverse joints exhibited slightly different mechanical behavior for the unbonded overlay, the passes prior to the first crack or to failure were affected more by other structure parameters such as E*h ratio.

  25. Intact Slab Life – Number of passes prior to the first crack of a slab normalized to number of passes prior to SCI = 80 of the test item North Test Item (Initial UL SCI)

  26. Intact Slab Life – Number of passes prior to the first crack of a slab normalized to number of passes prior to SCI = 80 of the test item South Test Item (Initial UL SCI)

  27. Recommendation: From this experiment, there was no evidence to indicate that joints should not be mismatched if there is a reason to do so. Other factors should govern this decision.

  28. C. Quantify differences in responses and resulting impacts on failure criteria between dual tandem and triple dual tandem gears. Passes to SCI Levels

  29. Ratios of Passes on Test Items (South/North) Total Gear Load on North Test Items = 150% of Total Gear Load on South Test Items

  30. Predicted Ratios from FAARFIELD 1.304 (South/North) Total Gear Load on North Test Items = 150% of Total Gear Load on South Test Items

  31. Strain Recovery % Between AxlesBaseline ExperimentPre-Cracking Responses

  32. D. Verify whether measured responses match predicted responses from current models and design methods. (Rollings, 1988)

  33. (Rollings, 1988)

  34. BASELINE EXPERIMENT FAARFIELD 1.304 ANALYSIS SUMMARY WITH MR = 550 psi

  35. SCI VALIDATION STUDY FAARFIELD 1.304 ANALYSIS SUMMARY WITH MR = 550 psi

  36. Baseline Test Item N1

  37. Baseline Test Item S1

  38. SCI Validation Test Item N1

  39. SCI Validation Test Item S1

  40. Data for Ongoing and Future Analysis

  41. CUMULATIVE AREA AND PEAK STRAIN FOR ODD-NUMBERED PASSES (WEST TO EAST) FOR EG-O-N1-1B

  42. CUMULATIVE AREA AND PEAK STRAIN FOR EVEN-NUMBERED PASSES (EAST TO WEST) FOR EG-O-N1-1B

  43. Acknowledgements Jim Lafrenz Project Panel David Brill, Gordon Hayhoe, Murphy Flynn, Frank Pecht, . . . . . Project Team Members QES: Co-PI Dennis Morian, Joe Reiter, Suri Sadasivam, . . . . . Penn State: Lin Yeh, Vishal Singh, Hao Yin, Maria Lopez de Murphy Other team members: Tasos Ioannides, Shie Shin Wu, John Rice

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