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Guidance, Parameters & Recommendations for Rubblized Pavements

Guidance, Parameters & Recommendations for Rubblized Pavements. July 2006. Wisconsin Highway Research Program Wisconsin Department of Transportation Project IC 0092-05-07. Guidance, Parameters & Recommendations for Rubblized Pavements. By: Harold L. Von Quintus, P.E. Jagannath Mallela

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Guidance, Parameters & Recommendations for Rubblized Pavements

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  1. Guidance, Parameters & Recommendations for Rubblized Pavements July 2006

  2. Wisconsin Highway Research ProgramWisconsin Department of TransportationProject IC 0092-05-07 Guidance, Parameters & Recommendations for Rubblized Pavements By: Harold L. Von Quintus, P.E. Jagannath Mallela Brian Aho Chetana Rao

  3. Presentation Overview • Objectives • Data Collection • Performance Analyses • Summary of Findings

  4. Project Objectives • Document historical information on the rubblization projects in Wisconsin. • Provide guidelines for the selection, design, testing, and construction of rubblized PCC pavements. • Determine conditions for which rubblizing PCC is a feasible rehabilitation strategy.

  5. Products • Final Report – Guidance, Parameters, & Recommendations for Rubblized Pavements. • Guidelines for Designing & Constructing Rubblized PCC Pavements, Appendix A. • Catalog of Performance History & Details of Wisconsin’s Rubblized Projects, Appendix B.

  6. Rubblization Definition: Fracturing the PCC slab in place into fragments of nominal 3 to 8 inch size or less while retaining good interlock between the fractured particles. Purpose: Eliminate reflection cracking in an HMA overlay by destroying the integrity of the PCC slab.

  7. Rubblization Projects > 20 Projects > 5 but < 20 Projects

  8. LTPP SPS-6 Projects – Distress Summary LCNWP: Traffic & structure independent. LCWP: > 4 inches is adequate.

  9. LTPP SPS-6 Projects – Distress Summary LTPP data inconclusive, other than transverse cracking dependent on HMA overlay thickness. Fatigue cracking is traffic dependent.

  10. Rubblization Timeline in Wisconsin Demo I-43 No. of Rubblized Projects Increase 1st Project RFB 1st Project MHB RFB & RFB + Guillotine Increase Thick. Adopt PG Spec. Adopt Mix Spec. Number of Rubblized Projects

  11. Project Identification & Data Collection • Identify rubblization projects in Wisconsin. • PMS database • Industry • Project summary sent to regions for confirmation. • Review historical or time series performance data to identify discrepancies. • Resolve discrepancies. • Prepare final listing of rubblization projects & create database.

  12. Project Identification & Data Collection:Summary of Discrepancies Between Data Sources • Rubblization year? • Performance data does not make sense with year of rubblization? • Rehabilitation strategy inconsistent with database – change order?

  13. Project Identification & Data Collection:Projects Used in Analyses • No conflicting information between data sources. • Best available data and information on each PM segment. • Performance data for each PM segment within project limits used in determining average values for project.

  14. Overview of Wisconsin’s Rubblized Projects – Number of Projects Relatively few projects are > 7 yrs. old!

  15. Overview of Wisconsin’s Rubblized Projects – Unit Costs, 1998 – 2004

  16. Overview of Wisconsin’s Rubblized Projects – Unit Costs, 1998 – 2004

  17. Overview of Wisconsin’s Rubblized Projects – HMA Overlay Thickness Thicker HMA overlays used in recent years!

  18. Overview of Wisconsin’s Rubblized Projects – HMA Overlay Thickness 2 to 5.5 in. 3 to 6.5 in. HMA Overlay Thickness increased in 1998.

  19. Performance Indicators Used in AnalysisExtracted from Wisconsin’s Pavement Management Database • IRI Values – Less than 4% of rubblized segments have IRI > 140 in./mi. • Rut Depths – Less than 10% of rubblized segments have rut depths > 12 mm. • PDI Values – Less than 5% of rubblized segments have PDI values > 50.

  20. Performance Data Rubblized Project:SQNO – 10390Year – 1997HMA Overlay = 3 in. Key Issues: • Data Variability • Discrepancies • Missing Data

  21. Performance Data Rubblized Project:SQNO – 11910Year – 1998HMA Overlay = 5.5 in. Key Issues: • Data Variability • Discrepancies • Missing Data

  22. Overview of Wisconsin’s Rubblized Projects – 2004 Rut Depths. Most projects have minor rut depths, with exception of the older projects!!

  23. Overview of Wisconsin’s Rubblized Projects – 2004 Distress Values. Older projects have higher amounts of distress!!

  24. Overview of Wisconsin’s Rubblized Projects – 2004 IRI Values. Most projects are still smooth!!

  25. Summary of Wisconsin’s Rubblization Projects • Over 50% of rubblized segments are less than 5 years in age. • 60% of rubblized segments have no cracking. • 50% of rubblized segments have rut depths < 6 mm. • 65% of rubblized segments are smooth with IRI values < 80 in./mi. Rubblized projects are relatively new for the above to be meaningful.

  26. Overview of Wisconsin’s Rubblized Projects – 2004 IRI Values.

  27. Overview of Wisconsin’s Rubblized Projects: 2004 IRI Values. IRI increases with age, but other confounding factors!

  28. Overview of Wisconsin’s Rubblized Projects: 2004 IRI Values.

  29. Overview of Wisconsin’s Rubblized Projects – 2004 Rut Depths.

  30. Overview of Wisconsin’s Rubblized Projects: 2004 Rut Depths. Older projects built under previous specs. have the greater rut depths!!

  31. Overview of Wisconsin’s Rubblized Projects: 2004 Rut Depths.

  32. Overview of Wisconsin’s Rubblized Projects – 2004 Distress Values.

  33. Overview of Wisconsin’s Rubblized Projects: 2004 PDI Values.

  34. Overview of Wisconsin’s Rubblized Projects: 2004 PDI Values.

  35. Summary:Rubblized Segments Performing Better Than other Rehabilitation Strategies! BUT, Average Service Life is low!! Older sections heavily influence extrapolated service life, because of higher distress.

  36. Rubblization Timeline in Wisconsin Demo I-43 No. of Rubblized Projects Increase CONFOUNDING FACTORS COMPLICATE THE ANALYSIS! 1st Project RFB 1st Project MHB RFB & RFB + Guillotine Increase Thick. Adopt PG Spec. Adopt PG Spec. Number of Rubblized Projects

  37. Wisconsin’s Rubblized Projects:Before & After 1997. Change in HMA mixtures: • Performance-Graded binders • Mixture design criteria • Thicker HMA overlays

  38. Wisconsin’s Rubblized Projects – HMA Overlay Thickness

  39. Wisconsin’s Rubblized Projects – Extrapolated Service Life • Must stratify projects into groups with similar HMA mixture specifications & overlay thickness. • If excessive rutting does not occur within the first 4 years, excessive rutting probably does not occur. • If HMA overlay is built smooth, it will remain smooth until other distresses begin to occur.

  40. Wisconsin’s Rubblized Projects – Extrapolated Service Life Where: t = Age in years tdesign = Design life in years a,b = Regression coefficients

  41. Wisconsin’s Rubblized Projects – Extrapolated Service Life

  42. Wisconsin’s Rubblized Projects – Extrapolated Service Life

  43. Wisconsin’s Rubblized Projects – Extrapolated Service Life Age & mix properties are dominant factors. HMA thickness minor factor.

  44. Expected Service Life Based on Elastic Modulus & Damage • Tensile strain at bottom of HMA overlay • Elastic modulus of rubblized PCC; 35 to 120 ksi • Average elastic modulus of rubblized PCC – 65 ksi

  45. Expected Service Life Based on Damage & Elastic Modulus, yrs. Changes made around 1997 were very beneficial to HMA performance!!

  46. Comparison of Average Service Lives from Different Studies

  47. Performance Analysis Summary • 1990 to 1997 projects; expected service life equals 13 years. • Projects built after 1997; expected service life exceeds design life. • NEEDS TO BE CONFIRMED WITH DATA. • Age & mix are predominant factors; insufficient number of projects to determine effect of other factors. • Predominant distress types are longitudinal cracking outside wheel path & transverse cracking.

  48. Performance Analysis Summary • Rutting not a controlling factor. • Average elastic modulus of rubblized PCC layer is 65 ksi, Recommended value for design. • CONFIRM WITH DATA • Minimum in place modulus of foundation is 15 ksi. • Minimum HMA overlay thickness is 4 inches. • NEEDS TO BE CONFIRMED WITH DATA.

  49. Summary • Is rubblization a cost effective strategy? – YES • Parameters to be considered: • Detailed site investigation • Minimum foundation modulus = 15 ksi • Recommended values for design: • AASHTO structural layer coefficient = 0.20 • Elastic modulus of PCC layer = 65 ksi • Problems encountered with rubblization: • HMA overlay too thin • Omission of drainage layers • Localized soft spots in foundation

  50. Summary • Types of test and frequency – Insufficient data from Wisconsin projects. • Test strip for each foundation and PCC thickness • Deflection basin tests, 100 to 200 ft interval • Data to monitor for confirming rehab strategy – Insufficient data from Wisconsin projects. • Deflection basin data • Gradation of rubblized layer • Volumetric properties of HMA • Distress with time

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