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NCAT Update

NCAT Update. AFK10 April 21, 2005. Structural Study at the NCAT Test Track. R. Buzz Powell Dr. David Timm. STRUCTURAL EXPERIMENT. 9”. 7”. 5”. Observations. 5 inch layers failed about as predicted Some cracking in 7 inch layers Modified sections failed first but not by much

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NCAT Update

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  1. NCAT Update AFK10 April 21, 2005

  2. Structural Studyat the NCAT Test Track R. Buzz Powell Dr. David Timm

  3. STRUCTURAL EXPERIMENT 9” 7” 5”

  4. Observations • 5 inch layers failed about as predicted • Some cracking in 7 inch layers • Modified sections failed first but not by much • Less rutting in modified sections

  5. Based on Test Track Work the Following has been Adopted • AL, FL, and NC use more fine-graded mixes • FL uses more modified binders • AL, OK, and TN have begun to use SMA • OK has more confidence in APA • AL, GA and TN have increased AC contents

  6. Automated QC Testing Utilization of Automation and Real-Time Testing to Improve QC/QA Procedures For Hot Mix Asphalt Dr. Randy West

  7. QC/QA State of Practice • Most HMA requirements for QC are quite complex. • QC focus has shifted to the end product and away from controlling the process. • Due to the time lag between production and results, hundreds of tons are likely to have been produced, creating a high risk if mix is out of tolerance.

  8. Automated Asphalt Content Using a Plant’s Controls Use binder flow rate (gal./min. → tons/hr) with a flow meter or non-powered, positive-displacement pump. And feed rates of aggregates and RAP (tons/hr) with belt scales, tachometers and a computer integrator.

  9. HMA Binder Mix Plant Reading 3.9% AC Permeable HMA Base Plant Reading 2.1% AC AC Content Comparisons

  10. PG 67-22 Comparison of Binder Viscosity Measurements

  11. Why Warm Asphalt? Research by Stroup-Gardiner and Lange at AU Indicates increased emissions with increased temp.

  12. We Can Reduce Temperatures Today with No Additives • Pre-Superpave – typical compaction temperature 275 F • Place Thicker Lifts – NCHRP 9-27 • 3 x NMAS for fine graded • 4 x NMAS for coarse graded • Tarp Trucks • Drier Aggregate – pave under stockpiles

  13. What are Warm Asphalt Mixes? Several process have been developed to improve mixture workability allowing lower production and laydown temperatures • WAM Foam – Shell/Kolo Veidekke • Zeolite – Eurovia/Hubbard Construction • Sasobit – Sasol Int./Moore and Munger • New processes

  14. AIRFIELD ASPHALT PAVEMENT TEST PROGRAM(AAPTP)

  15. PROCESS • FAA Funded in July 2004 • Contractor is Auburn University • AAPTP Director reports to the College of Engineering not to the Director of NCAT • Program size $1.6 million per year • WEB Site: www.AAPTP.us

  16. Process Continued • Program Coordinating Group • 14 Members – • Met in October 2004 • Provides overall direction to program • Identifies the projects • Project Development Panel • Project Director • Representative of FAA • Representative of DOD • Two subject area experts

  17. Initial Projects • Adjusting PG Binder Grade Selection Procedures • Development of Guidelines for Rubblization • Guidance on the Use of Superpave Mix Design Procedures for Airfield Pavements • Evaluation of SMA for Airfields

  18. Initial Projects (Cont.) • Longitudinal Joint Construction • Improved OGFC • Evaluate Need and Develop Plan for National Certification of Airport HMA Technicians

  19. Endurance Limit of Hot Mix Asphalt Mixtures to Prevent Fatigue Cracking in Flexible Pavements NCHRP 9-38 Ray Brown Brian Prowell

  20. Flexible (Asphalt) Pavement Fatigue Long Life Pavement Top Down Fatigue Bottom Up Fatigue Surface 12” ? Surface Base Base Surface Base Sub-base Sub-base Subgrade

  21. Tire/Pavement Noise

  22. Pavements tested • Locations • NCAT test track, Michigan, Alabama, New Jersey, Maryland, Colorado, Nevada, California, Arizona, Texas, Florida, Virginia, Minnesota and Colorado • Numbers of surfaces tested • Total – 244 surfaces • HMA – 201 surfaces • PCCP – 43 surfaces

  23. Average Results • Hot Mix Asphalt • Dense Graded HMA – 97 dB(A) • Stone Matrix Asphalt – 97 dB(A) • New Generation Open Graded Friction Courses • Fine Graded – 92 dB(A) • Coarse Graded – 95 dB(A) • Portland Cement Concrete Pavement • Transverse Tined –104 dB(A) • Diamond ground – 99 dB(A) • Longitudinally Tined – 100 dB(A)

  24. Bomag’s Asphalt Manager – A First Look Brian D. Prowell

  25. U. S. Demonstration • Intelligent compaction forum, sponsored by FHWA, in Auburn, AL December 2004 • Testing conducted on BOMAG Asphalt Manager in conjunction with NCHRP 10-65 • Nuclear gage and PQI readings taken after each roller pass • Roller placed in finish position to evaluate use as “testing device”

  26. Example Growth Curve

  27. Evaluation of NDesignfor Superpave Mixes

  28. Objectives • Evaluate performance of Superpave mixes • Compare to performance of Marshall mixes • Find same materials/traffic conditions • PG Binders and same aggregates • Similar traffic/ESAL loading • Optimize the Superpave NDesign levels

  29. Project Comparisons • Age • Marshall - 5.0 years • Superpave - 4.9 years • AADT • Marshall - 13,220 • Superpave - 13,971

  30. Thanks

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