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Brian Prowell Don Watson Graham Hurley Ray Brown

Stone Matrix Asphalt (SMA) for Airfield Pavements 2010 FAA Worldwide Airport Technology Transfer Conference . Brian Prowell Don Watson Graham Hurley Ray Brown. Acknowledgements.

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Brian Prowell Don Watson Graham Hurley Ray Brown

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  1. Stone Matrix Asphalt (SMA) for Airfield Pavements2010 FAA Worldwide Airport Technology Transfer Conference Brian Prowell Don Watson Graham Hurley Ray Brown

  2. Acknowledgements • This work was conducted as part of the Airfield Asphalt Pavement Technology Program Project 04-04, Evaluation of Stone Matrix Asphalt for Airfield Pavements.

  3. Background • SMA designed in Germany in the 1960’s as mix resistant to studded tires • Adopted in US in 1991

  4. Gradation

  5. Aggregate SkeletonStone Matrix Asphalt Mix

  6. Aggregate SkeletonDense-Graded Mix

  7. 9.5 mm NMAS SMA Surface Texture

  8. How is SMA Different? • Gradation • Asphalt Content • Dust Content • Stabilizing Additives

  9. SMA Performance in the USA • Marshall- 50 blow design has been used • Improved performance over HMA

  10. Objectives of AAPTP 04-04 Study The objectives: • Evaluate performance of SMA pavements • develop technical guidance for the FAA to implement SMA on U.S. airfields

  11. Documented SMA Use on Airfields • Australia • China • Europe • Belgium • Germany • Italy • Norway • United States

  12. Experimental Design

  13. Mix Combinations

  14. Rutting Susceptibility • Laboratory evaluations typically show SMA to have increased rutting susceptibility compared to HMA • Experiments to compare SMA and P401 • Three tests: stability and flow, repeated-load creep, and Hamburg wheel-tracking

  15. Stability and Flow

  16. Repeated Load Permanent Deformation to Asses Rutting Potential • 100 mm diameter, 150 mm height • 6% air voids • 58 C (climatic high temp. - 6 C ) • 20 psi confinement • 0.1 second load; 0.9 second rest • 100, 200, 350 psi vertical load • Continue for 10,000 cycles or until tertiary flow

  17. With the repeated load test the permanent deformation performance of SMA mixtures and P401 mixtures were not significantly different.

  18. Hamburg Test Test combines rutting performance with moisture susceptibility • Uses a steel wheel 47 mm wide by 204 mm diameter • Load = 685 N (154 lb) • Full test is 20,000 cycles • Temperature - 50 C • VTM - 6 + 0.5 % • Tested under water

  19. With Hamburg, rutting very similar for P-401 and SMA

  20. Overlay Tester Results

  21. Fuel Resistance • China has reported that SMA improves fuel resistance • AAPTP 05-02 evaluating fuel resistant sealers and binders • Citgo Fuel Resistance Test • Soaked in kerosene for 24 hours • Mass loss less than 5% good

  22. Fuel Resistance

  23. Deicer ResistanceImmersion Tensile Test

  24. Two Case Studies • Aviano AFB, Italy • Spangdahlem AFB, Germany

  25. Aviano SMA Constructed in 1999 Provided good performance up through 2010 Some water issues More rubber build up No grooving

  26. Rubber Build Up on SMA Aviano Air Force Base 2000

  27. Aviano Surface Texture in 2000

  28. Seepage of Water from Underneath, Aviano 2000

  29. Draindown, Aviano 2000

  30. Aviano, 2006

  31. Aviano 2008

  32. SMA Aviano • Provided good performance to date • Good friction • Some water issues • No grooves

  33. Based on good performance at Aviano, SMA was used at Spangdahlem in 2007

  34. Spangdahlem AFB • Milled and overlaid with SMA in 2007 • High density obtained • Some water vapor (blisters) problems

  35. Spangdahlem 2006, patch

  36. Spangdahlem 2006, cracking and condition of grooves

  37. After mixture was milled, approximately 2 weeks of rainfall occurred causing the asphalt mixture to become soaked with moisture

  38. Construction in 2007 • The contractor used two asphalt plants, two pavers, and up to 8 rollers • In place air voids were typically 3 to 4 percent

  39. Spangdahlem, 2007, moisture on surface of SMA

  40. Spangdahlem, 2007, blisters caused by water vapor

  41. Plans are underway to remove and replace the SMA at Spangdahlem

  42. Summary of SMA / P401 Comparison 1Based on laboratory tests performed as part of this study. 2Based on review of the literature or in-service performance.

  43. Recommendations • SMA could cost 82 to 94 percent more than dense-graded mixes and still be cost effective on a life-cycle basis. • SMA is not typically suited to small quantity production • 65 gyrations recommended as alternative to 50-blow Marshall

  44. Questions? The complete report is available at: www.AAPTP.US Contact Information for authors: Ray Brown ray.brown@usace.army.mil Brian Prowell Brian.AMSLLC@Charterinternet.com Don Watson Watsode@auburn.edu Graham Hurley Graham.AMSLLC@Charterinternet.com

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