Advancements In Tack Coats 2011


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Advancements In Tack Coats 2011

  1. 1. Advancements in Tack Coats January 2011
  2. 2. Tack or Bond Coat• A light application of asphalt or asphalt emulsion used to promote the bond between an existing and a new hot mix asphalt layer.• The goal is to bond subsequent hot mix layers in order to approach the strength of a single, monolithic layer.• Inadequate bond strength at the interfaces can lead to slippage between the asphalt layers, which may cause shoving, cracking, and other premature pavement failures.
  3. 3. Traditional Tack CoatsProblems with traditional tack coats:• Traditional tack coats are often tracked away from the intended application area.• Tracking is unsightly and results in less tack available to achieve maximum bond strength.• Tack coat tracked into parking lots, driveways, and adjacent areas is expensive to remove.• Tracking in intersections can create a liability due to a loss of friction.
  4. 4. Traditional Tack Coat
  5. 5. Traditional Tack Coat
  6. 6. Traditional Tack Coat
  7. 7. Advancements in Tack Coats:Trackless Tack• ―Trackless Tack‖ or NTSS-1HM is a specially formulated emulsion for high performing, non-tracking tack coat applications.• Applies like a traditional tack coat with conventional equipment.• Allows for faster paving applications and improved overall pavement strength.
  8. 8. Trackless Tack
  9. 9. Trackless Tack
  10. 10. Trackless TackBenefits of Trackless Tack:• Ultra fast curing tack coat, often in 10 minutes or less• Non-tracking – No loss of tack material to adjacent areas – Improved appearance and less cleaning of driveways, parking lots, vehicles, and construction equipment – Less inconvenience to the public and improved paving crew efficiency
  11. 11. Trackless TackBenefits of Trackless Tack (continued):• Improved bond between pavement layers – Less shoving, cracking, and other failures associated with inadequate bond – May reduce rutting 1• Improved density measurements – More consistent air voids across the mat 2, 3 – Improved values reported at the unconfined edge due to less shoving
  12. 12. Performance:FDOT Testing on Bond Strength• FDOT testing on core samples of HMA using RS-1(H) and NTSS-1HM.• Cores were sheared apart to determine the interfacial shear strength.• Trackless Tack showed 54% higher shear strength.
  13. 13. Performance:LTRC (NCHRP 9-40) 3, 4• The Louisiana Transportation Research Center (LTRC) recently evaluated the performance of three commonly used tack coat materials— CRS-1, SS-1H, and NTSS-1HM ―Trackless Tack.‖• The study was based on controlled field conditions on an existing asphalt surface at LADOTD‘s Pavement Research Center followed by the application of a 3‖ hot mix asphalt overlay.
  14. 14. Performance:LTRC (NCHRP 9-40) 3, 4• Tack coat applications were carefully controlled• Core samples were obtained and evaluated for Interfacial Shear Strength (ISS) to determine the bonding of the various tack coat materials• A laboratory shear tester (LISST) was used to conduct the testing• An analysis of air voids was also completed to determine the effect of the different tack coat materials on HMA density
  15. 15. Performance:LTRC (NCHRP 9-40) 3 Interfacial Shear Strength 500 Shear Strength, kPa 400 300 200 100 0 0 0.05 0.1 0.15 0.2 Residual Application Rate (gal/yd2 ) CRS-1 SS-1H NTSS-1HM
  16. 16. Performance:LTRC (NCHRP 9-40) 3Summary of ISS Results:• At all application rates, NTSS-1HM yielded the highest bond strength• CRS-1, regardless of application rate, never achieved the ISS associated with the lowest application of NTSS-1HM.• Using an estimated monolithic mixture strength of 729 kPa, NTSS-1HM yielded nearly 60% of the maximum bond strength compared to only 38% with SS-1H, and less than 14% with CRS- 1.
  17. 17. Performance:LTRC (NCHRP 9-40) 3 Maximum Interfacial Shear Strength 800 700 Percentage of Monolithic Strength CRS-1 13.4% Shear Strength, kPa 600 SS-1H 37.5% 500 NTSS-1HM 59.0% 400 300 200 100 0 CRS-1 SS-1H NTSS-1HM Monolithic Mixture
  18. 18. Performance:Can Tack Coats reduce rutting? 1Abadie, C., ―Louisiana Bituminous Surface Preservation Program: Enabling Thin Overlays,‖ LAPA Annual Meeting, June 2009
  19. 19. Performance:LTRC (NCHRP 9-40) 3 Variation of HMA Air Voids 10 8 Air Voids, % 6 4 2 0 0.031 0.062 0.155 Residual Application Rate (gal/yd2 ) CRS-1 SS-1H NTSS-1HM
  20. 20. Performance:LTRC (NCHRP 9-40) 3Analysis of Air Void Measurements:• The study also evaluated the in place air voids of each HMA section with varying application rates of CRS-1, SS-1H, and NTSS-1HM.• NTSS-1HM sections had the most consistent air void contents regardless of application rate.• The data suggests that the increased bond strength with NTSS-1HM reduces movement at the HMA layer interface allowing for more efficient compaction.
  21. 21. Performance:LTRC (NCHRP 9-40) 4• The study subsequently evaluated PG 64-22 asphalt binder as a tack coat• PG 64-22 in Louisiana typically meets the same specification as PG 67-22• The hot applied asphalt binder was also compared to CRS-1, SS-1H, and NTSS-1HM ―Trackless Tack‖• PG 64-22 exhibited lower bond strength than NTSS-1HM at all application rates
  22. 22. Performance:LTRC (NCHRP 9-40) 3 Interfacial Shear Strength 100 Shear Strength, psi 80 60 40 20 0 0 0.05 0.1 0.15 0.2 Residual Application Rate (gal/yd2 ) CRS-1 PG 64-22 SS-1H NTSS-1HM
  23. 23. Performance:Low Temperature (LTRC) 5• In conjunction with the NCHRP 9-40 study, LTRC also evaluated the bonding performance of two common tack coat materials at various temperatures – NTSS-1HM ―Trackless Tack‖ = high modulus – CRS-1 = low modulus• The study was performed to address that historical studies were only evaluated at ambient temperatures, 77 F
  24. 24. Performance:Low Temperature (LTRC) 5
  25. 25. Performance Analysis:Low Temperature (LTRC) 5• The data shows that low modulus materials, like CRS-1, possess much lower bonding performance at higher temperatures• NTSS-1HM ―Trackless Tack‖ possessed far better high temperature performance coupled with mostly equal or better low temperature bond strengths
  26. 26. Performance Analysis:Low Temperature (LTRC) 5• The data shows that bond strength increases with decreasing temperature, as expected• NTSS-1HM, however, maintains excellent bond strength even as low as -10 C• Considering most tack coat failures occur at high temperatures, the data explains why high modulus materials have consistently out performed low modulus tack coats in the field even in cooler climates and conditions
  27. 27. Trackless TackTypical Physical Properties PARAMETER TEST METHOD MIN MAX Saybolt Furol Viscosity, SFS @ 25 oC ASTM D88 20 400 Storage Stablility, 1 day, % ASTM D244 ---- 1 Settlement, 5 day, % ASTM D244 5 Residue by Distillation ASTM D244 50 ---- Oil Distillate, % ASTM D244 ---- 1 Sieve Test* ASTM D244 ---- 0.3 Tests on Residue Penetration @ 25 oC ASTM D5 ---- 20 Softening Point (oC) ASTM D36 65 ---- Solubility, % ASTM D2042 97.5 ---- Original DSR @ 82 oC (G*/SIN , 10 rad/sec) AASHTO T111 1 ---- * The Sieve result is tested for reporting purpose only, and it may be waived if no application problems are present in the field.
  28. 28. Advancements in Tack Coatsfor OGFC• Open Graded Friction Courses are very popular mixes because of improved safety and reduced roadway noise• The use of OGFC has been curtailed in some areas because of durability issues with these mixes• Bonded Friction Courses using a high application rate of polymer modified tack coats can improve durability
  29. 29. Open Graded Friction CoursesAdvantages Disadvantages6• Reduced risk of • Reduced durability hydroplaning • Raveling/Debonding of• Improved drainage OGFC layer• Improved visibility • Stripping in OGFC and/or• Coarse surface for underlying layers improved friction values • Difficult snow and ice• Improved ride numbers removal• Reduced noise• Improved driver safety!
  30. 30. I-35 San Antonio, TXWay, G., ―PCCAS AR Task Force Report,‖ September 22, 2007
  31. 31. FM 1431 Travis County, TX Dense Graded HMA Permeable Friction CourseWay, G., ―PCCAS AR Task Force Report,‖ September 22, 2007
  32. 32. Existing Surface PFCWay, G., ―PCCAS AR Task Force Report,‖ September 22, 2007
  33. 33. Developments in OGFC• Durability issues can be largely addressed by producing a Bonded Friction Course (BFC) with improved tack coat materials and processes• Historically, the Novachip® process using a ―Spray Paver‖ has been the most well known Bonded Friction Course system
  34. 34. Novachip® Spray Paver Process• Developed by Colas in the late ‗80s in France• Substantial use in the US since the late ‗90s• Consists of an application of a thin, gap graded HMA layer over a polymer modified tack coat• Uses a specialized ―Spray Paver‖ machine to apply a thick tack coat immediately before the gap graded layer is applied• Uses a polymer modified tack coat—Novabond
  35. 35. Novabond Tack CoatUsed in Spray Paver• The polymer modified emulsion wicks into the new gap graded mix by displacement and water vaporization• The thick application seals minor cracks in the existing surface layer and forms a strong bond• The resulting membrane also seals the existing surface to prevent water intrusion• CQS-1HP emulsion with a min. 60% residue• Typical application rate of 0.13 to 0.30 gal/yd2
  36. 36. Novachip® Spray Paver Process The emulsion membrane “wicks up” around the HMA aggregates The emulsion cures, 5/8” minimum bonding the mix & pavement depth of mix 9-12 m 3/8” nominal coating on aggregates aggregate size 3/16”emulsion membrane depth Existing
  37. 37. Novachip® Spray Paver
  38. 38. Novachip® Spray Paver
  39. 39. Novachip® Spray Paver
  40. 40. Novachip® Spray Paver Estimated Cost = $800,000/
  41. 41. Developments in BondedFriction Course• Bonded Friction Course applications using the Novachip® system have performed well over the last 20 years• However, the use and adoption has been slowed because of the high cost associated with the specialized ―Spray Paver‖ required by the Novachip® process
  42. 42. Developments in BondedFriction Course• Because of the increased cost, there has been a need for a non-tracking, polymer modified tack coat material to avoid the use of the specialized spray paver• The goal is to use existing paving equipment, and still apply a high application rate of polymer modified tack
  43. 43. Developments in BondedFriction Course• Even with using a fast drying material, like Trackless Tack, curing rates for such high application rates have been unsatisfactory• Extended cure times would lead to unacceptable delays and/or tracking• Developments led to a new hot-applied, polymer modified Trackless Tack material, UltraFuse Trackless Tack
  44. 44. UltraFuse Trackless TackNon-Tracking Hot Applied Polymerized Tack• Applied with conventional distributors and paving equipment• Fills cracks in the existing pavement and seals the surface• Can be paved on immediately after application, in approximately 10 seconds• The non-tracking surface liquefies during placement of the new OGFC surface
  45. 45. UltraFuse Trackless TackContinued• The liquefied polymer modified membrane wicks into the new OGFC layer by displacement forming a strong bond• Polymer modified for improved flexibility and bond strength• Application rate equals the residual asphalt associated with emulsion applications: 0.09 to 0.18 gal/yd2
  46. 46. UltraFuse Trackless TackUS 301 in Tampa, FL with FDOT
  47. 47. UltraFuse Trackless TackUS 301 in Tampa, FL with FDOT
  48. 48. UltraFuse Trackless TackUS 301 in Tampa, FL with FDOT 15 seconds after application
  49. 49. UltraFuse Trackless TackUS 301 in Tampa, FL with FDOT
  50. 50. UltraFuse Trackless TackUS 301 in Tampa, FL with FDOT
  51. 51. UltraFuse Trackless TackUS 301 in Tampa, FL with FDOT
  52. 52. UltraFuse Trackless TackUS 301 in Tampa, FL with FDOT
  53. 53. UltraFuse Trackless TackUS 301 in Tampa, FL with FDOT
  54. 54. UltraFuse Trackless TackUS 301 in Tampa, FL with FDOT
  55. 55. UltraFuse Trackless TackUS 301 in Tampa, FL with FDOT NT HAP Tack Approximately 1/4- 1/3 inch thick Pavement Interface
  56. 56. NCAT Testing• After the FDOT application on US 301 in Tampa, BEI contracted the National Center for Asphalt Technology (NCAT) to do further studies• Three different tack coats were evaluated: CQS-1HP (generic Novabond), NTSS- 1HM, and UltraFuse Trackless Tack
  57. 57. NCAT Testing(continued)• The same residual asphalt application rates were chosen for each tack coat material: – 0.08, 0.13, and 0.18 gallons per square yard• The goal was to determine the maximum interfacial shear strength obtained with each tack coat material
  58. 58. UltraFuse Trackless Tack forBonded Friction Course• In September of 2010, ALDOT created a special provision to use ―PG Asphalt for Trackless Tack‖ with an OGFC mix on US 231 in Wetumpka, AL• The application and paving was performed on September 28, 2010 in the right side northbound (0.15 gallons/yd2) and southbound lanes (0.18 gallons/yd2)
  59. 59. UltraFuse Trackless Tack”PG Asphalt for Trackless Tack” from ALDOT SpecialProvision No. 08-0945 September 7, 2010PARAMETER TEST METHOD MIN MAXRotational Viscosity AASHTO T316 ---- 3000@ 135 °C, cPPenetration @ 25 °C, dmm ASTM D5 ---- 30Softening Point, °C ASTM D36 70 ----Original DSR @ 82 °C, AASHTO T315 1.0 ----G*/sin( ), kPa
  60. 60. UltraFuse Trackless TackUS 231 in Wetumpka, AL with ALDOT
  61. 61. UltraFuse Trackless TackUS 231 in Wetumpka, AL with ALDOT
  62. 62. UltraFuse Trackless TackUS 231 in Wetumpka, AL with ALDOT
  63. 63. UltraFuse Trackless TackUS 231 in Wetumpka, AL with ALDOT
  64. 64. UltraFuse Trackless TackUS 231 in Wetumpka, AL with ALDOT
  65. 65. UltraFuse Trackless TackUS 231 in Wetumpka, AL with ALDOT
  66. 66. UltraFuse Trackless TackUS 231 in Wetumpka, AL with ALDOT
  67. 67. UltraFuse Trackless Tack forBonded Friction Course• Allows the agency and contractor to apply a Bonded Friction Course with conventional paving equipment• Eliminates the requirement and cost associated with the specialized Spray Paver• Improves bond strength to increase the durability of OGFC mixes
  68. 68. References1. Abadie, C. ―Louisiana Bituminous Surface Preservation Program: Enabling Thin Overlays,‖ LAPA Convention, June 2009.2. Cooper, S. and Mohammad, L. ―Influence of Tack Coat Type on the Density of HMA Mixtures,‖ 2006 Pavement Performance Seminar, April 2006.3. Mohammad, L., Bae, A., Elseifi, M., Button, J., and Scherocman, J. Interface Shear Strength Characteristics of Emulsified Tack Coats. Published and presented at the Association of Asphalt Paving Technologists Annual Meeting, Minneapolis, MN, March 16, 2009.4. Mohammad, L., ―NCHRP Project 9-40: Optimization of Tack Coat for HMA Placement— Research Update,‖ LAPA Convention, June 2009.5. Bae, A., Mohammad, L., Elseifi, M., Button, J., Patel, N. ―Effects of Temperature on the Interface Shear Strength of Emulsified Tack Coats and Its Relationship to Rheological Properties,‖ TRB Annual Meeting, Washington, DC, January 20106. Kandhall et. al, ―Open Graded Friction Course: State of the Practice,‖ TRB Circular, December 1998.7. Way, G., ―PCCAS AR Task Force Report,‖ September 22, 2007.8.
  69. 69. Special Thanks• FDOT and APAC on US 301 in Tampa• ALDOT and Wiregrass Construction on US 231 in Wetumpka• NCAT—Dr. Nam Tran
  70. 70. Questions?