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DOUBLE BARREL GREEN SYSTEM AN EQUIPMENT MEANS TO PRODUCE WARM MIX By Malcolm Swanson, P.E.

DOUBLE BARREL GREEN SYSTEM AN EQUIPMENT MEANS TO PRODUCE WARM MIX By Malcolm Swanson, P.E. Vice President – Engineering Astec, Inc. SUSTAINABILITY. Conserving our resources Reducing energy consumption Reducing Greenhouse Emissions Being more environmentally friendly

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DOUBLE BARREL GREEN SYSTEM AN EQUIPMENT MEANS TO PRODUCE WARM MIX By Malcolm Swanson, P.E.

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  1. DOUBLE BARREL GREEN SYSTEM AN EQUIPMENT MEANS TO PRODUCE WARM MIX By Malcolm Swanson, P.E. Vice President – Engineering Astec, Inc.

  2. SUSTAINABILITY • Conserving our resources • Reducing energy consumption • Reducing Greenhouse Emissions • Being more environmentally friendly • And building a better, long-lasting pavement

  3. GLOBAL WARMING

  4. ADDITIVES Aspha-Min WAM Evotherm Sasobit EQUIPMENT Double Barrel Green WARM MIX TECHNOLOGIES

  5. The ASTEC Double Barrel Green System Is An Equipment Package That Enables The Making Of Warm Mix By Adding Only Water to the Liquid Asphalt.

  6. Outline • Background and Benefits of Warm Mix • Equipment Explanation • Case Studies • Experience to Date

  7. Background • Mix temperatures 50-100F (28 – 44 C) cooler than conventional mix methods • Achieved by lowering the viscosity of the AC binder • Methods: additives, additives with water, foaming with water only, etc. • Foaming first introduced in the 1950’s • High fuel cost and pressure to reduce emissions make Warm Mix more attractive.

  8. Benefits of Warm Mix • Improves mix workability • Reduces emissions • Eliminates blue smoke and odor • Less total emissions • Improves Comfort & safety of workers • Improves Pavements • Extends resources via more recycle • Less fuel • Increases Plant Capacity

  9. Improves Workability

  10. Reduces Emissions

  11. CONVENTIONAL HOT MIX WARM MIX

  12. No Smoke – No Smell…Why? • Light oils are either put in asphalt or left in asphalt during refining • These light oils boil above 285oF (140 C) • By mixing at below 285oF (140 C), the boiling point is never reached… eliminating smoke (vapor) and corresponding smell

  13. Reduces total emissions…Why? • Producing mix at lower temperatures requires less fuel burning. • The increased ability to use RAP decreases emissions associated with production of virgin materials.

  14. Improved Comfort and Safety of Workers

  15. No Smoke At Paver No Extreme Temperatures

  16. Improves Pavements

  17. Why will we have a Longer Life Pavement? • Less oxidation of mix • More uniformity of compaction • With fractionating RAP…better control of gradation

  18. Extends Resources by Recycling More

  19. High Percentage Recycle Mix with Standard Grade of Asphalt • Two deterrents to running recycle above 20% have been: • High Stack Temperature • Need for a softer virgin liquid to ensure compaction because of the stiffer liquid in the RAP

  20. Make High Percentage Recycle Mix with Standard Grade of Asphalt • To achieve compaction (density)…run 275oF and foam virgin liquid • By using a standard liquid 64-22, you produce a much softer product than with virgin mix because: • Lower temperature results in less oxidation • Light oil remains in liquid • Steam produced from drying the RAP creates an inert atmosphere

  21. Uses Less fuel

  22. Uses Less Fuel • Making Mix at 50 – 100 F Lower Temperatures than Traditional HMA Requires 11% to 25% Less Fuel (Depends on Mix Type and Other Conditions.)

  23. Increases Plant Production Capacity

  24. Increases Plant Production Capacity • Lower Exhaust Gas Temperatures and Less Fuel Burned Take Load Off of the Exhaust System.

  25. ASTEC Double Barrel Green System Equipment Explanation

  26. DOUBLE BARREL GREEN

  27. The Double Barrel Green System Injects Water Into Liquid Asphalt. • Injected At The Rate Of 2% Of The Liquid Asphalt By Weight • Small Faction Of The Injected Water Becomes Trapped As Steam Bubbles In The Liquid Asphalt • The Effect On The Mix Is To Extend The Workable Temperature Downward to about 212 F (100 C).

  28. WATER IS INJECTED INTO THE AC INSIDE THE FOAM NOZZLE.

  29. Steam Bubbles Produce Foamed AC.

  30. ? mm mm FOAM EXPANDS THE LIQUID ASPHALT AND INCREASES FILM THICKNESS

  31. THE SYSTEM CONSISTS OF: WATER TANK AND CONTROL SKID…..

  32. FOAM UNIT MOUNTED ON DOUBLE BARREL ….

  33. CONTROL SYSTEM

  34. Junction Box Water Solenoid Valve Water Manifold Water Hot Oil Out Hot Oil In AC AC Valve (one of nine) Nozzle Manifold

  35. LIQUID AC HOT OIL WATER FOAMED AC

  36. How much water ?

  37. How Much Water? 2% of liquid AC by weight 2 LBS. of Water for 1 Ton of Mix

  38. Case StudiesDone by National Center for Asphalt Technology • Created in 1986 • NAPA (National Asphalt Pavement Association) • Auburn University (Alabama) • Created to improve pavements • Test Track • 17,500 sq. ft.(1626 sq.m) laboratory

  39. Andrea Kvasnak, PhD • BS from University of Florida 1999 • MS from University of Vermont 2002 • PhD from Iowa State University 2006 Contact : ank0004@auburn.edu www.ncat.us

  40. Case Study 1 • Completed April 18, 2007 • Three foam mixes (2% H2O to AC): • 1. Base, 30% RAP • 2. Surface Coarse, virgin aggregate • 3. Surface Coarse, 30% RAP • Two locations at Astec HQ • Samples taken and tested by National Center for Asphalt Technology (NCAT)

  41. Case Study 2 • Completed June 21, 2007 • 50% RAP and PG 64-22 binder • 3400 ton job • Location: North Terrace Rd, Chattanooga, Tennessee • Samples taken and tested by National Center for Asphalt Technology (NCAT)

  42. Summary Conclusions of Cases 1 and 2 1.Coating and mixing of the warm mixes were equivalent to that expected for conventional hot mixes. 2.Workability of the warm mix at 250 F (121 C) to 270 F (132 C) was similar to that of hot mix at temperatures above 300 F (150 C). cont’d

  43. Summary (cont’d) 3. There was no smoke. 4. There was evidence that the warm mix was susceptible to stripping. This has been a characteristic of warm mix in general. One reason could be that the binder is not aged during mixing. Potential solutions include using a harder AC or an anti-strip agent.

  44. High profile demonstrations: • Southeastern Materials / City of Chattanooga, 3400 tons 50% RAP • Columbia Bit. (Vancouver), 100tons Virgin. • S.T. Wooten (Sims), 400tons, 20% and 40% • S.T. Wooten (Sims), 400tons, 40% • LoJac (Nashville), 1200tons, Virgin • Shelly Materials (Columbus), 1200tons, 25% • Boggs Materials (Rock Hill), 1200tons, 50% • Columbia Bit. (Vancouver), 1500tons, 50% • LoJac (Nashville), 500tons, 40%

  45. 7-26-07 to 7-28-07 Storage Test • Approximately 50 tons of mix made at 300 tph with 20% RAP at 138 C. • Stored for 24 hours and checked – all normal • Few tons of mix sold to a private customer. • No problems. Mix behaved normally. • Stored for another 24 hours (48 total) and emptied– all normal.

  46. Questions ?

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