DOUBLE BARREL GREEN SYSTEM

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

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

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GLOBAL WARMING
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WARM MIX TECHNOLOGIES

• ADDITIVES
• Aspha-Min
• WAM
• Evotherm
• Sasobit

• EQUIPMENT
• Double Barrel Green

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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.
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Outline

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

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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 1950s
• High fuel cost and pressure to reduce emissions
  make Warm Mix more attractive.

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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

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Improves Workability
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Reduces Emissions
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CONVENTIONAL HOT MIX
WARM MIX
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No Smoke No SmellWhy?

• 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

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Reduces total emissionsWhy?

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

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Improved Comfort and Safety of Workers
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No Smoke At Paver No Extreme Temperatures
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Improves Pavements
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Why will we have a Longer Life Pavement?

• Less oxidation of mix
• More uniformity of compaction
• With fractionating RAPbetter control of
  gradation

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Extends Resources by Recycling More
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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

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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

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Uses Less fuel
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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.)
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Increases Plant Production Capacity
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Increases Plant Production Capacity
Lower Exhaust Gas Temperatures and Less Fuel
Burned Take Load Off of the Exhaust System.
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ASTEC Double Barrel Green System Equipment
Explanation
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DOUBLE BARREL GREEN
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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).

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WATER IS INJECTED INTO THE AC INSIDE THE FOAM
NOZZLE.
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Steam Bubbles Produce Foamed AC.
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?
mm
mm
FOAM EXPANDS THE LIQUID ASPHALT AND INCREASES
FILM THICKNESS
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THE SYSTEM CONSISTS OF WATER TANK AND CONTROL
SKID..
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FOAM UNIT MOUNTED ON DOUBLE BARREL .
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CONTROL SYSTEM
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Junction Box
Water Solenoid Valve
Water Manifold
Water
Hot Oil Out
Hot Oil In
AC
AC Valve (one of nine)
Nozzle Manifold
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LIQUID AC
HOT OIL
WATER
FOAMED AC
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How much water ?
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How Much Water? 2 of liquid AC by weight 2
LBS. of Water for 1 Ton of Mix
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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

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Andrea Kvasnak, PhD

• BS from University of Florida 1999
• MS from University of Vermont 2002
• PhD from Iowa State University 2006

Contact ank0004_at_auburn.edu
www.ncat.us
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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)

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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)

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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).
• contd

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Summary (contd)
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.
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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

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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.

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Questions ?
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