Transcript Document

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
– And building a better, long-lasting
pavement
GLOBAL
WARMING
WARM MIX TECHNOLOGIES
ADDITIVES
EQUIPMENT
Aspha-Min
WAM
Evotherm
Sasobit
Double Barrel Green
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.
Outline
• Background and Benefits of
Warm Mix
• Equipment Explanation
• Case Studies
• Experience to Date
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.
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
Improves Workability
Reduces Emissions
CONVENTIONAL
HOT MIX
WARM MIX
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
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.
Improved Comfort and Safety of Workers
No Smoke At Paver
No Extreme Temperatures
Improves Pavements
Why will we have a
Longer Life Pavement?
• Less oxidation of mix
• More uniformity of compaction
• With fractionating RAP…better control
of gradation
Extends Resources by Recycling More
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
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
Uses Less fuel
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.)
Increases Plant Production Capacity
Increases Plant Production Capacity
Lower Exhaust Gas Temperatures and
Less Fuel Burned Take Load Off of the
Exhaust System.
ASTEC Double Barrel Green System
Equipment Explanation
DOUBLE BARREL GREEN
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).
WATER IS INJECTED INTO THE AC INSIDE THE FOAM NOZZLE.
Steam Bubbles Produce Foamed AC.
mm
?
FOAM EXPANDS THE LIQUID ASPHALT
AND INCREASES FILM THICKNESS
mm
THE SYSTEM CONSISTS
OF:
WATER TANK AND
CONTROL SKID…..
FOAM UNIT MOUNTED
ON DOUBLE BARREL ….
CONTROL SYSTEM
Junction
Box
Water Solenoid
Valve
Water
Manifold
Water
AC Valve (one
of nine)
AC
Nozzle Manifold
LIQUID AC
HOT OIL
WATER
FOAMED AC
How much water ?
How Much Water?
2% of liquid AC by weight
2 LBS. of Water for 1 Ton of Mix
Case Studies
Done 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
Andrea Kvasnak, PhD
• BS from University of Florida 1999
• MS from University of Vermont 2002
• PhD from Iowa State University 2006
Contact : [email protected]
www.ncat.us
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)
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)
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
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.
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%
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.
Questions ?