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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. 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.

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

Aspha-Min

WAM

Evotherm

Sasobit

EQUIPMENT

Double Barrel Green

WARM MIX TECHNOLOGIES


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
Outline

  • Background and Benefits of Warm Mix

  • Equipment Explanation

  • Case Studies

  • Experience to Date


Background
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
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




CONVENTIONAL

HOT MIX

WARM MIX


No smoke no smell why
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
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.



No Smoke At Paver

No Extreme Temperatures



Why will we have a longer life pavement
Why will we have a Longer Life Pavement?

  • Less oxidation of mix

  • More uniformity of compaction

  • With fractionating RAP…better control of gradation



High percentage recycle mix with standard grade of asphalt
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
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 Asphalt

  • 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 Asphalt

  • Lower Exhaust Gas Temperatures and Less Fuel Burned Take Load Off of the Exhaust System.


ASTEC Double Barrel Green System Asphalt

Equipment Explanation



The double barrel green system injects water into liquid asphalt
The Double Barrel Green System AsphaltInjects 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).




?

mm

mm

FOAM EXPANDS THE LIQUID ASPHALT

AND INCREASES FILM THICKNESS


THE SYSTEM CONSISTS

OF:

WATER TANK AND

CONTROL SKID…..


FOAM UNIT MOUNTED

ON DOUBLE BARREL ….



Junction Box

Water Solenoid Valve

Water Manifold

Water

Hot Oil Out

Hot Oil In

AC

AC Valve (one of nine)

Nozzle Manifold


LIQUID AC

HOT OIL

WATER

FOAMED AC



How Much Water?

2% of liquid AC by weight

2 LBS. of Water for 1 Ton of Mix


Case studies done by
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
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
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
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
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
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
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
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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