session w62 using reclaimed asphalt shingles (ras) in ...€¦ · using reclaimed asphalt shingles...
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Using Reclaimed Asphalt Shingles (RAS) in Asphalt Pavement Mixtures
Operations and Specifications
Victor (Lee) Gallivan FHWA- Office of Asset Management,
Pavement and Construction March 5, 2014
Session W62
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Outline
• Operational Considerations • Processing, Plant, Laydown,
Compaction, and Design • AASHTO Reclaimed Asphalt
Shingles Material Revisions • NAPA Statistics- 2012
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• Small size – Finer is better
• Process in winter – Better than summer – Especially for Manufacturer Waste
Processing Considerations
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Previous Grind Specification
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New Finer Grind
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• Limit water use during processing – Higher the water content allows
faster processing – Limiting water constrains processing
rate
Processing Moisture Content
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• Moisture Limits Maximum Plant Production Rate
• Extra fuel to evaporate water
• 8% Moisture Maximum
Set Maximum Moisture Desired
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• Once shingles get wet – They stay wet
• Stockpiles don’t “drain” • Maximum Moisture Content
– 15% to 25% – Depending on environment
Maintain Moisture Content
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• Keep under cover (tent structure)
• Don’t fill to ceiling – Allow airflow – Stockpiles will
dry slowly
Maintain Moisture Content
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• Use shingle shredding equipment – No wood
mulchers
Processing Size
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• Use trommel screen – 3/8 inch – ¼ inch?
Processing Size
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• Can blend with sand or RAP • Yes
• BUT NO BUCKET BLENDING
Sand or RAP Addition
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• Must use feeder bins when building stockpile – Obtain homogenous blend
Blending is Separate Operation
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• Very fine black dust – Asphalt and fiberglass
• Irritant – Makes you itch
• Safety – Breathing protection
Processing Dust
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• Can use aggregate feeder – Difficulty feeding 3%
• Feed must be UNIFORM
Feeding Shingles
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• If gate height setting too low – Won’t feed through opening – Tends to plug
• If gate height setting too high – Belt speed too low – Difficult to control
Feeding Shingles
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• Use front end loader • “Fluff” shingles into feeder
– Don’t just dump in • Keep amount in feeder low
– Filling allows compaction – Won’t feed properly
• Empty feeder when not in use – RAS tends to “set up” in feeder
Loading Cold Feed
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• Shingles need separate weigh bridge – Otherwise feed rate is “assumed”
based on bin feeder calibration • Need lower range load cell
– Aggregate 300 to 500 tons per hour – Shingles 5 to 25 tons per hour
Weigh Bridge
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• Depending on plant location
• During windy conditions – Thin
“cellophane-like” plastic blows off
– Fine (black dust) blows off
Cover Feed Belts
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• No difference from regular mix
• Can store for longer than a day
Silo Storage
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• No difference • Fibers don’t
“cure” segregation – Still need
three dumps and other good practices
Trucking
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• No change – Direct feeding to hopper – Shuttle buggy – Windrow pickup machines
Feeding into Paver
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• Hot Mix Handwork – Mix is stiffer to handle – Still workable
• Foamed Warm Mix – High (5% ) shingles make mix too
stiff to handwork easily
Workability
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• Mix is more stable – Tenderness is less of problem
• Keep rolling patterns tight – Breakdown rollers tight to paver
Compaction
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Courtesy of Bruce Christianson - Alaska
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• Handling in Laboratory • Batching specimens • Making specimens
Design Considerations
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• Need accurate value for shingles • Use AASHTO T209 • How to handle “Floaters”
– Add hot (180°F) water when adding water to picnometer
– Need to cool to 77°F for vacuum saturation
Maximum Theoretical Gravity (Gmm)
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77° F Water
180° F Water
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• Calculate from Gmm test • Use for VMA calculations
– Error of using Gse instead of Gsb is acceptable
• Allow for asphalt content – 5% shingles is NOT 5% aggregate – Use aggregate contribution in VMA
calculation
Use Aggregate Effective Specific Gravity
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• Two methods – “Dipping” – Splitting
• “The shingles are fine enough we don’t need to split them down in the lab”
• WRONG
Batching Specimens
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• Dry shake to get apparent RAS gradation • Split shingles into
– +3/8 – +#4 – +#8 – +#16 – +#30 – -#30
Handling Shingles in Lab
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• Batch according to apparent gradation
• WHY? – High asphalt content of shingles
makes errors greater – Lot of material on +#30 sieve
Handling Shingles in Lab
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• Three samples of each
• Dipping – Scoop out of pan of dried shingles
• Batching – Break down and batch according to
apparent gradation
Dipping vs Batching
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Dipping Batching Asphalt Content Average 26.32% 26.66% Std Deviation 1.13% 0.53%
Minus #200 Average 27.2% 29.0% Std Deviation 2.3% 0.7%
Dipping vs Batching
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• Bulk Specific Gravity – Range of 0.010
Gyratory Pills
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Reclaimed Asphalt Shingles (RAS) Industry Guidance
CDRA NAPA
Construction & Demolition Recycling Association (CDRA)
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STANDARDS
• M323 Modifications; Binder replacement revisions for RAP and/or RAS (part 1 completed)
• MP15/PP53 Modifications regarding RAS (completed and submitted to AASHTO)
• Development of Technical Information on Shingles to replace the existing standards
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MP 15- Specifications
OLD • Grind Size: 100 percent
passes the 12.5-mm (0.5-in.) sieve
• Rates of RAS additions • Deleterious Substances
3% of mass and Non-Metallic 1.5%
• Reference Documents and Terminology
NEW • Grind Size reduced to 100
percent passes the 9.5 mm (3/8-in.) sieve
• Deleted –moved to PP53 • Deleterious Criteria
reduced to: 1% of mass and Non-Metallic reduced to 0.5%
• Reference Documents and Terminology updated
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PP 53- Practice
OLD • Shingle Binder
Availability Factor Given 0.70
• Binder Grade Determinations
• Instructions only referred to RAS
• Binder Grade Adjustments Left Open
NEW • Corrected SAF process
Range from 0.70 to 0.85 to be calculated
• BGD process revised
• New Equations for RAS and RAS+RAP
• New Table 1 included Guidelines on when to adjust (see next slide)
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PP53, Table 1—Binder Grade Adjustment Guidelines for Mixtures with Reclaimed Asphalt Shingles (RAS) - the percentage of available shingle binder and RAP binder in the design asphalt binder
Binder Grade w/RAS or RAS+RAP No Change in Virgin Binder Selection <15 % Select Virgin Binder Grade, one grade
softer >15% to <25%
Blending Chart Recommendations ≥25
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Numbering
OLD • Provisional
Standards • MP15 – 06(09) and PP53 – 06(09) Both To be replaced
NEW
• New Provisional Standards
• MP XX (14) and PP XX (14) (XX- TBD)
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ASTM Shingles Effort
• Nazli Yesiller, [email protected] Chair: D18:14 • “We are in the process of preparing the
next version of the specification for ballot. It will be very similar to the AASHTO Version”
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NAPA/FHWA 2012 Survey of Recycled
Materials Usage
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NAPA WEBSITE: www.asphaltpavement.org
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NAPA -RAP, RAS, WMA Usage Survey
• RAP usage 68.3 Million Tons = +22%
• RAS usage 1.9 Million Tons = +56%
• WMA usage 86.7 Million Tons = +26%
• Overall of RAP Usage 19.6% = +3%
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RAS Usage in HMA/WMA
701 thousand
tons
1,099 thousand
tons
0200400600800
1,0001,2001,4001,600
2009 2010 2011 20121,192
thousand tons
1.893 Thousand
Tons
Total asphalt mix: 358.4 359.8 366.0 (million tons)
Total RAS tons used for mix production
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2011 Average RAP Content by State
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2011 RAS Reported Usage by State (33 Yes’s)
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Victor (Lee) Gallivan, PE Recycled Material Program Coordinator
[email protected] Ph: 317-226-7493 Cl: 317-605-4704
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