Best Practices for Incorporating Recycled Asphalt Shingles

Report
RAS Best Practices
PAPA 54th Annual Paving Conference
Hershey, PA
January, 30th 2014
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RAS Best Practices
What is RAS?
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RAS Best Practices
Recycled Asphalt Shingles
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Types
2 types of roofing shingle scraps:
 Tear-offs generated during the demolition or
replacement of existing roofs
 Manufactured waste generated when new
asphalt shingles are trimmed during
production to the required physical
dimensions or from "out-of-spec" shingles
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Composition
Shingles typically contain:
 Asphalt binder
Tear-offs contain 20 – 40% binder
Manufacturer waste 18 – 22% binder
 40 to 60% hard rock granules and fillers
 1 to 12 % fiber, felt, and miscellaneous
materials
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Industry Guidance
NAPA IS 136: Guidelines for the Use of Reclaimed
Asphalt Shingles in Asphalt Pavements
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Where?
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Experience
 Incorporating RAS into HMA began more
than 30 years ago
 Pennsy Supply began using shingles in PA in
2002
 PennDOT currently only allows Manufactured
RAS, but may be considering allowing use of
Tear-Offs
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Environmental Concerns
 Similar concerns as for aggregate crushing,
RAP processing/crushing & HMA production
 Asbestos screening (if using tear-offs)
Must comply with local agency
requirements, which vary from state to state
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Environmental Benefits
 HMA mixtures produced with shingles are
100% recyclable
 Saves natural resources
 Saves landfill space
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Processing Shingles
 Various types of industrial grinders can be used
to grind the Shingles into a usable product
 Most use shredding approach
 Water is used during processing for dust suppression
and to aid in shredding, but must be controlled
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Processing Shingles
 Separate out the non-shingle debris before
incorporating into HMA
 Keep all non-shingle debris separated
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Processing Shingles
 Ensure proper sizing of the ground Shingle
particles
Finer is better
 Oversized Shingle particles impact:
Contribution to Pbe
Mat texture
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Processing Shingles
 Test RAS for gradation & AC Content
frequently as they are being shredded
 Keep RAS of different AC contents in
separate stockpiles
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Processing Shingles
Post-Processing
Pre-Processing
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Processing Shingles
 In some cases RAS is blended with a
carrier aggregate:
 Used to keep Shingles from
conglomerating & allows for more
efficient flow through cold feed bin
 RAP, 3/8” Stone, washed screenings,
Natural Sand can be used
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Storage
 Store RAS in covered environment to control
moisture
 Shingles left exposed to rain can have very
high moisture contents (12%+)
 RAS holds more moisture than RAP
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Plant
 Not always a best practice to keep the
shingles bin full
 Best practice to empty the shingles bin when
production complete or production is stopped
for extended period
Photo courtesy of Astec Industries
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Plant
 Ensure the RAS feed system is calibrated
and maintained
Photo courtesy of Astec Industries
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Plant
 Load cells or weigh belts measure the amount
of RAS as it is metered into plant
Photo courtesy of Gencor Industries
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Plant
 Watch for build-up at the RAP collar,
especially for plants with smaller throats
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Plant
 Consider covering conveyors and transfer
points
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Plant
 Test moisture content of RAS often while
incorporating into mix – even more frequently
if RAS stockpiles are not covered
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Plant
 RAS has been used successfully in batch
and drum facilities
 May need to increase dry & wet mix time in batch
plants
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Temperatures
Higher plant production temperatures may
be needed to ensure all moisture is removed
from RAS & to maximize blending of RAS
binder with virgin binder
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Temperatures
Higher plant production temperatures may
be needed to ensure all moisture is removed
from RAS & to maximize blending of RAS
binder with virgin binder
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Field
 RAS mixtures can behave differently than virgin
mixtures or RAP mixtures, which doesn’t
necessarily make them bad:
 RAS mixtures tend to be more sensitive to
fluctuations in production temperatures
 RAS mixtures are typically stiffer so may
require additional effort to compact
 RAS mixtures may make hand-work more
difficult , so think through paving sequence
before you begin paving
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Summary
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Shingles require processing
Need consistent stockpiles of RAS
Should cover stockpiles of RAS
Test gradation & moisture content of RAS often
RAS feed must be calibrated & controlled
Higher production temperatures may be needed
Be prepared to manage deltas in mix
characteristics when placing RAS mixtures
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Thank you
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