Post on 05-Jan-2016
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AAPA 2010 Study Tour – WMA RAP
Warm Mix Asphalt&
Recycled Asphalt Pavements
Cassandra Simpson | Greg Stephenson Robert Patience | Rick Hennig
AAPA 2010 Study Tour – WMA RAP
Background to US Mixes
• Virgin Source Aggregateso “Combined” Grading (eg passing ½” retained ¼”)oMore Variability in US Virgin Mixes
• Fractionated RAP (Single Size)o Reduces Variability in Final MixoMore Important at High Percentages of RAPo Helps in Design of High RAP Mixes
AAPA 2010 Study Tour – WMA RAP
Background to US Mixes
Who owns the RAPand
What are they doingwith it????
AAPA 2010 Study Tour – WMA RAP4
Green Highway Partnership Major Partners: EPA, FHWA, and MD SHA
• Integrates transportation functionality and ecological sustainability
• Green Highways are:o Built with permeable materialso Constructed with recycled materialso Designed using cutting edge technologies to
protect habitats & ecosystems
www.greenhighways.orgwww.greenhighways.org
AAPA 2010 Study Tour – WMA RAP
Advantages of Recycling
• Stabilise Cost• More Consistent Material (Fractionated RAP)• Environmentally Responsible• High Quality Material
o RAP is Old Material?!• Rocks in S. California ~14 million years• Bitumen ~10 to 200 million years
o Still high quality aggregate.o Bitumen is still coating the aggregate.
AAPA 2010 Study Tour – WMA RAP
Advantages of Warm Mix Asphalt
• Improved working conditions• Less fumes and emissions• Less energy consumption• Decreased binder ageing during production
o Reduced temperature allows more RAP?
• Is Warm Mix the Future for Asphalt?• 100% of production could be WMA in the
future with up to 50% WMA within 5 years
AAPA 2010 Study Tour – WMA RAP
WMA + RAP - BenefitsWMA + RAP - Benefits
• Production (temperature)• Product (aggregate and binder)
o Aged binder in RAP• Works as an anti-stripping agent• Improves TSR values
• Environmental (recycle, landfill, etc)
www.aapa.asn.au
AAPA 2010 Study Tour – WMA RAP
States That Have Tried WMA & Higher RAP
AAPA 2010 Study Tour – WMA RAP
RAP and WMA
• Lower mixing temperature resulted in less oxidation & light oil remaining in virgin bitumen
• Steam produced from drying RAP creates inert atmosphere
• Recovered binder from WMA with 25% RAP has same rheological properties as recovered binder from HMA with virgin bitumen
AAPA 2010 Study Tour – WMA RAP
Specified Binder 58-2825% RAP
AAPA 2010 Study Tour – WMA RAP
RAP and WMA
• Will RAP and New Binders Mix at WMA Process Temperatures?o Co-mingled binder properties?
• Interfacial Mixing Studyo Atomic Force Microscope
• Lab Mixing Studieso Dynamic Modulus Evaluation
AAPA 2010 Study Tour – WMA RAP
NCHRP 9-43 - Sasobit
10
100
1000
10000
39.2
F, 1
0 Hz
39.2
F, 1
Hz
39.2
F, 0
.1 H
z
68 F
, 10
Hz
68 F
, 1 H
z
68 F
, 0.1
Hz
95 F
, 10
Hz
95 F
, 1 H
z
95 F
, 0.1
Hz
Testing Condition
Dy
na
mic
Mo
du
lus
, k
si
Measured Estimated for Complete Mixing
AAPA 2010 Study Tour – WMA RAP
WMA + RAP - US Practices
• Texas DoT – 33%-50% of all WMA work contain RAP
• North Carolina (Boggs) – only use WMA with RAP (15-20%)
• South Carolina (Banks) – view RAP inclusion as insurance
• California (Granite) – a means of achieving a similar binder to that of hotmix
AAPA 2010 Study Tour – WMA RAP
Superpave Guidelines
• Guidelines for hotmix and potential guidelines for WMA + RAP
• Tier 1: Up to 15% RAP (25% for WMA)o use specified binder grade
• Tier 2: 15%-25% RAP (25% - 35% for WMA)o use one full binder grade lower
• Tier 3: Over 25% RAP (>35% for WMA)o use blending charts to determine required binder
grade
AAPA 2010 Study Tour – WMA RAP
Determining Blended Binder Grade
AAPA 2010 Study Tour – WMA RAP
Production and Paving Notes
• Work to minimize aggregate moisture.• Make sure the burner is tuned for the
temperature.• Keep bag-house temperature above
condensation point - higher % RAP in WMA helped increase temperature of bag house.
• Consider superheating aggregate ahead of RAP.
• Follow normal placement practices.
AAPA 2010 Study Tour – WMA RAP
• Short Term Ageing of WMA Binders During Production (laboratory ageing protocols)*
• Differences Between Field Produced WMA and HMA Volumetric Properties
• Increased RAP Usage with WMA*• Shingle Use with WMA*• Rubber Use with WMA*• More to come …??
Future National Research?
AAPA 2010 Study Tour – WMA RAP
1818
High RAP Mix DesignHigh RAP Mix Design
• NCHRP 9-46 Mix Design and Evaluation Procedure for High Reclaimed Asphalt Pavement Content in Hot Mix Asphalt
• Objective: Develop mix design method and specification for HMA containing up to 50% RAP.
AAPA 2010 Study Tour – WMA RAP
Questions?