Sustainable Streets for Chicagoland… CDOT’s Green Pavement Initiatives
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Transcript of Sustainable Streets for Chicagoland… CDOT’s Green Pavement Initiatives
Sustainable Streets for Chicagoland…
CDOT’s Green Pavement InitiativesCindy Williams
Quality Assurance Manager, CDOTJune 17, 2009
Typical Conventional Roadway Design for CDOT
• Sub-base granular material (non-recycled)
• Portland Cement Concrete (PCC) base course
• Hot Mix Asphalt (HMA) overlay w/ RAP– Urban environment allows RAP
Initiatives Taken by CDOT• Permeable Pavements
– Concrete– Hot Mix Asphalt
• Ground Tire Rubber (GTR)• Higher % Recycle Content
– RAP– Crushed Concrete
• Warm Mix Asphalt (WMA)
What We’ve Learned
Unique Attributes in Construction w/ Pervious PCC• Training - specify• Material
– No internal vibration– Unit wt vs. slump/air– Susceptible to temperature
(?)• Placing / Finishing Equipment• Curing Critical• Maintenance / Cleaning
Revisiting Pervious in 2009• Revising Mix proportioning
– Blending coarse aggregates– Cementitious Amounts / Type– Unit weights - relation to strength &
permeability
• Testing & Acceptance
• Modified Construction Techniques
Modified Construction Methods
Key Mixture Considerations regarding Pervious HMA
• Followed knowledge base on open-graded / SMA mixes
• Wanted to limit plant modifications to urban producers (fibers)
• Trial Blends with liquid AC options– Polymer, NO Fibers (drain down issues)– GTR modified, NO Fibers (as – built)
WHY GTR liquid AC?• Other agencies were on board• Cook County GTR Task Force
– CDOT– IDOT – IL Tollway
• Willing to try it
Pro’s to using GTR liquid AC• Limited - No Cost Implications
– No Fibers– No plant modifications
• Environmental goodness– 1 tire / 1 ton
• Terminal Blended = easy to use• Polymer Equivalent Liquid
(PG 64-22 + GTR)
Unique Attributesin Construction w/ GTR
• Plant– Silo storage
• Field– Stability
• Min / Max Lifts– Rollers– Temperatures
• Maintenance / Cleaning
8” Pervious HMA
(4” + 2” + 2”)
Monitoring Pervious Applications
• 2 yr program • Rutting• Raveling• Permeability• Albedo
What we learned…maintenance is the key!
High Recycle HMA
• Low ESAL / N30 Surface Mix
• 40% RAP• 10-15% Recycled PCC• 2nd season added GTR• CDOT In-House Crews
Why Higher Recycle Content
Mix?
WMA - How it came to be...
• Made sense with ongoing green initiatives within CDOT
• Tollway willing to try, coordinated our efforts (both trials same week)
• No additional cost to CDOT– Thank you Meadwestvaco, Ogden
Materials/Bigane Paving, S.T.A.T.E. Testing and the Tollway
Pro’s to WMA• Minor Plant Modification
– Evotherm technology
• Produced at 230˚ F• Placed from 230˚ - 180˚ F• Same rolling pattern• No difference in workability• Reduced odor, fumes• Reduced fuel / energy• Potential to extend season
Future Initiatives for CDOT• Recycled PCC
– Back into PCC– Clean, sub-base material
• Recycled “wash H20”
• FRAP, WMA + GTR• Modified Pervious Apps• Cement alternatives• Recycled shingles in HMA
What’s holding us back?• Time• Money
– Develop– Implement– Evaluate performance
• Types of projects / programs willing to try (satisfying funding partners)
• Knowledge base / method to implementation
No-brainers to Green YOUR Hardscape
• Maximize RAP/FRAP in your HMA• Increasing recycled cementitious contents• GTR modified HMA designs• Increase Pervious Surfaces where
opportunities exist• Other unique opportunities…
THE END