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