Kyle MooreGranite Construction

Phone: 760) 775-7500Email:

kyle.moore@gcinc.com

Best Practices For Placement of Asphalt-Rubber Pavements

Presentation Overview

• Design Considerations from Contractor’s Perspective

• Field Production of AR Binders• Issues with Field Blending

Processes• Performance of AR Mixes• Conclusions

Asphalt Rubber History• Developed in 1960’s by City of

Phoenix Engineer• Referred to as the “wet process” or

McDonald Process• Large amount of crumb rubber used

as a Binder Modifier• Needs constant agitation

Asphalt Rubber80 % Asphalt

20 % Ground Tire Rubber

PRODUCTS AND PROCESSES IN THE PUBLIC DOMAIN

Minus No. 10 mesh is used; free of wire and other

contaminants; up to 0.5%

fiber.

Crumb rubber

Ground tire rubber is typically received in 2,000 pound “Supersacks”.

Virgin Asphalt

Cement Tank

Crumb Rubber Hopper Blender

Asphalt Rubber blend Tank

Auger

Agitation Systems

Maintaining Heat and Agitation is Key

Rubber Is Loaded into Weigh Hopper

The Rubber is weighed by the Hopper’s load cells.

An aerial view of a portable Asphalt-RubberPlant setup at a Hotplant.

BLENDER

Hotplant

AR BLEND TANK

VIRGIN AC TANKRUBBER STAGING AREA

Meter / Pump is interlocked with Hotplant

Rotational viscosity test - “Haake” Test

SOME CONCERNS WITH FIELD BLENDING PROCESSES

• Limited Production Rate for hotplant• High Shear Blenders allow higher

production• Sustainable rate of production is

usually between 20 and 30 liquid tons per hour

• Elevated heat at plant - safety• End of project cleanout

AR Paving is done with conventional paving techniques.

• Virgin Asphalt Temp: >375° F• Binder Temperature: 375 ° - 425° F• Aggregate Temperature: <325° F• Breakdown Roller: 290 ° F• Ambient/Surface Temp: >55°F RHMA-G

Successful AR Production is about Heat Management

PLACING AC WITH AR BINDERS

• Don’t pave in the cold but AR performs well in the cold

• No use of pneumatic rollers– “Rubber picks up Rubber”

• Elevated mix temperature is not solution

• Use of limewater in some areas

Asphalt Rubber mixes for applications requiring hand work requires attention to detail.

Issues to consider

Contractor’s Cost Issues• Small Projects = Larger UNIT Costs

– Fixed mobilization– Fixed daily costs

• Rubber Plant may limit Production Rate

Asphalt Rubber Myths• The Contractor needs

specialized equipment• Viscosity testing

procedure is standardized

• Blend Design consistency

• Nuclear Oven Results variability

Some Days Are

Better Than

Others

When It All Goes Wrong

• Plant Breakdowns

• Limited Shelf Life

• Last Day Cutoff

Elements of a successful AR Project

• Experienced Binder Designer• Experienced Mix Designer• Blender / Hot Plant Compatibility

(Electronics)• On-site contractor quality control• Knowledgeable Agency inspection• Common Sense

Common Sense Best Practices• Tarp loads• Shorten windrows when paving with

bellys• Keep rollers close• Weather forecast

– Wind– Long range outlook

• Nighttime temperatures

Constructability vs. Performance

Performance in Indio, CA

Asphalt-Rubber Asphaltic Concrete offers excellentcolor contrast for striping and marking.

The Environmental Card

Lincoln, Nebraska

Interstate 10 near Odessa, Texas

CONCLUSIONS

AR mixes resist reflective crackingGap graded and open graded mixes

perform wellConstructability and unique field

issues must be dealt withUpfront costs hamper widespread

usageNoise mitigation may be part of future

Summary• Asphalt Rubber is

construction friendly

• AR is quiet, smooth, long lasting and an environmental winner

Questions?

“I know you believe you understand what you think I said, but I am not sure you realize that what you heard is not what I meant.”

---Alan Greenspan