Mark Belshe, P.E.

Executive Director, Rubber Pavements Association

Santos, Brazil

August 14, 2013

Best Practices In Construction Of

Rubber Asphalt Pavements

Presentation Overview

Producing AR Mixes

Placing AR Mixes

AR Open Graded Mixes

Thermal Blanket

Benefits

Conclusions

Why Put Rubber In Asphalt?

Tire rubber is an engineering tool to:

Reduce cracking

Increase asphalt content and asphalt film thickness

Prevent bleeding, flushing, and drain-down

An aid to increase performance life

Save Money in reduced maintenance

Save money in project cost through reduced thickness

Increase safety and reduce noise

ASPHALT RUBBER

ASTM Definition D8-02, ASTM Standard D6114

An aerial view of a portable Asphalt-Rubber

Plant setup at a Hotplant. BLENDER

Hotplant

AR BLEND TANK

VIRGIN AC TANK RUBBER

STAGING AREA

Rubber is loaded into Weigh Hopper

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

Auger

Agitation Systems

Examples of Blending Equipment

Meter / Pump is interlocked with Hotplant

Construction Considerations

Control of temperature is most important

Handwork is more difficult

Material is stickier

Cold or wet weather

Considerable handwork

Long haul

Temperature considerations

Common Sense Best Practices

Tarp loads

Shorten windrows when paving with bellys

Keep rollers close

Weather forecast

– Wind

– Long range outlook

Nighttime temperatures

“Rubber picks up Rubber”

Some

Days

Are

Better

Than

Others

Don’t Confuse Performance with

Constructability

www.rubberpavements.org

A-R can be used anywhere

asphalt is used Just need at

least 13 C and

rising temps

and no rain.

PaveCool or MultiCool

50o, 15 mph wind, ½” – less than a minute

Use of Warm Mix Admixtures with

Rubberized Asphalt Mixtures Better Workability of the HotMix Allows

Compaction Aid for Stiffer Mixes

Longer Haul Times due to wider paving window.

Extension of the Paving Season/ Cold Weather Paving

Reduction in Production Temperatures Reduces Emissions

– Better Environment for Workers

– Reduce Blue Smoke / Odor complaints

– Reduce Recordable Emissions

Reduction in Energy Consumption

– Depending on mix it may be possible to save up to 30% on energy costs.

Drain Down test may need modification with additives

AR Open Graded

Overlays of PCCP

AR-ACFC Placed since

1980’s

Excellent in Retarding

Reflective Cracking

Restores Smoothness and

Skid Resistance

Noise Dampening – 4 to 6

decibels

AR Open Graded Materials

ADOT Specs 414

100% Passing 19 mm

Wet Process / Field

Blended

Binder Content–

approx 9% to 9.5%

High Voids – 18% or

more

Visibility

SAFETY

AR Open Graded Materials Nominal 19 mm Thickness

Conventional Laydown Equipment

Seasonal and Temperature Restrictions

Consequences

Change in Albedo of Significant Portion of Urban Fabric

Temperature Impacts of Underlying PCCP

Open Graded Friction Course over PCCP

Stresses Affecting Rigid Pavements

Combined effects of: – Repeated wheel loadings

– Varying temperature gradients

– Varying moisture gradients (Mohamed and Hansen, 1997; Bouzid and Mang, 1995)

Temperature-induced pavement responses more significant than traffic-induced responses (Mahboub et at, 2004)

Positive temperature gradient – Surface temperature greater than bottom

Curl and Warp Study 040215

0

20

40

60

80

100

120

140

160

0 2 4 6 8 10 12 14 16 18

Curl Influence Removed

IRI

Right IRI (in/mi)

Time (years)

Effects of Thermal Blanket

– due to the insulating effects, thermal

stresses within the PCCP are reduced

leading to a longer service life.

– beneficial porosity and lower thermal mass

of the AR-ACFC layer aided in releasing

heat at a faster rate at night time.

Obrigado