best practices in construction of rubber asphalt pavements pr__ticas na...mark belshe, p.e....
TRANSCRIPT
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