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Asphalt Rubber Blending
By Jack Van Kirk
Director of Asphalt Technology
George Reed Inc.
CalAPA Fall ConferenceOctober 28 - 29, 20015Sacramento, CA
Asphalt Rubber Binder• How do you produce it?• Quality control?• Binder components?• How do you design it? • How do you test it?• Critical factors?
Asphalt Rubber Binder• Uses a minimum of 20 +/- 2 % crumb
rubber• Uses 10 mesh (2mm) crumb rubber• Reacts/interacts crumb rubber for a
minimum of 45 min. at elevated temperatures
• Modifies original properties of asphalt cement
Asphalt Rubber
Conventional or Modified Asphalt
How is Asphalt Rubber Produced?
• Specialized equipment and binder blended on-site
• High shear blender for mixing crumb rubber with asphalt
• Reaction tank with adequate agitation to assure proper reaction
• All materials are metered-in
Asphalt Rubber Blending Schematic
Crumb Rubber
Asphalt Storage Tank
Heat TankHigh Speed
Blender
Reaction Vessel
Binder Pumped to Plant
Rubber Weigh Hopper
Heater-Blender
Reaction Vessel
Reaction VesselAugers and
Direct Fire Heating
Binder Storage Vessel
Computer Controlled Metering
MPQP Requirements
High Shear Blender
Computer Controlled
Key is to have proper blending of components
Chip Seal
Plant Site Set-up
Quality Control
• Materials sampling and testing
• Field binder testing - hand held viscometer
Materials Sampling
• Components of the binder must be sampled and tested
• Asphalt rubber binder must be sampled from a point that will provide a representative sample
Quality Control/Quality Assurance
• QC- testing performed by contractor to ensure production is in control
• QA- testing performed to accept/reject the product
On-Site Qc for Asphalt Rubber Binder
Components of the Asphalt Rubber Binder• Crumb rubber modifier (CRM)• Asphalt cement• Asphalt modifier
Paving Asphalt
• PG 64-16 and PG 58-22 asphalt (80 +/- 2 %) (hot environments PG 70-10)
• Conform to Section 92 “Asphalts” of the Standard Specifications
Crumb Rubber Modifier (CRM)
• Scrap tire CRM (18 – 22 %)• Max. 0.01 % wire (by wt. Of
CRM)• Max. 0.05 % fabric (by wt. Of
CRM)• It must be a very clean rubber
Crumb Rubber
Laboratory Binder Design• Asphalt heated to 400 to 425°F• Asphalt modifier added to asphalt • Crumb rubber blended into asphalt/asphalt
modifier blend• Reacted for a minimum of 45 minutes• Agitated (stirred) frequently during reaction
period• Properties tested over 24 hour period
Compatibility of components
Binder ProfileTest 45
Minutes
60 Minutes
90 Minutes
120 Minutes
240 Minutes
360 Minutes
1440 Minutes
Viscosity @ 375°F
3600 3450 3100 2800 2200 2000 1800
Cone Penetration @ 77°F
30 34 32
Resilience, % Rebound @ 77°F
51 56 51
Softening Point, °F
166 165 163.5
Minimum reaction point
Typical Reaction Curve
Asphalt Rubber Binder Properties
• Cone penetration• Resilience• Field softening point• Viscosity
Cone Penetration
Resilience
Softening Point• Disc of asphalt material is
prepared• Ball bearing placed on top• Placed in water or glycol• Water heated up at a slow
constant rate• Softening point is temperature
at which ball falls through
Hand Held Viscometer• Haake/Rion viscometer or equivalent• Viscometer must be calibrated• Viscosity range 1500 - 4000 cp @ 375°F• Target viscosity: hot mix binder is about 2500 -
3500 cp, chip seal binder 1800 – 2200cp• Viscosity is a very good indicator of other
binder properties
Critical Factors Affecting Asphalt Rubber Binder
• Grade and source of base asphalt
• Amount of crumb rubber• Gradation of crumb rubber• Reaction time and temperature
Rubber particles in the binder help fight cracking
20 % CRM
HighViscosity
Current Use Asphalt Rubber Strategies
• Asphalt Rubber Hot Mix (Gap graded and open graded)
• Asphalt Rubber Chip Seal• Asphalt Rubber Cape Seal• Multi-Layer Systems
Properly blended binder
Good performing pavement strategy
Results in
Thank You