Asphalt Rubber Blending

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