Asphalt Rubber Blending
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Presentation delivered by Jack Van Kirk at the CalAPA 2015 Fall Asphalt Pavement Conference Oct. 28-29 in Sacramento, CA.
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Asphalt Rubber Blending
- 1. Asphalt Rubber Blending By Jack Van Kirk Director of Asphalt Technology George Reed Inc. CalAPA Fall Conference October 28 - 29, 20015 Sacramento, CA
- 2. Asphalt Rubber Binder • How do you produce it? • Quality control? • Binder components? • How do you design it? • How do you test it? • Critical factors?
- 3. 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
- 5. 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
- 6. Asphalt Rubber Blending Schematic Crumb Rubber Asphalt Storage Tank Heat Tank High Speed Blender Reaction VesselBinder Pumped to Plant
- 10. Reaction Vessel Reaction Vessel Augers and Direct Fire Heating
- 12. Computer Controlled Metering MPQP Requirements
- 13. High Shear Blender Computer Controlled Key is to have proper blending of components
- 14. Chip Seal Plant Site Set-up
- 15. Quality Control • Materials sampling and testing • Field binder testing - hand held viscometer
- 16. 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
- 18. Quality Control/Quality Assurance • QC- testing performed by contractor to ensure production is in control • QA- testing performed to accept/reject the product
- 19. On-Site Qc for Asphalt Rubber Binder
- 20. Components of the Asphalt Rubber Binder • Crumb rubber modifier (CRM) • Asphalt cement • Asphalt modifier
- 21. 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
- 22. 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
- 23. Crumb Rubber
- 25. 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
- 26. Binder Profile Test 45 Minute s 60 Minute s 90 Minutes 120 Minutes 240 Minutes 360 Minutes 1440 Minutes Viscosity @ 375°F 3600 3450 3100 2800 2200 2000 1800 Cone Penetrati on @ 77°F 30 34 32 Resilience , % Rebound @ 77°F 51 56 51 Softening 166 165 163.5
- 27. Minimum reaction point Typical Reaction Curve
- 28. Asphalt Rubber Binder Properties • Cone penetration • Resilience • Field softening point • Viscosity
- 29. Cone Penetration
- 30. Resilience
- 31. 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
- 32. 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
- 34. Critical Factors Affecting Asphalt Rubber Binder • Grade and source of base asphalt • Amount of crumb rubber • Gradation of crumb rubber • Reaction time and temperature
- 36. Rubber particles in the binder help fight cracking
- 38. 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
- 39. Properly blended binder Good performing pavement strategy Results in
- 40. Thank You