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California Asphalt Rubber Case Studies – Reduced Thickness

California Asphalt Rubber Case Studies – Reduced Thickness . Jack Van Kirk Basic Resources. Presentation Outline. What is Asphalt Rubber Where has it been used successfully Caltrans reduced thickness design guidelines and supporting research Cost-effective strategies

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California Asphalt Rubber Case Studies – Reduced Thickness

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  1. California Asphalt Rubber Case Studies – Reduced Thickness Jack Van Kirk Basic Resources

  2. Presentation Outline • What is Asphalt Rubber • Where has it been used successfully • Caltrans reduced thickness design guidelines and supporting research • Cost-effective strategies • Advantages of asphalt rubber

  3. Definition of Asphalt Rubber • Uses a minimum of 20 +/- 2 % crumb rubber • Uses 2mm size crumb rubber • Reacts/interacts crumb rubber for a minimum of 45 min. at elevated temperatures • Modifies original properties of asphalt cement

  4. Crumb Rubber Modifier

  5. Ground tire rubber is received in 2,000 pound “Supersacks”.

  6. Current UseAsphalt Rubber Strategies • Asphalt Rubber Hot Mix (ARHM) • Asphalt Rubber Chip Seal • Asphalt Rubber Cape Seal • Multi-Layer Systems

  7. Where have Asphalt Rubber strategies been used successfully?

  8. Caltrans Reduced Thickness Design Guideline • Caltrans developed the guidelines in 1992 • Based on laboratory and long-term field data (two decades) • Supported by research efforts

  9. Design of Asphalt Rubber Pavements • Uses a deflection based design method • Up to 50 % reduction in thickness compared to conventional AC design thickness • Over 1000 reduced thickness projects

  10. Structural Equivalencies Thickness (mm) DGAC ARHM-GG ARHM-GG on a SAMI 45 30 -- 60 30 -- 75 45 30 90 45 45

  11. Ravendale Project • First project to use reduced thickness Asphalt Rubber pavements when compared to the conventional AC design thickness • Different thickness test sections of Asphalt Rubber and conventional AC mixes were placed for comparison

  12. 75mm 45mm 45mm 45mm 75mm 45,60,75,150mm

  13. 45mm AR over SAMI 16 yrs old

  14. 45mm AR over SAMI 16 yrs old

  15. 75mm AR over SAMI 16 yrs old

  16. 75mm AR over SAMI 16 yrs old

  17. Council On Scientific and Industrial Research (CSIR) • Caltrans conducted a research project with CSIR, UCB, and Dynatest Consulting to verify the reduced thickness theory for Asphalt Rubber pavements • The research used accelerated pavement testing (APT) using the heavy vehicle simulator (HVS) • The research included laboratory testing to support the field testing

  18. Original condition of pavement in South Africa

  19. 75 mm Conv. AC 25 mm ARHM 38 mm ARHM

  20. Repetitions Wheel Load AC Overlay Section (75mm) ARHM-GG Section (38mm) ARHM-GG Section (25mm) 0-100,000 40kN Fine cracks at 100,000 __ __ 100,000 to 175,000 40kN Block cracks at 175,000 __ __ Wheel load Changed to 80 kN 175,000 to 200,000 80kN Completely cracked __ Fine cracks 200,000 to 237,000 80kN Test stopped __ Completely cracked Surface Temperature Reduced to –5 C 237,000 to 250,000 80kN Test stopped 1/2 of section cracked Test stopped Performance

  21. Supporting Research • UAF (Raad) -Conducted laboratory beam fatigue testing of ARHM-GG and conventional DGAC and concluded that ARHM-GG had significant improvement in fatigue properties • OSU (Hicks) and UNR (Epps) - Conducted life cycle cost analysis and concluded that Asphalt Rubber was more cost-effective when compared to conventional AC pavement maintenance and rehabilitation strategies

  22. Asphalt Rubber 3-Layer Systems • Asphalt Rubber binder used in hot mix and chip seals can be used in different thin layer systems • These systems can save hundreds of thousands of dollars when compared to full reconstruction using conventional strategies

  23. AsphaltRubber SAMI • Caltrans conducted field trials using Asphalt Rubber stress absorbing membrane interlayers (SAMI) • In 1991 Caltrans concluded that SAMI’s in AC overlays of AC pavements with aggregate base are equivalent to approximately 52mm of AC in retarding initial cracking

  24. Randolph AvenueCosta Mesa, CA

  25. 10 years old 37mm ARHM-GG ARCS 25mm AC

  26. Philadelphia StreetWhittier, CA

  27. 10 years old 37mm ARHM-GG ARCS 25mm AC

  28. Thin Asphalt Rubber Overlays Los Angeles, CA

  29. 25mm ARHM-GG 1 year old

  30. 5 years old

  31. 10 years old

  32. Advantages of Asphalt Rubber Binder • Significantly higher binder contents - 20 % higher in dense graded mixes - 40 - 50 % higher in gap graded mixes - 50 - 60 % higher in open graded mixes • Thicker film thickness • Reduced oxidation • Increased durability • Increased resistance to reflective cracking

  33. Advantages of Asphalt Rubber Pavement Strategies • More abrasion resistant • Reduced oxidation • Increased fatigue resistance • Can reduce thickness • Reduced construction time/Increased safety • Savings in energy and natural resources • Lower maintenance cost

  34. Why choose Asphalt Rubber strategies? • Has a long term performance history (over 30 years) • Over 1000 successful reduced thickness projects • Proven alternative to costly reconstruction • Established life cycle cost-effectiveness

  35. Asphalt Rubber = Performance Thank you!

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