CHARACTERIZATION OF ASPHALT CEMENTS MODIFIED WITH CRUMBED RUBBER FROM DISCARDED TIRES. FINAL REPORT

The potential legislative requirement for incorporation of scrap rubber into asphalt blends mandated a thorough evaluation of the influence of scrap rubber additives on the physical properties and aging characteristics of rubber/asphalt blends. Blends with up to 20% ground vulcanized rubber (both crumb and 200 mesh powder particles) from recycled tires were prepared with asphalt cements of various grades (AC5 - AC30) and evaluated using dynamic mechanical analysis (DMA). Blends produced from powdered rubber particles exhibited Newtonian behavior at high temperatures; similar behavior was not observed with crumb rubber blends. The mechanical properties of asphalt-rubber blends depend upon the concentration of rubber additives, the particle dimensions, and the chemical composition of the asphalt. Some asphalts induced excessive swelling of the rubber particles, resulting in 135 deg C viscosities greater than Strategic Highway Research Program (SHRP) recommended 3 Pa-Sec. The dynamic mechanical characteristics of all blends are discussed in terms of G*sin delta and G"; comparative data are presented according to the new SHRP binder specifications. Constant stress creep and creep recovery of the polymer or rubber asphalt blends proved to be a sensitive measure of the additive content. Pressure Aging Vessel (PAV) aging of the asphalt rubber blends revealed a significant difference between crumb rubber and powdered rubber additives. Simple blends of crumb rubber with asphalts ranging in grade from AC5 to AC30 exhibited phase separation during the thin film oven aging test. In contrast, blends with powdered rubber appeared to remain compatible or at least partially compatible through the PAV aging process and the blends retained the physical properties associated with the additive. The DMA data suggest that the low temperature cracking resistance of asphalt/powdered rubber blends is enhanced.

  • Record URL:
  • Corporate Authors:

    Louisiana State University, Baton Rouge

    Department of Chemistry
    Baton Rouge, LA  United States  70803-1804

    Louisiana Department of Transportation and Development

    1201 Capitol Access Road, P.O. Box 94245
    Baton Rouge, LA  United States  70804-9245

    Federal Highway Administration

    1200 New Jersey Avenue, SE
    Washington, DC  United States  20590
  • Authors:
    • Daly, W H
    • Negulescu, I
  • Publication Date: 1994-11

Language

  • English

Media Info

  • Features: Figures; References; Tables;
  • Pagination: 65 p.

Subject/Index Terms

Filing Info

  • Accession Number: 00723818
  • Record Type: Publication
  • Report/Paper Numbers: FHWA/LA-95/291, LTRC Proj No. 92-1B
  • Files: TRIS, USDOT, STATEDOT
  • Created Date: Jul 12 1996 12:00AM