EFFECT OF MICROWAVE ENERGY ON THE PROPERTIES OF ASPHALT AND ITS USE AS AN AGING TOOL

Microwave energy causes changes in asphalt properties. Unsymmetric organic molecules with dipoles, that is, with a permanent separation of positive and negative charges, undergo excitational rotation when they are subjected to microwave radiation. The excitational rotation depends on the material's dielectric constant. Because the radiation frequency is relatively high and the dielectric constant of asphalt is low, asphalt molecules cannot rotate as fast as the applied electromagnetic field, and an out-of-phase component of the dielectric constant, called dielectric loss, is dissipated as heat. Treatment of asphalt for a short time with low-power microwave radiation decreases the dispersitivity (D) and molecular size index (MSI) values obtained by high-performance size exclusion chromatography (HPSEC). Alternately, exposure for a longer time to a higher-power radiation increased both the D and MSI values for 12 asphalts studied. Microwave conditions (power level, treatment time, sample weight, and sample container material) were tailored to simulate the effects obtained after rolling thin film oven-pressure aging vessel (RTFO-PAV) aging of 18 asphalts. HPSEC gave comparable results for the two aging techniques: RTFO-PAV aging versus microwave aging. The difference in MSI amounted to +/-7.3 and +/-4.2 percent by using gravimetry and ultraviolet detection at 345 nm, respectively. The bending beam rheometer showed that microwave energy underestimates aging by a maximum of about 3 deg C in the limiting low temperature. Accelerated aging by microwave radiation is very simple and consumes less than 3 hr.

• Record URL:
  http://onlinepubs.trb.org/Onlinepubs/trr/1995/1488/1488-001.pdf
• Record URL:
  https://scholar.google.com/scholar_lookup?title=EFFECT+OF+MICROWAVE+ENERGY+ON+THE+PROPERTIES+OF+ASPHALT+AND+ITS+USE+AS+AN+AGING+TOOL&author=S.+Bishara&author=R.+McReynolds&publication_year=1995
• Availability:
  • Find a library where document is available. Order URL: http://worldcat.org/issn/03611981
• Supplemental Notes:
  • This paper appears in Transportation Research Record No. 1488, Unmodified and Modified Asphalt Binders. Distribution, posting, or copying of this PDF is strictly prohibited without written permission of the Transportation Research Board of the National Academy of Sciences. Unless otherwise indicated, all materials in this PDF are copyrighted by the National Academy of Sciences. Copyright © National Academy of Sciences. All rights reserved
• Authors:
  • Bishara, Safwat W
  • McReynolds, R L
• Publication Date: 1995

Language

• English

Media Info

• Features: Figures; References; Tables;
• Pagination: p. 1-12
• Monograph Title: Unmodified and modified asphalt binders
• Serial:
  • Transportation Research Record
  • Issue Number: 1488
  • Publisher: Transportation Research Board
  • ISSN: 0361-1981

Subject/Index Terms

• TRT Terms: Accuracy; Aging (Materials); Asphalt; Dielectric properties; Microwaves; Productivity
• Uncontrolled Terms: Accelerated aging; Time savings
• Old TRIS Terms: Dispersitivity; High performance size exclusion chromatography; Microwave radiation; Molecular size index
• Subject Areas: Highways; Materials; I31: Bituminous Binders and Materials;

Filing Info

• Accession Number: 00714788
• Record Type: Publication
• Files: TRIS, TRB, ATRI
• Created Date: Nov 29 1995 12:00AM