EFFECT OF GAMMA RADIATION ON PAVING ASPHALTS

THIS STUDY WAS A LIMITED FEASIBILITY STUDY TO DETERMINE IF GAMMA RADIATION COULD BE USED TO IMPROVE THE ENGINEERING PROPERTIES OF PAVING ASPHALTS. TWO ASPHALTS, DIFFERING WIDELY IN CHEMICAL AND PHYSICAL PROPERTIES, WERE SUBJECTED TO GAMMA RADIATION FROM A COBALT 60 SOURCE. THE TEST SAMPLES WERE EXPOSED TO RADIATION AT BOTH AMBIENT (CA. 125 DEGREE F) AND ELEVATED TEMPERATURES (194 DEGREE F AND 360 DEGREE F). AT AMBIENT CONDITIONS GAMMA DOSAGES WERE 106 TO 108 RADS AND AT ELEVATED TEMPERATURES DOSAGES WERE 108 AND 109 RADS. IRRADIATION AT AMBIENT TEMPERATURES PRODUCED MINIMAL TO MODERATE CHANGES IN PHYSICAL AND CHEMICAL PROPERTIES AT THE GAMMA DOSAGES USED. PENETRATION, VISCOSITY, AND SOFTENING POINT INCREASED MODERATELY WHILE TEMPERATURE-SUSCEPTIBILITY AND STIFFNESS DECREASED SLIGHTLY. ACID PRECIPITATION ANALYSIS, INFRARED ANALYSIS AND MOLECULAR WEIGHT MEASUREMENTS INDICATED CORRESPONDING CHANGES IN CHEMICAL PROPERTIES. THESE CHANGES INDICATED A BUILDUP OF LARGER MOLECULAR CONSTITUENTS AT THE EXPENSE OF PARAFFINIC AND NAPHTHENIC HYDROCARBONS. IRRADIATION AT ELEVATED TEMPERATURES PRODUCED CHANGES SIMILAR TO THOSE PRODUCED AT AMBIENT IRRIDIATION, BUT TO A GREATER DEGREE. HOWEVER THE HARDENING, AS EVIDENCED BY INCREASED VISCOSITY AND DECREASED PENETRATION, MORE THAN OFFSET THE BENEFICIAL EFFECTS INDICATED BY LOWER PENETRATION INDEX, TEMPERATURE-SUSCEPTIBILITY AND STIFFNESS. ON THE BASIS OF THE RESULTS OBTAINED, IT WAS CONCLUDED THAT SIGNIFICANT IMPROVEMENT IN THE ENGINEERING PROPERTIES BY GAMMA RADIATION METHODS IS NOT A LIKELY PROSPECT. ANY FUTURE WORK, IF UNDERTAKEN, SHOULD BE DIRECTED TOWARD EVALUATING ASPHALTS WITH RESPECT TO THEIR EFFECTIVENESS AS RADIATION SHIELDING MATERIALS. /FHWA/

  • Corporate Authors:

    Federal Highway Administration

    Office of Research and Development, 1200 New Jersey Avenue, SE
    Washington, DC  USA  20590
  • Authors:
    • Oglio, E R
    • Boone, J G
    • Zenewitz, J A
  • Publication Date: 1972-6

Media Info

  • Pagination: 28 p.

Subject/Index Terms

Filing Info

  • Accession Number: 00210491
  • Record Type: Publication
  • Source Agency: Federal Highway Administration
  • Report/Paper Numbers: FHWA-RD-72- 49 Final Rpt., FCP 24A1-022
  • Files: TRIS, USDOT
  • Created Date: Oct 9 1976 12:00AM