RATES OF ASPHALT HARDENING AT IN-SERVICE TEMPERATURES

HARDENING OF THE ASPHALT BINDER IN ASPHALTIC CONCRETE PAVING MIXTURES IS THE OBSERVABLE CAUSE OF MANY PAVEMENT FAILURES. WHY DO SOME ASPHALTS HARDEN BEFORE OTHERS UNDER IDENTICAL SERVICE CONDITIONS? IS THE DIFFERENCE IN DURABILITY DUE ONLY TO WEATHER AND TRAFFIC, OR DOES IT ALSO REFLECT PHYSICAL AND CHEMICAL DIFFERENCES IN THE MANY ASPHALT CEMENTS NOW AVAILABLE? THESE QUESTIONS ARE EXPLORED IN THIS INFORMATIONAL RELEASE FROM LONG-TERM RESEARCH AT PENN STATE ON ASPHALT DURABILITY, SPONSORED BY THE PENNSYLVANIA DEPARTMENT OF HIGHWAYS AND THE U.S. BUREAU OF PUBLIC ROADS. IN THE PROJECT LABORATORY AT PENN STATE, FIELD SAMPLES OF SOL, SOL-GEL, AND GEL ASPHALTS, ALL WITHIN THE 85 TO 100 PENETRATION RANGE, WERE STUDIED TO COMPARE THE EFFECT OF SERVICE TEMPERATURES ON THEIR VISCOSITY AND ASPHALTENE CONTENT OVER TIME. THE PRIMARY RESEARCH TASK WAS TO TEST THE POSTULATE THAT THE RATE OF CHANGE FOR EACH TYPE MIGHT BE A BETTER INDICATOR OF POTENTIAL DURABILITY THAN ULTIMATE CHANGE VALUES. THOUGH BOTH THE APPARENT ABSOLUTE VISCOSITY AND THE ASPHALTENE CONTENT OF THE TEST ASPHALTS INCREASED WITH TEMPERATURE AND EXPOSURE TIME, THE DATA FROM MORE THAN 800 SPECIMENS IN 100 MICRON FILMS ON GLASS PLATES SHOWED LITTLE COMPARATIVE DIFFERENCE IN RATE OF CHANGE FOR THE THREE TYPES. BUT MULTIPLE-POINT MEASUREMENTS WITH A CONE-PLATE VISCOMETER PROVED THE COMPLETE INADEQUACY OF SINGLE-POINT VISCOMETRY FOR THESE COMPLEX HYDROCARBON MATERIALS. ALL OF THEM EXHIBITED PSEUDOPLASTIC PROPERTIES AT 140 F, THE TEMPERATURE AT WHICH THEIR FLOW WAS EXPECTED TO BE NEWTONIAN. SINCE THE ASPHALTENE INCREASE DID NOT EXPLAIN THIS BEHAVIOR, IT MUST HAVE BEEN CAUSED BY THE FORMATION OF OTHER HEAVY MOLECULAR STRUCTURES BY INTERNAL PROCESSES SUCH AS POLYMERIZATION. THE VISCOSITY AND ASPHALTENE DATA OBTAINED IN THIS INVESTIGATION INDICATE THAT SOL ASPHALTS HAVE BETTER HARDENING CHARACTERISTICS THAN THE OTHER TYPES TESTED, AND SHOULD THEREFORE BE MORE DURABLE AS PAVING CEMENTS. /PSU/

  • Supplemental Notes:
    • Eng Res BulL B-100, 48 PP, 22 FIG, 13 TAB, 35 REF
  • Corporate Authors:

    Pennsylvania State University, University Park

    Pennsylvania Transportation Institute, Transportation Research Building
    University Park, PA  USA  16802
  • Authors:
    • Gotolski, W H
    • Ciesielski, S K
    • Smith, R W
  • Publication Date: 1969-12

Subject/Index Terms

Filing Info

  • Accession Number: 00211544
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Aug 26 1970 12:00AM