MODIFICATION OF TEMPERATURE SUSCEPTIBILITIES OF ASPHALT PAVING MIXTURES WITH DISCUSSION

THE PRINCIPAL POINTS AND CONCLUSIONS OF THIS PAPER MAY BE SUMMARIZED AS FOLLOWS: (1) THREE MAJOR STRUCTURAL SUBSYSTEMS--FATIGUE, PERMANENT DEFORMATION, AND SHRINKAGE FRACTURE--ARE INCLUDED IN THE DESIGN OF ASPHALT PAVEMENTS. THE PROPERTIES OF CONVENTIONAL ASPHALT MIXTURES ARE IN MANY CASES NOT SIMULTANEOUSLY SUITED TO THE DESIGN OBJECTIVES OF THESE THREE SUBSYSTEMS. THE TEMPERATURE-CONSISTENCY NATURE OF THESE MIXTURES IS A PRIME FACTOR. (2) THIS INVESTIGATION HAS DEMONSTRATED THAT ASBESTOS FIBER MODIFICATION OF DENSE-GRADED ASPHALT MIXTURES CAN IMPROVE THEIR TEMPERATURE CONSISTENCY CHARACTERISTICS, COMPARED TO "STANDARD" MIXTURES AND TO MINERAL FILLER MODIFIED MIXTURES. THE DESIGN OF SUCH FIBER MODIFIED MIXTURES MUST EXPLICITLY RECOGNIZE THE TYPE OF FIBER BEING USED. (3) THE USE OF ASBESTOS FIBER MODIFICATION IS A PRACTICAL METHOD, THOUGH NOT NECESSARILY THE ONLY ONE, AND IT ALLOWS VOIDS CONTENT OF MIXTURES IN SERVICE TO BE LOWERED TO ABOUT ONE PERCENT. THIS LOW VOIDS PROPERTY IS CONSIDERED TO BE IMPORTANT TO THE REQUIREMENTS OF THE FATIGUE AND SHRINKAGE FRACTURE SUBSYSTEMS, AND TO THE OVERALL DURABILITY OF THE MIXTURES. (4) THE EXPERIMENTAL RESULTS WERE OBTAINED IN TERMS OF STIFFNESS, STRAIN TO FAILURE AND STRENGTH, OVER THE SERVICE TEMPERATURE RANGE OF -20 F. TO 140F., FOR "STANDARD" ASPHALT MIXTURES, ASBESTOS FIBER MODIFIED MIXTURES AND MINERAL FILLER MODIFIED MIXTURES. STATISTICAL DESIGNS WERE USED FOR THE EXPERIMENTS AND THE SIGNIFICANCE OF DIFFERENT LEVELS OF THE VARIOUS FACTORS, AS WELL AS THE EXISTENCE OF INTERACTIONS OF FACTORS, WERE EVALUATED. (5) A MAJOR FINDING IS THAT AT LOW-TEMPERATURES, THE PROPERTIES OF ALL TYPES OF MIXTURES ARE PRIMARILY A FUNCTION OF THE ASPHALT TYPE USED; BUT, AT MEDIUM TO HIGH SERVICE TEMPERATURES, ASBESTOS FIBER MODIFICATION CAN SIGNIFICANTLY IMPROVE MIXTURE PROPERTIES, IN COMPARISON TO "STANDARD" CONDITIONS AND TO MINERAL FILLER MODIFICATION. (6) A MAJOR IMPLICATION OF THIS FINDING IS THAT WHERE A SOFTER ASPHALT IS TO BE USED FOR LOW-TEMPERATURE CRACKING CONSIDERATIONS, ASBESTOS FIBER MODIFICATION MAY BE USEFUL. SUCH MODIFICATION WILL NOT APPRECIABLY ALTER LOW-TEMPERATURE STIFFNESS BUT IT WILL INCREASE MEDIUM TO HIGH SERVICE TEMPERATURE STIFFNESS AND THEREBY POSSIBLY AVOID VIOLATIONS OF FATIGUE AND PERMANENT DEFORMATION REQUIREMENTS. (7) THE PROPERTIES OF ASPHALT MIXTURES DETERMINED IN THIS INVESTIGATION CORRESPOND REMARKABLY WELL WITH THESE REPORTED FROM THE ARKONA TEST ROAD AND THE STE. ANNE TEST ROAD. THESE COMPARISONS SUPPORT THE CONCEPT OF LIMITING STIFFNESS GUIDELINES FOR THE PROBLEM OF LOW-TEMPERATURE CRACKING; A RECENTLY DEVELOPED, MORE COMPREHENSIVE DESIGN APPROACH IS ALSO SUPPORTED BY THE FINDINGS. THE PAPER INCLUDES A DISCUSSION WHICH DEALS WITH VARIOUS QUESTIONS CONCERNING THIS INVESTIGATION.

• Authors:
  • Hignell, E T
  • Hajek, J J
  • Haas, R C
• Conference:
  • Association of Asphalt Paving Technologists Proc
• Publication Date: 1972

Media Info

• Features: Figures; References; Tables;
• Pagination: p. 524-61
• Serial:
  • Volume: 41

Subject/Index Terms

• TRT Terms: Asbestos; Asphalt pavements; Bituminous mixtures; Consistency; Cracking; Deformation; Durability; Fatigue (Mechanics); Fibers; Laboratory tests; Low temperature; Pavement cracking; Pavement design; Pavements; Shrinkage; Stiffness; Temperature; Tensile strength; Void ratios
• Old TRIS Terms: Shrinkage cracks; Void
• Subject Areas: Highways; Materials; Pavements;

Filing Info

• Accession Number: 00211823
• Record Type: Publication
• Files: TRIS
• Created Date: Sep 17 2002 12:00AM