FACTORS INFLUENCING DYNAMIC MODULUS OF ASPHALT CONCRETE

DYNAMIC MODULUS AND OTHER TEST DATA FOR A VARIETY OF DENSE-GRADED ASPHALT CONCRETE AND TWO HOT-MIX SAND ASPHALT MIXES WERE USED TO DEVELOP RELATIONSHIPS BETWEEN DYNAMIC MODULUS AND MIX CHARACTERISTICS (AIR VOIDS, ASPHALT CONTENT, ETC.) AND BETWEEN DYNAMIC MODULUS AND MECHANICAL PROPERTIES (MARSHALL STABILITY AND FLOW, ETC.). THE RELATIONSHIPS BETWEEN MODULUS AT CONSTANT TEMPERATURE AND MIX CHARACTERISTICS AT CORRESPONDING CONDITIONS LEAD TO THE FOLLOWING CONCLUSIONS FOR THE CONDITIONS INCLUDED IN THE TEST PROGRAM: (1) FOR A CONSTANT ASPHALT CONTENT, MODULUS INCREASES AS AIR VOIDS DECREASE, (2) FOR A CONSTANT AIR VOID CONTENT, MODULUS INCREASES AS ASPHALT CONTENT DECREASES, (3) FOR CONSTANT COMPACTIVE EFFORT, MODULUS MAY INCREASE OR DECREASE AS AIR VOIDS AND ASPHALT CONTENT CHANGE, BUT THE CHANGES IN MODULUS ARE MINOR FOR ASPHALT CONTENTS VARYING 1 PER CENT ABOVE OR BELOW OPTIMUM ASPHALT CONTENT, (4) MODULUS INCREASES AS ORIGINAL ASPHALT VISCOSITY INCREASES (OR PENETRATION DECREASES), ALL OTHER CONDITIONS BEING EQUAL. EQUATIONS WERE DEVELOPED TO SHOW THE INTERRELATIONSHIPS BETWEEN DYNAMIC MODULUS AND MIX CHARACTERISTICS FOR THE VARIETY OF MIXES. INCLUDED IN THE STUDY. EQUATIONS WERE ALSO DEVELOPED FOR RELATIONSHIPS BETWEEN DYNAMIC MODULUS AND THE MARSHALL STABILITY-MARSHALL FLOW RATIO. THESE EQUATIONS REPRESENT THE OBSERVED EFFECTS REASONABLY WELL, AND MAY BE USED TO ESTIMATE MODULUS USING THE RESULTS OF RELATIVELY ROUTINE TESTS, OR FOR INVESTIGATING EFFECTS ON MODULUS PRODUCED BY CHANGES IN MIX PROPERTIES, CHANGES IN TEST TEMPERATURE OR MARSHALL TEST PROPERTIES. DR. MCLEOD SUGGESTS IN THE DISCUSSION AN APPROACH BASED ON EQUATIONS AND NOMOGRAPHS DEVELOPED BY PFEIFFER AND VAN DOORMAAL, VAN DER POEL, HEUKELOM AND KLOMP, ANF VAN DRAAT AND SOMMER, RATHER THAN THE TWO PURELY EMPIRICAL EQUATIONS PROPOSED BY THE AUTHORS. MR SHOOK REPLIES THAT HOW CHANGES IN MODULUS MIGHT AFFECT PAVEMENT PERFORMANCE WAS NOT A FACTOR FOR STUDY IN THIS INVESTIGATION AND WE ARE NOT PREPARED TO COMMENT ON THIS ASPECT OF THE OVERALL PROBLEM AT THIS TIME. DR MC LEOD COMMENTS FURTHER ON THE PENETRATION INDEX VALUES. THE STATEMENT OF DR. MCLEOD IS AGREED WITH BY PROFESSOR K. O. ANDERSON THAT IN APPROACHING THE DESIGN OF MIXES WE MUST CONSIDER MIX PROPERTIES, NOT ONLY AT HIGH TEMPERATURES BUT ALSO AT LOW TEMPERATURES.

• Supplemental Notes:
  • Vol 38, pp 140-178, 19 FIG, 11 TAB, 16 REF
• Authors:
  • Shook, J F
  • Kallas, B F
  • Mcleod, N W
  • Finn, F N
  • Pell, P S
  • Krchma, L C
  • Haas, R C
  • Anderson, K O
• Discussers:
  • Obrcian, V
• Conference:
  • Association of Asphalt Paving Technologists Proc
• Publication Date: 1969-2

Subject/Index Terms

• TRT Terms: Air voids; Asphalt concrete; Asphalt content; Asphaltic sand; Compaction; Dynamic modulus of elasticity; Equations; Hot mix asphalt; Marshall test; Mechanical properties; Mixing; Pendulum tests; Temperature; Viscosity
• Old TRIS Terms: Air voids content; Marshall stability marshall stability & flow test flow; Mixing temperature
• Subject Areas: Highways; Materials;

Filing Info

• Accession Number: 00211504
• Record Type: Publication
• Files: TRIS
• Created Date: Jul 27 1970 12:00AM