EVALUATION OF RHEOLOGICAL MEASUREMENTS FOR UNMODIFIED AND MODIFIED ASPHALT CEMENTS

A rigorous evaluation of the dynamic shear rheometer (DSR) with both unmodified and modified asphalts indicated that testing problems such as potential compliance-related problems, plate slip, and equipment limitations could be easily identified during testing. Once these problems were identified changes in either the test configuration or the testing parameters could eliminate the problem. The relationship between the complex modulus (G*) and the complex viscosity showed that G* (in kilopascals) is equal to the complex viscosity (in poise) at 10 rad/sec. It was also shown that the complex viscosity, the DSR viscosity, could be estimated by the traditional vacuum viscosity for test temperatures of 46 deg C and above for unmodified asphalt cements. Typical values for the phase shift for test temperatures of 46 deg C and 64 deg C were 81 and 89 deg, respectively, for unmodified asphalt cements and 60 and 81 deg, respectively, for polymer-modified asphalts. For this range of test temperature the temperature had a greater influence on changes in the phase shift than in the change of asphalt source or grade for unmodified asphalts. Changes in the phase shift for modified binders were dependent on the test temperature, type of polymer, and asphalt source or grade. A quick method of estimating the temperature at which G*/sin of the phase shift equals 1 kPa for unmodified asphalts is presented. Briefly, if the sin of the phase shift can be assumed to be 1 for unmodified asphalts, then the traditional viscosity measurements at both 60 deg C and 135 deg C can be used to estimate the temperature at which the viscosity would be 1000 P (i.e., G* = 1 kPa). This approach compared well with the DSR-developed temperatures reported by Strategic Highway Research Program researchers.

Language

  • English

Media Info

  • Features: Figures; References; Tables;
  • Pagination: p. 72-81
  • Monograph Title: Unmodified and modified asphalt binders
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00714795
  • Record Type: Publication
  • Files: TRIS, TRB, ATRI
  • Created Date: Nov 29 1995 12:00AM