Evaluation of Low Temperature Properties of SISSI Mixtures and Binders

Open Access
Author:
PREMKUMAR, LAXMIKANTH
Graduate Program:
Civil Engineering
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
September 08, 2008
Committee Members:
  • Dr Ghassan R Chehab, Thesis Advisor
  • Mansour Solaimanian, Thesis Advisor
Keywords:
  • IDT
  • BBR
  • Thermal cracking
  • Asphalt
Abstract:
The main objective of this thesis is to revisit and build on the equivalence principle that governs the low temperature Superpave™ binder specifications. Bending beam rheometer (BBR) tests were conducted on asphalt binders from wearing layers of seven Superpave In-situ Stress Strain Investigation (SISSI) project sites. All the asphalt binders were aged with pressure aging vessel (PAV) prior to conducting the BBR tests. Both 240 second and 2 hour tests were conducted at three different temperatures, at the low temperature of the asphalt PG grade, 10°C higher than the lower temperature grade and at -5°C to obtain the flexural creep stiffness [S(t)] master curves. Additionally, indirect tensile tests (IDT), to capture the low temperature properties of the mixtures, were conducted on field mixtures obtained from the wearing layers of all the SISSI sites. From the BBR test results, it is observed that the equivalence principle that governs the low temperature Superpave™ binder specification does not hold for the SISSI binders tested and therefore alternate times and temperatures for testing are suggested in this research to deliver an equivalent stiffness. However, further testing on other types of asphalt binders is required to reach a comprehensive consensus. Further, the time-temperature shift factors for the SISSI binders are compared with the Strategic Highway Research Program (SHRP) and SISSI mixtures. The SISSI and SHRP shift factor curves do not match, contradicting the fact that all asphalt binders can be characterized by similar shift factors. The shift factors of the SISSI binders and mixtures tend to match well at higher than at lower testing temperatures. Finally, all the SISSI sites are ranked in accordance with their low temperature asphalt binder and mixture properties and the results are presented.