Evaluation of low-temperature fracture properties of asphalt binder

Open Access
Author:
Gauthier, Gilles Gerard
Graduate Program:
Civil Engineering
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
November 09, 2012
Committee Members:
  • David A Anderson, Thesis Advisor
  • Peggy Ann Johnson, Thesis Advisor
  • Mansour Solaimanian, Thesis Advisor
  • Shelley Marie Stoffels, Thesis Advisor
Keywords:
  • asphalt fracture properties
Abstract:
To rationally predict low temperature cracking in flexible pavements, the ability of asphalt binder to resist crack initiation and propagation must be measured. Different theoretical approaches to this problem exist. The current Superpave low-temperature binder grading system is based on the measurement of stiffness and strength. This method was developed during the SHRP program and allowed significant progress in the prediction of low-temperature binder performance. However, further improvements are required, especially to better describe the low-temperature behavior of modified asphalt binders. The use of fracture mechanics principles is a potential alternative to the current Superpave approach. Attempts have been made to apply this method to characterize the fracture properties of asphalt binders at low temperature. Researchers always assumed binders to be linear elastic. The results obtained from these studies were encouraging and concluded that fracture mechanics was a useful tool to describe binders at low temperature and leads to a different ranking of binder performance as compared to the Superpave grading system. This study was to verify and determine the limits of the applicability of linear elastic fracture mechanics (LEFM) to asphalt binder. Alternative, fracture mechanics-based approaches were considered to account for non-linear behavior. These methods imply the laboratory determination of critical fracture parameters: linear stress intensity or fracture toughness KIC, plastic energy rate JIC, and time-dependent energy rate JVC. The measurement of KIC was found to be straightforward using existing laboratory tools. To obtain JIC and JVC values, more tests and data analysis are required. Loading curves obtained from fracture testing of nine binders were analyzed using the different fracture mechanics approaches. Superpave critical temperatures were also determined for all binders. Binder characterization was completed with the dynamic thermo-mechanical determination of their glass transition temperature, Tg.