Contributions of PG Graded Asphalt to low Temperature Cracking Resistance of Pavement

The purpose of this research was to study and evaluate the role that asphalt binders play in the resistance of asphalt pavements to low temperature cracking. As part of the Strategic Highway Research Program (SHRP) new specifications for asphalt binders were developed that are based on the performance of the material. The asphalt binder graded and specified according to these new performance-based specifications is called PG binder. These new specifications are commonly referred to as Superpave (Superior Performing Asphalt Pavement) binder specifications. A section of Interstate 64 in southern Indiana was experiencing severe low temperature cracking before it was reconstructed over the summers of 1995 and 1996. The binder used in the new pavement mixes was PG material. Dynamic Shear Rheometer (DSR) tests, Bending Beam Rheometer (BBR) tests, and viscosity tests were performed on this binder. Comparisons were made between test results obtained from the binders in the old pavement and the new pavement. All tests and comparisons were based on the Superpave binder specifications. A portion of this study involved a review of the extraction and recovery procedures used in the laboratories. Much of the asphalt used in this project had to be extracted from cores or pavement mixes, and it was important to ensure that the extraction and recovery process did not significantly change the properties of the material. Also, as a part of this research project, plans were developed for field monitoring of the temperature distribution within the pavement and its variation with time, in order to correlate these changes with pavement performance. Data generated during this monitoring program will be used in the future for validation of low temperature algorithms developed as a part of Superpave system