In their quest to improve overall pavement performance and durability, pavement engineers in recent years developed and used innovative asphalt mixtures utilising engineered or modified asphalt binders. The technology of asphalt modification using refining processes has evolved in the past decade as a viable, effective alternative. Results of an extensive evaluation of several paving asphalt binders modified by refining processes are presented and discussed. The evaluation used testing and characterisation systems developed in the Strategic Highway Research Program (SHRP) and recent revisions of these systems as proposed in the NCHRP 9-10 project. Rheological, failure and ageing properties at temperatures that simulate pavement service were measured and analysed. Handling, constructability and performance characteristics of asphalt binders modified by refining processes are evaluated and compared with those of conventional materials and asphalt modified by different types of polymers. Comparative performance results on asphalt mixtures are presented to show the effect of the improvements in binder characteristics on mixture performance. Results on new binder test methods developed as part of NCHRP 9-10 are also presented comparing binder and mixture performance characteristics. For the covering abstract of this conference see ITRD number E211271.

Following the five-year study performed to investigate the behavior of binders and asphalt mixtures containing polymer modifiers, it was determined that an insufficient amount of time had elapsed to allow any determinations to be made based upon the special field test sections. The study reported herein was to extend that initial time and to study in depth those special test sections, using visual observations coupled with resulting tests performed on samples extracted from the sections and comparisons with the original data developed in the original research. The research includes laboratory testing of field samples, determining the aging effect on the control and modified binders and corresponding effect on the mixtures, and visual evaluations. Retained samples of the original asphalts were also evaluated for potential performance as determined by the performance-based asphalt binder specification developed by the Strategic Highway Research Program. Four hot mix pavement field projects were constructed in the Tyler, Lufkin, San Antonio, and Childress Districts (10, 11, 15, and 25, respectively), and two seal coat projects were placed in the Odessa and Bryan Districts (6 and 17).