CRITICAL ANALYSIS OF PH AND PG+ ASPHALT BINDER TEST METHODS
One of the principle products from the Stratigic Highway Research Program (SHRP) was the Superpave asphalt binder performance grading (PG) specification system. This system was based on fundamental engineering principles and has been adopted by almost all local and state agencies. Recently, different types of asphalt binder modification have increased in popularity. All the potential implications of asphalt binder modification cannot be captured by the Superpave grading system. In response to the apparent deficiencies of Superpave, state agencies have implemented PG plus (PG+) test methods. Specification limits for current PG+ tests have largely been based on engineering judgement and little research has been conducted to correlate PG+ test methods to field performance. In addition, new PG+ test methods, not currently included in any state specification, have been developed to characterize an asphalt binder?s resistance to each type of asphalt pavement distress in the field. Materials provided by the Western Cooperative Testing group (WCTG) were used in this study to investigate all available PG and PG+ methods. Each test was evaluated for adherence to fundamental engineering principles and correlated with select mixture performance tests. Mixture performance tests can measure the bulk properties of asphalt pavements and those binder test methods that have the highest correlation with mixture testing results merit consideration for state specifications. Results of this study were successfully able to identify PG+ test methods that correlate with mixture testing performance and recommendations were provided for future research and development of a new performance based specification.