Elimination of Empirical, Ineffective and Expensive PG Plus Tests to Characterize Modified Binders

Most departments of transportation, such as the Arkansas Department of Transportation (ARDOT), evaluates the high-temperature resistance of asphalt binders using a dynamic shear rheometer (DSR) in accordance with AASHTO T 315, which is unable to adequately capture the effects of elastomeric modification. Thus, ARDOT requires conducting the Elastic Recovery (ER) method (AASHTO T 301), and a PG Performance Grade (PG) Plus test that is empirical in nature, expensive and time-consuming. However, findings of a recent ARDOT sponsored project reveals that neither ER nor Multiple Stress Creep Recovery (MSCR) tests are effective to characterize high PG grade binders (i.e., PG 70-22 or PG 76-22) modified with non-polymeric additives such as acid. Therefore, other mechanistic or chemical-based test methods such as SARA (saturate, aromatic, resin and asphaltene) analysis will have to be explored to find a simple and effective test protocol for characterizing high PG grade binders irrespective of the modification process. The main objective of the proposed study is to develop new test method(s) to evaluate modified binders as a replacement for ER test. This objective will be accomplished by testing asphalt binder samples modified with different additives such as polymers, ground tire rubber, and acid. Rutting and fatigue resistance of these binders will be evaluated so that empirical tests can be eliminated.