Refinement of the Superpave Specification Parameter for Performance Grading of Asphalt

The Superpave specification parameter |G*|/sin δ for high temperature performance grading of paving asphalts has not been found to be adequate in rating various binders, especially some polymer-modified ones, for their rutting resistance. This has led researchers to seek other possible parameters that may better relate to rutting resistance and also to search for ways to improve the existing parameter |G*|/sin δ so that it is more sensitive to pavement performance. Some researchers have suggested the repeated creep and recovery test, while others have used a semiempirical approach as a means to refine the existing Superpave specification parameter. The present work revisits the proposed refinements of the Superpave specification parameter and shows that the semiempirical approach involving curve-fitting of experimental data is not necessary if the derivations are based on fundamental concepts. The final equations obtained through a theoretical development are verified using part of the same experimental data that were used by the earlier researchers.