A New Framework for Determining the Gradation of Asphalt Mixtures

Strength and rutting resistance as well as durability are the main quality measures for any asphalt mix. While the strength and resistance of the asphalt mixture to permanent deformation are controlled by the aggregate interlock and aggregate packing, the durability of asphalt mixture depends on adequate volumetric characteristics and film thickness of asphalt mixture. Accordingly, providing an adequate interlock between aggregates and the aggregate packing is of high importance in designing a new asphalt mixture in order to produce desirable volumetric characteristics in asphalt mixture. A new framework for asphalt mixture gradation has been developed and designed following an intensive review of the various currently used approaches. The new framework considers all the controlling factors in the aggregate gradation design for optimum gradation of the asphalt mixtures. Satisfactory interlocking between aggregate particles, proper skeleton within the asphalt mixture, and acceptable volumetric properties are the main parameters to be considered for optimum gradation design for asphalt mix. The framework provides a systematic approach for the gradation process starting from the concentration at different sieves to finally account for the 𝐹𝐴 ≤ 0.5. Other parameters including 𝐹𝐴 ratio, CA ratio and 𝐷 are also considered through the current framework.