Which system has been used for asphalt mix design since 1998?

The Superpave system has been utilized for asphalt mix design since 1998 and represents a significant advancement in the field. Superpave, which stands for Superior Performing Asphalt Pavements, was developed as part of the Strategic Highway Research Program (SHRP) to create a more performance-oriented approach to asphalt mix design. This system incorporates a variety of tests and methods to improve the quality and durability of asphalt pavements, addressing issues related to temperature susceptibility, moisture sensitivity, and traffic loads.

One of the key aspects of Superpave is its reliance on performance-based specifications, which allow for more accurate predictions of how asphalt mixes will perform in the field. This helps ensure that the pavement can withstand varying conditions over its service life.

In contrast, other options like the Marshall method, while historically significant, do not utilize the same rigorous performance-based criteria and were largely phased out in favor of the more comprehensive Superpave method. AASHTO is a standards organization and primarily focuses on developing guidelines rather than directly on asphalt mix design. The term "Hot Mix" refers to a broader category of asphalt mixtures rather than a specific design method. Thus, Superpave is the recognized system that revolutionized asphalt mix design starting in 1998.