In July 2014, California will be the last state to fully adopt Superpave (SUPerior PERforming asphalt PAVEments) asphalt mixture design and analysis test equipment and procedures. This is a significant milestone in the world of pavement design as it signifies a critical step forward in the development of Superpave industry best practices.
The Strategic Highway Research Program (SHRP) developed Superpave specification in the early 1990s as a way to develop durable, standardized pavement mix designs that can handle extreme temperatures and heavy traffic. The Federal Highway Administration (FHWA) adopted the performance-based Superpave mix design specification in 2002.
Key to the success of Superpave is the testing and validation of equipment, methodologies, mixes and prediction models. The Superpave process includes the selection of an aggregate structure and performance graded binder content. From there, a lab evaluates the dynamic modulus, creep compliance and moisture sensitivity.
Specialized equipment includes the Superpave Gyratory Compactor (SGC) for compacting test specimens during the mix design process and for quality control and quality acceptance testing during production. Other devices developed for use in Superpave mix analysis include the Superpave Shear Tester (SST) and Hamburg Wheel Tester (which will be used in California).
Even though Superpave has been around for some time, our industry has much to learn about the Superpave mix, tools and techniques that can be used to develop the most durable solutions—and California is looking to push that knowledge to the next step.
To develop its Superpave specification, the California Department of Transportation (Caltrans) established a Superpave committee comprised of industry, academia and Caltrans staff. The industry committee members include a wide range of laboratories, producers and contractors. The committee will develop the standards and procedures that can be applied on paving projects of all types and challenges, whether weather-related, traffic or a combination.
Since Caltrans specification development process will have the benefit of industry input and acceptance, we believe that the subsequent specification and testing procedures will likely provide value to other states and push the benefits of Superpave mix design to the next generation.