Development of Hot Mix Asphalt Pavement Performance Properties for Long-life Pavement Designs: Caltrans District 2, Interstate 5, Weed, California

In the period 2012 to 2014 Caltrans designed and built three long-life asphalt pavement (LLAP) rehabilitation projects. Two were in District 2 on Interstate 5 and one was in District 4 on Interstate 80. This technical memorandum describes the processes that were followed to develop the performance criteria for a pavement section to be designed and constructed as a long-life asphalt pavement (LLAP) section on Interstate 5 through and north of Weed, California. Appropriate layers of the structural pavement included 25 percent reclaimed asphalt (RAP), based on the availability of this material. Two designs were included in the development process. The planned structural pavement design included the following two hot mix asphalt mixes: An HMA surface course containing a polymer-modified asphalt (PG 64-28PM) and a representative aggregate from the Weed area treated with 1.2 percent lime (marinated) plus 15 percent RAP, and An HMA intermediate course containing a conventional asphalt binder (PG 64-16) and the same lime-treated aggregate as the surface course plus 25 percent RAP. Caltrans headquarters staff from the Office of Asphalt Pavement designed the structural pavement sections using results for material parameters developed from AASHTO T 320 shear, and AASHTO T 321 fatigue and stiffness testing. To properly establish testing protocols and parameters, it was also necessary to investigate the impact of traffic-loading and environmental factors as part of the study. These test results provided the basis of the performance and testing criteria included in the project specifications and bid documents. In addition to the AASHTO T 320 and AASHTO T 321 results used for design and performance-related specifications, results from AASHTO T 324 Hamburg Wheel-Track Testing (HWTT) were required in the performance-based specifications as a consideration for moisture sensitivity of the asphaltic mixes. The HWTT results were not used in the structural design process