This technical memorandum summarizes the first phase of a research study on the implementation of Superpave mix design for the California Department of Transportation (Caltrans). Fifteen Hveem mix designs selected from around the state were used as the basis of this study. The 15 selected mix designs vary in binder PG-grade, binder type (unmodified, rubber, and polymer), aggregate gradation and mineralogy, and RAP percentage. Based on the Hveem mix designs, Superpave volumetric mix designs were developed for each mix and comparisons were made between mixes developed from both methods. Specifically, these mixes were evaluated to meet the draft Caltrans Superpave volumetric mix design specification which includes the design air-void content, percent VMA, percent VFA and dust proportion as major design components. Details regarding adjustments to and strategies in determining the Superpave optimal binder content for each mix are discussed. A summary of changes and adjustments to Hveem mixes needed to meet Superpave specifications is presented. Recommendations for specimen preparation using Superpave mix design procedures are given.

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.

In the period 2012 to 2014 Caltrans designed and built three long-life asphalt pavement (LLAP) rehabilitation projects. Two projects were in District 2 on Interstate 5—one just north of the city of Red Bluff and the other on the interstate running through and north of the city of Weed—and one in District 4 on Interstate 80 in Solano County between the cities of Dixon and Vacaville. This technical memorandum describes the processes by which performance criteria were developed for a pavement section that is part of the LLAP project on Interstate 80. This pavement section, designed and constructed as an LLAP section, consisted of the following pavement components: A hot mix asphalt (HMA) surface course containing a polymer-modified asphalt (PG 64-28PM) with 15 percent reclaimed asphalt pavement (RAP) and a representative virgin aggregate from the local area treated with 1.2 percent lime (marinated). An HMA intermediate course containing a conventional asphalt binder (PG 64-10), 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 material parameters developed from AASHTO T 320 shear testing and AASHTO T 321 fatigue and stiffness testing results. Pavement design for the Solano project made use of the same mix parameters as those used for the design of the Caltrans District 2 Interstate 5 Red Bluff project but with traffic and climate data specific to the Solano site. In addition to the AASHTO T 320 and T 321 results used for the 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. The HWTT results were not used in the design process.

This technical memorandum presents the results of pavement evaluation and rehabilitation design of 02-PLU-36, PM 6.3/13.9. The pavement evaluation consists of deflection testing, coring, material sampling, backcalculation of stiffnesses, and condition assessment. Rehabilitation designs were developed using standard Caltrans methods. Alternative rehabilitation designs were developed using mechanistic-empirical software and models (CalME). Performance of all designs was assessed using mechanistic-empirical models. Suitable designs are recommended.