UC Davis Institute of Transportation Studies

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.