NCHRP Project 09-65, Capturing Durability of High Recycled Binder Ratio (RBR) Asphalt Mixtures, was initiated to (1) develop a proposed AASHTO standard practice and associated test methods for the design and evaluation of durable asphalt mixtures with high Recycled Asphalt Materials (RAP) content and (2) revise the proposed AASHTO Standard Practice for Characterization of Asphalt Mixtures with High Recycled Materials Contents and Recycling Agents.

This proposed draft AASHTO Standard Practice was previously developed in NCHRP Project 09-58 that included the construction of 18 field sections across 5 field projects that have now been in service for 7-9 years. Thus, field performance monitoring and laboratory evaluation of cores from those field sections still in-service will allow for the unique opportunity to calibrate and revise, as necessary, the performance criteria/thresholds included in the Standard Practice. These results will allow further validation of a promising model to predict mixture cracking performance from 33 field sections and the development of a process that DOTs can follow to further refine these models based on their local mixes and conditions. The implementation of the stepwise mix design approach being developed in NCHRP 09-65 to ensure the durability of high RBR mixtures via the training course will allow for confidence in its application and inclusion in the Standard Practice.

NCHRP Project 20-44(60) will support the adoption of the research results of NCHRP Project 09-65 through the development and delivery of a training course for DOT personnel for the step-by-step implementation of the mixture design based on the proposed draft AASHTO Standard Practice for asphalt mixtures with high RAP content. 

The planned activities for the training course under NCHRP Project 20-44(60) include:

• Calibration of performance models to improve the general models and simultaneously develop a process for collecting and evaluating data.
• Development and delivery of a step-by-step mixture design training course based on the proposed standard and process created to update performance models.
• Documentation of the implementation effort summarizing lessons learned and recommendations to facilitate the adoption of the standard.