Development of SUPERPAVE High-Temperature Performance Grade (PG) Based on Rutting Damage

摘要

SUPERPAVE asphalt binders are selected using the Performance Grade (PG) methodology introduced by SHRP. The PG grading system has two components; low-temperature and high-temperature. The work presented in this paper provides an improved methodology to select the high temperature PG grade for asphalt binders. An enhanced high-temperature transfer function for pavement temperatures was developed through a comprehensive application of the Integrated Climatic Model (ICM) This model was developed using hourly climatic data, providing a more accurate representation of the high-temperature conditions in the pavement. Using the hourly high-temperature calculations, a performance based procedure utilizing current empirical models for HMA stiffness and rut predictions was developed. This procedure is a damage based comparison of rut development and the impact of the use of different PG graded binders to compare the accumulation of damage. It accounts for extended hot periods in certain climates, which could not be considered in the original selection procedure. Models were developed to extend the damage-based PG concept from the limited number of stations with hourly temperature data to the entire database using daily temperature data. A Degree-Days concept was developed to relate the number of days the pavement temperature is over 10 C to the damage-based PG calculation. The performance based nature of the damage concept allows for a mechanistic inclusion of traffic amount, and the traffic speed. Recommendations for grade bumping for traffic and speed were presented. Variability was included to provide protection against the one-time extreme temperature event. An existing software program was modified to include the new algorithm for implementation.