Role of Bending Beam Rheometer Parameters in Thermal Stress Calculations

Abstract

The development of the Strategic Highway Research Program lowtemperature binder specifications was based on the observation that asphalt mixture creep stiffness at 2 h correlated well with instances of transverse cracking. With the correlation extended to asphalt binder stiffness and with time-temperature superposition, a maximum stiffness value was imposed on the binders, and a limiting temperature at which the stiffness at 60 s reached the limiting value was selected as a specification criterion. In addition, the slope at 60 s of the stiffness-versus-time curve on a double logarithmic scale, the so-called m-value, was introduced as an additional criterion. The role played by the stiffness and the m-value in the development of thermal stresses in asphalt pavements was investigated. The analysis showed that thermal stress magnitude was strongly related to the stiffness magnitude. At similar stiffness levels, higher m-values resulted in the faster development of thermal stresses.