Abstract
ABSTRACT The development of the Strategic Highway Research Program (SHRP) low temperature binder specifications was based on the observation that asphalt mixture creep stiffness at 2 hours correlated well with instances of transverse cracking. Extending the correlation to asphalt binder stiffness and using time-temperature superposition, a maximum stiffness value was imposed on the binders and a limiting temperature at which the stiffness at 60 seconds reached the limiting value was selected as a specification criterion. The slope at 60 seconds of the stiffness vs. time curve on a double logarithmic scale, the so-called “m-value” was introduced as an additional criterion based on the idea that a low m-value meant a slower relaxation of the thermal stresses, which was detrimental for the performance. This paper investigates the use of the “m-value” as a specification parameter for asphalt binder physical characterization. A comparison between m and the corresponding slope for the relaxation modulus is performed. The influence of m-value on thermal stress calculation performed in accordance to AASHTO MP1a is also investigated.
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