Predicting low temperature physical hardening in asphalt binders

The effect of the glass transition behavior on the rate and magnitude of physical hardening was studied for modified and unmodified asphalt binders. The analysis showed that the rate of physical hardening peaks at the glass transition temperature and becomes relatively insignificant beyond the limits of the glass transition region.Following the free volume concept, it was shown that physical hardening can be modeled as a function of isothermal time by a modified mechanical creep model. Such a model was developed in this study and used to predict physical hardening as a function of glass transition, conditioning time, and temperature.

► The effect of the glass transition on physical hardening was studied for asphalt binders.
► Using free volume concept physical hardening was modeled using a modified mechanical creep model.
► Most hardening is limited to the glass transition, peaking at the glass transition temperature.
► Model parameters are material specific and constant at all conditioning times and temperatures.
► Superpave BBR S and m-values can be predicted after physical hardening using developed model.