Effect of Binder Rheology on the Low-Temperature Cracking of Asphalt Mixtures

The low-temperature properties of bituminous materials (binders and mixtures) were studied using Dynamic Shear Rheometer (DSR), Bending Beam Rheometer (BBR), and Tensile Stress Restrained Specimen Test (TSRST). It was observed that the glass transition temperatures (Tg) determined using DSC and the BBR limiting temperatures were greatly dependent on the source and grade of the bitumens. Polymer modification decreased the glass transition temperature, but slightly or negatively influenced the limiting temperatures. The fracture properties of mixtures as measured by TSRST were also dependent on base bitumens, and generally not improved by polymer modification. However, polymer modification changed the stress response of the mixtures during TSRST. For some mixtures with elastomer modified binders, the phenomenon of “soft” cracking was observed. Statistical investigations showed that the mixture fracture temperature correlated with the BBR limiting temperatures of the binders, but no relationships could be established between TSRST and DSR parameters.