Using thermal analysis methods to better understand asphalt rheology

The Strategic Highway Research Program allowed to define some parameters that characterize the rheological properties of asphalt cement(s) (ACs). Those parameters implied that ACs follow the time and temperature superposition principle. However, highly asphaltic or waxy ACs deviate from this rule since their structure changes as a function of time and temperature. Some of these transitions clearly appear on differential scanning calorimetry curves. This paper shows some analogies between thermo-analytical and rheological properties of ACs. In particular, it emphasizes the roles of crystallized fraction(s) (CFs) and of the glass-transition temperature (T-g) on the whole temperature range of end use. Thus, at low temperatures, CF seems greatly responsible for the physical hardening (PH) occurring with time. PH magnitude also depends on the position of T-g relative to the given conditioning temperature. At higher temperatures, CF also plays a role on the rheological behavior since their dissolution-precipitation mainly occurs at temperatures between 0 degrees and 80 degrees C. (C) 1998 Elsevier Science B.V. All rights reserved.