Thermal behavior of asphalt cements

Asphalt cements are highly complex mixtures of hydrocarbon molecules whose thermal behavior is of prime importance for petroleum and road industry. From DSC, the determination of several thermal properties of asphalts is gi ven, e.g. glass-transition temperature and crystallized fraction content. The dissolution of a pure n-paraffin CnH2n+2 in an asphalt, as seen by DSC, should be a single peak. For 20<n<32 two peaks were observed. This means t hat their dissolution occurs in two liquids, and explains the usual shape o f the DSC traces of AC, which shows a minimum at 35 degrees to 40 degrees C . At room temperature, an asphalt cement is a mixture of two liquids containi ng some crystallized fractions. Above 80 degrees C, it appears as a single liquid phase. At low temperature, the study of the glasses formed was done, using either constant or variable heating rate DSC. This technique, shows two glass transitions, for an asphalt containing a high quantity of crystal lized fractions. The T-g of these glasses change with time and temperature. The formation of the crystallized phases is superposed to the enthalpic re laxation of the glasses, making a kinetic study very difficult. (C) 1998 El sevier Science B.V. All rights reserved.