A 13C NMR and DSC Study of the Amorphous and Crystalline Phases in Asphalts

The amorphous and crystalline phases in asphalt have been identified and studied using low-temperature solid-state carbon-13 CP/MAS NMR and DSC techniques. The NMR mass percent of the crystalline methylene carbons was shown to correlate linearly with the mass percent of crystalline wax in asphalts measured using DSC. While the internal methylene carbon content of long-chain alkanes in the crystalline phase in the asphalts varied, the internal methylene carbon content of the long-chain alkanes in the amorphous phase remained relatively constant. The NMR crystalline methylene carbon content was plotted against a low-temperature cracking parameter, the fracture temperature of an asphalt. It was found that 1% or less of aliphatic carbons in the crystalline phase has little effect on the fracture temperature. For these asphalts, the fracture temperature depends mainly on the initial amount of mobile aliphatic carbons in the amorphous phase at 23 °C. For asphalts containing 1% or more of crystalline aliphatic carbons, the fracture temperature increases with increasing crystalline methylene carbon content.