Separation of wax fraction in asphalt binder by an improved method and determination of its molecular structure

Abstract

The crystalline wax in asphalt binder has obvious influence on the low temperature performance of the asphalt pavement, and it is essential to adopt an accurate and efficient method to separate crystalline wax from asphalt binder. In this paper, the optimum eluted solvents used for the separation of the wax fraction are determined by the solubility parameters, and the reduced pressure column chromatography method is developed through the improvement of existing methods. It was discovered that the efficiency and accuracy of the experiment had been greatly improved with the higher repeatability and recovery of the saturates and aromatics. On this basis, the average molecular structures of the saturate and aromatic wax fraction were determined by the gas chromatography-mass spectrometry (GC–MS), gas chromatography-flame ionization detector (GC-FID), nuclear magnetic resonance (NMR) and Fourier-transform infrared (FTIR) spectroscopy methods. The smaller degree of the branch chain of the wax fraction would attribute to the larger content of the crystalline wax in asphalt binder, which could provide a compositional mechanism explanation for the physical hardening (thermoreversible ageing) of the asphalt binder at the low temperature.