Investigation of wax inhibition efficiency based on alkane structures in model asphalt for sustainable utilization of wax inhibitors

Abstract

In recent years, the wax inhibitors (WIs) are used to inhibit premature crystallization of alkane molecules in asphalt at low temperatures has yielded certain benefits. However, the method for effective and sustainable use of WIs in asphalt to avoid inefficient and expensive “trial and error” procedures has not yet been determined. In this paper, the model asphalts were established through non-waxy base asphalt doped with n-alkanes (Eicosane, triacontane and tetradecane) and isoalkane (Squalene), and the wax inhibition efficiencies and cracking resistance of model asphalt with addition of three typical WIs (poly (methyl methacrylate) (PMMA), nano-SiO2 hybrid PMMA and ionic liquid (IL) modified with graphene oxide (GO)) were directly characterized by wax precipitation temperature (WPT) and extended bending beam rheometer (Ex-BBR), double edge notched tension (DENT) and thermal fatigue tests, respectively. On this basis, the microscopic mechanism of wax inhibition was investigated by molecular dynamic simulation. The results show that the wax inhibition efficiencies are higher for the short-chain n-alkanes and ordered isoalkanes to improve the low-temperature cracking, ductile and thermal fatigue resistances more significantly, but the disordered isoalkanes and high content of long-chain n-alkanes will decrease the wax inhibition efficiencies of WIs. The WIs can increase diffusion coefficient and bond stretching, angle bending and dihedral angle torsion energies but decrease the Coulomb and van der waals (VDW) energies of wax molecules to inhibit the formation of wax crystals network. It is recommended to add WIs with higher content or efficiency for asphalts with heavy n-paraffins and low concentration of branched paraffins to inhibit wax precipitation. As for asphalts containing light n-alkanes and high concentration of branched alkanes, it is suggested to add smaller amount of WIs to save resources.