| Bitumen emulsions as a liquid mixture under normal temperature are widely used in many industrial applications.This work presents experimental evidence of pronouncedly different phase separation situations for bitumen emulsions at various salt concentrations. With increasing sodium chloride concentration (CNaCl), the added salt promotes the degree of phase separation of bitumen emulsions at CNaCl lower than5.3mM, where separated water is the upper phase and the bitumen is the lower phase. Nevertheless, this kind of phase separation is gradually reduced as CNaCl increases from5.3to250mM. At CNaCl=250-500mM, the bitumen emulsion with very low degree of phase separation is observed to transit from the aqueous phase in the upper position and the bitumen phase in the lower level into the reverse situation. Further increase of salt amount in bitumen emulsions leads to the enhanced phase separation at CNaCl=500-830mM. The zeta potential, density, and viscosity of bitumen emulsions have been measured for understanding the above phase separation behaviors of bitumen emulsions observed at various salt concentrationsAt the same time, the mixed emulsifier of Gemini surfactant and octadecyltrimethylammonium chloride (1831) has been used to prepare bitumen emulsions. The bitumen emulsions with low mass fraction of the mixed emulsifier have good stability, meeting the test standard of JTJ052-2000. |
