The Effect of pH on the Properties of a Cationic Bitumen Emulsifier

Abstract

Surfactants used in road surface treatments have an optimal application pH value which is an important condition for applications, otherwise stable bitumen emulsions with high solid contents are impossible to achieve. Therefore, a wide range of pH values were employed to investigate its effect on the bitumen/water interfacial properties of a cationic bitumen emulsifier. It is shown that interfacial tension and dilatational modulus have correlations with pH value. The lowest value of interfacial tension declined with the decrease of pH value. The strong acid system has the highest dilatational modulus while this modulus of the neutral system is the lowest. Compared with the neutral system, the maximum of the dilatational modulus also appears in the acid or alkaline system at a relatively low concentration. Physical properties of bitumen emulsions, including storage stability and Zeta potential, show the same changing rule as the interfacial rheology.