ζ Potential as a Measure of Asphalt Emulsion Stability

Asphalt emulsions are most often oil-in-water emulsions widely used in pavement preservation treatments as a result of lower application temperatures and versatility for many pavement preservation applications. Asphalt emulsion stability is an important parameter to consider when choosing the type and formulation of an emulsion for a specific pavement preservation treatment. The stability of asphalt emulsions depends upon the suspension of charged asphalt particles in an electrolyte solution. The particle size and ionic stability play an important role, and ζ potential provides a quantitative measure for tracking the stability of the emulsion. ζ potential is the potential difference between the charged asphalt droplet surface in a dispersed phase and oppositely charged ions in a water–emulsifier solution that make up the continuous phase. A high positive or negative ζ potential indicates a stable emulsion, while ζ potential values approaching zero indicate flocculation. This study will consist of two phases. The first phase presents an experimental design to observe the effect of various formulation parameters on the ζ potential of quick-setting asphalt emulsions and create a statistical model of important effects. The second phase studies the influence of aggregate fines of varying reactivity in the asphalt emulsion and determine the point of zero ζ potential for each formulation. This study aims to introduce the parameter of ζ potential in the design process of slurry-seal pavement preservation treatments and help improve the mixture design process and field performance of quick-setting asphalt emulsion mixtures.