Chemical surface-active agents, which serve as emulsifiers, are classified by the electrochemical charge that is attained when they dissociate in a water solution. In the case of anionic emulsions, the chemical charge is negative. The chemical type and quantity of surface-active agent used in the manufacturing process governs the process in which the resulting asphalt emulsion can be used.
There are three major classifications of emulsion grades: rapid set, medium set and slow set. The terms rapid, medium and slow relate to the amount of time it takes for the emulsion to cure and the amount of mixing that can be performed before the emulsion breaks. Emulsions that allow the longest mixing time generally take the longest to cure, and emulsions that allow very little mixing time are those that set and cure most rapidly.