Surfactants have nonpolar lipophilic (oil-loving) and polar hydrophilic (water-loving) portions in
the same molecule (Figure 5). The molecules concentrate at the interface between water and
bitumen, orientated with the polar group in the water and the nonpolar parts of the molecule in
the oil (Figure 6). This both reduces the energy required to emulsify the asphalt and prevents
coalescence of the droplets once formed. The choice and concentration of emulsifier also largely
determines the charge on the asphalt droplet and the reactivity of the emulsion produced.