For decades, project contracting officials have been using bitumen-in-water emulsions in the manufacture of cold mixes for wearing and base courses or surface rehabilitations. These emulsions are a complex system in which bitumen and water are solubilised by an emulsifier. Regardless the applications of bitumen emulsions, four main properties are always controlled: viscosity, bitumen/mineral surface adhesion, storage stability and rupture at the mineral surface. The two latter are related to the actions of the emulsifier in the emulsion. It confers stability thanks to electrostatic repulsion between bitumen droplets and decreases the interfacial tension between bitumen and water. The efficiency of this decrease depends on several parameters such as the nature and the amount of the emulsifier, but also on the nature of the bitumen. Indeed, according to the literature available, bitumen is composed of polar molecules which can affect the interfacial tension. More precisely, these molecules are found in asphaltenes and resins. The emulsifier plays also a role during the rupture of the emulsion. It adsorbs at the mineral substrate by electrostatic attraction. Bitumen droplets lack of emulsifier around themselves and coalesce. This phenomenon is known of one of the explanations for the rupture of the emulsion and the filmification of bitumen on the mineral substrate. The kinetics of adsorption of the emulsifier depends on its chemical nature and its amount.
