In road construction, oil in water emulsion are the most common type. Hydrophilic emulsifiers form oil in water emulsions (O/W), while oleophilic surfactants form water in oil emulsions (W/O). The former selectively interact with water, while the latter interact with bitumen. ![]() Emulsifiers are classified as hydrophilic or oleophilic. However, the role of the surfactant is not limited to just that reduction its main purpose is to form mechanically strong layers on the surface of the internal phase droplets, which prevent the droplets from aggregation.įormation of emulsion of certain types is defined by the physical and chemical properties of the surfactant, in particular, its ability to selectively interact with the environment. reducing the interfacial tension on the boundary between the phases. The surfactant is adsorbed on the surfaces of the dispersed droplets of bitumen or tar. to reduce the difference of interfacial tensions of bitumen and water this can be achieved by the introduction of emulsifiers. The interfacial tension between the phases must be reduced to produce stable bitumen or tar emulsions with water for road construction, i.e. The bigger the difference between the physical properties of the substances, the higher the interfacial tension between the phases, and the lower the stability of the entire system.īitumen and tar are very different from water physically, so in most cases, mechanical dispersion of these materials in water does not result in emulsification. The stability of the emulsion depends on the interfacial tension on the boundary between the internal and external phases. The distributed substance is called the internal or dispersed phase, while the medium in which the droplets are suspended, is called continuous or external phase. Emulsions with solid emulsifiers are coarse emulsions. Viscous emulsions, which include highly concentrated emulsions and emulsion with solid powdered emulsifiers, are referred to as pastes. Emulsion with bitumen or tar content above 70-75% are referred to as high concentration emulsions. The content of bitumen or tar in road construction emulsions can reach 50-65%. Examples of such emulsions are bitumen or tar and water. ![]() Emulsions are colloidal dispersed systems, where one liquid is dispersed in another in the form of small droplets without mixing.
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