Anionic Bitumen emulsion in which the droplets of bitumen carry a negative charge.  The anionic bitumen emulsion is derived from the migration of particles of bitumen under an electric field. The droplets migrate toward the anode (positive electrode), and hence the emulsion is called anionic. In an anionic emulsion, there are “billions and billions” of bitumen droplets with the emulsifying agent at the water bitumen interface. The tail portion of the emulsifying agent aligns itself in the bitumen while the positive portion of the head floats around in the water leaving the rest of the head negatively charged and at the surface of the droplet. This imparts a negative charge to all the droplets. Since negatives repel each other, all the droplets repel each other and remain as distinct bitumen drops in suspension.

In the early days of asphalt emulsion production, materials such as ox-blood, clays, and soaps were used as emulsifying agents. As emulsion demand increased, more efficient emulsifying agents were found. Many chemical emulsifiers are now commercially available.

The most common anionic emulsifiers are acids, which are wood-product derivatives such as tall oils, rosins, and lignin’s. Anionic emulsifiers are saponified (turned into soap) by reacting with sodium hydroxide or potassium hydroxide.

Emulsions are further classified on the basis of how quickly the asphalt droplets will coalesce; (i.e., revert to asphalt cement). The terms RS, MS, SS and QS have been adopted to simplify and standardize this classification. They are relative terms only and mean rapid-setting, medium-setting, slow-setting and quick-setting. The tendency to coalesce is closely related to the speed with which an emulsion will become unstable and break after contacting the surface of an aggregate. An RS emulsion has little or no ability to mix with an aggregate, an NIS emulsion is expected to mix with coarse but not fine aggregate, and SS and QS emulsions are designed to mix with fine aggregate, with the QS expected to break more quickly than the SS.

Emulsions are further identified by a series of numbers and letters related to viscosity of the emulsions and hardness of the base asphalt cements. The letter “C” in front of the emulsion type denotes cationic. The absence of the “C” denotes anionic in American Society for Testing and Materials (ASTM) and American Association of State Highway and Transportation Officials (AASHTO) specifications. For example, RS-1 is anionic and CRS-I is cationic.

The numbers in the classification indicate the relative viscosity of the emulsion. For example, an MS-2 is more viscous than an MS-1. The “h” that follows certain grades simply means that harder base asphalt is used. An “s” means that softer base asphalt is used.

The “HF” preceding some of the anionic grades indicates high-float, as measured by the float test. High float emulsions have a gel quality, imparted by the addition of certain chemicals, that permits a thicker asphalt film on the aggregate particles and prevents drain off of asphalt from the aggregate. These grades are used primarily for cold and hot plant mixes, seal coats and road mixes.

BS group has been equipped by DenimoTech full automatic inline emulsion plant which is able to produce different bitumen emulsion grades with superior quality. Some of our anionic emulsions that are classified according ASTM and EN standards are here: