What is bitumen emulsion?

With viscosities in the range 0.5–10 Poise at 60°C, bitumen emulsion is of considerably lower viscosity than bitumen itself (100–4,000 Poise), allowing it to be used at lower temperature. Low-temperature techniques for construction and maintenance reduce emissions, reduce energy consumption, avoid oxidation of the bitumen, and are less hazardous than techniques using hot bitumen. They are also more economical and environmentally friendly than cold techniques using cut back bitumen. The environmental benefit of bitumen emulsion is particularly positive when used for in-place or on-site techniques which avoid the energy usage and emissions associated with heating, drying, and haulage of aggregate. The construction of a roadway with cold techniques has been calculated to consume approximately half the energy of one of similar bearing capacity made with hot-mix bitumen. An environmental impact analysis (EIA) technique called “eco-efficiency” has been applied to emulsion maintenance techniques (micro surfacing and chip seal) and it was concluded that the emulsion system had less environmental impact than a thin hot-mix overlay.

Emulsions are water-based and in many cases can be diluted further with water for applications such as dust control and priming. They are also compatible with hydraulic binders like cement and lime as well as water-based polymer dispersions like natural and synthetic latex.

When mixtures of cement, latex, and bitumen emulsion cure, a composite binder is produced with a structure that cannot be duplicated with hot bitumen and with significantly improved properties compared to pure bitumen.

Bitumen emulsion is a dispersion of fine droplets of bitumen in water and has special storage requirements. Storage tanks should be insulated for protection from freezing and efficient use of heat. A skin of bitumen can form on the surface of emulsions when exposed to air. Therefore, it is best to use tall, vertical tanks that expose the least amount of surface area to the air. Most fixed storage tanks are vertical, but horizontal tanks are often used for short-term field storage. Skin formation can be reduced by keeping horizontal tanks full to minimize the area exposed to air.

Side entering propellers located about 3 feet (1 meter) from the tank bottom may be used to prevent surface skin formation. These propellers should be large in diameter and tuned slowly (approximately 60 RPM) to gently circulate the material. Propellers should only be utilized when there is sufficient emulsion for proper mixing.