Asphalt emulsion is a combination of three basic ingredients, asphalt, water, and small amount of an emulsifying agent. In the same process, these components are introduced into a mechanism known as a colloid mill, which shears the asphalt into tiny droplets. The emulsifier, which is a surface-active agent, keeps the asphalt droplets in a stable suspension and controls the breaking time. The result is a liquid product with a consistency ranging from that of milk to heavy cream, which can be used in cold processes for road construction and maintenance.
Asphalt emulsion does not require a petroleum solvent to make it liquid and in most cases asphalt emulsions can be used without additional heat. Both of these factors contribute to energy savings. Additionally, asphalt emulsions offer great flexibility in their application since they offer the end-user a great variety of characteristics not found in other paving and maintenance materials. Asphalt emulsions are environmentally friendly. There are little or no hydrocarbon emissions created with their use.
Asphalt emulsions were first prepared in the early part of the 20th century and today they are used all over the world. The use of asphalt emulsions is growing and 10-20% of all asphalt is used in the form of asphalt emulsions.
Asphalt emulsions are classified into three categories; anionic, cationic, or nonionic. The anionic and cationic classes refer to the electrical charges surrounding the asphalt particles. The absence of the letter "C" denotes anionic emulsions. Asphalt emulsions are further classified on the basis of how quickly they coalesce; i.e., revert to asphalt cement. The terms RS (Rapid Set), MS (Medium Set), SS (slow set), and QS (Quick Set) have been adopted to simplify and standardize this classification. Additionally, trailing numbers are used to delineate the relative viscosity if the emulsion and the letters "h" and "s" indicate whether a hard or soft base asphalt is used to make the asphalt emulsions. Thus, a CSS-1h is a cationic slow set emulsion with a relatively low asphalt emulsion viscosity made with a hard base asphalt.
Driveway sealers, roofing repair materials, caulks and mastics may contain specially formulated asphalt emulsions.
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Asphalt Emulsion Manufacturers Association