What is an asphalt emulsion?

Solution

• A homogenous mixture of two substances
• Individual molecules of one substance (solute) are
  surrounded by molecules of the other substance (solvent)
• Examples: Table salt in water; Metal alloys; Water (humidity) in air

Colloid or emulsion

• A homogenous mixture of two insoluble substances
• Particles of one substance (dispersed phase) are surrounded by molecules of the other substance (continuous phase)
• Examples: Milk, butter, mayonnaise; Smoke or fog Asphalt

Asphalt

• Composed of crystalline particles generally classified as “asphaltenes”
• Asphaltenes are suspended in an oily liquid continuous phase generally classified as “maltenes”
• The balance of composition determines asphalt physical properties such as rheology

Why emulsify asphalt?

• Viscosity reduction and safer use at lower temperatures
• Change from “oil” based to “water” based system
• Reduced energy use, worker exposure, and job site odor
• Properly formulated emulsion systems provide long term performance benefits

• The asphalt particles will stick together (the emulsion will break) if only water and asphalt are used
• The emulsifier is added to coat the asphalt particle surfaces and keep them from sticking together

• Average 3-7 microns diameter
• Asphalt is usually 57-70% of the emulsion
• 1 gram of asphalt will form more than 10 billion particles
• The total surface area of 1 gram of asphalt is 1-2 m2
• One drop of emulsifier would stabilize as much as 100 billion particles 10-20 m2 of asphalt particle surface area