What is the typical size of the asphalt droplets in an emulsion?

• A. Mostly 1-5 micrometers
• B. Typically 10-20 micrometers
• C. 0.1-0.5 micrometers
• D. 50-100 micrometers

Answer: (A)

The typical size of asphalt droplets in an emulsion is about 1 to 5 micrometers. This size keeps the asphalt finely dispersed enough to remain suspended in water during storage and handling, while still being large enough to wet aggregate effectively when the emulsion is sprayed onto a surface. Droplets in this micrometer range also break and coalesce at a suitable rate once applied, providing good coating and bonding without clogging spray equipment. Larger droplets (10–20 micrometers or more) can separate or coalesce too readily and cause uneven coverage, while much smaller droplets (0.1–0.5 micrometers) may not spray or break properly and can alter viscosity and stability without added benefit.