Why are industrial bitumen emulsions classified as heterogeneous mixtures in standards documentation?

Bitumen emulsions are dispersions of bitumen droplets in a continuous water phase stabilized by surfactants and additives. Even when stable, they are not a single uniform phase like a true solution, so standards classify them as heterogeneous mixtures. This classification matters because properties depend on droplet size distribution, temperature, time, and mechanical handling. It also explains why settling, creaming, or phase separation can occur if formulation or storage is poor. Standards reflect this by requiring storage stability tests and emphasizing handling limits.