How does aggregate chemistry influence the choice between cationic and anionic bitumen emulsions?

Aggregate surface charge and mineralogy affect how strongly the emulsion droplets adhere before breaking. Cationic emulsions typically bond better to acidic or siliceous aggregates and many damp surfaces because the positively charged droplets are attracted to negatively charged mineral surfaces. Anionic emulsions can perform well with calcareous or alkaline aggregates in specific conditions, but compatibility must be verified with coating and breaking tests. The practical approach is to run particle charge identification and aggregate coating tests using local aggregates, because dust, clay, and moisture can override theoretical chemistry.