Q. Bitumen emulsions - difference between anionic emulsions and cationic emulsions?

Bitumen emulsions comprises particles of bitumen dispersed in water by using emulsifying agent. When emulsion breaks, it signifies a change from a liquid to a coherent film with bitumen particles coagulating together. The sign of breaking is the change of colour from brown to black as the colour of emulsion and bitumen is black and brown respectively. 

There are in common two broad types of emulsions, viz.cationic emulsions and anionic emulsions. The breaking of anionic emulsions is dependent on the evaporation of water from bitumen emulsion. It poses difficulty in wet weather condition. Though for cationic emulsions, in place of relying on the evaporation of water the breaking is achieved by chemical coagulation. Therefore cationic emulsions are chiefly useful in wet weather conditions.