Bitumen emulsions are classified according to the electrolytic charge on the droplets and according to their reactivity(Setting Time). Cationic emulsions have droplets which carry a positive electrolytic charge where as anionic emulsions have negatively charged droplets , hence two types of bitumen emulsions.
Cationic – Positively charged droplets
Anionic – Negatively charged droplets
Also bitumen emulsions are named according to reactivity- Rapid setting ( RS) emulsions sets quickly in contact with clean aggregates of low surface area such as chippings, Medium setting ( MS) emulsions sets less quickly than rapid setting emulsions but sufficiently less quicker so that it can be mixed with aggregate of low surface area such as open graded mixes. Slow setting (SS) emulsions mix with reactive aggregates of high surface area. It should be noted that RS emulsions reactive( act quickly) and used with un reactive aggregates.
In naming emulsions according to ASTMD 977, and D2297 – Cationic emulsions are denoted as ;
CRS – Rapid setting
CSS – Slow setting
Where as Anionic emulsions are named as RS, MS, and SS followed by a number and text denoting emulsion viscosity and residue properties—such as SS-1H would mean slow setting anionic emulsion and hard bitumen residue.
The difference between CRS1 and CRS 2 would be CRS2 is with high viscosity. The quick setting (QS) and Cationic quick setting ( CQS)designations have been used to emulsions with medium in reactivity between MS and SS.
Applications for road works.
The summary of Applications are given in the table for quick guide. In general anionic emulsions are used with aggregates whose surface charged positively such as lime rock and cationic emulsions are used with aggregates whose surface charged negatively such as granite rocks.
|Stock pile mix||√||√|
|Pre coated chips||√||√|
|Asphalt Mix paving|
|Slurry and chip seal||√||√|
|In place mixes|
|Fog seal and cement curing||√||√|
|Water proofing coats||√|
|Drive way footpaths sealing||√||√|