Adhesion Promoter Conventional Anti-stripping Agents

The chemical affinity between bitumen and aggregate can be improved by the addition of very small quantities of chemicals which change the nature of the aggregate or the bitumen to have more affinity for the other.
These chemicals are known as "Anti-stripping Agents" "Anti-stripping Additive" or "adhesion promoters".
Since the stability of bituminous pavement largely depends on adhesion between bitumen and aggregates, the ionic nature of aggregate is an important factor explaining the problem of stripping that differ for different type of aggregates.
This also explains non-formation of stable bond in bituminous pavement construction. (refer IS-6241:1971 "Method of test for determination of stripping value of road aggregates, ASTM D3625 "The Boiling Water Test"). The widely accepted class of Anti-stripping agents belong to Fatty Polyamine group of chemicals where even in a very small dose they provide :

• Active and passive adhesion between Bitumen and the aggregates,
• Being surface active agents they provide bituminous wetting action (in some cases, reduced requirement of Bitumen), and prolongs the pavement life by slowing the ageing process.