Types of Aggregate and Binder Bond or Adhesion – Active Adhesion & Passive Adhesion
The coating and adhesion which takes place between the binder and aggregate at the time of "first contact", in the presence of water, is called "Active Adhesion" in HMA.
When the bitumen has the property to coat even wet aggregate, it is called good active adhesion. This is essential at the time of construction, as this would result in a complete bond between bitumen and aggregate. Even thin film of moisture would cause improper weak bonding.
The maintenance and retention strength of the adhesion of aggregate/ binder, is called Passive Adhesion. This is the ability of the bond to withstand influences which cause it to break.