ABSTRACT
Durability is the ability to survive and continue to give an acceptable performance. The durability of a flexible road structure depends on the durability of the materials from which it is constructed, in particular the bituminous materials. Bituminous materials may deteriorate in a number of ways. The bitumen itself will harden with exposure to oxygen and through temperature effects, the aggregate may not be of sufficient quality so that some individual particles may break down, or there may be loss of adhesion between the bitumen and aggregate particles. The rate of oxidation is highly dependent on temperature, and is rapid at the high temperatures used for mixing and laying bituminous materials. The measurement of permeability is, in essence, a simple task, achieved by applying a fluid under pressure to one side of a specimen of a bituminous mixture and measuring the resulting flow of fluid at the opposite side.
