Lesson 1/Learning Event 1
Bituminous wearing surfaces lack appreciable bearing action to carry wheel loads over weak
spots in the subbase. For this reason, the subgrade must have an adequate, uniform bearing
strength and the base course must have adequate thickness, bearing capacity, and cohesion.
Structures containing bitumens oxidize, thus losing their resilience with age. This is a major
limitation when a proposed project is to be of a standby nature.