ABSTRACT
Bituminous materials consist of a graded aggregate bound together with bitumen. There are two sources of bitumen: natural deposits and refinery bitumen. The most important deposit of this type, and the only one used as a source of road bitumen in the United Kingdom, is the Trinidad Lake. Resistance to impact loads is also required for road aggregates. The skid resistance of a road surface is provided largely by the aggregate exposed at the surface. There are two components, which are referred to as macrotexture and microtexture. Microtexture refers to the surface texture of individual particles and varies according to the type of aggregate. Here, it is important to use an aggregate which not only has a rough surface texture, but also will retain that texture under the action of traffic. This is assessed using the polished stone value test.
