What does "base course aggregate" refer to in pavement construction?

In pavement construction, "base course aggregate" refers to the layer that provides support for the pavement structure. This layer is usually situated between the subgrade and the surface layer (or wearing course) of the pavement. Its primary role is to distribute the load from the pavement above and ensure stability and durability for the overall structure.

Base course aggregates are crucial because they help to enhance the strength of the pavement, provide proper drainage, and prevent deformation under traffic loads. By using appropriate materials and ensuring proper thickness, the base course helps to extend the lifespan of the pavement system.

The other options describe different aspects of pavement construction. The top layer of aggregates pertains to the wearing surface, which is designed for direct contact with traffic. A decorative layer would be focused more on aesthetics rather than functionality. The first layer of aggregates may refer to any layer laid during construction, but it does not specifically convey the structural support role that the base course aggregates fulfill.