Base course

Layers in the construction of a mortarless pavement: A.) Subgrade B.) Subbase C.) Base course D.) Paver base E.) Pavers F.) Fine-grained sand

The Base course or basecourse in pavements refers to a layer of material in an asphalt roadway that is placed on top of the subbase, which in turn is placed onto of the subgrade so as to provide a foundation to support the upper layer of the pavement. Generally consisting of a specific type of construction aggregate, it is placed by means of attentive spreading and compacting to a minimum of 95% relative compaction, thus providing the stable foundation needed to support either additional layers of aggregates or the placement of an asphalt concrete wearing course which is applied directly on top of the base course.

Aggregate Base (AB) is typically made of a recipe of mixing different sizes of crushed rock together forming the Aggregate which has certain desirable properties. 3/4 inch Aggregate Base, Class 2, is used in roadways and is an aggregate made of a specific recipe of different sizes and quality of rock inclusive of 3⁄4 in (19.05 mm) to fine dust. An aggregate is normally made from newly quarried rock, or it is sometimes allowed to be made from recycled asphalt concrete and/or Portland cement concrete.