The base course or basecourse in pavements is a layer of material in an

asphalt Asphalt, also known as bitumen (, ), is a sticky, black, highly viscous liquid or semi-solid form of petroleum. It may be found in natural deposits or may be a refined product, and is classed as a pitch. Before the 20th century, the term ...

road A road is a linear way for the conveyance of traffic that mostly has an improved surface for use by vehicles (motorized and non-motorized) and pedestrians. Unlike streets, the main function of roads is transportation. There are many types o ...

way, race track, riding arena, or sporting field. It is located under the surface layer consisting of the ''

wearing course The wearing course is the upper layer in roadway, airfield, and dockyard construction. The term 'surface course' is sometimes used, however this term is slightly different as it can be used to describe very thin surface layers such as chip seal. In ...

'' and sometimes an extra ''binder course''. If there is a sub-base course, the base course is constructed directly above this layer. Otherwise, it is built directly on top of the subgrade. Typical base course thickness ranges from and is governed by underlying layer properties. Generally consisting of a specific type of

construction aggregate Construction aggregate, or simply aggregate, is a broad category of coarse- to medium-grained particulate material used in construction, including sand, gravel, crushed stone, slag, recycled concrete and geosynthetic aggregates. 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 Asphalt concrete (commonly called asphalt, blacktop, or pavement in North America, and tarmac, bitumen macadam, or rolled asphalt in the United Kingdom and the Republic of Ireland) is a composite material commonly used to surface roads, parki ...

which is applied directly on top of the base course.

Aggregate base Aggregate base is a construction aggregate typically composed of crushed rock capable of passing through a rock screen. The component particles will vary in size from 20 mm down to dust. The material can be made of virgin (newly mined) rock, ...

(AB) is typically made of a recipe of mixing different sizes of crushed rock together forming the aggregate which has certain desirable properties. '' 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 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.

References

{{DEFAULTSORT:Base Course Pavement engineering Road transport Road infrastructure

See also

References