# Base course

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{{Short description|Layer of material in asphalt roadways}}
thumb|Class 3 Road Base
[[Image:MortarlessPavement.jpg|thumb|right|Layers in the construction of a mortarless pavement:<br>A. [Subgrade](/source/Subgrade)<br> B. [Subbase](/source/Subbase_(pavement))<br>C. Base course<br>D. [Paver base](/source/Paver_base) as ''binder course''<br>E. [Pavers](/source/Paver_(flooring)) as ''[wearing course](/source/wearing_course)''<br>F. Fine-grained [sand](/source/sand)]]

The '''base course''' or '''basecourse''' in pavements is a layer of material in an [asphalt](/source/Asphalt_concrete) [road](/source/road)way, race track, riding arena, or sporting field. It is located under the surface layer consisting of the ''[wearing course](/source/wearing_course)'' 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 {{convert|4|to|6|in|mm|lk=on|order=flip}} and is governed by underlying layer properties. Generally made of a [construction aggregate](/source/construction_aggregate), it is spread and compacted to at least 95% relative compaction, thus providing a stable foundation for additional layers of material.<ref>{{cite book|title=Handbook of Road Technology|first=M. G.|last= Lay|edition=4|publisher=Taylor & Francis|year=2009|isbn=978-0203892534}}</ref><ref>{{cite book|first1=D. R.|last1=Phatak|first2=H. K.|last2=Gite|title=Highway Engineering|publisher=Nirali Prakashan|isbn=978-8185790923}}</ref>

[Aggregate base](/source/Aggregate_base) (AB) is typically a mix of different sizes of crushed rock ''{{Convert|20|mm|in|frac=8|abbr=on|disp=or}} Aggregate Base, Class 2'', is used in roadways and consists of rock particles of size {{convert|3/4|in|mm|-1|abbr=on|order=flip}} and less. 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.

== See also ==
* [Track bed](/source/Track_bed)

==References==
{{reflist}}

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

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Adapted from the Wikipedia article [Base course](https://en.wikipedia.org/wiki/Base_course) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Base_course?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.