Editing Bitumen (section)

=== Rolled asphalt concrete ===
{{Main|Asphalt concrete}}The largest use of bitumen is for making [[asphalt concrete]] for road surfaces; this accounts for approximately 85% of the bitumen consumed in the United States. There are about 4,000 asphalt concrete mixing plants in the US, and a similar number in Europe.<ref name="the_asphalt_paving_industry_2nd_ed">{{cite book | title = The Asphalt Paving Industry: A Global Perspective, 2nd Edition | publisher = National Asphalt Pavement Association and European Asphalt Pavement Association | year = 2011 | location = Lanham, Maryland, and Brussels | url = http://www.asphaltpavement.org/images/stories/GL_101_Edition_3.pdf | access-date = 27 September 2012 | isbn = 978-0-914313-06-9 | archive-date = 7 January 2014 | archive-url = https://web.archive.org/web/20140107203855/http://www.asphaltpavement.org/images/stories/GL_101_Edition_3.pdf }}</ref>
[[File:Pavement layers.png|thumb|[[Asphalt concrete]] is usually placed on top in a road.]]
Asphalt concrete pavement mixes are typically composed of 5% bitumen (known as asphalt cement in the US) and 95% aggregates (stone, sand, and gravel). Due to its highly viscous nature, bitumen must be heated so it can be mixed with the aggregates at the asphalt mixing facility. The temperature required varies depending upon characteristics of the bitumen and the aggregates, but [[Warm-mix asphalt|warm-mix asphalt technologies]] allow producers to reduce the temperature required.<ref name="the_asphalt_paving_industry_2nd_ed" /><ref name="whats_in_your_asphalt_2017_09_fhwa" />

The weight of an asphalt pavement depends upon the [[construction aggregate|aggregate]] type, the bitumen, and the air void content. An average example in the United States is about 112 pounds per square yard, per inch of pavement thickness.<ref name="whats_in_your_asphalt_2017_09_fhwa" />

When maintenance is performed on asphalt pavements, such as [[Pavement milling|milling]] to remove a worn or damaged surface, the removed material can be returned to a facility for processing into new pavement mixtures. The bitumen in the removed material can be reactivated and put back to use in new pavement mixes.<ref>{{cite journal|title=How Should We Express RAP and RAS Contents? |journal=Asphalt Technology E-News |year=2014 |volume=26 |issue=2 |url=http://www.eng.auburn.edu/research/centers/ncat/info-pubs/newsletters/fall-2014/recycledcontents.html |archive-url=https://web.archive.org/web/20150609020500/http://www.eng.auburn.edu/research/centers/ncat/info-pubs/newsletters/fall-2014/recycledcontents.html |archive-date=9 June 2015 }}</ref> With some 95% of paved roads being constructed of or surfaced with asphalt,<ref>{{cite web |url=https://www.fhwa.dot.gov/policyinformation/statistics/2012/hm12.cfm |title=Highway Statistics Series: Public Road Length Miles by Type of Surface and Ownership |publisher=[[Federal Highway Administration]] |date=1 October 2013 }}</ref> a substantial amount of asphalt pavement material is reclaimed each year. According to industry surveys conducted annually by the [[Federal Highway Administration]] and the National Asphalt Pavement Association, more than 99% of the bitumen removed each year from road surfaces during widening and resurfacing projects is reused as part of new pavements, roadbeds, shoulders and embankments or stockpiled for future use.<ref>{{cite web|title=Asphalt Pavement Recycling|url=http://www.asphaltpavement.org/recycling|work=Annual Asphalt Pavement Industry Survey on Recycled Materials and Warm-Mix Asphalt Usage: 2018|publisher=National Asphalt Pavement Association|access-date=14 January 2020|archive-date=23 January 2020|archive-url=https://web.archive.org/web/20200123010627/http://www.asphaltpavement.org/recycling}}</ref>

Asphalt concrete paving is widely used in airports around the world. Due to the sturdiness and ability to be repaired quickly, it is widely used for [[runway]]s.