Editing Concrete block (section)

== Composition ==

Concrete blocks are made from [[Casting|cast]] [[concrete]] (e.g. [[portland cement]] and [[Construction aggregate|aggregate]], usually sand and fine [[gravel]], for high-density blocks). In the western United States, where they are easily obtainable, porous lava rock gravels are used for weight reduction. They also have an added decorative effect to certain types of block, such as split-face, due to their distinct red and black colors. Lower-density blocks may use [[industrial waste]]s, such as [[fly ash]] or [[bottom ash]],<ref>{{cite web|url=http://www.independent.co.uk:80/news/world/middle-east/green-cake-new-invention-concrete-gaza-strip-war-hamas-israeli-blockade-rebuildng-a7517721.html|archive-url=https://web.archive.org/web/20180228234735/http://www.independent.co.uk/news/world/middle-east/green-cake-new-invention-concrete-gaza-strip-war-hamas-israeli-blockade-rebuildng-a7517721.html|archive-date=28 February 2018|title=A new invention by two female engineers could be the solution to Gaza's rebuilding problems - The Independent|work=The Independent |date=28 February 2018|access-date=20 October 2018}}</ref><ref>{{cite web|url=http://www.middleeasteye.net/in-depth/features/green-cake-cheaper-alternative-help-reconstruction-besieged-gaza-681019806|archive-url=https://web.archive.org/web/20170417085423/http://www.middleeasteye.net/in-depth/features/green-cake-cheaper-alternative-help-reconstruction-besieged-gaza-681019806|archive-date=17 April 2017|title=Rebuilding Gaza: 'Green Cake' could be the phoenix rising from Gaza's ashes - Middle East Eye|date=17 April 2017|access-date=20 October 2018}}</ref> as an aggregate.<ref>{{cite web|url=http://www.concrete-machinery.com/ |title=Block Making Machine aggregate example|publisher=Web Editor}}</ref>

[[Recycled]] materials, such as post-consumer glass, slag cement, or recycled aggregate, are often used in the composition of the blocks.<ref>{{Cite web|url=https://www.echelonmasonry.com/resources/masonry-and-leed-v4|title=Masonry & LEED v4: Continuing Education from Echelon Masonry|website=www.echelonmasonry.com|access-date=2019-02-12}}</ref> Use of recycled materials within blocks can create different appearances in the block, such as a [[terrazzo]] finish, and may help the finished structure earn [[Leadership in Energy and Environmental Design|LEED certification]].

Lightweight blocks can also be produced using [[autoclaved aerated concrete]]; these are widely used for construction in Finland and other Scandinavian countries, as well as in the UK and central Europe, for the material's inherent thermal insulation characteristics, as are [[expanded clay aggregate]] blocks.