Editing Concrete (section)

===Mineral admixtures and blended cements===
{{Components of Cement, Comparison of Chemical and Physical Characteristics}}

Inorganic materials that have [[pozzolan]]ic or latent hydraulic properties, these very [[Granularity|fine-grained]] materials are added to the concrete mix to improve the properties of concrete (mineral admixtures),<ref name = "FHWA Admixtures"/> or as a replacement for [[Portland cement]] (blended cements).<ref>{{cite book | author=Kosmatka, S.H. |author2=Panarese, W.C. | title = Design and Control of Concrete Mixtures | publisher=[[Portland Cement Association]] | date = 1988 | location = Skokie, IL | pages = 17, 42, 70, 184 | isbn = 978-0-89312-087-0 }}</ref> Products which incorporate [[limestone]], [[fly ash]], [[Ground granulated blast-furnace slag|blast furnace slag]], and other useful materials with [[Pozzolanic activity|pozzolanic properties]] into the mix, are being tested and used. These developments are ever growing in relevance to minimize the impacts caused by cement use, notorious for being one of the largest producers (at about 5 to 10%) of global [[greenhouse gas emissions]].<ref name=mit>{{Cite web |title=Paving the way to greenhouse gas reductions |url=https://news.mit.edu/2011/concrete-pavements-0829 |access-date=2022-08-13 |website=MIT News {{!}} Massachusetts Institute of Technology |language=en|archive-url=https://web.archive.org/web/20121031015018/http://web.mit.edu/newsoffice/2011/concrete-pavements-0829.html |archive-date=31 October 2012 |date=28 August 2011}}</ref> The use of alternative materials also is capable of lowering costs, improving concrete properties, and recycling wastes, the latest being relevant for [[circular economy]] aspects of the [[Construction Industry|construction industry]], whose demand is ever growing with greater impacts on raw material extraction, waste generation and [[landfill]] practices.
* [[Fly ash]]: A by-product of coal-fired [[power station|electric generating plants]], it is used to partially replace Portland cement (by up to 60% by mass). The properties of fly ash depend on the type of coal burnt. In general, siliceous fly ash is [[Pozzolanic activity|pozzolanic]], while [[calcareous]] fly ash has latent hydraulic properties.<ref>{{cite web |author=U.S. Federal Highway Administration |author-link=Federal Highway Administration |title=Fly Ash |url=http://www.fhwa.dot.gov/infrastructure/materialsgrp/flyash.htm |access-date=24 January 2007 |date=14 June 1999 |archive-url=https://web.archive.org/web/20070621161733/http://www.fhwa.dot.gov/infrastructure/materialsgrp/flyash.htm |archive-date=21 June 2007 }}</ref>
* [[Ground granulated blast furnace slag]] (GGBFS or GGBS): A by-product of [[Steelmaking|steel production]] is used to partially replace [[Portland cement]] (by up to 80% by mass). It has latent hydraulic properties.<ref>{{cite web | author = U.S. Federal Highway Administration | author-link = Federal Highway Administration | title = Ground Granulated Blast-Furnace Slag | url = http://www.fhwa.dot.gov/infrastructure/materialsgrp/ggbfs.htm | access-date = 24 January 2007 | archive-url = https://web.archive.org/web/20070122083859/http://www.fhwa.dot.gov/infrastructure/materialsgrp/ggbfs.htm | archive-date = 22 January 2007 | df = dmy-all }}</ref>
* [[Silica fume]]: A by-product of the production of [[silicon]] and [[ferrosilicon]] [[alloy]]s. Silica fume is similar to fly ash, but has a particle size 100 times smaller. This results in a higher surface-to-volume ratio and a much faster [[Pozzolanic activity|pozzolanic reaction]]. Silica fume is used to increase strength and [[Reinforced concrete structures durability|durability]] of concrete, but generally requires the use of superplasticizers for workability.<ref>{{cite web | author = U.S. Federal Highway Administration | author-link = Federal Highway Administration | title = Silica Fume | url = http://www.fhwa.dot.gov/infrastructure/materialsgrp/silica.htm | access-date = 24 January 2007 | archive-url = https://web.archive.org/web/20070122022403/http://www.fhwa.dot.gov/infrastructure/materialsgrp/silica.htm | archive-date = 22 January 2007 | df = dmy-all }}</ref>
* High reactivity [[metakaolin]] (HRM): Metakaolin produces concrete with [[Strength of materials|strength]] and [[durability]] similar to concrete made with silica fume. While silica fume is usually dark gray or black in color, high-reactivity metakaolin is usually bright white in color, making it the preferred choice for architectural concrete where appearance is important.
* [[Carbon nanofiber]]s can be added to concrete to enhance compressive strength and gain a higher [[Young's modulus]], and also to improve the electrical properties required for strain monitoring, damage evaluation and self-health monitoring of concrete. Carbon fiber has many advantages in terms of mechanical and electrical properties (e.g., higher strength) and self-monitoring behavior due to the high [[Ultimate tensile strength|tensile strength]] and high [[electrical conductivity]].<ref>{{cite journal |last1=Mullapudi |first1=Taraka Ravi Shankar |last2=Gao |first2=Di |last3=Ayoub |first3=Ashraf |title=Non-destructive evaluation of carbon nanofibre concrete |journal=Magazine of Concrete Research |date=September 2013 |volume=65 |issue=18 |pages=1081–1091 |doi=10.1680/macr.12.00187 }}</ref>
* Carbon products have been added to make concrete electrically conductive, for deicing purposes.<ref>{{cite journal |last1=Tuan |first1=Christopher |last2=Yehia |first2=Sherif |title=Evaluation of Electrically Conductive Concrete Containing Carbon Products for Deicing |journal=ACI Materials Journal |date=1 July 2004 |volume=101 |issue=4 |pages=287–293 |url=https://digitalcommons.unomaha.edu/civilengfacpub/26/ }}</ref>
* New research from Japan's [[University of Kitakyushu]] shows that a washed and dried recycled mix of used diapers can be an environmental solution to producing less landfill and using less sand in concrete production. A model home was built in Indonesia to test the strength and durability of the new diaper-cement composite.<ref>{{Cite news |last=Kloosterman |first=Karin |date=23 May 2023 |title=Tiny house built from diapers and concrete |url=https://www.greenprophet.com/2023/05/diaper-concrete-house/ |access-date=6 October 2024 |work=Green Prophet}}</ref>