Editing Cement (section)

===Portland cement blend===
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Portland cement blends are often available as inter-ground mixtures from cement producers, but similar formulations are often also mixed from the ground components at the concrete mixing plant.

'''Portland blast-furnace slag''' cement''', or blast furnace''' cement (ASTM C595 and EN 197-1 nomenclature respectively), contains up to 95% [[ground granulated blast furnace slag]], with the rest Portland clinker and a little gypsum. All compositions produce high ultimate strength, but as slag content is increased, early strength is reduced, while sulfate resistance increases and heat evolution diminishes. Used as an economic alternative to Portland sulfate-resisting and low-heat cements.

'''Portland-fly ash''' cement contains up to 40% [[fly ash]] under ASTM standards (ASTM C595), or 35% under EN standards (EN 197–1). The fly ash is [[pozzolanic]], so that ultimate strength is maintained. Because fly ash addition allows a lower concrete water content, early strength can also be maintained. Where good quality cheap fly ash is available, this can be an economic alternative to ordinary Portland cement.<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|url-status=dead|archive-url=https://web.archive.org/web/20070621161733/http://www.fhwa.dot.gov/infrastructure/materialsgrp/flyash.htm|archive-date=21 June 2007|df=dmy-all}}</ref>

'''Portland pozzolan''' cement includes fly ash cement, since fly ash is a [[pozzolan]], but also includes cements made from other natural or artificial pozzolans. In countries where [[volcanic ash]]es are available (e.g., Italy, Chile, Mexico, the Philippines), these cements are often the most common form in use. The maximum replacement ratios are generally defined as for Portland-fly ash cement.

'''Portland silica fume''' cement. Addition of [[silica fume]] can yield exceptionally high strengths, and cements containing 5–20% silica fume are occasionally produced, with 10% being the maximum allowed addition under EN 197–1. However, silica fume is more usually added to Portland cement at the concrete mixer.<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|url-status=dead|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>

'''Masonry''' cements are used for preparing bricklaying [[mortar (masonry)|mortars]] and [[stuccos]], and must not be used in concrete. They are usually complex proprietary formulations containing Portland clinker and a number of other ingredients that may include limestone, hydrated lime, air entrainers, retarders, waterproofers, and coloring agents. They are formulated to yield workable mortars that allow rapid and consistent masonry work. Subtle variations of masonry cement in North America are plastic cements and stucco cements. These are designed to produce a controlled bond with masonry blocks.

'''Expansive''' cements contain, in addition to Portland clinker, expansive clinkers (usually sulfoaluminate clinkers), and are designed to offset the effects of drying shrinkage normally encountered in hydraulic cements. This cement can make concrete for floor slabs (up to 60&nbsp;m square) without contraction joints.

'''White blended''' cements may be made using white clinker (containing little or no iron) and white supplementary materials such as high-purity [[metakaolin]]. '''Colored''' cements serve decorative purposes. Some standards allow the addition of pigments to produce colored Portland cement. Other standards (e.g., ASTM) do not allow pigments in Portland cement, and colored cements are sold as blended hydraulic cements.

'''Very finely ground''' cements are cement mixed with sand or with slag or other pozzolan type minerals that are extremely finely ground together. Such cements can have the same physical characteristics as normal cement but with 50% less cement, particularly because there is more surface area for the chemical reaction. Even with intensive grinding they can use up to 50% less energy (and thus less carbon emissions) to fabricate than ordinary Portland cements.<ref name=Justnes>{{cite journal|title=Mechanism for performance of energetically modified cement versus corresponding blended cement|url=http://www.emccement.com/Articles/EMC%20mechanism%20paper.pdf|archive-url=https://web.archive.org/web/20110710185446/http://www.emccement.com/Articles/EMC%20mechanism%20paper.pdf|archive-date=10 July 2011|journal=Cement and Concrete Research|volume=35|issue=2|year=2005|pages=315–323|doi=10.1016/j.cemconres.2004.05.022|last1=Justnes|first1=Harald|last2=Elfgren|first2=Lennart|last3=Ronin|first3=Vladimir}}</ref>