Editing Cement

{{Short description|Hydraulic binder used in the composition of mortar and concrete}}
{{Other uses}}
{{Distinguish|Concrete}}
{{Use dmy dates|date=November 2024}}
[[File:USMC-110806-M-IX060-148.jpg|thumb|Cement powder in a bag, ready to be mixed with aggregates and water.<ref>{{Cite web|title=Draeger: Guide for selection and use of filtering devices|url=https://www.draeger.com/Library/Content/ab-selection-guide-fl-9045782-en-1502-3.pdf|date=22 May 2020|publisher=Draeger|url-status=live|archive-url=https://web.archive.org/web/20200522143702/https://www.draeger.com/Library/Content/ab-selection-guide-fl-9045782-en-1502-3.pdf|archive-date=22 May 2020|access-date=22 May 2020}}</ref>]]
[[File:Year book - photo flashes showing Toledo's phenomenal progress, thriving industries and wonderful resources - DPLA - ac95c5ef8efd2394c21e2b6edcd01d94 (page 94) (cropped).jpg|thumb|right|Cement block construction examples from the Multiplex Manufacturing Company of Toledo, Ohio, in 1905]]

A '''cement''' is a [[binder (material)|binder]], a [[chemical substance]] used for construction that [[solidification|set]]s, hardens, and adheres to other [[material]]s to bind them together. Cement is seldom used on its own, but rather to bind sand and gravel ([[construction aggregate|aggregate]]) together. Cement mixed with fine aggregate produces [[mortar (masonry)|mortar]] for masonry, or with [[sand]] and [[gravel]], produces [[concrete]]. Concrete is the most widely used material in existence and is behind only water as the planet's most-consumed resource.<ref name="Rodgers-2018">{{Cite news|url=https://www.bbc.com/news/science-environment-46455844|title=The massive {{chem|CO|2}} emitter you may not know about|last=Rodgers|first=Lucy|date=17 December 2018|publisher=BBC News|access-date=17 December 2018}}</ref>

Cements used in construction are usually [[inorganic]], often [[lime (material)|lime]]- or [[calcium silicate]]-based, and are either '''hydraulic''' or less commonly '''non-hydraulic''', depending on the ability of the cement to set in the presence of water (see [[Lime mortar#Hydraulic and non-hydraulic lime|hydraulic and non-hydraulic lime plaster]]).

'''Hydraulic cements''' (e.g., [[Portland cement]]) set and become [[adhesive]] through a [[chemical reaction]] between the dry ingredients and water. The chemical reaction results in mineral [[hydrate]]s that are not very water-soluble. This allows setting in wet conditions or under water and further protects the hardened material from chemical attack. The chemical process for hydraulic cement was found by ancient Romans who used [[volcanic ash]] ([[pozzolana]]) with added lime (calcium oxide).

'''Non-hydraulic cement''' (less common) does not set in wet conditions or under water. Rather, it sets as it dries and reacts with [[carbon dioxide]] in the air. It is resistant to attack by chemicals after setting.

The word "cement" can be traced back to the Ancient Roman term {{lang|la|[[opus caementicium]]}}, used to describe masonry resembling modern concrete that was made from crushed rock with burnt lime as binder.<ref>{{Citation |last=Cement Analyst |first=Milan A |title=Opus Caementicium |date=2015 |work=Innovative Vaulting in the Architecture of the Roman Empire: 1st to 4th Centuries CE |pages=19–38 |editor-last=Lancaster |editor-first=Lynne C. |url=https://www.cambridge.org/core/books/abs/innovative-vaulting-in-the-architecture-of-the-roman-empire/opus-caementicium/F17A6BFF99071417F6E8B556BFDECCDA |access-date=2025-03-07 |place=Cambridge |publisher=Cambridge University Press |isbn=978-1-107-05935-1}}</ref> The volcanic ash and pulverized brick supplements that were added to the burnt lime, to obtain a [[hydraulic binder]], were later referred to as {{lang|la|cementum}}, {{lang|la|cimentum}}, ''cäment'', and ''cement''. In modern times, organic polymers are sometimes used as cements in concrete.

World production of cement is about 4.4 billion tonnes per year (2021, estimation),<ref name=usgs_report>{{Cite web|title=Cement|url=https://pubs.usgs.gov/periodicals/mcs2022/mcs2022-cement.pdf|access-date=26 September 2023|publisher=United States Geological Survey (USGS)}}</ref><ref name=chathamhouse/> of which about half is made in China, followed by India and Vietnam.<ref name=usgs_report/><ref name=Hargreaves/>

The cement production process is responsible for nearly 8% (2018) of global {{CO2}} emissions,<ref name=chathamhouse/> which includes heating raw materials in a [[cement kiln]] by fuel combustion and release of {{CO2}} stored in the calcium carbonate (calcination process). Its hydrated products, such as concrete, gradually reabsorb atmospheric {{CO2}} (carbonation process), compensating for approximately 30% of the initial {{CO2}} emissions.<ref>{{Cite journal|last1=Cao|first1=Zhi|last2=Myers|first2=Rupert J.|last3=Lupton|first3=Richard C.|last4=Duan|first4=Huabo|last5=Sacchi|first5=Romain|last6=Zhou|first6=Nan|last7=Reed Miller|first7=T.|last8=Cullen|first8=Jonathan M.|last9=Ge|first9=Quansheng |last10=Liu |first10=Gang|date=29 July 2020|title=The sponge effect and carbon emission mitigation potentials of the global cement cycle|journal=Nature Communications|language=en|volume=11|issue=1|pages=3777|doi=10.1038/s41467-020-17583-w|pmid=32728073|pmc=7392754|bibcode=2020NatCo..11.3777C|issn=2041-1723|doi-access=free}}</ref>

==Chemistry==
Cement materials can be classified into two distinct categories: hydraulic cements and non-hydraulic cements according to their respective setting and hardening mechanisms. Hydraulic cement setting and hardening involves hydration reactions and therefore requires water, while non-hydraulic cements only react with a gas and can directly set under air.

===Hydraulic cement===
[[File:LDClinkerScaled.jpg|thumb|[[Clinker (cement)|Clinker]] nodules produced by sintering at 1450&nbsp;°C]]

By far the most common type of cement is '''hydraulic cement''', which hardens by [[hydration reaction|hydration]] (when water is added) of the [[Clinker (cement)|clinker]] minerals. Hydraulic cements (such as [[Portland cement]]) are made of a mixture of silicates and oxides, the four main mineral phases of the clinker, abbreviated in the [[cement chemist notation]], being:
:C<sub>3</sub>S: [[alite]] (3CaO·SiO<sub>2</sub>);
:C<sub>2</sub>S: [[belite]] (2CaO·SiO<sub>2</sub>);
:C<sub>3</sub>A: [[tricalcium aluminate]] (3CaO·Al<sub>2</sub>O<sub>3</sub>) (historically, and still occasionally, called ''celite'');
:C<sub>4</sub>AF: [[brownmillerite]] (4CaO·Al<sub>2</sub>O<sub>3</sub>·Fe<sub>2</sub>O<sub>3</sub>).

The silicates are responsible for the cement's mechanical properties — the tricalcium aluminate and brownmillerite are essential for the formation of the liquid phase during the [[sintering]] ([[Pottery#Firing|firing]]) process of clinker at high temperature in the [[Cement kiln|kiln]]. The chemistry of these reactions is not completely clear and is still the object of research.<ref>{{Cite web|url=http://cee.mit.edu/cee-in-focus/2011/spring/cement-structure|archive-url=https://web.archive.org/web/20130221105202/http://cee.mit.edu/cee-in-focus/2011/spring/cement-structure|url-status=dead|title=Cement's basic molecular structure finally decoded (MIT, 2009)|archive-date=21 February 2013}}</ref>

First, the [[limestone]] (calcium carbonate) is burned to remove its carbon, producing [[Calcium oxide|lime]] (calcium oxide) in what is known as a [[calcination]] reaction. This single chemical reaction is a major emitter of global [[Climate change#Greenhouse gases|carbon dioxide emissions]].<ref>{{cite web|title=EPA Overview of Greenhouse Gases|date=23 December 2015|url=https://www.epa.gov/ghgemissions/overview-greenhouse-gases}}</ref>
:<chem>CaCO3 -> CaO + CO2</chem>

The lime reacts with silicon dioxide to produce dicalcium silicate and tricalcium silicate.
:<chem>2CaO + SiO2 -> 2CaO.SiO2</chem>
:<chem>3CaO + SiO2 -> 3CaO.SiO2</chem>

The lime also reacts with aluminium oxide to form tricalcium aluminate.
:<chem>3CaO + Al2O3 -> 3CaO.Al2O3</chem>

In the last step, calcium oxide, aluminium oxide, and ferric oxide react together to form brownmillerite.
:<chem>4CaO + Al2O3 + Fe2O3 -> 4CaO.Al2O3.Fe2O3</chem>

===Non-hydraulic cement===
[[File:Calcium oxide powder.JPG|thumb|[[Calcium oxide]] obtained by [[thermal decomposition]] of [[calcium carbonate]] at high temperature (above 825&nbsp;°C).]]

A less common form of cement is '''non-hydraulic cement''', such as [[slaked lime]] ([[calcium oxide]] mixed with water), which hardens by [[carbonation]] in contact with [[carbon dioxide]], which is present in the air (~&nbsp;412 vol. ppm ≃ 0.04 vol.&nbsp;%). First [[calcium oxide]] (lime) is produced from [[calcium carbonate]] ([[limestone]] or [[chalk]]) by [[calcination]] at temperatures above 825&nbsp;°C (1,517&nbsp;°F) for about 10 hours at [[atmospheric pressure]]:
:<chem>CaCO3 -> CaO + CO2</chem>
The calcium oxide is then ''spent'' (slaked) by mixing it with water to make slaked lime ([[calcium hydroxide]]):
:<chem>CaO + H2O -> Ca(OH)2</chem>
Once the excess water is completely evaporated (this process is technically called ''setting''), the carbonation starts:
:<chem>Ca(OH)2 + CO2 -> CaCO3 + H2O</chem>
This reaction is slow, because the [[partial pressure]] of carbon dioxide in the air is low (~&nbsp;0.4&nbsp;millibar). The carbonation reaction requires that the dry cement be exposed to air, so the slaked lime is a non-hydraulic cement and cannot be used under water. This process is called the ''lime cycle''.

==History==

Perhaps the earliest known occurrence of cement is from twelve million years ago. A deposit of cement was formed after an occurrence of oil shale located adjacent to a bed of limestone burned by natural causes. These ancient deposits were investigated in the 1960s and 1970s.<ref name=MAST>{{cite web|title=The History of Concrete|url=http://matse1.matse.illinois.edu/concrete/hist.html|publisher=Dept. of Materials Science and Engineering, University of Illinois, Urbana-Champaign|access-date=8 January 2013|url-status=live|archive-url=https://web.archive.org/web/20121127052951/http://matse1.matse.illinois.edu/concrete/hist.html|archive-date=27 November 2012}}</ref>

===Alternatives to cement used in antiquity===
Cement, chemically speaking, is a product that includes [[Calcium oxide|lime]] as the primary binding ingredient, but is far from the first material used for cementation. The [[Babylonia]]ns and [[Assyria]]ns used [[bitumen]] (asphalt or [[pitch (resin)|pitch]]) to bind together burnt brick or [[alabaster]] slabs. In [[Ancient Egypt]], stone blocks were cemented together with a [[Mortar (masonry)|mortar]] made of [[sand]] and roughly burnt [[gypsum]] (CaSO<sub>4</sub> · 2H<sub>2</sub>O), which is [[plaster]] of Paris, which often contained calcium carbonate (CaCO<sub>3</sub>),<ref name="Blezard"/>

===Ancient Greece and Rome===
Lime (calcium oxide) was used on [[Crete]] and by the [[Ancient Greeks]]. There is evidence that the [[Minoans]] of Crete used crushed potsherds as an artificial [[pozzolan]] for hydraulic cement.<ref name="Blezard"/> Nobody knows who first discovered that a combination of [[Slaked lime|hydrated non-hydraulic lime]] and a pozzolan produces a hydraulic mixture (see also: [[Pozzolanic reaction]]), but such concrete was used by the Greeks, specifically the [[Ancient Macedonians]],<ref>Brabant, Malcolm (12 April 2011). [https://www.bbc.co.uk/news/av/world-europe-13046299/macedonians-created-cement-three-centuries-before-the-romans Macedonians created cement three centuries before the Romans] {{webarchive|url=https://web.archive.org/web/20190409224527/https://www.bbc.co.uk/news/av/world-europe-13046299/macedonians-created-cement-three-centuries-before-the-romans |date=9 April 2019 }}, ''BBC News''.</ref><ref>{{cite web|url=http://www.ashmolean.org/exhibitions/current/?timing=current&id=57&exhibitionYear=2011|title=Heracles to Alexander The Great: Treasures From The Royal Capital of Macedon, A Hellenic Kingdom in the Age of Democracy|archive-url=https://web.archive.org/web/20120117164459/http://www.ashmolean.org/exhibitions/current/?timing=current&id=57&exhibitionYear=2011|archive-date=17 January 2012|publisher=Ashmolean Museum of Art and Archaeology, University of Oxford}}</ref> and three centuries later on a large scale by [[Roman engineers]].<ref>{{Cite book|last=Hill|first=Donald|url={{google books|plainurl=y|id=oMceAgAAQBAJ|page=106}}|title=A History of Engineering in Classical and Medieval Times|date=19 November 2013|publisher=Routledge|isbn=978-1-317-76157-0|language=en|page=106}}</ref><ref>{{Cite web|url=https://www.understanding-cement.com/history.html|title=History of cement|website=www.understanding-cement.com|access-date=17 December 2018}}</ref><ref>{{Cite web|url=https://io9.gizmodo.com/how-the-ancient-romans-made-better-concrete-than-we-do-1672632593|title=How the Ancient Romans Made Better Concrete Than We Do Now|last=Trendacosta|first=Katharine|date=18 December 2014|website=Gizmodo}}</ref>

{{Blockquote|text=There is... a kind of powder which from natural causes produces astonishing results. It is found in the neighborhood of [[Baiae]] and in the country belonging to the towns round about [[Mount Vesuvius]]. This substance when mixed with lime and rubble not only lends strength to buildings of other kinds but even when piers of it are constructed in the sea, they set hard underwater.|author=[[Marcus Vitruvius Pollio]]|source=Liber II, ''De Architectura'', Chapter VI "Pozzolana" Sec. 1|title=}}

The Greeks used [[Tuff|volcanic tuff]] from the island of [[Thera]] as their pozzolan and the Romans used crushed [[volcanic ash]] (activated [[aluminium silicate]]s) with lime. This mixture could set under water, increasing its resistance to corrosion like rust.<ref name="Natural Pozzolan Association">{{cite web|url=https://pozzolan.org/improve-concrete.html|title=How Natural Pozzolans Improve Concrete|work=Natural Pozzolan Association|access-date=7 April 2021}}</ref> The material was called ''pozzolana'' from the town of [[Pozzuoli]], west of [[Naples]] where volcanic ash was extracted.<ref name=Ridi2010>{{Cite journal|first=Francesca|last=Ridi|title=Hydration of Cement: still a lot to be understood|journal=La Chimica & l'Industria|url=http://www.soc.chim.it/sites/default/files/chimind/pdf/2010_3_110_ca.pdf|issue=3|date=April 2010|pages=110–117|url-status=live|archive-url=https://web.archive.org/web/20151117023718/http://www.soc.chim.it/sites/default/files/chimind/pdf/2010_3_110_ca.pdf|archive-date=17 November 2015}}</ref> In the absence of pozzolanic ash, the Romans used powdered brick or pottery as a substitute and they may have used crushed tiles for this purpose before discovering natural sources near Rome.<ref name="Blezard"/> The huge [[dome]] of the [[Pantheon, Rome|Pantheon]] in Rome and the massive [[Baths of Caracalla]] are examples of ancient structures made from these concretes, many of which still stand.<ref>{{cite web|url=http://www.chamorro.com/community/pagan/Azmar_Natural_Pozzolan.pdf|title=Pure natural pozzolan cement|access-date=12 January 2009|url-status=bot: unknown|archive-url=https://web.archive.org/web/20061018162743/http://www.chamorro.com/community/pagan/Azmar_Natural_Pozzolan.pdf|archive-date=18 October 2006}}. chamorro.com</ref><ref name="Rodgers-2018" /> The vast system of [[Roman aqueduct]]s also made extensive use of hydraulic cement.<ref>Russo, Ralph (2006) [http://www.yale.edu/ynhti/curriculum/units/2006/4/06.04.04.x.html "Aqueduct Architecture: Moving Water to the Masses in Ancient Rome"] {{webarchive|url=https://web.archive.org/web/20081012075152/http://www.yale.edu/ynhti/curriculum/units/2006/4/06.04.04.x.html |date=12 October 2008 }}, in ''Math in the Beauty and Realization of Architecture'', Vol. IV, Curriculum Units by Fellows of the Yale-New Haven Teachers Institute 1978–2012, Yale-New Haven Teachers Institute.</ref> Roman concrete was rarely used on the outside of buildings. The normal technique was to use brick facing material as the [[formwork]] for an infill of [[Mortar (masonry)|mortar]] mixed with an [[Construction aggregate|aggregate]] of broken pieces of stone, brick, [[Sherd|potsherds]], recycled chunks of concrete, or other building rubble.<ref name="Cowan 1975">{{cite journal|doi=10.1080/00038628.1975.9696342|title=An Historical Note on Concrete|journal=Architectural Science Review|volume=18|pages=10–13|year=1975|last1=Cowan|first1=Henry J.}}</ref>

===Mesoamerica===
Lightweight concrete was designed and used for the construction of structural elements by the [[pre-Columbian]] builders who lived in a very advanced civilisation in [[El Tajin]] near Mexico City, in Mexico.  A detailed study of the composition of the aggregate and binder show that the aggregate was pumice and the binder was a pozzolanic cement made with volcanic ash and lime.<ref>{{Cite book|last1=Cabrera|first1=J. G.|last2=Rivera-Villarreal|first2=R.|last3=Sri Ravindrarajah|first3=R.|chapter=Properties and Durability of a Pre-Columbian Lightweight Concrete |year=1997|title=SP-170: Fourth CANMET/ACI International Conference on Durability of Concrete|journal=Symposium Paper / American Concrete Institute, International Concrete Abstracts Portal|volume=170|issue=SP-170: Fourth CANMET/ACI International Conference on Durability of Concrete|pages=1215–1230|doi=10.14359/6874|isbn=9780870316692|s2cid=138768044}}</ref>

=== Middle Ages ===
Any preservation of this knowledge in literature from the [[Middle Ages]] is unknown, but medieval [[masonry|masons]] and some military engineers actively used hydraulic cement in structures such as [[canal]]s, fortresses, [[harbor]]s, and [[Shipyard|shipbuilding facilities]].<ref name="Sismondo">{{Cite book|last=Sismondo|first=Sergio|url={{google books|plainurl=y|id=LescwF8FBigC}}|title=An Introduction to Science and Technology Studies|date=20 November 2009|publisher=Wiley|isbn=978-1-4443-1512-7|language=en}}</ref><ref name="Mukerji">{{Cite book|last=Mukerji|first=Chandra|url={{google books|plainurl=y|id=fRwNRrFswv8C|page=121}}|title=Impossible Engineering: Technology and Territoriality on the Canal Du Midi|date=2009|page=121|publisher=Princeton University Press|isbn=978-0-691-14032-2|language=en}}</ref> A mixture of lime mortar and aggregate with brick or stone facing material was used in the [[Eastern Roman Empire]] as well as in the West into the [[Gothic architecture|Gothic period]]. The German [[Rhineland]] continued to use hydraulic mortar throughout the Middle Ages, having local pozzolana deposits called [[trass]].<ref name="Cowan 1975"/>

===16th century===
[[Tabby (cement)|Tabby]] is a [[building material]] made from oyster shell lime, sand, and whole oyster shells to form a concrete. The Spanish introduced it to the Americas in the sixteenth century.<ref name="books.google.com"><{{Cite journal|last=Taves|first=Loren Sickels|url={{google books|plainurl=y|id=VJY1hE0W9UoC|page=5}}|page=5|title=Tabby Houses of the South Atlantic Seaboard|journal=Old-House Journal|date=27 October 2015|publisher=Active Interest Media, Inc.|language=en}}</ref>

===18th century===
The technical knowledge for making hydraulic cement was formalized by French and British engineers in the 18th century.<ref name="Sismondo"/>

[[John Smeaton]] made an important contribution to the development of cements while planning the construction of the third [[Eddystone Lighthouse]] (1755–59) in the [[English Channel]] now known as [[Smeaton's Tower]]. He needed a hydraulic mortar that would set and develop some strength in the twelve-hour period between successive high [[tide]]s. He performed experiments with combinations of different [[limestone]]s and additives including trass and [[pozzolana]]s<ref name="Blezard">{{Cite book|editor-last=Hewlett|editor-first=Peter|url={{google books|plainurl=y|id=v1JVu4iifnMC}}|title=Lea's Chemistry of Cement and Concrete|date=12 November 2003|publisher=Elsevier|isbn=978-0-08-053541-8|language=en|last=Blezard|first=Robert G.|chapter=The History of Calcareous Cements|pages=1–24}}</ref> and did exhaustive market research on the available hydraulic limes, visiting their production sites, and noted that the "hydraulicity" of the lime was directly related to the [[clay]] content of the [[limestone]] used to make it. Smeaton was a civil engineer by profession, and took the idea no further.

In the [[Atlantic coastal plain|South Atlantic seaboard]] of the United States, [[Tabby (cement)|tabby]] relying on the oyster-shell [[midden]]s of earlier Native American populations was used in house construction from the 1730s to the 1860s.<ref name="books.google.com"/>

In Britain particularly, good quality building stone became ever more expensive during a period of rapid growth, and it became a common practice to construct prestige buildings from the new industrial bricks, and to finish them with a [[stucco]] to imitate stone. Hydraulic limes were favored for this, but the need for a fast set time encouraged the development of new cements. Most famous was Parker's "[[Roman cement]]".<ref>Francis, A.J. (1977) ''The Cement Industry 1796–1914: A History'', David & Charles. {{ISBN|0-7153-7386-2}}, Ch. 2.</ref> This was developed by [[James Parker (cement maker)|James Parker]] in the 1780s, and finally patented in 1796. It was, in fact, nothing like material used by the Romans, but was a "natural cement" made by burning [[Septarian concretion|septaria]] – [[Nodule (geology)|nodules]] that are found in certain clay deposits, and that contain both [[clay minerals]] and [[calcium carbonate]]. The burnt [[nodule (geology)|nodules]] were ground to a fine powder. This product, made into a mortar with sand, set in 5–15 minutes. The success of "Roman cement" led other manufacturers to develop rival products by burning artificial [[hydraulic lime]] cements of [[clay]] and [[chalk]].
Roman cement quickly became popular but was largely replaced by [[Portland cement]] in the 1850s.<ref name="Blezard"/>

===19th century===
Apparently unaware of [[John Smeaton|Smeaton's]] work, the same principle was identified by Frenchman [[Louis Vicat]] in the first decade of the nineteenth century. Vicat went on to devise a method of combining chalk and clay into an intimate mixture, and, burning this, produced an "artificial cement" in 1817<ref>{{cite web|url=http://www.nationalcement.com/faq/who-discovered-cement|title=Who Discovered Cement|url-status=live|archive-url=https://web.archive.org/web/20130204131106/http://www.nationalcement.com/faq/who-discovered-cement|archive-date=4 February 2013|df=dmy-all|date=12 September 2012}}</ref> considered the "principal forerunner"<ref name="Blezard"/> of Portland cement and "...Edgar Dobbs of [[Southwark]] patented a cement of this kind in 1811."<ref name="Blezard"/>

In Russia, [[Egor Cheliev]] created a new binder by mixing lime and clay. His results were published in 1822 in his book ''A Treatise on the Art to Prepare a Good Mortar'' published in [[Saint Petersburg|St. Petersburg]]. A few years later in 1825, he published another book, which described various methods of making cement and concrete, and the benefits of cement in the construction of buildings and embankments.<ref>{{cite book|author1=Znachko-Iavorskii|author2=I. L.|title=Egor Gerasimovich Chelidze, izobretatelʹ tsementa|url=http://catalog.hathitrust.org/Record/008851841|url-status=live|archive-url=https://web.archive.org/web/20140201232847/http://catalog.hathitrust.org/Record/008851841|archive-date=1 February 2014|publisher=Sabchota Sakartvelo|year=1969}}</ref><ref>{{cite web|title=Lafarge History of Cement|url=http://cement-174.ru/stati/izobretenie.html|url-status=live|archive-url=https://web.archive.org/web/20140202101113/http://cement-174.ru/stati/izobretenie.html|archive-date=2 February 2014}}</ref>

[[File:William Aspdin Radford cyclopedia Volume 1.jpg|thumb|right|upright|[[William Aspdin]] is considered the inventor of "modern" [[Portland cement]].<ref name="William Aspdin">{{cite book|last1=Courland|first1=Robert|title=Concrete planet : the strange and fascinating story of the world's most common man-made material|date=2011|publisher=Prometheus Books|location=Amherst, N.Y.|isbn=978-1616144814|url=https://archive.org/details/isbn_9781616144814|url-access=registration|page=[https://archive.org/details/isbn_9781616144814/page/190 190]}}</ref>]]
[[Portland cement]], the most common type of cement in general use around the world as a basic ingredient of concrete, [[mortar (masonry)|mortar]], [[stucco]], and non-speciality [[grout]], was developed in England in the mid 19th century, and usually originates from [[limestone]]. [[James Frost (cement maker)|James Frost]] produced what he called "British cement" in a similar manner around the same time, but did not obtain a patent until 1822.<ref>Francis, A.J. (1977) ''The Cement Industry 1796–1914: A History'', David & Charles. {{ISBN|0-7153-7386-2}}, Ch. 5.</ref> In 1824, [[Joseph Aspdin]] patented a similar material, which he called ''Portland cement'', because the render made from it was in color similar to the prestigious [[Portland stone]] quarried on the [[Isle of Portland]], Dorset, England. However, Aspdins' cement was nothing like modern Portland cement but was a first step in its development, called a ''proto-Portland cement''.<ref name="Blezard"/> Joseph Aspdins' son [[William Aspdin]] had left his father's company and in his cement manufacturing apparently accidentally produced [[calcium silicate]]s in the 1840s, a middle step in the development of Portland cement. William Aspdin's innovation was counterintuitive for manufacturers of "artificial cements", because they required more lime in the mix (a problem for his father), a much higher kiln temperature (and therefore more fuel), and the resulting clinker was very hard and rapidly wore down the [[millstone]]s, which were the only available [[Grinding wheel|grinding technology]] of the time. Manufacturing costs were therefore considerably higher, but the product set reasonably slowly and developed strength quickly, thus opening up a market for use in concrete. The use of concrete in construction grew rapidly from 1850 onward, and was soon the dominant use for cements. Thus Portland cement began its predominant role. [[Isaac Charles Johnson]] further refined the production of ''meso-Portland cement'' (middle stage of development) and claimed he was the real father of Portland cement.<ref>Hahn, Thomas F. and Kemp, Emory Leland (1994). ''Cement mills along the Potomac River''. Morgantown, WV: West Virginia University Press. p. 16. {{ISBN|9781885907004}}</ref>

Setting time and "early strength" are important characteristics of cements. Hydraulic limes, "natural" cements, and "artificial" cements all rely on their [[belite]] (2 CaO · SiO<sub>2</sub>, abbreviated as C<sub>2</sub>S) content for [[Strength of materials|strength]] development. Belite develops strength slowly. Because they were burned at temperatures below {{convert|1250|C|F}}, they contained no [[alite]] (3 CaO · SiO<sub>2</sub>, abbreviated as C<sub>3</sub>S), which is responsible for early strength in modern cements. The first cement to consistently contain alite was made by William Aspdin in the early 1840s: This was what we call today "modern" Portland cement. Because of the air of mystery with which William Aspdin surrounded his product, others (''e.g.,'' Vicat and Johnson) have claimed precedence in this invention, but recent analysis<ref>{{cite book|author=Hewlett, Peter|title=Lea's Chemistry of Cement and Concrete|url={{google books|plainurl=y|id=v1JVu4iifnMC|page=1}}|year=2003|publisher=Butterworth-Heinemann|isbn=978-0-08-053541-8|page=Ch. 1|url-status=live|archive-url=https://web.archive.org/web/20151101041700/https://books.google.com/books?id=v1JVu4iifnMC|archive-date=1 November 2015}}</ref> of both his concrete and raw cement have shown that William Aspdin's product made at [[Northfleet]], Kent was a true alite-based cement. However, Aspdin's methods were "rule-of-thumb": Vicat is responsible for establishing the chemical basis of these cements, and Johnson established the importance of [[sintering]] the mix in the [[Cement kiln|kiln]].

In the US the first large-scale use of cement was [[Rosendale cement]], a natural cement mined from a massive deposit of [[Dolomite (rock)|dolomite]] discovered in the early 19th century near [[Rosendale, New York]]. Rosendale cement was extremely popular for the foundation of buildings (''e.g.'', [[Statue of Liberty]], [[United States Capitol|Capitol Building]], [[Brooklyn Bridge]]) and lining water pipes.<ref name="Natural Cement Comes Back">{{Cite web|url={{google books|plainurl=y|id=VCcDAAAAMBAJ|page=118}}|title=Natural Cement Comes Back|work=Popular Science|date=October 1941|page=118|publisher=Bonnier Corporation|language=en}}</ref>
[[Sorel cement]], or magnesia-based cement, was patented in 1867 by the Frenchman [[Stanislas Sorel]].<ref name=sorel_1867>Stanislas Sorel (1867). "[https://archive.org/details/ComptesRendusAcademieDesSciences0065/page/n103 Sur un nouveau ciment magnésien]". ''Comptes rendus hebdomadaires des séances de l'Académie des sciences'', volume 65, pages 102–104.</ref> It was stronger than Portland cement but its poor water resistance (leaching) and corrosive properties ([[pitting corrosion]] due to the presence of leachable [[chloride]] anions and the low pH (8.5–9.5) of its pore water) limited its use as reinforced concrete for building construction.<ref name="WallingProvis2016">{{cite journal|last1=Walling|first1=Sam A.|last2=Provis|first2=John L.|title=Magnesia-based cements: A journey of 150 years, and cements for the future?|journal=Chemical Reviews|volume=116|issue=7|year=2016|pages=4170–4204|issn=0009-2665|doi=10.1021/acs.chemrev.5b00463|pmid=27002788|doi-access=free}}</ref>

The next development in the manufacture of Portland cement was the introduction of the [[rotary kiln]]. It produced a [[clinker (cement)|clinker]] mixture that was both stronger, because more [[alite]] (C<sub>3</sub>S) is formed at the higher temperature it achieved (1450&nbsp;°C), and more homogeneous. Because raw material is constantly fed into a rotary kiln, it allowed a [[continuous production|continuous manufacturing process]] to replace lower capacity [[batch production]] processes.<ref name="Blezard"/>

===20th century===
[[File:Factory of National Cement Share Company.jpg|thumb|right|The National Cement Share Company of [[Ethiopia]]'s new plant in [[Dire Dawa]]]]
[[Calcium aluminate cements]] were patented in 1908 in France by Jules Bied for better resistance to sulfates.<ref>{{Cite book|url={{google books|plainurl=y|id=NAqkAgAAQBAJ|page=211}}|title=Engineering Materials Science: Properties, Uses, Degradation, Remediation|last1=McArthur|first1=H.|last2=Spalding|first2=D.|date=1 January 2004|publisher=Elsevier|isbn=9781782420491}}</ref> Also in 1908, Thomas Edison experimented with pre-cast concrete in houses in Union, N.J.<ref>{{Cite web|url=https://science.howstuffworks.com/transport/engines-equipment/cement-mixer.htm|title=How Cement Mixers Work|date=26 January 2012|website=HowStuffWorks|language=en|access-date=2 April 2020}}</ref>

In the US, after World War One, the long [[curing time]] of at least a month for [[Rosendale cement]] made it unpopular for constructing highways and bridges, and many states and construction firms turned to Portland cement. Because of the switch to Portland cement, by the end of the 1920s only one of the 15 Rosendale cement companies had survived. But in the early 1930s, builders discovered that, while Portland cement set faster, it was not as durable, especially for highways—to the point that some states stopped building highways and roads with cement. Bertrain H. Wait, an engineer whose company had helped construct the New York City's [[Catskill Aqueduct]], was impressed with the durability of Rosendale cement, and came up with a blend of both Rosendale and Portland cements that had the good attributes of both. It was highly durable and had a much faster setting time. Wait convinced the New York Commissioner of Highways to construct an experimental section of highway near [[New Paltz, New York]], using one sack of Rosendale to six sacks of Portland cement. It was a success, and for decades the Rosendale-Portland cement blend was used in concrete highway and concrete bridge construction.<ref name="Natural Cement Comes Back"/>

Cementitious materials have been used as a nuclear waste immobilizing matrix for more than a half-century.<ref>Glasser F. (2011). Application of inorganic cements to the conditioning and immobilisation of radioactive wastes. In: Ojovan M.I. (2011). Handbook of advanced radioactive waste conditioning technologies. Woodhead, Cambridge, 512 pp.</ref> Technologies of waste cementation have been developed and deployed at industrial scale in many countries. Cementitious wasteforms require a careful selection and design process adapted to each specific type of waste to satisfy the strict waste acceptance criteria for long-term storage and disposal.<ref>Abdel Rahman R.O., Rahimov R.Z., Rahimova N.R., Ojovan M.I. (2015). Cementitious materials for nuclear waste immobilization. Wiley, Chichester 232 pp.</ref>

==Types==
{{Components of Cement, Comparison of Chemical and Physical Characteristics}}

Modern development of hydraulic cement began with the start of the [[Industrial Revolution]] (around 1800), driven by three main needs:
* Hydraulic [[cement render]] ([[stucco]]) for finishing brick buildings in wet climates
* Hydraulic mortars for masonry construction of harbor works, etc., in contact with sea water
* Development of strong concretes

Modern cements are often [[Portland cement]] or Portland cement blends, but other cement blends are used in some industrial settings.

=== Portland cement ===
{{Main|Portland cement}}
Portland cement, a form of hydraulic cement, is by far the most common type of cement in general use around the world. This cement is made by heating [[limestone]] (calcium carbonate) with other materials (such as [[clay]]) to {{convert|1450|C}} in a [[kiln]], in a process known as [[calcination]] that liberates a molecule of [[carbon dioxide]] from the calcium carbonate to form [[calcium oxide]], or quicklime, which then chemically combines with the other materials in the mix to form calcium silicates and other cementitious compounds. The resulting hard substance, called 'clinker', is then ground with a small amount of [[gypsum]] ({{chem2|CaSO4*2H2O}}) into a powder to make ''ordinary Portland cement'', the most commonly used type of cement (often referred to as OPC).
Portland cement is a basic ingredient of [[concrete]], [[mortar (masonry)|mortar]], and most non-specialty [[grout]]. The most common use for Portland cement is to make concrete. Portland cement may be grey or [[White Portland cement|white]].

===Portland cement blend===
<!--Clinker (cement) links here--->
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>

===Other ===

'''Pozzolan-lime''' cements are mixtures of ground [[pozzolanic ash|pozzolan]] and [[Agricultural lime|lime]]. These are the cements the Romans used, and are present in surviving Roman structures like the [[Pantheon, Rome|Pantheon]] in Rome. They develop strength slowly, but their ultimate strength can be very high. The hydration products that produce strength are essentially the same as those in Portland cement.

'''Slag-lime''' cements—[[ground granulated blast-furnace slag]]—are not hydraulic on their own, but are "activated" by addition of alkalis, most economically using lime. They are similar to pozzolan lime cements in their properties. Only granulated slag (i.e., water-quenched, glassy slag) is effective as a cement component.

'''Supersulfated''' cements contain about 80% ground granulated blast furnace slag, 15% [[gypsum]] or [[anhydrite]] and a little Portland clinker or lime as an activator. They produce strength by formation of [[ettringite]], with strength growth similar to a slow Portland cement. They exhibit good resistance to aggressive agents, including sulfate. 

[[Calcium aluminate cements|'''Calcium aluminate''' cements]] are hydraulic cements made primarily from [[limestone]] and [[bauxite]]. The active ingredients are monocalcium aluminate CaAl<sub>2</sub>O<sub>4</sub> (CaO · Al<sub>2</sub>O<sub>3</sub> or CA in [[cement chemist notation]], CCN) and [[mayenite]] Ca<sub>12</sub>Al<sub>14</sub>O<sub>33</sub> (12 CaO · 7 Al<sub>2</sub>O<sub>3</sub>, or C<sub>12</sub>A<sub>7</sub> in CCN). Strength forms by hydration to calcium aluminate hydrates. They are well-adapted for use in refractory (high-temperature resistant) concretes, e.g., for furnace linings.

'''Calcium sulfoaluminate''' cements are made from clinkers that include [[ye'elimite]] (Ca<sub>4</sub>(AlO<sub>2</sub>)<sub>6</sub>SO<sub>4</sub> or C<sub>4</sub>A<sub>3</sub>{{overline|S}} in [[Cement chemist notation|Cement chemist's notation]]) as a primary phase. They are used in expansive cements, in ultra-high early strength cements, and in "low-energy" cements. Hydration produces ettringite, and specialized physical properties (such as expansion or rapid reaction) are obtained by adjustment of the availability of calcium and sulfate ions. Their use as a low-energy alternative to Portland cement has been pioneered in China, where several million tonnes per year are produced.<ref>Bye, G.C. (1999). ''Portland Cement''. 2nd Ed., Thomas Telford. pp. 206–208. {{ISBN|0-7277-2766-4}}</ref><ref>{{cite journal|doi=10.1680/adcr.1999.11.1.15|title=Development of the use of sulfo- and ferroaluminate cements in China|journal=Advances in Cement Research|volume=11|pages=15–21|year=1999|last1=Zhang|first1=Liang|last2=Su|first2=Muzhen|last3=Wang|first3=Yanmou}}</ref> Energy requirements are lower because of the lower kiln temperatures required for reaction, and the lower amount of limestone (which must be endothermically decarbonated) in the mix. In addition, the lower limestone content and lower fuel consumption leads to a {{chem|CO|2}} emission around half that associated with Portland clinker. However, SO<sub>2</sub> emissions are usually significantly higher.

'''"Natural"''' cements corresponding to certain cements of the pre-Portland era, are produced by burning [[argillaceous minerals|argillaceous limestones]] at moderate temperatures. The level of clay components in the limestone (around 30–35%) is such that large amounts of [[belite]] (the low-early strength, high-late strength mineral in Portland cement) are formed without the formation of excessive amounts of free lime. As with any natural material, such cements have highly variable properties.

'''[[Geopolymer]]''' cements are made from mixtures of water-soluble alkali metal silicates, and aluminosilicate mineral powders such as [[fly ash]] and [[metakaolin]].

'''Polymer''' cements are made from organic chemicals that polymerise. Producers often use [[thermoset]] materials. While they are often significantly more expensive, they can give a water proof material that has useful tensile strength.

[[Sorel cement|'''Sorel''' cement]] is a hard, durable cement made by combining magnesium oxide and a magnesium chloride solution

'''Fiber mesh''' cement or [[Fiber-reinforced concrete|fiber reinforced concrete]] is cement that is made up of fibrous materials like synthetic fibers, glass fibers, natural fibers, and steel fibers. This type of mesh is distributed evenly throughout the wet concrete. The purpose of fiber mesh is to reduce water loss from the concrete as well as enhance its structural integrity.<ref name="Port Aggregates 2019-12-31">{{Cite web|title=Concrete mesh: When to use fiber mesh or wire mesh {{!}} Port Aggregates|last=Munsell|first=Faith|work=Port Aggregates|date=31 December 2019|access-date=19 September 2022|url=https://www.portaggregates.com/when-to-use-fiber-or-wire-concrete-mesh/}}</ref> When used in plasters, fiber mesh increases cohesiveness, tensile strength, impact resistance, and to reduce shrinkage; ultimately, the main purpose of these combined properties is to reduce cracking.<ref name="Cement.org 2003">{{cite news|url=https://www.cement.org/docs/default-source/stucco/eb049.pdf?sfvrsn=540de3bf_2|format=PDF|title=Plaster / Stucco Manual|work=Cement.org|date=2003|page=13|access-date=12 April 2021}}</ref>

'''Electric''' cement is proposed to be made by recycling cement from demolition wastes in an [[electric arc furnace]] as part of a [[steelmaking]] process. The recycled cement is intended to be used to replace part or all of the [[Lime (material)|lime]] used in steelmaking, resulting in a slag-like material that is similar in mineralogy to Portland cement, eliminating most of the associated carbon emissions.<ref>{{Cite web|last=Barnard|first=Michael|date=30 May 2024|title=Many Green Cement Roads Lead Through Electric Arc Steel Furnaces|url=https://cleantechnica.com/2024/05/30/many-green-cement-roads-lead-through-electric-arc-steel-furnaces/|access-date=11 June 2024|website=CleanTechnica|language=en-US}}</ref>

==Setting, hardening and curing==
Cement starts to set when mixed with water, which causes a series of hydration chemical reactions. The constituents slowly hydrate and the mineral hydrates solidify and harden. The interlocking of the hydrates gives cement its strength. Contrary to popular belief, hydraulic cement does not set by drying out — proper curing requires maintaining the appropriate moisture content necessary for the hydration reactions during the setting and the hardening processes. If hydraulic cements dry out during the curing phase, the resulting product can be insufficiently hydrated and significantly weakened. A minimum temperature of 5&nbsp;°C is recommended, and no more than 30&nbsp;°C.<ref>{{Cite web|url=https://www.sovchem.co.uk/profile/news/read/id/206/|title=Using cement based products during winter months|date=29 May 2018|website=sovchem.co.uk|archive-url=https://web.archive.org/web/20180529203647/https://www.sovchem.co.uk/profile/news/read/id/206/|archive-date=29 May 2018|url-status=dead}}</ref> The concrete at young age must be protected against water evaporation due to direct insolation, elevated temperature, low [[relative humidity]] and wind.

The ''interfacial transition zone'' (ITZ) is a region of the cement paste around the [[Aggregate (composite)|aggregate]] particles in [[concrete]]. In the zone, a gradual transition in the [[Microstructure|microstructural]] features occurs.<ref name="scr01" /> This zone can be up to 35 micrometer wide.{{r|ty01|p=351}} Other studies have shown that the width can be up to 50 micrometer. The average content of unreacted clinker phase decreases and [[porosity]] decreases towards the aggregate surface. Similarly, the content of [[ettringite]] increases in ITZ. {{r|ty01|p=352}}

==Safety issues==
Bags of cement routinely have health and safety warnings printed on them because not only is cement highly [[alkali]]ne, but the [[setting process]] is [[exothermic]]. As a result, wet cement is strongly [[causticity|caustic]] (pH = 13.5) and can easily cause severe [[skin burn]]s if not promptly washed off with water. Similarly, dry cement powder in contact with [[mucous membrane]]s can cause severe eye or respiratory irritation. Some trace elements, such as chromium, from impurities naturally present in the raw materials used to produce cement may cause [[Allergic contact dermatitis|allergic dermatitis]].<ref name="hse.gov.uk">{{cite web|url=http://www.hse.gov.uk/pubns/cis26.pdf|title=Construction Information Sheet No 26 (revision2)|access-date=15 February 2011|url-status=live|archive-url=https://web.archive.org/web/20110604222509/http://www.hse.gov.uk/pubns/cis26.pdf|publisher=hse.gov.uk|archive-date=4 June 2011}}</ref> Reducing agents such as ferrous sulfate (FeSO<sub>4</sub>) are often added to cement to convert the carcinogenic hexavalent [[Chromate ion|chromate]] (CrO<sub>4</sub><sup>2−</sup>) into trivalent chromium (Cr<sup>3+</sup>), a less toxic chemical species. Cement users need also to wear appropriate gloves and protective clothing.<ref>{{cite web|url=http://www.hse.gov.uk/pubns/cis26.pdf|title=CIS26 – cement|archive-url=https://web.archive.org/web/20110604222509/http://www.hse.gov.uk/pubns/cis26.pdf|archive-date=4 June 2011|access-date=5 May 2011}}</ref>

==Cement industry in the world==

[[File:Cement Production 2022.png|thumb|right|alt=Global cement production (2022)|Global cement production in 2022]]
[[File:Clinker Capacity 2022.png|thumb|right|alt=Global cement capacity (2022)|Global cement capacity in 2022]]

{{See also|List of countries by cement production|Cement industry in the United States}}
In 2010, the world production of hydraulic cement was [[Orders of magnitude (mass)#1012 to 1017 kg|{{convert|3300|Mt|e6ST}}]]. The top three producers were [[Cement industry in China|China]] with 1,800, India with 220, and the [[Cement industry in the United States|United States]] with 63.5 million tonnes for a total of over half the world total by the world's three most populated states.<ref>{{cite web|author=United States Geological Survey|title=USGS Mineral Program Cement Report. (Jan 2011)|url=http://minerals.usgs.gov/minerals/pubs/commodity/cement/mcs-2011-cemen.pdf|url-status=live|archive-url=https://web.archive.org/web/20111008062123/http://minerals.usgs.gov/minerals/pubs/commodity/cement/mcs-2011-cemen.pdf|archive-date=8 October 2011|df=dmy-all}}</ref>

For the world capacity to produce cement in 2010, the situation was similar with the top three states (China, India, and the US) accounting for just under half the world total capacity.<ref>Edwards, P; McCaffrey, R. Global Cement Directory 2010. [http://www.globalcement.com/ PRo Publications] {{webarchive|url=https://web.archive.org/web/20140103095700/http://globalcement.com/ |date=3 January 2014 }}. Epsom, UK, 2010.</ref>

Over 2011 and 2012, global consumption continued to climb, rising to 3585 Mt in 2011 and 3736 Mt in 2012, while annual [[Economic growth|growth rates]] eased to 8.3% and 4.2%, respectively.

China, representing an increasing share of world cement consumption, remains the main engine of global growth. By 2012, Chinese demand was recorded at 2160 Mt, representing 58% of world consumption. Annual growth rates, which reached 16% in 2010, appear to have softened, slowing to 5–6% over 2011 and 2012, as China's economy targets a more [[sustainable growth]] rate.

Outside of China, worldwide consumption climbed by 4.4% to 1462 Mt in 2010, 5% to 1535 Mt in 2011, and finally 2.7% to 1576 Mt in 2012.

Iran is now the 3rd largest cement producer in the world and has increased its output by over 10% from 2008 to 2011.<ref>{{Cite web|date=2012-08-20|title=Pakistan loses Afghan cement market share to Iran|url=https://www.cemnet.com/News/story/150426/pakistan-loses-afghan-cement-market-share-to-iran.html|access-date=2 November 2024|website=International Cement Revie|archive-url=https://web.archive.org/web/20130922070531/http://cemnet.com/News/story/150426/pakistan-loses-afghan-cement-market-share-to-iran.html|archive-date=22 September 2013}}</ref> Because of climbing energy costs in Pakistan and other major cement-producing countries, Iran is in a unique position as a trading partner, utilizing its own surplus petroleum to power clinker plants. Now a top producer in the Middle-East, Iran is further increasing its dominant position in local markets and abroad.<ref>ICR Newsroom. [http://www.cemnet.com/News/story/150426/pakistan-loses-afghan-cement-market-share-to-iran.html Pakistan loses Afghan cement market share to Iran] {{webarchive|url=https://web.archive.org/web/20130922070531/http://cemnet.com/News/story/150426/pakistan-loses-afghan-cement-market-share-to-iran.html |date=22 September 2013 }}. Retrieved 19 November 2013.</ref>

The performance in North America and Europe over the 2010–12 period contrasted strikingly with that of China, as the global financial crisis evolved into a sovereign debt crisis for many economies in this region{{clarify|date=September 2020|reason=Which region?}} and recession. Cement consumption levels for this region fell by 1.9% in 2010 to 445 Mt, recovered by 4.9% in 2011, then dipped again by 1.1% in 2012.

The performance in the rest of the world, which includes many emerging economies in Asia, Africa and Latin America and representing some 1020 Mt cement demand in 2010, was positive and more than offset the declines in North America and Europe. Annual consumption growth was recorded at 7.4% in 2010, moderating to 5.1% and 4.3% in 2011 and 2012, respectively.

As at year-end 2012, the global cement industry consisted of 5673 cement production facilities, including both integrated and grinding, of which 3900 were located in China and 1773 in the rest of the world.

Total cement capacity worldwide was recorded at 5245 Mt in 2012, with 2950 Mt located in China and 2295 Mt in the rest of the world.<ref name=Hargreaves>{{cite journal|author=Hargreaves, David|journal=International Cement Review|title=The Global Cement Report 10th Edition|date=March 2013|url=http://www.cemnet.com/content/publications/GCR10Worldoverview.pdf|url-status=live|archive-url=https://web.archive.org/web/20131126060704/http://www.cemnet.com/content/publications/GCR10Worldoverview.pdf|archive-date=26 November 2013|df=dmy-all}}</ref>

===China===
{{main|Cement industry in China}}
"For the past 18 years, China consistently has produced more cement than any other country in the world. [...] (However,) China's cement export peaked in 1994 with 11 million tonnes shipped out and has been in steady decline ever since. Only 5.18 million tonnes were exported out of China in 2002. Offered at $34 a ton, Chinese cement is pricing itself out of the market as Thailand is asking as little as $20 for the same quality."<ref>Yan, Li Yong (7 January 2004) [https://web.archive.org/web/20040108214033/http://www.atimes.com/atimes/China/FA07Ad02.html China's way forward paved in cement], ''Asia Times''</ref>

In 2006, it was estimated that China manufactured 1.235 billion tonnes of cement, which was 44% of the world total cement production.<ref name="NEAA070619b">{{cite web|url=http://www.mnp.nl/en/dossiers/Climatechange/moreinfo/Chinanowno1inCO2emissionsUSAinsecondposition.html|title=China now no. 1 in {{chem|CO|}} emissions; USA in second position: more info|archive-url=https://web.archive.org/web/20070703030047/http://www.mnp.nl/en/dossiers/Climatechange/moreinfo/Chinanowno1inCO2emissionsUSAinsecondposition.html|archive-date=3 July 2007|publisher=[[Netherlands Environmental Assessment Agency|NEAA]]|date=19 June 2007}}</ref> "Demand for cement in China is expected to advance 5.4% annually and exceed 1 billion tonnes in 2008, driven by slowing but healthy growth in construction expenditures. Cement consumed in China will amount to 44% of global demand, and China will remain the world's largest national consumer of cement by a large margin."<ref>{{cite news|archive-url=https://web.archive.org/web/20090427075804/http://cementamericas.com/mag/cement_chinas_cement_demand/|url=http://cementamericas.com/mag/cement_chinas_cement_demand/|title=China's cement demand to top 1 billion tonnes in 2008|work=CementAmericas|date=November 2004|archive-date=27 April 2009 }}</ref>

In 2010, 3.3 billion tonnes of cement was consumed globally. Of this, China accounted for 1.8 billion tonnes.<ref name=worldcoal>{{cite web|url=http://www.worldcoal.org/coal/uses-of-coal/coal-cement/|title=Uses of Coal and Cement|publisher=World Coal Association|archive-url=https://web.archive.org/web/20110808003702/http://www.worldcoal.org/coal/uses-of-coal/coal-cement/|archive-date=8 August 2011}}</ref>

=={{anchor|Environmental and social impacts}}Environmental impacts==
{{Further|Environmental impact of concrete}}
Cement manufacture causes environmental impacts at all stages of the process. These include emissions of airborne pollution in the form of dust, gases, noise and vibration when operating machinery and during blasting in [[quarry|quarries]], and damage to countryside from quarrying. Equipment to reduce dust emissions during quarrying and manufacture of cement is widely used, and equipment to trap and separate exhaust gases are coming into increased use. Environmental protection also includes the re-integration of quarries into the countryside after they have been closed down by returning them to nature or re-cultivating them.

==={{chem|CO|2}} emissions===
[[File:Co2-emissions-by-fuel-line1800-2018.svg|right|400px|Global carbon emission by type to 2018]]
Carbon concentration in cement spans from ≈5% in cement structures to ≈8% in the case of roads in cement.<ref>{{cite journal|title=Influence of 150 years of land use on anthropogenic and natural carbon stocks in Emilia-Romagna Region (Italy)|author1=Scalenghe, R.|author2=Malucelli, F.|author3=Ungaro, F.|author4=Perazzone, L.|author5=Filippi, N.|author6=Edwards, A.C.|year=2011|volume=45|issue=12|pages=5112–5117|doi=10.1021/es1039437|pmid=21609007|journal=Environmental Science & Technology|bibcode=2011EnST...45.5112S}}</ref> Cement manufacturing releases {{CO2|link=yes}} in the atmosphere both directly when [[calcium carbonate]] is heated, producing [[lime (mineral)|lime]] and [[carbon dioxide]],<ref>{{cite web|url=http://www.eia.doe.gov/oiaf/1605/ggrpt/carbon.html|title=EIA – Emissions of Greenhouse Gases in the U.S. 2006-Carbon Dioxide Emissions|archive-url=https://web.archive.org/web/20110523061426/http://www.eia.doe.gov/oiaf/1605/ggrpt/carbon.html|archive-date=23 May 2011|publisher=US Department of Energy}}</ref><ref>{{cite journal|title=Striking a balance between profit and carbon dioxide emissions in the Saudi cement industry|author1=Matar, W.|author2=Elshurafa, A. M.|year=2017|volume=61|pages=111–123|doi=10.1016/j.ijggc.2017.03.031|journal=International Journal of Greenhouse Gas Control|bibcode=2017IJGGC..61..111M|doi-access=free}}</ref> and also indirectly through the use of energy if its production involves the emission of {{chem|CO|2}}. The cement industry produces about 10% of global [[Anthropogenic greenhouse gas|human-made {{chem|CO|2}} emissions]], of which 60% is from the chemical process, and 40% from burning fuel.<ref>{{cite web|url=http://www.pbl.nl/sites/default/files/cms/publicaties/PBL_2014_Trends_in_global_CO2_emisions_2014_1490_0.pdf|title=Trends in global {{chem|CO|2}} emissions: 2014 Report|archive-url=https://web.archive.org/web/20161014143722/http://www.pbl.nl/sites/default/files/cms/publicaties/PBL_2014_Trends_in_global_CO2_emisions_2014_1490_0.pdf|archive-date=14 October 2016|publisher=PBL Netherlands Environmental Assessment Agency & European Commission Joint Research Centre|year=2014}}</ref> A [[Chatham House]] study from 2018 estimates that the 4 billion tonnes of cement produced annually account for 8% of worldwide {{chem|CO|2}} emissions.<ref name=chathamhouse>{{Cite web|url=https://reader.chathamhouse.org/making-concrete-change-innovation-low-carbon-cement-and-concrete|title=Making Concrete Change: Innovation in Low-carbon Cement and Concrete|website=Chatham House|date=13 June 2018|access-date=17 December 2018|archive-url=https://web.archive.org/web/20181219161129/https://reader.chathamhouse.org/making-concrete-change-innovation-low-carbon-cement-and-concrete|archive-date=19 December 2018|url-status=live}}</ref>

Nearly 900&nbsp;kg of {{chem|CO|2}} are emitted for every 1000&nbsp;kg of Portland cement produced. In the European Union, the specific energy consumption for the production of cement clinker has been reduced by approximately 30% since the 1970s. This reduction in primary energy requirements is equivalent to approximately 11 million tonnes of coal per year with corresponding benefits in reduction of {{chem|CO|2}} emissions. This accounts for approximately 5% of anthropogenic {{chem|CO|2}}.<ref>
{{Cite book|last=Mahasenan|first=Natesan|author2=Smith, Steve|author3=Humphreysm Kenneth|author4=Kaya, Y.|title=Greenhouse Gas Control Technologies – 6th International Conference|chapter=The Cement Industry and Global Climate Change: Current and Potential Future Cement Industry {{chem|CO|2}} Emissions|publisher=Pergamon|isbn=978-0-08-044276-1|pages=995–1000|location=Oxford|year=2003|chapter-url=http://www.sciencedirect.com/science/article/B873D-4P9MYFN-BK/2/c58323fdf4cbc244856fe80c96447f44}}
</ref>

The majority of carbon dioxide emissions in the manufacture of Portland cement (approximately 60%) are produced from the chemical decomposition of limestone to lime, an ingredient in Portland cement clinker. These emissions may be reduced by lowering the clinker content of cement. They can also be reduced by alternative fabrication methods such as the intergrinding cement with sand or with slag or other pozzolan type minerals to a very fine powder.<ref name="Science Direct 2015">{{cite web|url=https://www.sciencedirect.com/topics/engineering/blended-cement|title=Blended Cement|work=Science Direct|date=2015|access-date=7 April 2021}}</ref>

To reduce the transport of heavier raw materials and to minimize the associated costs, it is more economical to build cement plants closer to the limestone quarries rather than to the consumer centers.<ref>{{cite web|last=Chandak|first=Shobhit|title=Report on cement industry in India|url=https://www.scribd.com/doc/13378451/Cement-Industry-In-India|publisher=scribd|access-date=21 July 2011|url-status=live|archive-url=https://web.archive.org/web/20120222124243/http://www.scribd.com/doc/13378451/Cement-Industry-In-India|archive-date=22 February 2012}}</ref>

{{As of|2019}} [[carbon capture and storage]] is about to be trialed, but its financial viability is uncertain.<ref>{{cite news|title=World's first zero-emission cement plant takes shape in Norway|url=https://www.euractiv.com/section/energy/news/worlds-first-zero-emission-cement-plant-takes-shape-in-norway/|publisher=Euractiv.com Ltd.|date=13 December 2018}}</ref>

==={{chem|CO|2}} absorption===
Hydrated products of Portland cement, such as concrete and mortars, slowly reabsorb atmospheric CO2 gas, which has been released during calcination in a kiln. This natural process, reversed to calcination, is called carbonation.<ref name="pade2007">{{cite journal|last1=Pade|first1=Claus|last2=Guimaraes|first2=Maria|date=1 September 2007|title=The CO2 uptake of concrete in a 100 year perspective|url=https://www.sciencedirect.com/science/article/pii/S0008884607001317|journal=Cement and Concrete Research|volume=37|issue=9|pages=1348–1356|doi=10.1016/j.cemconres.2007.06.009|issn=0008-8846}}</ref> As it depends on CO2 diffusion into the bulk of concrete, its rate depends on many parameters, such as environmental conditions and surface area exposed to the atmosphere.<ref>{{Cite journal|last1=Xi|first1=Fengming|last2=Davis|first2=Steven J.|last3=Ciais|first3=Philippe|last4=Crawford-Brown|first4=Douglas|last5=Guan|first5=Dabo|last6=Pade|first6=Claus|last7=Shi|first7=Tiemao|last8=Syddall|first8=Mark|last9=Lv|first9=Jie |last10=Ji |first10=Lanzhu|last11=Bing|first11=Longfei|last12=Wang|first12=Jiaoyue|last13=Wei|first13=Wei|last14=Yang|first14=Keun-Hyeok|last15=Lagerblad|first15=Björn|date=December 2016|title=Substantial global carbon uptake by cement carbonation|url=https://www.nature.com/articles/ngeo2840|journal=Nature Geoscience|language=en|volume=9|issue=12|pages=880–883|doi=10.1038/ngeo2840|bibcode=2016NatGe...9..880X|issn=1752-0908}}</ref><ref name="cao2020">{{Cite journal|last1=Cao|first1=Zhi|last2=Myers|first2=Rupert J.|last3=Lupton|first3=Richard C.|last4=Duan|first4=Huabo|last5=Sacchi|first5=Romain|last6=Zhou|first6=Nan|last7=Reed Miller|first7=T.|last8=Cullen|first8=Jonathan M.|last9=Ge|first9=Quansheng |last10=Liu |first10=Gang|date=29 July 2020|title=The sponge effect and carbon emission mitigation potentials of the global cement cycle|journal=Nature Communications|language=en|volume=11|issue=1|pages=3777|doi=10.1038/s41467-020-17583-w|pmid=32728073|bibcode=2020NatCo..11.3777C|issn=2041-1723|doi-access=free|pmc=7392754|hdl=10044/1/81385|hdl-access=free}}</ref> Carbonation is particularly significant at the latter stages of the concrete life - after demolition and crushing of the debris. It was estimated that during the whole life-cycle of cement products, it can be reabsorbed nearly 30% of atmospheric CO2 generated by cement production.<ref name="cao2020" />

Carbonation process is considered as a mechanism of concrete degradation. It reduces pH of concrete that promotes reinforcement steel corrosion.<ref name="pade2007" /> However, as the product of Ca(OH)2 carbonation, CaCO3, occupies a greater volume, porosity of concrete reduces. This increases strength and hardness of concrete.<ref>{{cite journal|last1=Kim|first1=Jin-Keun|last2=Kim|first2=Chin-Yong|last3=Yi|first3=Seong-Tae|last4=Lee|first4=Yun|date=1 February 2009|title=Effect of carbonation on the rebound number and compressive strength of concrete|url=https://www.sciencedirect.com/science/article/pii/S0958946508001236|journal=Cement and Concrete Composites|volume=31|issue=2|pages=139–144|doi=10.1016/j.cemconcomp.2008.10.001|issn=0958-9465}}</ref>

There are proposals to reduce carbon footprint of hydraulic cement by adopting non-hydraulic cement, [[lime mortar]], for certain applications. It reabsorbs some of the {{chem|CO|2}} during hardening, and has a lower energy requirement in production than Portland cement.<ref>{{Cite news|url=https://www.theguardian.com/commentisfree/2007/oct/23/comment.comment|title=Response: Lime is a much greener option than cement, says Douglas Kent|last=Kent|first=Douglas|date=22 October 2007|work=The Guardian|access-date=22 January 2020|language=en-GB|issn=0261-3077}}</ref>

A few other attempts to increase absorption of [[carbon dioxide]] include cements based on magnesium ([[Sorel cement]]).<ref>{{Cite web|date=9 March 2011|title=Novacem's 'carbon negative cement'|url=https://ceramics.org/ceramic-tech-today/novacems-carbon-negative-cement/|access-date=26 September 2023|website=The American Ceramic Society|language=en-US}}</ref><ref>{{cite web|url=http://www.imperialinnovations.co.uk/?q=node/176|title=Novacem|archive-url=https://web.archive.org/web/20090803053655/http://www.imperialinnovations.co.uk/?q=node%2F176|archive-date=3 August 2009|website=imperialinnovations.co.uk}}</ref><ref>{{cite news|url=https://www.theguardian.com/environment/2008/dec/31/cement-carbon-emissions|work=The Guardian|location=London|title=Revealed: The cement that eats carbon dioxide|first=Alok|last=Jha|date=31 December 2008|access-date=28 April 2010|url-status=live|archive-url=https://web.archive.org/web/20130806151853/http://www.theguardian.com/environment/2008/dec/31/cement-carbon-emissions|archive-date=6 August 2013|df=dmy-all}}</ref>

===Heavy metal emissions in the air===
In some circumstances, mainly depending on the origin and the composition of the raw materials used, the high-temperature calcination process of limestone and clay minerals can release in the atmosphere gases and dust rich in volatile [[heavy metal (chemistry)|heavy metals]], e.g. [[Thallium#Thallium pollution|thallium]],<ref>{{cite web|url=http://www.epa.gov/safewater/pdfs/factsheets/ioc/thallium.pdf|access-date=15 September 2009|title=Factsheet on: Thallium|url-status=live|archive-url=https://web.archive.org/web/20120111232626/http://www.epa.gov/safewater/pdfs/factsheets/ioc/thallium.pdf|archive-date=11 January 2012|df=dmy-all}}</ref> [[cadmium]] and [[mercury (element)|mercury]] are the most toxic. Heavy metals (Tl, Cd, Hg, ...) and also [[selenium]] are often found as trace elements in common metal [[sulfide]]s ([[pyrite]] (FeS<sub>2</sub>), [[Sphalerite|zinc blende (ZnS)]], [[galena]] (PbS), ...) present as secondary minerals in most of the raw materials. Environmental regulations exist in many countries to limit these emissions. As of 2011 in the United States, cement kilns are "legally allowed to pump more [[toxins]] into the air than are hazardous-waste incinerators."<ref>{{cite web|last=Berkes, Howard|title=EPA Regulations Give Kilns Permission To Pollute : NPR|work=NPR.org|access-date=17 November 2011|date=10 November 2011|url=https://www.npr.org/2011/11/10/142183546/epa-regulations-give-kilns-permission-to-pollute|url-status=live|archive-url=https://web.archive.org/web/20111117112612/http://www.npr.org/2011/11/10/142183546/epa-regulations-give-kilns-permission-to-pollute|archive-date=17 November 2011|df=dmy-all}}</ref>

===Heavy metals present in the clinker===
The presence of [[heavy metals]] in the clinker arises both from the natural raw materials and from the use of recycled by-products or [[alternative fuels]]. The high pH prevailing in the cement porewater (12.5 < pH < 13.5) limits the mobility of many heavy metals by decreasing their solubility and increasing their sorption onto the cement mineral phases. [[Nickel]], [[zinc]] and [[lead]] are commonly found in cement in non-negligible concentrations. [[Chromium]] may also directly arise as natural impurity from the raw materials or as secondary contamination from the abrasion of hard chromium steel alloys used in the ball mills when the clinker is ground. As [[Chromate ion|chromate]] (CrO<sub>4</sub><sup>2−</sup>) is toxic and may cause severe [[skin allergies]] at trace concentration, it is sometimes reduced into trivalent Cr(III) by addition of [[ferrous sulfate]] (FeSO<sub>4</sub>).

===Use of alternative fuels and by-products materials===
A cement plant consumes 3 to 6 [[Gigajoule|GJ]] of fuel per tonne of clinker produced, depending on the raw materials and the process used. Most cement kilns today use coal and petroleum coke as primary fuels, and to a lesser extent natural gas and fuel oil. Selected waste and by-products with recoverable [[calorific value]] can be used as fuels in a cement kiln (referred to as [[co-processing]]), replacing a portion of conventional [[fossil fuels]], like coal, if they meet strict specifications. Selected waste and by-products containing useful minerals such as calcium, silica, alumina, and iron can be used as raw materials in the kiln, replacing raw materials such as clay, [[shale]], and limestone. Because some materials have both useful mineral content and recoverable calorific value, the distinction between alternative fuels and raw materials is not always clear. For example, sewage sludge has a low but significant calorific value, and burns to give ash containing minerals useful in the clinker matrix.<ref>{{cite web|url=http://www.wbcsd.org/DocRoot/Vjft3qGjo1v6HREH7jM6/tf2-guidelines.pdf|title=Guidelines for the selection and use of fuels and raw materials in the cement manufacturing process|archive-url=https://web.archive.org/web/20080910015447/http://www.wbcsd.org/DocRoot/Vjft3qGjo1v6HREH7jM6/tf2-guidelines.pdf|archive-date=10 September 2008|publisher=World Business Council for Sustainable Development|date=1 June 2005}}</ref> Scrap automobile and truck tires are useful in cement manufacturing as they have high calorific value and the iron embedded in tires is useful as a feed stock.<ref>{{cite web|url=https://www.ifc.org/wps/wcm/connect/cb361035-1872-4566-a7e7-d3d1441ad3ac/Alternative_Fuels_08+04.pdf|title=Increasing the use of alternative fuels at cement plants: International best practice|publisher=International Finance Corporation, World Bank Group|date=2017}}</ref>{{rp|p. 27}}

Clinker is manufactured by heating raw materials inside the main burner of a kiln to a temperature of 1,450&nbsp;°C. The flame reaches temperatures of 1,800&nbsp;°C. The material remains at 1,200&nbsp;°C for 12–15 seconds at 1,800&nbsp;°C or sometimes for 5–8 seconds (also referred to as residence time). These characteristics of a clinker kiln offer numerous benefits and they ensure a complete destruction of organic compounds, a total neutralization of acid gases, sulphur oxides and hydrogen chloride. Furthermore, heavy metal traces are embedded in the clinker structure and no by-products, such as ash or residues, are produced.<ref>{{cite web|url=https://cembureau.eu/media/1229/9062_cembureau_cementconcretecirculareconomy_coprocessing_2016-09-01-04.pdf|title=Cement, concrete & the circular economy|archive-url=https://web.archive.org/web/20181112223510/https://cembureau.eu/media/1229/9062_cembureau_cementconcretecirculareconomy_coprocessing_2016-09-01-04.pdf|archive-date=12 November 2018|website=cembureau.eu}}</ref>

The EU cement industry already uses more than 40% fuels derived from waste and biomass in supplying the thermal energy to the grey clinker making process. Although the choice for this so-called alternative fuels (AF) is typically cost driven, other factors are becoming more important. Use of alternative fuels provides benefits for both society and the company: {{chem|CO|2}}-emissions are lower than with fossil fuels, waste can be co-processed in an efficient and sustainable manner and the demand for certain virgin materials can be reduced. Yet there are large differences in the share of alternative fuels used between the European Union (EU) member states. The societal benefits could be improved if more member states increase their alternative fuels share. The Ecofys study<ref>de Beer, Jeroen et al. (2017) [https://cembureau.eu/media/2lte1jte/11603-ecofys-executive-summary_cembureau-2017-04-26.pdf Status and prospects of co-processing of waste in EU cement plants] {{Webarchive|url=https://web.archive.org/web/20201230172551/http://www.cembureau.eu/media/2lte1jte/11603-ecofys-executive-summary_cembureau-2017-04-26.pdf |archive-url=https://web.archive.org/web/20200923223026/http://cembureau.eu/media/2lte1jte/11603-ecofys-executive-summary_cembureau-2017-04-26.pdf |archive-date=23 September 2020 |url-status=live |date=30 December 2020 }}. ECOFYS study.</ref> assessed the barriers and opportunities for further uptake of alternative fuels in 14 EU member states. The Ecofys study found that local factors constrain the market potential to a much larger extent than the technical and economic feasibility of the cement industry itself.

==Reduced-footprint cement==
Growing environmental concerns and the increasing cost of fossil fuels have resulted, in many countries, in a sharp reduction of the resources needed to produce cement, as well as effluents (dust and exhaust gases).<ref name="groundwork.org.za">{{Cite web|title=Alternative fuels in cement manufacture – CEMBUREAU brochure, 1997|url=http://www.groundwork.org.za/Cement/Alternative_Fuels_in_Cement_Manufacture_CEMBUREAU_Brochure_EN.pdf|url-status=dead|archive-url=https://web.archive.org/web/20131002040331/http://www.groundwork.org.za/Cement/Alternative_Fuels_in_Cement_Manufacture_CEMBUREAU_Brochure_EN.pdf|archive-date=2 October 2013}}</ref> Reduced-footprint cement is a cementitious material that meets or exceeds the functional performance capabilities of Portland cement. Various techniques are under development. One is [[geopolymer cement]], which incorporates recycled materials, thereby reducing consumption of raw materials, water, and energy. Another approach is to reduce or eliminate the production and release of damaging pollutants and greenhouse gasses, particularly {{chem|CO|2}}.<ref>{{cite web|title=Engineers develop cement with 97 percent smaller carbon dioxide and energy footprint – DrexelNow|url=http://drexel.edu/now/archive/2012/February/Engineers-Develop-Cement-With-97-Percent-Smaller-Carbon-Dioxide-and-Energy-Footprint/|website=DrexelNow|date=20 February 2012|access-date=16 January 2016|url-status=live|archive-url=https://web.archive.org/web/20151218144742/http://www.drexel.edu/now/archive/2012/February/Engineers-Develop-Cement-With-97-Percent-Smaller-Carbon-Dioxide-and-Energy-Footprint/|archive-date=18 December 2015}}</ref> Recycling old cement in [[electric arc furnace]]s is another approach.<ref>{{Cite news|title=How to make low-carbon concrete from old cement|url=https://www.economist.com/science-and-technology/2023/04/26/how-to-make-low-carbon-concrete-from-old-cement|access-date=27 April 2023|newspaper=The Economist|issn=0013-0613}}</ref> Also, a team at the [[University of Edinburgh]] has developed the 'DUPE' process based on the microbial activity of ''[[Sporosarcina pasteurii]]'', a bacterium precipitating calcium carbonate, which, when mixed with [[sand]] and [[urine]], can produce mortar blocks with a compressive strength 70% of that of concrete.<ref>{{cite web|author=Monks, Kieron|date=22 May 2014|title=Would you live in a house made of sand and bacteria? It's a surprisingly good idea|url=https://edition.cnn.com/2014/05/21/tech/innovation/would-you-live-in-a-house-made-of-urine-and-bacteria/index.html|url-status=live|archive-url=https://web.archive.org/web/20140720051919/http://edition.cnn.com/2014/05/21/tech/innovation/would-you-live-in-a-house-made-of-urine-and-bacteria/index.html|archive-date=20 July 2014|access-date=20 July 2014|publisher=CNN}}</ref> An overview of climate-friendly methods for cement production can be found here.<ref>{{Cite web|title=Top-Innovationen 2020: Zement lässt sich auch klimafreundlich produzieren|url=https://www.spektrum.de/news/gruene-produktion-des-klima-suenders-beton/1806968|access-date=28 December 2020|website=www.spektrum.de|language=de}}</ref>

==See also==
{{Div col}}
* [[Asphalt concrete]]
* [[Calcium aluminate cements]]
* [[Cement chemist notation]]
* [[Cement render]]
* [[Cenocell]]
* [[Energetically modified cement]] (EMC)
* [[Fly ash]]
* [[Geopolymer cement]]
* [[Portland cement]]
* [[Rosendale cement]]
* [[Sulfate attack in concrete and mortar]]
* [[Sulfur concrete]]
* [[Tiocem]]
* [[List of countries by cement production]]
{{Div col end}}

==References==
{{reflist|refs
<ref name="ty01">H. F. W. Taylor, Cement chemistry, 2nd ed. London: T. Telford, 1997.</ref>
<ref name="scr01">Scrivener, K.L., Crumbie, A.K., and Laugesen P. (2004). "The Interfacial Transition Zone (ITZ) between cement paste and aggregate in concrete." Interface Science, '''12 (4)''', 411–421. doi: 10.1023/B:INTS.0000042339.92990.4c.
</ref>
}}

==Further reading==
{{Refbegin}}
* {{Cite book|last1=Taylor|first1=Harry F. W.|author-link=Harry F. W. Taylor|date=1997|title=Cement Chemistry|publisher=Thomas Telford|pages=|isbn=978-0-7277-2592-9|url={{google books|plainurl=y|id=1BOETtwi7mMC}}}}
* {{cite book|author1=Peter Hewlett|author2=Martin Liska|date=2019|title=Lea's Chemistry of Cement and Concrete|publisher=Butterworth-Heinemann|pages=|isbn=978-0-08-100795-2|url={{google books|plainurl=y|id=0cxPCgAAQBAJ}}}}
* {{Cite journal|ref=none|last=Aitcin|first=Pierre-Claude|title=Cements of yesterday and today: Concrete of tomorrow|journal=Cement and Concrete Research|volume=30|issue=9|pages=1349–1359|doi=10.1016/S0008-8846(00)00365-3|year=2000}}
* {{Cite journal|ref=none|last=van Oss|first=Hendrik G.|author2=Padovani, Amy C.|title=Cement manufacture and the environment, Part I: Chemistry and Technology|journal=Journal of Industrial Ecology|volume=6|issue=1|pages=89–105|doi=10.1162/108819802320971650|year=2002|bibcode=2002JInEc...6...89O|s2cid=96660377}}
* {{Cite journal|ref=none|last=van Oss|first=Hendrik G.|author2=Padovani, Amy C.|title=Cement manufacture and the environment, Part II: Environmental challenges and opportunities|journal=Journal of Industrial Ecology|volume=7|issue=1|pages=93–126|doi=10.1162/108819803766729212|year=2003|bibcode=2003JInEc...7...93O|url=http://wbcsdcement.org/pdf/tf4/JIE-article-winter-2003-part-2.pdf|citeseerx=10.1.1.469.2404|s2cid=44083686|access-date=24 October 2017|archive-date=22 September 2017|archive-url=https://web.archive.org/web/20170922012016/http://wbcsdcement.org/pdf/tf4/JIE-article-winter-2003-part-2.pdf|url-status=usurped}}
*{{Cite book|title=Designing green cement plants|last=Deolalkar, S. P.|publisher=Butterworth-Heinemann|year=2016|isbn=9780128034354|location=Amsterdam|oclc=919920182|ref=none}}
* Friedrich W. Locher: ''Cement : Principles of production and use'', Düsseldorf, Germany: Verlag Bau + Technik GmbH, 2006, {{ISBN|3-7640-0420-7}}
* Javed I. Bhatty, F. MacGregor Miller, Steven H. Kosmatka; editors: ''Innovations in Portland Cement Manufacturing'', SP400, [[Portland Cement Association]], Skokie, Illinois, U.S., 2004, {{ISBN|0-89312-234-3}}
* [https://www.carbonbrief.org/qa-why-cement-emissions-matter-for-climate-change "Why cement emissions matter for climate change"] {{Webarchive|url=https://web.archive.org/web/20190321070251/https://www.carbonbrief.org/qa-why-cement-emissions-matter-for-climate-change |date=21 March 2019 }} ''Carbon Brief'' 2018
* {{Cite book|ref=none|last=Neville|first=A.M.|year=1996|title=Properties of concrete. Fourth and final edition standards|publisher=Pearson, Prentice Hall|isbn=978-0-582-23070-5|oclc=33837400}}
* {{Cite book|ref=none|last=Taylor|first=H.F.W.|title=Cement chemistry|url=https://archive.org/details/cementchemistry00tayl|url-access=limited|year=1990|publisher=Academic Press|isbn=978-0-12-683900-5|page=[https://archive.org/details/cementchemistry00tayl/page/n490 475]}}
* {{Cite journal|ref=none|last=Ulm|first=Franz-Josef|author2=Roland J.-M. Pellenq|author3=Akihiro Kushima|author4=Rouzbeh Shahsavari|author5=Krystyn J. Van Vliet|author6=Markus J. Buehler|author7=Sidney Yip|title=A realistic molecular model of cement hydrates|journal=Proceedings of the National Academy of Sciences|volume=106|issue=38|pages=16102–16107|doi=10.1073/pnas.0902180106|pmid=19805265|year=2009|bibcode=2009PNAS..10616102P|pmc=2739865|doi-access=free}}
{{Refend}}

==External links==
{{Commons category|Cement}}
* {{Cite EB1911|wstitle=Cement |volume=5 |short=x}}
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