Editing Concrete (section)

===Classical era===
[[File:Rome (Italy, October 2019) - 275 (50589571796).jpg|thumb|Exterior of the [[Roman Pantheon]], finished 128 AD, the largest unreinforced concrete [[dome]] in the world.<ref>{{Cite web |title=Roman Concrete Research |first=David |last=Moore |url=http://www.romanconcrete.com/ |access-date=2022-08-13 |archive-url=https://web.archive.org/web/20141006012615/http://www.romanconcrete.com/|url-status=live |date=6 October 2014 |website= Romanconcrete.com|archive-date=6 October 2014 }}</ref>]]
[[File:Pantheon (Rome) - Dome.jpg|thumb|Interior of the Pantheon dome, seen from beneath. The concrete for the [[coffer]]ed dome was laid on moulds, mounted on temporary scaffolding.]]
[[File:Museo Foro Caesaragusta - Cloaca del foro 03.JPG|thumb|upright|''[[Opus caementicium]]'' exposed in a characteristic Roman arch. In contrast to modern concrete structures, the concrete used in Roman buildings was usually covered with brick or stone.]]

The Romans used concrete extensively from 300 BC to AD 476.<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> During the Roman Empire, [[Roman concrete]] (or ''[[opus caementicium]]'') was made from [[quicklime]], [[pozzolana]] and an aggregate of [[pumice]].<ref>{{Cite book |last=Chiu |first=Y. C. |url=https://books.google.com/books?id=osNrPO3ivZoC&dq=During+the+Roman+Empire,+Roman+concrete+(or+opus+caementicium)+was+made+from+quicklime,+pozzolana+and+an+aggregate+of+pumice.&pg=PA50 |title=An Introduction to the History of Project Management: From the Earliest Times to A.D. 1900 |date=2010 |publisher=Eburon Uitgeverij B.V. |isbn=978-90-5972-437-2 |pages=50 |language=en}}</ref> Its widespread use in many [[Architecture of ancient Rome|Roman structures]], a key event in the [[history of architecture]] termed the [[Roman architectural revolution]], freed [[Roman engineering|Roman construction]] from the restrictions of stone and brick materials. It enabled revolutionary new designs in terms of both structural complexity and dimension.<ref>{{Cite book| last = Lancaster| first = Lynne| title = Concrete Vaulted Construction in Imperial Rome. Innovations in Context| publisher=Cambridge University Press| date = 2005| isbn = 978-0-511-16068-4}}</ref> The [[Colosseum]] in Rome was built largely of concrete, and the [[Pantheon, Rome|Pantheon]] has the world's largest unreinforced concrete dome.<ref>{{cite web |url=http://www.romanconcrete.com/docs/chapt01/chapt01.htm |title=The Pantheon |first=David |last=Moore |work=romanconcrete.com |date=1999 |access-date=26 September 2011 |url-status=live |archive-url=https://web.archive.org/web/20111001052926/http://www.romanconcrete.com/docs/chapt01/chapt01.htm |archive-date=1 October 2011  }}</ref>

<blockquote>Concrete, as the Romans knew it, was a new and revolutionary material. Laid in the shape of [[arch]]es, [[Vault (architecture)|vaults]] and [[List of Roman domes|domes]], it quickly hardened into a rigid mass, free from many of the internal thrusts and strains that troubled the builders of similar structures in stone or brick.<ref>D.S. Robertson (1969). ''Greek and Roman Architecture'', Cambridge, p. 233</ref></blockquote>

Modern tests show that ''opus caementicium'' had a similar compressive strength to modern Portland-cement concrete (c. {{convert|200|kg/cm2|MPa psi|abbr=on|disp=sqbr}}).<ref>{{Cite book |last=Cowan |first=Henry J. |title=The master builders: a history of structural and environmental design from ancient Egypt to the nineteenth century |date=1977 |publisher=Wiley |isbn=0-471-02740-5 |location=New York |oclc=2896326}}</ref> However, due to the absence of reinforcement, its [[Ultimate tensile strength|tensile strength]] was far lower than modern [[reinforced concrete]], and its mode of application also differed:<ref>{{Cite web|url=http://www.ce.memphis.edu/1101/notes/concrete/section_2_history.html|archive-url=https://web.archive.org/web/20170227213256/http://www.ce.memphis.edu/1101/notes/concrete/section_2_history.html|title=CIVL 1101|archive-date=27 February 2017|website=www.ce.memphis.edu}}</ref>

<blockquote>Modern structural concrete differs from Roman concrete in two important details. First, its mix consistency is fluid and homogeneous, allowing it to be poured into forms rather than requiring hand-layering together with the placement of aggregate, which, in Roman practice, often consisted of [[rubble]]. Second, integral reinforcing steel gives modern concrete assemblies great strength in tension, whereas Roman concrete could depend only upon the strength of the concrete bonding to resist tension.<ref>Robert Mark, Paul Hutchinson: "On the Structure of the Roman Pantheon", ''Art Bulletin'', Vol. 68, No. 1 (1986), p. 26, fn. 5</ref></blockquote>

The long-term durability of Roman concrete structures was found to be due to the presence of [[Pyroclastic rock|pyroclastic]] (volcanic) rock and ash in the concrete mix. The crystallization of [[strätlingite]] (a complex calcium aluminosilicate hydrate)<ref>{{cite journal |doi = 10.1111/j.1151-2916.1995.tb08910.x|title = 29Si and27Al MASNMR Study of Stratlingite|journal = Journal of the American Ceramic Society |volume = 78|issue = 7|pages = 1921–1926|year = 1995|last1 = Kwan|first1 = Stephen|last2 = Larosa|first2 = Judith |last3=Grutzeck |first3= Michael W.}}</ref> during the formation of the concrete and its merging with similar calcium–aluminium-silicate–hydrate structures helped give the Roman concrete a greater degree of fracture resistance compared to modern concrete.<ref>{{cite journal|title=Mechanical resilience and cementitious processes in Imperial Roman architectural mortar|first1=Marie D.|last1=Jackson|first2=Eric N.|last2=Landis|first3=Philip F.|last3=Brune|first4=Massimo|last4=Vitti|first5=Heng|last5=Chen|first6=Qinfei|last6=Li|first7=Martin|last7=Kunz|first8=Hans-Rudolf|last8=Wenk|first9=Paulo J. M.|last9=Monteiro|first10=Anthony R.|last10=Ingraffea|date=30 December 2014|journal=PNAS|volume=111|issue=52|pages=18484–18489|doi=10.1073/pnas.1417456111|pmid=25512521|pmc=4284584|bibcode = 2014PNAS..11118484J|doi-access=free}}</ref> In addition, Roman concrete is significantly more resistant to erosion by seawater than modern concrete; the aforementioned pyroclastic materials react with seawater to form Al-[[tobermorite]] crystals over time.<ref>{{cite journal|periodical=American Mineralogist|title=Phillipsite and Al-tobermorite mineral cements produced through low-temperature water-rock reactions in Roman marine concrete|volume=102|issue=7|pages=1435–1450 |author1=Marie D. Jackson |author2=Sean R. Mulcahy |author3=Heng Chen |author4=Yao Li |author5=Qinfei Li |author6=Piergiulio Cappelletti |author7=Hans-Rudolf Wenk |date=3 July 2017 |bibcode=2017AmMin.102.1435J|doi=10.2138/am-2017-5993CCBY|s2cid=53452767|url=https://cedar.wwu.edu/geology_facpubs/67|doi-access=free }}</ref><ref>{{cite news|url=https://www.telegraph.co.uk/science/2017/07/03/secret-roman-concrete-survived-tidal-battering-2000-years-revealed/|title=Secret of how Roman concrete survived tidal battering for 2,000 years revealed|url-status=live|archive-url=https://web.archive.org/web/20170704011801/http://www.telegraph.co.uk/science/2017/07/03/secret-roman-concrete-survived-tidal-battering-2000-years-revealed/ |work=The Telegraph|date=3 July 2017|archive-date=4 July 2017|last1=Knapton|first1=Sarah}}</ref> The use of hot mixing in preparation of concrete, leading to the formation of lime clasts in the final product, has been proposed to give the Roman concrete a [[Self-healing concrete|self-healing ability]].<ref>{{cite journal |last1=Seymour |first1=Linda M. |last2=Maragh |first2=Janille |last3=Sabatini |first3=Paolo |last4=Di Tommaso |first4=Michel |last5=Weaver |first5=James C. |last6=Masic |first6=Admir |title=Hot mixing: Mechanistic insights into the durability of ancient Roman concrete |journal=Science Advances |date=6 January 2023 |volume=9 |issue=1 |pages=eadd1602 |doi=10.1126/sciadv.add1602 |pmc=9821858 |pmid=36608117 |bibcode=2023SciA....9D1602S }}</ref><ref>{{Cite web |last=Starr |first=Michelle |date=2024-02-01 |title=We Finally Know How Ancient Roman Concrete Was Able to Last Thousands of Years |url=https://www.sciencealert.com/we-finally-know-how-ancient-roman-concrete-was-able-to-last-thousands-of-years |access-date=2024-02-01 |website=ScienceAlert |language=en-US}}</ref>

The widespread use of concrete in many Roman structures ensured that many survive to the present day. The [[Baths of Caracalla]] in Rome are just one example. Many [[Roman aqueduct]]s and bridges, such as the magnificent [[Pont du Gard]] in southern France, have masonry cladding on a concrete core, as does the dome of the [[Pantheon, Rome|Pantheon]].