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'''Reinforced concrete'''
==Description==
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[[File:Expo58 building Philips.jpg|thumb|The novel shape of the [[Philips Pavilion]] built in [[Brussels]] for [[Expo 58]] was achieved using reinforced concrete]]
[[Joseph Monier]], a 19th-century French gardener, was a pioneer in the development of structural, prefabricated and reinforced concrete, having been dissatisfied with the existing materials available for making durable flowerpots.<ref>{{cite book |last=Day |first=Lance |title=Biographical Dictionary of the History of Technology |url=https://archive.org/details/isbn_9780415060424 |url-access=registration |page=[https://archive.org/details/isbn_9780415060424/page/284 284] |publisher=Routledge |year=2003 |isbn=0-203-02829-5}}</ref> He was granted a patent for reinforcing concrete flowerpots by means of mixing a wire mesh and a mortar shell. In 1877, Monier was granted another patent for a more advanced technique of reinforcing concrete columns and girders, using iron rods placed in a grid pattern. Though Monier undoubtedly knew that reinforcing concrete would improve its inner cohesion, it is not clear whether he even knew how much the [[Ultimate tensile strength|tensile strength]] of concrete was improved by the reinforcing.<ref name=Mörsch>{{cite book |last=Mörsch |first=Emil |title=Concrete-steel Construction: (Der Eisenbetonbau) |year=1909 |publisher=The Engineering News Publishing Company |pages=
▲[[François Coignet]] used iron-reinforced concrete as a technique for constructing building structures.<ref name="britannia">{{cite encyclopedia |url=https://www.britannica.com/technology/building-construction/Early-steel-frame-high-rises#ref105155 |title=Building construction: The invention of reinforced concrete |url-access=subscription |encyclopedia=Encyclopedia Britannica |access-date=2018-09-27 |archive-date=2018-09-28 |archive-url=https://web.archive.org/web/20180928005354/https://www.britannica.com/technology/building-construction/Early-steel-frame-high-rises#ref105155 |url-status=live }}</ref> In 1853, Coignet built the first iron reinforced concrete structure, a four-story house at 72 [[rue Charles Michels]] in the suburbs of Paris.<ref name="britannia" /> Coignet's descriptions of reinforcing concrete suggests that he did not do it for means of adding strength to the concrete but for keeping walls in monolithic construction from overturning.<ref name="Condit">{{cite journal |last=Condit |first=Carl W. |journal=Technology and Culture |title=The First Reinforced-Concrete Skyscraper: The Ingalls Building in Cincinnati and Its Place in Structural History |date=January 1968 |volume=9 |issue=1 |pages=1–33 |doi=10.2307/3102041 |jstor=3102041}}</ref> The Pippen building in [[New York and Long Island Coignet Stone Company Building|Brooklyn]] stands as a testament to his technique. In 1854, English builder William B. Wilkinson reinforced the concrete roof and floors in the two-story house he was constructing. His positioning of the reinforcement demonstrated that, unlike his predecessors, he had knowledge of tensile stresses.<ref>{{cite web | url =http://www.theconcreteproducer.com/Images/The%20History%20of%20Concrete%2C%20Part%202_tcm77-1306954.pdf | title =History of Concrete | year =1995 | author =Richard W. S | publisher =The Aberdeen Group | access-date =25 April 2015 | archive-url =https://web.archive.org/web/20150528183822/http://www.theconcreteproducer.com/Images/The%20History%20of%20Concrete%2C%20Part%202_tcm77-1306954.pdf | archive-date =28 May 2015 | url-status =dead | df =dmy-all }}</ref><ref>{{cite web| url = http://www.jfccivilengineer.com/reinforced_concrete.htm| title = Reinforced Concrete| work = The Elements of Structure| year = 1995| author = W. Morgan| via = John F. Claydon's website| access-date = 25 April 2015| archive-date = 12 October 2018| archive-url = https://web.archive.org/web/20181012133730/http://www.jfccivilengineer.com/reinforced_concrete.htm| url-status = live}}</ref><ref name="CIVL1101">{{cite web |url= http://www.ce.memphis.edu/1101/notes/concrete/section_2_history.html |title= History of Concrete Building Construction |year= 2015 |website= CIVL 1101 – History of Concrete |author= Department of Civil Engineering |publisher= University of Memphis |access-date= 25 April 2015 |archive-date= 27 February 2017 |archive-url= https://web.archive.org/web/20170227213256/http://www.ce.memphis.edu/1101/notes/concrete/section_2_history.html |url-status= live }}</ref>
Before the 1870s, the use of concrete construction, though dating back to the [[Roman Empire]], and having been reintroduced in the early 19th century, was not yet a proven scientific technology. [[Thaddeus Hyatt]], published a report entitled ''An Account of Some Experiments with Portland-Cement-Concrete Combined with Iron as a Building Material, with Reference to Economy of Metal in Construction and for Security against Fire in the Making of Roofs, Floors, and Walking Surfaces'', in which he reported his experiments on the behavior of reinforced concrete. His work played a major role in the evolution of concrete construction as a proven and studied science. Without Hyatt's work, more dangerous trial and error methods might have been depended on for the advancement in the technology.<ref name="Condit"/><ref>{{cite book| last=Collins| first=Peter| title=Concrete: The Vision of a New Architecture| date=1920–1981| publisher=McGill-Queen's University Press| isbn=
▲[[Joseph Monier]], a 19th-century French gardener, was a pioneer in the development of structural, prefabricated and reinforced concrete, having been dissatisfied with the existing materials available for making durable flowerpots.<ref>{{cite book |last=Day |first=Lance |title=Biographical Dictionary of the History of Technology |url=https://archive.org/details/isbn_9780415060424 |url-access=registration |page=[https://archive.org/details/isbn_9780415060424/page/284 284] |publisher=Routledge |year=2003 |isbn=0-203-02829-5}}</ref> He was granted a patent for reinforcing concrete flowerpots by means of mixing a wire mesh and a mortar shell. In 1877, Monier was granted another patent for a more advanced technique of reinforcing concrete columns and girders, using iron rods placed in a grid pattern. Though Monier undoubtedly knew that reinforcing concrete would improve its inner cohesion, it is not clear whether he even knew how much the [[Ultimate tensile strength|tensile strength]] of concrete was improved by the reinforcing.<ref name=Mörsch>{{cite book |last=Mörsch |first=Emil |title=Concrete-steel Construction: (Der Eisenbetonbau) |year=1909 |publisher=The Engineering News Publishing Company |pages=[https://archive.org/details/concretesteelco00goodgoog/page/n221 204]–210 |url=https://archive.org/details/concretesteelco00goodgoog}}</ref>
[[Ernest L. Ransome]], an English-born engineer, was an early innovator of reinforced concrete techniques at the end of the 19th century. Using the knowledge of reinforced concrete developed during the previous 50 years, Ransome improved nearly all the styles and techniques of the earlier inventors of reinforced concrete. Ransome's key innovation was to twist the reinforcing steel bar, thereby improving its bond with the concrete.<ref>{{cite web| last1=Mars| first1=Roman| title=Episode 81: Rebar and the Alvord Lake Bridge| url=http://99percentinvisible.org/episode/episode-81-rebar-and-the-alvord-lake-bridge/|
▲Before the 1870s, the use of concrete construction, though dating back to the [[Roman Empire]], and having been reintroduced in the early 19th century, was not yet a proven scientific technology. [[Thaddeus Hyatt]], published a report entitled ''An Account of Some Experiments with Portland-Cement-Concrete Combined with Iron as a Building Material, with Reference to Economy of Metal in Construction and for Security against Fire in the Making of Roofs, Floors, and Walking Surfaces'', in which he reported his experiments on the behavior of reinforced concrete. His work played a major role in the evolution of concrete construction as a proven and studied science. Without Hyatt's work, more dangerous trial and error methods might have been depended on for the advancement in the technology.<ref name="Condit"/><ref>{{cite book|last=Collins|first=Peter|title=Concrete: The Vision of a New Architecture|date=1920–1981|publisher=McGill-Queen's University Press|isbn=0-7735-2564-5|pages=58–60|url=https://books.google.com/books?id=7Zttxa_oHcEC&q=Thaddeus+Hyatt+concrete&pg=PA58|access-date=2020-11-02|archive-date=2021-07-09|archive-url=https://web.archive.org/web/20210709160746/https://books.google.com/books?id=7Zttxa_oHcEC&q=Thaddeus+Hyatt+concrete&pg=PA58|url-status=live}}</ref>
▲[[Ernest L. Ransome]], an English-born engineer, was an early innovator of reinforced concrete techniques at the end of the 19th century. Using the knowledge of reinforced concrete developed during the previous 50 years, Ransome improved nearly all the styles and techniques of the earlier inventors of reinforced concrete. Ransome's key innovation was to twist the reinforcing steel bar, thereby improving its bond with the concrete.<ref>{{cite web|last1=Mars|first1=Roman|title=Episode 81: Rebar and the Alvord Lake Bridge|url=http://99percentinvisible.org/episode/episode-81-rebar-and-the-alvord-lake-bridge/|website=[[99% Invisible]]|access-date=6 August 2014|archive-date=8 August 2014|archive-url=https://web.archive.org/web/20140808074102/http://99percentinvisible.org/episode/episode-81-rebar-and-the-alvord-lake-bridge/|url-status=live}}</ref> Gaining increasing fame from his concrete constructed buildings, Ransome was able to build two of the first reinforced concrete bridges in North America.<ref>{{cite book|last=Collins|first=Peter|title=Concrete: The Vision of a New Architecture|date=1920–1981|publisher=McGill-Queen's University Press|isbn=0-7735-2564-5|pages=61–64|url=https://books.google.com/books?id=7Zttxa_oHcEC&pg=PA58|access-date=2016-04-03|archive-date=2021-07-09|archive-url=https://web.archive.org/web/20210709160745/https://books.google.com/books?id=7Zttxa_oHcEC&pg=PA58|url-status=live}}</ref> One of his [[Smith-Ransome Japanese Bridge|bridges]] still stands on Shelter Island in New Yorks East End, One of the first concrete buildings constructed in the United States was a [[William E. Ward House|private home designed by William Ward]], completed in 1876. The home was particularly designed to be fireproof.
[[:de:Gustav Adolf Wayss|G. A. Wayss]] was a German civil engineer and a pioneer of the iron and steel concrete construction. In 1879, Wayss bought the German rights to Monier's patents and, in 1884, his firm, [[:de:Wayss & Freytag|Wayss & Freytag]], made the first commercial use of reinforced concrete. Up until the 1890s, Wayss and his firm greatly contributed to the advancement of Monier's system of reinforcing, established it as a well-developed scientific technology.<ref name=Mörsch/>
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One of the first [[skyscraper]]s made with reinforced concrete was the 16-story [[Ingalls Building]] in Cincinnati, constructed in 1904.<ref name=CIVL1101/>
The first reinforced concrete building in Southern California was the [[Homer Laughlin Building|Laughlin Annex]] in downtown [[Los Angeles]], constructed in 1905.<ref>{{Cite book |url=https://books.google.com/books?id=
In 1906, a partial collapse of the Bixby Hotel in Long Beach killed 10 workers during construction when shoring was removed prematurely. That event spurred a scrutiny of concrete erection practices and building inspections. The structure was constructed of reinforced concrete frames with hollow clay tile ribbed flooring and hollow clay tile infill walls. That practice was strongly questioned by experts and recommendations for
In April 1904, [[Julia Morgan]], an American architect and engineer, who pioneered the aesthetic use of reinforced concrete, completed her first reinforced concrete structure, El Campanil, a {{convert|72|ft|adj=on}} bell tower at [[Mills College]],<ref name="El Campanil">{{cite web|title=El Campanil, Mills College: Julia Morgan 1903-1904|url=https://www.bluffton.edu/homepages/facstaff/sullivanm/jmmills/jmcampanil.html|access-date=18 April 2019|archive-date=30 December 2018|archive-url=https://web.archive.org/web/20181230165410/http://www.bluffton.edu/homepages/facstaff/sullivanm/jmmills/jmcampanil.html|url-status=live}}</ref> which is located across the bay from [[San Francisco]]. Two years later, El Campanil survived the [[1906 San Francisco earthquake]] without any damage,<ref name="morgan 1904">{{cite web |last1=Callen |first1=Will |date=4 February
In 1906, the National Association of Cement Users (NACU) published ''Standard No. 1''<ref>{{Cite book |title=Standard Specifications for Portland Cement of the American Society for Testing Materials, Standard No. 1 |publisher=National Association of Cement Users |year=1906 |location=Philadelphia, PA}}</ref> and, in 1910, the ''Standard Building Regulations for the Use of Reinforced Concrete''.<ref>{{Cite book |title=Standard Building Regulations for the Use of Reinforced Concrete |publisher=National Association of Cement Users |year=1910 |location=Philadelphia, PA}}</ref>
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== Use in construction ==
[[File:SagradaFamiliaRoof2.jpg|thumb|upright=1.5|right|Rebars of [[Sagrada Família]]'s roof in construction (2009)]]
[[File:O Cristo Redentor.JPG|thumb|''[[Christ the Redeemer (statue)|Christ the Redeemer]]'' statue in Rio de Janeiro, Brazil. It is made of reinforced concrete clad in a mosaic of thousands of triangular [[soapstone]] tiles.<ref name="brit">{{Cite encyclopedia |title=Christ the Redeemer (last updated 13 January 2014) |encyclopedia=[[Encyclopædia Britannica]] |url=http://www.britannica.com/EBchecked/topic/1435544/Christ-the-Redeemer |access-date=November 5, 2022 |last1=Murray |first1=Lorraine}}</ref>]]
Many different types of structures and components of structures can be built using reinforced concrete elements including [[Concrete slab|slab]]s, [[wall]]s, [[beam (structure)|beams]], [[column]]s, [[foundation (architecture)|foundations]], [[framing (construction)|frame]]s and more.
Reinforced concrete can be classified as [[precast]] or [[concrete|cast-in-place concrete]].
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Without reinforcement, constructing modern structures with concrete material would not be possible.
===Reinforced concrete elements===
When reinforced concrete elements are used in construction, these reinforced concrete elements exhibit basic behavior when subjected to external [[structural load|loads]]. Reinforced concrete elements may be subject to [[tension (physics)|tension]], [[compression (physics)|compression]], [[bending]], [[shear stress|shear]], and/or [[torsion (mechanics)|torsion]].<ref>{{cite book | author1=Bungale S. Taranath |title=Reinforced Concrete Design of Tall Buildings |publisher= CRC Press |year=2009 |page=7 |isbn=9781439804810 }}</ref>
==Behavior ==
===Materials===
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===Anchorage (bond) in concrete: Codes of specifications===
Because the actual bond stress varies along the length of a bar anchored in a zone of tension, current international codes of specifications use the concept of development length rather than bond stress. The main requirement for safety against bond failure is to provide a sufficient extension of the length of the bar beyond the point where the steel is required to develop its yield stress and this length must be at least equal to its development length. However, if the actual available length is inadequate for full development, special anchorages must be provided, such as cogs or hooks or mechanical end plates. The same concept applies to lap splice length <ref>{{Cite journal|title=Monotonic and Cyclic Seismic Analyses of Old-Type RC Columns with Short Lap Splices|journal=Construction Materials|date=31 March 2024|volume=4|issue=2|pages=329–341|last1=Megalooikonomou|first1=Konstantinos G.|doi=10.3390/constrmater4020018 |doi-access=free }}</ref> mentioned in the codes where splices (overlapping) provided between two adjacent bars in order to maintain the required continuity of stress in the splice zone.
===Anticorrosion measures===
In wet and cold climates, reinforced concrete for roads, bridges, parking structures and other structures that may be exposed to [[deicing]] salt may benefit from use of corrosion-resistant reinforcement such as uncoated, low carbon/chromium (micro composite), epoxy-coated, hot dip galvanized or [[stainless steel]] rebar. Good design and a well-chosen concrete mix will provide additional protection for many applications.
Uncoated, low carbon/chromium rebar looks similar to standard carbon steel rebar due to its lack of a coating; its highly corrosion-resistant features are inherent in the steel microstructure. It can be identified by the unique ASTM specified mill marking on its smooth, dark charcoal finish. Epoxy Another, cheaper way of protecting rebars is coating them with [[zinc phosphate]].<ref>{{cite journal |title=Effect of zinc phosphate chemical conversion coating on corrosion behavior of mild steel in alkaline medium: protection of rebars in reinforced concrete |first1=Florica |last1=Simescu |first2=Hassane |last2=Idrissi |publisher=National Institute for Materials Science |journal=Science and Technology of Advanced Materials |volume=9 |issue=4 |pages=045009 |date=December 19, 2008 |pmc=5099651 |doi=10.1088/1468-6996/9/4/045009 |pmid=27878037 |bibcode=2008STAdM...9d5009S }}</ref> Zinc phosphate slowly reacts with [[calcium]] cations and the [[hydroxyl]] anions present in the cement pore water and forms a stable [[hydroxyapatite]] layer.
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{{Main|Prestressed concrete}}
Prestressing concrete is a technique that greatly increases the load-bearing strength of concrete beams. The reinforcing steel in the bottom part of the beam, which will be subjected to tensile forces when in service, is placed in tension before the concrete is poured around it. Once the concrete has hardened, the tension on the reinforcing steel is released, placing a built-in compressive force on the concrete. When loads are applied, the reinforcing steel takes on more stress and the compressive force in the concrete is reduced, but does not become a tensile force. Since the concrete is always under compression, it is less subject to cracking and failure.<ref>{{Cite book|url=https://www.worldcat.org/oclc/20693897|title=Structural materials|
== Common failure modes of steel reinforced concrete ==
[[File:Concrete spall (interior of unit).jpg|thumb|Concrete spalling from the ceiling of an office unit (''interior'') in [[Singapore]], possibly due to rebar corrosion. |alt=|upright]]
Reinforced concrete can fail due to inadequate strength, leading to mechanical failure, or due to a reduction in its durability. Corrosion and freeze/thaw cycles may damage poorly designed or constructed reinforced concrete. When rebar corrodes, the oxidation products ([[rust]]) expand and tends to flake, cracking the concrete and unbonding the rebar from the concrete. Typical mechanisms leading to durability problems are discussed below.
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The use of de-icing salts on roadways, used to lower the [[freezing point]] of water, is probably one of the primary causes of premature failure of reinforced or prestressed concrete bridge decks, roadways, and parking garages. The use of [[epoxy|epoxy-coated]] reinforcing bars and the application of [[cathodic protection]] has mitigated this problem to some extent. Also FRP (fiber-reinforced polymer) rebars are known to be less susceptible to chlorides. Properly designed concrete mixtures that have been allowed to cure properly are effectively impervious to the effects of de-icers.
Another important source of chloride ions is [[sea water]]. Sea water contains by weight approximately 3.5% salts. These salts include [[sodium chloride]], [[magnesium sulfate]], [[calcium sulfate]], and [[bicarbonate]]s. In water these salts dissociate in free ions (Na<sup>+</sup>, Mg<sup>2+</sup>, Cl<sup>−</sup>, {{chem|SO
In the 1960s and 1970s it was also relatively common for [[magnesite]], a chloride rich [[carbonate mineral]], to be used as a floor-topping material. This was done principally as a levelling and sound attenuating layer. However it is now known that when these materials come into contact with moisture they produce a weak solution of [[hydrochloric acid]] due to the presence of chlorides in the magnesite. Over a period of time (typically decades), the solution causes [[corrosion]] of the embedded [[rebar]]s. This was most commonly found in wet areas or areas repeatedly exposed to moisture.
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This a reaction of [[amorphous]] [[silica]] ([[chalcedony]], [[chert]], [[siliceous]] [[limestone]]) sometimes present in the [[Construction aggregate|aggregate]]s with the [[hydroxyl]] ions (OH<sup>−</sup>) from the cement pore solution. Poorly crystallized silica (SiO<sub>2</sub>) dissolves and dissociates at high pH (12.5 - 13.5) in alkaline water. The soluble dissociated [[silicic acid]] reacts in the porewater with the [[calcium hydroxide]] ([[portlandite]]) present in the [[cement]] paste to form an expansive [[calcium silicate hydrate]] (CSH). The [[alkali–silica reaction]] (ASR) causes localised swelling responsible for [[tensile stress]] and [[Fracture|cracking]]. The conditions required for alkali silica reaction are threefold:
(1) aggregate containing an alkali-reactive constituent (amorphous silica), (2) sufficient availability of hydroxyl ions (OH<sup>−</sup>), and (3) sufficient moisture, above 75% [[relative humidity]] (RH) within the concrete.<ref>{{cite web |url=https://www.bbc.co.uk/dna/h2g2/A4014172 |title=Concrete Cancer |website=h2g2 |publisher=BBC |date=March 15, 2012 |orig-year=2005 |access-date=2009-10-14 |archive-date=2009-02-23 |archive-url=https://web.archive.org/web/20090223173400/http://www.bbc.co.uk/dna/h2g2/A4014172 |url-status=live }}</ref><ref>{{cite web |url=http://www.cementindustry.co.uk/main.asp?page=272 |title=Special Section: South West Alkali Incident |website=the cement industry |publisher=British Cement Association |date=4 January 2006 |access-date=2006-11-26 |url-status=dead |archive-url=https://web.archive.org/web/20061029112122/http://www.cementindustry.co.uk/main.asp?page=272 |archive-date=October 29, 2006 }}</ref> This phenomenon is sometimes popularly referred to as "[[Alkali–silica reaction|concrete cancer]]". This reaction occurs independently of the presence of rebars; massive concrete structures such as [[dam]]s can be affected.
===Conversion of high alumina cement===
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==Fiber-reinforced concrete==
{{Main|Fiber
Fiber reinforcement is mainly used in [[shotcrete]], but can also be used in normal concrete. Fiber-reinforced normal concrete is mostly used for on-ground floors and pavements, but can also be considered for a wide range of construction parts (beams, pillars, foundations, etc.), either alone or with hand-tied rebars.
Concrete reinforced with fibers (which are usually steel, [[glass]], [[Fiber-reinforced plastic|plastic fibers]]) or cellulose polymer fiber is less expensive than hand-tied rebar.{{Citation needed|date=December 2017}} The shape, dimension, and length of the fiber are important. A thin and short fiber, for example short, hair-shaped glass fiber, is only effective during the first hours after pouring the concrete (its function is to reduce cracking while the concrete is stiffening), but it will not increase the concrete tensile strength. A normal-size fiber for European shotcrete (1 mm diameter, 45 mm length—steel or plastic) will increase the concrete's tensile strength. Fiber reinforcement is most often used to supplement or partially replace primary rebar, and in some cases it can be designed to fully replace rebar.<ref>
Steel is the strongest commonly available fiber,{{Citation needed|reason=I thought Aramid fibers were stronger, need a reliable source for this statement as it may not be fact based or is out-of-date.|date=December 2017}} and comes in different lengths (30 to 80 mm in Europe) and shapes (end-hooks). Steel fibers can only be used on surfaces that can tolerate or avoid corrosion and rust stains. In some cases, a steel-fiber surface is faced with other materials.
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==See also==
* [[Anchorage in reinforced concrete]]
* [[Concrete cover]]
* [[Concrete slab]]
* [[Corrosion engineering]]
* [[Cover
* [[Falsework]]
* [[Ferrocement]]
* [[Formwork]]
* [[Henri de Miffonis]]
* [[Interfacial
* [[Precast concrete]]
* [[Types of concrete]]▼
* [[Structural robustness]]▼
* [[Reinforced concrete structures durability]]
* [[Reinforced solid]]
▲* [[Structural robustness]]
▲* [[Types of concrete]]
== References ==
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