Editing Terrazzo

{{Short description|Cementitious composite material, usually used in flooring}}
{{For|the Italian town|Terrazzo, Italy}}
[[File:Terrazzo entryway.jpg|thumb|Terrazzo entryway on Beverley Street in [[Staunton, Virginia]], U.S.]]
[[File:Hollywood Walk of Fame (7960322318).jpg|thumb|upright|One of the most well known examples of terrazzo flooring is the [[Hollywood Walk of Fame]].]]
'''Terrazzo''' is a composite material, poured in place or precast, which is used for floor and wall treatments. It consists of  chips of [[marble]], [[quartz]], [[granite]], [[glass]], or other suitable material, poured with a [[cementitious]] binder (for chemical binding), [[polymer]]ic (for physical binding), or a combination of both. Metal strips often divide sections, or changes in color or material in a pattern.  Additional chips may be sprinkled atop the mix before it sets.  After it is cured it is ground and polished smooth or otherwise finished to produce a uniformly textured surface.  "Terrazzo" is also often used to describe any pattern similar to the original terrazzo floors.<ref>{{cite news |last1=Brooke |first1=Eliza |title=Terrazzo used to be kitschy. Now it's on everything from Spalding basketballs to Madewell dresses. |url=https://www.vox.com/the-goods/2019/10/15/20906410/terrazzo-fashion-home |access-date=15 October 2019 |work=[[Vox (website)|Vox]] |date=15 October 2019}}</ref>
Modern forms of terrazzo include [[polished concrete]].

==History==
===Terrazzo proper===
Although the history of terrazzo can be traced back to the ancient [[mosaic]]s of Egypt, its more recent predecessors come from Italy. The form of terrazzo used today derives partly from the 18th century ''pavimento alla Veneziana'' ([[Venice|Venetian]] pavement) and the cheaper ''seminato.'' ''Pavimento alla Veneziana'' had workers place marble fragments next to each other in a mortar base. Terrazzo is also related to the technique ''seminato'' for which workers tossed larger marble chips into the cement that was then ground and polished. Together, these methods create the generic form of terrazzo that involves pieces of stone that are bonded to a cement bed. Terrazzo was first introduced in the United States in the late 1890s, but did not achieve popularity until the 1920s.<ref name=":03">{{cite book|title=Twentieth Century Materials: History and Conservation|last1=Johnson|first1=Walter|date=1995|publisher=McGraw Hill|location=New York|page=203}}</ref> Until then it was hand polished with a long handled tool called a ''galera''.<ref name=":03" /> Due to its likelihood of cracking, terrazzo was used at a small scale in comparison to the large expanses we see today. Two inventions resulted in its rise in popularity: divider strips and the electric grinding machine. The invention of divider strips by L. Del Turco and Bros. in 1924 contained the cracking of terrazzo by allowing the material greater space to expand and shrink after installation. This invention made terrazzo a durable and reliable material in addition to allowing for further design work within the floor.<ref name=":12">{{Cite book |url=https://sds-me.com/cement-terrazzo/ |title=Cement Terrazzo |date=27 March 2024}}</ref> Installers use the dividing strips as guides when they work with different colored terrazzo. Additionally, the electric grinding machine and mechanization of the production process cut down on costs and installation time, making terrazzo an affordable flooring option.

[[Art Deco]] and [[Streamline Moderne|Moderne]] styles from the 1920s to 1940s favored terrazzo with the dividers allowing for straight or curved lines that increased the decorative potential.<ref name=":22">{{cite book|title=Twentieth Century Materials: History and Conservation|last1=Jester|first1=Thomas|date=1995|publisher=McGraw Hill|location=New York|page=204}}</ref> The popularity of terrazzo led to an increase in installers in the 1920s. The National Terrazzo and Mosaic Organization was formed in 1931 to further professionalize the practice of terrazzo installation.<ref name=":32">{{cite book|title=Twentieth Century Materials: History and Conservation|last1=Jester|first1=Thomas|date=1995|publisher=McGraw Hill|location=New York|page=205}}</ref> One of the best-known examples of terrazzo is the [[Hollywood Walk of Fame]]. Created in 1958, the walk honors celebrities in the form of a terrazzo star that displays their name.<ref name=":42">{{cite web|url=http://www.hollywoodchamber.net/|title=Hollywood Chamber of Commerce}}</ref>

===Archaeological use of the term===
Archaeologists have adopted the term ''terrazzo'' to describe the floors of early [[Neolithic]] buildings ([[PPNA]] and [[PPNB]], ca. 9,000–8,000 BC) in [[Western Asia]] constructed of burnt [[Lime (mineral)|lime]] and clay, colored red with [[ochre]] and polished. The embedded crushed limestone gives it a slightly mottled appearance. The use of fire to produce burnt lime, which was also used for the [[hafting]] of implements, predates production of fired pottery by almost a thousand years.{{citation needed|date=June 2016}} In the early Neolithic settlement of [[Çayönü]] in eastern [[Turkey]] about {{convert|90|m2|abbr=on}} of terrazzo floors have been uncovered. The floors of the PPN B settlement of [[Nevalı Çori]] measure about {{convert|80|m2|abbr=on}}. They are {{convert|15|cm|abbr=on}} thick, and contain about 10–15% lime.

These floors are almost impenetrable to moisture and very durable, but their construction involved a high input of energy. Gourdin and Kingery (1975) estimate that the production of any given amount of lime requires about five times that amount of wood.<ref>{{cite journal |last1=Gourdin |first1=W. H. |last2=Kingery |first2=W. D. |title=The Beginnings of Pyrotechnology: Neolithic and Egyptian Lime Plaster |journal=Journal of Field Archaeology |volume=2 |issue=1–2 |pages=133–150 |doi=10.1179/009346975791491277 |year=1975 }}</ref>{{clarify|Five times what?|date=June 2016}} Recent experiments by Affonso and Pernicka<ref>{{cite book |last1=Affonso |first1=Maria Thais Crepaldi |last2=Pernicka |first2=Ernst |chapter=Neolithic Lime Plasters and Pozzolanic Reactions: Are They Occasional Occurrences? |editor1-first=Rainer Michael |editor1-last=Boehmer |editor2-first=Joseph |editor2-last=Maran |title=Lux orientis: Archäologie Zwischen Asien und Europa. Festschrift für Harald Hauptmann zum 65. Geburtstag |chapter-url=https://books.google.com/books?ei=ZWW8UfiFE8PD0gGRxIHwCg |access-date=15 June 2013 |series=Internationale Archäologie: Studia honoraria Volume 12 |year=2001 |publisher=Verlag Marie Leidorf |location=Rahden/Westfallen, Germany |isbn=9783896463920 |oclc=646779465 |pages=9–13}}</ref> have shown that only twice the amount is needed, but that would still amount to 4.5 metric tonnes of dry wood for the floors in Çayönü. Other sites with terrazzo floors include Nevalı Çori, [[Göbekli Tepe]], [[Tell es-Sultan|Jericho]], and [[Kastros]] ([[history of Cyprus|Cyprus]]).

== Production ==
[[File:Pima1.jpg|thumb|Terrazzo with stylized Native-American design at the [[Hoover Dam]]]]
[[File:Gamla stan tunnelbana terrazzo 070330.JPG|thumb|Terrazzo wall at the [[Gamla stan]] metro station, [[Stockholm]]]]

Terrazzo artisans create walls, floors, [[patio]]s, and panels by exposing marble chips and other fine aggregates on the surface of finished [[concrete]] or [[epoxy]]-resin. Much of the preliminary work of terrazzo workers is similar to that of [[cement masons]]. Marble-chip, cementitious terrazzo requires three layers of materials. First, cement masons or terrazzo workers build a solid, level concrete foundation that is {{convert|3|to|4|in}} deep. After the forms are removed from the foundation, workers add a {{convert|1|in}} layer of sandy concrete. Before this layer sets, terrazzo workers partially embed metal divider strips in the concrete wherever there is to be a joint or change of color in the terrazzo. For the final layer, terrazzo workers blend and place into each of the panels a fine marble chip mixture that may be color-pigmented. While the mixture is still wet, workers toss additional marble chips of various colors into each panel and roll a weighted roller ({{convert|100|–|125|lb}}) over the entire surface.

In the 1970s, [[polymer]]-based terrazzo was introduced and is called thin-set terrazzo. Initially polyester and [[vinyl ester resin|vinyl ester]] resins were used as the binder resin. Today, most of the terrazzo installed is epoxy terrazzo.  The advantages of this material over cementitious terrazzo include a wider selection of colors, {{convert|1/4|to|3/8|in}} installation thickness, lighter weight, faster installation, impermeable finish, higher strength, and less susceptibility to cracking. The disadvantage of epoxy resin–based terrazzo is that it can only be used for interior, not exterior, applications. Epoxy-based terrazzo will lose its color and slightly peel when used outdoors, whereas cement-based terrazzo will not. In addition to marble aggregate blends, other aggregates have been used, such as [[mother of pearl]] and [[abalone]] shell. Recycled aggregates include: glass, porcelain, concrete, and metal. Shapes and medallions can be fabricated on site by bending divider strips, or off site by [[water-jet cutting]].

When the terrazzo is thoroughly cured, helpers grind it with a [[concrete grinder|terrazzo grinder]], which is somewhat like a [[floor polisher]], only much heavier. Slight depressions left by the grinding are filled with a matching [[grout]] material and hand-[[trowel]]ed for a smooth, uniform surface; it is then cleaned, polished, and sealed.<ref>{{cite web |url=http://stats.bls.gov/ooh/Construction-and-Extraction/Cement-mason-and-terrazzo-workers.htm |title=Cement Masons and Terrazzo Workers |date=29 March 2012 |work=Occupational Outlook Handbook, 2012–13 Edition |publisher=[[Bureau of Labor Statistics]], [[United States Department of Labor|U.S. Department of Labor]] |access-date=15 June 2013}}</ref>

=== Types and systems ===
[[File:Norfolk and Western Railway terrazzo logo.jpg|thumb|left|[[Norfolk and Western Railway]] terrazzo logo, Roanoke, Virginia]]
Terrazzo installation includes both bonded and unbonded methods.  Bonded systems include: bonded underbed, monolithic, chemically bonded, and the most recent, thin set method ([[epoxy]] resin). Bonded terrazzo is applied over a sand-cement mortar underbed which sits on top of a concrete slab. The sand-cement layer allows for variations in the finished concrete slab that it sits on. Monolithic terrazzo is applied directly over an extremely flat and high quality concrete sub-floor. Thin-set terrazzo does not require a concrete sub-floor. Instead, a flexible membrane can be installed so that cracks do not appear on the surface.<ref>{{Cite news|url=https://www.archtoolbox.com/materials-systems/finishes/flooringterrazzo.html|title=Flooring - Terrazzo - archtoolbox.com|work=archtoolbox.com|access-date=2017-12-05|language=en-GB}}</ref> Unbonded includes the sand cushion method which uses wire reinforcing, an isolation sheet, and sand dusting that absorbs any movement from the concrete slab.<ref name="McGraw Hill">{{cite book|title=Twentieth Century Materials: History and Conservation|last1=Jester|first1=Thomas|date=1995|publisher=McGraw Hill|location=New York|page=207}}</ref>

=== Relation to mosaics ===
Although terrazzo derives from the mosaic artform, it does not necessarily place individual pieces in a decorative pattern. Instead, small pieces are thrown into the mortar base creating a more uniform surface appearance. Decorative patterns are often created by using dividers which creates lines between different colored terrazzo mixtures.

=== Deterioration ===
Cracking is a common form of failure and is often caused by the structural system that supports the terrazzo rather than the material itself. Contact with [[alkali]]s or [[acid]]s can deteriorate the bonding agents used in terrazzo. As the aggregates are often marble dust which is [[calcium carbonate]], strong acid can also cause deterioration to the aggregates. When partial replacement is necessary, a "bracketing" system mixing and matching different chips is used to create potential matches.<ref name="McGraw Hill"/> Aged terrazzo can be resurfaced to restore its original look by re-polishing.<ref>{{Cite web|url=https://www.gsa.gov/technical-procedures/regrinding-terrazzo-floors?Form_Load=88517|title = Regrinding Terrazzo Floors| date=10 August 2016 }}</ref>

==See also==
* [[Engineered stone]]
* [[Mosaic]]
* [[Polished concrete]]
* [[Portuguese pavement]]

==References==
{{Reflist}}

== External links ==
* {{Commons category-inline}}

{{Authority control}}

[[Category:Decorative arts]]
[[Category:Floors]]
[[Category:Pre-Pottery Neolithic]]