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Terrazzo is a composite material, poured in place or precast, which is used for floor and wall treatments. It consists of chips of
marble Marble is a metamorphic rock consisting of carbonate minerals (most commonly calcite (CaCO3) or Dolomite (mineral), dolomite (CaMg(CO3)2) that have recrystallized under the influence of heat and pressure. It has a crystalline texture, and is ty ...
,
quartz Quartz is a hard, crystalline mineral composed of silica (silicon dioxide). The Atom, atoms are linked in a continuous framework of SiO4 silicon–oxygen Tetrahedral molecular geometry, tetrahedra, with each oxygen being shared between two tet ...
,
granite Granite ( ) is a coarse-grained (phanerite, phaneritic) intrusive rock, intrusive igneous rock composed mostly of quartz, alkali feldspar, and plagioclase. It forms from magma with a high content of silica and alkali metal oxides that slowly coo ...
,
glass Glass is an amorphous (non-crystalline solid, non-crystalline) solid. Because it is often transparency and translucency, transparent and chemically inert, glass has found widespread practical, technological, and decorative use in window pane ...
, or other suitable material, poured with a cementitious binder (for chemical binding),
polymer A polymer () is a chemical substance, substance or material that consists of very large molecules, or macromolecules, that are constituted by many repeat unit, repeating subunits derived from one or more species of monomers. Due to their br ...
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. Modern forms of terrazzo include polished concrete.


History


Terrazzo proper

Although the history of terrazzo can be traced back to the ancient
mosaic A mosaic () is a pattern or image made of small regular or irregular pieces of colored stone, glass or ceramic, held in place by plaster/Mortar (masonry), mortar, and covering a surface. Mosaics are often used as floor and wall decoration, and ...
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'' ( 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. Until then it was hand polished with a long handled tool called a ''galera''. 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. 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 Art Deco, short for the French (), is a style of visual arts, architecture, and product design that first Art Deco in Paris, appeared in Paris in the 1910s just before World War I and flourished in the United States and Europe during the 1920 ...
and Moderne styles from the 1920s to 1940s favored terrazzo with the dividers allowing for straight or curved lines that increased the decorative potential. 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. One of the best-known examples of terrazzo is the
Hollywood Walk of Fame The Hollywood Walk of Fame is a landmark which consists of 2,813 five-pointed terrazzo-and-brass stars embedded in the sidewalks along 15 blocks of Hollywood Boulevard and three blocks of Vine Street in the Hollywood, Los Angeles, Hollywood dist ...
. Created in 1958, the walk honors celebrities in the form of a terrazzo star that displays their name.


Archaeological use of the term

Archaeologists have adopted the term ''terrazzo'' to describe the floors of early
Neolithic The Neolithic or New Stone Age (from Ancient Greek, Greek 'new' and 'stone') is an archaeological period, the final division of the Stone Age in Mesopotamia, Asia, Europe and Africa (c. 10,000 BCE to c. 2,000 BCE). It saw the Neolithic Revo ...
buildings ( PPNA and PPNB, ca. 9,000–8,000 BC) in
Western Asia West Asia (also called Western Asia or Southwest Asia) is the westernmost region of Asia. As defined by most academics, UN bodies and other institutions, the subregion consists of Anatolia, the Arabian Peninsula, Iran, Mesopotamia, the Armenian ...
constructed of burnt lime and clay, colored red with
ochre Ochre ( ; , ), iron ochre, or ocher in American English, is a natural clay earth pigment, a mixture of ferric oxide and varying amounts of clay and sand. It ranges in colour from yellow to deep orange or brown. It is also the name of the colou ...
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. In the early Neolithic settlement of Çayönü in eastern
Turkey Turkey, officially the Republic of Türkiye, is a country mainly located in Anatolia in West Asia, with a relatively small part called East Thrace in Southeast Europe. It borders the Black Sea to the north; Georgia (country), Georgia, Armen ...
about of terrazzo floors have been uncovered. The floors of the PPN B settlement of Nevalı Çori measure about . They are 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. Recent experiments by Affonso and Pernicka 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,
Jericho Jericho ( ; , ) is a city in the West Bank, Palestine, and the capital of the Jericho Governorate. Jericho is located in the Jordan Valley, with the Jordan River to the east and Jerusalem to the west. It had a population of 20,907 in 2017. F ...
, and Kastros (
Cyprus Cyprus (), officially the Republic of Cyprus, is an island country in the eastern Mediterranean Sea. Situated in West Asia, its cultural identity and geopolitical orientation are overwhelmingly Southeast European. Cyprus is the List of isl ...
).


Production

Terrazzo artisans create walls, floors, patios, and panels by exposing marble chips and other fine aggregates on the surface of finished
concrete Concrete is a composite material composed of aggregate bound together with a fluid cement that cures to a solid over time. It is the second-most-used substance (after water), the most–widely used building material, and the most-manufactur ...
or
epoxy Epoxy is the family of basic components or Curing (chemistry), cured end products of epoxy Resin, resins. Epoxy resins, also known as polyepoxides, are a class of reactive prepolymers and polymers which contain epoxide groups. The epoxide fun ...
-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 deep. After the forms are removed from the foundation, workers add a 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 () over the entire surface. In the 1970s,
polymer A polymer () is a chemical substance, substance or material that consists of very large molecules, or macromolecules, that are constituted by many repeat unit, repeating subunits derived from one or more species of monomers. Due to their br ...
-based terrazzo was introduced and is called thin-set terrazzo. Initially polyester and 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, 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 Abalone ( or ; via Spanish , from Rumsen language, Rumsen ''aulón'') is a common name for any small to very large marine life, marine gastropod mollusc in the family (biology), family Haliotidae, which once contained six genera but now cont ...
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 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- troweled for a smooth, uniform surface; it is then cleaned, polished, and sealed.


Types and systems

Terrazzo installation includes both bonded and unbonded methods. Bonded systems include: bonded underbed, monolithic, chemically bonded, and the most recent, thin set method (
epoxy Epoxy is the family of basic components or Curing (chemistry), cured end products of epoxy Resin, resins. Epoxy resins, also known as polyepoxides, are a class of reactive prepolymers and polymers which contain epoxide groups. The epoxide fun ...
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. Unbonded includes the sand cushion method which uses wire reinforcing, an isolation sheet, and sand dusting that absorbs any movement from the concrete slab.


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 In chemistry, an alkali (; from the Arabic word , ) is a basic salt of an alkali metal or an alkaline earth metal. An alkali can also be defined as a base that dissolves in water. A solution of a soluble base has a pH greater than 7.0. The a ...
s or
acid An acid is a molecule or ion capable of either donating a proton (i.e. Hydron, hydrogen cation, H+), known as a Brønsted–Lowry acid–base theory, Brønsted–Lowry acid, or forming a covalent bond with an electron pair, known as a Lewis ...
s can deteriorate the bonding agents used in terrazzo. As the aggregates are often marble dust which is
calcium carbonate Calcium carbonate is a chemical compound with the chemical formula . It is a common substance found in Rock (geology), rocks as the minerals calcite and aragonite, most notably in chalk and limestone, eggshells, gastropod shells, shellfish skel ...
, 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. Aged terrazzo can be resurfaced to restore its original look by re-polishing.


See also

* Engineered stone *
Mosaic A mosaic () is a pattern or image made of small regular or irregular pieces of colored stone, glass or ceramic, held in place by plaster/Mortar (masonry), mortar, and covering a surface. Mosaics are often used as floor and wall decoration, and ...
* Polished concrete * Portuguese pavement


References


External links

* {{Authority control Decorative arts Floors Pre-Pottery Neolithic