Roman concrete

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The Pantheon in Rome is an example of Roman concrete construction. Rome-Pantheon-Interieur1.jpg
The Pantheon in Rome is an example of Roman concrete construction.
Caesarea harbour: an example of underwater Roman concrete technology on a large scale Caesarea Concrete Bath.jpg
Caesarea harbour: an example of underwater Roman concrete technology on a large scale

Roman concrete, also called opus caementicium, was used in construction in ancient Rome. Like its modern equivalent, Roman concrete was based on a hydraulic-setting cement added to an aggregate.

Contents

Many buildings and structures still standing today, such as bridges, reservoirs and aqueducts, were built with this material, which attests to both its versatility and its durability. Its strength was sometimes enhanced by the incorporation of pozzolanic ash where available (particularly in the Bay of Naples). The addition of ash prevented cracks from spreading. Recent research has shown that the incorporation of mixtures of different types of lime, forming conglomerate "clasts" allowed the concrete to self-repair cracks. [1]

Roman concrete was in widespread use from about 150 BC; [2] some scholars believe it was developed a century before that. [3]

It was often used in combination with facings and other supports, [4] and interiors were further decorated by stucco, fresco paintings, or coloured marble. Further innovative developments in the material, part of the so-called concrete revolution, contributed to structurally complicated forms. The most prominent example of these is the Pantheon dome, the world's largest and oldest unreinforced concrete dome. [5]

Roman concrete differs from modern concrete in that the aggregates often included larger components; hence, it was laid rather than poured. [6] Roman concretes, like any hydraulic concrete, were usually able to set underwater, which was useful for bridges and other waterside construction.

Historic references

The so-called "Temple of Mercury" in Baiae, a Roman frigidarium pool of a bathhouse built in the 1st century BC containing the oldest surviving concrete dome, and largest one before the Pantheon. Baia-Tempio di Mercurio.jpg
The so-called "Temple of Mercury" in Baiae, a Roman frigidarium pool of a bathhouse built in the 1st century BC containing the oldest surviving concrete dome, and largest one before the Pantheon.

Vitruvius, writing around 25 BC in his Ten Books on Architecture, distinguished types of materials appropriate for the preparation of lime mortars. For structural mortars, he recommended pozzolana (pulvis puteolanus in Latin), the volcanic sand from the beds of Pozzuoli, which are brownish-yellow-gray in colour in that area around Naples, and reddish-brown near Rome. Vitruvius specifies a ratio of 1 part lime to 3 parts pozzolana for mortar used in buildings and a 1:2 ratio for underwater work. [10] [11]

The Romans first used hydraulic concrete in coastal underwater structures, probably in the harbours around Baiae before the end of the 2nd century BC. [12] The harbour of Caesarea is an example (22-15 BC) of the use of underwater Roman concrete technology on a large scale, [10] for which enormous quantities of pozzolana were imported from Puteoli. [13]

For rebuilding Rome after the fire in 64 AD which destroyed large portions of the city, Nero's new building code largely called for brick-faced concrete.[ citation needed ] This appears to have encouraged the development of the brick and concrete industries. [10]

Example of opus caementicium on a tomb on the ancient Appian Way in Rome. The original covering has been removed. OpusCaementiciumViaAppiaAntica.jpg
Example of opus caementicium on a tomb on the ancient Appian Way in Rome. The original covering has been removed.

Material properties

Roman concrete, like any concrete, consists of an aggregate and hydraulic mortar, a binder mixed with water that hardens over time. The composition of the aggregate varied, and included pieces of rock, ceramic tile, lime clasts, and brick rubble from the remains of previously demolished buildings. In Rome, readily available tuff was often used as an aggregate. [14]

Gypsum and quicklime were used as binders. [2] Volcanic dusts, called pozzolana or "pit sand", were favoured where they could be obtained. Pozzolana makes the concrete more resistant to salt water than modern-day concrete. [15] Pozzolanic mortar had a high content of alumina and silica.

Recent research (2023) found that lime clasts, previously considered a sign of poor aggregation technique, react with water seeping into any cracks. This produces reactive calcium, which allows new calcium carbonate crystals to form and reseal the cracks. [16] These lime clasts have a brittle structure that was most likely created in a "hot-mixing" technique with quicklime rather than traditional slaked lime, causing cracks to preferentially move through the lime clasts, thus potentially playing a critical role in the self-healing mechanism. [1]

Concrete and, in particular, the hydraulic mortar responsible for its cohesion, was a type of structural ceramic whose utility derived largely from its rheological plasticity in the paste state. The setting and hardening of hydraulic cements derived from hydration of materials and the subsequent chemical and physical interaction of these hydration products. This differed from the setting of slaked lime mortars, the most common cements of the pre-Roman world. Once set, Roman concrete exhibited little plasticity, although it retained some resistance to tensile stresses.

Crystal structure of tobermorite: elementary unit cell Torbermorite CSH 3D Crystal Structure RasMol.gif
Crystal structure of tobermorite: elementary unit cell

The setting of pozzolanic cements has much in common with setting of their modern counterpart, Portland cement. The high silica composition of Roman pozzolana cements is very close to that of modern cement to which blast furnace slag, fly ash, or silica fume have been added.

The strength and longevity of Roman 'marine' concrete is understood to benefit from a reaction of seawater with a mixture of volcanic ash and quicklime to create a rare crystal called tobermorite, which may resist fracturing. As seawater percolated within the tiny cracks in the Roman concrete, it reacted with phillipsite naturally found in the volcanic rock and created aluminous tobermorite crystals. The result is a candidate for "the most durable building material in human history". In contrast, modern concrete exposed to saltwater deteriorates within decades. [17] [18] [19]

The Roman concrete at the Tomb of Caecilia Metella is another variation higher in potassium that triggered changes that "reinforce interfacial zones and potentially contribute to improved mechanical performance". [20]

Seismic technology

Another view of the Pantheon in Rome, including the concrete dome Pantheon Rome-The Dome.jpg
Another view of the Pantheon in Rome, including the concrete dome

For an environment as prone to earthquakes as the Italian peninsula, interruptions and internal constructions within walls and domes created discontinuities in the concrete mass. Portions of the building could then shift slightly when there was movement of the earth to accommodate such stresses, enhancing the overall strength of the structure. It was in this sense that bricks and concrete were flexible. It may have been precisely for this reason that, although many buildings sustained serious cracking from a variety of causes, they continue to stand to this day. [21] [10]

Another technology used to improve the strength and stability of concrete was its gradation in domes. One example is the Pantheon, where the aggregate of the upper dome region consists of alternating layers of light tuff and pumice, giving the concrete a density of 1,350 kilograms per cubic metre (84 lb/cu ft). The foundation of the structure used travertine as an aggregate, having a much higher density of 2,200 kilograms per cubic metre (140 lb/cu ft). [22] [10]

Modern use

Scientific studies of Roman concrete since 2010 have attracted both media and industry attention. [23] Because of its unusual durability, longevity and lessened environmental footprint, corporations and municipalities are starting to explore the use of Roman-style concrete in North America. This involves replacing the volcanic ash with coal fly ash that has similar properties. Proponents say that concrete made with fly ash can cost up to 60% less because it requires less cement. It also has a reduced environmental footprint due to its lower cooking temperature and much longer lifespan. [24] Usable examples of Roman concrete exposed to harsh marine environments have been found to be 2000 years old with little or no wear. [25] In 2013, the University of California Berkeley published an article that described for the first time the mechanism by which the suprastable calcium-aluminium-silicate-hydrate compound binds the material together. [26] During its production, less carbon dioxide is released into the atmosphere than any modern concrete production process. [27] It is no coincidence that the walls of Roman buildings are thicker than those of modern buildings. However, Roman concrete was still gaining its strength for several decades after construction had been completed. [17]

See also

Literature

Related Research Articles

<span class="mw-page-title-main">Concrete</span> Composite construction material

Concrete is a composite material composed of aggregate bonded together with a fluid cement that cures over time. Concrete is the second-most-used substance in the world after water, and is the most widely used building material. Its usage worldwide, ton for ton, is twice that of steel, wood, plastics, and aluminium combined.

<span class="mw-page-title-main">Cement</span> Hydraulic binder used in the composition of mortar and concrete

A cement is a binder, a chemical substance used for construction that sets, hardens, and adheres to other materials to bind them together. Cement is seldom used on its own, but rather to bind sand and gravel (aggregate) together. Cement mixed with fine aggregate produces 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.

<span class="mw-page-title-main">Portland cement</span> Binder used as basic ingredient of concrete

Portland cement is the most common type of cement in general use around the world as a basic ingredient of concrete, mortar, stucco, and non-specialty grout. It was developed from other types of hydraulic lime in England in the early 19th century by Joseph Aspdin, and is usually made from limestone. It is a fine powder, produced by heating limestone and clay minerals in a kiln to form clinker, grinding the clinker, and adding 2 to 3 percent of gypsum. Several types of portland cement are available. The most common, called ordinary portland cement (OPC), is grey, but white portland cement is also available. Its name is derived from its resemblance to portland stone which was quarried on the Isle of Portland in Dorset, England. It was named by Joseph Aspdin who obtained a patent for it in 1824. His son William Aspdin is regarded as the inventor of "modern" portland cement due to his developments in the 1840s. The term portland in this context refers to a material or process, not a proper noun like a place or a person, and should not be capitalized.

<span class="mw-page-title-main">Calcium oxide</span> Chemical compound of calcium

Calcium oxide, commonly known as quicklime or burnt lime, is a widely used chemical compound. It is a white, caustic, alkaline, crystalline solid at room temperature. The broadly used term lime connotes calcium-containing inorganic compounds, in which carbonates, oxides, and hydroxides of calcium, silicon, magnesium, aluminium, and iron predominate. By contrast, quicklime specifically applies to the single compound calcium oxide. Calcium oxide that survives processing without reacting in building products, such as cement, is called free lime.

<span class="mw-page-title-main">Mortar (masonry)</span> Workable paste which hardens to bind building blocks

Mortar is a workable paste which hardens to bind building blocks such as stones, bricks, and concrete masonry units, to fill and seal the irregular gaps between them, spread the weight of them evenly, and sometimes to add decorative colors or patterns to masonry walls. In its broadest sense, mortar includes pitch, asphalt, and soft mud or clay, as those used between mud bricks, as well as cement mortar. The word "mortar" comes from Old French mortier, "builder's mortar, plaster; bowl for mixing." (13c.).

<span class="mw-page-title-main">Pozzolana</span> Natural siliceous or siliceous-aluminous material

Pozzolana or pozzuolana, also known as pozzolanic ash, is a natural siliceous or siliceous-aluminous material which reacts with calcium hydroxide in the presence of water at room temperature. In this reaction insoluble calcium silicate hydrate and calcium aluminate hydrate compounds are formed possessing cementitious properties. The designation pozzolana is derived from one of the primary deposits of volcanic ash used by the Romans in Italy, at Pozzuoli. The modern definition of pozzolana encompasses any volcanic material, predominantly composed of fine volcanic glass, that is used as a pozzolan. Note the difference with the term pozzolan, which exerts no bearing on the specific origin of the material, as opposed to pozzolana, which can only be used for pozzolans of volcanic origin, primarily composed of volcanic glass.

<span class="mw-page-title-main">Silica fume</span> Silicon dioxide nano particles

Silica fume, also known as microsilica, is an amorphous (non-crystalline) polymorph of silicon dioxide, silica. It is an ultrafine powder collected as a by-product of the silicon and ferrosilicon alloy production and consists of spherical particles with an average particle diameter of 150 nm. The main field of application is as pozzolanic material for high performance concrete.

<span class="mw-page-title-main">Lime (material)</span> Calcium oxides and/or hydroxides

Lime is an inorganic material composed primarily of calcium oxides and hydroxides, usually calcium oxide and/or calcium hydroxide. It is also the name for calcium oxide which occurs as a product of coal-seam fires and in altered limestone xenoliths in volcanic ejecta. The International Mineralogical Association recognizes lime as a mineral with the chemical formula of CaO. The word lime originates with its earliest use as building mortar and has the sense of sticking or adhering.

<span class="mw-page-title-main">Hydraulic lime</span>

Hydraulic lime (HL) is a general term for calcium oxide, a variety of lime also called quicklime, that sets by hydration. This contrasts with calcium hydroxide, also called slaked lime or air lime that is used to make lime mortar, the other common type of lime mortar, which sets by carbonation (re-absorbing carbon dioxide (CO2) from the air). Hydraulic lime provides a faster initial set and higher compressive strength than air lime, and hydraulic lime will set in more extreme conditions, including under water.

<span class="mw-page-title-main">Phillipsite</span> Minerals in the zeolite group

Phillipsite is a mineral series of the zeolite group; a hydrated potassium, calcium and aluminium silicate, approximating to (Ca,Na2,K2)3Al6Si10O32·12H2O. The members of the series are phillipsite-K, phillipsite-Na and phillipsite-Ca. The crystals are monoclinic, but only complex cruciform twins are known, these being exactly like twins of harmotome which also forms a series with phillipsite-Ca. Crystals of phillipsite are, however, usually smaller and more transparent and glassy than those of harmotome. Spherical groups with a radially fibrous structure and bristled with crystals on the surface are not uncommon. The Mohs hardness is 4.5, and the specific gravity is 2.2. The species was established by Armand Lévy in 1825 and named after William Phillips. French authors use the name Christianite (after Christian VIII of Denmark), given by A. Des Cloizeaux in 1847.

<span class="mw-page-title-main">Lime plaster</span> Type of plaster composed of sand, water, and lime

Lime plaster is a type of plaster composed of sand, water, and lime, usually non-hydraulic hydrated lime. Ancient lime plaster often contained horse hair for reinforcement and pozzolan additives to reduce the working time.

Trass is the local name of a volcanic tuff occurring in the Eifel, where it is worked for hydraulic mortar. It is a grey or cream-coloured fragmental rock, largely composed of pumiceous dust, and may be regarded as a trachytic tuff. It much resembles the Italian pozzolana and is applied to like purposes. Mixed with lime and sand, or with Portland cement, it is extensively employed for hydraulic work, especially in the Netherlands; while the compact varieties have been used as a building material and as a fire-stone in ovens. Trass was formerly worked extensively in the Brohl valley and is now obtained from the valley of the Nette, near Andernach.

<span class="mw-page-title-main">Lime mortar</span> Building material

Lime mortar or torching is a masonry mortar composed of lime and an aggregate such as sand, mixed with water. It is one of the oldest known types of mortar, used in ancient Rome and Greece, when it largely replaced the clay and gypsum mortars common to ancient Egyptian construction.

Metakaolin is the anhydrous calcined form of the clay mineral kaolinite. Minerals that are rich in kaolinite are known as china clay or kaolin, traditionally used in the manufacture of porcelain. The particle size of metakaolin is smaller than cement particles, but not as fine as silica fume.

<span class="mw-page-title-main">Ground granulated blast-furnace slag</span> Granular slag by-product of iron and steel-making used as supplementary cementitious material

Ground granulated blast-furnace slag is obtained by quenching molten iron slag from a blast furnace in water or steam, to produce a glassy, granular product that is then dried and ground into a fine powder. Ground granulated blast furnace slag is a latent hydraulic binder forming calcium silicate hydrates (C-S-H) after contact with water. It is a strength-enhancing compound improving the durability of concrete. It is a component of metallurgic cement. Its main advantage is its slow release of hydration heat, allowing limitation of the temperature increase in massive concrete components and structures during cement setting and concrete curing, or to cast concrete during hot summer.

<span class="mw-page-title-main">Pozzolan</span> Siliceous volcanic ashes commonly used as supplementary cementitious material

Pozzolans are a broad class of siliceous and aluminous materials which, in themselves, possess little or no cementitious value but which will, in finely divided form and in the presence of water, react chemically with calcium hydroxide (Ca(OH)2) at ordinary temperature to form compounds possessing cementitious properties. The quantification of the capacity of a pozzolan to react with calcium hydroxide and water is given by measuring its pozzolanic activity. Pozzolana are naturally occurring pozzolans of volcanic origin.

<span class="mw-page-title-main">Alkali–silica reaction</span> Chemical reaction damaging concrete

The alkali–silica reaction (ASR), also commonly known as concrete cancer, is a deleterious swelling reaction that occurs over time in concrete between the highly alkaline cement paste and the reactive amorphous silica found in many common aggregates, given sufficient moisture.

<span class="mw-page-title-main">Types of concrete</span> Building material consisting of aggregates cemented by a binder

Concrete is produced in a variety of compositions, finishes and performance characteristics to meet a wide range of needs.

The pozzolanic activity is a measure for the degree of reaction over time or the reaction rate between a pozzolan and Ca2+ or calcium hydroxide (Ca(OH)2) in the presence of water. The rate of the pozzolanic reaction is dependent on the intrinsic characteristics of the pozzolan such as the specific surface area, the chemical composition and the active phase content.

<span class="mw-page-title-main">Energetically modified cement</span> Class of cements, mechanically processed to transform reactivity

Energetically modified cements (EMCs) are a class of cements made from pozzolans, silica sand, blast furnace slag, or Portland cement. The term "energetically modified" arises by virtue of the mechanochemistry process applied to the raw material, more accurately classified as "high energy ball milling" (HEBM). At its simplest this means a milling method that invokes high kinetics by subjecting "powders to the repeated action of hitting balls" as compared to (say) the low kinetics of rotating ball mills. This causes, amongst others, a thermodynamic transformation in the material to increase its chemical reactivity. For EMCs, the HEBM process used is a unique form of specialised vibratory milling discovered in Sweden and applied only to cementitious materials, here called "EMC Activation".

References

  1. 1 2 Chandler, David L. (6 January 2023). "Riddle solved: Why was Roman concrete so durable?". MIT News. Archived from the original on 21 January 2023.
  2. 1 2 "National Pozzolan Association: The History of Natural Pozzolans". pozzolan.org. Retrieved 2021-02-21.
  3. ↑ Boëthius, Axel; Ling, Roger; Rasmussen, Tom (1978). "Etruscan and Early Roman Architecture". Yale/Pelican history of art. Yale University Press. pp. 128–129. ISBN   978-0300052909.
  4. ↑ "Aqua Clopedia, a picture dictionary on Roman aqueducts: Roman concrete / opus caementicium". romanaqueducts.info. Retrieved 2023-01-24.
  5. ↑ Moore, David (February 1993). "The Riddle of Ancient Roman Concrete". S Dept. of the Interior, Bureau of Reclamation, Upper Colorado Region. Retrieved 20 May 2013.
  6. ↑ Henig, Martin, ed. (1983). A Handbook of Roman Art. Phaidon. p. 30. ISBN   0714822140.
  7. ↑ "Baiae, historic site, Italy". Encyclopedia Britannica .
  8. ↑ Lancaster 2009, p. 40.
  9. ↑ Mark, Robert; Hutchinson, Paul (March 1986). "On the Structure of the Roman Pantheon". The Art Bulletin. New York, NY: College Art Association. 68 (1): 24. doi:10.2307/3050861. JSTOR   3050861.
  10. 1 2 3 4 5 Lechtman & Hobbs 1986.
  11. ↑ Vitruvius. De Architectura, Book II:v,1; Book V:xii2.
  12. ↑ Oleson et al., 2004, The ROMACONS Project: A Contribution to the Historican and Engineering Analysis of the Hydrauilc Concrete in Roman Maritime Structures, International Journal of Nautical Archaeology 33.2: 199-229
  13. ↑ Hohlfelder, R. 2007. "Constructing the Harbour of Caesarea Palaestina, Israel: New Evidence from ROMACONS Field Campaign of October 2005". International Journal of Nautical Archaeology 36:409-415.
  14. ↑ "Rome's Invisible City". BBC One. Retrieved 6 July 2017.
  15. ↑ Wayman, Erin (16 November 2011). "The Secrets of Ancient Rome's Buildings". Smithsonian.com. Retrieved 24 April 2012.
  16. ↑ Seymour, Linda; et al. (2023). "Hot mixing: Mechanistic insights into the durability of ancient Roman concrete". Science Advances. 9 (1): eadd1602. Bibcode:2023SciA....9D1602S. doi:10.1126/sciadv.add1602. hdl: 1721.1/147056 . PMC   9821858 . PMID   36608117. S2CID   255501528.
  17. 1 2 Guarino, Ben (4 July 2017). "Ancient Romans made world's 'most durable' concrete. We might use it to stop rising seas". The Washington Post .
  18. ↑ Jackson, Marie D.; Mulcahy, Sean R.; Chen, Heng; Li, Yao; Li, Qinfei; Cappelletti, Piergiulio; Wenk, Hans-Rudolf (2017). "Phillipsite and Al-tobermorite mineral cements produced through low-temperature water-rock reactions in Roman marine concrete". American Mineralogist. 102 (7): 1435–1450. Bibcode:2017AmMin.102.1435J. doi: 10.2138/am-2017-5993CCBY . ISSN   0003-004X.
  19. ↑ McGrath, Matt (4 July 2017). "Scientists explain ancient Rome's long-lasting concrete". BBC News. Retrieved 6 July 2017.
  20. ↑ Ouellette, Jennifer (1 January 2022). "Noblewoman's tomb reveals new secrets of ancient Rome's highly durable concrete". Ars Technica . Retrieved 5 January 2022.
  21. ↑ MacDonald 1982, fig. 131B.
  22. ↑ K. de Fine Licht, The Rotunda in Rome: A Study of Hadrian's Pantheon. Jutland Archaeological Society, Copenhagen, 1968, pp. 89–94, 134–35
  23. ↑ "Fixing Canada's Infrastructure with Volcanoes". Trebuchet Capital Partners Research. 15 October 2015. Retrieved 19 August 2016.
  24. ↑ Patrick, Neil (6 September 2016). "By 25 BC, ancient Romans developed a recipe for concrete specifically used for underwater work which is essentially the same formula used today". The Vintage News.
  25. ↑ M. D. Jackson, S. R. Chae, R. Taylor, C. Meral, J. Moon, S. Yoon, P. Li, A. M. Emwas, G. Vola, H.-R. Wenk, and P. J. M. Monteiro, "Unlocking the secrets of Al-tobermorite in Roman seawater concrete", American Mineralogist, Volume 98, pp. 1669–1687, 2013.
  26. ↑ Jackson, Marie D.; Moon, Juhyuk; Gotti, Emanuele; Taylor, Rae; Chae, Sejung R.; Kunz, Martin; Emwas, Abdul-Hamid; Meral, Cagla; Guttmann, Peter; Levitz, Pierre; Wenk, Hans-Rudolf; Monteiro, Paulo J. M. (28 May 2013). "Material and Elastic Properties of Al-Tobermorite in Ancient Roman Seawater Concrete". Journal of the American Ceramic Society. 96 (8): 2598–2606. doi:10.1111/jace.12407 . Retrieved November 4, 2023.
  27. ↑ "Renaissance of Roman Concrete: Cutting carbon emissions". constructionspecifier.com. 29 December 2016. Retrieved June 27, 2022.
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