Pozzolana


Pozzolana

Pozzolana, also known as pozzolanic ash, is a fine, sandy volcanic ash, originally discovered and dug in Italy at Pozzuoli in the region around Vesuvius, but later at a number of other sites. Vitruvius speaks of four types of pozzolana: black, white, grey, red. It is found in all the volcanic areas of Italy, such as Naples, in various colours: black, white, grey and red.

Pozzolana is a siliceous and aluminous material which reacts with calcium hydroxide in the presence of water to form compounds possessing cementitious properties at room temperature and that have the ability to set under water. It transformed the possibilities for making concrete structures, although it took the Romans some time to discover its full potential. Typically it was mixed two-to-one with lime just prior to mixing with water. The Roman port at Cosa was built of Pozzolana that was poured underwater, apparently using a long tube to carefully lay it up without allowing sea water to mix with it. The three piers are still visible today, with the underwater portions in generally excellent condition after 2100 years.

Modern pozzolanic cements are a mix of natural or industrial pozzolans and Portland cement. In addition to underwater use, the high alkalinity of pozzolana makes it especially resistant to common forms of corrosion from sulfates. Once fully hardened, the Portland cement-Pozzolana blend may be stronger than Portland cement, due to its lower porosity, which also makes it more resistant to water absorption and spalling.

Some industrial sources of materials with pozzolanic properties are: Class F (silicious) fly ash from coal-fired power plants, silica fume from silicon production, rice husk ash from rice paddy-fields (agriculture), and metakaolin from oil sand operations. Metakaolin, a powerful pozzolan, can also be manufactured, and is valued for making white concrete.

Other industrial waste products used in Portland composite cements include Class C (calcareous) fly ash and ground granulated blast furnace slag.

ee also

*Aerated autoclaved concrete
*Cenospheres

References

*McCann, A.M. (1994). "The Roman Port of Cosa",(273 BC), "Scientific American, Ancient Cities", pp. 92–99, by Anna Marguerite McCann. Covers, "hydraulic concrete, of "Pozzolana mortar" and the "5 piers, of the Cosa harbor, the Lighthouse on pier 5," diagrams, and photographs. Height of Port city: 100 BC.


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Look at other dictionaries:

  • pozzolana — /pot seuh lah neuh/; It. /pawt tsaw lah nah/, n. a porous variety of volcanic tuff or ash used in making hydraulic cement. Also, pozzolan /pot seuh leuhn/, pozzuolana /pot sweuh lah neuh/; It. /pawt tswaw lah nah/, puzzolan, puzzolana. [1905 10;… …   Universalium

  • Pozzolana — Pozzuolana Poz zu*o*la na, Pozzolana Poz zo*la *na, n. [It.] Volcanic ashes from Pozzuoli, in Italy, used in the manufacture of a kind of mortar which hardens under water. [1913 Webster] …   The Collaborative International Dictionary of English

  • pozzolana — or pozzolan noun Etymology: Italian pozzolana Date: circa 1706 finely divided siliceous or siliceous and aluminous material that reacts chemically with slaked lime at ordinary temperature and in the presence of moisture to form a strong slow… …   New Collegiate Dictionary

  • pozzolana — 1poz·zo·là·na s.f. TS mar. piccola imbarcazione usata nel Napoletano per la pesca con le nasse e i tramagli; anche agg.: barca pozzolana {{line}} {{/line}} DATA: 1937. ETIMO: der. del lat. Puteolanus, der. di Puteoli, nome di una località in… …   Dizionario italiano

  • pozzolana — noun A type of volcanic ash used for mortar or for cement which sets under water. See Also: pozzolan, pozzolanic …   Wiktionary

  • pozzolana — {{hw}}{{pozzolana}}{{/hw}}s. f.  (pl. pozzolane ) (geol.) Tufo recente, poco cementato, di colore grigio o rossastro, usato per far malte idrauliche …   Enciclopedia di italiano

  • pozzolana — pozzolana1 pl.f. pozzolane pozzolana2 pl.f. pozzolane …   Dizionario dei sinonimi e contrari

  • pozzolana — [ˌpɒtsə lα:nə] noun a type of volcanic ash used for mortar or for cement that sets under water. Origin C18: from Ital., from pozz(u)olana (earth) of Pozzuoli , a town near Naples …   English new terms dictionary

  • pozzolana — poz·zo·la·na …   English syllables

  • pozzolana — n. (also puzzolana) a volcanic ash used for mortar or hydraulic cement. Etymology: It., f. pozz(u)olano (adj.) of Pozzuoli near Naples …   Useful english dictionary


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