digplanet beta 1: Athena
Share digplanet:

Agriculture

Applied sciences

Arts

Belief

Business

Chronology

Culture

Education

Environment

Geography

Health

History

Humanities

Language

Law

Life

Mathematics

Nature

People

Politics

Science

Society

Technology

Pozzolana, also known as pozzolanic ash (pulvis puteolanus in Latin), is a siliceous or siliceous and aluminous material which reacts with calcium hydroxide in the presence of water at room temperature (cf. pozzolanic reaction). 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. Nowadays the definition of pozzolana encompasses any volcanic material (pumice or volcanic ash), 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.

Historical use[edit]

Pozzolanas such as Santorin earth were used in the Eastern Mediterranean since 500–400 BC. Although pioneered by the ancient Greeks, it was the Romans that eventually fully developed the potential of lime-pozzolan pastes as binder phase in Roman concrete used for buildings and underwater construction. Vitruvius speaks of four types of pozzolana: black, white, grey, and red, all of which can be found in the volcanic areas of Italy, such as Naples. Typically it was very thoroughly mixed two-to-one with lime just prior to mixing with water. The Roman port at Cosa was built of pozzolana-lime concrete 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 even after more than 2100 years.

Geochemistry and mineralogy[edit]

The major pozzolanically active component of volcanic pumices and ashes is a highly porous glass.[1] The easily alterable, or highly reactive, nature of these ashes and pumices limits their occurrence largely to recently active volcanic areas. Most of the traditionally used natural pozzolans belong to this group, i.e., volcanic pumice from Pozzuoli, Santorin earth and the incoherent parts of German trass.

The chemical composition of pozzolana is variable and reflects the regional type of volcanism. SiO2 being the major chemical component, most unaltered pumices and ashes fall in the intermediate (52–66 wt% SiO2) to acid (>66 wt% SiO2) composition range for glassy rock types outlined by the IUGS. Basic (45–52 wt% SiO2) and ultrabasic (<45 wt% SiO2) pyroclastics are less commonly used as pozzolans. Al2O3 is present in substantial amounts in most pozzolanas, Fe2O3 and MgO are present in minor proportions only, as is typical or more acid rock types. CaO and alkali contents are usually modest but can vary substantially from pozzolana to pozzolana.

The mineralogical composition of unaltered pyroclastic rocks is mainly determined by the presence of phenocrysts and the chemical composition of the parent magma. The major component is volcanic glass typically present in quantities over 50 wt%. Pozzolana containing significantly less volcanic glass, such as a trachyandesite from Volvic (France) with only 25 wt% are less reactive.[2] Apart from the glass content and its morphology associated with the specific surface area, also defects and the degree of strain in the glass appear to affect the pozzolanic activity.[3] Typical associated minerals present as large phenocrysts are members of the plagioclase feldspar solid solution series. In pyroclastic rocks in which alkalis predominate over Ca, K-feldspar such as sanidine or albite Na-feldspar are found. Leucite is present in the K-rich, silica-poor Latium pozzolanas. Quartz is usually present in minor quantities in acidic pozzolanas, while pyroxenes and/or olivine phenocrysts are often found in more basic materials. Xenocrysts or rock fragments incorporated during the violent eruptional and depositional events are also encountered. Zeolite, opal CT and clay minerals are often present in minor quantities as alteration products of the volcanic glass. While zeolitisation or formation of opal CT is in general beneficial for the pozzolanic activity, clay formation has adverse effects on the performance of lime-pozzolan blends or blended cements.

Modern use[edit]

Pozzolana is abundant in certain locations and is extensively used as an addition to Portland cement in countries such as Italy, Germany, Turkey, China and Greece. Compared to industrial by-product pozzolans they are characterized by larger ranges in composition and a larger variability in physical properties. The application of pozzolana in Portland cement is mainly controlled by the local availability of suitable deposits and the competition with the accessible industrial by-product supplementary cementitious materials. In part due to the exhaustion of the latter sources and the extensive reserves of pozzolana available, partly because of the proven technical advantages of an intelligent use of pozzolana, their use is expected to be strongly expanded in the future.[4]

Pozzolanic reaction[edit]

Main article: Pozzolanic reaction

The pozzolanic reaction is the chemical reaction that occurs in portland cement containing pozzolans. It is the main reaction involved in the Roman concrete invented in Ancient Rome and used to build, for example, the Pantheon.

At the basis of the pozzolanic reaction stands a simple acid-base reaction between calcium hydroxide, also known as Portlandite, or (Ca(OH)2), and silicic acid (H4SiO4, or Si(OH)4). Simply, this reaction can be schematically represented as follows:

Ca(OH)2 + H4SiO4 → Ca2+ + H2SiO42- + 2 H2O → CaH2SiO4 · 2 H2O

or summarized in abbreviated notation of cement chemists:

CH + SH → C-S-H

The product of general formula (CaH2SiO4 · 2 H2O ) formed is a calcium silicate hydrate, also abbreviated as C-S-H in cement chemist notation, the hyphenation denotes the variable stoichiometry. The ratio Ca/Si, or C/S, and the number of water molecules can vary and the above mentioned stoichiometry may differ.

Many pozzolans contain aluminate, or Al(OH)4-, that will react with calcium hydroxide and water to form calcium aluminate hydrates such as C4AH13, C3AH6 or hydrogarnet, or in combination with silica C2ASH8 or strätlingite (cement chemist notation). In the presence of anionic groups such as sulphate, carbonate or chlorine, AFm phases and AFt or ettringite phases can form.

See also[edit]

References[edit]

  1. ^ Ludwig, U.; Schwiete H.E. (1963). "Lime combination and new formations in the trass-lime reactions". Zement-Kalk-Gips 10: 421–431. 
  2. ^ Mortureux, B.; Hornain H.; Gautier E.; Regourd M. "Comparison of the reactivity of different pozzolans". Proceedings of the 7th International Congress on the Chemistry of Cement IV: 110–115. 
  3. ^ Mehta, P.K: (1981). "Studies on blended Portland cements containing Santorin earth". Cement and Concrete Research 11: 507–518. doi:10.1016/0008-8846(81)90080-6. 
  4. ^ Damtoft, J.S.; Lukasik J., Herfort D., Sorrentino D. Gartner E.M. (2008). "Sustainable development and climate change iniatives". Cement and Concrete Research 38: 115–127. doi:10.1016/j.cemconres.2007.09.008. 
  • Cook D.J. (1986) Natural pozzolanas. In: Swamy R.N., Editor (1986) Cement Replacement Materials, Surrey University Press, p. 200.
  • Lechtman H. and Hobbs L. (1986) "Roman Concrete and the Roman Architectural Revolution", Ceramics and Civilization Volume 3: High Technology Ceramics: Past, Present, Future, edited by W.D. Kingery and published by the American Ceramics Society, 1986; and Vitruvius, Book II:v,1; Book V:xii2.
  • 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.
  • Mertens, G.; R. Snellings; K. Van Balen; B. Bicer-Simsir; P. Verlooy; J. Elsen (2009). "Pozzolanic reactions of common natural zeolites with lime and parameters affecting their reactivity". Cement and Concrete Research 39 (3): 233–240. doi:10.1016/j.cemconres.2008.11.008. ISSN 0008-8846. Retrieved 2009-03-23. 


See also[edit]

References[edit]

  • Cook D.J. (1986) Natural pozzolanas. In: Swamy R.N., Editor (1986) Cement Replacement Materials, Surrey University Press, p. 200.
  • 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.
  • Snellings R., Mertens G., Elsen J. (2012) Supplementary cementitious materials. Reviews in Mineralogy and Geochemistry 74:211–278.

Original courtesy of Wikipedia: http://en.wikipedia.org/wiki/Pozzolana — Please support Wikipedia.
This page uses Creative Commons Licensed content from Wikipedia. A portion of the proceeds from advertising on Digplanet goes to supporting Wikipedia.
30830 videos foundNext > 

pozzolana e basalto; architettura e strade dell'antica Roma

Le eruzioni dei vulcani Sabatino e Albano vicino Roma hanno creato strati di cenere vulcanica (pozzolana) che gli antichi romani hanno utilizzato per edifica...

pozzolana

XCENTRIC RIPPER XR35 MAGLIANO SABINO - CAVE DI LAPILLO - POZZOLANA

IL RIPPER E MONTATO SU UN ESCAVATORE CASE, IL RIPPER è STATAO UTILIZZATO PER IL DISGAGGIO DI BLOCCHI DI POZZOLANA DA MACINARE SUCCESSIVAMENTE. PER ULTERIORI ...

mobile crashing pozzolana crushing process

More details: http://www.setpowerpointfree.com/contact/ Get the price of mobile crashing pozzolana crushing process: http://www.setpowerpointfree.com/contact/ CME as one of the largest...

Cost Of Pozzolana Cement Plant Equipment, process crusher

More details:http://goo.gl/Pajuu7 (Get Price!) More About Cost Of Pozzolana Cement Plant Equipment, process crusher, Please Visit:http://goo.gl/9Sn3fe (Conta...

CAVA LAPILLO E POZZOLANA snc SUTRI (VITERBO)

CAVA LAPILLO E POZZOLANA snc http://www.paginegialle.it/cavalapillo v. Di Monte Topino Tel 0761 600607, 0761 608101 Fax 0761 600126 Cava Lapillo e Pozzolana ...

cost of pozzolana cement plant equipment

More details: http://www.stonemining.net/contact/ Get the price of cost of pozzolana cement plant equipment: http://www.stonemining.net/contact/ Zenith as on...

cost of pozzolana cement plant equipment

More details:http://goo.gl/Pajuu7 More About cost of pozzolana cement plant equipment, Please Visit:http://goo.gl/Pajuu7 cost of pozzolana cement plant equip...

La coltivazione artificiale dei funghi nelle Cave di Pozzolana a Roma.

Giornale Luce B0594 del 12/1934 Descrizione sequenze:entrate delle grotte di Pozzolana a Roma con un uomo che trascina un asino che traina un carro con della...

pozzolana grinding mill supply and for sale in uae

pozzolana grinding mill supply and for sale in uae, Links: ▻ http://goo.gl/dii9h4 More details ▻: http://goo.gl/n1nfwu ▻ (Hot!!!) Zenith is quite experienced...

30830 videos foundNext > 

16 news items

 
GhanaWeb
Sat, 26 Jul 2014 04:03:45 -0700

Support for the use of pozzolana cement in the construction of both public and private housing units; …We will promote well-structured and integrated urban development as follows: Upgrade low-income residential structures and depressed residential ...
 
Global Cement
Mon, 21 Jul 2014 20:33:45 -0700

China: Loesche GmbH has completed work on the largest slag mill in the world for Shanxi Taigang Stainless Steel Co (TISCO) in Taiyuan, China achieving a new record product rate of producing 255t/hr blast-furnace slag meal. The Loesche type LM 63.3+3 ...
 
World Cement
Mon, 14 Jul 2014 06:18:45 -0700

... and tree plantation, waste water treatment, as well as an array of community development and social volunteering activities. Most of the cement that Gagal manufactures comprises flyash-based Portland pozzolana cement, which reduces carbon emissions.
 
PR Newswire India (press release)
Mon, 14 Jul 2014 22:48:45 -0700

The components like fly-ash, clinker, gypsum, and slag are inter-grind to manufacture Portland Slag Cement (PSC) and Portland Pozzolana Cement (PPC). This new plant will follow OCL's philosophy of strict quality policy in its products and services ...
 
Vibe Ghana
Fri, 04 Jul 2014 12:08:16 -0700

Dr Atiemo cited burnt bricks and the pozzolana cement and said their lack of commercial production and promotion gave cause to worry. He was speaking at a day's business seminar organized by the CSIR-Technology Development and Transfer Centre to ...

Linkiesta.it

Linkiesta.it
Sun, 13 Jul 2014 23:28:15 -0700

Nei decenni passati, la zona dove sorge il campo nomadi ospitava vecchie discariche e cave di pozzolana riempite di rifiuti. Come se non bastasse, a pochi metri dall'insediamento oggi sorge un deposito Gpl dell'Eni e un'ex area industriale nel cui ...
 
LiberoReporter
Wed, 16 Jul 2014 11:31:33 -0700

I cassonetti non hanno fatto ritorno in quella che è stata, fino a poco tempo fa, l'isola di prossimità indicata dal Comune di Viterbo per i residenti di strada Pian del Cerro, ubicata dopo lo svincolo per la superstrada vicino alla cava di pozzolana ...
 
LiberoReporter
Tue, 15 Jul 2014 01:18:40 -0700

... dell'immondizia nel luogo dove, appunto, l'amministrazione comunale aveva deciso di collocare per la terza volta, sembrando la definitiva, la sfortunata isola ecologica, ovvero dopo l'imbocco per la superstrada, vicino alla cava di pozzolana (vedi ...
Loading

Oops, we seem to be having trouble contacting Twitter

Talk About Pozzolana

You can talk about Pozzolana with people all over the world in our discussions.

Support Wikipedia

A portion of the proceeds from advertising on Digplanet goes to supporting Wikipedia. Please add your support for Wikipedia!