Pozzolana
![](http://upload.wikimedia.org/wikipedia/commons/thumb/6/6d/Puzzolane_stones_from_Vesuvius_Italy.jpg/220px-Puzzolane_stones_from_Vesuvius_Italy.jpg)
Pozzolana or pozzuolana (
Historical use
Pozzolanas such as
Geochemistry and mineralogy
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
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
Modern use
Pozzolana is abundant in certain locations and is extensively used as an addition to Portland cement in countries such as Italy, Germany, Kenya, Uganda,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.[5]
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. At the basis of the pozzolanic reaction stands a simple acid-base reaction between calcium hydroxide (as Portlandite) and silicic acid.
See also
- Ancient Roman use as underwater cement
- Caesarea Maritima, the Herodian port
- Ostia Antica, the Trajanic port
- Calcium silicate hydrate (CSH)
- Cement
- Cement chemist notation
- Concrete
- Energetically modified cement (EMC)
- Fly ash
- Metakaolin
- Portland cement
- Pozzolan
- Pozzolanic reaction(main page)
- Pumice
- Rice hull ash
- Roman concrete
- Silica fume
References
- ^ Ludwig, U.; Schwiete H.E. (1963). "Lime combination and new formations in the trass-lime reactions". Zement-Kalk-Gips. 10: 421–431.
- ^ 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.
- .
- ^ "Na-Feldspar mineral".
- .
- 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.