Pozzolanic ash is an alumino-siliceous material which reacts with calcium hydroxide in the presence of water to form compounds possessing cementitious properties at room temperature, producing C-S-H. This allowed it to be used in the Roman Empire to make cement by combining with lime and water. Pozzolanic ash occurs naturally in volcanic deposits from Pozzuoli and Naples. See also pozzolana. Aluminum is a soft and lightweight metal with a dull silvery appearance, due to a thin layer of oxidation that forms quickly when it is exposed to air. ... General Name, Symbol, Number silicon, Si, 14 Chemical series metalloids Group, Period, Block 14, 3, p Appearance dark gray, bluish tinge Atomic mass 28. ... Calcium hydroxide Calcium hydroxide is a chemical compound with the chemical formula Ca(OH)2. ... sabki maaa ki chooot !! In the general sense, a cement is any material with adhesive properties. ... The Roman Empire is the term conventionally used to describe the Ancient Roman polity in the centuries following its reorganization under the leadership of Octavian (better known as Caesar Augustus), until its radical reformation in what was later to be known as the Byzantine Empire. ... Puteoli, the ancient predecessor of Pozzuoli, was an Italian city of Roman times on the coast of Campania, on the north shore of a bay running north from the Bay of Naples. ... Naples (Italian Napoli, Neapolitan Napule, from Greek Νέα Πόλις - Néa Pólis - meaning New City; see also List of traditional Greek place names) is the largest city in southern Italy and capital of Campania Region and the Province of Naples. ... Pozzolana is a fine sandy volcanic ash, originally discovered and dug at Pozzuoli in the region around Vesuvius, but later at a number of other sites. ...

Today, pozzolanic ash can also be obtained from industrial waste products and used as a replacement for Portland cement in concrete. Some industrial sources of pozzolanic ash are: Class F fly ash from coal fired power plants, silica fume from silicon production, rice husk ash from rice-padi fields (agriculture), and metakaolin from oil sands operations. Metakaolin, a powerful pozzolan, can also be manufactured (from kaolinite clays), and is valued for improving white concrete.

Pozzolanic substances react with C-H in the cement paste, converting it to C-S-H and resulting in increased concrete strength. Most pozzolans, with the exception of fly ash, result in high early strength in concrete, but reduced workability and high heat of hydration. This necessitates the use of superplasticizer and chilled water when mixing such admixtures into concrete. Class F fly ash, however, results in low early strength but reduced heat of hydration and improved workability. One optimal solution for "green concrete" is to use both fly ash as well as silica fume at the same time, though this requires careful mix proportioning. Pozzolana is a fine sandy volcanic ash, originally discovered and dug at Pozzuoli in the region around Vesuvius, but later at a number of other sites. ... It has been suggested that this article or section be merged with Plasticizer. ...

Other industrial waste products used for partial cement replacement include Class C fly ash and blast furnace slag. However, these substances are not pozzolanic, and should not be mistaken as such. Blast furnace diagram A blast furnace is a type of furnace for smelting whereby the combustion material and ore are supplied with air from the bottom of the chamber such that the chemical reaction does not take place only at the surface. ... For the Transformers character, see Slag (Transformer). ...

See also

Pozzolana Pozzolana is a fine sandy volcanic ash, originally discovered and dug at Pozzuoli in the region around Vesuvius, but later at a number of other sites. ...