Information AboutPozzolana |
| CATEGORIES ABOUT POZZOLANA | |
| volcanology | |
| concrete | |
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Finely ground and mixed with Lime it acts like Portland Cement and makes a strong Mortar that will also 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. Pozzolan 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, producing CSH. 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. Modern pozzolans are actually a mix of pozzolana and Portland, more correctly known as Portland Cement-Pozzolan. In addition to underwater use, pozzolan's high acidity makes it especially resistant to common forms of Corrosion from Sulphate s. Once fully set, Portland-Pozzolana (pozzolanic cement) is stronger than Portland alone due to it being less porous, which also makes it more resistant to water leakage and Spalling . Some industrial sources of pozzolan are: Class F fly ash from coal fired power plants, silica fume from silicon production, rice husk ash from rice-padi fields (agriculture), metakaolin from oil sands operations. Metakaolin, a powerful pozzolan, can also be manufactured, and is valued for making white concrete. Other industrial waste products used for cement replacement include Class C fly ash and blast furnace slag. However, these substances are not pozzolanic, and should not be mistaken as such. See also Pozzolanic Ash REFERENCES
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