A pozzolan is a material which, when combined with calcium hydroxide, exhibits cementitious properties. Pozzolans are commonly used as an addition to Portland cement to increase the long-term strength and other material properties. Pozzolans are primarily vitreous siliceous materials which react slowly with calcium hydroxide to form calcium silicates; other cementitious materials may be formed depending on the constituents of the pozzolan. The pozzolanic reaction is slower than the rest of the reactions which occur during cement hydration, and thus the short-term strength of concrete made with pozzolans may not be as high as concrete made with purely cementitious materials. Calcium hydroxide is a chemical compound with the chemical formula Ca(OH)2. ... Cement is a material used for bonding other materials together, and as a binder in concrete. ... Sampling fast set Portland cement Portland cement is the most common type of cement in general usage, as it is a basic ingredient of concrete, mortar and plaster. ... Vitreous refers to a material in a glassy state. ... Mineral hydration is an inorganic chemical reaction where water is added to the crystal structure of a mineral, usually creating a new mineral. ... The most common form of concrete consists of Portland cement, construction aggregate (generally gravel and sand) and water. ...
The first known pozzolan was pozzolana, a volcanic ash, for which the category of materials was named. The most commonly-used pozzolan today is fly ash, though silica fume, ground granulated blast furnace slag and other materials are also used as pozzolans. 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. ... Background Fly ash is the finely divided mineral residue resulting from the combustion of powdered coal in electric generating plants. ... Silica fume, also known as microsilica, is a byproduct of the reduction of high-purity quartz with coal in electric furnaces in the production of silicon and ferrosilicon alloys. ... Ground granulated blastfurnace slag (GGBS or GGBFS) is obtained by quenching molten iron blast furnace slag (a by-product of iron and steel making) in water or stream, to produce a glassy granular product that is then dried and ground into a fine powder. ...
A Pozzolan is a finely-divided material that reacts with calcium hydroxide and alkalies to form compounds possessing cementitious properties.
Pozzolans are present on earth's surface such as diatomaceous earth, volcanic ash, opaline shale, pumicite, and tuff.
Natural pozzolans have been used in dams and bridges to lower the heat of hydration and increase resistance of concrete to sulfate attack and control the alkali-silica reaction.
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