Pozzolana

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Pozzolana

Pozzolana, also known as pozzolanic ash, is a fine, sandy volcanic ash

Volcanic ash

Volcanic ash consists of small tephra, which are bits of pulverized rock and glass created by volcano eruptions, less than in diameter. There are three mechanisms of volcanic ash formation: gas release under decompression causing magmatic eruptions; thermal contraction from chilling on contact with water causing phreatomagmatic eruptions...
, originally discovered and dug in Italy

Italy

Italy , officially the Italian Republic , is a country located on the Italian Peninsula in Southern Europe and on the two largest islands in the Mediterranean Sea, Sicily and Sardinia....
at Pozzuoli

Pozzuoli

Pozzuoli is a city of the province of Naples, in the Italy region of Campania. It is the main city of the Campi Flegrei....
in the region around Vesuvius, but later at a number of other sites. Vitruvius

Vitruvius

File:Vitruvius.jpgMarcus Vitruvius Pollio was a Ancient Rome writer, architect and engineer , active in the 1st century BC. By his own description Vitruvius served as a Ballista , the third class of arms in the military offices....
speaks of four types of pozzolana: black, white, grey, red.

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Pozzolana, also known as pozzolanic ash, is a fine, sandy volcanic ash

Volcanic ash

Italy

Pozzuoli

Vitruvius

Naples

Naples is a city in southern Italy, the capital of the region of Campania and of the province of Naples. The city is known for its rich history, art, culture and gastronomy, playing an important role throughout much of its existence; it is over 2,800 years old....
, in various colours: black, white, grey and red.

Pozzolana is a siliceous and aluminous

Aluminium oxide

Aluminium oxide is an amphoteric oxide of aluminium with the chemical formula 23. It is also commonly referred to as alumina or aloxite in the mining, ceramic and materials science communities....
material which reacts with calcium hydroxide

Calcium hydroxide

Calcium hydroxide, traditionally called slaked lime, hydrated lime, or pickling lime, is a chemical compound with the chemical formula Calcium2....
in the presence of water to form compounds possessing cement

Cement

In the most general sense of the word, a cement is a binder, a substance which sets and hardens independently, and can bind other materials together....
itious properties at room temperature and that have the ability to set under water. It transformed the possibilities for making concrete

Concrete

Concrete is a construction material composed of cement as well as other cementitious materials such as fly ash and slag cement, construction aggregate , water , and Chemistry admixtures....
structures, although it took the Romans

Ancient Rome

Ancient Rome was a civilization that grew out of a small agricultural community founded on the Italian Peninsula as early as the 10th century BC....
some time to discover its full potential. Typically it was mixed two-to-one with lime

Lime

Lime may refer to:...
just prior to mixing with water. The Roman port at Cosa

Cosa

Cosa was a Latin colonia founded under Ancient Rome influence in southwestern Tuscany in 273 BC, perhaps on land confiscated from the Etruscans ....
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

Pier

A pier is a raised walkway over water, supported by widely spread piles or column. The lighter structure of a pier allows tides and currents to flow almost unhindered, whereas the more solid foundations of a quay or the closely-spaced piles of a wharf can act as breakwaters, and are consequently more liable to silting....
are still visible today, with the underwater portions in generally excellent condition after 2100 years.

Modern pozzolanic cements are a mix of natural or industrial pozzolan

Pozzolan

A pozzolan is a material which, when combined with calcium hydroxide, exhibits cementitious properties. Pozzolans are commonly used as an addition to Portland cement concrete mixtures to increase the long-term strength and other material properties of Portland cement concrete, and in some cases reduce the material cost of concrete....
s and Portland cement

Portland cement

Portland cement is the most common type of cement in general use around the world, because it is a basic ingredient of concrete, mortar , stucco and most non-specialty grout....
. In addition to underwater use, the high alkalinity

Alkalinity

Alkalinity or AT is a measure of the ability of a solution to neutralize acids to the equivalence point of carbonate or bicarbonate....
of pozzolana makes it especially resistant to common forms of corrosion

Corrosion

Corrosion means the breaking down of essential properties in a material due to chemical reactions with its surroundings. In the most common use of the word, this means a loss of electrons of metals reacting with water and oxygen....
from sulfate

Sulfate

In inorganic chemistry, a sulfate is a salt of sulfuric acid....
s. Once fully hardened, the Portland cement-Pozzolana blend may be stronger than Portland cement, due to its lower porosity

Porosity

Porosity is a measure of the void spaces in a material, and is measured as a fraction, between 0?1, or as a percentage between 0?100%. The term is used in multiple fields including ceramics, metallurgy, materials, manufacturing, earth sciences and construction....
, which also makes it more resistant to water absorption and spalling.

Some industrial sources of materials with pozzolanic properties are: Class F (silicious) fly ash

Fly ash

Fly ash is one of the residues generated in the combustion of coal. Fly ash is generally captured from the chimneys of Fossil fuel power plant, and is one of two types of ash that jointly are known as coal ash; the other, bottom ash, is removed from the bottom of coal furnaces....
from coal-fired power plants, silica fume

Silica fume

Silica fume, also known as microsilica, is a fine grain, low density and high surface area silica.It is sometimes confused with fumed silica ....
from silicon

Silicon

Silicon is the most common metalloid. It is a chemical element, which has the symbol Si and atomic number 14. The atomic mass is 28.0855....
production, rice husk ash from rice paddy-fields (agriculture), and metakaolin

Metakaolin

Metakaolin is a hydroxylation form of the clay mineral kaolinite.Rocks that are rich in kaolinite are known as china clay or kaolin, traditionally used in the manufacture of porcelain....
from oil sand operations. Metakaolin, a powerful pozzolan, can also be manufactured, and is valued for making white concrete.

Other industrial waste products used in Portland composite cements include Class C (calcareous) fly ash and ground granulated blast furnace slag

Ground granulated blast furnace slag

Ground granulated blast furnace slag is obtained by quenching molten iron slag from a blast furnace in water or steam, to produce a glassy, granular product that is then dried and ground into a fine powder....
.

Pozzolana

See also