Fly Ash Resource Center

POZZOLAN

Pozzolan is a finely-divided material that reacts with calcium hydroxide and alkalies to form compounds possessing cementitious properties.

More than 2000 years ago, Greeks and Romans built structures that survive today that took advantage of the pozzolan-lime reaction. The Romans used a mixture of lime and pozzolana, a fine volcanic ash, to produce a hydraulic cement (hardening under water). Romans used pozzolana cement from Pozzuoli, Italy near Mt. Vesuvius to build the Appian Way, the Roman baths, the Coliseum and Pantheon in Rome, and the Pont du Gard aqueduct in south France. Vitruvius reported a 2 parts pozzolana to 1 part lime mixture. Animal fat, milk, and blood were used as admixtures (to improve performance.) These structures still exist today!

Ancient Roman Gate
Roman Gate

NATURAL POZZOLAN

Pozzolans are present on earth's surface such as diatomaceous earth, volcanic ash, opaline shale, pumicite, and tuff. These materials require further processing such as calcining, grinding, drying, etc.The Aegean island of Santorini has natural deposits of volcanic ash (Santorin earth.) In the United States, volcanic tuffs and pumicites, diatomaceous earth, and opaline shales are found principally west of the Mississippi River in Oklahoma, Nevada, Arizona, and California. 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. Usually the pozzolanic deposit must be in the vicinity of the project to support mining and processing costs.




Sarychev Volcano erupting on Matua Island (Kuril Islands.) Photo by International Space Station (6-12-09).




Tungurahua Volcano in Abata,Ecuador (Courtesy of AFP/MArtin Bernetti)
 



Mount St. Helens emits plume of steam and ash. Mt. St. Helens: Courtesy U.S. Geol. Survey-Cascades Volcano Obs.

Popocatepetal Volcano in Mexico-volcanic ash. Popocatepetal Volcano

Cascades Volcano Observatory (Courtesy U.S. Geological Survey) Mt. St. Helens. Coutsesy U.S. Geol Survey
 
 
 

The City of Los Angeles Aqueduct (1910-1912)is comprised of portland cement and a natural pozzolan( a Rhyolite pumicite.) The Bonneville dam (1935) used portland natural pozzolan cement. The piers of the San Francisco-Oakland Bay Bridge have natural pozzolan containing concrete (1935.)
 
 

ARTIFICIAL POZZOLAN

Fly ash is an artificial pozzolan produced when pulverized coal is burned in electric power plants. The glassy (amorphous) spherical particulates are the active pozzolanic portion of fly ash. Fly ash is 66-68% glass. Class F fly ash (see ASTM C 618) readily reacts with lime (produced when portland cement hydrates) and alkalies to form cementitious compounds. Class C fly ash also may exhibit hydraulic (self-cementing) properties. Hungry Horse, Canyon Ferry, Palisades, Yellowtail dams all contain portland cement-fly ash concrete.


Power plant (Courtesy of Korean Electric Power Co. KEPCO)


Fly Ash  (Courtesy of U. of Québec)

A pozzolan requires the presence of a reactive alumino silicate glass. These glassy particulates must be fine enough to provide a sufficient reactive surface area for the solid-state chemical reactions. This reactive glass reacts with available calcium hydroxide and alkalies to produce cementitious compounds calcium-silicate hydrate gel and calcium-alumino silicates, etc.)
 

Bear River Zeolite in Idaho

Lassenite SR Pozzolan (Northern California, See Western Pozzolan

MetaKaolin Pozzolan,

Lava S.A Pozzolanic Rock Milos Greece see LAVA

Pagan Island Pozzolan Northern Mariana Islands see here.

Pyramids have Pozzolan?
 

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