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fly ash[′flī ‚ash]
Fine particulate, essentially noncombustible refuse, carried in a gas stream from a furnace.
Coal combustion residue.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
A fine glass powder recovered from the gases of burning coal during the production of electricity. It is an ash residue from high-temperature combustion processes. Electric motor plants using western coal produce a nontoxic fly ash that because of its very high calcium content can be a substitute for Portland cement, the common bonding material in concrete, and these micron-sized Earth elements consist primarily of silica, alumina, and iron. When mixed with lime and water, fly ash forms a cementitious compound with properties very similar to that of Portland cement. Because of this similarity, fly ash can be used to replace a portion of cement in the concrete, providing some distinct quality advantages. The concrete is denser, resulting in a tighter, smoother surface with less bleeding. Fly ash concrete offers a distinct architectural benefit with improved textural consistency and sharper detail. Regulations vary from state to state; however, ASTM International suggests that fly ash must not contain more than 6 percent unburned carbon to be used for its cementitious qualities. Substitution of fly ash for Portland cement in concrete is considered a sustainable building strategy, as it reduces the amount of energy-intensive (and CO2-producing) cement in the mix.
Illustrated Dictionary of Architecture Copyright © 2012, 2002, 1998 by The McGraw-Hill Companies, Inc. All rights reserved
The finely divided residue resulting from the combustion of ground or powdered coal, transported from the firebox through the boiler by flue gases.
as the aggregate.
McGraw-Hill Dictionary of Architecture and Construction. Copyright © 2003 by McGraw-Hill Companies, Inc.