Fly Ash Material and Characteristics

Fly ash is one of the residues created during the combustion of coal in coal-fired power plants and comprises fine particles that rise with the flue gases. In the past, fly ash produced from coal combustion was simply entrained in flue gases and

Table 16.2 Historical compositions of automotive friction brake materials [1]

Material description

Application(s)

Approximate

year

Cast iron on steel

Railroad car brake blocks

prior to1870s

and tires

Hair or cotton belting (limited by charring

Wagon wheels and early

ca. 1897

at about 300°F)

automobiles

Woven asbestos with brass and other

Automobiles and trucks

ca. 1908

wires for increased strength and

performance

Molded limings with shorter chrysotile

Automobiles and trucks

ca. 1926

fibers, brass particles, and low-ash

bituminous coal

Dry-mix molded material to replace cast

London underground

ca. 1930

iron brake blocks that produced

metallic dust that shorted electric train

rails

Flexible resin binders developed along

Brake drum limings

1930s

with more complex formulations

Resin bonded metallic brake limings

Industrial and aircraft

1950s

applications

Glass fibers, mineral fibers, metal fibers,

Automotive and trucks

1960s

carbon, and synthetic fibers to provide

semi-metallics with higher

performance than asbestos (beginning

of safety issues with asbestos)

Non-asbestos (fiberglass) materials

Brake drums on original

1980s

equipment cars

Suggested use of carbon fibers

Automotive brakes

1991

dispersed into the atmosphere. This created environmental and health concerns that prompted laws which have reduced fly ash emissions to less than 1% of ash produced. Coal-fired power plants all over the world generate huge amounts of fly ash each year, 70 million tons of which are produced in the United States alone. Fly ash is a waste by-product material that must be disposed off or recycled. Worldwide, more than 65% of fly ash produced is disposed off in landfills or in ash ponds. Only 40% of all fly ashes generated in the United States find beneficial applications in concrete, embankments, road subbase, etc. [15, 16]. The recycling of fly ash has become an increasing concern in recent years due to increasing landfill costs and the current interest in sustainable development. Also, there have been few attempts at value-added application of fly ash in composite fabrications [17-19]. In recent years, research on fly ash as a filler and reinforcement in metal-matrix composites (MMCs) and polymer-matrix composites (PMCs) has been growing.

Fly ash particles are classified into two types, precipitator and cenosphere. Generally, the solid spherical particles of fly ash are called precipitator fly ash. It is composed of the crystal compound such as quartz, mullite, and hematite, and glassy compound such as silica glass, and other metal oxides. The precipitator fly

Renewable Energy Eco Friendly

Renewable Energy Eco Friendly

Renewable energy is energy that is generated from sunlight, rain, tides, geothermal heat and wind. These sources are naturally and constantly replenished, which is why they are deemed as renewable.

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