ash is also produced as
a by product from industrial plants using pulverized
coal or lignite as fuel for the boilers.
is not all carbon. Coal also contains quantities of
When coal is consumed in a power plant to generate electricity, it is
ground to the fineness of powder. Blown into
the power plant’s boiler, the
carbon is consumed — leaving molten particles rich in silica,
calcium. These particles solidify as microscopic, glassy spheres that are collected
from the power
plant’s exhaust before they can
“fly” away — hence the
product’s name: Fly Ash. Fly ash particles
glassy, spherical shaped “ball
bearings” — typically finer than cement particles.
ash (also known as Pulverised fuel ash/chimney ash/hopper
about 80 percent of the total ash generated in the power plant.
about 20 percent of ash gets collected at the bottom of
the boiler and is taken
out by suitable technologies and is referred as bottom ash
(shown on left).
Bottom ash – a heavier ash particle that falls to
the “bottom” of power
plant boilers – can be used in structural fill applications
and as aggregate
for manufacturing concrete blocks.
fly ash alone or alongwith bottom ash is carried to storage or
lagoon or pond in the form of water slurry and deposited, it is termed
ash. Whereas if fly ash, alone or alongwith bottom ash is
carried to a storage
or deposition site in dry form and deposited, it is termed as mound ash.
ash can be used in a variety of structural and low strength fill
It can be used as a mineral filler for paints, shingles, carpet backing
other products. It can be used in manufacturing mortars and stuccos. It
has various agricultural applications. But the largest application for
is in the production of concrete.
rate of fly ash for portland cement will vary depending
chemical composition of both the fly ash and the portland cement. The
specified is a minimum
of 1 to 1 ½ pounds of fly ash to
1 pound of cement. It should be noted that the amount of fine aggregate will
have to be reduced to accommodate the additional volume of fly ash.
This is due
to fly ash being lighter than the cement.