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Fly ash is a pozzolan. When mixed with lime (calcium hydroxide), pozzolans combine
to form cementitious compounds. Concrete containing fly ash becomes stronger, more
durable, and more resistant to chemical attack. Further, fly ash particles are hard
and round, which has a ‘ball bearing’ effect that allows concrete to be produced
using less water. Both characteristics contribute to enhanced concrete workability
and durability
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FLY ASH is sourced from state of the art government-run coal-fired thermal power
plants in the State of Gujarat in India, which have one-source long-term contracts
for quality coal fly ash procurement. Moreover, the in-built classification system
in the power plant enables extraction of a specific fineness consistently
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FLY ASH is packed in 1.4 MT Jumbo bags especially for exports with liners.
Since jumbo bags are critical during handling of fly ash, we use high grade jumbo
bags.
FLY ASH is sourced from state of the art government-run coal-fired thermal power
plants in the State of Gujarat in India, which have one-source long-term contracts
for quality coal fly ash procurement. Moreover, the in-built classification system
in the power plant enables extraction of a specific fineness consistently
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ASTMC 618F
Two classes of fly ash are defined by ASTM C618: Class F fly ash and Class
C fly ash. The chief difference between these classes is the amount of calcium,
silica, alumina, and iron content in the ash. The chemical properties of the fly
ash are largely influenced by the chemical content of the coal burned(i.e.,anthracite,bituminous,and,lignite).
Not all fly ashes meet ASTM C618 requirements, although depending on the
application, this may not be necessary. Ash used as a cement replacement must meet
strict construction standards, but no standard environmental standards have been
established in the United States. 75% of the ash must have a fineness of 45 µm or
less, and have a carbon content, measured by the loss on ignition (LOI), of less
than 4%. In the U.S., LOI needs to be under 6%. The particle size distribution of
raw fly ash is very often fluctuating constantly, due to changing performance of
the coal mills and the boiler performance. This makes it necessary that fly ash
used in concrete needs to be processed using separation equipment like mechanical
air classifiers. Especially important is the ongoing quality verification. This
is mainly expressed by quality control seals like the Indian ISI mark or the DCL
mark of the Dubai Municipality.
Class F fly ash
The burning of harder, older anthracite and bituminous coal typically produces
Class F fly ash. This fly ash is pozzolanic in nature, and contains less than 10%
lime (CaO). Possessing pozzolanic properties, the glassy silica and alumina of Class
F fly ash requires a cementing agent, such as Portland cement, quicklime, or hydrated
lime, with the presence of water in order to react and produce cementitious compounds.
Alternatively, the addition of a chemical activator such as sodium silicate (water
glass) to a Class F ash can lead to the formation of a geopolymer.
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