Basically fly ash is by-product left
from burning coal which is collected in electrical generating
station or baghouse. Using of fly ash in concrete has many good
results and also improves concrete performance in both the fresh
and hardened condition.
Use of Fly Ash for concrete in hot
- Increases Workability- Fly ash provides
lubricant effect in the concrete thus increasing the workability of
- Decreases water demand- Fly ash reduces water
requirements by 2 to 10 percent .
- Setting time - Concrete will set slowly when
fly ash is used.
- Early-age strength- Initially fly ash affects
the strength of concrete so its better reducing fly ash
- Long-term strength - Decrease in water use
leads to to gain strength over the period of time.
- Increases Pumpability - Fly ash tends to
reduction in frictional losses while pumping concrete.
- Reduces heat of hydration- Replacing of cement
with fly-ash in the concrete reduce the heat of hydration of
- Improves Placeability and Finishability - Fly
ash allows concrete to move more fluidly which makes it easy for
placing and finishing processes.
- Reduces permeability - The reduction in water
use and development of additional cementitious compounds tends to
decrease pore interconnectivity of concrete, thus reducing in
- Improves durability- Fly ash use increases in
cementitious compounds with reduction in permeability ultimately
resulting in improved durability.
- Decreases resistance to carbonation- Fly ash
use in concrete reduces its resistance to carbonation.
- Improves sulfate resistance- Sulfate
resistance is increased by use of F-class fly ash in concrete.
Summary- Basically fly ash is by-product left from burning coal
which is collected in electrical generating station. Fly ash allows
concrete to move more fluidly which makes it easy for placing and