Concrete Mix with Fly Ash
Fly ash or pulverized fuel ash (pfa) is a finely divided powder thrown out as a waste material at the thermal power plants using pulverized coal for raising steam in the boilers. The fly ash is an industrial waste and great hazard for our environment. In the building industry, the use of fly ash as a part replacement of cement in mortar and concrete at the construction site has been made all over the world and is well known.
The important building materials which can be produced from fly ash are:
- Portland fly ash cement.
- Ready-mixed fly ash concrete.
- Precast fly ash concrete building units.
- Sintered fly ash lightweight aggregate for concrete.
- Lime fly ash cellular concrete.
- Fly ash building bricks.
- Fly ash stabilized high-magnesia cement.
- Oil-well cementing composition.
- Hydraulic binders.
- Bituminous products.
The advantages of fly ash concrete over the corresponding plain cement concrete are:
- Improved workability.
- Lower heat of hydration.
- The increase in creep with fly ash content up to 15% is negligible.
- Increases the modulus of elasticity of concrete when concretes of the same strength with and without fly ash are compared.
- Superior resistance to freezing and thawing.
- Improved sulphate resistance.
- Lower water and air permeability.
- Lower leaching of lime liberated during hydrating of cement.
- Reduced alkali-aggregate reactions.
- Greater resistance to attack of aggressive waters.
Since a huge quantity of cement is used in mass concrete construction and the cost of fly ash is negligible as compared to that of the cement, the use of fly ash concrete brings about a substantial saving in cement consumption and overall construction cost. Fly ash concrete may be used in concrete structures including high strength concrete without any risk of steel corrosion. Researchers have proved that concrete with approved quality fly ash does not induce corrosion of reinforcing steel even in marine and industrial aggressive environments. With proper mix design the 7 and 28-days strength of fly ash concrete may be equal or even more than plain concrete. The 90 days strength of fly ash concrete may be more than 140% of plain concrete.
Steel Building Designs –
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