What is the composition of fly ash?
Fly ash is predominately composed of silica, aluminum, iron, calcium, and oxygen, but the particles may also contain heavy metals such as arsenic and lead at trace levels.
What are the advantages of using fly ash in concrete?
Fly ash use in concrete improves the workability of plastic concrete, and the strength and durability of hardened concrete. Fly ash use is also cost effective. When fly ash is added to concrete, the amount of portland cement may be reduced.
What is the density of fly ash?
The bulk density of fly ash is 650… 700 kg/m3.
Is fly ash a hazardous material?
Fly ash is not considered a hazardous waste under EPA’s Resource Conservation and Recovery Act (RCRA).
What is fly ash in cement?
Fly ash is a pozzolan, a substance containing aluminous and siliceous material that forms cement in the presence of water. When used in concrete mixes, fly ash improves the strength and segregation of the concrete and makes it easier to pump.
Is fly ash a sustainable material?
Also, fly ash is a material with sustainable properties. The results derived from the experiments indicate that mortar and concrete made with 100% fly ash C require an alkaline solution to produce similar (comparable) strength characteristics as Portland cement concrete.
What are the disadvantages of fly ash?
Disadvantages
- Slower strength gain.
- Seasonal limitation.
- Increased need for air-entraining admixtures.
- Increase of salt scaling produced by higher proportions of fly ash.
What is the disadvantage of using fly ash?
Disadvantages of Fly Ash The quality of fly ash can affect the quality and strength of Cement concrete. Poor quality fly ash can increase the permeability of the concrete and cause damage to the building.
What is the maximum size of fly ash?
Since the particles solidify rapidly while suspended in the exhaust gases, fly ash particles are generally spherical in shape and range in size from 0.5 µm to 300 µm.
How does fly ash affect the quantity of concrete?
Generally, air entrainment modified concrete to be frost resistant if all other criteria are met. Fly ash might lead to increase the quantity of admixtures which are necessary to obtain acceptable level of entrained air and occasionally influence entrained air stability in fresh concrete.
Why do we use fly ash as a concrete admixture?
The benefits of fly ash in concrete: Workability, concrete is easier to place with less effort. Ease of pumping, pumping requires less energy and longer pumping distances are possible. Improved finishing, concrete is creamier with clear sharp architectural patterns easier to achieve. Reduced bleeding, fewer bleed channels decrease permeability and chemical attack.
What does fly ash do to the strength of concrete?
The benefits are: Higher strength, fly ash continues to combine with free lime increasing compressive strength over time. Increased durability, dense fly ash concrete helps keep aggressive compounds on the surface. Reduced shrinkage, the lubricating action of flyash concrete reduces water content and drying shrinkage.
What is fly ash used for in concrete?
Portland cement. Owing to its pozzolanic properties, fly ash is used as a replacement for Portland cement in concrete. The use of fly ash as a pozzolanic ingredient was recognized as early as 1914, although the earliest noteworthy study of its use was in 1937.