What are the two different classes of fly ash?
What are the two different classes of fly ash?
ASTM C618 defines two classes of fly ash for use in concrete: 1) Class F, usually derived from the burning of anthracite or bituminous coal, and 2) Class C, usually derived from the burning of lignite or subbituminous coal.
Which is Better Class C or Class F fly ash?
The results show that class C fly ash non-cement mortar demonstrated a higher strength compared to class F fly ash at ambient temperature. In contrast, the class F fly ash non-cement mortars exhibited a better performance than class C when it cured at heat temperature.
What classification is fly ash?
Chemistry. Fly ash consists primarily of oxides of silicon, aluminum iron and calcium. Magnesium, potassium, sodium, titanium, and sulfur are also present to a lesser degree. When used as a mineral admixture in concrete, fly ash is classified as either Class C or Class F ash based on its chemical composition.
What is Class C fly ash used for?
Fly ash, particularly Class C, can effectively be used to stabilize soil for various types of construction. High calcium fly ash (Class C) acts as a good source of calcium hydroxide which “self activates”, reacting with silica and alumina in the fly ash and soil to form a cementitious hydration product.
What is Type F fly ash?
Composition. Class F fly ash is designated in ASTM C 618 and originates from anthracite and bituminous coals. It consists mainly of alumina and silica and has a higher LOI than Class C fly ash. Class F fly ash also has a lower calcium content than Class C fly ash.
Can fly ash replace Portland cement?
Typically, 15 percent to 30 percent of the portland cement is replaced with fly ash, with even higher percentages used for mass concrete placements. An equivalent or greater weight of fly ash is substituted for the cement removed. The substitution ratio for fly ash to portland cement is typically 1:1 to 1.5:1.
Can fly ash replace portland cement?
What is the difference between coal ash and fly ash?
Coal ash is a general term—it refers to whatever waste is leftover after coal is combusted, usually in a coal-fired power plant. It contains arsenic, mercury, lead, and many other heavy metals. Fly ash particles are the lightest kind of coal ash—so light that they “fly” up into the exhaust stacks of the power plant.
What is F fly ash?
Fly Ash is a pozzolanic cement replacement that enhances the performance of concrete by increasing compressive strength, improving workability, durability, long term strength, resistance to freeze-thaw damage and reduces permeability, efflorescence shrinkage, thermal cracking, alkali silica reaction and sulfate attack …
What is LOI in fly ash?
LOI is routinely used as an indicator for determining the residual carbon content in fly ash. In fact, LOI also includes the presence of carbonates and combined water in clay minerals [19] but the combustion of carbon is the major contributing component of ignition loss [3].
What kind of materials can fly ash be used for?
It is a fine grey coloured powder having spherical glassy particles that rise with the flue gases. As fly ash contains pozzolanic materials components which reach with lime to form cementatious materials. Thus Fly ash is used in concrete, mines, landfills and dams.
Which is better class F or C fly ash?
Class F fly ash, is available in larger quantities, which is generally low in lime, less than 15%, and contains greater combination of silica, alumina and iron (more than 70%) compared to Class C fly ash.
What is the difference between lime and fly ash?
Lime content in the fly ash gives tan and light colours where as brownish colour is imparted by the presence of iron content. A dark grey to black colour is typically attributed to an elevated un-burned content. The classification of fly ash is done differently as per codes used.
How much does a cubic foot of fly ash weigh?
The bottom ash aggregate may be graded to meet the requirements of ASTM C 331 Specification for lightweight aggregate for use in concrete Masonry units. This ash aggregate usually has a unit weight of 60 – 65 pounds per cubic foot. This aggregate may also be blended with other lightweight aggregates to achieve greater quantities.
