The fineness of fly ash can be determined by wet sieving (Section 7.2) , dry sieving (Section 7.3) or with the Blaine air permeability apparatus (Section 7.4). This test method describes the determination of fly ash fineness by wet sieving on a 45/. ~m sieve (ISO 565).
What are the tests conducted on fly ash?
The available alkali test , which is commonly used to measure fly ash alkali, takes approximately 35 days for execution and reporting. Hence, in many instances the fly ash has already been incorporated into concrete before the test results are available.
How can you tell the quality of fly ash?
The four most relevant characteristics of fly ash for use in concrete are loss on ignition (LOI), fineness, chemical composition and uniformity . LOI is a measurement of unburned carbon (coal) remaining in the ash and is a critical characteristic of fly ash, especially for concrete applications.
How do you detect fly ash in concrete?
After the residue has been allowed about 15 minutes to dry, a small portion is tapped from the sieve onto a microscope slide and examined , preferably with a dark background. If any glassy spheres can be seen it indicates that there is fly ash in the sample.
How do you measure the pH of fly ash?
The pH value was tested by dissolving fly ash into distilled water followed with pH measurement. Fly ash with pH value ranged from 8 to 11 tends to experience rapid setting [14]. In addition, pH value of fly ash has closely correlation with its CaO content. High CaO content in fly ash resulted in higher pH value [10].
Is fly ash a specification?
Fly ash consists primarily of oxides of silicon, aluminum iron and calcium. ... American Association of State Highway Transportation Officials (AASHTO) M 295 [American Society for Testing and Materials (ASTM) Specification C 618] defines the chemical composition of Class C and Class F fly ash .
How many types of fly ash are there?
Two classes of fly ash are defined in ASTM C618: 1) Class F fly ash, and 2) Class C fly ash. Fly ash that is produced from the burning of anthracite or bituminous coal is typically pozzolanic and is referred to as a Class F fly ash if it meets the chemical composition and physical requirements specified in ASTM C618.
Does fly ash weaken concrete?
Poor-quality fly ash can have a negative effect on concrete . The principle advantage of fly ash is reduced permeability at a low cost, but fly ash of poor quality can actually increase permeability. Some fly ash, such as that produced in a power plant, is compatible with concrete.
What does fly ash do to cement?
Fly ash use in concrete improves the workability of plastic concrete , and the strength and durability of hardened concrete. ... When fly ash is added to concrete, the amount of portland cement may be reduced.
Does fly ash absorb water?
In this study, a poor water sorbing fly ash was transformed into a high water-absorbing material for improving soil water retention during the drought period. The fly ash water absorbent (FAWA) exhibited high water-absorbing capacity (WAC) of 310 g/g at par with commercially available superabsorbent
What is the chemical formula of fly ash?
This standard determines the usability of fly ash that can be used in concrete and classifies the various types, based partially on the measurement of the combined cumulative amounts of three oxides in the fly ash chemical composition – silicon dioxide (SiO2) , aluminum oxide (Al2O3) and iron oxide (Fe2O3).
How do you use fly ash?
Fly ash can be used as prime material in many cement-based products , such as poured concrete, concrete block, and brick. One of the most common uses of fly ash is in Portland cement concrete pavement or PCC pavement.
What is a source of fly ash?
Fly ash is produced by coal-fired electric and steam generating plants . Typically, coal is pulverized and blown with air into the boiler’s combustion chamber where it immediately ignites, generating heat and producing a molten mineral residue.
Is fly ash hazardous?
Fly ash particles (a major component of coal ash) can become lodged in the deepest part of your lungs, where they trigger asthma, inflammation and immunological reactions. Studies link these particulates to the four leading causes of death in the U.S.: heart disease, cancer, respiratory diseases and stroke.
Is coal ash and fly ash the same thing?
Coal ash is a general term—it refers to whatever waste is leftover after coal is combusted, usually in a coal-fired power plant. ... 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 are the properties of fly ash?
Cenospheres are one of the most valuable materials found in fly ash. Their properties, such as high compressive strength, light weight, low water absorption, chemical inertness, and good thermal resistance , make them suitable to a wide range of applications.
