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Topic: Pozzolanic ash


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In the News (Mon 22 Dec 14)

  
  Coal Fly Ash - Material Description
The fly ash produced from the burning of pulverized coal in a coal-fired boiler is a fine-grained, powdery particulate material that is carried off in the flue gas and usually collected from the flue gas by means of electrostatic precipitators, baghouses, or mechanical collection devices such as cyclones.
Fly ash is useful in many applications because it is a pozzolan, meaning it is a siliceous or alumino-siliceous material that, when in a finely divided form and in the presence of water, will combine with calcium hydroxide (from lime, Portland cement, or kiln dust) to form cementitious compounds.
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.
www.tfhrc.gov /hnr20/recycle/waste/cfa51.htm   (2541 words)

  
 Using Fly Ash in Concrete - MC Magazine Winter 2000 - Concrete Publications - NPCA
Most fly ash is pozzolanic, which means it's a siliceous or siliceous-and-aluminous material that reacts with calcium hydroxide to form a cement.
Typically, fly ash is added to structural concrete at 15-35 percent by weight of the cement, but up to 70 percent is added for mass concrete used in dams, roller-compacted concrete pavements, and parking areas.
Fly ash is considered to have met C618's requirements if the 7- or 28-day strength of a sample with 20 percent fly ash reaches 75 percent of the control strength in an ASTM C109 test.
www.precast.org /publications/mc/TechArticles/00_Winter_FlyAsh.htm   (1906 words)

  
 FAQ
This percentage is obtained by dividing the mass of fly ash in a cubic meter of concrete by the sum of all cementing and pozzolanic materials the mix.
Pozzolanic does not promote or endorse such high uses of fly ash but encourages continued investigation into the appropriateness of higher uses of fly ash in highly engineered and monitored concrete applications.
Fly ash improves the engineering properties of concrete and lowers the environmental impact of any project it is used on, typically without impacting the costs associated with the job.
www.lehighnw.com /canada/pages/pozzo5.htm   (981 words)

  
 Pozzolans, Pompeii, Naples, Thera, Santorini, Lost Atlantis, and Sophia Loren Concrete Construction - Find Articles
Pozzolans usually serve three purposes: (1) they increase strength and decrease permeability; (2) their use makes concrete a patriotic material because it serves as a useful "dump" for waste products; and (3) they provide an economic advantage by lowering concrete costs (because they are cheaper than portland cement).
Fly ash (fine, usually spherical particles that formerly were emitted from electric utility smoke stacks but now are captured) and volcanic ash are two widely used pozzolans.
The word pozzolan is an Anglicized version of the Latin word pozzulana that was primarily applied to the volcanic ash (a glassy, dust-like material) from the eruptions of Mt. Vesuvius collected near the base of the volcano.
www.findarticles.com /p/articles/mi_m0NSX/is_7_49/ai_n6149106   (779 words)

  
 Development of Bottom Ash as Pozzolanic Material   (Site not responding. Last check: 2007-10-20)
Bottom ash, which was rarely used in concrete due to its inactive pozzolanic reaction, improved its quality by grinding until the particle size retained on Sieve 325 was less than 5% by weight.
Compressive strengths of mortar containing 20–30% of bottom ash as cement replacement were much less than that of cement mortar at all ages, but the use of ground bottom ash produced higher compressive strength than the cement mortar after 60 days.
When ground bottom ash was used at a 20% replacement of cement to make concrete, the concrete with higher cement content produced higher percentage compressive strength as well as a higher development rate than those of the low cement content concretes.
www.pubs.asce.org /WWWdisplay.cgi?0300484   (266 words)

  
 What is Coal Ash?
Fly ash is the fine powder formed from the mineral matter in coal, consisting of the noncombustible matter in coal plus a small amount of carbon that remains from incomplete combustion.
Fly ash is generally light tan in color and consists mostly of silt-sized and clay-sized glassy spheres.
Bottom ash is a coarse, granular, incombustible byproduct that is collected from the bottom of furnaces that burn coal for the generation of steam, the production of electric power, or both.
www.undeerc.org /carrc/html/WhatisCoalAsh.html   (356 words)

  
 Chapter 3 - Fly Ash Facts for Highway Engineers - Recycling - Pavements - FHWA   (Site not responding. Last check: 2007-10-20)
The substitution ratio for fly ash to portland cement is typically 1:1 to 1.5:1.
The fineness of fly ash is important because it affects the rate of pozzolanic activity and the workability of the concrete.
Fly ashes tend to contribute to concrete strength at a faster rate when these components are present in finer fractions of the fly ash.
www.fhwa.dot.gov /pavement/recycling/fach03.cfm   (1971 words)

  
 ACI 232.2R Use of Fly Ash in Concrete - IHS, Inc
Fly ash, a by-product from the combustion of pulverized coal, is widely used as a cementitious and pozzolanic ingredient in hydraulic cement concrete.
In subsequent research, Davis and colleagues studied the reactivity of fly ash with calcium and alkali hydroxides in portland-cement paste and the ability of fly ash to act as a preventive measure against deleterious alkaii-aggregate reactions.
Fly ash is now used in concrete for many reasons, including improvements in workability of fresh concrete, reduction in temperature rise during initial hydration, improved resistance to sulfates, reduced expansion due to alkali-silica reaction, and contnbutions to the durability and strength of hardened concrete.
aec.ihs.com /document/abstract/DCQLFBAAAAAAAAAA   (920 words)

  
 Fly Ash - Utilization of Recycled Materials in Illinois Highway Construction - Recycling - Pavements - FHWA   (Site not responding. Last check: 2007-10-20)
Heavier particles of ash (bottom ash or slag) fall to the bottom of the burning chamber, while the lighter particles (fly ash) remain suspended in the flue gases.
Class F fly ash is produced by burning anthracite or bituminous coal; whereas, Class C fly ash is produced from lignite or sub-bituminous coal (1).
In Illinois, fly ash is used as a fine aggregate or supplementary cementitious material in PCC; however, the Department limits the use of Class F to no more than 15 percent by weight, and Class C to no more than 20 percent by weight.
www.fhwa.dot.gov /pavement/recycling/recfly.cfm   (421 words)

  
 High Volume Fly Ash Concrete Technology
The fly ash is then collected in electrostatic precipitators or bag houses and the fineness of the fly ash can be controlled by how and where the particles are collected.
Fly ash can be introduced in concrete directly, as a separate ingredient at the concrete batch plant or, can be blended with the opc to produce blended cement, usually called portland-pozzolana cement (ppc) in India.
Fly ash blended cements are produced by several cement companies in India.
www.hvfacprojectindia.com /hvfactechnology/basics.htm   (692 words)

  
 Concrete Topics -- Boral Material Technologies
Workability and placeability of concrete is typically improved with the inclusion of fly ash because the fly ash particles are spherical in nature and act as ball bearings.
A pozzolan is defined by ASTM as a siliceous or alumino-siliceous material which itself possesses little or no cementitious value but will, in finely divided form and in the presence of moisture, react with calcium hydroxide at ordinary temperatures to form compounds possessing cementitious properties.
ASTM C 618 classifies the types of fly ash as either Class C or Class F. Class C fly ashes have higher amounts of calcium oxide and hence are cementitious as well as pozzolanic whereas Class F fly ashes are only pozzolanic.
www.concrete.com /documents/boralarticle2.htm   (711 words)

  
 Coal Fly Ash - User Guideline - Portland Cement Concrete
The relative resistance of fly ash to sulfate deterioration is reportedly a function of the ratio of calcium oxide to iron oxide.
Fly ash, especially Class F fly ash, is effective in three ways in substantially reducing alkali-silica expansion: 1) it produces a denser, less permeable concrete; 2) when used as a cement replacement it reduces total alkali content by reducing the Portland cement; and 3) alkalis react with fly ash instead of reactive silica aggregates.
When fly ash is used as a separately batched material, trial mixes should be made using a water-cement plus fly ash (w/c+f) ratio, sometimes referred to as the water-cementitious ratio, instead of the conventional w/c ratio.
www.rmrc.unh.edu /Partners/UserGuide/cfa53.htm   (4064 words)

  
 Fly Ash
Materials such as fly ash are produced principally at coal-fueled electric power plants
Fly ash use improves concrete performance, making it stronger, more durable, and more resistant to chemical attack.
Fly ash use also creates significant benefits for our environment.
www.flyash.com   (171 words)

  
 Pozzolanic mixture for stabilizing landfill leachate - Patent 4917733
A pozzolanic mixture for stabilizing landfill leachate which includes fly ash with an excess of lime, kiln dust, and optionally bottom ash, which is combined with the landfill leachate with a makeup quantity of water to produce a stable cementitious pozzolanic mixture that hardens to a mortar-like material.
A pozzolanic mixture for stabilizing landfill leachate, comprising: fly ash, kiln dust, and landfill leachate which is cured to form a solid, leach-resistant body.
In accordance with the present invention, a pozzolanic mixture is produced by combining lime enriched fly ash with kiln dust, landfill leachate, and optionally, bottom ash.
www.freepatentsonline.com /4917733.html?highlight=4081285   (3579 words)

  
 New Page 1
Fly ash is a pozzolanic material and has been classified into two classes, F and C, based on the chemical composition of the fly ash.
However, fly ash that are produced from the same source and which have very similar chemical composition, can have significantly different ash mineralogies depending on the coal combustion technology used.
Since the lime content of class F fly ash is relatively low, addition of lime is necessary for hydration reaction with the pozzolans of the fly ash.
geoserver.cee.wisc.edu /fauga/new_page_1.htm   (983 words)

  
 EBNet -- Pozzolan Links
Some pozzolans, for various reasons, are also expensive, but the most abundant and widely available, fly ash, is not, and typically costs about half as much by weight as cement.
Class C fly ashes are in themselves mildly cementitious, and have been combined with lime or even calcium carbonate soils to produce moderately strong concretes.
Both classes of fly ash are restricted by the 1997 UBC to 25% of cementitious material "in special exposure conditions" (section 1904), but this restriction is widely interpreted to apply to concrete in all conditions.
www.ecobuildnetwork.org /pozzo.htm   (1223 words)

  
 Pozzolana - Wikipedia, the free encyclopedia
Pozzolana, also known as pozzolanic ash, is a fine, sandy volcanic ash, originally discovered and dug in Italy at Pozzuoli in the region around Vesuvius, but later at a number of other sites.
Modern pozzolanic cements are a mix of natural or industrial pozzolans and Portland cement.
Some industrial sources of materials with pozzolanic properties are: Class F (silicious) fly ash from coal fired power plants, silica fume from silicon production, rice husk ash from rice paddy-fields (agriculture), and metakaolin from oil sands operations.
en.wikipedia.org /wiki/Pozzolanic_ash   (426 words)

  
 Ash Basics Company
In today’s coal ash industry, the largest volume utilization of CCPs in the United States is the use of fly ash as a mineral admixture in ready mix concrete.
The use of fly ash in concrete accounts for approximately 30% of all CCP utilization in the U.S., with potential to grow if concrete suppliers would increase their fly ash percentage in any given mix design.
It is a low strength slurry consisting generally of fly ash, water and Portland Cement which can be used in any project where access and compaction of conventional material like soil or stone are an issue, such as around buried pipe, under concrete building slabs, or as a fill material for erosion conditions.
www.biztechnologysolutions.net /dean/utilization.asp   (1113 words)

  
 Segregated Dry Fly Ash Handling at Thermal Power Station
Due to its pozzolanic nature, when used in cement, mortar or concrete, it reacts with alkalies, primarily calcium hydroxide, released during hydration of cement, forming calcium silicate hydrate (C-S-H) bond that adds to the strength of the concrete.
The fineness of fly ash particles collected in different fields of ESP is a function of various parameters such as degree of coal pulverisation, combustion characteristics of the boiler, design of ESP etc. However, irrespective of all these parameters, average particle size of fly ash decreases from the first field onwards.
Availability of segregated dry fly ash in smaller bags for low volume users in jumbo bags for medium volume users and in bulk tankers for high volume users is necessary for large scale utilisation of fly ash in high value added applications.
www.tifac.org.in /news/flybag.htm   (1606 words)

  
 NEBCO, Inc. - Building Nebraska From The Ground Up
Nebraska Ash was formed in 1976 for the express purpose of handling coal combustion products at coal fired electric generating stations.
OLandB was organized in 1903 as an interurban railroad to connect Lincoln to Omaha to the northeast and with Beatrice to the south.
Bottom ash is utilized primarily as a road aggregate and base for counties and ranchers in the surrounding area.
www.nebcoinc.com /building_nebraska   (2730 words)

  
 ASTM Methods
Pozzolanic admixtures shall be sampled and tested in accordance with the requirements established in C311.
Covers pozzolanic blended material consisting of an intimate unIAOrm blend of Class F and Class C fly ashes, or a blend of Class F fly ash with cement kiln dust.
Covers the determination of quantity (Q) and intensity (I) results for several elements in soils, spoils, fly ash, and other soil substitutes to ascertain their suitability for the growth of vegetation and possible adverse effects for metals on the food chain.
www.mcrcc.osmre.gov /ccb/ASTM.htm   (2314 words)

  
 The American Society for Testing and Materials (ASTM) C618
The three classes of pozzolans are Class N, Class F, and Class C. Class N is raw or calcined natural pozzolan such as some diatomaceous earths, opaline cherts, and shales; tuffs, volcanic ashes, and pumicites; and calcined clays and shales.
Class F is pozzolanic fly ash normally produced from burning anthracite or bituminous coal.
Class C is pozzolanic and cementitious fly ash normally produced from burning lignite or subbituminous coal.
www.undeerc.org /carrc/html/ASTMC618.html   (147 words)

  
 ST: Concrete Industry: Why Use Fly Ash?
Fly ash combines with alkalis from cement that might otherwise combine with silica from aggregates, thereby preventing destructive expansion.
The pozzolanic reaction between fly ash and lime generates less heat, resulting in reduced thermal cracking when fly ash is used to replace a percentage of Portland Cement.
The ball-bearing effect of fly ash in concrete creates a lubricating action when concrete is in its plastic state.
www.stiash.com /L1/concrete_whyflyash.html   (362 words)

  
 Additional Reactions
The needed physical properties of the phases found in fly ash and the relevant hydration products are summarized in Table 1.
While specific gravities, molecular weights, and molar volumes are readily available in the literature [3, 7], heat of formation data have yet to be located for all of the phases.
to pozzolanic C-S-H, for the case where there is an excess of silica due to the presence of fly ash or silica fume.
ciks.cbt.nist.gov /~bentz/flyash/node7.html   (569 words)

  
 ejge paper 2000-094   (Site not responding. Last check: 2007-10-20)
Recent research, based on pozzolanic activity, found that rice husk ash was a potential material to be utilized for soil improvement.
Fly ash or pozzolanic materials, which are regarded as wastes, may be used to make these soil improvements.
Recent research, based on pozzolanic activity, found that rice husk ash was a potential material for soil improvement (Muntohar 1997 and 1999).
www.ejge.com /2000/Ppr0019/Ppr0019.htm   (2030 words)

  
 Amazon.com: "pozzolanic activity": Key Phrase page   (Site not responding. Last check: 2007-10-20)
Pozzolanic index with cement Pozzolanic activity index test (ASTM C-311) with cement showed that Pinatubo ejecta in the form of slurry sediment (Si, S2) and the...
The pozzolanic activity is dependent upon their physical form and the amounts of glass and zeolites present.
Their pozzolanic activity is attributable to the presence of Si02 and A1203 in amorphous form.
www.amazon.com /phrase/pozzolanic-activity   (555 words)

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