use of flyash in concrete

232.2R

Fly ash is used in concrete primarily because of its pozzolanic and cemen-titious properties. These properties contribute to strength gain and mayimprove performance of fresh and hardened concrete. Use of fly ash oftenresults in a reduction in the cost of concrete construction.

This report gives an overview of the origin and properties of fly ash, itseffect on the properties of portland-cement concrete, and the proper selec-tion and use of fly ash in the production of portland-cement concrete andconcrete products. The report contains information and recommendationsconcerning the selection and use of Class C and Class F fly ashes generallyconforming to the requirements of ASTM C 618. Topics covered include adetailed description of the composition of fly ash, the physical and chemi-cal effects of fly ash on properties of concrete, guidance on the handlingand use of fly ash in concrete construction, use of fly ash in the productionof concrete products and specialty concretes, and recommended proce-dures for quality assurance. Referenced documents give more informationon each topic.

Keywords: abrasion resistance, admixtures, alkali-aggregate reactions,concrete durability, concrete pavements, controlled low-strength materials,corrosion resistance, creep properties, drying shrinkage, efflorescence,fineness, finishability, fly ash, mass concrete, mixture proportioning, per-meability, portland cements, pozzolans, precast concrete, quality assur-ance, reinforced concrete, roller-compacted concrete, soil-cement,strength, sulfate resistance, thermal behavior, workability.

ACI 232.2R-96

Use of Fly Ash in Concrete

Reported by ACI Committee 232

Paul J. Tikalsky*

ChairmanMorris V. Huffman

Secretary

W. Barry Butler Jim S. Jensen Sandor Popovics

Bayard M. Call Roy Keck Jan Prusinski

Ramon L. Carrasquillo Steven H. Kosmatka D. V. Reddy

Douglas W. Deno Ronald L. Larsen Harry C. Roof

Bryce A. Ehmke V. M. Malhotra John M. Scanlon

William E. Ellis, Jr. Larry W. Matejcek Donald L. Schlegel

William H. Gehrmann Bryant Mather Ava Shypula

Dean Golden Richard C. Meininger Peter G. Snow*

William Halczak Richard C. Mielenz Samuel S. Tyson

G. Terry Harris, Sr. Tarun R. Naik Jack W. Weber

Allen J. Hulshizer Harry L. Patterson Orville R. Werner, II*

Tarif M. Jaber Terry Patzias

* Chairmen of Committee during preparation of this report.

ACI Committee Reports, Guides, Standard Practices, DesignHandbooks, and Commentaries are intended for guidance inplanning, designing, executing, and inspecting construction.This document is intended for the use of individuals who arecompetent to evaluate the significance and limitations of its con-tent and recommendations and who will accept responsibility forthe application of the material it contains. The American Con-crete Institute disclaims any and all responsibility for the appli-cation of the stated principles. The Institute shall not be liable forany loss or damage arising therefrom.Reference to this document shall not be made in contract docu-

ments. If items found in this document are desired by the Archi-tect/Engineer to be a part of the contract documents, they shallbe restated in mandatory language for incorporation by the Ar-chitect/Engineer.

CONTENTS

Chapter 1—General, p. 232.2R-21.1—Introduction1.2—Source of fly ash

on-

Chapter 2—Fly ash composition, p. 232.2R-42.1—General2.2—Chemical composition2.3—Crystalline composition2.4—Glassy composition2.5—Physical properties2.6—Chemical activity of fly ash in portland cement c

crete2.7—Future research needs

9e

Chapter 3—Effects of fly ash on concrete, p. 232.2R-3.1—Effects on properties of freshly-mixed concret

-1

ACI 232.2R-96 supersedes ACI 226.3R-87 and became effective January 1, 1996.Copyright © 1996, American Concrete Institute.All rights reserved including rights of reproduction and use in any form or by any

means, including the making of copies by any photo process, or by electronic ormechanical device, printed, written, or oral, or recording for sound or visual reproduc-tion or for use in any knowledge or retrieval system or device, unless permission inwriting is obtained from the copyright proprietors.

jcg

(Reapproved 2002)

232.2R-2 ACI COMMITTEE REPORT

rete of
3.2—Effects on properties of hardened conc
s-redthesh

Chapter 4—Concrete mixture proportioning, p. 232.2R-17

4.1—General4.2—Considerations in mixture proportioning

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ngny

ixedor-

Chapter 5—Fly ash specifications, p. 232.2R-15.1—Introduction5.2—Chemical requirements5.3—Physical requirements5.4—General specification provisions5.5—Methods of sampling and testing5.6—Source quality control5.7—Start-up oil and stack additives5.8—Rapid quality assurance tests

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s val-ce-

s of

Chapter 6—Fly ash in concrete construction, p. 232.2R21

6.1—Ready-mixed concrete6.2—Concrete pavement6.3—Mass concrete6.4—Bulk handling and storage6.5—Batching

3nd

turesh,d byiti-ing

Chapter 7—Fly ash in concrete products, p. 232.2R-27.1—Concrete masonry units7.2—Concrete pipe7.3—Precast/prestressed concrete products7.4—No-slump extruded hollow-core slabs

5

)

theringicalse ofthearlypor-

Chapter 8—Other uses of fly ash, p. 232.2R-28.1—Grouts and mortars8.2—Controlled low strength material (CLSM8.3—Soil cement8.4—Roller-compacted concrete8.5—Waste management

7that

ent

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Chapter 9—References, p. 232.2R-29.1—Organizational references9.2—Cited references9.3—Suggested references

n att the
Appendix—Rapid quality control tests, p. 232.2R-33
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CHAPTER 1—GENERAL

1.1—IntroductionFly ash, a by-product of coal combustion, is widely us

as a cementitious and pozzolanic ingredient in portlandment concrete. It may be introduced either as a separbatched material or as a component of blended cementuse of fly ash in concrete is increasing because it improsome properties of concrete, and often results in lower concrete. This report describes the technology of the usfly ash in concrete and lists references concerning the cacterization of fly ash, its properties, and its effects on ccrete. Guidance is provided concerning the specification

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use of fly ash, along with information on quality control fly ash and concrete made with fly ash.

According to ACI 116R, fly ash is “the finely divided reidue resulting from the combustion of ground or powdecoal and which is transported from the firebox through boiler by flue gases; known in UK as pulverized fuel a(pfa).” ACI 116R defines “pozzolan” as “a siliceous or sceous and aluminous material, which in itself possessesor no cementitious value but will, in finely divided form ain the presence of moisture, chemically react with calchydroxide at ordinary temperatures to form compounds sessing cementitious properties.” Fly ash possesses zolanic properties similar to the naturally occurripozzolans of volcanic or sedimentary origin found in maparts of the world. About 2000 years ago, the Romans mvolcanic ash with lime, aggregate and water to produce mtar and concrete (Vitruvius, 1960). Similarly, fly ash mixed with portland cement (which releases lime during dration), aggregate and water to produce mortar and crete. All fly ashes contains pozzolanic materials, howesome fly ashes possess varying degrees of cementitiouue without the addition of calcium hydroxide or portland ment because they contain some lime.

Fly ash in concrete makes efficient use of the producthydration of portland cement: (1) solutions of calcium aalkali hydroxide, which are released into the pore strucof the paste combine with the pozzolanic particles of fly aforming a cementing medium, and (2) the heat generatehydration of portland cement is an important factor in inating the reaction of the fly ash. When concrete containfly ash is properly cured, fly-ash reaction products fill in spaces between hydrating cement particles, thus lowethe concrete permeability to water and aggressive chem(Manmohan and Mehta, 1981). The slower reaction ratmany fly ashes compared to portland cement limits amount of early heat generation and the detrimental etemperature rise in massive structures. Properly protioned fly ash mixtures impart properties to concrete may not be achievable through the use of portland cemalone.

Fly ash from coal-burning electric power plants becaavailable in quantity in the 1930s. In the United States,study of fly ash for use in portland cement concrete begaabout that time. In 1937, R. E. Davis and his associates aUniversity of California published results of research concrete containing fly ash (Davis et al., 1937). This wserved as the foundation for early specifications, methodtesting, and use of fly ash.

Initially, fly ash was used as a partial mass or volumeplacement of portland cement, an expensive componeconcrete. However, as the use of fly ash increased, reseers recognized the potential for improved properties of ccrete containing fly ash. In subsequent research Davishis colleagues studied the reactivity of fly ash with calciand alkali hydroxides in portland-cement paste, and thwith the ability of fly ash to act as a preventive measagainst deleterious alkali-aggregate reactions. Muchsearch (Dunstan, 1976, 1980, and Tikalsky and Carrasq

FLY ASH IN CONCRETE 232.2R-3

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1992, 1993) has shown that fly ash often affects the rtance of concrete to deterioration when exposed to sulfThe U.S. Army Corps of Engineers, the Bureau of Reclation, major U.S. engineering firms, and others recognizedbeneficial effect of fly ash on the workability of fresh cocrete and the advantageous reduction of peak temperatumass concrete. The beneficial aspects of fly ash were cially notable in the construction of large concrete da(Mielenz, 1983). Some major engineering projects in United Kingdom, most notably the Thames Barrage, andUpper Stillwater Dam in the United States, incorporated75 percent mass replacement of portland cement by flyto achieve reduced heat generation and decreased permity.

In the United States, a new generation of coal-fired poplants was built during the late 1960s and 1970s, at leastially in response to dramatically increased oil prices. Thmodern power plants, utilizing efficient coal mills and staof-the-art pyroprocessing technology, produced finer ashes with a lower carbon content than those previoavailable. In addition, fly ash containing higher levels of ccium became available due to the use of new coal sou(usually subbituminous and lignitic). Concurrent with tincreased availability of fly ash, extensive research in NAmerica and elsewhere has led to better understanding chemical reactions involved when fly ash is used in concand improved technology in the use of fly ash in the concindustry. Fly ash is now used in concrete for many reasincluding reduced cost, improvements in workability fresh concrete, reduction in temperature rise during inhydration, improved resistance to sulfates, reduced exsion due to alkali-silica reaction, and contributions to therability and strength of hardened concrete.

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1.2—Source of fly ashDue to the increased use of pulverized coal as fuel for e

tric power generation, fly ash is now available in most arof the United States and Canada, and in many other pathe world. Fly ash is produced as a by-product of burncoals which have been crushed and ground to a finene70 to 80 percent passing a 75 µm (No. 200) sieve. Approximately 45,000 Gg (50 million tons) of fly ash is produced nually in the United States (American Coal Ash Associat1992). An estimated 10-12 percent of that total is utilizethe production of concrete and concrete products.

ASTM C 618 categorizes fly ashes by chemical comption, according to the sum of the iron, aluminum, and sicontent (expressed in oxide form). Class F ashes are noly produced from coals with higher heat energy, such atuminous and anthracite coals, although some sbituminous and lignite coals in the western United Staalso produce Class F fly ash. Bituminous and anthracitefly ashes rarely contain more than 15 percent calcium oxSubbituminous fly ashes typically contain more than 20 cent calcium oxide, and have both cementitious and zolanic properties. There are important differences in formance of fly ashes from different sources. As a groClass F ashes and Class C ashes generally show diff

e,

,

performance characteristics; however, the performancefly ash is not determined solely by its classification as eiClass F or Class C. In general, the sulfate resistance andity of a fly ash to mitigate the effects of alkali-silica reactare a function of the coal sources. Strengthening charactics of a fly ash vary widely depending on the physical chemical properties of the ash.

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1.2.1 Production and processing—The ash contents ocoals may vary from 4 to 5 percent for subbituminous anthracite coals, to as high as 35 to 40 percent for somnites. The combustion process, which creates temperaof approximately 1600 C (2900 F) liquifies the unburnminerals. Rapid cooling of these by-products upon leathe firebox causes them to form spherical particles, wipredominantly glassy structure. Many variables may afthe characteristics of these particles. Among these arecomposition, grinding mill efficiency, the combustion enronment (temperature and oxygen supply), boiler/buconfiguration, and the rate of particle cooling.

Modern coal-fired power plants that burn coal from a csistent source generally produce uniform fly ash. Howethe fly ash particles vary in size, chemical composition, density. Sizes may run from less than 1 µm (0.00004 in.) tomore than 80 µm (0.00315 in.), and density of individuparticles from less than 1 Mg/m3 (62.4 lb/ft3) hollow spheresto more than 3 Mg/m3 (187 lb/ft3). Collection of these particles from the furnace exhaust gases is accomplished bytrostatic or mechanical precipitators, or by baghousestypical gas flow pattern through an electrostatic precipitis shown in Fig. 1.1.

As the fly ash particles are collected, they segregate iquential precipitator hoppers according to their size and sity; larger/heavier particles tend to accumulate closer togas inlet (typically called the “primary”) while the smaer/lighter particles tend to be collected farther from the i

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(“backpasses”). The fineness, density, and carbon contefly ash may vary significantly from hopper to hopper.

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1.2.2 Beneficiated fly ash—Most fly ash produced from power plant is of suitable quality for collection and useconcrete. However, if the quality of some or all of the fly aproduced is less than required by specification or mastandards, methods may be used to beneficiate the flyThe properties which are commonly controlled by benefation are fineness and loss on ignition, LOI, (an indicatocarbon content). As noted in 1.2.1 above, segregation occuin various precipitator or baghouse hoppers. If the conand piping systems in the power plant allow it, fly ash canselectively drawn from those hoppers which contain higher quality fly ash.

Mechanical or air-classification equipment may be eployed to reduce the mean particle size of fly ash to mspecification or market requirements. Such classifiers eftively remove the denser particles, and may be adjustevary the amount of coarser ash removed. Depending osize, density, and distribution of particles containing carbthe LOI may be increased, decreased, or unchanged bclassification technique. A typical centrifugal classifier stallation (one classifier) could beneficiate 54 to 91 (60,000 to 100,000 tons) of classified material per year.

Technology is now being developed to reduce the cacontent of fly ashes. Electrostatic separation (Whitlo1993) and carbon burnout techniques (Cochran and B1993) are considered effective in reducing the loss on ition of fly ash without deleterious effects on its other propties.

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CHAPTER 2—FLY ASH COMPOSITION

2.1—GeneralFly ash is a complex material consisting of heterogene

combinations of amorphous (glassy) and crystalline phaThe largest fraction of fly ash consists of glassy spheretwo types, solid and hollow (cenospheres). These glphases are typically 60 to 90 percent of the total mass oash with the remaining fraction of fly ash made up of a vety of crystalline phases. These two phases are not comly separate and independent of one another. Rathercrystalline phases may be present within a glassy matrattached to the surface of the glassy spheres. This uniphases makes fly ash a complex material to classify characterize in specific terms.

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2.2—Chemical compositionThe bulk chemical composition has been used by AS

C 618 to classify fly ash into two types, Class C and ClasThe analytic bulk chemical composition analysis used totermine compliance with ASTM C 618 does not addressnature or reactivity of the particles. This type of analysiused as a quality assurance tool. Minor variations in chemical composition of a particular fly ash do not relaterectly to the long-term performance of concrete containthat fly ash. Although the constituents of fly ash are not tically present as oxides, the chemical composition of fly

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is so reported. The crystalline and glassy constituents thmain after the combustion of the pulverized coal are a reof materials with high melting points and incombustibility

Wide ranges exist in the amounts of the four principal cstituents, SiO2 (35 to 60 percent), Al2O3 (10 to 30 percent)Fe2O3 (4 to 20 percent), CaO (1 to 35 percent). The sumthe first three constituents (SiO2, Al2O3, and Fe2O3) is re-quired to be greater than 70 percent to be classified aASTM Class F fly ash, whereas their sum must only exc50 percent to be classified as an ASTM Class C fly ash. CC fly ashes generally contain more than 20 percent of mrial reported as CaO; therefore the sum of the SiO2, Al2O3,and Fe2O3 may be significantly less than the 70 percent CF minimum limit.

The SiO2 content of fly ash results mainly from the clminerals and quartz in the coal. Anthracite and bitumincoals often contain a higher percentage of clay mineratheir incombustible fraction than do subbituminous and nite coals; therefore the fly ash from the high-rank coalsricher in silica. The siliceous glass is the primary contribufrom the fly ash to the pozzolanic reaction in concrete sit is the amorphous silica that combines with free lime water to form calcium silicate hydrate (C-S-H), the bindeconcrete.

The principal source of alumina (Al2O3) in fly ash is theclay in the coal, with some alumina coming from the orgacompounds in low-rank coal. The types of clays foundcoal belong to three groups of clay minerals:

Smectite Na(Al5,Mg)Si12O30(OH)6 ⋅ nH2OIllite KAl 5Si7O20(OH)4Kaolinite Al 4Si4O10(OH)8Northern lignites typically contain a sodium smecti

whereas bituminous coal typically contains only memberthe illite group and kaolinite. This difference in types of cexplains the lower Al2O3 in low-rank coal fly ash. From thalumina/silica ratios of smectite, 0.35, illite, 0.61, and olinite, 0.85, it is clear why lignite fly ashes typically conta40 percent less analytic Al2O3 than bituminous fly ashes.

The Fe2O3 content of fly ash comes from the presenceiron-containing materials in the coal. The highest concentions of iron-rich fly ash particles are between 30 and 60 µm,with the lowest iron contents in particles less than 15 µm.

The source of the materials reported as CaO in fly ascalcium, primarily from calcium carbonates and calcium sfates in the coal. High-rank coals, such as anthracite antuminous coal, contain smaller amounts of noncombusmaterials typically showing less than five percent CaO inash. Low-rank coals may produce fly ash with up to 35 cent CaO. The southern lignite coals found in Texas Louisiana show the least CaO of the low-rank coals, a10 percent.

The MgO in fly ash is derived from organic constituensmectite, ferromagnesian minerals, and sometimes doloThese constituents are typically minimal in high-rank cobut may result in MgO contents in excess of 7 percent inashes from subbituminous and northern lignites (lignite csources in North Dakota, Saskatchewan, and surroundin


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eas). Southern lignites (from Texas and Louisiana) hMgO contents of less than 2 percent.

The SO3 in fly ash is a result of pyrite (FeS2) and gypsum(CaSO4·H2O) in the coal. The sulfur is released as sulfur oxide gas and precipitated onto the fly ash or “scrubbfrom the flue gases, through a reaction with lime and alparticles.

The alkalies in fly ash come from the clay minerals aother sodium and potassium-containing constituents incoal. Alkali sulfates in northern lignite fly ash result from tcombination of sodium and potassium with oxidized pyrorganic sulfur and gypsum in the coal. McCarthy et (1988) reported that Na2O is found in greater amounts thaK2O in lignite and subbituminous fly ash, but the reverstrue of bituminous fly ash. Expressed as Na2O equivalent(percent Na2O + 0.658 x percent K2O) alkali contents aretypically less than 5 percent, but may be as high as 10 pein some high-calcium fly ashes.

The carbon content in fly ash is a result of incomplcombustion of the coal and organic additives used in thelection process. Carbon content is not usually determinerectly, but is often assumed to be approximately equal toLOI; however, ignition loss will also include any combinewater or carbon dioxide, CO2, lost by decomposition of hydrates or carbonates that may be present in the ash. Clfly ashes usually have loss on ignition values less than 1cent, but Class F fly ashes range from this low level to vaas high as 20 percent. Fly ashes used in concrete typihave less than 6 percent LOI; however, ASTM C 618 pvides for the use of Class F fly ash with up to 12.0 percLOI if either acceptable performance records or laboratest results are made available.

Minor elements that may be present in fly ash incluvarying amounts of titanium, phosphorus, lead, chromiuand strontium. Some fly ashes also have trace amounts oganic compounds other than unburned coal. These additcompounds are usually from stack additives and are cussed in a subsequent section.

Table 2.1 gives typical values of North American fly asbulk chemical composition for different sources. Other rerences that provide detailed chemical composition data

Table 2.1—Example bulk composition of fly ash with coal sources

Bituminous Subbituminous Northern Lignite Southern Lignite

SiO2, percent 45.9 31.3 44.6 52.9

Al2O3, percent 24.2 22.5 15.5 17.9

Fe2O3, percent 4.7 5.0 7.7 9.0

CaO, percent 3.7 28.0 20.9 9.6SO3, percent 0.4 2.3 1.5 0.9

MgO, percent 0.0 4.3 6.1 1.7

Alkalies,* percent 0.2 1.6 0.9 0.6

LOI, percent 3 0.3 0.4 0.4Air permeability fine-ness, m2/kg

403 393 329 256

45 µm sieve retention,percent

18.2 17.0 21.6 23.8

Density, Mg/m3 2.28 2.70 2.54 2.43

* Available alkalies expressed as Na2O equivalent.

also available (Berry and Hemmings, 1983; McCarthy e1984; Tikalsky and Carrasquillo, 1992).

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2.3—Crystalline compositionFrom the bulk chemical composition of fly ash a divis

can be made between the phases in which these checompounds exist in fly ash. Developments in the techniqof quantitative X-ray diffraction (XRD) analysis have mait possible to determine the approximate amounts of cryline material in fly ash (Mings et al., 1983; Pitt and Demi1983; McCarthy et al., 1988).

Low-calcium fly ashes are characterized by having orelatively chemically inactive crystalline phases, namquartz, mullite, ferrite spinel, and hematite (Diamond, pez-Flores, 1981). High-calcium fly ash may contain thfour phases plus anhydrite, alkali sulfate, dicalcium silictricalcium aluminate, lime, melilite, merwinite, periclasand sodalite (McCarthy et al., 1984). A list of crystallicompounds found in fly ash is given in Table 2.2.

Alpha quartz is present in all fly ash. The quartz is a reof the impurities in the coal that failed to melt during cobustion. Quartz is typically the most intense peak in theray diffraction (XRD) pattern, but this peak is also subjecthe most quantitative variability.

The crystalline compound mullite is only found in sustantial quantities in low-calcium fly ashes. Mullite formwithin the spheres as the glass solidifies around it. It islargest source of alumina in fly ash. It is not normally cheically reactive in concrete.

In its purest form magnetite (Fe3O4) is the crystallinespinel structure closest to that found in fly ash. A slight crease in the diffraction spacing of ferrite spinel is detethrough XRD. Stevenson and Huber (1987) used a scanelectron microscope (SEM) electron probe on a magneticseparated portion of the fly ash to determine that the cauthis deviation is the Mg and Al substitution into the structof this phase as an iron replacement. The ferrite spinel pfound in fly ash is not chemically active. Hematite (Fe2O3),formed by the oxidation of magnetite, is also present in sfly ashes; it too is not chemically active.

Coal ashes containing high calcium contents often conbetween 1 and 3 percent anhydrite (CaSO4). The calcium


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Table 2.2—Mineralogical phases in fly ash

Mineral name Chemical composition

Thenardite (Na,K)2SO4

Anhydrite CaSO4

Tricalcium Aluminate (C3A) Ca3Al2O6

Dicalcium silicate (C2S) Ca2SiO4

Hematite FE2O3

Lime CaOMelilite Ca2(Mg,Al)(Al,Si)2O7

Merwinite Ca3Mg(SiO2)2Mullite Al6Si2O3

Periclase MgOQuartz SiO2

Sodalite structures Na8Al8Si6O24SO4

Ca2Na6Al6Si6O24(SO4)2

Ca8Al12O24(SO4)2Ferrite spinel Fe3O4

Portlandite Ca(OH)2

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acts as a “scrubber” for SO2 in the combustion gases anforms anhydrite. Crystalline CaO, sometimes referred tfree lime, is present in most high-calcium fly ashes and be a cause of autoclave expansion. However, lime inform of Ca(OH)2,“slaked lime,” does not contribute to autclave expansion. Soft-burned CaO hydrates quickly does not result in unsoundness in concrete. However, hburned CaO, formed at higher temperatures hydrates slafter the concrete has hardened. Demirel et al., (1983pothesize that the carbon-dioxide rich environment of combustion gases cause a carbonate coating to form on ly burned CaO particles, creating a high-diffusion enebarrier. This barrier retards the hydration of the particle thereby increases the potential for unsoundness. If freeis present as highly-sintered, hard-burned material, therepotential for long-term deleterious expansion from its hydtion. Although there is no direct way to separate soft-burlime from the sintered lime, McCarthy et al., (1984) note twhen hard-burned lime is present it is often found in the ler grains of fly ash. If there is sufficient hard-burned CaOcause unsoundness it should be detected as excessiveclave expansion. Ca(OH)2 is also present in some high calcum fly ashes that have been exposed to moisture.

Crystalline MgO, periclase, is found in fly ashes wmore than two percent MgO. Fly ash from low-rank comay contain periclase contents as high as 80 percent oMgO content. The periclase in fly ash is not “free” Mgsuch as that found in some portland cements. Rathercrystalline MgO in fly ash is similar to the phase of Mgfound in granulated blast furnace slags in that it is nonrtive in water or basic solutions at normal temperatu(Locher 1960).

Phases belonging to the melilite group include:Gehlenite Ca2Al2SiO7

Akermanite Ca2MgSi2O7

Sodium-Melilite NaCaAlSi2O7

These phases have been detected in fly ash, but archemically active in concrete. Each of these phases canan Fe substituted for Mg or Al.

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Merwinite is a common phase in high-calcium fly ashand the early stages of the devitrification of Mg-containglasses. Northern lignites typically have higher MgO ctents and lower Al2O3 contents than subbituminous-coal ashes, allowing the merwinite phase to dominate oveC3A phase in the northern lignite fly ash. Merwinite is noreactive at normal temperatures.

The presence of C3A in high-calcium fly ash was confirmed by Diamond (1982) and others. The intense Xdiffraction peaks of this phase overlap those of the merwphase, making the quantitative interpretation difficult. Hoever, McCarthy et al., (1988) reported that the C3A phase isthe dominant phase in fly ashes with subbituminous-sources, and the merwinite phase is dominant in ligniteashes. Neither phase is present in low-calcium fly ashescementitious value of C3A contributes to the self-cementinproperty of high-calcium fly ashes. The C3A phase is ex-tremely reactive in the presence of calcium and sulfate in solution.

Phases belonging to the sodalite group form from mrich in alkalies, sulfate, and calcium and poor in silica. sean and hauyne compounds have been identified in flby McCarthy et al., (1988). Mather (1980) and others hfound tetracalcium trialuminate sulfate (C4A3S), the activeconstituent of Type K expansive cement. C4A3S reacts readily with water, lime and sulfate to form ettringite.

Among the other phases found in fly ash are alkali suand dicalcium silicate. Dicalcium silicate is a crystallphase which is present in some high-calcium fly ashes athought to be reactive in the same manner as C2S in portlandcement. Northern lignite fly ashes often contain crystalalkali sulfates such as thenardite and aphthitilite.

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ote

2.4—Glassy compositionFly ash consists largely of small glassy spheres wh

form while the burned coal residue cools very rapidly. Tcomposition of these glasses is dependent on the comtion of the pulverized coal and the temperature at which burned. The major differences in fly ash glass composilie in the amount of calcium present in the glass. Coal has only small amounts of calcium; e.g., anthracite and bminous or some lignite coals, result in aluminosilicate glafly ash particles. Subbituminous and some lignite coals lelarger amounts of calcium in the fly ash and result in calcaluminosilicate glassy phases (Roy et al., 1984). This caseen in the ternary system diagram shown in Fig. 2.1. Thenormalized average glass composition of high-calciumash plots within the ranges where anorthite to gehlenitethe first phases to crystallize from a melt, whereas the lcalcium fly ashes fall within the regions of the diagrawhere mullite is the primary crystalline phase. It is widebelieved that the disordered structure of a glass resemthat of the primary crystallization phase that forms on coing from the melt. In fly ash, the molten silica is accompnied by other molten oxides. As the melt is quenched, thadditional oxides create added disorder in the silica gnetwork. The greater the disorder and depolymerization


k be

ndsof them-hio

n to fly

f re-

to flys arsesest ce-deregh-tivity

ing tosedm artiestent,

ris-mity thegenionrs, orrtedticle, orticletpo- hast in

the fly-ash glass structure, the less stable the networcomes.

In a simplified model the mass of crystalline compoucan be subtracted from the bulk mass to yield the mass glassy portion of the fly ash. Extending this model to chical compounds, the crystalline composition can be stoicmetrically subtracted from the bulk chemical compositioyield an average composition of the glass for any givenash. This is of importance when considering the level oactivity of a fly ash.

The ternary diagram shown in Fig. 2.1 may also be used illustrate the basic composition of the glassy portion ofash. Fly ashes which have calcium-rich glassy phaseconsiderably more reactive than aluminosilicate glasGlasses in fly ash with a devitrified composition furthfrom the mullite fields are most reactive within a portlandment-fly ash system because they have the most disornetwork. This would indicate that fly ash containing hicalcium or high-alkali glasses possess a greater reacthan low-calcium or low-alkali fly ashes.

Fig. 2.1—CaO-SiO2 — Al2O3 ternary system diagram

nsityed,

hardnce, fly

t with col-

esulteme en

ribu-uc-aratesthe

wa-

ntsarser

cipi-ete, par-

2.5—Physical propertiesThe shape, fineness, particle-size distribution, and de

of fly ash particles influence the properties of freshly mixunhardened concrete and the strength development ofened concrete. This is primarily due to the particle influeon the water demand of the concrete mixture. In additionashes produced at different power plants or at one plandifferent coal sources may have different colors. Fly ashor and the amount used can influence the color of the ring hardened concrete in the same way as changes in cor fine aggregate color. Fly ash color is generally not an

-

e

-

gineering concern, unless aesthetic considerations relatthe concrete require maintaining a uniform color in expoconcrete. However, a change in the color of an ash froparticular source may be an indicator of changed propedue to changes in coal source, carbon content, iron conor burning conditions.

e.

d

-

2.5.1 Particle shape—Particle size and shape charactetics of fly ash are dependent upon the source and uniforof the coal, the degree of pulverization prior to burning,combustion environment (temperature level and oxysupply), uniformity of combustion, and the type of collectsystem used (mechanical separators, baghouse filteelectrostatic precipitators). Lane and Best (1982) repothat the shape of fly ash particles is also a function of parsize. The majority of fly ash particles are glassy, solidhollow, and spherical in shape. Examples of fly ash parshapes are shown in Fig. 2.2 and 2.3. Fly ash particles thaare hollow are translucent to opaque, slightly to highly rous, and vary in shape from rounded to elongated. Itbeen shown that the intergrinding of fly ash with cementhe production of blended cement has improved its conttion to strength (EPRI SC-2616-SR). Grinding further redes particle size, breaks up cenospheres, and sepparticles which have surface attractions. However, if mixture of fly ash and cement clinker is ground too fine, ter requirements can be increased.

-nt

-

2.5.2 Fineness—Individual particles in fly ash range isize from less than 1 µm to greater than 1 mm. In older planwhere mechanical separators are used, the fly ash is cothan in more modern plants which use electrostatic pretators or bag filters. In fly ash suitable for use in concrASTM C 618 states that not more than 34 percent of the


Fig. 2.2—Fly ash at 4000 magnification

Fig. 2.3—Fly ash showing plerospheres at 2000 magnification

lareddiny b

n itsuls ce

sh,ce ton of-velyand

430ility5),from

ticles should be retained on the 45-µm (No. 325) sieve. The45-µm (No. 325) sieve analysis of fly ash from a particusource will normally remain relatively constant, providthere are no major changes in the coal source, coal grinprocess operations, and plant load. Minor variations maexpected due to sampling techniques.

Fineness of a specific fly ash may have an influence operformance in concrete. Lane and Best (1982) used reof tests by ASTM C 430, 45-µm (No. 325) sieve fineness, aa means to correlate the fineness of Class F fly ash withtain concrete properties.

g,e

sts

r-

Their data indicate that for a particular source of fly aconcrete strength, abrasion resistance, and resistanfreezing and thawing are direct functions of the proportiothe fly ash finer than the 45µm (No. 325) sieve. They concluded that fineness within a particular source is a relaticonsistent indicator of fly ash performance in concrete that performance improves with increased fineness.

Fly ash fineness test methods other than the ASTM C45-µm (No. 325) sieve procedure are the air-permeabtest (ASTM C 204), the turbidimeter method (ASTM C 11and the hydrometer method. Fineness values obtained


oceed bair- deby areacgleigh-luetri-eenttribuhat

of

mos- of-

ondheritiesfew-in th

ainn ispera- ac-ed.beckand of tem-he re-

s itce,on- com- the (c)s of

ent; anding ofcon-

ghcept-cs,

these three tests can differ widely depending on the prdure used, and the test results are also strongly influencthe density and porosity of the individual particles. The permeability test procedure provides a rapid method fortecting changes. Increased surface area as determined permeability tests in many cases correlates with higher tivity, especially when comparing ashes from a sinsource. Exceptions to this trend are found with some hcarbon fly ashes, which tend to have high fineness vawhich may be misleading. Useful information on size disbution of particles finer than 45-µm (No. 325) sieve can bobtained by sonic sifting and by particle sizing equipmbased on laser scattering. Data on the particle size distion of several Class C and Class F fly ashes indicate tlarge percentage of particles smaller than 10µm had a posi-tive influence on strength (EPRI CS-3314).

2.5.3Density—According to Luke (1961), the density solid fly ash particles ranges from 1.97 to 3.02 Mg/m3 (123to 188 lb/ft3), but is normally in the range of 2.2 to 2.8 Mg/3

(137 to 175 lb/ft3). Some fly ash particles, such as cenpheres, are capable of floating on water. High density isten an indication of fine particles. Roy, Luke, and Diam(1984) indicate that fly ashes high in iron tend to have higdensities and that those high in carbon have lower densASTM Class C fly ashes tend to have finer particles and er cenospheres; thus their densities tend to be higher, range of 2.4 to 2.8 Mg/m3 (150 to 175 lb/ft3).

al-t o

ateion thshtherateon. hyx-

atexedmd-le

encashThed thta,ce-ea

eacagery

s of

n in-

dis-

hin

ofres

t iner than

-H-S-

t is ce-landl C-

ef-

usrete

2.6—Chemical activity of fly ash in portland cement con-crete

The principal product of the reactions of fly ash with ccium hydroxide and alkali in concrete is the same as thathe hydration of portland cement, calcium silicate hydr(C-S-H). The morphology of the Class F fly ash reactproduct is suggested to be more gel-like and denser thanfrom portland cement (Idorn, 1983). The reaction of fly adepends largely upon breakdown and dissolution of glassy structure by the hydroxide ions and the heat geneduring the early hydration of the portland cement fractiThe reaction of the fly ash continues to consume calciumdroxide to form additional C-S-H as long as calcium hydroide is present in the pore fluid of the cement paste.

Regourd (1983) indicated that a very small, immedichemical reaction also takes place when fly ash is miwith water, preferentially releasing calcium and aluminuions to solution. This reaction is limited, however, until aditional alkali or calcium hydroxide or sulfates are availabfor reaction. The amount of heat evolved as a consequof the reactions in concrete is usually reduced when fly is used together with portland cement in the concrete. rate of early heat evolution is reduced in these cases antime of maximum rate of heat evolution is retarded (Meh1983; Wei, et al., 1984). When the quantity of portland ment per unit volume of concrete is kept constant, the hevolved is increased by fly ash addition (Mehta, 1983).

Idorn (1984) has suggested that, in general, fly ash rtion with portland cement in modern concrete is a two-streaction. Initially, and during the early curing, the prima

-y

-ir--

s

-a

.

e

reaction is with alkali hydroxides, and subsequently the mreaction is with calcium hydroxide. This phase distinctionot apparent when research is conducted at room temture; at room temperature the slower calcium-hydroxidetivation prevails and the early alkali activation is minimizAs was shown to be the case for portland cement by Ver(1960), the pozzolanic reaction of fly ashes with lime water follows Arrhenius’ law for the interdependencetemperatures and the rates of reaction. An increase inperature causes a more than proportionate increase in taction rate.

Clarifying the basic principles of fly ash reaction makepossible to identify the primary factors which, in practiwill influence the effectiveness of the use of fly ash in ccrete. These factors include; (a) the chemical and phaseposition of the fly ash and of the portland cement; (b)alkali-hydroxide concentration of the reaction system;the morphology of the fly ash particles; (d) the finenesthe fly ash and of the portland cement; (e) the developmof heat during the early phases of the hydration process(f) the reduction in mixing water requirements when usfly ash. Variations in chemical composition and reactivityfly ash affect early stage properties and the rheology of crete (Roy, Skalny, and Diamond, 1982).

It is difficult to predict concrete performance throucharacterization of fly ashes by themselves. Fly ash acability with regard to workability, strength characteristiand durability must be investigated through trial mixtureconcrete containing the fly ash.

f

at

d

-

e

e

2.7—Future research needsFuture research needs in the area of fly ash compositio

clude:a) better understanding of the effects of particle-size

tributionb) determining the acceptable levels of variation wit

the chemical and phase compositionc) clarifying the role of carbon particles as a function

their size and adsorption capability for chemical admixtud) identifying the chemically active aluminate presen

some fly ashes that causes such ashes to increase rathto reduce the severity of sulfate attack on concrete.

e) determining the minimum effective C ratio of C-Sas this allows more pozzolanic silica to be converted to CH by combination with a given amount of calcium ion thareleased to the pore fluid by the hydration of portlandment. If one uses 60 percent fly ash with 40 percent portcement will there be enough calcium ion to make usefuS-H out of all the silica in the cement and in the fly ash?

f) characterizing of glass phases of fly ash and theirfect on pozzolanic properties

t

-

CHAPTER 3—EFFECTS OF FLY ASHON CONCRETE

3.1—Effects on properties of fresh concrete3.1.1Workability—The absolute volume of cement pl

fly ash normally exceeds that of cement in similar conc


ashd is

ene inicity in

sat

asteash re4)

lumndin oy oftai

e thetingwet ofauseface,situa-lts inuchr too

dte ofal-in air-maypar- innt,

mixtures not containing fly ash. This is because the fly normally is of lower density and the mass of fly ash useusually equal to or greater than the reduced mass of cemWhile it depends on the proportions used, this increaspaste volume produces a concrete with improved plastand better cohesiveness (Lane, 1983). In addition, thecrease in the volume of fines from fly ash can compenfor deficient aggregate fines.

Fly ash changes the flow behavior of the cement p(Rudzinski, 1984); the generally spherical shape of fly particles normally permits the water in the concrete to beduced for a given workability (Brown, 1980). Ravina (198reported on a Class F fly ash which reduced the rate of sloss compared to non-fly ash concrete in hot-weather cotions. Class C fly ashes generally have a high proportioparticles finer than 10-µm (EPRI CS-3314), which favorablinfluences concrete workability. Data on the rheologyfresh fly ash-cement-water mixtures was reviewed in deby Helmuth (1987).

n-g b

oween,

ng onountith

oint air

3.1.2 Bleeding—Using fly ash in air-entrained and noair-entrained concrete mixtures usually reduces bleedinproviding greater surface area of solid particles and a lwater content for a given workability (Idorn and Henriks1984).

eienconrtardines tionpum

aseoneere

rac-in-Thecar-les

3.1.3 Pumpability—Improved pumpability of concretusually results when fly ash is used. For mixtures deficin the smaller sizes of fine aggregate or of low cement tent, the addition of fly ash will make concrete or momore cohesive and less prone to segregation and bleeFurther, the spherical shape of the fly ash particles servincrease workability and pumpability by decreasing frictbetween particles and between the concrete and the line (Best and Lane, 1980).

hent isF flyysetient, alies ashash

giveing, Th de-ede acn f

umptere

on, fil-orouscingill,

dmix-tent

vee re-

pec-ith

flyuffer

sus-ed tofor-

r ad-gerrms,

3.1.4Time of setting—The use of fly ash may extend ttime of setting of concrete if the portland cement contereduced. Jawed and Skalny (1981) found that Class ashes retarded early C3S hydration. Grutzeck, Wei, and Ro(1984) also found retardation with Class C fly ash. The ting characteristics of concrete are influenced by amband concrete temperature; cement type, source, contenfineness; water content of the paste; water soluble alkause and dosages of other admixtures; the amount of flyand the fineness and chemical composition of the fly (Plowman and Cabrera, 1984). When these factors are proper consideration in the concrete mixture proportionan acceptable time of setting can usually be obtained.actual effect of a given fly ash on time of setting may betermined by testing when a precise determination is neor by observation when a less precise determination isceptable. Pressures on form work may be increased wheash concrete is used if increased workability, slower slloss, or extended setting characteristics are encoun(Gardner, 1984).

erres

t flyhiching

n of

lerriod100

3.1.5Finishability—When fly ash concrete has a longtime of setting than concrete without fly ash, such mixtushould be finished at a later time than mixtures withouash. Failure to do so could lead to premature finishing, wcan seal the bleed water under the top surface creat

t.

-e

-

plane of weakness. Longer times of setting may increasprobability of plastic shrinkage cracking or surface crusunder conditions of high evaporation rates. Using very mixtures containing fly ashes with significant amountsvery light unburned coal particles or cenospheres can cthese particles to migrate upward and collect at the surwhich may lead to an unacceptable appearance. Some tions are encountered when the addition of fly ash resustickiness and consequent difficulties in finishing. In scases the concrete may have too much fine material ohigh an air content.

p-f

l

yr

t-

g.o

p

-tnd;;

n

e

d-

ly

d

a

3.1.6Air entrainment—The use of fly ash in air-entraineconcrete will generally require a change in the dosage rathe air-entraining admixture. Some fly ashes with LOI vues less than 3 percent require no appreciable increase entraining admixture dosage. Some Class C fly ashes reduce the amount of air-entraining admixture required, ticularly for those with significant water-soluble alkaliesthe fly ash (Pistilli, 1983). To maintain constant air conteadmixture dosages must usually be increased, dependithe carbon content as indicated by LOI, fineness, and amof organic material in the fly ash. When using a fly ash wa high LOI, more frequent testing of air content at the pof placement is desirable to maintain proper control ofcontent in the concrete.

Required air-entraining admixture dosages may increwith an increase in the coarse fractions of a fly ash. In laboratory study, separate size fractions of a fly ash wused in a series of mortar mixtures with only one size ftion per mixture. The finer fractions required less air-entraing admixture than the total ash sample (Lane, 1983). coarse fraction usually contains a higher proportion of bon than the fine fraction. The form of the carbon particin fly ash may be very similar to porous activated carbwhich is a product manufactured from coal and used intration and adsorption processes. In concrete, these pparticles can adsorb air-entraining admixtures, thus redutheir effectiveness (Burns, Guarnashelli, and McAsk1982). Adjustments must be made as necessary in the ature dosage to provide concrete with the desired air conat the point of placement.

Meininger (1981) and Gebler and Klieger (1983) hashown that there appears to be a relationship between thquired dosage of air-entraining admixture to obtain the sified air content and the loss of air in fly ash concrete wprolonged mixing or agitation prior to placement. Thoseashes that require a higher admixture dosage tend to smore air loss in fresh concrete. When this problem is pected, air tests should be made as the concrete is placmeasure the magnitude of the loss in air and to provide inmation necessary to adjust properly the dosage level foequate air content at the time of placement. Meinin(1981) showed that once the mixture is placed in the fono further appreciable loss of air is encountered. Agitatiothe concrete is a prerequisite for loss of air to continue.

In one investigation dealing with air entrainment (Geband Klieger, 1983), the retention of air over a 90-min pein different fly ash concretes ranged from about 40 to


on tea-

owee airw 3.t no

perngthix-

izedellsh,ent

trainge inn th theighica-lemes.t cantectre inin thases de-

ntrolencenixe

n ber re-ate-

entrib-ete isuiv-nt orash.ndd bying

eport-cretereteand forearsighn theand.n at

aring,arly-

crete C flyashased-oodmirel

percent, as measured on the fresh concrete, expressedbasis of the initial air content. Air contents were also msured in the hardened concrete. This particular study shthat for conditions where the air reduction occurred, thcontent in the hardened concrete was not reduced belopercent. The spacing factor increased somewhat, buabove the accepted limit of 0.20 mm (0.008 in.).

The loss of air depends upon a number of factors: proties and proportions of fly ash, cement, fine aggregate, leof mixing or agitating time, and type of air-entraining admture used (Gaynor, 1980; Meininger, 1981). NeutralVinsol resin air-entraining admixtures did not perform wwith fly ashes having high LOI values. For a given fly athe most stable air content was achieved with the cemfine aggregate combinations that had the highest air-ening admixture requirement. On the other hand, a chanfly ash that requires a higher admixture dosage to obtaispecified air content is more likely to cause loss of air ifmixture is agitated or manipulated for a period of time. Hloss on ignition of fly ash is often, but not always, an indtor of the likelihood of air-loss problems; so far, the probseems to be confined to the lower CaO, Class F fly ash

The foam-index test (see Appendix) is a rapid test thabe used to check successive shipments of fly ash to dechange in the required dosage of air-entraining admixtuconcrete. The test is useful to predict needed changes amount of admixture, and if the foam-index value increby a large amount, it is an indicator that loss of air duringlivery and placement should be checked. For quality-copurposes a procedure can be adapted from the refer(Meininger, 1981; Gebler and Klieger, 1983) which, whused in a consistent manner, can be useful at ready-mconcrete plants.

n conr fly

ns onshi withsh. forininat 7 (Ab de-th by the80; in-

ashs ue in

ciengertra,tra

ctiveever,engthlian ce-shbyr

58)ncreter ex-aforoten--al-

.rt, as

earlyretestic-gth.r flyinalelas-

3.2—Effects on properties of hardened concrete3.2.1 Compressive strength and rate of strength gai—

Strength at any given age and rate of strength gain ofcrete are affected by the characteristics of the particulaash, the cement with which it is used, and the proportioeach used in the concrete (EPRI CS-3314). The relatioof tensile strength to compressive strength for concretefly ash is not different from that of concrete without fly aCompared with concrete without fly ash proportionedequivalent 28-day compressive strength, concrete contaa typical Class F fly ash may develop lower strength days of age or before when tested at room temperaturedun-Nur, 1961). If equivalent 3-day or 7-day strength issired, it may be possible to provide the desired strengusing accelerators or water-reducers, or by changingmixture proportions (Bhardwaj, Batra, and Sastry, 19Swamy, Ali, and Theodor-Akopoulos, 1983). Test resultsdicate that silica fume can be used, for example, in flyconcrete to increase the early-age strength; simultaneouof silica fume and fly ash resulted in a continuing increas56- and 91-day strengths indicating the presence of sufficalcium ion for both the silica-fume reaction and the lonterm fly-ash reaction to continue (Carette and Malho1983). Also, Mukherjee, Loughborough, and Malho

he

d

5t

-

--

e

a

e

es

d

-

fp

g

-

(1982) have shown that increased early strengths caachieved in fly ash concrete by using high-range wateducing admixtures to reduce the water to cementitious mrial ratio to at least as low as 0.28.

After the rate of strength contribution of portland cemslows, the continued pozzolanic activity of fly ash contutes to increased strength gain at later ages if the concrkept moist; therefore, concrete containing fly ash with eqalent or lower strength at early ages may have equivalehigher strength at later ages than concrete without fly This higher rate of strength gain will continue with time aresult in higher later age strengths than can be achieveusing additional cement (Berry and Malhotra, 1980). Us28-day strengths as a reference, Lane and Best (1982) red strength increases of 50 percent at one year for concontaining fly ash, as compared with 30 percent for concwithout fly ash. Other tests, comparing concrete with without fly ash showed significantly higher performancethe concrete containing fly ash at ages up to 10 y(Mather, 1965). The ability of fly ash to aid in achieving hultimate strengths has made it a very useful ingredient iproduction of high-strength concrete (Blick, Peterson, Winter, 1974; Schmidt and Hoffman, 1975; Joshi, 1979)

Class C fly ashes often exhibit a higher rate of reactioearly ages than Class F fly ashes (Smith, Raba, and Me1982). Even though Class C fly ash displays increased eage activity, strength at later ages in high-strength conappears to be quite acceptable. Cook (1982) with Classash and Brink and Halstead (1956) with Class F fly showed that, in most cases, the pozzolanic activity increat all ages proportionally with the percent passing the 45µm(No. 325) sieve. Class C fly ashes typically give very gstrength results at 28 days. Cook (1981) and Pitt and De(1983) reported that some Class C fly ashes were as effeas portland cement on an equivalent-mass basis. Howcertain Class C fly ashes may not show the later-age strgain typical of Class F fly ashes. The effect of AustraClass F fly ash on strength development with differentments was demonstrated by Samarin, Munn, and A(1983) and is shown in Fig. 3.1. Strength development foClass C fly ash is shown in Fig. 3.2.

Both Brink and Halstead (1956) and Mather (19showed that changes in cement source may change costrengths with Class F fly ash as much as 20 percent. Foample, cements with alkali contents of 0.60 percent N2Oequivalent or more typically perform better with fly ash strength measured beyond 28 days. However, when ptially alkali-reactive aggregates are used in concrete, lowkali cement should be used, even if fly ash is also used

se

t

3.2.2 Modulus of elasticity—Lane and Best (1982) repothat the modulus of elasticity of Class F fly ash concretewell as its compressive strength, is somewhat lower at ages and a little higher at later ages than similar concwithout fly ash. The effects of fly ash on modulus of elasity are not as significant as the effects of fly ash on strenFig. 3.3 shows a comparative stress-strain relationship foash and non-fly ash concrete with 19.0-mm (3/4-in.) nommaximum size aggregate. The increase in modulus of


ash
Fig. 3.1—Rate of strength gain for different cementitious materials: Class F fly (Samarin, Munn, and Ashby 1983)
h part
Fig. 3.2—rates of strength gain of portland cement concrete and concrete in whicof the cement is replaced pound-for-pound with a Class C fly ash (Cook 1983)
all.teris

han

iche ofplusstress

ticity under these conditions with Class F fly ash is smThe study concludes that cement and aggregate charactics will have a greater effect on modulus of elasticity tthe use of fly ash (Cain, 1979).

intem-

odcreteo thereep

av-wer andwedame pro-

3.2.3 Creep—The rate and magnitude of creep strainconcrete depend on several factors including ambient perature and moisture conditions, strength of concrete, mulus of elasticity, aggregate content, the age of the conwhen loaded, and the ratio of the sustained stress tstrength at the time of loading. The effects of fly ash on c

-

-

strain of concrete are limited primarily to the extent to whfly ash influences the ultimate strength and the ratstrength gain. Concrete with a given volume of cement fly ash loaded at ages of 28 days or less to a constant will normally exhibit higher creep strain than concrete hing an equal volume of cement only, due to the lostrength of fly ash concrete at the time of loading (LaneBest, 1982). However, both Lane and Best (1982) shothat concrete with fly ash proportioned to have the sstrength at the age of loading as concrete without fly ash


Fig. 3.3—Stress-strain relationship at 90 days (TVA Technical Report CR-81-1)

spesturestrai yea

ns oalueea-

andgthse wilate-Yuawith

wasith i

n-f the of flyit im-

g, con-

hed es-

ntg onelop-t of

on ofe

duced less creep strain at all subsequent ages. When mens with and without fly ash are sealed to prevent moilosses, simulating conditions in mass concrete, creep values are essentially equal after loading at an age of 1(Ghosh and Timusk, 1981). When unsealed specimeequal strength were also loaded at 1 year, creep strain vfor concrete containing fly ash were only half those msured for concrete without fly ash.

Most investigations have shown that if concretes withwithout Class F fly ash having equivalent 28-day strenare equally loaded at the same age, the fly ash concretexhibit lower long-term creep due to the greater rate of age strengths gain common to most fly ash concrete. and Cook (1983) investigated the creep of concretes Class C fly ash. With 20 percent replacement, creepabout the same; at above 20 percent, creep increased wcreasing fly ash content.

teontadenvol-lowe in-th ofetegth flyt fly

el aretettle

uanti-truc-

theera-sh asown3).n of

s fore IIade

ateri- 3.1.tem-f hy-

3.2.4 Bond of concrete—The bond or adhesion of concreto steel is dependent on the surface area of the steel in cwith the concrete, the location of reinforcement, and the sity of the concrete. Fly ash usually will increase paste ume and may reduce bleeding. Thus, the contact at the interface where bleed water typically collects may becreased, resulting in improved bond. Development lengreinforcement in concrete is primarily a function of concrstrength. With proper consolidation and equivalent strenthe development length of reinforcement in concrete withash should be at least equal to that in concrete withouash. These conclusions about bond of concrete to stebased on extrapolation of what is known about concwithout fly ash. The bonding of new concrete to old is liaffected by the use of fly ash.

ci-

nrf

3.2.5 Impact resistance—The impact resistance of cocrete is governed largely by the compressive strength omortar and the hardness of the coarse aggregate. Useash affects the impact resistance only to the extent that proves ultimate compressive strengths.
s
ll

3.2.6 Abrasion resistance—Compressive strength, curinfinishing, and aggregate properties are the major factorstrolling the abrasion resistance of concrete (ACI 201.2R,210R). At equal compressive strengths, properly finisand cured concretes with and without fly ash will exhibitsentially equal resistance to abrasion.

n

n-

ct-

r

,

re

3.2.7 Temperature rise—The chemical reaction of cemewith water generates heat, which has an important bearinthe rate of strength development and on early stress devment due to differential volume change in concrete. Mosthis heat is generated during the early stages of hydratithe alite (substituted C3S) and C3A phases of the cement. Thrate of hydration and heat generation depends on the qty, fineness, and type of the cement, the mass of the sture, the method of placement, the temperature ofconcrete at the time of placement, and the curing tempture. The temperature rise can be reduced by using fly aa portion of the cementitious material in concrete, as shin Fig. 3.4 (Samarin, Munn, and Ashby, 1983; Mehta, 198As the amount of cement is reduced the heat of hydratiothe concrete is generally reduced (Mather, 1974). Valueheat of hydration at 3, 7, and 28 days for blends of Typportland cement and a Class F fly ash when the fly ash mup more than 50 percent by mass of the cementitious mal were reported (Mather, 1974) and are given in TableHowever, some Class C fly ashes do contribute to early perature rise in concrete (Dunstan, 1984). When heat o


rete
Fig. 3.4—Variation of temperature with time at the center of 15 cubic meter concblocks (Samarin, Munn, and Ashby, 1983)
s F. Inreez-ation

ctingity ofof ce- con-

Table 3.1—Heat of hydration of portlandcement/fly ash blends (Mather, 1974)Fly ash, percent of

cementitiousmaterial

Calories per gram

3 days 7 days 28 days

0 61 75 9152 31 42 6157 37 43 5665 35 42 5368 31 40 4971 29 36 48

ture59)

inate
dration is of critical concern, the proposed concrete mixshould be tested for temperature rise.
uresse ooperingtem110

ater tongedr at a

wa-avingrop-ide

3.2.8 Resistance to high temperatures—With respect tothe exposure of concrete to sustained high temperatCarette, Painter, and Malhotra (1982) indicate that the ufly ash in concrete does not change the mechanical prties of concrete in relation to similar concrete containonly portland cement when exposed to sustained high-perature conditions ranging from 75 to 600 C (170 to 1F).

withvoidof thLar conrial

ieve

in-t ePa

erly dif-rete

ach-ione thetruc-981;

ould an al-outrce-

rme-ss of

rein

3.2.9Resistance to freezing and thawing—The resistanceto damage from freezing and thawing of concrete made or without fly ash depends upon the adequacy of the air-system, the soundness of the aggregates, age, maturity cement paste, and moisture condition of the concrete (son, 1964). Because of the often slower strength gain ofcretes with Class F fly ash, more cementitious mate(cement plus fly ash) may be used in mixtures to achcomparable strength at 28 days.

Care should be exercised in proportioning mixtures tosure that the concrete has adequate strength when firsposed to cyclic freezing and thawing, that is, about 24 M(3500 psi) or more. When compared on this basis in propair-entrained concrete, investigators found no significantference in the resistance to freezing and thawing of conc

with and without fly ash [Lane and Best, (1982) for Clasfly ash and Majko and Pistilli, (1984)] for Class C fly ashaddition, Halstead (1986) exposed fly ash concrete to fing and thawing at very early ages and found no degradof performance as compared with control concrete.

,f-

-

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x-

3.2.10Permeability and corrosion protection—Concreteis permeable to water to the extent that it has interconnevoid spaces through which water can move. Permeabilconcrete is governed by many factors such as amount mentitious material, water content, aggregate grading,solidation, and curing efficiency. Powers et al., (19showed that the degree of hydration required to elimcapillary continuity from ordinary cement paste curedstandard laboratory conditions was a function of the watcementitious materials ratio and time. Required time rafrom 3 days at a water to cement ratio of 0.40 to 1 yeawater to cement ratio of 0.70.

Calcium hydroxide liberated by hydrating cement is ter-soluble and may leach out of hardened concrete, levoids for the ingress of water. Through its pozzolanic perties, fly ash chemically combines with calcium hydroxand water to produce C-S-H, thus reducing the risk of leing calcium hydroxide. Additionally, the long-term reactof fly ash refines the pore structure of concrete to reducingress of chloride ions. As a result of the refined pore sture, permeability is reduced (Manmohan and Mehta, 1and EPRI CS-3314).

Despite concern that the pozzolanic action of fly ash creduce the pH of concrete, researchers have found thatkaline environment very similar to that in concrete withfly ash remains to preserve the passivity of steel reinfoment (Ho and Lewis, 1983). Moreover, the reduced peability of fly ash concrete can decrease the rate of ingrewater, corrosive chemicals, and oxygen.

s3.2.11Reduction of expansion caused by alkali-silica

action (ASR)—The reaction between the siliceous glass


en fof ant

panate-e

grces

tiessi-highr re-m ofor-

sing for

n in are8 in

fly ash and the alkali hydroxides in the portland-cempaste consumes alkalies, which reduces their availabilityexpansive reactions with reactive aggregates. The use oequate amounts of some fly ashes can reduce the amouaggregate reaction and reduce or eliminate harmful exsion of the concrete (Farbiarz and Carrasquillo, 1987). Dfor mixtures containing eight different fly ashes with a cment of 0.66 percent Na2O equivalent and a highly reactivaggregate are shown in Fig. 3.5a and 3.5b. Often the amountof fly ash necessary to prevent damage due to alkali-aggate reaction will be more than the optimum amount ne

Fig. 3.5a—Mortar bar expansion versus percentage of cement replaced for allhighly reactive aggregate mixtures containing fly ash with less than 1.5 percentalkalies

Fig. 3.5b—Mortar bar expansion versus percentage of cement replaced for all highlyreactive aggregate mixtures containing fly ash with more than 1.5 percent alkalies

trd- of-

a

e--

sary for improvement in strength and workability properof concrete. Fig. 3.5b illustrates the phenomena of a pesmum level, where particular replacement levels of some alkali fly ashes increase the problem of ASR and higheplacement levels of the same fly ash reduce the probleASR. The pessimum level of a particular fly ash is an imptant consideration when selecting mixture proportions upotentially reactive aggregates. The available methodspreventing harmful expansion due to alkali-silica reactioconcrete containing fly ash when reactive aggregatesused include: (a) use of a pozzolan meeting ASTM C 61


r (b exen

li-sis thctivkali91)me

hta, there-n thesiveesh-theaO

012

a sufficient amount to prevent excessive expansion, othe use of blended cement demonstrated to control ASRpansion using ASTM C 595 and C 1157 (Portland CemAssociation, 1994). Several recent case studies of alkaica reactions in concrete suggest that some aggregatepass the current ASTM limits may cause deleterious reaity in the course of a number of years, even with low-alcement (Farbiaz and Carrasquillo, 1987; Snow, 19Therefore, Class F fly ash at 20-25 percent mass replacemay be used as a general preventive measure.

lyuren paon-atete,

ons. Eve sthe pes-992ininttacix-

n.icaosetionsuch reagethe

e-sheatly

h albinace t sul-e)flyhe f5 to

d bycur-eriade-emien

ashssednt-per-

iv-en-

and. InmtestTM ce-cor-

fate. Fly

ay

ison-te. In paste thent re-cretesh-rying ash Sy-con-

ingxter-eactsthe

of flyce byelpscon-i and

to con-icingave-salts

cified that per-y beErn-

3.2.12Sulfate resistance—As a general rule, Class F fash can improve the sulfate resistance of concrete mixtThe increase in sulfate resistance is believed to be due ito the continued reaction of fly ash with hydroxides in ccrete to continue to form additional calcium silicate hydr(C-S-H), which fills in capillary pores in the cement pasreducing permeability and the ingress of sulfate solutiThe situation with Class C fly ash is somewhat less clearidence suggests that some Class C fly ashes may reducfate resistance when used in normal proportions. K. Ma(1982) found that several Class C fly ashes used at 30cent replacement of several high C3A cements made the sytem less sulfate resistant. Tikalsky and Carrasquillo (11993) and Dunstan (1976) showed that concrete contasome high calcium fly ashes are susceptible to sulfate aand generally higher volumes of high calcium fly ash mtures have a greater susceptibility to sulfate deterioratio

Deterioration due to sulfate attack depends on chemreactions which yield products of greater volume than thof the original reactants, resulting in expansion. A reacoccurs between the sulfates (usually of external origin, as sulfate-bearing soils or sulfate-rich groundwater) andactive phases producing calcium sulfoaluminates. Damdue to this reaction can be reduced by minimizing amount of C3A (tricalcium aluminate) in the concrete. Dikou (1975) and Pierce (1982) established that certain fly aused in concrete under wetting and drying conditions greimprove the sulfate resistance of concretes made wittypes of cement. The cements and cement-fly ash comtions studied indicated a descending order of resistansulfate attack: (a) Type V plus fly ash - most resistant tofate; (b) Type II plus fly ash; (c) Type V; (d) Type II; (Type I plus fly ash; and (f) Type I - least resistant. All ashes used in this study were Class F, and the ratios of tash to total cementitious material by mass varied from 125 percent.

The sulfate resistance of fly ash concrete is influencethe same factors which affect concrete without fly ash: ing conditions, exposure, and water-to-cementitious matratio. The effect of fly ash on sulfate resistance will be pendent upon the class, amounts, and the individual chcal and physical characteristics of the fly ash and cemused.

An indicator of the relative sulfate resistance of a fly is the “R-value” developed by Dunstan (1980) and discuby Pierce (1982). The “R-value” is the ratio of the perceage of calcium oxide minus 5 percent (CaO percent-5 cent) to the percentage iron oxide (Fe203) in a fly ash, based

)-

tl-at-

.nt

s.rt

.-ul-rr-

,g

on the bulk chemical analysis. More recent research (Me1986; Tikalsky and Carrasquillo, 1993) has shown thatR-value is not a definitive method for predicting sulfate sistance. They found that sulfate resistance depended oamount of reactive alumina and the presence of expanphases in the fly ash and not as strongly influenced by F203

as indicated by the R factor. Generally, ASTM C 618 fly aes with less than 15 percent CaO content will improve sulfate resistance of concrete. Fly ashes with more Cshould be tested for sulfate expansion using ASTM C 1or USBR Test 4908.

The maximum sulfate resistance will be achieved in a gen exposure and situation by employing a low water-cemtitious materials ratio, sulfate-resisting portland cement, fly ash which exhibits good sulfate-resistance qualitiesattempting to select the fly ash which will give the maximusulfate resistance to a concrete mixture, one should blends of cements and fly ashes using ASTM C 1012. ASC 1157, the performance-based specification for blendedment, sets a limit on expansion at 6 months (tested in acdance with C 1012) of 0.10 percent for moderate sulresistance and 0.05 percent for high sulfate resistanceashes with large amounts of chemically active alumina madversely affect sulfate resistance.
k
l

-

s

3.2.13Drying shrinkage—Drying shrinkage of concrete a function of the fractional volume of paste, the water ctent, cement content and type, and the type of aggregathose cases where the addition of fly ash increases thevolume, drying shrinkage may be increased slightly ifwater content remains constant. If there is a water-conteduction, shrinkage should be about the same as conwithout fly ash. Davis et al., (1937) studied different fly acement mixtures and found no apparent differences in dshrinkage between concrete with up to 20 percent flycontent and non-fly ash concrete. Dunstan (1984) andmons and Fleming (1980) found that increased fly ash tent resulted in slightly less drying shrinkage.
l-o
ly

3.2.14Efflorescence—Efforescence is caused by leachof water soluble calcium hydroxide and other salts to enal concrete surfaces. The leached calcium hydroxide rwith carbon dioxide in air to form calcium carbonate, source of the white discoloration on concrete. The use ash in concrete can be effective in reducing efflorescenreducing permeability. This reduced permeability hmaintain the high alkaline environment in hardened crete. However, certain Class C fly ashes of high alkalsulfate contents may increase efflorescence.

l

-t

3.2.15Deicing scaling—Scaling of concrete exposeddeicing salts occurs when immature or nonair-entrainedcrete pavements are exposed to large quantities of desalts in a freezing and thawing environment. Concrete pments containing fly ash that are exposed to deicing should be air entrained and allowed to reach a spestrength or maturity. There is some laboratory researchindicates concrete containing 40 percent fly ash, as acentage of the total mass of cementitious material, mamore susceptible to scaling (Gebler and Klieger, 1986;


l re- andem-

zen and Carrasquillo, 1992; Johnston, 1994). Additionasearch is needed in this area.

nceture

atchshesifferprents.

testeate

agesallyent forpon

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suchtherand

ftennt tople, the typed toot-singresom-ng-

nalde toe

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CHAPTER 4—CONCRETE MIXTUREPROPORTIONING

4.1—GeneralThe most effective method for evaluating the performa

of a given fly ash in concrete and establishing proper mixproportions for a specific application is by use of a trial band testing program (ACI 211.1). Because different fly ahave different properties and concrete requirements dproportions for a given fly ash and cement cannot be scribed for all materials combinations and requiremeTherefore, a series of mixtures should be prepared and to determine the required total amount of cementitious mrials to obtain a specified strength with various percentof fly ash (Ghosh, 1976; Cook, 1983). Fly ash is normused at the rate of 15 to 35 percent by mass of total cemtious material. Larger proportions of fly ash may be usedmass concrete to reduce the likelihood of cracking ucooling, to improve sulfate resistance, to control alkaligregate reaction, or they may be used in other special acations (Malhotra, 1984; Haque et al., 1984).

nt oTMlan-ro-art flynge

ingounpropmeeralarly low is ande ad

r aashim-uc-uallellgesith

, in-rial

f cearlytiou de-

puteeteer tome-s amentent.or a it is ashhen

ter-te tous toi) ason-r. Aablyti-ton,ingte,en-

s ofper-atateray

por-cingater

4.2—Considerations in mixture proportioningFly ash may be used in concrete either as a constitue

an ASTM C 1157 blended cement or as specified in ASC 595 for portland-pozzolan cement, Type IP, pozzomodified portland cement, Type I (PM), or it may be intduced separately at the concrete mixer. When used as pblended cement, the proportions of portland cement toash are fixed by the cement manufacturer within the raprovided in the specification. In mixture proportioning usType IP cement or fly ash blended cement, the total amof the blended cement to achieve the desired concrete erties needs to be determined. When fly ash blended ceis obtained under ASTM C 1157 one may order it for genuse, moderate heat and sulfate resistance, high estrength, low heat of hydration, high sulfate resistance orreactivity with alkali reactive aggregate. When fly ashbatched separately the individual proportions of cementfly ash must be selected, and their relative ratio should bjusted as appropriate for each job situation.

It is usually possible to proportion concrete mixtures foparticular strength level with a blend of cement and fly in which the portland cement is less than it would be in silar strength mixtures not containing fly ash. If water-reding admixtures are also used, the cement content is usfurther reduced, as it is with non-fly ash concrete. Lovewand Washa (1958), Cannon (1968), and others have suged methods of proportioning concrete containing fly ash wand without chemical admixtures. When fly ash is useddications are that the total volume of cementitious mateused (cement plus fly ash) must exceed the volume oment used in cement-only mixtures to produce equal estrength and equal slump. The total mass of the cementimaterial and the optimum proportion of fly ash selected

,-

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of

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-

-

y

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-

s

pend on the class and quality of fly ash; the type, quality,alkali content of the portland cement; the presence of chical admixtures; placement conditions; and parameters as strength requirements, curing conditions, and weaconditions at the time of placement (Prusinski, Fouad Donovan; Majko and Pistilli, 1984).

The optimum use of fly ash and chemical admixtures orequires that adjustments be made in the ratio of cemefly ash between winter and summer conditions. For examin cold weather, a reduction in the fly ash percentage ofcementitious material may be prudent or a change in theof chemical admixture or dosage rate may be indicatepermit earlier finishing or form removal. Conversely, hweather concreting provides greater opportunities for uhigh proportions of fly ash since higher curing temperatutend to increase the relative strength of fly-ash concrete cpared to non-fly ash concrete at all ages, especially if loterm curing is provided.

Because use of fly ash normally contributes additiovolume to the concrete, certain adjustments must be maproportions. When following ACI 211.1, the volume of finaggregates should be adjusted to compensate for thicrease and for any change in volume of mixing water andvoid system. Ordinarily, a small reduction in the mixing wter demand can be expected when fly ash is used.

Most specifying agencies and concrete producers coman equivalent water-cement ratio (w/c) for fly ash concrby adding the cement + pozzolan by mass to get a wattotal cementitious material ratio by mass. This ratio is sotimes called the water to binder ratio (ACI 363R). This iconsistent approach since the fly ash in a blended cemeeting ASTM C 595 will be counted as part of the cemIn those cases where a maximum water-cement ratio minimum cement content is specified or recommended,generally accepted practice to count the mass of the flyas part of the amount of cementitious material required wseparately batched fly ash is used.

Where there is uncertainty concerning the proper wacementitious material ratio to use in air-entrained concreattain frost resistance of concrete, it may be advantageospecify that a strength level, such as 24 MPa (3500 psstipulated in ACI 308, be obtained prior to exposing the ccrete to freezing and thawing while saturated with wateminimum strength level is needed to achieve a reasonlow porosity of concrete and thus minimize capillary connuity in the paste (Powers et al., 1959; Buck and Thorn1967). This is the same approach used in the ACI BuildCode (ACI 318) for concrete with lightweight aggregasince it is difficult to calculate accurately the water to cemtitious material ratio in such mixtures.

Similar to non-fly ash concrete, the water requirementconcrete containing fly ash may be reduced by 5 to 10 cent by using conventional water-reducing admixtures. Dreported by Vollick (1959) indicate that the amount of wareduction obtained in concrete incorporating fly ash mvary depending on the specific fly ash used and its protion in the concrete. The use of high-range water-reduadmixtures in concrete containing fly ash may lead to w


argica

erias in078

cons ist o

nal-c-um

entment mays for.

ap-

reductions of 15 to 40 percent. The results appear to be lly dependent on type and dosage of admixture, chemcomposition of the cement, and the cementitious matcontent of the concrete. Cementitious material contentexcess of 385 kg/m3 (650 lb/yd3) usually are required for 2percent or greater water reduction. Ryan and Munn (19have reported that when a rapid rate of slump loss of crete incorporating high-range water-reducing admixtureexperienced, it is not appreciably affected by the amounfly ash used.

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CHAPTER 5—FLY ASH SPECIFICATIONS, TESTMETHODS, AND QUALITY ASSURANCE

5.1—IntroductionThe ASTM specification for fly ash is ASTM C 618, Sta

dard Specification for Coal Fly Ash and Raw or CalcinNatural Pozzolan for Use as a Mineral Admixture in Poland-Cement Concrete, and the standard sampling andmethods are in ASTM C 311, Standard Test MethodsSampling and Testing Fly Ash or Natural Pozzolans for as a Mineral Admixture in Portland-Cement Concrete. Thstandards are under the jurisdiction of ASTM Committee9. ASTM C 618 was originally published in 1968 to comband replace C 350 on fly ash and C 402 on other pozzofor use as mineral admixtures. Standard C 311 for sampand testing was published originally 1953. It is recommeed that specifiers of fly ash use the latest edition of thstandards. The following discussion is based on the reqments of ASTM C 618 and C 311 which were in effect attime this report was written. It is not intended to be a detareview of all requirements. The Canadian Standards Assation has a published standard for fly ash (CAN/CSA 23.5 - M 86). This standard is very similar to ASTM C 61with exceptions which will be noted in the following discusions.

ASTM C 618 classifies fly ashes as Class F, which mhave at least 70 percent (SiO2 + Al2O3 + Fe2O3); or Class C,which must have at least 50 percent of these compoundchemical analysis. Class C fly ash generally contains mCaO than Class F and has significant cementitious, as wpozzolanic, properties. The CaO content of Class C flyby chemical analysis is generally greater than 10 percenmay exceed 35 percent. The CaO is mainly combined iniceous and aluminous glass.

ASTM C 618 states that Class F is “normally producfrom burning anthracite or bituminous coal;” and Class C“normally produced from lignite or subbituminous coaMany power plants blend various types of coals for pogeneration. Some fly ashes produced from subbitumincoals and lignite meet all the physical and chemical requments of Class F are thus marketed as Class F. Most Clfly ashes meet the ASTM C 618 physical and chemicaquirements for Class C.

ht to

thatix-
5.2—Chemical requirements
As pointed out by Halstead (1981), early studies soug

e-ll

)-

f

str

sg-e-

i-

t

nes

hd-

s- F-

relate fly ash performance to individual chemical oxide aysis results for silica, alumina, or iron oxide with little sucess. Today many but not all specifications have a minimrequirement for the sum of the oxides, (SiO2 + Al2O3 +Fe2O3) (Manz, 1983). The intent is to assure that sufficireactive glassy constituents are present. A lower requireis necessary for Class C since the calcium oxide contentbe substantial, thus making it impossible in some casethe sum of (SiO2 +Al2O3 + Fe2O3) to be 70 percent or more

There has been a criticism of this sum of the oxidesproach to fly ash classification, and it has been suggethat fly ash should be classified by its CaO content (RLuke, and Diamond, 1984). The problem is illustrated inpaper by Majko and Pistilli (1984), where properties of fashes are reported. They referred to these ashes as "Clbecause of the good strength development obtained increte and CaO contents in the 9 to 25 percent range; hoer, four of the five fly ashes contained more than 70 per(SiO2 + Al2O3 + Fe2O3) which means they were chemicalclassified as Class F.

Virtually all specifications have a limit on the amount what is reported as sulfur trioxide (SO3) in fly ash. ASTM C618 has a limit of 5.0 percent for both classes; other specation limits range from 2.5 to 12.0 (Manz 1983). The sulin fly ash can affect the optimum amount of fly ash neefor maximum strength development and acceptable setime for the portland cement mixture in which it is used. upper limit is considered necessary to avoid an excess ofate remaining in the hardened concrete which could conute to harmful sulfate attack.

Limits on moisture content of fly ash are necessary tosure proper handling characteristics. Also, many Class Cashes will begin to hydrate in the presence of moistASTM C 618 limits moisture to 3.0 percent.

The maximum allowable loss on ignition in ASTM C 6is 6.0 percent for both Class C and Class F fly asCAN/CSA-A 23.5-M allows 12 percent for Class F andpercent for Class C. Some specifiers modify this limit tvalue lower than 6 percent, particularly where air-entraiconcrete is involved. The great majority of fly ashes frbase-load power plants are well below 6 percent loss onition, due mainly to the efficiency of operation requiredmake economical use of coal as an energy source. In special circumstances, a user may elect to use a Classash with up to 12 percent loss on ignition when acceptlaboratory or performance data are available.

Specification ASTM C 618 contains an optional chemirequirement on amount of available alkalies, expresseequivalent Na2O. This requirement limits the available alklies in Class F and Class C fly ashes to 1.5 percent maximHowever, fly ash with available alkalies greater than 1.5 cent may be used with reactive aggregate if laboratory show that deleterious expansion does not occur. Thesquirements are not appropriate unless the concrete wimade using reactive aggregates or unless it is knownhigher alkali levels interact adversely with chemical admtures (Halstead, 1981).


the-ect-iclem- andeea is

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ive re-notv-

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edthe

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3).ngin

e thin

for limad-ese of

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ionggre- Flyce the C

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ay pro-yoris-

d (4)

5.3—Physical requirementsFly ash fineness is controlled in most cases by limiting

amount retained on the 45-µm (No. 325) sieve by wet sieving. Reactivity of fly ash has been found to be related dirly to the quantity passing this sieve since the coarser partgenerally do not react rapidly in concrete. ASTM C 618 liits the amount retained to 34 percent for both Class FClass C fly ashes. Control of fineness has occasionally bspecified by surface area (air permeability). Surface arenormally reported by mass for portland cement and by ume for fly ash; the test results are not directly comparaThe relationship between fineness based on various denis shown in Table 5.1.

The strength activity index with portland cement is cosidered only as an indication of reactivity and does not dict the compressive strength of concrete containing theash. It does not necessarily bear any relation to the optimproportion of fly ash for use in concrete. The alternatstrength activity index with hydrated lime at 7 days hascently been dropped from ASTM C 618 because it is widely regarded as a significant indicator of quality. Howeer, tests conducted on consecutive samples of a given sof fly ash by a single laboratory using a single source of lcorrelate well with the results of other qualification tests.

In the past, the strength activity test with lime filled a nefor more rapid results on strength performance (7 days rathan 28 days). More recent revisions of ASTM C 618 hincluded a 7-day strength activity test with portland cemeThe 7-day C 618 test uses standard 23 C (73 F) laboracuring temperatures, whereas Canadian Standard CSAS-M specifies curing at 65 C (149 F) for 7 days.

Other specified and optional physical properties includ1. Water requirement of the mortar used in the strength

tivity test to assure that fly ash does not cause a largecrease in mixing water demand.

2. Soundness by measuring autoclave expansion or traction. A length change of 0.8 percent is the maximumlowed by ASTM C 618 for both fly ash classes. It is requithat if the fly ash will constitute more than 20 percent of cementitious material in the proposed concrete, the pused for autoclave testing shall contain the anticipated centage of fly ash. The test protects against the delayepansion that could occur if sufficient amounts of MgO apresent in the concrete as periclase, or CaO as hard-bucrystalline lime (Halstead, 1981; Pitt and Demirel, 198Bobrowski and Pistilli (1979) found no correlation amoautoclave expansion, SO3 content, and concrete strength their laboratory study.

3. Variability limits are given in ASTM C 618. Limits arspecified for both Class F and Class C fly ashes to keepvariation of specific gravity and fineness of the fly ash withpractical limits for shipments over a period of time. Also, fly ash used in air-entrained concrete there is an optionalit on the permitted variation of demand for air-entraining mixture caused by variability of the fly ash source. Thlimits are invoked to restrain the variability of propertiesconcrete containing fly ash.

s

n

.s

Table 5.1—Relationship between pa rticle size andsurface area

Equivalent surface area, m2/kg at variousdensities

Meanparticlediameter

µm

Surfacearea, m2/m3 2.0 Mg/m3 2.5 Mg/m3 3.0 Mg/m3 3.15 Mg/m3

2 3000 1500 1200 1000 9503 2000 1000 800 670 6304 1500 750 600 500 4805 1200 600 480 400 3806 1000 500 400 330 3207 860 430 340 290 2708 750 380 300 250 2409 670 330 270 220 210

e

r

y3

-

4. The optional Multiple Factor, applicable only to ClaF, is calculated as the product of LOI (percent) and amretained on the 45-µm (No. 325) sieve (percent). The maxmum value of 255 restricts sieve residue (less than 34cent) only when the loss on ignition exceeds 6 percent.

5. Increase in drying shrinkage of mortar bars at 28 dThis limit is applied only at the request of the purchaseshow whether the fly ash will cause a substantial increashrinkage in mortar bars as compared to bars with portcement only.

6. Reactivity with alkalies. Optional mortar-bar expanstests can be requested if a fly ash is to be used with an agate regarded to be deleteriously reactive with alkalies.ash has been recommended for use in concrete to redudamage from alkali-silica reaction (Snow, 1991). ASTM618 limits the actual expansion of potentially reactive aggate/paste combinations, whereas CSA-A 23.5-M demines the effect of fly ash in reducing expansion compared to portland cement only samples.

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te

5.4—General specification provisionsASTM C 618 requires that the purchaser or an author

representative have access to stored fly ash for the puof inspection and sampling and that the fly ash may be reed if it fails to meet any of the specified requirements.

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ed

e

-

5.5—Methods of sampling and testingASTM C 311 outlines the procedures to be used for s

pling and testing fly ash. For a number of test procedureference is made to other cement, mortar, or concrete for the body of the test procedure, with ASTM C 311 incating the modifications in proportions, preparation produres, or test parameters needed to accommodate flytesting. The three main divisions of the standard are spling methods, chemical analysis methods, and physicalprocedures.

Either individual grab samples or composite samples mbe used depending on the circumstances. The methodvides detailed procedures for sampling from: (1) convedelivering to bulk storage, (2) bulk storage at points of dcharge, (3) bulk storage by means of sampling tubes, anrailroad cars or trucks.


tureg thtand ceionsas,

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uctema

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ar-ne-heisticsples that

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ash) for oth-plet-

alityndi-n toimeribed

kingm ae or

thebe

Chemical test procedures involve determining moiscontent by drying to constant mass and then determininLOI. The latter requires igniting the dried sample to consmass in a muffle furnace at 750 ± 50 C using an uncovereporcelain crucible (not a platinum crucible as used forment testing). Many of the required chemical determinatare then made using procedures which are the same very similar to, those used in testing portland cement.

Physical tests on fly ash include density and amountained on the 45-µm (No. 325) sieve determined using ttest methods developed for portland cement. Soundnesstrength activity testing procedures are included in ASTM311 with reference to cement testing procedures wherepropriate.

Of all the tests conducted, the two which are most diffito obtain credible, repeatable, results are fineness strength activity with lime. In the fineness test, test sievesnot precisely manufactured to exactly 45 µm. The standardprocedure calls for calibrating sieves using a portlandment reference sample, and computing a correction fafor the sieve. Since the fly ash particles retained on thesieve tend to be much larger than 45 µm, large correctionfactors give inaccurate results. Sieves with small correcfactors give more accurate results. In the strength activitdex test with lime, results are highly dependent on the used by the laboratory. Since the performance of the limnot controlled by the test method standards, tests condby different laboratories on the same fly ash sample yield significantly different results. For many of the chemcal and physical tests on fly ash contained in ASTM C the precision and bias estimates have not been establis

nceamom-m is his-rmewom

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5.6—Source quality controlA company selling fly ash intended to be in conforma

with ASTM C 618 should have a quality control progrthat is technically and statistically sound. The first recmended step in starting a fly ash quality control prograto establish its quality history. The purpose of the qualitytory is to demonstrate that the fly ash consistently confoto specification and uniformity requirements. For a nsource of fly ash, at least six months of testing is recmended. This quality history should include monthly ASC 618 certification as well as at least 40 individual tessults for loss on ignition, 45-µm (No. 325) sieve residue, spcific gravity, and SO3. An analysis of these data by statistitechniques helps determine whether the proposed soufly ash is suitable for the intended use (Dhir, Apte, and Mday, 1981). After the quality history is established, source should be tested at least monthly to assure conconformance to ASTM C 618.

A quality control program should be established for eindividual source. Such programs may vary with coal tycollection systems, and other factors. The important chteristics of the particular source of fly ash should be demined and a quality control program established for source taking into account those characteristics and thquirements of specifications for its use in concrete. Tesfor critical requirements may be needed more freque

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than prescribed in ASTM C 311. For example, critical chacteristics of fly ashes may include: loss on ignition, finess, color, or SO3. However, all fly ashes may not have tsame critical characteristics nor may all these characterneed to be included in regular testing programs. Sammay also be taken periodically and stored in the eventfuture testing and evaluation is desirable.

An effective quality control program allows the fly asupplier to maintain test reports on the fly ash for demontion of product compliance with regard to the physicchemical, and variability requirements of ASTM or othspecial project performance requirements, as well as to itor variability of critical characteristics. Statistical evalutions of the test data provide the supplier with informationlong-term variations.

ASTM C 311 provides for tests to be conducted on fly samples representing not more than 360 Mg (400 tonscertain tests and not more than 1800 Mg (2000 tons) forers. Some of the tests require at least 28 days to be comed. Consequently, it is often desirable to establish a qucontrol program employing rapid testing techniques as icators of certain critical fly ash characteristics, in additioASTM compliance testing. Sampling and testing on a tschedule basis, in addition to the shipping basis prescby ASTM C 311, may be a useful part of the program.

Fly ash testing using rapid techniques is a basis for macontinual judgments as to the selection of fly ash frosource and determining its suitability for a desired end usdirecting it to waste disposal (see Section 5.8 and the Appen-dix for descriptions of rapid tests). In conjunction with quality control program, the fly ash supplier should knowledgeable about power plant operation and take ato exclude questionable fly ash when variations in the poplant operation may influence fly ash quality. The chemcomposition and fineness of fly ash from one source arelikely to vary significantly at a power plant where the csource is consistent, maintenance of the coal pulverizerfly ash collectors is satisfactory, and the load on the poplant is fairly constant.

The performance of fly ash in concrete is related toproperties and the variation of these properties with coning shipments from the source of supply. Variations in oingredients in the concrete will also affect the performaof the mixture. For Class F fly ash from a single coal southe properties that are most likely to affect its performancconcrete are fineness, loss on ignition, and autoclave exsion (Minnick, Webster, and Purdy, 1971). Significant prerties of Class C fly ash that affect performance in concinclude fineness, loss on ignition, autoclave expansion,the amounts of SO3, CaO, and alkalies present. Variabilityfly ash color should also be monitored since changes in may be of importance for architectural concrete applicatiFly ash color may also indicate changes in carbon contepower plant burning conditions, which may alter the permances of the fly ash, especially in air-entrained concre

McKerall, Ledbetter, and Teague (1981) have develoregression equations for fineness and specific gravity oashes produced in Texas from subbituminous coal and


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d intestcases

nite. These regression equations can be used to find cloproximations of fineness, CaO content, and specific gragiven the results of the tests on the 75µm (No. 200) sieve tesand a CaO heat evolution test described in the Appendi

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5.7—Start-up, oil, and stack additivesThe fly ash distributor and user should be aware of ch

es in the ash properties that may result from changes in er-plant operation, such as use of stack additives, flueconditioners, and changes in other aspects of produsuch as boiler start-up (Ravina, 1981). Changes in burand fly ash collection procedures at the power station affect fly ash quality. The use of oil (to supplement burnior stack additives, some of which may produce strong monia odors, needs to be detected rapidly. The additiosodium sulfate to reduce blinding of precipitators may afthe time of setting of concrete, especially when certainmixtures are used. Liaison between the fly ash supplierthe power station shift engineers, combined with frequrapid tests, should be used to detect problems early and vert questionable quality fly ash to waste disposal. Whecoal-boiler unit is first fired, oil is often used to help initiacombustion, and the ash may contain hydrocarbon resifrom the oil. In power plants where this is done during stup or under some other transient, short-term condition,fly ash collected during these brief oil burning perioshould not be used in concrete. There are also some otions — in the UK, for example — where oil is burned wcoal on a continuous basis. Fly ash from these operamay be suitable for concrete under certain circumstanparticularly in concrete which is not air-entrained where ctrol of admixture dosage is not a factor.

Materials are sometimes used by electric utilities durcoal burning and fly ash collection to improve the efficienof these operations. Materials termed “fireside additiv(EPRI CS-1318) are sometimes used in the burner to reSO3 emissions, reduce corrosion and fouling, and to imprthe collection efficiency of the electrostatic precipitatoFireside additives are used more in oil-fired boilers thacoal-fired plants.

Materials injected into the flue gas to enable the elecstatic precipitators to collect a greater proportion of theash are termed “flue gas conditioners” (EPRI FP-910). Fgas conditioners are often used in coal-burning power plaWhen these types of materials are used, however, the flmay contain a small amount of substances such as magammonium compounds, alkalies, or SO3. Prior to the use ofly ash containing an additive, the variability of the amoof additive used in the power plant or present in the fly and its effect in concrete should be carefully evaluated.

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5.8—Rapid quality control testsFly ash collection at a base load power plant usually

tinues around the clock, and because of limitations in stocapacity, decisions must be made fairly rapidly concernthe probable quality of the fly ash so that material that dnot meet requirements may be designated for other usdirected to waste disposal. Some of the properties spec

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in ASTM C 618 as well as other characteristics are usemaking these rapid fly ash quality judgments. Several methods have been devised to make daily, and in some hourly, quality estimates, if needed.

One or more of the rapid tests listed in the Appendix be used as indicators of quality. The principal objective idetermine by rapid tests if the fly ash meets pre-establiparameters for quality. These results should be supporteperiodic comparison with results of standard tests of theash and could be used in developing correlations betweeash characteristics and concrete performance. Dependithe objective of the testing they may be used by the flymarketer at the power plant or by the user to check shipmof fly ash for changes in properties or to predict air-entring admixture dosage or strength performance in concThe rapid testing procedures discussed in the Appendix

1. Loss on ignition2. Carbon content3. 45-µm (No. 325) sieve fineness4. Air-jet sieving5. Air-permeability fineness6. Color7. Density (specific gravity)8. Foam index test9. Organic material10. CaO content11. Hydrocarbons12. Ammonia

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CHAPTER 6—FLY ASH IN CONCRETECONSTRUCTION

6.1—Ready-mixed concreteA survey of the ready-mixed concrete industry in the U

ed States in 1989 indicated that, of the companies whsponded to the questionnaire, 92 percent use at least soash compared to 31 percent in 1983 (Justman, 1991).proximately 55 percent of the concrete produced contafly ash; as compared to 46 percent in 1983. Some of thesons for this substantial increase are: (a) technical ben(b) increased cost of energy to produce cement encourcost savings in concrete through the use of cement-flycombinations; (c) the increased use of high-strength conof 52 MPa (7500 psi) or greater which commonly requthe use of fly ash (Cook, 1981; Albinger, 1984); (d) increing availability of fly ashes meeting industry standards inUnited States and Canada; and (e) governmental policiecouraging the use of fly ash to the maximum extent pracble.

Many concrete producers use fly ash to overcome dciencies in aggregate grading or have developed mixtspecifically for pumping. This takes advantage of the caity of concrete containing fly ash to pump higher and furtat faster rates, and with less segregation. Ready-mixedcrete containing Class C fly ash was successfully pumpea 75-story office tower in Houston, Texas (Cook, 1982).

Very high strengths, up to 100 MPa (14,000 psi) in field and higher in the laboratory, have been used with


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tain Class C fly ashes. Class F fly ashes are also used instrength concrete because of the contribution to workaband long-term strength gain.

Class F fly ashes are used to mitigate the deleterioupansion associated with alkali-silica expansion. Aggregthat are otherwise unsuitable for use due to reactivity caused when a fly ash known to reduce alkali-silica expanis used at the proper proportion in the concrete mixture.

Albinger (1984) has stated that the decision to use ouse fly ash should be based on four factors: fly ash proties; effectiveness of the quality control program of the splier; ability to adjust to concrete changes, such as delfinishability and increased air-entraining admixture demaand cost effectiveness. The cost of additional equipmestore and batch fly ash is an expense which may be offsthe savings in material cost.

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6.2—Concrete pavementA 1992 EPRI study of 32 states found that all 32 states

mitted the use of fly ash in pavement concrete and permthe use of blended cements containing fly ash (EPRI 19Halstead (1981) summarized quality control and logproblems relating to the use of fly ash in concrete. Probwith the control of air entrainment and costs of transporfly ash long distances were identified as the principal drents to more extensive use. Franklin (1981) reportestudies in the United Kingdom considering the incorporaof fly ash in pavement concrete. In the United States, thof increased amounts of fly ash in highway constructiobeing encouraged because of the availability of qualityash in most areas and governmental policies on fundingrelates to the use of fly ash to the maximum extent prac(Cain, 1983). Hester (1967) reported on the use of fly aconcrete pavement and structures in Alabama. This swas found that for mixtures containing fly ash with reducement contents, higher flexural strengths were obtaineKansas, after 10 years of exposure and service, fly asduced, but did not eliminate, map-cracking and abnormapansion in a 1949 test road (Scholer, 1963; Stingley e1960; K. Mather and Mielenz, 1960). During the 1950s, nois, Nebraska, Wisconsin, Michigan, and Kentucky cstructed experimental pavements with fly ash concreevaluate strength, crack resistance, placing and finisqualities, and long-term wear resistance. All of these rare reported to have performed well.

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6.3—Mass concreteMass concrete was one of the first applications in wh

fly ash was used in the United States. Hungry Horse DMontana, completed in 1953, contains over 2.3 million m3 (3million yd3) of concrete and a total of 110,000 Mg (120,0tons) of fly ash. From that time until 1970, at least 100 mlocks and dams using fly ash were constructed under threction of either the Corps of Engineers or private engining firms. There are few mass concrete dams built in anyof the world that do not contain fly ash or natural pozzoin the concrete (Hyland, 1970). Large volumes of fly a

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have been used in roller-compacted concrete dams (Scer, 1982).

Use of fly ash can reduce the thermal stresses by redthe heat of hydration in mass concrete structures (NasseMarzouk, 1979; Blanks, Meissner, and Rawhauser, 1Carlson, Houghton, and Polivka, 1979). By using fly asconcrete in massive structures, it is possible to achieveduction in temperature rise (and reduce the risk of thecracking) without incurring the undesirable effects assoed with very lean mixtures; i.e., harshness, bleeding, tency to segregate, and tendency for increased permea(Price, 1982; Montgomery, Hughes, and Williams, 19Improved sulfate resistance and reduction of expansionto alkali-aggregate reaction provided by proper use of flyin concrete mixture are other important considerations inconstruction of mass concrete.

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6.4—Bulk handling and storageSince fly ash is normally of lower density than portland

ment, its bulk density should be considered when orderintaking inventory. Fly ash storage typically requires about40 percent more volume per unit mass than does portlanment; a 100 Mg (or tons) portland cement bin will hold ab70 to 75 Mg (or tons) of fly ash. Packaging in paper ba“big bags,” or other bulk containers may also reflect thdifferences in bulk density. The bulk density of fly ashbins or silos is generally between 880 and 1280 kg/m3 (55and 80 lb/ft3); whereas cement in bins and silos is generbetween 960 and 1500 kg/m3 (60 and 94 lb/ft3). Both fly ashand cement may have lowered bulk density immediatelyter conveying (Strehlow, 1973). Rail cars can not carrymuch mass of fly ash as cement. Bulk pneumatic tank trthat typically carry cement or fly ash are usually laenough in volume to receive a full legal load for over-hiway delivery. Occasionally, fly ashes with very low budensity may reduce the load that can be carried.

The spherical particle shape of fly ash, as well as sigcant quantities of very fine grains mean that fly ash willquire handling and storage facilities slightly different froportland cement. When aerated, fly ash tends to exhibit fluid handling characteristics, with an aerated angle ofpose of 10 to 15 deg. As a result, bins for storage of fly as well as transport systems (pneumatic or mechanical) be well sealed to prevent leakage. This characteristiccreases the possibility of leakage of fly ash from bins anlos.

Bins and silos intended for cement may be used to storash. Bins or silos should be large enough to receive at two deliveries. The fluid nature of aerated fly ash mayquire slightly different unloading techniques than portlacement. Due to the similar appearance of fly ash and cemit is prudent to color-code and label the fill pipes or to tother precautions to minimize the possibility of cross-ctamination. Care must also be taken to clearly identify whstorage compartments contain fly ash, and to establish per materials-management procedures (Gaynor, 1978). should be completely cleaned when they are being convto handle a different type of material. As with cement fr


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different mills, fly ash from different sources should notmixed in the same bin.

Since it is virtually impossible to detect fly ash contamition of a cement storage compartment by visually examinthe cement as batched or the concrete as mixed, caavoiding intermingling of cement and fly ash is of great portance. A separate silo for fly ash is preferred. Segmestorage bins containing fly ash and portland cement (in acent bins) should be separated by double bin wall with aspace between, to prevent fly ash and cement from flowtogether through a breach in a common wall; otherwiseash may move from one bin to the other through faulty wed connections, or through holes caused by wear. If ceand fly ash must be stored in different compartments ofsame bin or silo and are separated by a common divipartition, frequent inspections of the partition must be ma

Each storage bin and silo should be equipped with a ptive shutoff to control the flow of the fly ash to the weigbatcher. Rotary valves, rotary-valve feeders, and buttevalves are generally suitable for this purpose. A convental scissor gate may be used if it is well maintained. Indedent dust collectors on cement and fly ash bins, as showFig. 6.1 are recommended to prevent cross-contaminatio

Fig. 6.1—Cement and fly ash silo with separate dust col-lection systems

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6.5—BatchingWhen batching fly ash and cement at a concrete plant

usually not necessary to install separate weigh batchersash and cement may be weighed cumulatively in the sweigh batcher. Due to the lower density of fly ash, webatchers must be sized adequately to handle larger volof cementitious material. Cement should be weighed firsthat accidental overbatching of fly ash will not cause undbaching of cement (Gaynor, 1978). However, care mustaken to accurately batch the correct amounts of both ceand fly ash, since overbatching or underbatching may rein unacceptable variations in the properties of the plastichardened concrete.

To transport fly ash from bin to weigh batcher, methsuch as gravity flow, pneumatic or screw conveyors, orslides are most often used. The method depends on thetion of the fly ash bin relative to the weigh hopper. Fly a

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from overhead storage is normally conveyed by gravity for an air slide. If the fly ash storage is at nearly the sameas the weigh batcher, an air slide or a screw conveyor cused (see Figs. 6.2a and b). Since fly ash flows very easily,positive shut-off valve should be installed to insure overbatching does not result from fly ash flowing throuthe air slide or screw when the device is stopped. Fly asbe conveyed from lower level storage by pneumatic conor. During storage and batching, fly ash should be protefrom moisture (in the air, from condensation, or from clement weather) to avoid problems in handling and chain the fly ash characteristics.

Fig. 6.2(a)—Schematic of an air slide

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CHAPTER 7—FLY ASH IN CONCRETE PRODUCTS

7.1—Concrete masonry unitsThe manufacture of concrete masonry units typically

volves the use of a dry, harsh concrete mixture compainto molds with mechanical force. When demolded, thunits maintain their shape during handling and transportainto a curing environment. Fly ash has found widespreadin the manufacture of these products as a cementitious


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rial and aggregate mineral filler.Curing methods for masonry units include autoclave c

ing and atmospheric-pressure steam curing. Manufactuusing both curing systems are able to incorporate fly astheir concrete mixtures and obtain the required strengthaddition, they obtain better mold life, and products with iproved finish and texture, and sharper corners. Fly ashportedly gives added plasticity to the relatively harmixtures used in concrete masonry units (Belot, 1967). toclave curing, though not as common as in the past, isused to manufacture high quality masonry units. Concmasonry units cured in autoclaves show early strength eqalent to that of 28-day moist-cured strength and reductiovolume change in drying (Hope, 1981). The process utemperatures of 135 to 190 C (275 to 375 F) and pressu0.52 to 1.17 MPa (75 to 170 psi). These conditions typicallow for the use of fly ash in amounts up to 35 percentClass C and 30 percent of the cementitious material for CF fly ashes. Percentages greater than this can result in erescence and reduced strength with Class C fly ash and variation and reduced strength with Class F fly ash. Partlar care should be taken to insure that the fly ash meetsoundness requirement of ASTM C 618, especially whenfly ash will constitute more than 20 percent of the total mentitious material in the product.

Atmospheric-pressure steam curing is typically carriedin insulated kilns. The exact temperature used is a funcof the materials and the amount of fly ash used. Up to 35cent for Class C and 25 percent for Class F fly ashes by mof total cementitious material has been used satisfactowith a curing temperature above 71 C (160 F). Dryshrinkage of atmospheric-pressure steam-cured conunits can be reduced by the addition of fly ash. Optimum ing temperature is 82 to 93 C (180 to 200 F).

Accelerated curing techniques require a period of prbefore the concrete products are subjected to elevatedperatures. Where fly ash is used in conjunction with cemthis preset period may be longer. If so, it must be usedamage to the product may result.

Proportioning of mixtures for the manufacture of concrmasonry units is not carried out as an exact science. Cotions may vary widely from plant to plant. When proportioing mixtures, concrete product producers should checkgrading and types of aggregates, cements, equipmentkiln temperatures, and then adjust trial batches with varamounts of fly ash to achieve specific technical or econoobjectives (Valore, 1970).

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7.2—Concrete pipeThe manufacture of concrete pipe is accomplished by

different processes, one using extremely dry concrete tures and the other using more fluid concrete mixtures. Dcast concrete pipe is produced utilizing mechanical comtion, vibration or both to consolidate the dry concrete mture into a form which is removed as soon as the castinfinished. With removal of the form, the green pipe is carely transported to its place of curing. Accelerated, atmospic curing is typically used to obtain early age performanc

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Wet-cast concrete uses more fluid concrete placed compacted in a form which remains around the pipe ucertain levels of performance are achieved. Wet-cast may be manufactured by the spinning process to removecess water and air to produce high density and low perability.

Fly ash has found widespread use in the manufacturconcrete pipe as a cementitious material and as an aggrmineral filler to enhance quality and economy. Becaproperly proportioned mixtures containing fly ash make concrete less permeable, pipe containing fly ash maymore resistant to weak acids and sulfates (Davis, 1954Mather, 1982). Factors pertaining to the life of concrete pexposed to sulfate attack include the type of cement, clafly ash, quality of concrete, bedding and backfill used, asulfate concentration.

Dry-cast concrete pipe mixtures without fly ash typicause greater cement contents than necessary for strengobtain the required workability. In a packerhead pipe casoperation, concrete with a very dry consistency and low ter content is compacted into a vertical pipe form using avolving compaction tool. Vibratory pipe processes umechanical vibration to compact dry concrete into a foThe cement content can be reduced by replacing some ocement with fly ash. Fly ash is used as a cementitious mrial and as a mineral filler to provide added workability aplasticity. Equipment used in pipe production may last loer due to the lubricating effect of the fly ash. Use of fly acan increase the cohesiveness of the no-slump, freplaced concrete facilitating early form stripping and moment of the product to curing.

Other benefits attributed to the use of fly ash include aduction in the heat of hydration of concrete mixtures ctaining fly ash which can reduce the amount of hairlcracks on the inside surface of stored pipe sections (C1979). Concrete mixtures containing fly ash also tendbleed less which is very beneficial in wet-cast pipe.

Current ASTM specifications for the production of cocrete pipe require the use of fly ash meeting the provisionASTM C 618, Class F or C. These specifications allow the use of portland-pozzolan cement per ASTM C 595 ctaining a maximum of 25 percent fly ash by mass. Whereash is used separately, it is limited to between 5 and 25cent of total cementitious material. The cementitious matals content for concrete for pipe production shall not be than 280 kg/m3 (470 lb/yd3). The concrete mixture shall alshave a maximum water-cementitious materials ratio of 0

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7.3—Precast/prestressed concrete productsPrecast concrete products can be produced with or wi

reinforcement. Reinforcement typically includes the usfibers, conventional reinforcing steel, and prestressing tendons, either pretensioned or post-tensioned, or comtions thereof. By definition, precast concrete productscast and cured in other than their final position (ACI 116This enables the use of reusable forms which, for econare cycled as rapidly as possible. For this reason, thesecrete products generally achieve their competitive pos


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in the marketplace by using a limited number of forms wa rather short production cycle. Normal production schules allow for one use of forms per day, however, 10 to hr schedules are common. Accelerated curing is typicemployed to enhance early age concrete performancehandling, shipping, and product use.

Concrete mixtures for these products are proportionedhigh levels of performance at early ages. Compressstrengths of 24 to 34.5 MPa (3500 to 5000 psi) are typicrequired at the time of form removal or stripping. These ely concrete strengths are generally achieved with cemcontents of 355 to 445 kg/m3 (600 to 750 lb/yd3). Conven-tional and high-range water-reducing admixtures are oused for workability at very low water content. Non-chloriaccelerating admixtures are also sometimes used forcreased times of setting. Under these conditions, fly ash erally has not been considered as an appropriate ingrefor concrete mixtures. However, conditions appear tochanging toward the use of fly ash in these applications.

Responding to a questionnaire distributed in August 1977 members of the Prestressed Concrete Institute (PCIsponded to questions about their use of fly ash in prestreconcrete products (Shaikh and Feely, 1986). Of the totalpercent indicated that they were currently using fly ashtheir products, 9 percent had used fly ash but had stopand 58 percent had never used fly ash. Of those responthat they were using fly ash, the average fly ash contentpercentage of total cementitious material was 19 percwith the lowest being 12 percent and the highest beingpercent. Of the respondents who have discontinued theof fly ash, 86 percent stated low initial strength gain aproblem. Other problems experienced in using fly ash w1) lack of consistency of fly ash, 2) slump loss, and 3) diculty in obtaining uniform mixing. It was felt that additionastudies should be carried out to define the effect of fly ashsome of the critical parameters such as: 1) early stregain, 2) creep, 3) shrinkage, 4) permeability, and 5) elamodulus.

Favorable results were obtained by Dhir et al., (1988investigations on concrete containing fly ash at ages fromhours to 1 year measuring: 1) strength development (cpressive and tensile) and 2) deformation behavior (elacreep, and shrinkage) using Class F fly ash. The amounfly ash used as a percentage of total cementitious matranged from 22 to 45 percent, and the ratio (by massClass F fly ash added versus cement replaced ranged 1.23:1 to 1.59:1. It was concluded that concretes containfly ash perform as well as, or better than, concretes conting only rapid-hardening cement.

Another investigation was conducted with Class C fly ato determine the extent of strength gain obtainable (Naik Ramme, 1990). Cement replacements of 10 to 30 perwere investigated with fly ash replacing cement at a ratio1.25:1 using an established nominal 34.5 MPa (5000 concrete mixture without fly ash. This study concluded thigh-early strength concrete can be produced with highplacement of cement by fly ash for precast/prestressed crete operations. This work was done with the cooperatio

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two different prestressed-concrete operators. One of therations is using fly ash as 20 percent of the cementimaterial in daily work year around.

In cases where fly ash can not be economically justifiea cementitious material, it may be used to enhance product features. Fly ash used in precast concrete proimproves workability, resulting in products with sharp, dtinctive corners and edges; fly ash may also imprflowability resulting in products with better surface appeance. Better flowability and workability properties achievby using fly ash are particularly desirable for products wintricate shapes and surface patterns and for those thheavily reinforced. Additionally, an appropriate fly ash mbe used in areas with potentially reactive aggregates oknown sulfate conditions to provide protection against thtypes of long-term durability problems.

The most common reasons for using fly ash are the sain cost of materials and labor that can generally be achiand improved quality of concrete. However, proportions curing procedures used must produce adequate strength or the turnaround time on forms or molds will becreased (Ravina, 1981). In general, fly ash becomes mosirable for applications where early strength is not a criparameter. This usually occurs only when the specificatprohibit form removal before specified ages.

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7.4—No slump extruded hollow-core slabsPretensioned hollow-core structural slabs are produce

ing no-slump concrete. It is consolidated and shaped passes through an extrusion machine. The particle shathe coarse aggregate and the amount of fine aggregavery important to workability. Fly ash has been added tocrease the workability of these dry, harsh mixes (Ju1987).

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CHAPTER 8—OTHER USES OF FLY ASH

8.1—Grouts and mortarsAccording to ACI 116R, grout is “a mixture of cemen

tious material and water, with or without fine aggregate, portioned to produce a pourable consistency withsegregation of the constituents.” Its primary purpose ipermanently fill spaces or voids. Mortar contains the sbasic ingredients, but with less water so that a less fluidsistency is achieved. Mortar is used primarily in masoconstruction. The benefits derived from using fly ashgrouts and mortars are much the same as those obwhen fly ash is used in concrete (Bradbury, 1979). Thesclude economy, improved workability, lower heat of hydtion, reduced expansion due to alkali-silica reaction, redpermeability, and improved sulfate resistance. The flowaity of grout is generally improved, particularly under prsure, due primarily to the favorable particle shape and lospecific gravity of the ash particles, which tend to stay in pension longer and reduce segregation (Hempling andzella, 1976).

Common uses of grout include: (a) preplaced aggreconcrete where grout is injected into the voids of previo


), (b been con forluids orfillen

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placed coarse aggregate to produce concrete (ACI 304Rcontact grouting either under machinery to fill the spacetween a base plate and the substrate concrete or betwetop surface of concrete placed or pumped under existingcrete or rock, as in tunnel linings, (c) providing supportdeep mine applications, (d) curtain grouting where very fmixtures (often without aggregate) are used to fill crackfissures in rock foundations, (e) soil stabilization, to voids in the soil or between soil particles to densify and gerally improve its load carrying capacity, (f) slab jackingraise and realign concrete slabs or structures that havtled, and (g) underwater placing and slope protection wgrout is generally injected into preplaced inflatable clbags or blankets which are flexible enough to conform tosurrounding contour to completely fill the void and provcomplete contact.

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8.2—Controlled low-strength material (CLSM)These materials are discussed in ACI Committee Re

229 “Controlled Low Strength Materials,” and are oftknown by other names such as flowable fill, lean-mix bafill, controlled-density fills, flowable-mortar, K-krete, flyash slurry, and flowable fly ash. CLSM’s normally consisfly ash, cement, water and fine aggregate. On occasionmay include coarse aggregate, lightweight aggregate,admixtures such as air-entraining admixtures, water-reers and high-range water-reducers.

CLSM’s can be proportioned to flow like liquids; no taming or compaction is needed to achieve strength or denThey are ideal for trench backfilling, pipe bedding and ptection, foundation subbase, spread footings, paving bfloor fills, culvert backfill, and for filling abandoned tankmanholes, steam lines, and sewer lines. Large voids susink-holes, basements, and mines have been filled CLSM. Failing bridges have often been replaced by culvfor 25 percent of the cost of replacing the bridge (Lars1988). Voids under bridges, culverts, slabs, and pavemare filled with no compactive effort using CLSM to achiestability without replacement. Wash-outs of all types commonly filled with CLSM. Rip-rap has been grouted wCLSM to protect it from erosion, and revetment mats on er banks have been filled with CLSM to protect them frerosion (Larsen, 1990).

Compressive strengths ranging from 0.35 to 8.25 MPato 1200 psi) are commonly achieved in CLSM to providegidity for volume stability. Self-leveling CLSM can be prportioned to support normal loads. At strength levels than 1.0 MPa (150 psi), it can be readily excavated. If CLis used where future excavation is anticipated then an eis made to keep strengths low for easy excavation.

Economy is achieved because backfill compaction crand equipment are not necessary. Excavations for seweand other conduits can be smaller because compaequipment is not needed. Pavements, bridges, and cucan be repaired with minimal interruption of traffic and uof detours. However, the amount of subsidence of thesewet mixtures must be provided for in some applications.

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8.3—Soil cementSoil cement is “a mixture of soil and measured amoun

portland cement and water compacted to a high den(ACI 116R). Soil cement is explained in detail by a “Staof-the-Art Report on Soil-Cement” by ACI Committee 23Soil cement is used as a base for road, street and airporing. It provides uniform, strong, solid support for pavingis used for slope protection for dams and embankmentliners for reservoirs, lagoons, and other channels. It hasused as a mass placement for dikes, foundations, andcontainment berms in power plants. It has also been usrammed-earth wall systems and as regular backfill mateFly ash may be used in soil cement as a cementitious mal. Usually the cementitious material content is 4 to 16 cent of the dry weight of soil of which any portion of tcementitious material may be fly ash.

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8.4—Roller compacted concreteRoller-compacted concrete is used principally in m

concrete and pavements. ACI Committee 207 has devea report, “Roller Compacted Mass Concrete” (ACI 207.5that discusses its use in the construction and repair of dThis economical form of concrete is transported and plaby dump truck or belt at the construction site, spread by ventional earth-fill placement methods, and then compaby rollers. Final compaction is normally done by vibratroller. Construction time is very fast, the mixture is econoical and it achieves the strength of richer conventional m

ACI Committee 325 is preparing a state-of-the-art reon roller compacted concrete pavements. Roller-compaconcrete for pavement is a low-slump concrete with amm (3/4-in.) maximum aggregate size, low water conand not less than 11 percent by mass of cementitious mals, of which 70 percent may be fly ash. The materialsmixed to a low slump consistency and laid down in lifts, ually by a lay-down machine. Rubber and steel-wheel vibing rollers are used to compact the lifts. The pavement receives a water cure or curing compound. Control jointsnot normally provided. Successful uses include militaryhicle, car, truck, and aircraft parking areas as well as log ing and storage yards, forestry and mine haul roads,railroad unloading yards.

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8.5—Waste management“Wastecrete” is the name that has been given to solidif

tion and stabilization of hazardous wastes with fly ashwith various combinations of cementitious materials. Fly is typically used to solidify many types of hazardous wasuch as manufacturing waste streams, incinerator ash, fill waste, mine tailings, radioactive wastes, and superfwastes. The advantages and properties that may be assed with this use of fly ashes are:

1. reduction in permeability2. pH adjustment3. pozzolanic activity4. self-cementing5. economy


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6. free water reduction7. ease of applicationFly ash immobilizes many toxic heavy metals as relativ

insoluble hydroxides or carbonates. This immobilizationaccomplished by maintaining a pH in the range betweeand 12. Other additives are sometimes used to treat the and decrease leachability of various organic compouThe benefits of stabilization are solidification and limitithe solubility or mobility of the hazardous contaminanWhen solidifying and stabilizing hazardous waste with ash it is essential to conduct treatability studies on the cbined wastes and solidifying agents, so that appropriatsults are obtained (Roy, Eaton, and Cartledge, 1991; RoyEaton, 1992).

“Oilcrete” is a term that has been used to describe solication and stabilization of various oil wastes with fly ash other solidifying agents. The oil wastes to be treated arebased drilling fluids, water-based drilling fluids, and listedunlisted refinery sludges. Fly ash has been used for myears to stabilize oil wastes in Louisiana and Texas; recethese techniques were modified for use in the westernplains states.

In-situ treatment of oil-reserve pits is a relatively simprocedure accomplished by mixing fly ash by pneumaticjection or mechanical methods. The oil waste and fly mixture harden to form a low-permeability, solid mass. Gerally, 0.14 MPa (20 psi) will support 10 m (30 ft) of oveburden, but some agencies require 1.4 MPa (200 psi) wwill necessitate the use of additional fly ash. After stabilition, oilcrete can be covered and the natural grade resto

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CHAPTER 9—REFERENCES

9.1—Specified and/or recommended referencesThe various standards or reports referred to in this d

ment are listed below with their serial designation.

American Concrete Institute

116R Cement and Concrete Terminology201.2R Guide to Durable Concrete207.5R Roller-Compacted Mass Concrete210R Erosion of Concrete in Hydraulic Structures211.1 Standard Practice for Selecting Proportions

Normal, Heavyweight, and Mass Concrete212.3R Chemical Admixtures in Concrete212.4R Guide for Use of High-Range Water-Reduci

Admixtures in Concrete229R Controlled Low-Strength Materials (CLSM)230.1R State-of-the-Art Report on Soil Cement304 Guide for Measuring, Mixing, Transporting an

Placing concrete308 Standard Practice for Curing Concrete318 Building Code Requirements for Reinforced Co

crete363R State-of-the-Art Report on High-Strength Co

crete

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ASTM

C 14 Specification for Concrete Sewer, Storm Drain, aCulvert Pipe

C 76 Specification for Reinforced Concrete CulveStorm Drain, and Sewer Pipe

C 109 Test Method for Compressive Strength of Hydralic Cement Mortars (Using 2-in. or 50-mm CubSpecimens)

C 115 Test Method for Fineness of Portland Cement the Turbidmiter

C 151 Test Method for Autoclave Expansion of PortlanCement

C 157 Test Method for Length Change of Hardened Hdraulic Cement Mortar and Concrete

C 185 Test Method for Air Content of Hydraulic CemenMortar

C 188 Test Method for Density for Hydraulic CementC 204 Test Method for Fineness of Portland Cement

Air Permeability ApparatusC 227 Test Method for Potential Alkali Reactivity of Ce

ment-Aggregate Combinations (Mortar-Bar Metod)

C 289 Test Method for Potential Reactivity of Aggregat(Chemical Method)

C 311 Method for Sampling and Testing Fly Ash or Natral Pozzolans for Use as a Mineral Admixture Portland Cement Concrete

C 361 Standard Specification for Reinforced ConcreLow-Head Pressure Pipe

C 412 Specification for Concrete Drain TileC 430 Test Method for Fineness of Hydraulic Cement

the 45-µm (No. 325) SieveC 441 Test Method for Effectiveness of Mineral Admix

tures or Ground Blast-Furnace Slag in PreventExcessive Expansion of Concrete due to the AlkaSilica Reaction

C 478 Specification for Precast Reinforced ConcreManhole Sections

C 505 Specification for NonReinforced Concrete Irrigtion Pipe with Rubber Gasket Joints

C 506 Reinforced Concrete Arch Culvert, Storm Draiand Sewer Pipe

C 507 Specification for Reinforced Concrete EllipticaCulvert, Storm Drain, and Sewer Pipe

C 595 Specification for Blended Hydraulic CementsC 618 Specification for Fly Ash and Raw or Calcined Na

ural Pozzolan for Use as a Mineral Admixture Portland Cement Concrete

C 654 Specification for Porous Concrete PipeC 789 Specification for Precast Reinforced Concrete B

Sections for Culverts, Storm Drains, and SewersC 850 Specification for Precast Reinforced Concrete B

Sections for Culverts, Storm Drains, and Sewwith Less Than 2 ft of Cover Subjected to HighwLoadings


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C 989 Specification for Ground Iron Blast-Furnace Sfor Use in Concrete and Mortars

C 1012 Test Method for Length Change of Hydraulic-Cment Mortars Exposed to a Sulfate Solution

C 1157 Performance Specification for Blended HydrauCements

Electric Power Research Institute

SC-2616-SR, Special Report, 1982 Workshop Proceings:Research and Development Needs for Use of Fly AConcrete

CS-3314, Jan. 1984,Testing and Correlation of Fly AsProperties with Respect to Pozzolanic Behavior

Highway Research Board

HRB Special Report 127, 1972,Guide to Compounds oInterest in Cement and Concrete Research

HRB Special Report, 119, 1971,Pozzolans in HighwayConcrete, “Admixtures in Concrete,” pp. 21-32

American Coal Ash Association

How Fly Ash Improves Concrete Block, “Ready-Mix Con-crete, and Concrete Pipe,” 1978-1979, reprinted fromConcrete Industries Yearbook

Tennessee Valley Authority

Technical Report CR-81-1, 1981,Properties and Use oFly Ash in Portland Cement Concrete

United States Bureau of Reclamation

4908 Length Change of Hardened Concrete ExposeAlkali Sulfates

Canadian Standards Association

A23.5M Standard Specification for Fly Ash in Concre

These publication may be obtained from the following ganizations:

American Concrete InstituteP.O. 9094Farmington Hills, MI 48333

ASTM100 Barr Harbor DriveWest Conshohocken, PA 19428-2959

Electric Power Research InstituteBox 50490Palo Alto, CA 94303

-n

Transportation Research Board2101 Constitution AvenueWashington, DC 20418

American Coal Ash Association2760 Eisenhower Ave., Ste. 304Alexandria, VA 22314

Tennessee Valley AuthoritySingleton Materials Engineering LaboratoryKnoxville, TN 37902

Materials Engineering and Research LaboratTechnical Service CenterBureau of ReclamationP.O. Box 25007Denver, CO 80225

Canadian Standards Association178 Rexdale Blvd.Rexdale, OntarioCanada M9W 1R3

o

9.2—Cited referencesAbdun-Nur, Edward, 1961, “Fly Ash in Concrete, A

Evaluation,” Bulletin No. 284, Highway Research BoarWashington, DC, 138 pp.

Albinger, John M., 1984, “Fly Ash for Strength and Ecoomy,” Concrete International: Design and Construction. V.6, No. 4, Apr., pp. 32-34.

American Coal Ash Association, 1992, “1991 Coal Cobustion Byproduct — Production and Use,” WashingtD.C.

Belot, J. R., Jr., 1967, “Fly Ash in Concrete and ConcBlock Manufacturing,”Proceedings, 1st Fly Ash UtilizatioSymposium (Pittsburgh, Mar.),Information Circular No.8348, U.S. Bureau of Mines, Washington, D.C.

Berry, E. E., and Hemmings, R. T., 1983,Coal Ash inCanada, Report for the Canadian Electrical Association, Otario Research Foundation, V. 2, Laboratory Evaluation

Berry, E. E., and Malhotra, V. M., 1980, “Fly Ash for Uin Concrete—A Critical Review,” ACI JOURNAL, ProceedingsV. 77, No. 2, Mar.-Apr., pp. 59-73.

Best, J. F., and Lane, R. O., 1980, “Testing for OptimPumpability of Concrete,”Concrete International: Design& Construction, V. 2, No. 10, Oct., pp. 9-17.

Bhardwaj, M. C.; Batra, V. S.; and Sastry, V. V., 19“Effect of Admixtures (Calcium Chloride) on PozzalaConcrete,” Indian Concrete Journal(Bombay), V. 54, No. 5May, pp. 134-138.

Blanks, R. Fl,; Meissner, H. S.; and Rawhauser, C., 1“Cracking in Mass Concrete,” ACI JOURNAL, Proceedings V.34, No. 4, Mar.-Apr., pp. 477-496.

Blick, Ronald L.; Peterson, charles F.; and Winter, Micel E., “Proportioning and Controlling High Strength Co


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OnBe-ees

te,12-

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fy- of

,”

in

ncets,”

crete,” Proportioning Concrete Mixes, SP-46, AmericanConcrete Institute, Detroit, pp. 141-163.

Bobrowski, G. S., and Pistilli, M. F., 1979, “A LaboratorStudy of the Effects of SO, and Autoclave Expansion Copression Strength,”Proceedings, 5th International Ash Uti-lization Symposium, DOE/METC/SP-79, U.S. Departmeof Energy, Morgantown Energy Technology Center, Feb

Bradbury, H. W., 1979, “The Use and Potential for FAsh in Grouting,”Proceedings, 5th International Ash Utili-zation Symposium. DOE/METC/SP-79, U.S. DepartmentEnergy, Morgantown Energy Technology Center, Feb.

Brink, R. H., and Halstead, W. J., 1956, “Studies Relatto the Testing of Fly Ash for Use in Concrete,”Proceedings,ASTM, V. 56, pp. 1161-1206.

Brown, J. H., 1980, “Effect of Two Different PulverizedFuel Ashes Upon the Workability and Strength of ConcretTechnical Report No. 536, Cement and Concrete Assocition, Wexham Springs, 18 pp.

Buck, Ad. D., and Thornton, H. T., Jr., 1967, “Investigtions of Concrete in Eisenhower and Snell Locks Lawrence Seaway,”Technical Report No. 6-784 (NTIS AD655 504), U.S. Army Engineer Waterways Experiment Stion, Vicksburg, pp. 1-62 (plus addenda which include M6-493, 1962 and 1963).

Burns, John S.; Guarnashelli, Claudio; and McAskNeil, 1982, “Controlling the Effect of Carbon in Fly Ash oAir Entrainment,”Proceedings, 6th International Ash Utili-zation Symposium, DOE/METC/82-52, U.S. DepartmentEnergy/National Ash Association, July, V. 1, pp. 294-313

Cain, C. J., 1979, “Fly Ash in Concrete Pipe,”ConcretePipe News, V. 31, No. 6, Dec., pp. 114-116.

Cain, C. 1983, “Fly Ash—A New Resource MaterialConcrete (Chicago), V. 47, No. 7, Nov., pp. 28-32.

Cannon, Robert W., 1968, “Proportioning Fly Ash Cocrete Mixes for Strength and Economy,” ACI JOURNAL, Pro-ceedings V. 65 No. 11, Nov., pp. 969-979.

Carette, G., and Malhotra, V. M., 1983, “Early-AgStrength Development of Concrete Incorporating Fly Aand Condensed Silica Fume,”Fly Ash, Silica Fume, Slag andOther Mineral By-Products in Concrete, SP-79, Americanconcrete Institute, Detroit, pp. 765-784.

Carette, G. G., Painter, K. E.; and Malhotra, V. M., 198“Sustained High Temperature Effect on Concretes Mawith Normal Portland Cement, Normal Portland Cement aSlag, or Normal Portland Cement and Fly Ash,”ConcreteInternational: Design & Construction, V. 4, No. 7, July, pp.41-51.

Carlson, Roy W.; Houghton, Donald L.; and Polivka, Mlos, 1979, “Causes and Control of Cracking in UnreinforcMass Concrete,” ACI JOURNAL, ProceedingsV. 76, No. 7, Ju-ly, pp. 821-837.

Cochran, J.W. and Boyd, T.J., 1993, “Beneficiation of FAsh by Carbon Burnout,”Proceedings of the Tenth International Ash Use Symposium, EPRI TR 101774, V. 2, Pape73.

Cook, James E., 1981, “A Ready-Mixed Concrete Comny's Experience with Class C Fly Ash,”NRMCA Publication

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No. 163, National Ready Mixed Concrete Association, Sver Spring, Apr., pp. 1-11.

Cook, James E., 1982, “Research and Application of HStrength Concrete Using Class C Fly Ash,”Concrete Inter-national: Design & Construction, V. 4, No. 7, July pp. 72-80.

Cook, James E., 1983 “Fly Ash in Concrete—TechniConsiderations,”Concrete International: Design & Construction, V. 5, No. 9, Sept., pp. 51-59.

Davis, Raymond E., 1954, “Pozzolanic Materials—WSpecial Reference to Their Use in Concrete Pipe.”TechnicalMemorandum, American Concrete Pipe Association, Viena, pp. 14-15.

Davis, Raymond E.; Carlson, R. W.; Kelly, Joe W.; aDavis, Harmer E., 1937, “Properties of Cements and ccretes Containing Fly Ash,” ACI JOURNAL, Proceedings, V.33, No. 5, May-June, pp. 577-612.

Demirel, T., Pitt, J.M., Schlorholtz, S.M., Allenstein, R.Hammerberg, R.J., 1983, “Characterization of Fly Ash Use in Concrete,” Iowa DOT Project HR-225,Report ISU-ERI-AMES-84431.

Dhir, Ravindra K.; Apte. Arun G.; and Munday, John L., 198, “Effect of In-Source Variability of Pulverized-FueAsh Upon the Strength of OPC/pfa Concrete,”Magazine ofConcrete Research (London), V. 33, No. 117, Dec., pp. 199207.

Dhir, R.K., Munday, J.G.L., and Ho, N.Y., 1988, “PFA Structural Precast Concrete: Engineering Properties,”Ce-ment and Concrete Research, V. 18, pp. 852-862.

Diamond, Sidney, 1981a, “The Characterization of FAshes,”Proceedings, Symposium on Effects of Fly Ash Incorporation in Cement and Concrete Materials Researchciety, Pittsburgh, Nov., pp. 12-23.

Diamond, Sidney, and Lopez-Flores, Federico, 1981, “the Distinction in Physical and Chemical Characteristics tween Lignitic Bituminous Fly Ashes,” and “ComparativStudies of the Effects of Lignitic and Bituminous Fly Ashin Hydrated Cement Systems,”Proceedings, Symposium onEffects of Fly Ash Incorporated in Cement and ConcreMaterials Research Society, Pittsburgh, pp. 34-44 and 1123.

Dikeou, J. T., 1975, “Fly Ash Increases ResistanceConcrete to Sulfate Attack,”Research Report No. 23, U.S.Bureau of Reclamation, Denver, 17 pp.

Dunstan, E. R., Jr., 1976, “Performance of Lignite aSub-Bituminous Fly Ash in Concrete,”Report No. REC-ERC-76, U.S. Bureau of Reclamation, Denver, 23 pp.

Dunstan, E.R., Jr., 1980, “A Possible Method for Identiing Fly Ashes That Will Improve the Sulfate ResistanceConcretes,”Cement, Concrete, and Aggregates,V. 2, No. 1,Summer, pp. 20-30.

Dunstan, Edwin, 1984, “Fly Ash and Fly Ash ConcreteBureau of Reclamation,Report REC-ERC-82-1, 42 pp.

EPRI, 1992, “Institutional Constraints to Coal Ash UseConstruction,”Final Report TR-101686, Dec.

Ernzen, James and Carrasquillo, R. L.; 1992, “Resistaof High Strength Concrete to Cold Weather Environmen


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Research Report No. 481-7, Center for Transportation Rsearch, Austin, TX, July.

Farbiarz, J. and Carrasquillo, R. L., 1987, “Alkali-Aggrgate Reaction in Concrete Containing Fly Ash,” ACI SP-1Concrete Durability, V. 2 pp. 1787-1808.

Franklin, R. E., 1981, “Effect of Pulverized Fuel Ash the Strength of Pavement Quality Concrete,”TRRL ReportNo. 982, Transport and Road Research LaboratCrowthorne, Berkshire, 13.

Gardner, N. J., 1984, “Formwork Pressures and CemReplacement by Fly Ash,”Concrete International: Design& Construction, V. 6, No. 10, Oct., pp. 50-55.

Gaynor, R. D., 1974, “Ready Mixed Concrete,”Signifi-cance of Tests and Properties of Concrete and ConcrMaking Materials, STP-169C, ASTM, Philadelphia, pp511-521.

Gaynor, R. D., 1980, “Concrete Technology—SomReady Mixed Concrete Problems in the U.S. in 1980 Some Changes for the Future,” National Ready Mixed Ccrete Association, Silver Spring, Sept.

Gebler, Steven, and Klieger, Paul, 1983, “Effect of FAsh on the Air-Void Stability of Concrete,”Fly Ash SilicaFume, Slag and Other Mineral By-Products in Concrete, SP-79, American Concrete Institute, Detroit, pp. 103-142.

Gebler, Steven H. and Klieger, Paul; 1986 "Effect of FAsh on Physical Properties of Concrete," Proceedings, ond International Conference on the Use of Fly Ash, SiFume, and Other Mineral By-Products in Concrete, April,1, pp. 1-50.

Ghosh, R. S., 1976, "Proportioning of Concrete Mixescorporating Fly Ash,"Canadian Journal of Civil Engineering (Ottawa), V. 3, pp. 68-82.

Ghosh, Ram S., and Timusk, John, 1981, "Creep ofAsh Concrete," ACI JOURNAL, Proceedings V. 78, No. 5,Sept.-Oct., pp. 351-357.

Greening, Nathan R., 1967, "Some Causes of VariatioRequired Amount of Air-Entraining Agent in Portland Cment Mortars,"Journal, PCA Research and DevelopmeLaboratories, V. 9, No. 2, May, pp. 22-36.

Grutzeck, M. W.; Wei, Fajun; and Roy, D. M., 1984, “Rtardation Effects in the Hydration of Cement-Fly APastes,”Proceedings, Materials Research Society, Pittburgh.

Halstead, W. J., 1981, “Quality Control of Highway Cocrete Containing Fly Ash,”Report No. VHTRC 81-R38,Virginia Highway and Transportation Research CounCharlottesville, Feb.

Halstead, W.J., 1986, “Use of Fly Ash in ConcretTransportation Research Board, Research Program No.32 pages.

Haque, M. N.; Langan, B. W.; and Ward, M. A., 198“High Fly Ash Concretes,” ACI JOURNAL, Proceedings V. 81,No. 1, Jan.-Feb., pp. 54-60.

Helmuth, Richard, 1987, “Fly Ash in Cement and Cocrete,” Portland Cement Association, SP040.

Hempling, Steven D., and Pizzella, John R., 1976, “Copressive Strength of Fly Ash Cement Grouting Mix,”Pro-ceedings, 4th International Ash Utilization Symposium (S

,

t

-

-

7,

Louis, Mar.), ERDA MERC/SP-76, U.S. Bureau of MineWashington, D.C., pp. 589-598.

Hester, J. A., 1967, “Fly Ash in Roadway ConstructioProceedings, 1st Fly Ash Utilization Symposium (Pittsburgh, Mar.),Information Circular No. 8348, W.S. Bureauof Mines, Washington, D.C., pp. 87-100.

Ho, D. W. S., and Lewis, R. K., “Carbonation of ConcrIncorporating Fly Ash or a Chemical Admixture,”Fly Ash,Silica Fume, Slag and Other Mineral By-Products in Cocrete, SP-79, American concrete Institute, Detroit, pp. 3346.

Hope, Brian B., 1981, “Autoclaved Concrete ContainFly Ash,” Cement and Concrete Research, V. 11, No. 2,Mar., pp. 227-233.

Hyland, Edward J., 1970, “Practical Use of Fly AshConcrete,”Construction Specifier, V. 23, No. 2, Mar., pp39-42.

Idorn, G. M., 1983, “30 Years with Alkalis in ConcreteProceedings, 6th International Conference on Alkalis Concrete, Danish Concrete Society, Copenhagen, pp. 2

Idorn G. M., 1984, “Concrete Energy and DurabilityConcrete International: Design & Construction, V. 6, No. 2,Feb., pp. 13-20.

Idorn, G. M., and Henriksen, K. R., 1984, “State of the for Fly Ash Uses in Concrete,” Cement and Concrete Rsearch, V. 14, No. 4, July pp. 463-470.

Jawed, L., and Skainy, J., 1981, “Hydration of TricalciuSilicate in the Presence of Fly Ash,”Proceedings, Sympo-sium N, Effects of Fly Ash Incorporation in Cement aConcrete, Materials Research Society, Pittsburgh, pp. 60

Johnston, Colin; 1994, “Deicer Salt Scaling Resistaand Chloride Permeability,”Concrete International, V. 16,No. 8, pp. 48-55, Aug.

Joshi, R. D., 1979, “Sources of Pozzolanic Activity in FAshes—A Critical Review,”Proceedings, 5th InternationalAsh Utilization Symposium, DOE/METC/SP-79, U.S. Dpartment of Energy, Morgantown Energy Technology Cter, Feb., pp. 610-623.

Justman, Mark A., 1991, “Survey of Fly Ash Use Ready-Mixed Concrete,”Report P-42, to the NationaReady-Mixed Concrete Association, 8 p., May.

Juvas, Klaus, 1987, “The Workability of No-Slump Cocrete for Use in Hollow-Core Slabs,” Nordic Concrete Rsearch,Publication No. 6, pp. 121-130.

Lane, R. O., 1983, “Effects of Fly Ash on Freshly MixConcrete,”Concrete International: Design & Construction,V. 5, No. 10. Oct., pp. 50-52.

Lane, R. O., and Best, J. F., 1982, “Properties and UsFly Ash in Portland Cement Concrete,”Concrete Interna-tional: Design & Construction, V. 4, No. 7, July, pp. 81-92

Larsen, R.L., 1988, “Use of Controlled Low-Strength Mterials in Iowa,”Concrete International, July, pp. 22-23.

Larsen, R.L., 1990, “Sound Uses of CLSM’s in the Enronment,”Concrete International, July, pp. 26-29.

Larson, T.D., 1964, “Air Entrainment and Durability Apects of Fly Ash Concrete,”Proceedings, ACI V. 64, pp.866-886.


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Larsen, T. J., and Page, G. C., 1976, “Fly Ash for Strucal Concrete in Aggressive Environments,”Proceedings, 4thInternational Ash Utilization Symposium (St. Louis, MarERDA MERC/SP-76, U.S. Bureau of Mines, WashingtoD.C., pp. 573-588.

Locher, F.W., 1960, “Hydraulic Properties and Hydratiof Glasses of the System CaO-Al2O3-SiO2,” Proceedings ofthe Fourth International Symposium on the Chemistry of ment, V. 1, NBSMonograph 43, Washington, D.C., pp. 267276.

Lovewell, C. E., and Washa, Geroge W., 1958, “Proptioning Concrete Mixtures Using Fly Ash,” ACI JOURNAL,Proceedings V. 54, No. 12, June, pp. 1093-1102.

Luke, Wilbur I., 1961, “Nature and Distribution of Partcles of Various Sizes in Fly Ash,”Technical Report No. 6-583, U.S. Army Engineer Waterways Experiment StatiVicksburg, Nov., 21 pp.

Majko, Richard M., and Pistelli, Michael F., 1984, “Opmizing the Amount of Class C Fly Ash in Concrete Mitures,” Cement, Concrete and Aggregates, V. 6, No. 2,Winter, pp. 105-119.

Malhotra, V. M., 1984, “Use of Mineral Admixtures foSpecialized Concretes,”Concrete International: Design &Construction, V. 6, No. 4, Apr., pp. 19-24.

Manmohan, D., and Mehta, P. K., 1981, “Influence Pozzolanic, Slag, and Chemical Admixtures on Pore SDistribution and Permeability of Hardened Cement PastCement, Concrete, and Aggregates, V. 3, No. 1, Summer,pp. 63-67.

Manz, Oscar E., 1983, “Review of International Specifictions for Use of Fly Ash in Portland Cement Concrete,”FlyAsh, Silica Fume, Slag and Other Mineral ByproductsConcrete, SP-79, American Concrete Institute, Detroit, p198-200.

Mather, Bryant, 1958, “The Partial Replacement of Poland Cement in Concrete,”Cement and Concrete, STP-205,ASTM, Philadelphia, pp. 37-67.

Mather, Bryant, 1965, “Compressive Strength Develment of 193 Concrete Mixtures During 10 Years of MoCuring,” Miscellaneous Paper No. 6-123, Report 12 (NTISAD756 324), U.S. Army Engineer Waterways ExperimeStation, Vicksburg, Apr.

Mather, Bryant, 1974, “Use of Concrete of Low PortlanCement in Combination with Pozzolans and other Admtures in Construction of Concrete Dams,”Journal of theAmerican Concrete Institute, Proceedings, V. 71, pp. 589599.

Mather, Katherine, 1982, “Current Research in SulfResistance at the Waterways Experiment Station,”GeorgeVerbeck Symposium on Sulfate Resistance of Concrete, SP-77, American Concrete Institute, Detroit, pp. 63-74.

Mather, Katherine, and Meilenz, Richard D., 1960, “Coperative Examination of Cores from the McPherson TRoad,” Proceedings, Highway Research Board, V. 39, p205-216.

McCarthy, G. J, Johansen, D. M., Steinwand, S. J. Thedchanamoorthy, A., 1988, “X-Ray Diffraction Analysof Fly Ash,” Advances in X-Ray Analysis, V. 31.

McCarthy, Gregory J.; Swanson, Kevin D.; Keller, Lindsay P.; and Blatter, Walter C., 1984, “Mineralogy of WesteFly Ash,” Cement and Concrete Research, V. 14, No. 4, Ju-ly, pp. 471-478.

McKerall, William C.; Ledbetter, W. B.; and TeagueDavid J., 1981, “Analysis of Fly Ashes Produced in TexaCooperative Research Report No. 240-1, FHWA/TX-81/21.Texas Transportation Institution/State Department of Higways and Public Transportation, College Station, Jan.

Mehta, P. Kumar, 1983, “Pozzolanic Cementitious BProducts as Mineral Admixtures for Concrete—A CriticReview,”Fly Ash, Silica Fume, Slag and Other Mineral bProducts in Concrete, SP-79, American Concrete InstituteDetroit, pp. 1-46.

Mehta, P.K., 1986, “Effect of Fly Ash Composition oSulfate Resistance of Cement,” ACI JOURNAL, Proceedings,V. 83 No. 6, Nov.-Dec., pp. 994-1000.

Meininger, Richard C., 1981, “Use of Fly Ash in Air-Entrained Concrete—Report of Recent NSGA-NRMCA Rsearch Laboratory Studies,” National Ready Mixed ConcrAssociation, Silver Spring, Feb., 32 pp.

Mielenz, Richard C., 1983, “Mineral Admixtures—History and Background,”Concrete International: Design &Construction, V. 5, No. 8, Aug., pp. 34-42.

Mings, M. L.; Schlorholtz, S. M.; Pitt, J. M.; and Demieel, T., 1983, “Characterization of Fly Ash by X-Ray Analsis Methods,”Transportation Research Record No. 941,Transportation Research Board, pp. 5-11.

Minnick, L. J.; Webster, W. C.; and Purdy, E. J., 197“The Predictions of the Effect of Fly Ash in Portland CemeMortar and Concrete,”Journal of Materials, V. 6, No. 1,Mar., pp. 163-187.

Montgomery, D. G.; Hughes, D. C.; and Williams, R. I. T1981, “Fly Ash in Concrete—A Microstructure Study,”Ce-ment and Concrete Research, V. 11, No. 4, July, pp. 591-603.

Mukherjee, P. K.; Loughborough, M. T.; and Malhotra, M., 1982, “Development of High-Strength Concrete Incoporating a Large Percentage of Fly Ash and Superplastiers,” Cement, Concrete, and Aggregates, V. 4, No. 2,Winter, pp. 81-86.

Naik, T.R., and Ramme, B.W., 1990, “High EarStrength Fly Ash Concrete for Precast/Prestressed Pucts,”PCI Journal, Nov.-Dec. 1990, pp. 72-78.

Nasser, K. W., and Marzouk, H. M., 1979, “PropertiesMass Concrete Containing Fly Ash at High TemperatureACI JOURNAL, Proceedings V. 76, No. 4, Apr., pp. 537-550.

Pierce, James S., 1982, “Use of Fly Ash in Combating Sfate Attack in Concrete,”Proceedings, 6th International AshUtilization Symposium, Reno, V. 2, pp. 208-231.

Pistilli, Michael F., 1983, “Air-Void Parameters Deveoped by Air-Entraining Admixtures, as influenced by Solble Alkalies from Fly Ash and Portland Cement,” ACJOURNAL, Proceedings V. 80, No. 3, May-June, pp. 217-222

Pitt, J. M., and Demirel, T., 1983, “High Substitution oIowa Fly Ashes in Portland Cement Concrete,” Civil Engneering Department and Engineering Research InstitIowa State University, Ames, pp. 5-8.


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Powers, T. C., Copeland, L. E., and Mann, H. M., 19“Capillary Continuity or Discontinuity in Cement PastesJournal of the PCA Research and Development Labs, V. 1,No. 2 pp. 1-12.

Price, Walter H., 1982, “Control of Cracking in Mass Cocrete Dams,”Concrete International: Design & Construction, V. 4, No. 10, Oct., pp. 36-44.

Prusinski, Jan R., Fouad, F. H. and Donovan, M. J., 1“Plant Performance of High Strength Prestressed ConcMade with Class C Fly Ash,” Proceedings of Tenth Intertional Ash Use Symposium,EPRI Document TR-101774,Paper 41, 15 pp.

Ravina, Dan, 1981, “Efficient Utilization of Coarse aFine Fly Ash in Precast Concrete by Incorporating TherCuring,” ACI JOURNAL, Proceedings V. 78, No. 3, May-Junepp. 194-200.

Ravina, Dan, 1984, “Slump Loss of Fly Ash ConcretConcrete International: Design & Construction, V. 6, No. 4,Apr., pp. 35-39.

Regourd, M., 1983, “Technology in the 1990's Develment in Hydraulic Cements,”Proceedings A310.5, Philo-sophical Transactions, Royal Society of London, pp. 85-

Roy, A., Eaton, H. C., and Carltedge, F. K; 1991, “HeaMetal Sludge by a Portland Cement/Fly Ash Binder Mture,” Hazardous Waste & Hazardous Material, V. 9, No. 4,pp. 1.

Roy, A., Eaton, H. C.; 1992, “Solidification/Stabilizatioof Synthetic Electroplating Waste in Lime-Fly Ash BindeCement and Concrete Research, V. 22, No. 4 pp. 589.

Roy, Della M.; Luke, Karen; and Diamond, Sidney, 19“Characterization of Fly Ash and Its Reactions in ConcreProceedings, Materials Research Society, Pittsburgh.

Roy, D. M.; Skalny, J.; and Diamond, Sidney, 1982, "fects of Blending Materials on the Rheology of Cement Pand Concretes,"Proceedings, Symposium M, Concrete Rheology, Materials Research Society, Pittsburgh, pp. 152-1

Rudzinski, L., 1984, "Effect of Fly Ashes on the Rheoloical Behavior of Cement Pasts,"Materials and StructuresResearch and Testing(RILEM, Paris), V. 17, No. 101, SeptOct., pp. 369-373.

Ryan, W. G., and Munn, R. L., 1978, "Some Recent Exriences in Australia with Superplasticising Admixtures,"Su-perplasticizers in Concrete, SP-62, American ConcretInstitute, Detroit, pp. 123-136.

Samarin, A.; Munn, R. L.; and Ashby, J. B., 1983, "TUse of Fly Ash in concrete--Australian Experience,"FlyAsh, Silica fume, Slag and Other Mineral By-ProductsConcrete, SP-79, American Concrete Institute, Detroit, p143-172.

Schmidt, William, and Hoffman, Edward S., "9000 pConcrete--Why? Why Not?" Civil Engineering--ASCE, 45, No. 5, May, pp. 52-55.

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Scholer, C. H., 1963, "Proven Serviceability Fly Ash Ccrete Pavement," Walter N. Handy Co., Springfield.

Schrader, Ernest K., 1982, "The First Concrete GraDam Designed and Build for Roller Compacted Consttion Methods,"Concrete International: Design & Construction, V. 4, No. 10, Oct., pp. 15-24.

Shaikh, A. F., and Feely, J. P., 1986, "Summary of sponses to a Questionnaire on the Use of Fly Ash in thecast and Prestressed Concrete Industry,"PCI Journal, pp.126-128.

Smith, R. L.; Raba, C. F., Jr.; and Mearing, M. A., 19"Utilization of Class C Fly Ash in concrete,"Proceedings,6th International Fly Ash Utilization Symposium, RenMar., p. 31.

Snow, Peter G., 1991, “Effect of Fly Ash on Alkali-SiliReactivity in Concrete,”Transportation Research Reco1301, Factors Affecting Properties and PerformancePavements and Bridges, pp. 149-154.

Stevenson, R. J. and Huber, T. P., 1987, “SEM StudChemical Variations in Western US Fly Ash,"Materials Re-search Society Proceedings, V. 86, pp 99-108.

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Strehlow, Robert W., 1973, “Concrete Plant ProductioConcrete Plant Manufacturers Bureau, Silver Spring, pp.

Swamy, R. N.; Ali, Sami A. R.; and TheodorakopoulosD., 1983, “Early Strength Fly Ash Concrete for StructuApplications,” ACI JOURNAL, Proceedings V. 80, No. 5, Sept.Oct., pp. 414-423.

Symons, M. G., and Fleming, K. H., “Effect of Post Agusta Fly Ash on Concrete Shrinkage,"Civil EngineeringTransactions (Barton), V. CE 22, No. 3, Nov., pp. 181-18

Tikalsky, P. J. and Carrasquillo, R. L., 1993, “Fly AEvaluation and Selection for Use in Sulfate Resistant Ccrete,”ACI Materials Journal, V. 90, No. 6, pp. 545-551.

Tikalsky, P. J. and Carrasquillo, R. L., 1992, “InfluenceFly Ash on the Sulfate Resistance of Concrete,”ACI Materi-als Journal, V. 89, No. 1, pp. 69-75.

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Verbeck, George, 1960, “Chemistry of the HydrationPortland Cement,”Proceedings, 4th International Symposium on the Chemistry of Cement (Washington, D.C., OMonograph No. 43, U.S. National Bureau of StandarWashington, D.C., pp. 453-465.

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Vollick, C. A., 1959, “Effect of Water-Reducing Admixtures and Set-Retarding Admixtures on the PropertiePlastic Concrete,”Symposium on Effects of Water-ReducAdmixtures and Set-Retarding Admixtures on PropertieConcrete, STP-266, ASTM, Philadelphia, pp. 180-200.


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Wei, F.; Grutzeck, M. W.; and Roy, D. M., 1984, “Effecof Fly Ash on Hydration of Cement Pastes,”Ceramic Bulle-tin, V. 63, p. 471.

Whitlock, David R., 1993, “Electrostatic Separation Unburned Carbon from Fly Ash,Proceedings of the TentInternational Ash Use Symposium, EPRI TR 101774, V. 2Paper 70.

Yuan, Robert L., and Cook, James E., 1983, “StudClass C Fly Ash Concrete,”Fly Ash, Silica Fume, Slag anOther Mineral By-Products in Concrete, SP-79, AmericanConcrete Institute, Detroit, pp. 307-319.

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9.3—Suggested referencesFly Ash, Silica Fume, Slag, and Other Mineral By-Pro

ucts in Concrete, Proceedings of the First International Coference — Montebello, Quebec, American Concrete Intute SP-79, 1176 p., 1983, editor, V. M. Malhotra.

Fly Ash, Silica Fume, Slag, and Natural Pozzolans in Ccrete, Proceedings of the Second International Confere— Madrid, Spain, American Concrete Institute SP-91, 1p., 1986, editor, V. M. Malhotra.

Fly Ash, Silica Fume, Slag, and Natural Pozzolans in Ccrete, Proceedings of the Third International ConferenceTrondheim, Norway, American Concrete Institute SP-11706 p., 1989, editor, V. M. Malhotra.

Fly Ash, Silica Fume, Slag, and Natural Pozzolans in Ccrete, Proceedings of the US-Turkey Workshop, IstanTurkey, 184 p., 1992, editor, V. Ramakrishnan and M. heyl Akman.

Fly Ash and Coal Conversion By-Products: Characterition, Utilization and Disposal VI, Symposium ProceedingV. 178, Materials Research Society, 1989, Boston, Machusetts, editors, Robert L. Day and Fredrik P. Glasser.

Controlled Low-Strength Materials, American ConcreteInstitute SP-150, 110 p., 1994, editor, Wayne S. Adaska

Helmuth, Richard,Fly Ash in Cement and Concrete, Port-land Cement Association, 196 p., 1987.

Supplementary Cementing Materials for Concrete, CAN-MET, Ottawa, Ontario, Canadian Government PublishCentre, 1986, editor, V. M. Malhotra.

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creteucerrioderyvide

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APPENDIX—RAPID QUALITY CONTROL TESTS

A.1—Loss on ignitionThe test, in accordance with ASTM 311, involves dry

to constant mass for moisture content. However, if the mture content is known to be low, a quick loss on ignition be run in less than an hour using a preheated muffle fura crucible providing greater surface area, and a coolingthat increases heat los from the sample. In this casemoisture would be included in the ignition loss value.

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A.2—Carbon analysisCarbon content of fly ash is related to loss on ignition,

it is not a totally comparable measurement. A rapid Leco nace method is available to make a total carbon determtion. Gebler and Klieger (1983) tested a number of Clasand Class C fly ashes using this procedure. In all cases

carbon determination was somewhat less than the AST311 loss on ignition, but the correlation between the twovalues was very good.

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A.3—Material retained on 45-µm (No. 325) sieveThe ASTM C 311 procedure generally involves at le

two hours of drying of the residue on the sieve after the sieving operation. However, a hot plate or higher oven tperature can be employed to obtain more rapid resultsmethod is preferred for Class C fly ash to minimize weigain during drying due to hydration.

Wet sieving of fly ash may produce errors if the fly acontains significant water-soluble materials or materwhich react rapidly with water.

e

A.4—Air-jet sievingAlpine air-jet sieve equipment is available that will pr

vide a faster test since the sieving operation is conducteing air instead of water, and the material retained on the scan be weighed directly. Other rapid particle size distrition instruments (such as the ATM sonic sieve equipmare also available which can be employed to indicate ches in the particle size distribution of the fly ash.

-

A.5—Air-permeability finenessThe ASTM C 204 method can be used to measure the

cific surface of fly ash within 10 min. Specific surface is currently specified in ASTM C 618; however, it has bcited in previous versions of the specification. It is a fast cedure which may be used to detect changes in fly ashness from given source, particularly changes at the loweof the size distribution.

A.6—ColorColor changes can be checked by comparing the col

the fly ash with that of a reference fly ash. Spread the twashes side by side on a white surface and compare theunder daylight or controlled light source. If necessarpiece of clear glass can be placed over the fly ashes focomparison. A change in color can be an indicator of chin fly ash properties, and it may cause changes in concolor, important in architectural uses. A concrete prodcan save a jar sample from each fly ash delivery for a peof several months. A comparison of color of a new delivwith previous deliveries from the same source can proan immediate indication of changed conditions.

,ty

A.7—Density (specific gravity)Changes in density or the amount of cenospheres that

on water is another fairly rapid procedure which may be uful in identifying changes. The density procedure for fly areferenced in ASTM C 311 is C 188. The measurementbe made in an hour or two; however, excellent temperacontrol is required for good accuracy.

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A.8—Foam-index test(Meininger, 1981; Gebler and Klieger, 1983.) Foam-ind

values based on the amount of air-entraining admix


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ctedcK-ited been

needed in a slurry of 50 ml of water, 4 g of fly ash, and 1of cement to produce a layer of foam just covering the face of liquid in a 473 ml (16 oz) wide-mouthed jar after vorous shaking. There is a good relationship betweenminimum amount of admixture in this test necessary to cfoam to cover the surface, without discontinuities, andadmixture dosage needed in concrete containing the sources of fly ash and cement.

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ACI 232.2R-96 was submitted to letter ballot of the committee and was approved inaccordance with ACI balloting requirements.

A.9—Organic material(Meininger, 1981; Gebler and Klieger, 1983.) Analysis

fly ash by the Wakeley-Black soil testing method is oneproach that has been used to estimate the easily oxidiorganic matter or carbon in fly ash using sodium dichromand sulfuric acid. Those fly ashes with greater oxidizamaterial measured in this manner tended to require hadmixtures demand and caused more loss of air in conc

The University of Maryland method used in these fly studies provides a value which is increased by a factogive an estimate of total oxidizable matter. The factor ufor soils may not apply to fly ash so the direct amount ofidized material should be used. Previous work on the e

-of organic material in cement also showed that it can haeffect on air-entrainment (Greening, 1967).

e

A.10—CaO contentMeasurement of heat evolution when fly ash is rea

with an appropriate chemical solution as described by Merall, Ledbetter, and Teague (1981). In addition to the creference, some trails using automated equipment haveused. Future development of this type of equipment mayvide indicators of CaO content which can be obtained inthan 15 min.

leA.11—Presence of hydrocarbons (start-up oil)

Mix the fly ash with tap water and note the presence black film on the surface of the water.

re.

A.12—Presence of ammonia (precipitator additive)Add 20 to 50 g fly ash to tap water which includes cem

or other alkaline material. Cover the bottle and mix. Othe bottle to detect ammonia odor (Ravina 1981).

use of flyash in concrete

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