~~r~ Designation: C 618 - 00

Standard Specification for Coal Fly Ash and Raw or Calcined Natural Pozzolan for Use as a Mineral Admixture in Concrete1

This standard is issued under the fixed designation C 618; the number immediately following the designation indicates the year of original adoption or, in the case of revision, the year oflast revision. A number in parentheses indicates the year of last reapproval. A superscript epsilon (E) indIcates an editorial change since the last revision or reapproval.

This standard has been approved {or usc by agencjes of the Dcparrmem of Defense.

1. Scope 1.1 This specification covers coal fly ash and raw or

calcined natural pozzolan for use as a mineral admixture in concrete where cementitious or pozzolanic action, or both, is desired, or where other properties normally attributed to finely divided mineral admixtures may be desired, or where both objectives are to be achieved.

NOTE I-Finely divided materials may tend to reduce the entrained air content of concrete. Hence, if a mineral admixture is added to any concrete for which entrainment of air is specified, provision should be made to ensure that the specified air content is maintained by air content tests and by use of additional air-entraining admixture or use of an air-entraining admixture in combination with air-entraining hydraulic cement.

1.2 The values stated in SI units are to be regarded as the standard.

1.3 The text of this standard references notes and footnotes, which provide explanatory information. These notes and footnotes (excluding those in tables and figures) shall not be considered as requirements of the standard.

2. Referenced Documents 2.1 ASTM Standards: C 125 Standard Terminology Relating to Concrete and Concrete Aggregates2

C 311 Test Methods for Sampling and Testing Fly Ash or Natural Pozzolans for Use as a Mineral Admixture in Portland-Cement Concrete2

3. Terminology 3.1 Definitions: 3.1.1 The terms used in this specification are defined in

Terminology C 125. 3.1.2 fly asfJ--the finely divided residue that results from me-combu:sti~I1...()fground_()I ..p_o~~~r:_L~~~1 and that is

! Tbis specification is under the jurisdiction of ASTM Committee C09 on Concrete and Concrete Aggregates awl ;, the direct re5l'Msibility of Subcommittee C09.24 on Ground Slag and Pozzolonic Admixtures.

Current edition approved Aug. 10,2000. Published September 2000. Originally published as C618 68 T to replace C350 and C402. Last previous edition C618 -99.

, Annual Book ofASTM Standards, Vol 04.02.

transported by flue gasses. NOTE 2-This definition of fly ash does not include, among other

things, the residue resulting from: (1) the burning of municipal garbage or any other refuse with coal; (2) the injection of lime directly into the boiler for sulfur removal; or (3) the burning of industrial or municipal garbage in incinerators commonly known as "incinerator ash."

4. Classification 4.1 Class N-Raw or calcined natural pozzolans that com

ply with the applicable requirements for the class as given herein, such as some diatomaceous earths; opaline cherts and shales; tuffs and volcanic ashes or pumicites, calcined or uncalcined; and various materials requiring calcination to induce satisfactory properties, such as some clays and shales.

4,2ClassF~Fly ash normally produced from burning anthracite or bituminous coal that meets the applicable requirements for this class as given herein. This class fly ash has

poz~olanic properties. 4::'3 Class G---Fly ash normally produced from lignite or

subbituminous coal that meets the applicable requirements for this class as given herein. This class of fly ash, in addition to having pozzolanic properties, also has some cementitious properties.

NOTE 3-Some Class C fly ashes may contain lime contents higher than 10%.

5. Ordering Information 5.1 The purchaser shall specify any supplementary optional

chemical or physical requirements. 5.2 The purchaser shall indicate which procedure, A or B,

shall be used when specifying requirements for effectiveness in contribution to sulfate resistance under Table 4.

6. Chemical Composition 6.1 Fly ash and natural pozzolans shall conform to the

.requirementslls to chemical composition prescribed in Table 1. Supplementary -optlona:lcnemicat-requirements .. are_..shownjg Table 2.

7. Physical Properties 7.1 Fly ash and natural pozzolans shall conform to the

physical requirements prescribed in Table 3. Supplementary

Copyright ASTM. 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, United States.

~~I~ C 618

optional physical requirements are shown in Table 4.

8. Methods of Sampling and Testing 8.1 and test the mineral admixturc in accordallcc

with the requirements of Test Methods C 31 J. 8.2 Use cemcnt of the type proposed for use in the work

and, if from the mill proposed as the source of the cement, in all tests requiring the use of hydraulic cement.

9. Storage and Inspection 9.1 The mineral admixture shall be stored in such a manner

inspection and identification

Inspection of the material shall be made as agreed upon and tbe seller as part of the Durchase contract.

10. Rejection 10.1 TIle has the right to reject material that fails

to conform to the of this specification. Rejection shall be to the producer or supplier promptly and in writing.

10.2 The purchaser has the right to reject packages varying more than 5 % from tbe stated weight. The purchaser also has the right to reject the entire shipment if the average weight of the packages in any shipment, as shown by weighing 50 packages taken at random, is less than that specified.

10.3 The purchaser has the right to require that mineral admixture in storage prior to shipment for a period longer than 6 months after be retested. The purchaser has the right to reject such material if it fails to meet the fineness requirements.

11. Packaging and Package Marking

11.1 'When the mineral admixture is delivered in the class, name, and brand of the producer. and the weight of the matelial contained therein, shall be

Similar infol1TIatlOn shall be invoices the mineral admixture.

12. Keywords

12.1 mineral natural pozzolans

2

C 618 TABLE 1 Chemical Requirements

Mineral Admixture Class

N F C .._-_._._--------------------

Silicon dioxide (SiD,) plus aluminum oxide (AI2 0 3 ) plus iron oxide (Fe203)' 700 70.0 500 min, %

Sulfur trioxide (S03)' max, % 4.0 5.0 5.0 Moisture content, max, % 3.0 3.0 3.0 Loss on ignition, max, % 100 S.OA 6.0

"The use of Class F pozzolan containing up to 12.0 % loss on ignition may be approved by the user if either acceptable performance records or laboratory test results are made available.

TABLE 2 Supplementary Optional Chemical Requirement

NOT!' I--This optional requirement appJies only when specifically requested.

Mineral Admixture Class

N F C Available alkalies, as equivalent, as Na,O, max, %A 1.5 1.5 1.5

AAppiicable only when specifically required by the purchaser for mineral admixture to be used in concrete containing reactive aggregate and cement to meet a limitation on content of alkalies,

TABLE 3 Physical Requirements Mineral Admixture Class

N F C

Fineness: Amount retained when wet-sieved on 45 pm (No, 325) sieve, 34 34 34

max, %A Strength activity index: S

With portland cement, at 7 days, min, percent of 75 c 75 c 75c control

With portland cement, at 28 days, min, percent of 75 75 c 75c control

Water requirement, max, percent of control 115 105 105 Soundness: D Autodave expansion or contraction, max, % 0.8 0,8 0,8 Uniformity requirements"'

The density and fineness of individual samples shall not vary from the average established by the ten preceding tests, or by all preceding tests if the number is less than ten, by more than:

Density, max variation from average, % 5 5 5 Percent retained on 45-flm (No. 325), max variation, 5 5 5

percentage points from average

ACare should be taken to avoid the retaining of agglomerations of extremely fine material. "The strength activity index with portland cement is not to be considered a measure of the compressive strength the mineral admixture, The mass

of mineral admixture specified for the test to determine the strength activity index with portland cement is not considered to be the recommended for the concrete to be used in the work. The optimum amount of mineral admixture for any specific project is detenmined by the of the concrete and other constituents of the concrete and is to be established by testing. Strength activity index with portland cement is a measure a given cement and may vary as to the source of both the mineral admixtUre and the cement.

the 7 day or 28 day strength index will indicate specification compliance. admixture will constitute more 20 % by weight of the cementitious material in the project mix the test specimens for autoclave expansion

shall contain that anticipated percentage. Excessive autoclave expansion is highly Significant in cases where water to admixture and cement ratios are low, for example, in block or shotcrete mixes.

3

C 618

TABLE 4 Supplementary Optional Physical Requirements

NUTI', 1-Thcsc optional requirements apply only when specIfically requested. Mineral Admixture Class

F c

AApp!icable only for Class F mineral admixtures since the loss on ignition limitations predominate for Class C,

BOetermination of compliance or noncompliance with the requirement relating to increase in drying shrinkage will be made at the request of the purchaser.

cMineral admixtures meetino this requirement are considered as effective in controlling alkali reactions as the use the low-alkali control cement used in

admixture shall be considered effective only when the is used at percentan"~ mass of the total cementitious that used in the tests and when the alkali content of the cement to be used with the mineral not exceed that used in the

Appendix XI, Test Methods C 311. "Fly ash or natural shall be considered effective only when the fly ash or natural pozzolan is used at percentages, by mass, of the total cementitious material

within 2 % of those are successful in the test mixtures or between two percentages that are successful, and when the CoA content of the project cement is less than, or equal to, that which was used in the test mixtures, See Appendix X2 of Test Method C 311,

The American SOCiety for Testing and Materials takes no position respecting the validity ofany patent rights asserted in connection with any item mentioned in this standard, Users of this standard are expressly advised that determination of the validity ofany such patent rights, and the risk of infringement of such rights, are entirely their own responsibility

This standard is subject to revision at any time by the responsible technical committee and must be reviewed evel}' five years and if not revised, either reapproved or withdrawn. Your comments are invited either for revision ofthis standard or for additional standards and should be addressed to ASTM Headquarters. Your comments will receive careful consideration at a meeting of the responsible technical committee, which you may attend, If you feel that your comments have not received a fair hearing you shOUld make your views known to the ASTM Committee on Standards, at the address shown below.

This standard is copyrighted byASTM, 100 BarrHarbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States. Individual (single or multiple copies) of this standard may be obtained by contacting ASTM at the above address or at

IO-B3;?-~585 (phone), 610-832-9555 (fax), or service@astm.org (e-mail); or through the ASTM website (www,astmorg),

Multiple factor, calculated as the product of loss on ignition and fineness, amount retained when wet-sieved on 45-~m (No. 325) sieve, max, "loA

Increase of drying shrinkage of mortar bars at 28 days, max, difference, in %, 0.03 over control"

Uniformity Requirements: In addition, when air-entraining concrete is specified, the of air- 20 entraining agent required to produce an air content of 18.0 vol of mortar shall not vary from the average established the ten preceding tests or by all preceding tests if less than ten, by more than,

Effectiveness in Controlling Alkali-Silica Reaction: c Expansion of test mixture as percentage of low-alkali cement control, at 14 100

days, max, % Effectiveness in Contributing to Sulfate Resistance: D Proced u ro A:

Expansion of test mixture: For moderate SUlfate exposure after 6 months exposure, max, % 0,10 For high sulfate exposure after 6 months exposure, max, % 0.05

Procedure B: Expansion of test mixture as a percentage of sulfate resistance cement 100

control after at least 6 months exposure, max, %

255

0.03

20

0,10 0,05

100

0,03

20

0,10 0,05

100

4

FL'f A 5;+) 1> 0 c"'u t--{ m \ 3"1\>'\1, A6"", Xl 1:)1 r

aneon report fly ash in sulphate environment (1654x2340x2 tiff)

ANCON Beton Pty Ltd ACN 076102

m;:;hti,,;fh less effort, greater more complete

FlY ASH Hardened State

nr:~fftUtr~=~=::=:.. -~--~ Fly ash COrrtinues tc Cl:lI'l1bine ~'IiiIh free lime, ino\?asing s!rudural ova- lime.

PenoeabiJity. The lubricating action of

reouces w$ter content for nf"r""""

density and reduces bleed channels. This, coupled with long-term Pozzolanic reaction which ties up free lime. lowers permeability. (see chart).

Uilrability. ash concrete is denser and less

permeable which keeps aggfessive compounds outside the concrete where their destructive action is lessened. Fly ash concrete is.then more resistant to attack by sulfate, mild acid, soft (time hungry) water and sea water.

. . RellucedSnltateAtlack . As Fly ash concrete is denser and less permeable with chemically-bound free lime; it keeps sulfate from getting inside and crei3ting its destructive expansion.

Redll.eed.ffflo.re~cence. With reduced permeability and chemically-bound free lime and salts, ash concrete reduced efflorescence, causing compounds are held inside the concrete.

BeducedShrinkage. . The biggest contributor to drying shrinkage is unit water content, The lubricating action of fly ash spheres reduces water content and with it. drying shrinkage,

Reduced Heot01 HydraliOR, The Pozzolanic reaction between fly ash and lime generates less heat resulting in reduced thermal cracking,

R-f'ACTOR R=~F\O, ~ 0.75

ancon report fly ash in sulphate environment (1654x2340x2 tiff)

ANCON Beton Pty Ltd ACN U761024a3 "Leading Practical Concrete Tecimology"

PO Box: 421 Glenside SA 5065 Australia

Tel: +618837974 Fax:: +61 8 8379 7Z Mobile: +614120566'

C""""pornlenc. R.,;, p0z0030d98vld.dor

14 October 1998

,-

ANtON REPO:RT . on

PQZzQ}i;lmc Philippines. Flyaah Test-ing for its, Pe.riQ,t'lUaUce jn a S.ph~te 'En:v4'Ql1l:Uellt

and for Othe]' D1U'abUity Crite.xia-----..

REPOR.T To: Mr. T. Schroe~Mfma,gex Pozzolarric Philippines

PREPARED :6Y: Ian Burnett

UPDATED REPORT: 14 October 1998

Report Version 1 d

OtTmr Off'ias: . Sydney: Tel: +61 Z93861470 Perth! 'l:eh +61894451485 Melbourne: Tel: +61397101820 Fax: +6:1 Z93861471 Fax: +61 8 94451806 Fax: +61::; 9710 1811

Technical IB3lliJLLILIEIJTI~

Number 2FLY ASH:

THE MODERN POZZOLAN

What Are Pozzolans? Pozzolans are siliceous or siliceous/aluminous materials which, when mixed with lime and water, form cementitious compounds.

What Is Fly Ash? Fly ash is the best known - and one of the world's most commonly used - pozzolans. Physically, it is a very fine powdery material, predom'inately silica, with particles almost totally spherical in shape.

A Bilef History: Fly ash closely resembles the volcanic ashes used in the production of the earliest known hydraulic cements some 2,300 years ago-nearthesmall Italian town of Pozzuoli (which later gave its name to our modern day pozzolans). Predating portland cement by over 2,000 years, fly ash has significantly improved the performance of concrete throughout its history.

The Modern Pozzolan. Today's fly ash is a by-product of burning finely ground coal in electricity generating power plants. It is captured from the exhaust gases of the plants by electrostatic precipitators or bag houses which leave relatively clean air to escape from the smoke stacks. This accomplishes two objectives: the fine fly ash is prevented from polluting the

ambient air and the collected material once processed becomes a valuable resource for industry.

Why Is Fly Ash Used In Concrete? Fly ash is widely used today as a cementitious material in the production of a great variety of concrete mixes. The advantages of using fly ash are detailed in Pozzolanic Technical Bulletins. Briefly they include: *lncreased Compressive Strength * Increased Workability *Increased Durability 'Decreased Permeability *Reduced Sulphate Attack *Decreased Bleeding and Segregation *Reduced Shrinkage *Reduced Heat of Hydration *Reduced Cement! Aggregate Reaction *Increased Flexural Strength.

The Fly Ash Advantage: The spherical shape of fly ash particles and their extreme fineness, has a beneficial effect on the workability of concrete. The shape allows the concrete to move more freely ... and the fine particle size allows better filling of the voids. The slump test photograph shown below clearly illustrates the improved cohesion of the fly ash concrete mix.

I I

Ordinary ConcreteFly Ash Concrete

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Technical IBllllIUL[illlW

Number 3WHAT IS FLY ASH?

A&TM

The American So,ciety For Test Type F

ing ancLMaterials defines pozzo!an 1, Most effectively moderates

as .-ra- siliceous or siliceous and heat gain during concrete curing

aluminous material which in itself

- and is therefore considered an

possesses little or no cementitious ideal replacementfor some cement

value, but will, in finely divided in mass concrete, and high strength

form and in the presence of mois mixes. For the same reason, Type F

ture, chemically react with calcium is the solution to a wide range of I hydroxide at ordinary temperatures j summer concreting problems. I to form compounds possessing 2. Provides sulfide and sulfate

cementitious properties." resistance equal or superior to

Types F and C fly ash processed Type V cement. Type F is often

and distributed by Pozzolanic are recommended for use where con

by-products of the combustion of crete may be exposed to sulfate

coal in large power plants. Pozzo ions in soil and ground water.

lanic fly ash is collected in electro Type C

static precipitators or bag houses, 1. Most useful in "performance"

then claSSified by precise particle mixes, prestressed applications,

size, thus assuring a uniform, qual and other situations where higher

ity product. early strengths are important. , I

Type F fly ash is available in the 2. Especially useful in soil I largest quantities. Produced when stabilization since TypeC may not I

either anthracite, bituminous or require the addition of lime. sub-bituminous coal is burned, For additional information or Type F is generally low in lime, specific questions about fly ash. usually under seven percent, and contact your nearestPozzolanic contains a greater combination of technical representative. silica, alumina and iron (greater than 70 percent) than Type C fly ash.

Type C fly ash normally comes from lignite or sub-bituminous coal. These types of coal may -prod-uceanashwlthhigher lime contents - generally more than 15 percent - often as high as 30 percent This gives Type C unique self-hardening characteristics.

Where as both types of fly ash impart a wide range of qualities to many types of concrete, they differ chiefly in the following ways:

1\' l\eVA QOITICU f"r.H lUCIA. f"'1'l.11C"f""IOhlill nnl n~Ann. InAt-tn. Un1JTA~A

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I I ASTM SPECIFICATIONs FOR FLY ASH Number 4 I

I Like all materials used in the production of I

concrete, fly ash must meet the stringent require- , i ments of ASTMsp.ec.. i.f. katio.nS..f.. JY...ash sp...e.cific...a-l tions are addressed under ASTMC-6 J8 "Fly Ash and Raw orCalcinedNalural Pozzolan for \1 Use as a Mineral Admixture in Portland Cement. Concrete.." While these standards are continu- i ously under review and subject to change, a reP-i resentation of this specification, current at the I time of this writing follows this article.

The specifications are categorized by chemical and physical pr9perties for standard and optional requirements. Standard requirements are imposed for alllly ash produced while optional requirements are applied only when certain conditions exist. Standard Chemical Requirements:

Major Oxides. .summation of the major oxides of Si0 , A 13, and Fe 0 indicates the 2 2 2 3 amount of reactive material present and functions asthem~jordHference between class F and class C llyash. Allhough not expressly addressed, CaO fills in [or the reduced levels of major oxides in class C ny ash.

Sulfur Trioxide. S03 content limitation is based on minimizing expansion during hydration.

M()l.st~r~.... c?ll~e~t... M.?isture co~te~t .. is B!jm(\rilY)(frlt~q'(jI.l~I()~~ncernsover.Bo~a~iljty,Values as lowaSonepercent may cayseH9.,w problems. 5\$~TCtl.AY

Loss On Ignition. Loss On It1~lion (LOl)i is a measure of unburned carbon remaining inl the By ash. It is desirable to maintain the lowest level of LOI possible, especially for air entrained I concrete as carbon absorbs air-entraining agent! rendering it unavailable for generation of an airl void system. A low LOI is also desirable to pre-

v....e....n....'.diSCOIO... rat.ion. O.....f. t.he... co.fl.... c~~.LO.I fOf.. classFUy ashpreviou~ lirnitedloJypercent has .

been lowered t~ercent. This was done to improve Ily ash quality. 'I Standard Physical Requirements: .

Fineness. The specilication places an up-I per limit on coarseness of lIy ash at 34 percentretained on the #325 sieve. Maintaining uniform, l rin ('! ness of tbe fly ash isirr1pgrtantj n producingl quality concrete of consistent caliber. i

Strength Activity Index. Strength activi

:~ :~t~ f:7~td~:/~~~h.~~~t~Rr;.:i~~~i:~

weIght (JLce!'f1enUs r!'!placedwlthhke weight pJIrlyasn.:jlhe test departs from the oid pozzolanl test which was a 35% equivalent volume replac~J ment o[ cement with fly ash. The current testlSj felt to better simUlate the usefulness of [ly as~ lor strength in concrete. r

Lime Pozzolanlc Activity Index. Poz zolanic activity with lime is again a measure 0,

I

the pozzolanic activity 01 the fly ash being tested using a mortar mix composed of lime, fly ash and sand.

Water Requirement. Water requirement is an important tesLindicating the capacity of fly ash to reduce water demand. Most active fly ashes of good quality generate water demands of Jess than 95 percent 01 the total cement control.

Autoclave Expansion. Autoclave expansion forces tota: cementitious hydration under

temperatures and pressures and gives an accurate determination 01 long term expansion characteristics cl fly ash concrete.

Uniformi~y. Uniformity requirements for the specilic gravity and fineness of the lIy ash ensure a level 0:' consistency of the fly ash enabling unHorm production of concrete. Optional Chemical Requirements:

Available Alkalies. Available alkalies are measured as the amount available in a saturated lime solution. Thi.s requirement is recommended only where the threat 01 alkali-aggregate reactions my be encountered. OpUooal Physlical Requirements:

Multlple Factor. Multiple factor is the product of fineness and La!. The intent is to prevent both fineness and La! lrom reaching specification limits simultaneously and is a method 01 maintaining uniformity.

Drying Shrinkage. The drying shrinkage test measures th'~ increase in shrinkage of the fly ash in a morta,r sample. Most high quality fly ash will actually l;ed.uce the d(Yingshfinkage in concrete. .

Air Entrain.ing Admixture Demand. Air entraining admixture demand reflects the effect of fly ash on air entraining admixture and encompasses changes in fineness and La!. A high LOI affects the ability to entrain air. Fly ashes with LOI under one percent generally do not affect admixture demand significantly.

Reactivity with Cement Alkalies. Cement alkali reactlon indicates the elfectiveness of fly ash in reducing alkali-aggregate reaction. Due to the test method and the materials comprising the test, it is only an indicator and cannot .beidentifiedwith perlormance_olconcrele.This test should only be used when alkaliaggregate conditions are suspected.

ASTM specifications fully cover requirements lor /Iy ash in Portland cement concrete and provide [or the use 01 the uniform. well tested materials for lly ash concrete production.

for further in/ormation Or specific questions regarding ASTM specifications for fly ash. con tact your neares!: Pozzolanic technical representative.

(specificaliOf/ chart 0(/ back)

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l ;""~'r:~?1~~:?i.. :.;~ :~~~':;"-::

Technical [B3ill1IllLlE'TI1l~

Number 5WHY USE FLY ASH?

Concrete manufacturers. engineers, architects, developers and contractors all have an interest in specifying or using ash on a routine basis to improve quality of their project and toincrea'se their cost effectiveness.

Ready Mix Producers. A ready mix prod ucer has several reasons for using ash in concrete.

1. Fly ash can compensate for fines not found in some sands Clnd, thereby, enhance pumpability and concrete finishing.

2. Fly ash will result in a more predictable and consistent finished product which will ensure customer acceptance.

3. Fly ash offers flexibility in mix design providing a greater range of mixes

from liquid soil at 100 p.s.i. to high strength 8,OOO-plus p.s.i. concrete - pro. duced by the same batch plant without exotic equipment.

4. Fly ash improves the flowability of the concrete which translates into less wear and tear on alilhe producer's equipment from batching facilities to trucks.

5. Fly ash enables the producer to customize designs to each customer's needs. thus providing the producer who uses it with a competitive advantage.

Engineers and Architects. Engineers and architects will find that fly ash provides the following benefits:

1. It enables them to provide the client with a superior and more durable finished concrete.

2. Fly ash produces a high strength concrete that accommodates the design of thinner sections.

3. Fly ash permits design flexibility acc()mmudating curves. arches and other 'pleasiilgarcliilecTufal eHects

4. The addition of fly ash to the mix is a bu ilt in insurance lor later age strength gain in concrete.

S. Fly ash ensures that the concrete will qualify as a durable building material.

6. Fly ash contributes to the aesthetic appearance of the concrete

Developers, Contractors, Owners. ash concrete provides the following

advantages to developers, contractors and owners:

J. The workability of fly ash concrete generally ensures that the speed of construction is laster which translates into a quicker return on investment.

2. Fly ash in the mix accommodates more creative designs.

3. Since rJy ash concrete is not as vulnerable to deterioration or disintegration as rapidly as concrete without fly ash, it ensures low-maintenance buildings which will retain Iheirvalue over the longterm.

Fly ash definitely enhances concrete construction and returns real benefits to every member of the building team.

For further information or specific questions about the use of Jly ash, contact your nearest Pozzolanic technical representative.

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''-IT\U\\ /1 .;J 1:. ~ fbE"TOI'Ie 7vol : R.EA-l>Y Mix.(f

oieal m\lllILILllilJ1JlNJ

Number 6WHAT IS TYPE IP CEMENf?

Portland-pozzolan cements (Type I P) are precise blends of portland cement and fly ash (pozzolan). These cements are manufactured to enhance concrete products by introducing the properties imparted by fly ash: increased compressive strength, increased workability, increased durability, decreased permeability, reduced sulphate attack, decreased bleeding and segregation, reduced shrinkage, reduced heat of hydration, reduced cemenVaggregate reactions, increased flexural strength.

Specifications. Specifications lor these cements are in ASTM C-595-81 and cover the following cements: 1

L Types J(PM) & I (PM)-A pozzalan modified portland cement for use in general concrete construction. Percentages of fly ash included are up to 15 percent.

2. Types I P & 1 P-A portland-pozzalan cement for use in general construction. Percentages of fly ash range from 151040 percent.

3. Type P portland-pozzolan cement for use in concrete construction where high strengths at early ages are not required. Percentage of fly ash is generally ati,TypelP cements are produced by two methods, either by direct blending of a specification fly ash or by intergrinding

ash with cement clinker in a finish Intergrinding allows the use of coarse. non-specification fly ash to be used since grinding in the finish mill will reduce its fineness.

Fly Ash Superior. Pozzolans normally used include fly ash, diatomaceous earth, shale, volcanic ashes or pumicites as well as somecalcined claysand shales.

gIves tfie-best results lor production of Type I P cement.

I. Fly ash consists of spheres which enhance workability with a lubricating action not given by high-surface area,

angular, natural pozzolan particles which tend to yield sticky concrete mixes.

2. Fly ash spheres reduce water demand; thus improving concrete quality white natural pozzolans increase water demand. Upon intergri!)ding, the larger ash spheres are crushed, releasing many smaller spheres which were trapped inside. Releasing these spheres can significantly increase the aCtivity of a fly ash.

Caution should be used, however, with fly ashes of high carbon contents. Upon intergrinding, the carbon particles will be ground very fine exposing a high surface area which can result in problems in entraining air in concrete. Highcarbtm ffy ash should not be used in this uppltcati6n5

Although the use of Type I P cement affords the user the advantages of fly ash concrete, blended cements limit the flexibility of the concrete producer to vary percentages of fly ash to meet different needs. The best way to maintain flexibility is to inventory fly ash in a silo of its own and design the mixes as needed.

For further information or specific questions about 1 P cements, contact your nearest Pozzolanic technical representative.

IASTM C-595-81: "Standard Specification For Blended Hydraulic CemenC. ASTM.Annua/ Book OfStandards. Part 14. Concrete And Mineral Aggregates: 1981

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(1 1"

Technical [E)(U][LllIEmW

Number 7CHEMICAL COMPARISON OF FLY ASH

AND PORTlAND CEMENT The chemical composition of fly ash is

very similar to that of portland cement The table below shows typical com.

pound#analyses for two fly ashes and a natural pozzolan (Class F Fly Ash, Class CFly Ash and Class N Natural) and ordinary portland cemenl A glance at the table reveals:

I. The same compounds exist In fly ash and portland cemenl Those of flv ash are

amorphous (glassy) due to rapid cooti ng; those of cement are crystalline formed slower cooling.

2. The major difference between fly ash and portland cement is the relative quantity of each of the different compounds. Portland cement is rich in lime (CaO) while fly'ash is low. Fly ash is high in reactive silicates while

cement has smaller amounts.

TI'PICAL CHEMICAL COMPOUNDS

IN POZZOIANS AND PORTlAND CEMENT

POZZOlAN TYPE CHEMICAL COMPOUND ClASS F CLASSC ClASS N CEMENT SiO 54.90 39.90 58.20 22.60

25.BOAI20 3 16.70 IB.40 4.30 6.90Fe~Ol 5.BO 9.30 2.40

CaO B.70 24.30 3.30 64.40 MgO LBO 4.60 3.90 2.10

0.60SOl 3.30 . LI0 2.30 Na,O & K20 0.60 L30 1.10 0.60

The table illustrates the basic chemical durable cementing compounds no different difference. Portland cement Is manufactured from those formed during hydration,of ordinary with CaO some of which is released in a free cement. state during hydration. As much as 20 A review of the chemistry of both materials of free lime is released during the hydration of makes it quite apparent that a blend of the two JOO pounds of cement. This liberated lime will enhance the concrete product and effi forms the necessary Ingredient for reaction ciently utilize the properties of both, with fly ash silicates to form strong and

HYDRATION PRODUCTS OF CEMENTING BINDERS PORTLAND CEMENT

PORTLAND, CALCIUM CEMENT

(PC) + WATER -)

(H,Ol ,----__---"""""~~L__----"~ SILICATE

HYDRATE (CSH 1

PORTLAND CEMENT T FREE LIME (CAOH)

WATER

~~T~Ft:Y --ASH - -PORTLAND FLY

CEMENT + ASH + WATER +( PC) ( FA) ( H, 01 ~ ""-~ "'00'7_ _ CALCIUM SILICATE HYDRATE $Ot.;,UABLE,

(CSH)

FREE FLY LIME + ASH

( CA OH) ( FA) THROUGH POZZOLANIC ACTIVITY. FLY ASH COtotilNES WlTH FREE LIME TO PRODUCE THE SAME CEMENTITIOUS COMPOUNDS FORMED BY THE HYDRATION OF PORTLAND CEMErIT.

For further information or specific questions about the chemistry or fly ash, contact your nearest Pozzolanic techniCal representative.

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FLY ASH AND THE

. CONCRETE PRODUCER During ,the past 20 years, the

producer of ready-mixed concrete has experienced a number of challenges in incorporating new tech

nology into day-to-day operations. The addition of air entraining

chemical admixtures to concrete

mixtures previously containing

only cement, water and aggregates

required increased production

equipment and controls to provide

satisfactory performance and

uniformity.

Chemical water reducing ad

mixtures further complicated con

crete production by opening a new'

range of product offerings with

varied properties depending upon

need and choice.

Conversion of concrete pro

duction from a sack content stand

ard to a compressive strength per

formance standard increased the

need for consistency in produc

tion and more testing to ensure

quality.

Meeting these technological

challenges and others have re

quired expertise and operational

changes which have resulted in

the production of better quality

concrete and a wider range of

concrete products.

Ely.asb.. presents a technical challenge similar to the others and also offers many benefits and opportunities. Benefits to concrete include: Increased ultimate compressive

strength Reduced water demand

Number 9

Improved workability Better pumpability Easier finishing Reduced segregation Increased density Reduced permeability Reduced bleeding Reduced heat of hydration Reduced drying shrinkage Reduced thermal volume change Increased early age extensibility Decreased creep' Increased flexural and tensile

strength Increased ultimate modulus of

elasticity Decreased leaching and

efflorescence Decreased alkali-aggregate

reaction Increased ultimate freeze-thaw

resistance Increased sulfate resistance

For information about the proper handling and storage methods for fly ash, see Technical Bulletin Number 10.

For information about proportioning fly ash concrete mixes, see Technical Bulletin Number 11.

For information about supply of fly ash, see Technical Bulletin Number 1.

For information about ASTM specifications for fly ash.~ee Technical Bulletin Number 4.

For further information Or assistance, please contact your nearest Pozzolanic technical representative .

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() O .... ~ .......I_ ... ;"'" l .... t .... ~ ....... 'll'>ro. ...1 f"'''' ...... " ......... 1eo:-....=

10 HANDLING FLY ASH ash and cement are transported

and handled with common ment but a similarity in appear-

has some different that can affect its

FlowabUity. reveal that fly ash particles This rounded shape prevents the from interlocking and restraining the flow. "When aera.tedjflyashiscapapleof flo'ving{ilrough openings where will not flow.

More Abrasive. Fly ash consists, basically. of particles of glassy silica dioxide that have the abrasive qualities of sandblasting grit. Fly ash flowing through a small leak can rapidly enlarge it to increase the rate of [low.

These two properties can cause problems if there are leaks - even very tiny ones- in either the storage orthe handling equipment.

Therefore, if it's necessary to store fly ash adjacent to cement in a split silo, the partitioning must be carefully checked for leaks to prevent seepage. Double partition walls are recommended providing an extra measure of safety.

Separate dust collection systems must be used on split silos to avoid contamination in compartments.

REMEMBER - FLY ASH WILL FLOW WHERE CEMENT WILL NOT.

Highly Absorbent. Fly ash can be handled equally well with either screw systems or air-slide equipment, However, some fly ash is in a sense "hydroscopic" and it may readily absorb moisture.

Special precautions must be taken to ensure that any equipment used to handle

ash has adequate water _ Watershouldnol be'

allowed to collect on top of silos or above C>nllipment that handles fly ash.

Alcohol traps have proven very effective for removing moisture from the aeration source. Where boit-together equipment is

llli3illJILILlliUDW

Special Considerations. The fine

ness of the flv ash also reauirps that

screws or air-slides should contain positive cut-off valves_ Certain air-slide designs may be excepted from this, although positive cut-offs are generally a good idea for all fly ash systems: As a general ru Ie, screws should be used for upslopes (max. 26 degrees) and air-slides should have a down slope of 5 to 8 degrees.

Since dry fly ash is' generally less dense than cement, tonnage capacity of a silo will be less than for cement.

Unless fluidizing techniques are employed, there is a danger of pa

PROPORTIONING FLY ASH CONCRETE MIXES Effects of Fly Ash~n ProportIonIng

. Proportioning fly ash concrete mixtures is only slightly more complicated than proportioning plain cement concrete mixtures. The same solid voh-!;lTIep~oportioning techniques described in A'ef211 are employed as are used with conventional concrete mixtures.

AC! 211 gives theproportioner a series of steps through which values are selected for:

cementitious materials content water content air content coarse aggregate size and content These ingredients are converted into

solid volumes. The difference between the sum of the total volumes and 2.7 cubic feet will determine the ilecessruy volume of sand. Sand weight is then calculated to complete the trial mix proportions. The accuracy of this mix must be checked by physically preparing a sample of the proportioned ingredients and testing the mixture for yield.

While fly ash is a cementitious material which greatly benefits concrete, the proportioning of concrete containing fly ash requires adjustments due to the physical properties of the ash. Viewed microscopically, fly ash particles are found to be spherical in shape. Because of this and other physical attributes of fly ash, one can expect the following:

The ball bearing shape significantly aids the workability of concrete. This allows for lower sand content than conventional mixes while handling remains similar. As the propqrtion of sand is reduced, all pertor

anceaspects of llie concrete are enhanced. \'~I~~~;;~

plain concrete, and this redud'lon can be further increased where high levels of fly ash are used.

The specific gravity of fly ash is much lower than that of Portland cement; there-

TFI FPHnNF: I nr.AI

i

TechnicalIB3lliJIlJLlliUDINJ

Number 11

While ffy ash is generally

fore, 100# of fly ash has a much greater solid volume than the same weight of Portland cement. Past practice has dictated a cement reduction when water-reducing admixtures are used; however. in fly ash concrete the cementitious~~terials (cefuentand flYa:sh) /volume is hil5h~ri not lower. ThiS higher quantity of cementitious materials greatly assists in the finishing process.

Air-entrainment is not affected adversely with high quality, low LOI fly ash supplied by Pozzolanic, but one can expect a need for a sligj:ltly higher dosage of airentraining due to the increased solid volume of cementitiousfines. T~i~ingeClSejBdo~ "~:/l)pjG

.'-.i;''''

Technical J]3ill1ILllIETI1lW

Number 12FLY ASH FOR

STRUCTURAL CONCRETE A major use for fly ash in the construc

tion industry is in the production of high quality structural concrete. Fly ash contributes beneficial properties to the concrete while helping to maintain economy. These properties include compressive strength, lubrication and increased durability.

CompressIve Strength. Specifications for normal strength concrete generally require a given level of strength in 28 days. Fly ash concrete is easily proportioned to meet strength requirements at this age or any other age desired.

Fly ash concrete designed to be equivalent in strngth to ordinary concrete at 28 days will normally exhibit slightly lower strength at early ages. This slight early age strength reduction does not adversely affect job sequencing due to construction loading. (See strength gain curves in Fig. 1).]

Fly ash concrete can be easily proportioned to meet strength specifications at early ages (3 to 7 days). Economics, although still attractive, will not be as great as when proportioning for 2~ays ofage orlater. Fly ash has been.titilizedinrnany 'earlystr~f)~th projec!s.b8ause ofmanyheriefieiarleatllres other than economy.

Later age strength gain after 28 days can prove to be quite valuable. It may be used to obtain required strengths at lower cost. It may be relied upon in deciding structural acceptability where compressive strength tests indicate lower than specified strengths. It also plays a key role in producing high strength concrete.

High compressive strengths from 6,000 p.s.Lto... H,.oQOp,sJ, are.gflenrequ.ire

'1 :;,

Techni I lli3illJIULffiUIJW FLY ASH IMPROVES WORKABILITY Number 13

Though it is neverspecifiecj, workability is one 01 the most critical characteristics of concrete. WorkabilitY refers to the ~ase of handling, placing and finishing of fresh or ~plastic" concrete. Slump is the general indicator of workability, yet different concretes can have greatly different levels

with the same slump measurement. Blemishes in concrete, typically called

rock pockets, are indicative of concrete without suitable workability I even though the slump may be judged to be acceptable. Rock pockets indicate a separation of the paste from the coarse aggregate in the concrete mix. Concrete must be cohesive even at high slumps to maintain its homogeneous character and avoid segregation and costly rock pockets. Fly ash offers this feature without extra cost.

Reduced Water of Convenience. Approximat~ly 25 pounds (three gallons) of water are normally required to hydrate 100 pounds of cement l A normal concrete mix will generally contain twice the required amount of water to hydrate the cement enough to facilitate handling and plaCing of the concrete. This additional water, called ~"'watefofcbrivenlence," increases slump but aHhe cost of decreased cohesiveness. Water of convenience is reduced when fly ash is added to the mix because the plasticizing action results in a two to ten percent water reduction in the plastic concrete to produce the same level of slump as plain concrete. Reduced water of convenience at the same level of slump makes for more cohesive concrete and decreases the occurrence of costly segregation.

Greater Consolidation. Fly ash concrefeISadllaIlY-irioreworkablelhali p1

"

o

TYPICAL

VEBE TIME

VS. SLUMP

~ P1.AIH "" "

'i~"'f ' vI~"

in.

Paste Volume Increases. The specific gravity of fly ash is lighter than cement. When replacing cement with fly ash on a pound for pound basis, the result is a greater solid volume of cementitious fines. Proportioning concrete mixtures with only waterreducing admixtures results in a greatly diminished volume of cementitious fines. In effect~~misaffioUfits 16 lakihgcemefifahd water out of the mix and replacing them with sand and gravel. The strengths may be acceptable, but the workability may not be. Proportioning penormance concrete with ash virtually guarantees a greater solid volume of cementitious materials which in itself helps promote cohesiveness and workability.

Cementitious fines are very important to

(continued on back)

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, ";,J

"~: ;~

Technical IDOJILILlliUlJW

- 1

FLY ASH DECREASES THE Number 15 PERMEABILITY OF CONCRETE

Permeability of concrete and the resulting level of durability are matters of the greatest concern as the infrastructure of our nation disintegrates before our very eyes. Our task now is to replace that which has fallen apart and to do so in such a manner that it will last. Attention to permeability and durability then become our primary goals.

Permeability is defined as the coefficient representing Uthe rate at which water is transmitted through a saturated specimen of concrete under an externally maintained hydraulic gradientl," Permeability is inversely linked to durability in that the lower the permeability, the higher the durability of concrete.

Permeability is most frequently being described now by the chloride-ion permeability tes~ which measures the passage of electrical current through a concrete specimen exposed to a batch 01 sodium chloride2, Limits 01 acceptability are as shown in the table belo~.

Table 1. Chloride Permeablllty

Based on Charge Passed

Charge Pused Chloride (coulombs) Permeability Typical 01

,. 4,000 High High walercemenl ratio (>0.6), pee

2,000 4.000 Moderate Moderale walercement ralio (OA 10 0.5), pee

1,000 2,000 Low Low water-cemenl ratio 004), PCC

100 1,000 Very Low Latex-modified concrele, silca-lume collcrete

< 100 Negligible Polymer impregnated concrele, polymer

It has been common thought that

latex modified and silica-fume concretes had

the ability to obtain permeabilities Jow

enough to pose long term durability lor our

highway system. Recent testing, however,

has shown that properly proportioned con

cretes using a combination 01 fly ash, nor

mal or high-range water reducing admixtures,

and air entraining admixtures have the abilto produce the same low levels of perme

-_~_'V'_-r---,_,,,,_________ ~Fly~crease the cementitiouS\ ;co~pounds, minimize water d~mand, and ~"

( reduce bleed channels all of which increase i >concrete density. These factors yield con- \~

Techni I IB3illJILILIETI1J1NJ CL~SS F FLY ASH DECREASES Number]6 POTENTIAL ALKALI/AGGREGATE REACTION

Theiunique properties of class F it ot only beneficial, but

essentia in some cases for decreasing reaction b tween cement and aggregates during the ncreting process l (see Fig. 1).

Un er certain conditions and in certain areas, re ctive silica in aggregates will react with sol ble alkalies from any available source, ausing excessive and deleterious expansi n. A volume change will occur over a period of time which causes the concrete to "soaIl' at the surface. In addition to re

s rface ruptures, interior may occur w ich cause cracking and seriously impair s ructural integrity of the concrete.

The! use of low alkali (L.A.) cement 0.6% Ikalies) has become standard for combatt ng reactive aggregates, although it may by itself prove ineffective over time. ASTM C 27 limits expansion at six months to O.OID . While a mixture may prove acceptabl in the test, it may well

expansion. Class C fly ash may not control expansion as well as class F. notes that CaO content may be a useful parameter to indicate the effectiveness of an ash to combat alkali/aggregate reaction3 (see Fig. 3),

The decrease in alkali/aggregate reaction comes from the fact that class F fly ash reacts chemically with and absorbs alkalies in the cement, thus making them unavailable for reaction later with the reactive ag_ gregate.

One example of class F fly ash's unique propensity to reduce alkali/aggregate reactions was documented by the State of Alabama. In 1960, the Alabama Highway Department specified fly ash in all concrete pavement, bridges and culverts. Time-tested results in hundreds 01 lane-miles of fly ash concrete since then have been tive according to department representatives. Bridges more than 20 years old have exhib:

destruct' e expansion later 2). Alkalies fr m other sources, including the aggregate, can fuel the expansion reaction. Some . gregates may also be so reactive that they expand to failure before six months with low lkali cement. Stark reported failure of a mix ure containing cement with as little as .35% otal alkalies2

Incl ding Class F fly ash in the mix design inv riably reduces this reaction, protecting he concrete (and the steel reinforcem t) from the deterioration which

ited improved resistance to alkali/aggregate reaction.

In addition to the use of pozzolanic material, it is recommended that low-alkali cement (less than 0.6%) and acceptable aggregates be used in order to prevent alkalijaggregate reaction4

For further information or specific questions about the use of fly ash to decrease alkali/aggregate reactions, contact your nearest Pozzoianic technical represen tative.

IEliert, R.I J., "Bureau 01 Reclamation with Fly Ash and Other Puzwlans in Concrete," Thirc al Ash Utilization Symposium, 1973, p. 14.

2Stark, D.te.. "AlkaliSilica Reactivity: Some Reconsiderations," Research Development Bulletin RD07D.OlT

Portland ement Association, 1981.

'Dunstan, E. R., "Fly Ash and Fly Ash Concrete," Bureau of Reclumution, Denver, Colorudo, hlu)' 1984.

~Graham, D. E., "Fly Ash and Its use in Concrete," NRMCA Publication No. 138, 1972, p. 10.

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CLASS F FLY ASH INCREASES Number 17 RESISTANCE TO SULFATE ATTACK

Soluble sulfates in soils, ground waters, and sewage waste destroy Portland cement concrete unless it is designed with fly ash to maximize sulfate resistance.

Sulfate attack is a two-phased pr.ocess: I) Sulfates combine with calcium hydroxide, forming calcium sulfate (gypsum). The volume of this gypsum is greater than the sum of its components, causingintemal pressures which fracture the concrete. 2,) Aluminate compounds from Portland' cement are attacked by sulfates forming a compound called ettringite. Ettringite formation ruptures the concrete in the same manner as gypsum formation.

Fly ash effectively reduces this sulfate deterioration in three important ways: I) Class F fly a

- ......,,~... ......... ~J~LSL!::tJJ;; Ll IJ L1'\J

FLY ASH HELPS MINIMIZE Number 18 CONCRETE VOLUME CHANGE

It is natural that concrete changes volume with changing environmental conditions. Three primary factors are responsible for volume changes in concrete: temperature, moisture, and applied stress. Volume change becomes a critical element when conqete is placed in a restrained area ultimately resulting in high stresses and failure. Fly ash can be instrumental in assisting to minimize the changes in volume and the res\llting cracking associated with it.

same causing the edges to curl upwards. ApplIed Stress. Applied stress (loading)

causes a change in concrete shape and dimension called "delormation." Delormation can occur rapidly caUSing a quick failure, Or it can begin immediately and continue for as long as the load is maintained on the concrete. Time dependent deformation is called creep." (See Technical Bulletin #37)

Fly Ash MinImIzes Change. Pozzolanic's Temperature. Concrete volume changes

in a manner directly proportional to changes in temperature Irom the time it first looses plasticity t6when it gains its permanent set. High heat of hydration in its early life causes great expansion followed by great contraction as it cools back to ambient conditions. Thermal cracking becomes an issue as heat is retained inside the mass of concrete more than at the edges_ This means the outside shrinks faster than the inside with differential shrinkage accounting for ther~al cracking. Concrete should be plated and I

- - - -- - '---" ""---"-' '------IL...--tL.=.1 Ll LJ L1 U

FLY ASH IMPROVES FLEXURAL STRENGTH

Flexural strength of concrete is of importance in highway and street pavements, warehouses, parking facilities - any area where concrete must support vehicles. While the flexural capacity of concrete may be low in comparison with other materials, such as steel, it can be proportioned and its application engineered to provide durable, 10nglasting service. Concrete Capacity. The capacity

of a rigid concrete to support a given dynamic. repetitious loading is basically a function of concrete section thickness, flexural strength and subgrade stability. Many current specifi

_ cations caU for the flexural performance of conventional concrete without realizing the benefits fly ash can effect to achieve more durable, longer lasting pavements at lower cost. Fly Ash Advantages. The advan

tages offered by fly ash are both physical and chemical in nature and positively affect lIexural strengths. Physical Advantages. Fly ash

consists of microscopic spheres which interact in the concrete mix to give the following benefits cement

. and other additives cannot. 1. Fly ash spheres impart a ball

bearing action that greatly increases workability. This increased workability can be utilized to reduce sand content which reduces aggregate surface area to be coated and increases flexural strength.

Increased. densitylsachieved as fly ash concrete is more easilyconsolidated and voids filled with the small spherical particles.

Number 19

3. This ball bearing effect reduces the resistance to flow that ordinarily occurs between angular cement and sand particles, reducing water of convenience demand by two to ten percent and increasing both flexural capacity and density.

4. More workable fly ash concrete can be easily placed and consolidated at lower slump than can ordinary portland cement concrete,' further reducing water content.

Chemical Advantages. Fly ash is a pozzolan and reacts with calcium hydroxide generated by portland cement. hydration to form stable, durable cementitious compounds. This pozzolanic activity is benefici.albecause:

I. Weak, leachable calciu m hydroxide is chemically captured by the fly ash and fixed in strong cementitious compounds, increasing flexural strength and density, while decreasing permeability.

2. Pozzolanic activity continues at a high rate long after cement hydration slows to provide higher flexural strength.

Increased flexural strength derived by the use of fly ash may be utilized to decrease section thickness and save money. H thickness is maintained, longer useful (ife will result.

For additional information regarding designing concrete mixes for flexural strength, contact your nearest Pozzolanic technical representative.

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Number 20FLY ASH FOR HIGH STRENGTH

CONCRETE As recently as J960, concrete com

pressive strengths over 6,000 p.s.i. were rarely achieved and seldom used in the design and construction

concrete structures. By 1972, Material Service Corp. in Chicago was regularly producing 9,000 p.sj. concrete for the construction of high-rise concrete structures. High strength concrete of 12,000 p.s. i. and above is becoming fundamental to the architecture and engineering of the ]980's.

Achieving high strength concrete is a great deal more complex than merely adding more cement to everyday concrete mixes. Decades of testing and research have been required by the finest technical people in the world to achieve the kind of reliab!e, consistent results required to make high strength concrete a safe building material.

.Attention To Mix. Research has shown that careful attention must be paid to all ingredients of the concrete mix, choosing from among the many to select those which produce the best results. Careful appraisal of available materials has shown that "the use of a good quality fly ash is a must in the production of highstrength concrete and a fly ash witb an ignition loss under three percent or less is preferable".' In terms of the capacity for generating high strength.

'thestfehgtn gainacfiTeved fromihe use of 1percent to 15 percent fly ash (by weight of cement) cannot be attained through additional cement."

Strength Requirement. In line with the innovative thinking required to develop high-strength concrete

comes a Change in the age at which strength is commonly specified. It is well known that the level of achieved strength is time dependent. The older the concrete, the stronger it will become. Delaying design strength requirements to later ages makes it infinitely more practical to produce high strengths. While fly ash concrete is beneficial in many ways up to the normally required 28 days, it has a higher rate of strength gain at later ages than portland cement. This later age strength gain allows higher strengths to be achieved than can be achieved with portland cement alone.

High strength concrete requires vel)' careful appraisal of available materials, care in production and, of course, the use of.a high quality fly. ash.

Please contact your nearest Pozzolanic technical representative for more information or specific questions about fly ash iii high-strength concrete.

I Blick. R. L.. "Some Factors Jnil uencing High,Slrerlglh Concrele:' Modern COf1creh', VoL:lG. No. 12. April J!I7:l

.

Technical [ffi(u]ilJLl1ill1J~

Number 21FLYASH FOR

PUMPED CONCRETE Pumped concrete must be designed

so that il can be easily conveyed by pressure through a rigid pipe or flexible hose for discharge directly into the desired area. I

Changes in design mixes to improve pumpability can enhance (he quality of the concrete. These changes may result in improved concrete strength and impron:d concrete performance but they cdn be more costly. However, by using PozzoIan ic fly ash. pumpability can be ensured. quality of the concrete impro\'ed and tile costs controlled.

Mix Homogeneity. The designer must be aware of the need to improve gradation and maintain uniformity of 111(' various materials used in the pumped mix in order to achieve greater homoge'neity of the total mix.~ Three mix proportioning methods frequently \lsed to produce pumpable cOllcrett' are:

Maximum Density 01 Combined Materials

Maximum Density Least Voids Minimum Voids Minimum Area Mixes must be designed \\lith several

factors in mind: J. Pumped concrete Illust be 111m\.' with enough fine material and water

to fill internal voids. 2 .. Since the surface area and \'(Jiel

content of fine material below 300 microns control the liquid under pressure, there must be more of these .sizes than in iI

Illi x.G~!JeJ,allY):ipeaking..tJle. Ji It( '.I

the material, the greater the control.

. :3. The cuarse aggregal(' gradillg should !Jt~ continuolls and often the .siliid (:OI1I('llt mllst bt, increased by up to fi\'(' pern.'nl al the expense of the C()itrs('i'

aggregate so as to balance the sao micron Smm fraction against the finer solids,

Fly Ash Effective. Unfortunately, adding extra water and fine aggregate leads to a weaker concrete. The usual remedies for this are either to increase the cement content, which is costly, or to use chemical admixtures, which also can be

and may lead to segregation in marginal mixes. There is another and far 1110re effective alternative: Pozzolanic fly {lsi\.

There are many advantages 10 including Pozzolanic fly ash in concrete mixes [0 be pumped. Among them are:

l. Particle Size. Fly ash rneeting ASTM Specification G18 must have GG percent passing the 325 (45 microll)sieve and these fine particles are ideal for void

Just a small deficiency in the mix fines can often prevent successful pumping.

2. Particle Shape. Microscopic examination shows most fly ash particles are spherical and act like miniature ball bearings aiding the movement of the concrete by reducing rriCtional losses in Ilw pump and piping, Studies have shown Ihilt fly ash can be twice as effective as n'l1H:nl in improving workability ancl. therefore, pumpability.:

3. P6zz.olanic Activity. This chemical reaction combines the fly ash particles with the calcium hydroxide lii>t'rated through tile hydration of cement to form additional cemenlilious compoullds \\1.1i5..I} jncrei,lsg.....(J.~ I.U': r.eJe....!.ilw.nglll_

4. Water Requirement. Excess walt'r in pumped mlxt's resulting in ()\'(:r six illcil slumps \\'ill ollt'n Cill/St' Ilwtl'rial

(continued HI bock J

I:\("J :iU' -72 Fi('ld H{'ft'rt"tH T i\.liHIHal- .\fJrf lIlt fit" 1/1.' Ir II .';/IJ11 tllrlll ("HIIO('[('/UI f~(uldlllJ.!. ...... Pull SII.. -, 1~ J7~~ I' -; .... :-'j'p 'portiUllilig C01H"rl'lp fi1i~{s ',-\el 1'lIhltl Hilt/if .""" __ /1" p. :!7. J Missner. H.5.. "Eflecl of Inerl Mineral Additi\'l~s un \'urkabiJ.it:r," Significance of Tests and Propertie:i ,J! Concrete ond Concrete Making MOleria/s. STP 169-A American Society iorTesling and X!alerillts. Phillldfclpitl

Technical [Q3(UJLLlL[El])JlM

FLYASH REDUCES HEAT OF HYDRATION Number 22

Use of fly ash.in mass concrete has been well documented by many sources, including the U.S. Army Corps of Engineers and Bureau of Reclamation. Typical examples of projects utilizing fly ash in mass concrete include the Hungry Horse Dam, additions to the Bonneville Dam, Hoover Dam repair, the Canyon Ferry Dam, the 1-205 Bridge piers and the Hood Canal Floating Bridge anchors.

Mass concrete is defined as [any volume of concrete with dimensions large enough to require that measures be taken to cope with generation of heat from hydration of the cement and attendant volume change to minimize cracking. "1

Guidance is available in ACI 207-2R-73, Effect of Restraint, Volume Change and Reinforcement on Cracking of Mass Concrete," to determine when existing conditions warrant mass concrete practices.

Smaller Rise. Replacement of cement by pozzolanic fly ash results in a decreased temperature rise in fresh concrete.2 This is especially important in massive structures such as dams and large bridge piers where a large temperature rise can lead to cracking.

Hydration of portland cement generates heat very qllicklycausing the concrete temperature'to rise. This increase comes at an early age where plastic strain capacity is high and the concrete readily accepts expansion. With age, the temperature falls to ambient. This occurs where plastic strain capacity is very low and may cause concrete to crack.

Criteria. Established criteria exists for selecting proportions'for mass concrete in ACI207-1R-70 "Mass Concrete for Dams and Other Massive Structures" and are:

1. Utilize the largest maximum sized aggregate possible while maintaining minimum sand contents, thereby requiring 'the minimum amount of cementitious materials [or a given strength level.

2. Maintairi slump at a minium to minimize water demand and cerrientitious materials content.

3. Utilize low heat cement. 4. Make judicious uS~9LiJ.dfflixJure,s. 5.Pfoportion for Hie-highest fly ash con

tent within the constraints 01 time and strength.

Fly Ash Benefits. Fly ash is a tremendous aid as it generates only 15 to 35 percent as much heat as cement at early ages. This coupled with long term strength gain and physical fly ash characteristics benefit mass concrete by:

1. Significantly reducing heat gain to reduce thermal cracking. '

2. Functi0ning as a workability aid in typically lean, coarse mass concrete mixes.

3. Acting as a water reducing agent by allowing approximately two to ten percent reduction in water content.

The rate and amount of heat generation is dependent upon the fineness and qualily of the fly ash and its proportion in the total mix. When Type II cement is used with fly ash, the heat generateq by the pozzolanic reaction up to the age of approximately 28 days will be, on the avera,ge, about 50 percent less than the cement it replaced.

For large structures such as concrete dams, not only is the possibility of thermal shrinking and cracking reduced, but the lowered, heat of hydration also decreases the amount of artificial cooling required. Thus larger placements can be made and construction expedited at lower cost.3

For designers who want to minimize heat problems in mass concrete, the following caloric test results reflect the decreased heat that can be obtained through the use of a specification fly ash in concrete mixes.

SAMPLES CURED AT 73 F. MIX DAY CALORIES Type I Cement 3 67 Type I Cement 7 81 1 Part Type 1/ 2 Parts Fly Ash 3 35 1 Part Type l/ 2 Parts Fly Ash 7 37 2 Parts Type 1/ 1 Part Fly Ash 3 48 2 Parts Type 1/ 1 Part Fly Ash 7 61

'For fUrther Tnformaiiqri-or-speclflc' questions regarding the use of fly ash to reduce heat 01 hydration, contact your nearest Pozzolanic technical representative.

I CommiUee 116-1; 'O~menl and ConcreteTerminoiogy"; AC{ Manual of Cl?ncreie Practice, Part I; 1980.

2 Central Electricity Generating' Board; Applications of PFA In Concrete and Cement'; RIBA Product l)aICJ: London; March 1982.

l Abdum-Nur. Edward A.; "Fly Ash In Concrete"; /iigill1)ayResearch /3.oard; BulleJin No. 284; J~nual}' \961: p.28..

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echnical r83[U]rUL~

FLY ASH IN PRECAST/PRESTRESSED Number 23 CONCRETE PRODUCTS

Production of precast concrete products involves intricate, difficult patterns. Precast concrete products can be produced with or without reinforcement, but units typically consist of narrow, de'ep sections which are heavily reinforced making concrete placement vel)' difficult. Reinforcement typically includes the use of fibers, conventional reinforcing steel" and prestressing steel tendons, either pretensioned or post-tensioned or combinations thereof. Mixtures must have enough workability to flow well under vibration and totally fHl the form without segregation. Hand finishing is often required necessitating a mixture workable enough to allow for this kind of manipulation.

By definition, precast concrete products are cast and cured in other than their final

, positionl . This enables the use of reusable forms which, due to economic concerns, are cycled as rapidly as possible. For this reason, these concrete products generally achieve their competitive position in the marketplace by using a limited number of forms with a rather short production cycle, Normal production schedules allow for one usage of forms per day; however, 10 to 12 hour schedules are common. Accelerated curing, typically employed to enhance early age concrete strength for handling, shipping, and product utilization, accelerates the pozzolanic reaction of fly ash to help develop the necessary early strengths2

Concrete mixtures for these products are proportioned for high levels of performance"'at'earlya:ges~Co1TIpresslve'StrengthS' ' of 3500 to 5000 psi (24 to 28 MPa) are typicalty required at the time of form removal or stripping. These early concrete strengths are generally achieved with cementitious material contents of 600 to 750 Ib/cy (355 to 445 kg/cm). Conventional and highrange water reducing agents are often employed to attain workability at very low water content. Nonchloride accelerating admixtures are also sometimes used. While the early strength gain characteristics of fly ash has generally

been considered too slow for use in these mixtures, conditions are changing toward the use of fly ash in these applications. As is true Qf all mixtures used in precast concrete work, mixture proportioning and curing procedures used must produce adequate early strength or the turnaround time on forms or molds will be increased3 ,

While early age strength levels are required for stripping and handling, higher strength levels are required for the ultimate use of the products. The Use of quality fly ash meeting ASTM C-618 (class f) spedfications is a must in the production of high strength concrete of 6000 p.s-i. and higher4. The strength gain achieved from the use of 10 to 15 percent fly ash cannot be readily attained through the addition of a proportionate amount of cement.

Pretensioned hollow-core structural slabs are produced with no-slump concrete. It is consolidated and shaped as it passes through an extrusion machine. The particle shape of the coarse aggregate and the amount of fine aggregate are very important to workability. Fly ash is widely considered as a beneficial ingredient to increase the workability of these dl)', harsh mixess. Early strength performance of these mixtures using class F fly ash closely parallel mixtures without fly ash in terms of early compressive strength. No early strength reduction is apparent.

Although most concern is directed at obtaining desired early compressive strengths,-meseconcrefe pCrocfuds must possess durability to resist destructive attack from numerous environmental factorsG. Class F fly ash is seen as a major ingredient utilized in the production of durable concrete and as such should be included in any concrete subject to severe environments. For further information on the role of class F fly ash as an aid to durability, see technical bulletins #14 (freeze/thaw resistance), #15 (permeability). and #17 (sulfate attack).

(continued on back)

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Number 24FLY ASH FOR

CONCRETE PAVEMENT ash has been used in road paving

for more than 2,000 years. The Romans used naturally occurring

volcanic ash from Mount Vesuvius to cement the paving stones in their roadways. Many miles of this ancient roadway - although rough by our standards - still exist as a useable highway.

Today in Europe, paving stones have been replaced by modern day pavement - but a product almost identical to volcanic ash.is still used. In fact, most European highways have been constructed with fly ash in all levels, including the wearing course.

On this side of the Atlantic, it has been only in relatively recent years that we have begun to recognize the value of fly ash in concrete pavements.

Many States Use Ash. Roadways and interstate highways in Alabama. California, Georgia, Florida, Nebraska, Utah and approximately 20 other states and Canadian provinces have been successfully constructed with ash, many dating back to the early 50's and 60s. These roads are found in every type of clImatological condition that exists - from virtually subtropical to sub-zero.

In January of 1974. the Federal Highway Administration encouraged the use of fly ash in concrete pavement with its Notice N 5080A .which urged the states to allow partial substitution of fly ash for cement whenever feasible'. The FHWA indicated that the replacement of cement with fly ash of the order of 10 to 25 percent can be made giving equal or better concrete strength and durability. In addition, in January, 1983, the Environmental Protection Agency published federal procurement guidelines for cement and concrete containing ash which encourage the utilization of [Iv ash and establish compliance deadlInes.

Co-mpressivestren-gths.-Highway departments frequently specify a minimum 14-day flexural strength. These requirements can readily be met through the utilization of proper mix designs incorporating specification fly ash. Equal compressive strengths at all ages can be readily attained providing specification fly ash, properly proportioned, is substi

tuted for up to 25 percent of the cement. Some of the reasons that fly ash is used in

concrete paving have more to do with the physical characteristics of fly ash than the chemical and strength gain characteristics. With modern construction techniques - such as paving trains using slip form equipment ~ the fly ash facilitates placement of the concrete at lower slumps while maintaining excellent workability. This means less hand work for the paving contractor. , . and better surface texture and edge characteristics for the design engineers.

Denser Concrete. Using fly ash also results in a denser concrete, . _ and one that will have much greater ultimate strength and

Paving contractors are increasingly asking that Oy ash be used in their concrete because they are able to place the pavement or curb with less tearing and thus, a smaller

crew is required_ These are other advantages to using

ash which result in a stronger and more durable pavement:

.. Fly ash concrete pavement will improve the resistance of the concrete to sulphate attack,

.. The concrete will be more resistant to road salts and freeze/thaw action as well as reduced alka I 1/aggregate reaction.

.. In many areas of our C"ountry, fly ash also can help keep the initial cost of concrete pavement competitive with asphalt pavements_

Many Advantages. These are all valid reasons - and time tested advantages for producers and specifiers to request the use of fly ash in their paving concrete. The fact that the ancient Roman roadways still exist today is profound testimony to the wisdom of using bothJJy.ash.andconcfe.teiRwad

hnieal J]3(U][L[L~UOlf\J] Number 25FLY ASH FOR SOILS WORK

Five basic types of soils work commonly utilize Ily ash:

L Cement Treated Base (CTB) produced through a mixing plant

2. Soil Cement- produced by disking the cement and fly ash into in-situ soils.

3. Lime Treated Base/Type A- produced through a pug mill.

4. Lime Treated Base/Type B - produced by disking the lime and fly ash into in-situ soils.

5. Flow Fill Placement - produced by mixing large quantities 01 fly ash, sand and waterwith minimal orzero quantity of cement.

Cement Treated Base (CTB). This method most closely resembles normal concrete work because of the gradation 01 the malerial with which it is mixed. The mix is designed to achieve a given strength p.s.i. factor at a given age. . placed using a dump type vehicle ... brought to grade with a scraper ... and compacted with either rubber tired or steel drum compactors. Moisture is added after the material has been placed and graded and sometimes aller rolling.

This process makes replacement of cement with fly ash feasible with 15 \025 percent replacement common and up to 60 percent representing close 10 the maximum.

Design strengths can be anticipated at about the same ages as with straight cement utilization.

Soil Cement The gradation of materials used in the soil cement method resembles block and pipe mixes. Basically. small aggregate is used with cementing materials at minimum water contents and subjected to compaction. Large amounts 01 this type 01 work have

been done in the U.S. and Canada using lIyash replacements of up to 33 percent and as low as five percent.

With fly ash the soil cement surface will exhibit greater strengths over a longer period 01 time. For that reason. it is often used in the construction of road bases in housing developments.

Lime Treated Bases. The practice 01 using lIy ash and lime to produce cementitious bases is severa! centuries old, The process utilizes limE and. for the most part. naturally occurring water (either ground water or rainwater) to produce cement-like compounds.

Once the lime and flv ash have been

mixed together by means 01 (a) a pug mill or (b) disking into the soil, the normal pozza. lanic action between the lime and the fly ash begins.

This process initially uses either water introduced at the pug mill or applied to the surface of the designated area by a water truck. Over the long term, moisture from ground water and rain will continue to supply adequate moisture to sustain the pozzolanic activity of these two materials and thus generate continual strength gain.

Subgrade Application. This characteristic of slow strength gain usually is not detrimental because, in most cases. the material is being applied as a subgrade for asphaltic concrete or to stabilize in-silu soils. In these instances. high early strengths are not necessary, and may, in facl, be undesirable.

It must be remembered. however. that this is a soils product that becomes "concretelike," rather than concrete. and cannot, therefore, be expected to perform like concrete at early ages. It will perform in early ages in a manner very similar to normal, compacted soils. At medium ages (90 to 120 days), it will begin to acquire properties 01 low strength concrete. At later ages. it will begin demonstrating the properties 01 normal concretes.

Several projects where lime and fly ash have been used have shown extraordinary strengths (3.625 p.s.i. to 5.800 p.s.i.) at five to ten years.

Flow Fill Placement One of the more recent uses of fly ash is as the binding medium and auxiliary carrying medium.in a liquidly placed soil !ill. This method uses somewhat bighJ1Y.ash..contents.300 .\ol.DOOpocJndspe r cubic yard and. low. 10 to 100 pounds per cubic yard. or zero cement contents.

Zero Voids. This method is designed to produce a soils product that has zero air voids and high. inter-particle surface contact. Fly ash has just the properties for achie\'ing both criteria.

As a binding medium. fly ash partic:ies mteracl wilh the chemicals in water to form certain crystaline structures that i1ct a" a source of- internal stabilization ill the soil svstem. . II more than 7:2:; p.:-;,i. tu 1.1:ill p.s.i. IS required of the soil mass. il is recommendf::

lechnical LP5lWLLLLllilJ~1J~ FLY ASH FOR ASPHALTIC CONCRETE Number 26

The use of fly ash in asphaltic concrete is common practice in many parts of the United States and Canada.

Fly ash is most commonly used in this application where adequate fines in the local sand -are not available. However, even where adequate sands do exist, including fly ash in the mix design can improve the quality of the asphaltic concrete.

Fly Ash Ideal Choice. Whenever a mineral filler is required, fly ash is the ideal choice for two reasons:

1. The particle size of fly ash is virtually 100 percent minus 200 sieve. This means less asphaltic oil is required to fill the voids and, therefore, the result is a less expensive mix.

2. Fly ash promotes a denser mix and surface which assures a longer pavement life with less repair work required to maintain satisfactory surface conditions for traffic.

The tremendous increases in the cost of asphaltic oil make the use of fly ash extremely attractive even in areas where sands normally contain adequate fines for asphalt work.

The round, hard, spherical particle shape of the fly ash contributes a great deal to its ability to . minimizethearnountofoiLrequired for the mix ... and its ability to produce greater density in the asphaltic concrete. These round pa.rticles act like little ball bearings, much the same in asphaltic concrete mixes as in portland cement

concrete - promoting flowability

and compactability of the mix.

Reduces On.Justas this lubri

cating characteristic reduces the

need for more water in portland

cement concrete, it reduces the'

need for oil in asphaltic concrete

with obvious cost savings resulting.

The surface of the fly ash par

ticles are generally very hard and,

therefore, will not absorb the oiL

They have few crevices or rough

points to retain or demand oiL

Others Porous. Neither of

these attributes is true of other

mineral fillers. In fact, other min

eral fillers have a porous surface

which causes them to soak up

more oil. They are also angular

with many crevices and peaks,

increasing the need for oil to assure

proper fluidity and compaction.

Another very important factor

to consider in selecting a mineral

filler is the cost, in energy, to

produce it. A ton of fly ash-since it

is the by-product of a power gener

ation facility - costs zero BTUs of

energy. Manufacturing a ton of

cement by comparison, consumes

7.3 millio"n BTUs of energy. Similar

comparisons are relevant for lime,

other manufactured fillers or

alphaltic oiL

Because of the fact that it is a

by-product and not the product of

an energy-intensive manufacturing

. p~ocess, thE'!

Technical [B301l[L[LIETI1JWl

Number 28FLY ASH

AND HOT WEATHER CONCRETE Hot Mudl The statement is heard

often in the concrete industry. Rapidly setting concrete is generally considered a good thing. However, when the mercury goes above 80 degrees and as-placed concrete temperatures rise above 85 degrees, a complex set of problems must be solved.

Problems: Dehydration of concrete due to high temperatures, low humidity, wind and subsurface wicking aggravates plastic cracking and crazing. Increased concrete water demand due to high temperature and rapid cement hydration increases drying shrinkage and reduces strength.

Since cement generates 120 BTU's per pound of weigh~ it is important to reduce the amount of cement-generated heat. This can be done with fly ash which decreases the heat of hydration in the mix. During the first critical 24 hours, replacement of 100 pounds of cement with the same amount of fly ash reduces the heat of hydration by 19 percent, but does not sacrifice any strength or durability features. Since fly ash minimizes water requirements by two to ten

Other methods that the ready mix producer and the contractor use to keep concrete cool during hot weather are:

Ready-mix Producer: 1. Design mixes for strength

using higher percentage of quality fly ash and reducing cement.

2. Use a chemical retarder in prescribed dosage to slow initial heat build up.

3. Spray aggregate piles to cool by evaporation.

4. Chill water or add shaved ice to mix water.

5. Keep spray on cement silo. 6. Reschedule to night pours. Contractor: 1. Soak subsurface for mini

mum of two hours before placing. 2. Keep spray on rebar ahead of

pour. 3. Erect wind screen. 4. Erect shade covering. 5. Don't allow ready mix trucks

to stand in the sun. 6. Screed immediately and

don't overwork the concrete. Spray on surface evaporation retardant if applicable.

7. Immediately after finishing, al)plycuringcon!p()ul!9(\yJ}it~pig-111ented) or pond IIle concrete.

pefcenf;ilisnofnecessary the mix with water during placing and thus strengths can be mailitained.. Pumpability, placeability and finishability also are improved by adding fly ash to hot weather

mixes because they will m~ve more fluidly throughout placmg and finishing processes.

For further information or specific questions about using fly ash for hot weather concrete. contact your nearest Pozzolanic technical representative.

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Tech IIB3CUJrL[L[gJ]]W FLY ASH FOR CONCRETE PIPE MANUFACTURING

Class F fly ash has been used success

fully il1 the manufacture of concrete pipe for

more than 30 years. It has become an almost

indispensable ingredient to the dry, harsh

mixes typically used in modern pipe manu

facture.

The manufacture of concrete pipe is

accomplished by two different processes,

one using extremely dry concrete mixtures

and the other using plastic concrete mix

tures. DI)' cast concrete pipe are produced

utilizing mechanical compaction and/or vi

bration to consolidate the dry concrete

mixture into a form which is removed as

soon as the casting is finished. With removal

of the form. the green pipe is carefully

transported to its place of curing. Acceler

ated, atmospheric curing is typically used to

obtain early age performance.

Wet cast concrete uses plastic concrete

placed and compacted in a form which re

mains around the pipe until certain levels of

performance are achieved. Wet cast pipe

may be manufactured by the spinning pro-

cess. to remove excess water and air to

produce great density and low permeability.

Fly ash has found widespread use in the

manufacture of concrete pipe as a cementi

tious material and as an aggregate mineral

filler to enhance quality and economy.

The major reasons for the use of fly ash

in concrete pipe are:

HostIle CondItions. Pipe is inevita

bly subject to hostile conditions. It is most

....oftenus.ed to convey sewage . .to arid through. sewage treatment plants. where hydrogen sulfide attack may erode Portland cement concrete as if it were butter. Properly pro-portioned mixtures containing fly ash make the concrete less permeable, and pipe containing fly ash may be more resistant to weak acids and s