Hrwr + Fly Ash+Silica Fume

8/12/2019 Hrwr + Fly Ash+Silica Fume

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Purdue University

Purdue e-Pubs

Joint Transportation Research Program Civil Engineering

1-1993

Chemical Admixtures of Highway Concrete:Fundamental Research and a Guide to Usage, Part

I - Background, History and Future Applications.Sidney [email protected]

Keisuke Matsukawa

This document has been made available through Purdue e-Pubs, a service of the Purdue University Libraries. Please contact [email protected] for

additional information.

Recommended CitationDiamond, S., and K. Matsukawa. Chemical Admixtures of Highway Concrete: Fundamental Researchand a Guide to Usage, Part I - Background, History and Future Applications.. Publication FHWA/IN/

JHRP-92/07 pt.I. , Indiana Department of Transportation and Purdue University, West Lafayette,Indiana, 1993. doi: 10.5703/1288284313483
http://docs.lib.purdue.edu/http://docs.lib.purdue.edu/jtrphttp://docs.lib.purdue.edu/civlhttp://docs.lib.purdue.edu/civlhttp://docs.lib.purdue.edu/jtrphttp://docs.lib.purdue.edu/


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Final ReportCHEMICAL ADMIXTURE FOR HIGHWAY CONCRETE

FUND MENT L RESE RCH AND A V I P ~ 9 ~ f ~ r j

y

Sidney DiamondProfessor of Engineering MaterialsKeisuke MatsukawaGraduate Research Assistant

Joint Highway Research ProjectProject No.: C 36 37DDFile: 5-8-30

Prepared as Part of an InvestigationConducted by

Joint Highway Research ProjectEngineering Experiment StationPurdue Universityin cooperation with the

Indiana Department of Transportationand the

U.S. Department of TransportationFederal Highway AdministrationThe contents of this report ref lect the views of the authors who are responsiblefor the facts and the accuracy of the data presented herein. The contents do notnecessarily reflect the offiCial views of policies of the Federal HighwayAdministration. This report does not consti tute a standard specification orregulation.

Purdue UniversityWest Lafayette IndianaMarch 31 1992Revised February 22. 1993


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TECHNICAL RepORT STANDARD TITLE PAGE1. R.p . " N .. 20 GOY.' '.' Acc. 'on N .. 3, R.clpl.n' Co' . I .... N . ,

FHWA/IN/JHRP-92/74. Ti.r. and Sub'I,I. 5. Reoot Do'. Harch 1992CHEMICAL ADMIXTURES FOR HIGHWAY CONCRETE: Revised F b r u a ~ 22. 9 . ,FUNDAMENTAL RESEARCH AND A GUIDE TO USAGE P. , f . ",,;nll O'lI"niIOl;o" C .


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i

ACKNOWLEDGEMENTS

The first-named writer is very much indebted to a large number of people whohelped in the accumulation of information concerned with State DOT practices andspecifications. Representatives of seven state agencies kindly allowed themselves tobe interviewed and provided detailed discussions of present practices and futureprospects. He is equally indebted to a number of people associated with the chemicaladmixture industry for frank discussions concerning current and future products andtheir characteristics. However any errors in his interpretations of current practices andof he characteristics of the various admixtures are the the responsibility of the writer.

The writers also wish to thank two of their colleagues at Purdue Professor W LDolch and Ms Janet Lovell for their advice and assistance in various phases of theseinvestigations.

e also thank Ward Malisch and the Aberdeen Group for permission toreproduce the comprehensive listing of chemical admixture marketers given in Part ITable 1

The understanding and forebearance of the project advisory board membersMessrs. R Smutzer of INDOT and L M. Heil E Hoelker and S Forster of FHWA areacknowledged with great appreciation.


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Table of Contents Part I)LIST OF TABLES viiLIST OF FIGURES viiiINTRODUCTION. 1HISTORICAL PROSPECTIVE ON CHEMICAL ADMIXTURES 2THE CONCRETE ADMIXTURES INDUSTRY 4ADMIXTURE SELECTION AND SPECIFICATION BY STATE DOTS 11A GUIDE TO SPECIFIC CLASSES OF CHEMICAL ADMIXTURES 12

Air Entraining Agents 12Accelerators 14Retarders 17Water Reducers. 20Water-Reducing Retarders 22Water-Reducing Accelerators. 24High-Range Water Reducers (Superplasticizers) 28High-Range Water Reducing and Retarding Admixtures 30Admixtures Not covered by ASTM Specifications 34Corrosion Inhibitor Admixtures 34Antifreeze Admixtures 35Waterproofing Admixtures 36Stop-Start Admixtures 36Alkali Silica Reaction Preventing Admixtures 37Shrinkage-Reducing Admixtures 37

SOURCES OF FURTHER INFORMATION 37MINERAL ADMIXTURES AND HIGH-PERFORMANCE CONCRETES 39

Mineral Admixtures 39Natural and Artificial Pozzolans 39Fly Ashes. 40Silica Fume. 40Ground Granulated Blast Furnace Slag 41High Performance Concretes 41

ADMIXTURE COSTS. 42A PROSPECTIVE ON THE USE OF ADMIXTURES IN CONCRETEFOR TRANSPORTATION-RELATED STRUCTURES. 45


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LISTOFTABLES

PageTable 1. Markete rsof chemicaladmixturesasof Jan 1 1992 5Table2 AdmixtureCostEstimates 44


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v

LIST OF FIGURESPage

Figure 1 Product sheet describing an admixture marketed specifically forhighway applications ........................................................................... 9Figure 2 Product sheet describing one of the newer air'entraining agents ...... 15Figure 3 Product sheet describing several different accelerators marketed by a particular manufacturer for different purposes...................... 18Figure 4 Product sheet describing a waterreducing admixture. Otherbenefits are also claimed for this product ......................................... 23Figure 5 Product sheet describing a waterreducing setretarding admixture, marketed by the Sika Corporation ............................................ 25Figure 6 Product sheet describing a waterreducing accelerating admixture. The accelerating component is said to be an inorganic

formate and the admixture is said to be free of chloride ................ 26Figure 7 Illustrative product sheet for a highrange water reducer(superplasticizer) ............................................................................... 31Figure 8 Product sheet for a retardingtype high range water reducer........... 32Figure 9 Product sheet describing a corrosion inhibijor based on calciumnitrite ................................................................................................. 36


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conversion of gypsum to ettringite and to monosuifate. as monitored by x-ray diffraction andspecially-devised differential scanning calorimetry techniques. The corresponding effects on thephysical properties of the fresh cement paste were followed by rheological measurement using amini-slump cone.This protocol was then applied to study the effects of several different naphthalenesulfonate and melamine sulfonate superplasticizers on cements of various characteristics.n extensive list of more than 5 technical fmdings was compiled, some of them entirelyunexpected. The conclusions arrived at from the great mass of technical data and analysespresented included 1) that the influences of the naphthalene sulfonate and melamine sulfonateforms of superplasticizer with the specific cement components re similar to each other, 2) thatthe rheological effectiveness of superplasticizers depend on maintaining a reasonableconcentration of polymer molecules of the proper chain length in solution, in spite of thetendency of the hydrating cement to absorb these molecules, 3) that this balance betweenabsorption and maintenance of superplasticizer in solution was strongly conditioned by whetheror not a sufficient concentration of sulfate ions w s also maintained - in cases where it was not,the paste stiffened rapidly and the superplasticizer was ineffective, 4) that with superplasticizerpresent pattern of early cement hydration was considerably modified. or example, the fonnationof ettringite was very rapid over the ftrst few minutes and then stopped for some hours. in

contrast to its slower but continuous rate of formation without superplasticizer. 5) thatsuperplasticizers substantially reduce the amounts of crystalline ettringite and monosulfateproducts detectable, presumably due to the poor crystallinity of these products formed in thepresence of the superplasticizer, and 6) that the alkali ions most often Na) used to neutralize thesulfonate groups in superplasticizers rem in in the pore solution when the superplasticizers readsorbed, and are converted to alkali hydroxide, thus increasing the potential for alkali-silicareaction.


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GENERAL INTRODUCTION

This project was originated with two distinct but related objectives in mind:1 To review evaluate and interpret current practices with respect

to the use of chemical admixtures in ordinary concrete. This effortmight hopefully lead to a set of recommendations as to how currentgeneration chemical admixtures coming into widespread use in othersegments of the concrete based construction industry can best be applied for highway and other transportation-related concretes. Theproduct of this portion of the study was visualized as being in the formo a guide to current types of admixtures and to benefijs to be expectedfrom their utilization. Information on comparative costs and cautionsconcerning proper use and possible problems might be included.

2 To carry out basic research in the area of how chemical admixturesfunction in concrete. Chemical admixtures are normally dissolved in themix water. Their effectiveness to a considerable extent depends onmaintaining a reasonable concentration level of these materials in thefluid phase of the concrete over the relevant period of activity. Very little information on concentration levels exists. Thus one objective wasto develop methods for determining this and measuring changes inconcentration over time. We then proposed to use this newly developed technology to study the behavior and interactions o one or morecurrent generation admixtures used with a range of cements includingcements typically encountered in Indiana highway concretes.


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This Final Report is thus a composite of tw parts designed separately to meetthe two objectives. Separate introductions sections have been provided for each part.

Part I deals with the complicated overall situation with respect to the use ofchemical admixtures in concrete and contains sections on the history of chemical admixtures for concrete on the unique features of the chemical admixture industry aspresently constituted and on typical practices in State Departments of Transportationwith respect to specifications and control of the use of chemical admixtures. It then provides a profile of each of the major types of admixtures used in the various segments ofthe concrete construction industry including chemical type promised benefits degreeand area of current usage and possible problems. Some idea of the potential for use ofthe specific admixture in various highway applications is provided.One of the many complications that has overtaken this study during the course oftts compilation is the very substantial growth of the use of certain mineral admixturesincluding fly ash of several types silica fume and ground granulated blast furnace slagin concrete both for highway and non-highway applications. The use of mineral admixtures strongly influences the conditions under which chemical admixtures function inconcrete in some cases the reverse is true as well. A section briefly describing thesemineral admixtures and their influences on the behavior of chemical admixtures is included at the end of Part 1

Part II reports the resutts of a complex and detailed series of laboratory investi-gations that formed part of the Ph.D. thesis investigation of Dr. Keisuke Matsukawacarried out under the supervision ofthe writer. Dr. Matsukawa chose naphthalene sulfonate superplasticizer as his pilot chemical admixture. He developed a specific analysiSfor the content of this material in the fluid phase: i.e. the original mix water and after setthe solution remaining in the pores of the hardened cement paste. He then developedthe procedure for conducting repeated analyses at short intervals to determine how theconcentration changes over time. At the same time he measured the effects produced


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by the presence of the admixture on the concentrations of the cations and anions nor-mally present in cement mix water. e also monitored the changing physical propertiesof the cement paste and finally the corresponding changes in gypsum hemihydrateand ettringite contents of the solid phase. All of these analyses taken together providefor the first time a complete and accurate picture of what the specific admixture at thespecific dosage used was doing to the particular cement it was used with. This providesa pattern for laboratory investigations of admixture effects that had not previously beenavailable.

The pattern was then applied to various dosage levels of two different naphtha-lene suHonate superplasticizers on three different cements. Subsequently the patternwas applied to study the effects of malamine sulfonate superplasticizer .

The effectiveness of superplasticizers was found to be intimately associated withthe concentration of sulfate ions being maintained in the mix water y the particularmaterials used. In order for a superplasticizer to maintain its dispersing action and notundergo slump loss it must maintain a reasonable concentration in solution. Cementmixes that do not do so were found to stiffen and set prematurely. This response wasfound to be specifically associated with a low concentration of sulfate ions solution;adding sulfate reduces the early uptake of superplasticizer and allows the admixture tocontinue to function properly.

The superplasticizer level in solution was found generally to be quickly reducedby uptake into the early cement hydration products. The degree of this uptake was in-versely correlated with the maintenance of superplasticizer effectiveness. Surprisingly itwas found that the early uptake of superplasticizer by some cements was under somecircumstances spontaneously reversible after a few hours.

It was found that the pattern of ettringite development in early cement hydrationwhich strongly influences setting behavior is much affected by the by the presence andconcentration of the superplasticizer.


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v

Most commercial naphthalene sulfonate superplasticizers are alkali neutralized. Itwas found that the use of such an admixture strongly affects the alkali and OH ion relationships that develop in the pore solution of the r s u ~ i n g concrete. The neutralizing alkali ions normally Na+) are immediately detected in the mix water. s the dissolvedsuperplasticizer polymer chains are taken up y the hydrating cement, the sulfonateS03H-) charged sites on the chains are lost to the solution, but they are immediately

replaced y an equivalent number of hydroxyl OH-) ions. The net effect is a permanentincrease in the concentration of OH- ions, and a corresponding greater potential forsubsequent alkali aggregate reactions.

Studies were also carried out on the behavior of melamine sulfonate superplasticizers. These constitute a second family of superplasticizers that are not used as widelyas naphthalene sulfonates superplasticizers, but still account for a significant proportionof total usage. hey were found generally to behave in the same manner as naphthalene sulfonate-based admixtures.

While these studies did not specifically address the effects of mineral admixturesLe. fly ash, silica fume, etc.) on the behavior of the chemical admixtures studied, the

basic knowledge developed provides a means of predicting what such joint effects mightbe. Thus it represents a penmanent contribution to understanding the chemical fundamentals of what may take place when complex combinations of admixtures are used inconcrete, for highway purposes or otherwise.


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PART I

CHEMIC L ADMIXTURES IN HIGHWAY CONCRETE: BACKGROUND HISTORYAND FUTURE APPLICATIONS


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INTRODUCTION

The historical background to this compilation stems in part from, and relates directly to, the changing nature of State agencies responsible for highways and othertransportation facilities. Historically, the present State Departments of Transportationare direct lineal descendants of state highway departments, which had as their primeand often sale charge the construction and maintenance of highway networks. A typicalexample is the present Indiana Department of Transportation (INDOT), which came intoexistence in 1989 as a direct descendent of the former Indiana Department ofHighways (IDOH). There has been comparatively little new construction activity sincehighway departments changed over to DOTs, and practices, at least with respect tconcrete, have probably not changed very much

By far the largest volume of concrete placed under State Highway Departmentauspices was for highway pavements, with much smaller volumes being specified forappurtenant structures and specialized structures such as bridge decks. Separate specifications have been, and continue to be listed for bridge deck concrete and forstructural concrete; such concrete necessarily is of higher standard than the

specifications usually require for pavement concrete.Historically, the only chemical admixtures normally specified for pavement concretes were air entraining agents, used to insure an adequate air-bubble system forfreeze-thaw durability. Other admixtures often were permitted, especially for structuraland bridge deck concrete. While these admixtures were speCified on the basis of theirmeeting AASHTO (and indirectly, ASTM) standards, they have been selected andused primarily on the representations of admixture suppliers and the experience of localcontractors.

The actual extent of use of admixtures on highway iobs has always been muchless than on building construction and other concrete applications. Consequently, StateHighway Department engineers, even concrete specialists in the central state highwaylaboratories and offices of the Engineer of Materials, seem to had only limitedopportunities to become familiar with them. A further factor was (and is) the relativeuneasiness of most civil engineers in dealing with complex chemical matters. Thus


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when present trends began to develop involving the development of many new chemicaladmixtures, widespread use of these in conjunction with fly ash and in some cases silicafume, and highly successful appHcations of both to building construction and other nonhighway applications, the need for additional guidance specifically directed towardState DOT engineers became manifest. This portion of the final report represents anattempt to at least partially meet this need.

To some extent the time scale under which this work was undertaken, and delaysdue to the writer's medical difficutties, have reduced the need for this report. Otheragencies have been active in th intervening period in promoting and providing guidanceon admixture use. For example, the Federal Highway Administration has in the past fewyears conducted a series of demonstration project meetings under the designationEffe.ctive Utilization of Portland Cement Admixtures , to acquaint State DOT engineers

with the fundamentals of chemical admixtures in concrete. Transportation ResearchBoard Committee A2-E05 has recently published a 50-page guide on Admixtures andGround Slag for Concrete (Transportation Research Circular 365, Dec. 1990 . TheAmerican Concrete Institute has maintained an active program of seminars in variouslocations entitled How to Effectively Use the Newest Admixtures , and a SeminarCourse Manual (SCM-23 (90)) is available. Nevertheless, the writer feels that thiscompilation still can fill an important need.

HISTORICAL PERSPECTIVE ON CHEMICAL ADMIXTURES

For many years concrete recipes contained only Portland cement, coarse andaggregate, sand, and water. The use of other prospective components, includingchemical admixtures, were actively discouraged by well respected and influential agencies on the grounds that they were simply not needed and could be detrimental.

After the accidental discovery that air-entraining agents might be successfullyused in concrete to prevent freeze-thaw damage, and the widespread adoption of thisfirst chemical admixture, the way was opened for the development and marketing of agreat variety of chemical materials to use in concrete mixes for a variety of perceivedpurposes. Companies specializing in this area were founded, and a recognized chemical admixture industry came into being. n the Untted States, after s a period of development, ASTM codified these chemical admixtures into several classes, based on theirintended effects. Set accelerators, set retarders, water reducers, and combination pur-


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pose admixtures were recognized and standardized tests were adopted to measure andhopefully predict their effectiveness. AASHTO subsequently adopted essentially thesame system for the special needs of highway and transportation agencies.

More recently, the class of official chemical admixtures has been broadened toinclude superplasticizers ( high-range water reducers ) and combined superplasticizerretarders.However, the official admixtures have been in recent years augmented by arapidly growing collection of chemical admixtures designed for new purposes.Prominent examples include admixtures to help prevent corrosion of steel in concrete,stop-start admixture packages that penmij a suspension of the hardening of fresh con

crete and ijs resumption after as much as several days, antifreeze admixtures, admixtures to reduce the cracking induced by excessive shrinkage by lowering the surfacetension, and others. These are in addition to specialized admixtures designed for useby cement manufacturers ( i.e. grinding aids) and admixtures for specialized forms ofconcrete construction such as shotcrete, pumping aids, etc.

The picture has become even more complex wijh the much more widespread useof mineral admixtures such as silica fume, fly ash, and ground granulated blast furnaceslag. Silica fume acts in concert with superplasticizers to substantially reduce the waterdemand in concrete, to a far greater extent than can be accomplished by superplasticizers alone; however, by ijself, silica fume generally increases water demand. In consequence, high performance concrete based on silica fume incorporation necessarily requires accompanying use of superplasticizer (or sometimes very heavy doses of waterreducers). Some fly ashes have similar characteristics, and high perfonmance concretesbased on fly ashes usually also require heavy doses of on or the other of thesechemical admixtures. However, fly ashes and slags are also widely used in more conventional concrete, including concrete for highway purposes. Indeed, chemical admixture manufacturers are currently marketing new generation admixtures, such as airentraining agents, said to be designed to work specifically wijh concrete containing minerai admixtures.

Because of this proliferation, the present state of affairs with regard to chemicaladmixture selection and use in concrete may be even more confusing than has beenpreviously. Certainly combinations of chemical admixtures are more frequently prescribed, and combinations of chemical and mineral admixtures are becoming recognized tools in the deSign of practical concretes. The potential for problems, particularlyfor problems reflecting negative interactions, is thus muttiplied. On the other hand, thenew tools have provided so much improvement in concrete properties and in potential


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durabiltty that their judicious use cannot be avoided if the responsible' engineer is toproperly fulfill his function in producing the best and most durable transportation structures at the least cost,

THE CONCRETE ADMIXTURES INDUSTRYTo understand how and what admixtures should be used in a given Situation, it is

helpful to understand how concrete admixtures are produced and marketed, Such information is not usually available in published form, and because of this some StateDOT engineers tend to be a little bewildered by some of the seemingly arcane practicesassociated with the concrete admixtures industry.

Concrete admixture marketing began in the United States. The first productsmarketed to concrete producers were air entraining agents, based on a waste product

, derived from tree stumps ( vinsol resin, short for very insoluble resin - material leftover after various more soluble components had been extracted or other uses). Wasteproducts of various kinds have been widely used in chemical admixture industry formulations since then.

However, in more recent years, admixture manufacturers have typically movedbeyond by-product compounding, and have employed extensive technical staffs andconducted highly sophisticated chemical and manufacturing research to formulate andefficiently produce their newer products.

The chemical admixtures industry in the United States has grown from a few producers to a relatively large number o firms. The joumal Concrete Construction annually publishes a classified list of suppliers of various materials to the concrete construction industry. In the December 99 issue, the lists include 38 suppliers of accel'erating admixtures, 30 suppliers of air-entraining agents, 26 suppliers o retarding admixtures, 29 suppliers o water reducing admixtures, 33 suppliers of superplasticizers,and 17 suppliers of corrosion inhibiting admixtures. The separate lists, of course; contain many duplications, and only 65 separate firms are included. The combined listingof all of these firms is provided as Table I through the kind permission of ConcreteConstruction.

These firms encompass a wide variety of sizes and characteristics. The industryhas historically consisted of a small group of companies marketing nationally, and arather larger group of companies marketing regionally, often wtth limited product lines,but sometimes with great success due to their ability to service local markets. Whilemarket share figures are not ordinarily released, t is generally understood that


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5

Table 1.Harketers of Chem ical Adm ixtures as of Jan. 1, 1992

(Listing Provided through the c our te sy of the AberdeenGro up,Publis hers of CODcreteconstru cti on)1. Air-Entraining Agents

Anti ydroAreal ChemicalsAXIH Concre te TechnologiesCarrollConchemConcret e Producers Dept Store Corm ixConstr uction Chemicals OFCDura fiber Group/Hill Brother s Chemicallas tize llEucli d ChemicalFosroe

Fox IndustriesF ri tzChemicalGibeo\ I RGraceHandy Chemicals IAIH LTesting EquipmentMast er Builders\J RMeadowsHonex ResourcesNox-CretePQSelect Product sSinSpeeco Industries Sternson Gro upTexmasticInternationalUniversal Fas teningConcrete Accessori es

2. AcceleratorsAnti Hyd roAqua-F loAreal Chemicals XIMConcrete TechnologiesBerylex National SalesCarrollCem tech Laboratorie sChargar

ConchemConcrete Producers DeptStoreConprocoConsp ecMarket ing Mfg.CormixConstruction Chemicals Dow Chem ic alUS

Durafiber Group/Hill Brothers ChemicalOur-O -WalEuclid Chemic alFosroeFoxIndustriesGemiteProducts YRGra ceHandy Chem icalsA CHornIAILafarge Calc iumAluminatesLambertMaster BuildersYRMeado sMonex ResourcesNationa l VarnishNordics -Vik ing Concre te P roductsQuikr ete CompaniesSinSouthern Grouts Korta rs SpeccoIndustriesSpray-Crete In dustriesTexmastic InternationalUniver sa l Fast en ingConcre te Accessorie s

3. Reta rdersAnt i HydroAreal Chem ica lsAXIM Concrete TechnologiesBorem coSpecial ty Chem ica lsConchemConcrete Producers DeptStoreCormixConstructionChemicalsDuraf ib er Group/Hill Brothers Chem icalEucl id ChemicalFosrocFoxIn dustri esFritz ChemicalGeistlich InternationalYRGraceumann ReimerI A IKaster Bui lders KonexResourcesOldNorth HfgOnodaLKScofield Sin


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Spec co IndustriesSpecrete-IPTexmastic InternationalUniversal Fastening &Concrete Accessories4. Vater Reducers

Anti HydroAreal ChemicalsXIM Concrete TechnologiesBerylex National SalesBoremco Specialty ChemicalsConchemConcrete Producers Dept StoreCormix Construction ChemicalsDurafiber Group/Hill Brothers ChemicalEuclid ChemicalFosrocFox IndustriesFri : ChemicalGeistlich InternationalGibcoU GraceHaarmann 6 ReimerHandy CheillicalsI A ILambertKaster BuildersKonex ResourcesNox-CreteL M ScofieldSikaSpecco IndustriesSpecrete-IPTexmastic InternationalUniVersal Fastening &Concrete Accessories

5. High Range Vater Reducers(Superplasticlzers)Anti HydroAreal ChemicalsXIM Concrete TechnologiesBoremco Specialty ChemicalsConchemConcrete AccessoriesConcrete Producers Dept StoreCormix Construction ChemicalsDurafiber Group/Hill Brothers ChemicalEuclid ChemicalFibrinFosrocFox IndustriesFritz ChemicalGemite ProductsGeochemical

6

GibcoU R GraceHandy ChemicalsI A ILobeco ProductsMaster BuildersMetalcrete MfgHonex ResourcesNorcem Concrete ProductsNordic s-Viking Concrete ProductsNox-CreteOnodaSikaSpecco Industriesspray-Crete IndustriesTexmastic InternationalUniversal Fastening 6Concrete Accessories

6. Corrosion InhibitorsAtlas Minerals & ChemicalsConcrete Producers Dept StoreElkem MaterialsFosrocFox IndustriesGemite ProductsY R GraceIP SystemsMaster BuildersMonex ResourcesNorcem Concrete ProductsNordic s.Viking Concrete ProductsNoxCreteOnoSikaSpecco IndustriesUniversal Fastening& Concrete Accesaories


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significant portion of the market is dominated by the two largest producers, W. R. Graceand Master Builders, Inc. Informed estimates suggest that their combined share of thetotal chemical admixture market in the n ~ e d States may be in excess of 70 . Otherlarge producers include Cormix (incorporating admixtures formerly marketed by theGifford Hill Co.), Euclid Chemical, Fosroc, Monex Resources, and Sika.

The large firms (and some that are not so large) are often owned by internationalconglomerates, many foreign owned. They have access to current technology drawnfrom many chemical and physical fields, and maintain extensive and well-equipped laboratories. Chemical admixture industries are very active in European countries and inJapan. While the industry was started in the United States, like many others, leadershipmay have passed to overseas competitors. The European industry, in particular is wellorganized and there is an active European Federation of Concrete AdmixturesAssociations (EFCA) headquartered in Frankfurt.

In the United States, recent experience indicates that the stability of variouscompanies fluctuates drastically. Buy-outs, reorganizations, and sales of product linesare common. The industry is hotly competitive; new developments formulated by onefirm are often quickly matched by competnors. Patent positions play an important role;the larger companies have extensive legal staffs and file many patent applications.

Despite this emphasis on modern technology and international development,marketing strategies seem not to have changed very much. From the beginning, technical service and problem solving have been most important components of the marketing effort, to a much greater extent than in other fields. Admixture suppliers have traditionally supplied a full service package to their customers, and have included the costsof such services in the price of the admixture. These services often include provision forproviding and maintaining admixture dispensers, i n o n ~ o r i n large jobs, and investigatingcauses of field problems.

This tradition generally continues, atthough some firms now market admixtureson a commodity basis, w ~ h o u t the service, but at lower prices. Indeed, there are someindications that a few ready mix concrete producers are blending at least some of theirown concrete admixtures from industrial raw materials.

Specific admixtures are often marketed under a general product line deSignation,and differentiated from each other by supplementary letter or numbers.

The usual practice in the industry is to guarantee that any product delivered willconformance with ASTM (or AASHTO) specifications, but not to guarantee that thespecific product will always be formulated from the same components, nor indeed toidentify the components beyond certain vague class designations. This industry prac-


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tice is unlike that in most European countries, where admixture manufacturers typicallyare required to disclose the actual chemical ingredients used in their products. Thus inthe United States the actual composition of a given admixture may change without thename of the admixture being changed. Indeed, different formulations may appear underthe same product name in different regions. Conversely, the same product may carrydifferent names in different markets.Certain firms produce a specially-designated line of admixtures for the highwaypavement market, which m yor may not include the same materials produced for saleto the general concrete industry. Typically such admixtures are provided only in bulk,rather than in pre-packaged containers. A product sheet describing one such admixture( Masterpave ) is provided as an illustration in Figure 1. This and other product sheetsreproduced in this report are tor illustrative pu[poses only no endorsement of any ofthe specific products or pf the claims listed is expressed or impljed,

Admixture companies characteristically produce a product sheet for each of theiradmixtures. These typically contain (1) a description of the product 2) the advantagesclaimed, 3) applicable ASTM or other standards that are claimed to be met (4) recommended dosage rates, (5) technical data (6) information on compatibility wijh otherproducts (7) precaufions that should be observed. Manufacturers generally adviseclose conformance to the suggested dosage rates and to the listed precautions.Manufacturers providing service to clients will generally, buf not always so indicate bysome statement like For further assistance, o n s u ~ your local X Company representative.

The product sheet that was shown in Figure 1 to illustrate a special productaimed at transportation departments is rather less specific than most product sheetsaimed at the general market. Most product sheets are rather more detailed in theinformation provided. Product sheets from various manufacturers are included as illustrations in the various sections describing specific types of admixtures. Again, noendorsement of these specific products is implied,

One particular component of some admixtures deserves special mention. It hasbeen well established for many years that the presence of chlorides in concrete promotes corrosion of embedded steel, and efforts have been made by many in the concrete field to eliminate all possible sources of chloride in reinforced and prestressedconcretes. In accord with this trend, the current version of the ASTM standard specification for chemical admixtures for concrete C 94 - 90) carries the proviso (Section 5.4)that At the request of the purchaser, when the admixture is to be used in prestressed


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9

U I L a E R S

DESCRIPTION

ADVANTAGES

WHERE 7 USE

Products Information

MASTER PAVE is a ready.to-use,liquid admixture expressly recommended for pavement concrete. Itmeets ASTM C 494 requirements,specificaJly: IncllIased Strength-compressiveand flexuralMASTER PAVE admixture aids In theproduction of concrete which hasthe following special qualities Inthe plastic or hardened state:Plastic Concrete

Irnpnwed TextIMg ow.cterI tIcs Gntater Edge Stability andSlump Control

This admixture can be used In allpaving-related concrete requiringnormal set In combination with alithe benefits of an effective, waterreducing admllctura MASTERPAVEadmixture Is chloride-tree iJess than10 ppm by weight of cement).MASTERPAVE admixture can be usedwith all alr1trainlng admixtures

Relative Durability to Damagefrom Freezing and Thawlng-weilabove industry standards Reduced Wlter Content Requiredlor a Given Workllblllty Normal-Settlng Charactanatlcs

Improved WonWIllity usingless watlBf Reduced Segregation IncrU&ed Placing RateHardened Concrate

IncrAMd Compress.'ve andFlexural Strengths Higher arly StrengthapProved under AASIfTQ CAD andASTM specHicatlons, IncludingMaster Builders air-entrainingadmixtures.When used In conjullCtlon withanother admixture. each admixturemust be dispensed separately Intothe mix.

QU NTITY 7 USE MASTERPAVE admixture is rec0mmended for use at a rate of 4 to 6 ozper 100 Ib (260 to 390 ml per 100 kg)of cement for most concrete mixesusing average concrete Ingredients.Because of variations In job condl-

tlons and concrete materials, dosagerates other than the recommendedamounts may be required. In suchcases COIltact )'Our local MasterBuilders representatlYe.

Figure 1. ~I+ '. ~ .... ; - ,~ : ~ .

ProdUct sheet describing an admixture marketed specifically forhighway applications.


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PACKAGING

TEMPERATUREPRECAUTION:

10

MASTERPAVE admixture is suppliedin bulkc re should be taken to preventM STER P VE from freezing II itfreezes thaw al35 F (2 q or al:IoveFor additional Information onM STERP VE admixture or on itsuse In developing a concrete mix

M STER UILDERSMP OY NQ CONCRETE WORlOWIOECLEVEI.AND. OHIO 4


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concrete, the manufacturer shall state in writing the chloride content of the admixtureand whether or not chloride has been added during its manufacture .

While comparatively little prestressed concrete s used for transportation purposes, highway bridge decks are heavily reinforced, and in most of the country areheavily subject to steel corrosion damage. Under the circumstances, the restriction ofthis provision to prestressed, rather than to both prestressed and reinforced concrete,seems curious. Some state DOTs have instituted more stringent requirements as part oftheir standard specifications. For example, the Indiana Department of Transportationspecification cames provisions to the effect that no chloride can be deliberately added toan admixture n its formulation, and the total parcentage of incidental chloride must bespecified by the manufacturer.

SELECTION AND SPECIFICATION OF ADMIXTURES BY STATE DOTS

n the United States chemical admixtures for concrete generally are supplied asconforming to one or another of the relevant ASTM standards: ASTM C 260 - 86,Standard Specification for Air-Entraining Admixtures for Concrete; ASTM C 494 - 90,Specification for Chemical Admixtures for Concrete, and ASTM C 1017 - 90, StandardSpacification for Chemical Admixtures for Use in Flowing Concrete. For highway andtransportation use, the American Association of State Highway and TransportationOfficials has adopted the substance of two of these speCifications as M-154 (for ASTMC - 260), and M - 194 (for ASTM C-494). The spaciflcation for admixtures for flowingconcrete has so far not been adopted by AASHTO.

n addition to the standard speCifications referenced above, most State DOTsadd spacific requirements and exceptions based on local experience or practice. Thevolume of highway and transportation business has been historically great enough thatsuppliers will ordinarily meet such local amendments.

The usual practice is for prospective admixture suppliers to submit samples andr e s u ~ s of testing directly to the relevant division of the State DOT. If the r e s u ~ s aresatisfactory the supplier is placed on the Approved List of suppliers for that particularclass of material.

Some chemical admixtures, particularly the newer ones, are not covered byASTM or AASHTO specifications. n some cases at least, appropriate spacifications areunder development, but the process is slow and because of commercial considerationsthe necessary consensus may be d i f f i u ~ to reach.


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12

A GUIDE TO SPECIFIC CLASSES OF CHEMICAL ADMIXTURES

Air Entraining Agents

As has been previously mentioned, air-entraining agents were the originalchemical admixtures, and re probably still the most widely used of the various types.Theirwidespread use is based not only on their ability to prevent freezing and thawing

d a m ~ g e but also on the desirable buttery character induced into the consistency ofthe ftash concrete. Other perceived benefrts include lower penmeable and absorptivity ofthe hardened concrete, and in some cases possibly increased resistance to the effectsof sulfate attack and of alkali ggreg te attack.

ASTM C 260 (and its AASHTO M-154 equivalent) specify certain perfonmancecharacteristics not related to the primary function of the admixture, namely (a): a limijation on bleeding compared to the bleeding of the same concrete without the admixture;(b) a limitation on changes in setting time (no more than 1 1/4 hour retardation or acceleration); c) limitations on both compressive strength and flexural strength reductions atany age of test to no more than 10% of the reference strength wHhout the admixture),with the flexural strength limitation being optional, and d) a limijation on length changeto be no greater than 120% of that of the reference concrete after 14 days of drying.Strangely, the dosage of the admixture for these tests not prescribed, and is presumablythe m a n u f a c t u r e ~ s normal recommended dose rate .

The primary functional requirement specified for air entraining agents is that resistallce to freezing and thawing measured by Procedure A of ASTM Test Method C-666 be established at a relative durabili jy factor of 80%. Again, the dosage of air entraining agent to use to establish such effectiveness is not specified.

In point of fact, the effectiveness of a given ir entraining agent in preventingfreeze-thaw damage is well understood to be a function of the stability of the entrainedair void system under the necessary field handling conditions, and in the last analysis, tothe success of the agent in achieving a bubble spacing factor of the order of 0.01 in. orless. The freeze-thaw resistance of concrete is usually linked to the total air volumepercentage, which may be specified differently for different classes of concrete and different conditions of exposure. However, the air entraining agent specifications neither


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require nor permit the option of determining the effectiveness of a given air entrainingagent in producing a given level of air entrainment or a given bubble spacing factor atany particular dosage rate.

Air entraining agents are ordinarily adsorbed at air-water interfaces, and reducethe surface tension of the water significantly. Some air entraining agents (those with in-soluble calcium s a ~ s precipitate solid or gelatinous films around entrained air bubbles.The sand content and gradation influence the amount of air entrained, especially in leanmixes, and such factors as cement content, consistency of fresh concrete, mixing ef-fectiveness, temperature, and vibration may affect the air bubble system produced by agiven air entraining agent.

Air entraining agents have been formulated from various classes of compounds.The classic 'vinsol resin products are primarily impure abietic and pimeric acids derivedfrom pine stumps or from tall oil processing and neutralized, commonly wijh sodium hy-droxide. Alkyl aryl sulfonates{ which are classic detergents) alkyl suHates, and phenolethoxyates are among the other classes of compounds that have been used.

One of the particular characteristics that set air entraining agents apart tram mostadmixtures is the extremely low dosage of active ingredient actually used. Air entrainingagents are usually supplied as liquids which lend themselves to accurate batching byautomatic dispensing eqUipment, but the actual content of surfactant batched is nor-mally very low; values substantially less than 0.1 % by weight of cement have beenquoted. The small materials cost is usually offset by the greater yield (air beingsubstantially less expensive than the volume of concrete it displaces), and by othersavings sometimes attained in redesigning the concrete mix - for example reducing thesand content. The resuiting very low net cost of the air entrainment is one factorresponsible for its widespread use.

The dosage requirements in field applications, while small, m y be influenced bymineral admixtures, especially silica fume and fly ash. The carbon content of the fly ashis of particular importance, since some of the admixture m y be quickly adsorbed by thecarbon and its air entraining effect lost. The influence of silica fume is less straightforward, but there have been suggestions that some tradijionally effective air entrainingagents do not produce as satisfactory an air bubble system when used with concretecontaining silica fume. artiy in response to such concems, some manufacturers haverecently marketed new generation air entraining agents said to be specially effectivewith concretes incorporating silica fume and fly ash.

According to the current listing of producers of various types of concrete admix-tures published in the December 1991 isSue of Concrete Construction, 30 different firms


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currently market air entraining admixture in the United States. the actual variety ofproducts sold is substantially larger than this, some firms marketing a number of different air entraining agents.

A representative product sheet for one of the newer air-entraining agents is provided for illustrative purposes as Figure 2.

Accelerators

Accelerators are a class of chemical admixtures used primarily to facilitate coldweather concrete placement. A subsidiary use of these materials is to overcome a tendency to slow set; for this purpose they may be an element in a carefully compoundedprescription admixture which otherwise would cause excessive retardation.

There is considerable confusion in the field as to whether accelerators are primarily supposed to accelerate concrete setting, or to accelerate the rate of strength gainafter setting. ASTM C 494 -90, Standard Specification for Chemical Admixtures forConcrete, defines a Type C ( accelerating) admixture as one that does both, but thetwo uses are not necessarily equally addressed by a given kind of accelerating admixture. The performance requirement of that specffication for Type C admixtures requiresthat the time of initial set be advanced at least 1 hour, but not more than 3 1/2 hours,from that of the reference concrete, and the time of final set be advanced at least 1hour. With respect to e ~ y strength gain, the requirement is that the 3-day compressiveand flexural strengths be increased at least 25 and 10 , respectively, over that of thereference concrete. The specification also requires that there be no loss in compressive

s t r ~ g t h at 7 or 28 days, and that compressive strengths at 6 months and 1 year be atleasf 90 of those of the reference concrete. With respect to flexural strengths, thepermitted effect over time is somewhat different; the speCification is that there be noloss in flexural strength compared to the reference concrete at 7 days, and that the flexural strength at 28 days be at least 90 of that of the reference concrete. There aresubsidiary requirements on shrinkage, and on freeze-thaw durability for air-entrained,concrete used with an accelerating admixture.

Historically the premier accelerating admixture has been calcium chloride, whichis still the most effective accelerator available, and is extremely inexpensive to boot.Accelerators based on calcium chloride are available in liquid (solution) or in solid fOrm,and are extensively marketed. However, as indicated earlier, the association of chlorideat moderate concentration with corrosion of steel in concrete has rendered calcium


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15AS7ERBlJILJlERS

*tion

Admixture for Entraining Air in ConcreteDESCRIPTION:

ADVANTAGES OFAIR ENTRAINMENT:

ADVANTAGES OFMICIIOAIII

FEATURES BENEFITS:

M1CRO-AIR is an air-eotlaming admixture whiCh gives concrete extra pmlec-lion by ClliIsfu'Q ultra-statile ilIr bubtllesIMt are strong, smalll flO Closelyspaced-a charactenatic especiallyuseful In the types 01 concrete knownfor the,r difficulty to entrain andThe entrainment 01 optimum air COIl eniin COI'ICf8te results in the followingimprovements in concrete Quality: I _ s e d reslstanc.l to damage from:='::Oe::,1IId 1 $Caling Onatty I m ~ flabIIlty 01 airentlllinment Improftd eIr-vOid In hardInedconc:ret. IrnPl'O*l ability 10 entrain and retain.... In Iow-"ump concnte; CDncIWIRMdy ID U_SOlut lon Is the ptOperstrength lor accurate dispensing.Compatible for U_MICROAIRadmixture Is compatible with concnJIecontaining other admixtUleS Of admixturu systems-water-redUCltS, highrange water.f'8ducet8, .:ceIerators,/8tan::1ers, d e n l n ~ A Id watef repel-lents. It also Increases the entrainedair eonIent of concntemade with airentraining portland cement.The use 01 MICROAtR air-.eotralnlnga:im1xllM withMula' Buildln FolzoIIth"iIdn'Ilxtures forms. desirable combination tor producing the highest q u a t ~I'IOmIaI Of Ilghtweight conCJ8te.. HMY)"weight concrete normally does notcontain entraioed air.

maintaIn the air content desIred.EV1ln when used at a lower dosagerate than standard air-entrainlng adm . lures. MICRO-AIR mllel Ine require-ments 01 ASTM C 26(), AASKKl M 154,CRD-C 13 and other Federal and SlateSj)e l g l _ t I I ~1n._ _ _ I t _ I y ~ I O _ ( O I _ . I I n I N _ ~ I : I _ p O i n t O l p l _ . . . n t ; r o d t t _ . . . . ._ai'__ ... ~ ~ l t b o O " G _ I n I N _ ............

Reg. Us. Pat. & Tm. Ol .

Figure 2, Product sheet describing one of the newer air-entraining agents,


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USAGE INFORMATION

PACKAGING

16

1. MICi'lOAIR admu[tull ,s a ready-lOuse SOilltion. Do nol m l ~ il with anyOlner acm'XIUre.2. Ace MICRCAIR aomlxture to theCl)1lCl ete miX using a dispenserassigned for 3 r ~ n t r a i n l n g aam,xlures: or adO manually usmg a suitable measllfing device that ensuresaccuracy Within plus or minus 3%01 tile reQuired amount.3. There is no standanj dosage rate forMICRO-AIR aomixture. The exactQuantity of air-entraining admixtureneedec:l for a given air content ofconcrete is no pnldiclabje becauseof dlfferences in concrete-maklngmalen als. TypiCailactol' wh.ch mightinfluence Itle amount of cur entrainedtemperature, cement, sand grading,sand-aggre


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chloride-based accelerators suspect or entirely banned by many agencies, not only forreinforced and prestressed concrete, but for pavement concrete as well.

Generally speaking, admixture manufacturers have divided accelerators in chloride-based (primarily calcium chloride), and non-chloride based accelerators, and often advertise non-chloride based accelerators without specifying the active agent beingused. Users tend to make the reasonable assumption from this that non-chloride accelerators are all about the same or at least similar to each other in their effects in concrete. This is very far from the truth.

Calcium nitrite is an effective concrete accelerator, but it also has the very desirable property of acting as a steel corrosion inhibitor. It is marketed by at least one firmas a corrosion inhibitor, with the concrete acceleration properties being incidental.

Other non-chloride accelerators market include products based on calcium formate, and especially in complex admixtures, triethanolamine. Little triethanolamine isused by itself. A variety of other organic and some inorganic compounds have beenlisted in the Itterature as having accelerating properties but are rarely used in commercial practice.

Sodium thiocyanate based accelerators have been marketed by at least onecompany. However, their use has been questioned for concrete containing steel, on thebasis of possible increased susceptibility of the included steel to corrosion. The question is controversial since evidence has been presented by the manufacturer that at thelow dosage rate specified sodium thiocyanate based admixtures did not deleteriously affect the corrosion rate or the time to corrosion.

Non-chloride accelerators tend to be fairly expensive and require relatively highdose rates. A considerable potential market would seem to exist for an inexpensivecompound that would act as an effective accelerator without deleteriously affecting otherproperties of the concrete.

An illustrative product sheet is provided as Figure 3. This sheet is from amanufacturer who stresses the availabiltty of several different formulations, includingcalcium chloride, calcium chloride blended with corrosion inhibiting components, and achloride-free accelerator; thus the user may make his choice depending oncircumstances (and budgetl).

etarders

Chemical admixtures to retard the setting of concrete constitute a major class ofadmixtures. Some admixtures for accomplishing this are specified as Type 8 or


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19

RECOMMENDED CONCRETE PRAC71CESCOLD WEATHER CONDmONSConcrete should nOI be placed if ambient tempenlluresare apected 10 remain below 4O F uniCS$ concretetempenrures can be mailIIained above that level. ConCTete should 001 be placed in frozen iorms, even whena c c e l e f a W l ~ i o t u t e s are used, as concrete flatworkplaced on ground rnay take many bolUS to teaChinitial and final sets. AdditiOnaJ.Jy, stteJigtb pinmay beadvendyaffected.

WINDY CONDmONSCncking caused by plastic shrinkage due to highratcs of evaporation may be controlled by the ColIowint method$: Erection of windbreaks Usc of fog sprays or othu suitable curing methods Usc of suitable admixtures

SOt.rrHWESTERN REGIONSSan Antonio, C:xasSU-341-6182SOUTHERN REGIONAtlanu, Geotgia404-955-0039

.CURINGPropel concrete curing practices are eucntial forobtaining optimum concrete pe:rf'OIlDallCe. Sufficientmoi$ture and iavorabk tmlper.lI;ures must be maintained in order for me coocme [0 develop desiralproperties. This isespecially important durinS the fintseven clays.

QUALI1Y CONTROLR.ecommended AC or NRMCA proc:e:I.Ul'eS should befollowed for the addition of materials, maer cycle timeand plant slump (uurol.. P1m1 comrol sbouk1 alsoiDd.udc ~ air checks in ac.cwdance with ASTMC-113 or 1.

SOt1THEASTERN REGION' FIorido13-967-6626

MID-ATLANTICCOASTREGIONGreensboro, North CafolilIa9 1 9 3 7 ~

MONE.... RESOURCESoIf . . . ull 1


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LU

retarding admixtures in the ASTM C- 494 specification. There is a considerabledegree of overlap with Type D admixtures, which are water-reducing retarders. Indeed,most substances used as retarders are also intrinsically water-reducers in the sensethat they are surtace active and reduce the water demand. For example, of the variousclasses of substances that were said by one authority to be commercially used asretarders (Iignosunonates and their derivatives, hydroxycarboxylic acids and their s ~ sand modifications, sugars and other carbohydrates, and heptonates related to sugarsand starches), only sugars and other carbohydrates were said not to have intrinsic waterreducing properties.

A considerable number of inorganic acids and s a ~ s especially those whose calcium s ~ s are insoluble and form films around cement particles, also act as retarders.However, for various reasons they are not much used in practice.

Unlike accelerators which provide some acceleration of both setting and strengthgain after setting, retarders function primarily as set control agents. They are of courseused mostly in hot weather to overcome the rapid setting pattem that is a natural featureof high ambient temperature. Retarders are particularly helpful in lengthening thepermissible period after bat ching that vibration can be used, and in avoiding cold jointsby enabling adjacent layers to be vibrated into each other.

ASTM C-494 reqUires Type B retarders to increase initial set time at least 1 hourand not more than 31/2 hours, and to increase final set time not more than 3 1/2 hours.Compressive and flexural strengths after 3 days are required to be at least 90% of thecontrol concrete, and there are restrictions on the amount of increase in shrinkage thatmay be induced. Despite the fact that retarders are most commonly used at highambient temperatures, the time of setting measurements are specified to be carried outat 73 F

Water Reducers

Water redU ing admixtures (Type A in the ASTM C-494 classification) are designed to reduce the water demand of a given concrete mix while at the same time notmarkedly influencing other characteristics such as air entrainment behavior or settingtime. The action is often described as a plasticizing action, and accordingly, waterreducing admixtures are sometimes called plasticizers. The specific admixturesmarketed under this category, however, have only a limited water-reducing effect at

. dosages that can be used, and ASTM C-494 requires that only a 5% reduction in waterdemand be demonstrated. A newer category of chemical admixtures that are much


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2

more effective in reducing water demand, the so-called superplasticizers or high-rangewater reducers (HRWRs) are designated as Type F admixtures. These must provide atleast a t 2 reduction in water demand to meet the specification requirement.

Nearly all, if not all, of the surface active materials used as water reducers alsohave some retarding action. To accommodate the desire for the plasticizing effect without at the same time causing extensive retardation, most commercial water reducersare compound admixtures, in which an accelerating agent is included to compensate forthe retardation caused by the active plasticizing chemical. In past years, chloride-bearing accelerators were commonly used; currently, because of the growing sensttivity ofmany agencies to incorporation of any chloride in concrete, a non-chloride acceleratorusually triethanolamine is often used. If large amounts of accelerator are used, an accelerating water-reducing admixture can be produced.

In addition to the water-reducing effect ASTM C-494 Type A admixtures arerequired to maintain both initial and final set times to not more than 1 hour earlier and 1-112 hours later than those of the control concrete. The water reduction is required toeffect a compressive strength increase of 10 over the control concrete at 3, 7, and 28days. Long term compressive strengths and flexural strengths at any age must be atleast equal to the controls. A limited increase in shrinkage is tolerated.

Commercial water-reducing admixtures are generally formulated from one ormore of a restricted class of materials: lignosulfonates hydroxycarboxylic acids andhydroxylated polymers of various kinds. However, many other substances have beenreported to have similar effects.

Lignosulfonates are derived from the sulfonation of wood pulp, and tend to berelatively high molecular weight polymers of complex and ill-defined molecular structure.Wood sugars of various kinds are usually present. Since these sugars would induceexcessive retardation they are usually removed from lignosulfonates used as Type Awater reducers. Lignosulfonates also tend to entrain air, and an air-detraining agent issometimes incorporated into the final admixture.

Hydroxycarboxylic acids used in water-reducing admixtures include ottric, tartaricmucic, gluconic salicylic heptonic, and malic acids. Unlike lignosulfonates these tendto be pure chemicals. They are generally used in the form of sodium satts, which arevery soluble and they tend to have a considerable retarding action at higher dosagelevels.

Hydroxylated polymers used in water reducers are usually partially-hydrolyzedpolysaccharides derived from corn starch or other naturally occurring sources. They are


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hydrolyzed to relatively low molecular weights, and do tend to exert a retarding action inaddition to their water-reducing effect.

The term w a t e r - r e d u c e ~ ' is something of a misnomer. The admixture may usefully be incorporating into concrete without changing the water content, so as toincrease the fluidity or workability of the mix. The slump increase produced is a functionof the dosage level. Over the usual range and with properly designed concrete, a givendosage will produce about the same slump increase regardless of the initial slump of theconcrete to which it is added. For a given dosage, hydroxycarboxylic acid - based waterreducers are slightly more efficient than lignosulfonate - based water reducers.

The increase in workability is usually partly lost during the hour or two aftermixing. Notwithstanding that the slump I over time with plasticized concrete isusually greater than without admixture present, the residual slump at any given time isgenerally greater.

When the mix is redesigned to take advantage of the reduced water demand,the effectiveness of the plasticizer depends somewhat on the specific mix. Greaterwater reductions are possible at lower cement contents greater aggregate: cement ratios); at higher original slumps; and if delayed addition is used.

A typical product sheet for a water-reducing admixture is provided as Figure 4The manufacturer here claims superior finishing characteristics as well as the specifiedwater reducing effect.

water-Reducing Retarders

Water-reducing and retarding admixtures are classified as Type 0 admixtures inthe ASTM C 494 specifIcation. Paradoxically, since most water reducing admixtures dohave retarding effects, these dual-purpose admixtures may be in fact simplersubstances than single-purpose admixtures that are supposed to only retard set.

Many water reducing retarders are based on IignosuHonates; generally they contain high sugar contents, to help provide the requisite retarding action. Water-reducingretarders based on hydroxycarboxylic acids and on hydroxylated polymers are alsocommonly used.The ASTM functional requirements for this type of admixture separately addressthe water reducing and the retarding functions. The water demand must be reduced atleast 5 compared w ~ the control concrete. The retardation effect is required to resuHin initial setting between 1 hour and 3 1/2 hours later, and final setting not more than 3-


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4

1 2 hours later than the control concrete. The l i m ~ a t i o n s on the effects on strength andshrinkage are the sameas those for Type A water-reducing admixtures.

Use of a single admixture for both the water-reducing and retarding effects hasthe obvious advantage of s i m p l i c ~ y However, the balance between the two functionsis not easily tailored for particular situations. One can increase the dosage, which willlead to both additional retardation and additional water reduction, or decrease it andundergo reductions in both effects. Nevertheless as a practical matter, water reducingretarders are widely used and generally work well. They tend to be relatively inexpensive.

OccaSionally water-reducing retarders are implicated in false-setting problems,and their use with cements that tend to be false setting should be carefully m o n ~ o r e dWhat appears to happen is that the admixture coats the interground hemihydrate in thecement sufficiently to interfere w ~ h and slow down usual rapid conversion to gypsum.The gypsum formation may be delayed until after the usual mixing cycle. A thickeningand in extreme cases, a false setting effect is produced that interferes with properconcrete placement. Usually a second mixing or an extended mixing will cope ~ thiseffect.

A product sheet for a polymer-type water-reducing retarder is provided for illustrative purposes as Figure 5.

Water-Reducing Accelerators

These admixtures, unlike most water-reducing retarders, are formulations containing a substantial amount of separate set-mOdifying, i.e. accelerating, component.This is necessary to overcome the intrinsic retarding effect and then provide the desiredadditional accelerating effect .

These admixtures are classified as Type E in the ASTM C-494 speCification. Thespecific functional requirements combine those for Type A (water-reducing) and Type C(accelerating) admixtures. The late strength requirements are those of Type A

Unlike water-reducing retarders, this category of admixtures is relatively littleused in practice. The need to regulate the degree of acceleration needed to overcomecold-weather or other problems is perhaps more difflcuij to satisfy in a combined admixture.

An illustrative product sheet is provided for an admixture of this type as Figure 6Note that the manufacturer stresses that the acceleration is accomplished using a non-


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25

Plasiocreie 161 RPolymer-type, water-reducing,set-retarding admixtureDescription: Plastocrete , 61 R is a polymer type admixture.It is a non-air-entraining, water-reducing, set-retardingadmixture. Plestocrete 161 R contains no chlorides.1I meetsthe requirements of ASTM C-494 Type O.Where to Use: Use where retardation is needed. Use wherehigh strength, cost-effective concrete is needed. Use whereincreased workability is needed. Use in mixes with areduced cement content Use in all concrete where highquality is required.Advantages: High structural quality concrete. Saves cemenL.equal strengths with 4 to 1sack/cu yd reduction in cementHigher strength .2O higher compressive strength withequal cement Set-retarding_.initiai set will be retardedapproximately 2040 . Increases wOrkability. Contains nochlorides.Dosage: 3-5 fI ozl100 Ib cementPackaging: 5-gal pails, 55-gal drums. and bulk..Shelf ute: Unlimited. Protect trom free ing.Storage CondHions: Store above 30F , Protect rom freezing.If frozen, thaw and agitate before using.Color: Dark brown.Mixing: Add correct amount of Plastocrete 161 A at theconcrete plant Add manually or by automated dispenserdirectly into sandat weigh hopperor nto the water lineat thebatch plantUmltatlons: Do not mix with air-entraining agent Protecttrom freezing.Caution: ee product abel, MaterialSafety Data Sheet, TechOata Sheet, or contact Technical Service Department

Figure 5. Product sheet describing a water-reducing set-retarding admixture.marketed by the Sika Corporation.


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26

CONPl ST NChloride free, accelerating, water reducing admixture.USESTO accelerate the setting and early strength gainof Portland Cement concrete and mortar mixeswithout the introduction Of Chloride.AC s as a plasticiser. giving significant Increases inboth ultimate and early strengths. Typicalapplications include precast concrete, ccnCTeteplaced in cold weather, concrete lor repairs andmortars 101 briCkwork.ADVANTAGES

h l _Frft:Anti-frost:

High EarlyStrength:w..Reducing:Versatile:

TemperatureU .

Sate with all prestrnHd andreinforced concrete.&rty MttIng pt'Ovides Improvedretlltanc:e to frot1 attIck and earlierfinishing.Redue.s form .trlpping UmPllllUctzlng a c b acIIilate. waterreductiOn and ir1creasecI Ultimate-.n H used with ypes 01 PorUandCement and with all concreteand brickIaylnSl mortIIr mIxas,PartIc:uIIrty effectle In c:oncnI1I atlow temJMmu..... Allows contInUedpIlIeing of concNle. EnMnceswuther concreIe t ppIJcat\onI byreducing the waler com.nt II1dact:eIeniting hydration of cemenL

DESCRIPTIONCONPlAST NC is an admixture designed for usewith every type of Portland Cement. It isguaranteed completely free of all forms of addedchloride and is supplied as a light stTa .... coloredliquid instantly dispersible in water.The main active ingradient is an Inorganicformate.

The addition 01 the material to Portland Cementconcrete and mortar mixes reduces setting timesand accelerates the rate 01 strength gain andreSistance to frost attack.CONPLAST NC is also a plasticiZer which wherereqUired. enables the water/cement ratio to bereduced while still maintaining worKability. Suchreduction Will result in significant increases inboth ultimate and early strengths.STANDARDSCONPLAST NC complies with the requirementsof ASTM spedflcation C494 Type C.PROPERTIESCalcIum CbtoriOe Content NilSpeciflc Grmty. 1.27 at 70 F.freezing PoInt -3" F.Air Entrainment less than 1 additional air Isentrained.Compatibility: May be used with all types ofPortland Cements complying with ASTMspecification C150. Not suitable for use with highalumina cementThe effects of CONPlAST NC are highly effectivewith portland Cement mortar mixes. This avoidsthe use 01 chlo rkle In brickwor1< while providingearly sl1ength and frost lllSistance.CONPlAST NC is generelly compatible with otherFOSROC admlxtUfes, however, they shouldalways be dispensed separately.Setting Time: The addition of CONPlAST NC toPortland Cement concrete mixes aocelerates boththe setting and rate of strength gain.Comprenlw ~ Accelerates therate of strength gain.The strength improvements are most significantdunng the firsl18 twurs. If no change is madein the water/cement ratios, the ultimate strengthswill be Similar to those obtained using the samemixes without CONPLAST NC.

FOR MORE TECHNlCAL INFORMATlON 1-800-841-0445

Figure 6. Product sheet describing a water reducing accelerating admixture.. The accelerating component is said to be an inorganic formate andthe admixture is said to be free of chloride.


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Durability: Accelerated corrosion testingof steel inconcrete has snown that CQNPLAS7 NC does nOI8l1ec: the protection of steel afforded by cementagamst corrosion. even at 4 times the

r e ~ m m e n d e d dosage level.

INSTRUCTIONS FOR USEOO$llge:The optimum dosage for standard concrete andmortar mixes With all grades of Portland Cementis best determined by Site testing.As a guide the rate 01 addition is generally In therange of 30-45 fl. oz.I100 Ibs. 01 cemenL""An overdose 01 douol8 Ihe recommended amount01 CONPLAST NC will result ,n a slight increase ininitial acceleration, but will not alter the ultimatestrength or chalacteristics of the cured concreteor mortar.

Dispensing:The correct quantit y of CONPLAST NC should bemeasured by means of a recommended dispenser.FOSROC S Technical Depan:ment should beconsu lted regarding SUitable equipment and itsinstallation.The measured quantity o CONPLAST NC shouldbe added directly into the mixer. Best results areobtained When added at the same time with themixing water or at the end of the batch cycle.When the air lemperatura, al placing is below SOO FACI 306 recommended practice for cold weatherconcreting should always be followed.

STORAGECONPlAST NC has a minimum shelf life 01 12months providing the temperature range does notexceed 10" F. to 125 F. If these conditions areexceeded FOSROC should be contacted fOfadvice.

PACKAGINGCONPLAST NC is supplied by bulk delivery or in55 gallon drums.

W RR NTYF... .. . . . . . . . . . . . . . prOducU; 10 be . . . . 01 defotcIt. ....1a/if I WId ~ 1Jndoer_ warranry...will allIOd\atQI. ptOduct in10 0 be CIeIec i>


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chloride accelerator (an inorganic formate ), and is therefor safe for prestressed andsteel reinforced concrete.

High-Range Water Reducers (Super:plasticizers)

The development of this class of chemical admixtures has marked a considerablerevolution in the concrete field. In particular the availability of superplasticizers, used inconjunction with silica fume and fly ash, has made possible the development of a wholenew class of high-performance concretes. Superplasticizers can be, and are, used inmore conventional concretes, and in this section uses with conventional concretes arediscussed. High performance concretes will be discussed in a special section later inthis report.

Superplasticizers are specified as Class F admixtures in the ASTM C-494scheme. The operational requirement is that a water reduction of at least 12% beachieved. The reduction in water content is required to produce compressive strengthincreases of at least 40% at one day, wnh progressively lesser increases required atlater ages. At 6 months and later, the compressive strength is only required to matchthat of the control concrete. Only a modest flexural strength effect is required, the onlyincrease specified being 10% at 3 days.

The specification also includes requirements of only modest changes in set timeand modest shrinkage increases; these are identical to the corresponding requirementsfor water reducers.None of the water reducers discussed previously, wnh the possible exception of afew modified lignosulfonate products, can be used in concrete at high enough dosagesto meet the performance required from superplasticizers; retardation, air entrainment,and possibly other undesired side effects interfere. Rather, suparplasticizers generallyspeaking, represent entirely new chemical classes of admixture. Two families arecommonly recognized; those based on naphthalene sulfonate and those based onmelamine sulfonate, wtth the former far more commonly used. Actually, at least oneadmixture company has provided a superplasticizer blend containing both, and hasclaimed certain advantages for such a blend.

Naphthalene suijonates are actually naphthalene formaldehyde sulfonic acidsalls. They are produced by sulfonating naphthalene, polymerizing or 'condensing thesulfonated naphthalene wnh formaldehyde, and then neutralizing the sulfonate groupson the resulting polymer backbone wnh Na or Ca. Optimal chain length of the polymer


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is of the order of 10, but commercial products contain varying chain lengths, and oftensome sodium sulfate (if Na-neutralized.).

Melamine sulfonates are sulfonated melamine formaldehyde salts, produced bya rather more complex process, and are of a much higher degree of polymerization, onthe order of 100 or so. These materials were actually developed for other purposes,and subsequently were found useful in concrete. In contrast, naphthalene sulfonateswere a later, and deliberate development for use in concrete.

The general effects of the two classes of superplasticizer are mar1


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required to produce at least a 3 1/2 inch increase in slump and compressive and flexural strength levels of at least 90% of the reference concrete at all ages. Thesuperplasticizing admixture is required to have only minimal effect on the setting time.

Flowing concrete, as might be expected, tends to have a tendency to bleed andsegregate as the resutt of the loss of body in the fresh concrete. This can usually becounteracted by appropriate adjustment on the mix design, especially by increasing theproportion of fine sand.

For applications in which higher strength rather than flowing concrete are desired,the extent of water reduction obtainable can be very much higher than the 12%minimum value specified in ASTM C-494. At high dosage levels, water reductions up toabout 30% can be obtained with many naphthalene sulfonate or melamine sulfonatetype:superplasticizers, especially if they are added after a few minutes delay. Verymuch increased strengths can be produced at these lower water contents, even withoutgoing to silica fume or fly ash additions.

It is of course possible to use superplasticizing admixtures to reduce the cementcontent, i.e. by maintaining a constant or nearly constant water:cement ratio as the water demand is reduced. This of course results in an increased proportion of coarse andfine aggregate. Sometimes only the coarse aggregate content is allowed to increase.The resutting economy can partially offset the extra cost of the superplasticizer.

A illustrative product sheet for this class of admixture is provided as Figure 7.

High-Range Water RedUCing and Retarding AdmixturesThese admixtures, classified as Type G in the ASTM C 494 claSSification,

combine both superplasticizing and retarding effects, usually by blending a naphthaleneor melamine s u ~ o n t e superplasticizer with a conventional retarder. The functionalrequirements combine the retarding action requirements specified for Type B retarderswith the at least 12% water reducing action specified for superplasticizers. Because ofthe retardation, the 1-day strength requirement for superplasticizers (at least 140% ofthe control concrete) s reduced to 125% of the control concrete.Usage of such admixtures appears to be relatfvely restricted compared to the usage of non-retarding superplasticizers, atthough this may change in the future.

An illustrative product sheet describing a specific product falling into this class ofadmixture is provided as Figure 8.


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EUCON537HighRangeWalerReducingAdmix tureReta rdedSa' Type

EUCO N 537 ;sa fi fth generatio nadm ix tu refo rm ula tedsp ec if ica ll ytoex te n dthe work ing tim e01 fl ow in gconcre te at em pera tu resup to130 0 F.At normaldosagera te s, EUCON537compliesw it hthe para meters 01 ASTM C49 4 Type G adm ixtu re . E U C O N 537 has be enform u la te dwithoutany added ch lo ri des and c om p lie s w ith ACI201andAC t318 re qu ire m e nts for m in im alchlorideconte n t.

ca n be addedtoth e concreteslth eread ymixplant oraltheobsite . EUCON537 iscompatib lewithvinsol resintypeair-e ntra in ingadmixtures andmanyolhe radmixtures:however, all admixturesmust beaddedsepara te ly to th e mix. EUCON537 isrecommended fo rall typesofconcre te inc luding re in fo rc ed, prestr esse d, hig h strength, parkingstr uctu re s,indu s tr ia l slabs , w a te rt ig h tconcre te andligh tw e ig h tconcre te .A D V A N TA G E S

. EU C O N 537 pro duces concre te wit hcontr O lled d e la yofslumplos s an dw ork ab il i ty .2 E U C O N 537g rea tly re duceswate rrequire ments .3. EUCON 537re duces segrega tio n an d b leed in gin th e p las ti cconcre te .4. E U C Q N 537reduces crackingand perm eab il it yof hard ened concrete.5 EUCO N537, w hen used to produce flo w ingcon cre te , significantly re ducesconcre te p lacem ent timeandcostE N G IN E ER IN G DATAW ate r con ten t, max im um perc en t com pa re d tocon tro lRate ofs lu m pJoss 9 s lu m pconcrete, at72 FRateof slumploss, 9 slumpco ncre te , atgooF.C om pressiv eStreng th s vs control .1day3days7days28 daysRelativ eDurabi lit y - fre eze thawre s is ta nce

D IR EC TIO NS FO R USE

upto140%140-160% 130-150%125-135

70-8 01/2 to1 first hr.1 ' tol fi rsthr.

98.7%

Quantity- EU C O N 537is use data rangeof 6 to32ounces per 10 0 pounds cem ent. WhenEU C O N 537is added, at a rate of12ounces per100 pounds cem ent, to a1 to3 s lum pconcre te,it w il lproduce fl ow ab le w it haslu m p of 7 to10.

, O rC AH-2 16- 53 1- 922 2-'-110 '0-321-7628

CHEM ISTS TC THEBU IL C IN O INCUSTRY S INCE . 91 C

Figure8. Product sheetforaretarding-typehighrangewate rreducer.


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Admixtures Not Covered b Existing ASTM Specifications

The chemical admixture types discussed so far are all covered by ASTM specification. This by no means exhausts the list of chemical admixtures used in concrete orpromoted for such use. Some additional admixtures are in process of having specifications compiled and approved; others are used without such specification. The chemicaladmixtures field is in an active state of development and chemical admixtures toaddress new functions are being continuously developed and marketed. The admixturesdiscussed below probably comprise most but not necessarily all of the types availablefor general concrete use. Admixtures for specialized concretes such as shotcretespolymer-modified concretes or calcium aluminate cement concretes or for grouts arenot considered.Corrosion Inhibjtor Admixtures

The corrosion of reinforcing and prestressing steel in concrete due to chlorideions has been a major problem in the transportation and highway fields. Bridge decksand other concrete bridge elements and parking garages have been particularly af-fected.

For a number of years the main preventive measure specified has been the useof epoxy-coated steel. It now appears that this strategy at least as has been practicedunder current specifications is flawed. Accordingly new importance is expected to beplaced on the use of corrosion inhibitor admixtures in such concretes.

While a number of chemicals posses corrosion i n h i ~ i o n properties one admix-tures marketed commercially is based primarily on calcium n ~ r i t e This material whenadd::d at the noomal dosage rate functions also as a relatively strong accelerator. It alsonormally increases the uttimate strength of the concrete. When the accelerating effectis not desired for example in hot weather concreting a suitable retarder may be addedto overcome this effect. It is usually recommended that the two admixtures be addedseparately.

The effectiveness of calcium nnrite has been extensively documented in variousFHWA and other studies. One study has suggested the possibility of superior corrosionresistance might be obtained from a mixture of calcium nitrate and sodium molybdatebut such combined corrosion protection admixtures have not been extensively tested.


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Calcium nitrite is used at relatively high dosages, of the order of 2% by weight ofcement. The dosage level may have to be increased if very high contents of chlorideare expected. The increased costs involved are considerable, but where corrosion risksare high, the expected cost is usually considered to be modest in comparison with theexpected benefit, even if high dosages are required .

An illustrative product sheet describing a calcium nitrate based corrosionpreventing admixture is reproduced as Figure 9.More recently, a corrosion prevention admixture based on based on an entirely

different system has been introduced by another major manufacturer. This material is awater-based combination of organic amines to form a barrier film) and esters (to renderthe cement paste hydrophobic), and is said to prevent or delay corrosion by forming ahydrophobic barrier to chloride and moisture penetration into the concrete.ntifreeze dmixtures

Antifreeze admixtures are designed to prevent damage due to freezing in fneshconcrete, and to permit continued hydration at temperatunes less than 32 F. They havebeen little used in the Unijed States because of concems connected wtth their possibleinfluences on corrosion, on alkali silica reaction, and on air-entrainment. However, atleast one antifreeze admixture, said to be fnee of chlOride, has been marketed for several years by a major admixtune producer in the Unijed States. Its effects have been described in a recent paper, and are said t include acceleration of both setting andstrength gain, as well as antifneeze action.

Compounds that have been used for antifreeze purposes include ammonium hydroxide, various calcium and sodium satts (including nitrate, nitrite, and chloride),potassium carbonate, and unea. In a recent study reported by an agency of the U.S.Army Corps of Engineers, sodium and calcium nitrite mixtures and sodium nitritepotassium carbonate mixtures were found to be particularly effective. Both thesemixtures were additionally recorded as having significant accelerating effect, but bothincnease the alkali burden of the cement. A new antifreeze admixture free of bothchloride and alkalis has recently been marketed in Japan, which is said to containcalcium nitrite and nitrate and polyglycol ester derivatives, and thus be free of thisadditional alkali burden.

Use of antifreeze admixtures may turn out to be an appropriate and cost-effective way to protect transportation-related structures whene early freezing cannot be prevented.


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WaterproofingAdmixturesConcretewaterproofersareadmixturesadded in themixwaterthat aredesignedto increasethe solid-watercontact angle of the hardenedconcrete sufficientlyso thattheconcrete is renderedwater repellent or''waterproofed''. Thesematerialsaresome-times referred to as integral or internal waterproofers, todistinguishthem fromexternal coatingsdeSigned to do thesame job.Thewaterproofing action functionsonly fo rwater undermodest pressures, but renders concrete, once dry, much more difficult torewetand resaturate. This conferssomebenefit in freezingand thawingandsometimesin alkali-silica reactionand steel corrosion situations. Waterproofersare also used forarch itecturalconcrete,with benefitssuch as reduced possibilityofefflorescence andbettersurfaceappearancebeing claimed. Precastarchitecturalpanelsare acommonapplication.Three different classesofwaterproofing admixturesare generallyrecognized:liquidfatty acids (typicallymixturesofoleicandotherliquidfats); emulsionsofwaxesofvariouskinds,and finelydividedwaxysolidssuchascalcium or aluminumstearate.Waterproofing admixturesaremuchmorecommonlyused inEuropethanin theUnitedStates, anhough theyaremarketedbyseveral admixtureproducersin thiscountry. NoASTMstandardsexist.Nevertheless,thepossibilitiesfortheir useintransportationrelated structuresinvolvingvertical surfaceswhereappearance is importantshouldnot beoverlooked.

Stop-Start AdmixturesThese are novel and highlysophisticated chemical systems designedtopermitthesettingandhydrationof concrete to be stoppedonapplicationof oneagentandre-sumedat some laterperiod when the stopped concreteis remixedwtth thesecondagent. Usuallyaddttional fresh concretemust be blended wtth the stopped concretewhenhydrationistobe resumed.These systemswere developedmore asmanagement tools in concrete operationsthanasadmixtures designedtoaffect theunimatepropertiesofthehardenedcon

crete. In particular, theyhave beenmarketedasan environmental toolsto reduce oreliminatethevolumeofwasteconcrete andconcretewashingsthatresun fromordinaryconcreteoperations,especiallytransit-mixedoperations.Stop-start admixtures are marketed by several of the largest admixturemanufacturers.Thechemistryoftheeffectsproduced is notwidelyunderstood, andthe


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chemical systems themselves are not disclosed. There are no existing ASTM standardsfor this class of admixture.

lkali Silica Reactioo preventjng dmixturesThese fall into the category of potential rather than actual commercially

marketed admixtures although there are indications that one or more admixturecompanies might market such a product in the near future.

Hrwr + Fly Ash+Silica Fume

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