Sbf Bk a07025 Accelerating Admixtures for Concrete

8/18/2019 Sbf Bk a07025 Accelerating Admixtures for Concrete

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SINTEF REPORTTITLE

COIN P1 Advanced cementing materials

SINTEF Building and Infrastructure SP 1.2 F Controlling hydration development

COIN – Concrete Innovation Centre

Accelerating admixtures or concrete Address: NO-7465 TrondheimNORWA

State o the artLocation: Richard !ir"e#ands vei $Te#e%hone: &47 7$ 5' 5( (4

)a*: &47 7$ 5' 7+ $6

Enter%rise No,: NO '4 ..7 .(' /0A A1T2OR3

Roar Myrdal

CLIENT3

Aker Kværner Engineering and Technology, Borregaard LignoTech,maxitGroup, orcem A!", or#egian $u%lic Road& Admini&tration,Re&con Mapei A", "penncon A", 'nicon A", (eidekke A"A and

The Re&earch )ouncil o* or#ayREORT NO, CLAI)ICATION CLIENT RE),

"B+ BK A-./ 'nre&tricted Ter0e +! R1nningCLA44, T2I4 6A7E I!N RO8ECT NO, NO, O) AE9AENICE

'nre&tricted 2-343.4/56423243 576. 5/

ELECTRONIC )ILE COE RO8ECT /ANAER 3NA/E; IN, C2EC


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Fore!ord

)C@ 4 )oncrete @nnovation )entre 4 i& one o* pre&ently :D )entre& *or Re&earch %a&ed@nnovation )R@, #hich i& an initiative %y the Re&earch )ouncil o* or#ay! The main o%0ective*or the )R@& i& to enhance the capa%ility o* the %u&ine&& &ector to innovate %y *ocu&ing on long4term re&earch %a&ed on *orging clo&e alliance& %et#een re&earch4inten&ive enterpri&e& and

prominent re&earch group&!

The vi&ion o* )C@ i& creation o* more attractive concrete %uilding& and con&truction&!Attractivene&& implie& ae&thetic&, *unctionality, &u&taina%ility, energy e**iciency, indoor climate,indu&triali?ed con&truction, improved #ork environment, and co&t e**iciency during the #hole&ervice li*e! The primary goal i& to *ul*ill thi& vi&ion %y %ringing the development a ma0or leap

*or#ard %y more *undamental under&tanding o* the mechani&m& in order to develop advancedmaterial&, e**icient con&truction techni


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1 Introduction

The rate& o* chemical reaction& %et#een clinker material& in cement& and #ater, o*ten re*erred to

a& cement hydration reaction&, may %e altered %y adding &mall amount& o* chemical &u%&tance& tothe cement4 #ater mix! "u%&tance& a**ecting the&e rate& to give an overall increa&e in the hydrationrate, i!e! an accelerating e**ect, are termed accelerating admixture& or &imply accelerator&! 8ence,an accelerator i& added to concrete *or the purpo&e o* &hortening &etting time and;or increa&ingearly &trength development! @n the *ir&t ca&e the main action o* the accelerator occur& in the pla&tic&tate o* the cement pa&te, #hile in the latter ca&e the accelerator act& primarily in the hardened&tate! "ome accelerator& a**ect either &etting or hardening, #hile &everal accelerate %oth &ettingand hardening!

The aim o* thi& report i& to provide an overvie# o* chemical admixture& reported to accelerate&etting and;or hardening o* Crdinary $ortland )ement C$) and C$) %a&ed concrete! Both

accelerator& *or normal concrete and no??le added accelerator& *or &prayed concrete &hotcrete#ill %e di&cu&&ed! +ir&t, an outline o* accelerator& in general i& given including an overvie# o* accelerator con&umption in or#ay over the la&t year&, *ollo#ed %y a de&cription o* &peci*icaccelerator& and their mode o* action during cement hydration! Al&o commercial accelerator& aretreated!

A& almo&t : F o* concrete accelerator& on the market are in li


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"etting and hardening may al&o %e determined indirectly %y mea&uring the heat evolution or temperature increa&e generated *rom the chemical reaction& %et#een cement and #ater! Thehydration o* cement, %eing an exothermic reaction, produce& heat and i* the hydration i&

accelerated, heat i& either produced earlier &etting and;or at a *a&ter rate hardening! Thi& i&illu&trated in +igure .!:!

@t &hould, ho#ever, %e reali&ed that a lot o* accelerator& a**ect %oth &etting and hardening,&ometime& depending on the do&age o* the accelerator!

Qor

T

Time, t

+igure .!: The e**ect& o* &etting and hardening accelerator& upon the rate o* heatevolution H;kg or temperature T o) during hydration o* cement!Re*erence )ement pa&te #ithout accelerator!"etting )ement pa&te #ith &etting accelerator!8ardening )ement pa&te #ith hardening accelerator!The &etting accelerator produce& heat earlier than the re*erence, %ut the &lope& o* thecurve& are parallel e


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according to their phy&ical *orm and chemical nature, *or in&tance


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+igure .!D Ratio %et#een total application o* accelerator& *or normal concrete and the total u&e

o* $ortland cement& in or#ay in the period :22:I.6 7ata *rom ))A =4>,

Accelerator consumption – sprayed concrete

7ue to the large volume& o* &hotcrete production and the high do&age o* &hotcrete accelerator&typically more than / F %y cement #eight, &hotcrete accelerator& i& %y *ar the mo&t u&ed cla&& o* accelerator in term& o* volume! +or in&tance, the volume o* &hotcrete accelerator& &old in or#ayin .6 #a& approximately : time& that o* accelerator& u&ed *or normal concrete in the &ame

period &ee +igure& .!. and .!/! 'nlike the &ituation *or normal concrete, there i& no trend o* increa&e in &hotcrete accelerator con&umption per ton cement u&ed during the :22&! Cn the other hand, a very clear increa&e in accelerator con&umption relative to cement con&umption ha& %eeno%&erved &ince .5 &ee +igure .!6! @t &eem& to %e a con&en&u& among or#egian &hotcreteoperator& today, although not documented, that higher do&age& o* &hotcrete accelerator& areneeded to compen&ate *or &lo#er &trength development in the concrete no#aday& compared to thelate :22& or early .&! The rea&on *or thi& trend ha& not yet %een clari*ied, %ut may %e partlycau&ed %y the introduction o* alkali4*ree &hotcrete accelerator& the very &ame period &ee )hapter :5 and;or the increa&ing u&e o* %lended cement&!

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+igure .!/ Total or#egian application o* accelerator& *or &prayed concrete &hotcrete in

the period :22:I.6 7ata *rom ))A =4>!


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1• 8ydr oxide

2• )hlor ide,

%r omideand*luor

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8• $er chlor ate

9• "

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Aluminate


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Both type o* anion and type o* accompanying alkali or alkali earth cation play a role! A &creeningo* di**erent com%ination& o* &ome o* the anion& and cation& #ithin thi& group, %a&ed on high ande


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1• )a)l. accelerate& %oth &etting and hardening o* C$) =(>,

2• )a)l. i& the olde&t chemical admixture *or C$) %a&ed concrete reported a& early a& :336=>,

3• )a)l. i& the cheape&t and the mo&t e**ective accelerator to date =2>, 4• Although not *ully under&tood , the mode o* action o* )a)l. in concrete and it& e**ect on

the hydration kinetic& are #ell documented =(; 3>, 5• The e**ect o* )a)l. on other cement pa&te propertie& i& kno#n *or in&tance

*ree?e;tha# re&i&tance, &ulphate re&i&tance and poro&ity =(; :>!

6• )a)l. accelerate& %oth the reaction %et#een tricalcium aluminate )5A andgyp&um )a"CD .8.C and the hydration o* tricalcium &ilicate )5" =::>,

)a)l. doe& not accelerate the hydration o* high4alumina cement& =., :.>; %ut ha& %een reported toaccelerate the po??olanic reaction %et#een )aC8. and rice hu&k a&h =:5>! @t i& al&o reported that)a)l. activate& the hydration o* &lag =:D>! 8o#ever, a compari&on %et#een )a)l. and a."CD

&odium &ulphate a& activator& *or the po??olanic reaction o* *ly a&h, &ho#ed that a ."CDincrea&ed %oth early and later &trength&, #hile )a)l. mainly increa&ed later &trength& =+5>,

7e&pite the re&earch on )a)l.;cement pa&te interaction& *or &everal decade&, it ha& %een &tated that

the mechani&m& re&pon&i%le *or the accelerating e**ect o* )a)l. on the hydration o* )5" &till are

poorly under&tood =:6>! The ne# chloride4*ree accelerator&, replacing )a)l., are even le&&under&tood, and al&o le&& e**ective! The general &ituation today can %e &ummari&ed like thi& =:->

!hloride"based accelerators !hloride"free accelerators

"evere corro&ion ha?ard& o Aor lo# corro&ion ha?ard&

Lo# co&t;per*ormance ratio 8igh co&t;per*ormance ratio

The development o* chloride 4*ree accelerator& #ith lo# co&t;per*ormance ratio& ha& %een achallenge *or manu*acturer& o* admixture& *or many year&, and &till i&!

$ Calcium nitrate and other nitrate%nitrite salts

#itrates

According to the ranging o* accelerating anion& de&cri%ed a%ove, nitrate C5B i& le&& e**ective

than chloride &ee )hapter 5! The i&othermal conduction calorimeter curve& &ho#n in +igure /!:,comparing the e**ect& o* di**erent calcium &alt& on the rate o* hydration o* &ynthetic ) 5", clearly&ho# that calcium nitrate )aC5. i& le&& e**ective than )a)l. on %oth &etting and hardening=3>!

Ramachandran =+> *ound that )aC5. acted a& an accelerator o* &etting in cement pa&te at lo#concentration&, %ut &ho#ed no e**ect on early &trength development! According to El47idamony et

al =:2> )aC5. i& more e**ective than )a)l. a& accelerator *or the hydration o* %elite F4)."!Thi& ha& %een con*irmed %y 9u&tne& =(., .:> #ho ha& carried out a &erie& o* re&earch &tudie& on

technical grade calcium nitrate including a &mall amount o* ammonium, 8 DJ a& concrete

admixture &ince early :22&! 8i& *inding& regarding mode o* action in C$) pa&te are a& *ollo#&


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1• "et acceleration i& achieved %y lo# do&age&!2• Mu&t %e com%ined #ith other component& to *unction a& a hardening accelerator!

3• o correlation %et#een &et accelerating e**iciency and content o* )5A in the cement!

4• @nitial &etting time decrea&e& #ith increa&ing content o* %elite in the cement!5• @nitial &etting time decrea&e& #ith decrea&ing alkali content in the cement!6• The mechani&m *or accelerating &etting i& t#o4*old(1) An increa&ed calcium concentration lead& to a *a&ter &uper4&aturation o* the #ater #ith

re&pect to calcium hydroxide )aC8.!(2) A decrea&ed &ulphate concentration lead& to &lo#er;le&& *ormation o* ettringite #hich

#ill &horten the on&et o* )5A hydration!

+igure /!: @&othermal conduction calorimeter curve& *or )5" #ith variou& calcium &alt&! 7o&age i&. F anhydrou& &alt %y #eight o* )5 "! The num%er& indicate the &lope& o* thetemperature4time curve& *rom the end o* the dormant period to the peak temperaturerelative to that o* untreated )5", #hich a&&igned a value o* :! =3>!

Rixom =((> inve&tigated the relation&hip %et#een temperature and &etting and *ound that )a)l.can compen&ate *or approximately :/o) drop in temperature, #hile )aC5. can compen&ate *or

a :o) drop!

)alcium nitrate at relatively high do&age& ha& proven to %e an e**ective inhi%itor again&t chlorideinduced corro&ion o* &teel rein*orcement in concrete =.>! Accordingly, calcium nitrate i& amulti*unctional admixture *or concrete!

Today, mo&t &upplier& o* concrete admixture& o**er calcium nitrate %a&ed accelerator& &ee )hapter

:.!

The %ehaviour o* alkali nitrate& in concrete ha& al&o %een inve&tigated, %ut not a& thoroughly a&


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)aC5.! @t &eem& that &odium nitrate aC5 ha& hardly any accelerating e**ect on &etting


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%ehavior =., .5>, %ut i& u&ed to &ome extent in #inter concreting admixture&, &o4called anti*ree?eadmixture& &ee )hapter& : and :.!

#itrites

itrite C.B di**er& chemically *rom nitrate C5

B only in the oxidation &tate o* nitrogen itrite ox! &tate J/ ver&u& nitrate ox! &tate J-!

)alcium nitrite )aC.. ha& pro%a%ly %een the mo&t popular non4chloride &etting accelerator inthe '"A &ince late :26& =>, Many commercial accelerator& today, and particularly anti*ree?eadmixture& &ee )hapter& : and :., contain calcium and;or &odium &alt& o* nitrite! Even &trengthdevelopment e**ect& produced in concrete are reported to %e almo&t compara%le to tho&e o%tained

#ith )a)l. =2>! 7e&pite thi& #ide&pread u&e, report& de&cri%ing the mode o* action andmechani&m& involved in cement pa&te &etting are lacking!

)aC.. ha& al&o proved to %e an e**ective anodic corro&ion inhi%itor *or metal& em%edded inconcrete =.D>! Thi& i& pro%a%ly the main re&earch area today regarding u&e o* )aC .. inconcrete!

itrite& &u**er *rom one %ig commercial di&advantage compared to nitrate&! Even though calciumnitrite &eem& to %e Nthe %e&t non4chloride admixture to dateN O2P, nitrite& are toxic andenvironmentally un*riendly! Thi& mean& that nitrite&, at lea&t *or *uture application&, #ill %edi&couraged due to health and environmental re


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1• )alcium thiocyanate )a"). i& the mo&t e**ective thiocyanate *or promoting &trength

development! @n accordance #ith the ranging o* ionic com%ination& in )hapter 5

2• The addition o* 5 F )a"). %y cement #eight to a pa&te hydrated at I /o) re&ulted

in .34day& compre&&ive &trength that #a& -D F o* the &trength o* the pa&te cured at roomtemperature!3• The lea&t e**ective &alt on compre&&ive &trength development #a& pota&&ium thiocyanate

K")! The pa&te #ith K"), although producing the highe&t heat development a*ter 5 day& at room temperature, had &trength value& a& lo# a& .;5 o* the re*erence value!

4• Ammonium thiocyanate 8D") relea&e& o**en&ive ammonia vapour and there*ore i&not a via%le chemical *or practical application&!

A po&&i%le &olution to thi& la&t point could %e to try out amine& #ith le&& o**en&ive vapour& thanammonium *or in&tance, alkanolamine& like di4 or triethanolamine& #hich are al&o accelerator&*or cement hydration &ee )hapter 2!

'n*ortunately, Hi&e et al O./P u&ed very high do&age& in their &tudy I %et#een :!/ and 5 F %y#eight o* cement! Thi& i& pro%a%ly *ar too high *or many practical application& high co&t and highamount o* alkali& i* alkali thiocyanate& are u&ed! +urthermore, practical experience& recommend amaximum do&age %elo# : F %y cement #eight! Cne &upplier o* a a") %a&ed accelerator &tate&that a do&age higher than !3 F o* a D F &olution i!e! !5. F active material doe& not give*urther increa&e in acceleration, %ut can in certain ca&e& have a retarding e**ect O.3P!

A%delra?ig et al O.2P e&timated the degree o* hydration o* C$) pa&te& %y di**erential &canningcalorimetry and *ound that addition o* a") produced more calcium hydroxide than an e


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"ch#ar? O5.P *ound that high do&age& o* K .)C5 in com%ination #ith high do&age& o* pota&&iumcitrate are highly e**icient accelerator& *or aluminate and *errite hydration in C$)&! @t i& a&&umedthat citrate promote& the di&&olution o* the *errite pha&e& %y acting via &ur*ace complexation and

ligand4promoted di&&olution =5.>! )itric acid and it& &alt& are normally u&ed a& retarder& *or cementhydration, %ut may act a& accelerator& a high do&age& =55>!

& Car'oxylic acids and their salts

Accelerating propertie& are *ound among &everal type& o* car%oxylic acid& and their &alt&

1• monocarboxylic

2• dicarboxylic

3• hydroxycarboxylic

$opovic& =.> claim& that #ater &olu%le organic material& %elonging to the car%oxylic acid groupare &ome o* the mo&t e**ective chloride4*ree accelerator& *or cement hydration! Hithout %eing&peci*ic regarding type o* acid, he &tate& that one acid #ith a &hort hydrocar%on chain i& e**ectivedue to it& a%ility to promote the di&&olution o* calcium ion& *rom the cement compound& =.>!

&onocarboxylic 'formates and acetates(

Accelerating propertie& have %een reported *or the lo#er monocar%oxylic acid& ): to )D andtheir &alt& *ormic, acetic, propionic and %utyric, #hile higher car%oxylic acid homologe& Q)Dare retarder& O/P! @t &eem& that tho&e %elonging to ): are the mo&t e**icient one&, and that the

calcium &alt o* *ormic acid, calcium *ormate )a8)CC., are the mo&t common! 7od&on O3P %egan re&earch on )a8)CC. in early :26& and *ound that although )a8)CC. #a& not a&e**ective a& )a)l., it doe& produce &ati&*actory increa&e& in early &trength a& #ell a& that o* later age&! According to 7od&on =3> )a8)CC. al&o accelerate& &etting o* C$)! 8eikal = 5D> *oundthat the initial and *inal &etting time& o* %oth C$) and po??olanic cement pa&te& are &hortened#ith the addition o* )a8)CC.!

8e#lett =5/> ha& compared the calcium &alt& o* chloride, nitrite and *ormate, and related their accelerating e**iciencie& to the mo%ility o* the anion& in order to penetrate into the &ilicate

particle&! )on&e! 8eikal =5D> claim& that the accelerating e**ect o*

)a8)CC. on calcium &ilicate hydrate *ormation i& mainly attri%uted to the *act that the di**u&ionrate o* 8)CCB ion& i& much higher than *or the )a.J ion&, and that the 8)CCB ion& can penetrateinto the hydrated layer& covering )5" and F4)." grain&! A& a con&e!

9u&tne& =(.> *ound that )a8)CC. and calcium acetate )a)85)CC. #a& le&& e**ectiveaccelerator& than )aC5. at e report& that )a8)CC. accelerate& the hydration o* )5", and one explanation

i& that 8)CCB ion& inter*ere #ith the protective layer normally *ormed on the &ur*ace o* thecement particle&! +urthermore, the e**ect o* )a8)CC. a& an accelerator i& in*luenced %y


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the )5A;"C5 ratio in the cement! According to Ge%ler =5-> cement& that are Nunder&ul*ated

)5A;"C5DD! provide the %e&t potential *or )a8)CC. to accelerate the early age &trength o* concrete!

Rixom =2> claim& that )a8)CC. accelerate& the &etting and hydration o* all type& o* cement, %utat do&age& %eyond . F %y cement #eight I e&pecially #ith re&pect to the *ir&t .D hour& I thee**ect i& not &igni*icant!

The %igge&t pro%lem in u&ing )a8)CC. a& an accelerating admixture *or concrete i& it& lo#

&olu%ility in #ater approx! :6g;:g 8.C at room temperature! There*ore, it i& not commerciallyavaila%le in li! Thi& can createdi&pen&ing pro%lem&! "odium *ormate a8)CC, #hich ha& al&o accelerating propertie&, i&approximately 5 time& more &olu%le in #ater, %ut the potential pro%lem o* the added alkali atrelatively high do&age& di&courage& it& u&e =3>!

)icarboxylic 'oxalic acid(

7icar%oxylic acid& are acid& in #hich there are t#o car%oxyl group&! The &imple&t o* the&e acid&,ethanedioic acid @'$A) name or oxalic acid trivial name, con&i&t& &imply o* t#o car%oxylgroup& B)CC8 linked together! Although chemically related, the propertie& o* oxalic acid arevery di**erent than *or ethanoic acid acetic acid

COO2 C2$

COO2 COO2

*xalic acid 'ethanedioic( Acetic acid 'ethanoic(

p+a-./ p+a-0./1

+rom the pKa value& it i& &een that oxalic acid i& a much &tronger acid than acetic acid! Theinductive e**ect o* one car%oxyl group in oxalic acid i& expected to enhance the acidity o* theother =$>,

Cxalic acid i& reported to decrea&e the &etting time o* C$) and increa&e early compre&&ive&trength =$6>, Taylor O52P *ound that calcium oxalate i& precipitated #hen oxalic acid i& added to

)5", and the concentration o* )a.J ion& clo&e to the &ur*ace o* the )5" i& there%y kept lo# until all

the oxalic acid ha& %een u&ed up!

Ramachandran O:3P compared hydrated cement #ith and #ithout oxalic acid u&ing the 7TAtechni


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ionic %ond& #ith *ree lime and calcite& o* cement and *orm calcium oxalate OD:P! Hhen pre&ent in&mall amount& in cement it &eem& that the retarding e**ect o* oxalic acid i& &imilar to that *ound *or acetic acid at lo# do&age& =D:>!

%ydroxycarboxylic 'glycolic and lactic acids(

Although mo&t hydroxycar%oxylic acid& and their &alt& retard the &etting o* C$) =5/>, there areexample& o* hydroxycar%oxylic acid& #ith accelerating propertie& in cement! Thi& in*ormation i&typically di&clo&ed in the patent literature =4(; 4$>, G& early a& :26D Sach et al =D.> *ound that thet#o *ir&t mem%er& o* the &erie& o* H4hydroxycar%oxylic acid& #ith a hydroxyl group ad0acent tothe car%oxyl group I &ee Ta%le 3!: %elo# cau&ed a &igni*icant increa&e in the late .3 day&compre&&ive &trength o* concrete #hen admixed at lo# do&age&, typically *rom !: F to !: F

%y cement #eight! either the mechani&m o* action in cement pa&te, nor the e**ect on early&trength #a& di&cu&&ed %y Sach et al =D.>!

Ta%le 3!:)haracteri&tic& o* t#o H4car%oxylic acid& =DD> reported to accelerate cement hydration

Trivial name Cther name @'$A) name )hemical *ormula pK a

Glycolic acid 8ydroxyacetic acid .4hydroxyathanoic acid )8.C8)CC8 5!35

Lactic acid Milk acid .4hydroxypropanoic acid )85)8C8)CC8 5!3/

"chut? =D5> *ound that high do&age& o* &odium glycolate and &odium lactate &odium &alt& o* glycolic and lactic acid re&pectively &hortened &etting time and &peeded early &trengthdevelopment! Mechani&m& cau&ing the accelerating a%ility o* H4hydroxycar%oxylic acid& are

pro%a%ly unkno#n, %ut may %e linked to the a%ility o* the&e acid& to complex metal&! +or in&tance,glycolic acid i& u&ed a& a component o* hou&ehold cleaner& due to it& di&&olution capa%ilitie& *or hard4#ater &cale calcium and magne&ium =45>,

( Al)anolamines

Alkanolamine& are amine& containing either one primary amine R8., t#o &econdary amine

R .8 or three tertiary amine R 5 hydroxy alkyl group& R ! "ho#ing accelerating e**ect onC$) hydration, the&e organic chemical& are &ometime& u&ed a& ingredient& in admixture %lend&!They are all #eak %a&e&!

2riethanolamine '23A(

TEA, )8.)8.C85 , i& %oth a tertiary amine and a tri4alcohol, and i& pro%a%ly the mo&tcommon alkanolamine *or concrete purpo&e&! TEA #a& introduced a& early a& :25D, #hen it #a&interground a& an addition #ith C$) in com%ination #ith calcium ligno&ulphonate =>, Thi& #a&

done to increa&e the early compre&&ive &trength o* the concrete made *rom the cement! "ince :2/3TEA ha& %ecome a common ingredient o* &ome #ater reducing admixture& to o**4&et po&&i%le &etretardation cau&ed %y the #ater reducer =3>! Cne o* the mo&t characteri&tic *eature& o* TEA i& it&a%ility to either accelerate or retard cement hydration depending on do&age! TEA tend& to


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:3

accelerate )5A hydration kinetic&, %ut act a& a retarder on the hydration o* )5" O5:, 5/P! Rixom

=D6> ha& &ummari&ed &ome o* the *eature& o* TEA in C$)

1• @n the pre&ence o* TEA the reaction %et#een )5A and gyp&um i& accelerated!

2• The &u%&e claimed that Nthe mo&t popular addition rate o* TEA i& in the range o* !: F to!./ F on the #eight o* cement! +igure 2!: &ho#& the e**ect o* do&age!

+igure 2!: The e**ect o* do&age o* TEA on &etting and hardening o* C$) concrete& =3>! Thecurve& &ho# the re&i&tance to penetration a& a *unction o* time *or *our di**erent


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do&age& o* TEA and a re*erence #ithout TEA!


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:2

The data in +igure 2!: indicate that at a do&age o* !. F, TEA act& a& an accelerator, at !./ F a&a retarder, at !/ F a& a &evere retarder and at :! F a& a *la&h4&et accelerator! "imilar %ehaviour #a& *ound %y Ramachandran =5:> #hen mea&uring the initial and *inal &etting characteri&tic& o*

C$) mortar treated #ith I !/ F TEA &ee +igure 2!.!

4 e t t i n ?

t i m e 3 m i n @ t e s 5

+....

)ina#

+

.

.

.


33/53

+..

+. Initia#

+

.;.+ .;+ +

:osa?e 3 JK ei?ht o cement

+igure 2!. E**ect o* do&age o* TEA oninitial and *inal &etting o* C$) mortar7ata *rom =$+>,

Although it ha& %een &ho#n that TEAdecrea&e& the &trength o* C$), it act&di**erently #ith %la&t *urnace cement&!@t ha& %een *ound that TEA in a mortar containing 5 F C$) and - F &lagaccelerated the hydration kinetic& %yincrea&ing the rate o* reaction o* gyp&um #ith &lag in the pre&ence o* lime =$+>,

8eren OD-P #a& the *ir&t to pu%li&h datain :22/ on the e**ect o* monoethanolamine MEA,

8.)8.)8.C8, and diethanolamine7EA, 8)8.)8.C8., on cementhydration! 8e compared MEA, 7EAand TEA at do&age& !: to :! F in

#hite $or t

land cement

and

*ound no&igni*icant e**ecton the initial&etting time& atlo# do&age&, %ut&igni*icantretardation athigher do&age&*or all threetype&! Be&ide&,

%oth MEA andTEA lo#ered thecompre&&ive&trength a*ter 5day&, #hilecement pa&te&containing 7EA#ere clo&e to thato* the control&ample =D->!'n*ortunately,8eren did not

pu%li&h re&ult&on lo#er do&age&potentialdo&age& *or

accelerating e**ect&! 8o#ever, hi&re&ult& indicate that 7EA, at proper do&age&, could %e an intere&ting

potential accelerator, and even %etter than TEA! @n that re&pect it i&intere&ting to note that &everal alkali4*ree &hotcrete accelerator& contain7EA &ee )hapter& :: and :5! Another related amine, methyldiethanolamine

M7EA, )85)8.)8.C8., i&

u&ed in commercial accelerator& *or normal concrete &ee )hapter :.!

2riisopropanolamine '2I4A(

@n :22: T@$A #a& &ugge&ted a& a&trength enhancer *or C$) =.->! Later,in :22-, @chika#a =D3P &tudied thee**ect o* !: F T@$A %y #eight o* cement in cement& #ith di**erentcompo&ition& o* clinker mineral&, andhe *ound that the &trength enhancemento* cement mortar %y T@$A depend& onthe


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.

*rom the clinker #ith only : F )DA+! "and%erg =D2> carried out &imilar te&t& on : di**erent C$)&

I all containing Nnormal di&tri%ution& o* clinker mineral& I and *ound approximately : Fincrea&e in .3 day& &trength *or all &ample& containing !. F T@$A %y #eight o* cement!

Aggoun =/P te&ted the e**ect o* the admixture com%ination& T@$A ; TEA ; calcium nitrate on&etting time and early &trength in C$), and *ound that the com%ination amine ; calcium nitrate

produced &igni*icant and promi&ing re&ult& #ith re&pect to %oth &etting and hardening acceleration!Moreover, regardle&& o* the cement type u&ed, Aggoun =/> *ound that the per*ormance o* T@$A a&a hardening accelerator i& greater than that o* TEA!

T@$A ha& al&o %een evaluated a& a po&&i%le grinding aid component *or cement production a

common role o* TEA today =/:>!

1# Antireee admixtures

Hinter concreting practice ha& remained almo&t unchanged &ince the :25& O/.P! The concreteingredient& mu&t %e heated, the &u%&trate mu&t %e tha#ed, and the concrete it&el* ha& to %ethermally protected until it ha& cured! An alternative approach to cold #eather concreting i& to u&eanti*ree?e admixture&! Thi& i& not yet *ully recogni?ed %y &tandard practice, except in Ru&&ia#here the u&e o* anti*ree?e admixture& o*ten containing chloride &alt& ha& %een accepta%le

practice *or nearly *ive decade& O/5, /DP! @n the la&t t#o decade& anti*ree?e admixture& #ithoutchloride& have %een te&ted in orth America, "candinavia, +inland, )hina and 9apan O-, :-, /D>!

Anti*ree?e admixture& are &ometime& con&idered a &pecial cla&& %elonging to the general categoryo* accelerating admixture&! Cne o* their mode o* action& i& to a**ect the phy&ical condition o* themixing #ater, i!e! %eing capa%le o* depre&&ing the *ree?ing point o* #ater in the *re&h concrete, %utthe main action i& to accelerate the hydration o* cement like conventional accelerator& =//>! The

principal o%0ective o* u&ing &uch admixture& i& t#o*old =3>

(1) To give the C$) in the concrete an opportunity to hydrate to a point that i* the remaining #ater

in the pore& *ree?e&, it ha& &u**icient volume o* empty pore& into #hich it can expand!

(2) To give the concrete &u**icient &trength to re&i&t damage %y the expan&ion o* the *ree?ing

#ater!

@t &hould %e noticed that, in order to o%tain a &igni*icant lo#ering o* the *ree?ing point, one ha& todi&&olve a con&idera%le calculated that an addition o* . F anhydrou& )a)l. %y the #eight o* cement to a typical concrete mix de&ign #ould lo#er the*ree?ing point o* the remaining #ater I a&&uming that 5 F o* the originally added #ater #a&con&umed during the early hydration I %y le&& than :o)! )on&e


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o* the #ater and the molality M o* the chemical &olved in the #ater


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.:

+$o) B:!-6M I :!.3 :!:

Thi& relation i& independent o* type o* chemical u&ed, provided the chemical remain& &olu%le at

lo# temperature&! Molality i& de*ined a& num%er o* mole& o* particle& ion&, molecule& di&&olvedinto : kg o* #ater! E


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..

11 Shotcrete accelerators

@n modern &hotcreting a li,

Among the conventional accelerator&, only #ater gla&& i& u&ed in today=& or#egian &hotcreting!@n modern &hotcrete technology, particularly in orthern part& o* Europe, alkali aluminate&,car%onate& and hydroxide& are con&idered pro%lematic due to

1• 8ighly cau&tic material& that re

1• )ompati%le #ith all type& o* cement2• Le&& cau&tic than aluminate& p8 lo#er than that o* *re&h concrete3• Lo# early &trength&4• 7ecrea&e in the E4modulu& #ith time5• Reduced *inal &trength at high do&age&6• 7ecrea&e in the #ater proo*ing characteri&tic& due to the extraction o* lime #hen the

concrete i& &u%0ected to a continuou& expo&ure to moi&ture7• 8igh vi&co&ity at lo# temperature #hich re


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&hotcrete operation&


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.5

+or the&e rea&on& the u&e o* #ater gla&& a& &hotcrete accelerator ha& %een re&tricted in Germany

and Au&tria =6>!

Al6ali"free shotcrete accelerators 'wea6ly acidic solutions of aluminum salts( =6:, 6. >Alkali4*ree accelerator& #ere originally developed to &olve &ome o* the pro%lem& cau&ed %y thealkaline accelerator&! 8o#ever, it &eem& that the large market &hare o* alkali4*ree accelerator& in"candinavia today i& mainly cau&ed %y the capa%ility o* the&e accelerator& to give very high early&trength&, rather than their lack o* Nalkali pro%lem&!

The chemical compo&ition& o* alkali4*ree accelerator& are clo&ely guarded trade &ecret& andthere*ore little pu%li&hed in*ormation i& availa%le! ormally, the main ingredient i& aluminum&ulphate =6:, 6.>! Admixture& containing large amount& o* aluminum &alt& and complexe& are

#eakly acidic p8.45 due to the hydroly&i& cau&ed %y aluminum ion&, Al 5J, given %y the

e

Al5J J 8.C AlC8.J J 8J ::!:

Aluminum &ulphate, Al."C55 n8. C n:/4:3, i& a lo# co&t %ulk chemical #ith high&olu%ility! At high do&age& aluminum &ulphate cau&e& *la&h &etting o* C$) O5/P! Brge O6.Pinve&tigated the mechani&m o* action o* aluminum &ulphate in cement and *ound that aluminum&ulphate react& #ith lime and produce& ettringite and aluminum hydroxide according to

Al."C55 J 6 )aC8. J 5. 8.C 5)aC Al.C5 5)a"CD 5.8.C J AlC85 ::!.

Ettringite i& re&pon&i%le *or the rapid &etting =6., 65>! A& a %y4product o* the reaction, AlC85 i&*ormed #hich i& al&o kno#n to %e an accelerator O6.P!

Malte&e =6D, 6/> inve&tigated to #hat extent type o* calcium &ulphate &etting regulator in C$)gyp&um, H4hemihydrate, F4hemihydrate or anhydrite a**ected the &etting %ehavior o* &hotcreteaccelerated %y an inorganic acid %a&ed alkali4*ree accelerator containing aluminum &ulphate! 8e*ound that the lo#er the in&tantaneou& di&&olution rate o* the calcium &ulphate, the more e**icientthe accelerator &ee Ta%le ::!:!

Ta%le ::!:Alkali4*ree accelerator and type o* &etting regulator in C$) data *rom =6D>

Type o* &etting 7i&&olution rate o* +inal &etting time o* C$) pa&te&etting regulator

regulator in C$) Hithout accelerator Hith accelerator A)a

.J

ion&, g;l min

F4hemihydrate 2. / h 5 min 3 h 5 min

H4hemihydrate 6 / h 6 min 5 &

Gyp&um D3 / h 5 min 5 min / &

Anhydrite - / h 5 min : min :3 &


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.D

+erric &ulphate, TEA and &odium *luoride are al&o reported a& ingredient& in &hotcrete accelerator&[35]. According to patent literature alkali4*ree &hotcrete accelerator& may contain ingredient& like

1• Amine and glycolic acid =66> 2• 8ydro*luoric acid, diethanolamine, methyldiethanolamine and ethylenediaminetetraacetic acid complex %inder =6->

3• Magne&ium &ulphate, pho&phorou& acid, oxalic acid, maleic anhydride and diethanolamine=63>

4• )itric and malic acid& and their alkali metal &alt& =62>, 3Malic acid &hould not %e con*u&ed#ith maleic or malonic acid, %oth o* #hich are di**erent type& o* dicar%oxylic acid&!

5• AlC8xR y, #here xJy5, Rorganic acid *ormic, acetic, D4toluene&ulphonic, lacticor oxalic or nitric acid =->

"ome in*ormation on ingredient& in commercial &hotcrete accelerator& i& di&clo&ed in their "a*ety

Material& 7ata "heet& provided %y the producer& &ee )hapter :5!

@n order to gain very high early &trength& in &hotcrete Myrdal O-:> tried to com%ine a no??le addedalkali4*ree accelerator #ith a Ndormant accelerator that #a& added in the concrete during mixing!The idea #a& that the Ndormant &hould not react #ith the cement until activated or Nignited %ythe alkali4*ree accelerator! A dou%ling o* early compre&&ive &trength& #a& o%tained u&ing a

proprietary Ndormant %lend o* #ater &olu%le car%onate, alkanolamine, hydroxycar%oxylate and pho&phonate O-:P!

@t i& generally %elieved that the high content o* aluminum &ulphate in alkali4*ree accelerator& may promote an internal *orm o* &ulphate attack in the concrete, %ut &o *ar no conclu&ive re&ult& have %een *ound concerning the dura%ility o* *ield &hotcrete =-., -5>!


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./

12 Commercial accelerators or normal concrete

"upplier& o* accelerator& &eldom di&clo&e the ingredient& o* their accelerator&, neither in their open

technical document& nor in their re&pon&e& to direct in


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.6

Ta%le :.!:A &electiono*

commercialli


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.-

Ta%le :5!:A &election o* commercial li


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334 o o in*ormation given in the M"7"


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.3

1" Accelerators or calcium aluminate cements

Many inorganic &alt& a**ect the &etting o* calcium aluminate cement& )A)&, and are e**ective in

concentration& o* !: to !/ F %y #eight o* cement O26, 2-P! The e**ect on &etting time& di**er greatly %oth in direction and in relative magnitude& *rom tho&e o%&erved #ith $ortland cement&!The &etting time& o* )A) cau&ed %y variou& admixed ion& are reported to increa&e in the*ollo#ing order O26P

)ation& LiJ U aJ V control #ithout accel! V K J )a.J V Mg.J V "r .J V 8DJ

Anion& C8B U control #ithout accel! V )lB V C5B V Br B V )85)CC

B acetate

Thi& mean& that LiC8 i& an e**ective accelerator, #hile )aC 5 . tend to retard &etting o* )A)!

Generally, lithium &alt& like Li.)C5, LiC8, Li)l and LiC5 are mo&t e**icient and #idely u&ed

accelerator& *or )A) O26, 23, 22P!

The accelerating e**ect o* lithium &alt& ha& %een explained %y the precipitation o* lithiumaluminate hydrate #hich act& a& a heterogeneou& nucleation &u%&trate O26P!

Alkali4earth metal &alt& o* chloride, nitrate and *ormate may act a& #eak accelerator& or retarder&depending on concentration and temperature O26, :P!

@t &eem& that the chemical mechani&m& o* action o* the&e admixture& are not #ell under&tood!

1$ ,ecommendations or uture ,-

+uture RW7 &hould aim at developing more e**icient non4chloride accelerator& *or concrete, and iti& con&idered important to *ocu& the e**ort& on

1• )hemical& that &peed up early hardening o* C$) %lended #ith po??olanic material&2• Technical grade %ulk chemical&3• "a*ety chemical& *riendly to human& and natural environment4• Lo# alkali content

5• "ynergi&tic e**ect& o* chemical %lend&

Acceleration of early hardening

There i& a #ell pronounced pro%lem that today=& non4chloride hardening accelerator& do not per*orm #ell enough, e&pecially in N&lo# hardening %lended cement&! There i& a lack o* accelerator& that e**iciently &peed up the &trength development during the *ir&t .D hour&! @t &eem&that re&earch on &etting accelerator& i& not that important! Today=& mo&t common &ettingaccelerator %a&ed on technical grade )aC5. *ul*il& the re


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.2

afety

The development o* *uture admixture& mu&t take %oth human and environmental &a*ety intocon&ideration! Thi& mean& that cau&tic, a& #ell a& highly acidic, admixture& are out, e!g! &hotcrete

accelerator& %a&ed on alkali aluminate& and acidic alkali4*ree accelerator& #ith very lo# p8 &hould %e avoided! +or normal concrete, %oth nitrite and thiocyanate %a&ed accelerator& on the markettoday are or &hould %e la%elled $n, %armful ! The N#or&t la%elling o* a potential admixture *or the *uture #ould pro%a%ly %e $i, Irritant ! Cther la%el& de&cri%ing ri&k to human& and nature &hould

%e avoided

Yi Yn T )

@rritant 8arm*ul Toxic )orro&ive 7angerou& *or environment

Acceptable − −− 9nacceptable −−−−−−−−−−−−−−−−−−−−−−−−−−−−

:ow al6ali content

The term Nalkali4*ree i& already #ell e&ta%li&hed *or &hotcrete accelerator&! @t #ould %e extremelydi**icult to enter the European market today #ith a ne# non4aluminate, non4&ilicate or non4car%onate &hotcrete accelerator containing alkali metal& a%ove : F a.C4e!

4otential accelerating chemicals and their combinations

Although a harm*ul material la%elled $n, thiocyanate &hould not %e a%andoned completely!Thiocyanate i& a #ell e&ta%li&hed accelerator in Europe, and &hould %e inve&tigated *urther, %ut a&minor component in *ormulation& together #ith nitrate, alkanolamine& and;or hydroxycar%oxylicacid& and their &alt&! Alkali metal thiocyanate, like today=& &odium thiocyanate, &hould %e avoided!

@n&tead, &olu%le alkali4*ree thiocyanate& can %e made %y neutrali?ing thiocyanic acid #ith a non4alkaline %a&e, *or in&tance )aC8. or alkanolamine

8)8.)8.C8. J 8") K = 8.)8.)8.C8.>J")B :/!:

)iethanolamine 2hiocyanic acid

@n thi& #ay an alkali4*ree accelerator can %e *ormulated u&ing ingredient& that &eparately &ho#accelerating e**ect& a& #ell! $o&&i%le &ynergi&tic e**ect& o* &uch com%ination& have not %een

pu%li&hed earlier!

"imilar approach can %e utili?ed *or developing &olu%le non4alkali &alt& o* car%oxylic acid&, e!g!

*ormic and oxalic acid&! The e**ect o* non4calcium *ormate on the hydration o* C$) #ith di**erent)5A;"C5 ratio& &hould %e compared to the )5A;"C5 &en&itivity reported *or calcium *ormate &ee


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)hapter 3!


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5

A parallel RW7 activity &hould %e a &creening o* alkanolamine&! +rom literature it &eem& that7EA and T@$A are the mo&t promi&ing, #hile other amine& can %e *ound in M"7"& o* commercialaccelerator& &ee Ta%le :.!:!

A &y&tematic inve&tigation o* the e**ect& o* car%oxylic acid& and their &alt& on C$) hydration i&

highly appreciated, e&pecially the propertie& o* H4hydroxycar%oxylic acid& and their &alt&!

+urther development o* anti*ree?e admixture& &hould *ocu& on com%ination& o* chemical& alreadyte&ted and reported! An ideal anti*ree?e admixture #ould con&i&t o* a temperature depressant ma0or part and a non"chloride accelerator minor part! @t i& important to *ind temperaturedepre&&ant& #ith lo# alkali metal content! Technical grade calcium nitrate i& a promi&ingtemperature depre&&ant! At high do&age&, ho#ever, &hort &etting time& may re


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5:

The mechani&m& o* action o* the ne# non4chloride accelerator& are not *ully under&tood! The&ynergi&tic e**ect o* com%ination& o* chemical& on hydration rate& i& a relatively ne# re&earch*ield, and *e# re&ult& have %een pu%li&hed in open report&! There i& a trend that di**erent

car%oxylic acid& and their &alt& are u&ed in commercial accelerator&! ear *uture re&earch #ill pro%a%ly *ocu& on &ynergi&tic e**ect& o* chemical& already te&ted a& &ole admixture&!

1* ,eerences

1 E 25D4..:, Admixtures for concrete, mortar and grout " 4art ; !oncrete admixtures – )efinitions, requirements, conformity, mar6ing and labelling , Bru&&el&, Belgium, .:!

2 $opovic& ", !oncrete &aterials – 4roperties, pecifications and 2esting , .nd edition,

)hapter 6, Hilliam Andre# $u%li&hing, oye&, :22., pp .564.D6!3 European +ederation o* )oncrete Admixture A&&ociation&, E+)A Environmental7eclaration, E+)A doc!5 ETG, 9anuary .6, http;;###!e*ca!in*o;pu%lication&!html

4 "tati&tical data provided %y the or#egian )ommittee *or )oncrete Admixture& ))A,.-!

5 The American )oncrete @n&titute, )ommittee Report A)@ .:.!5R4D, !hemical Admixtures for !oncrete, .D!

6 Taylor 8 + H, !ement !hemistry, )hapter ::, Academic $re&& Limited, London, :22, pp5/345/2!

7 Rixom R and Mailvaganam , !hemical Admixtures for !oncrete, )hapter 6, EW+ "pon,London, :222, pp .34.::!

8 7od&on (, !oncrete Admixtures, )hapter D, (an o&trand Reinhold, e# Zork, :22, pp-54:.!9 "ee re*! -, )hapter -, pp 5:.45:5!10 "ee re*! -, )hapter /, pp :3.4:3-!

11 Tenouta&&e , 2he %ydration &echanism of !


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5.

20 9u&tne& 8, +alci>ev nitrat 6ot mnogo"fun6cianalni dodate6 betonu '?!alcium #itrate as &ultifunctional !oncrete Admixture@ in lovenian(, :Dth "lovenian collo


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55

43 "chut? R 9 "ika )hemical )orporation, Admixtures and &ethod for Accelerating theetting of 4ortland !ement !ompositons, 'nited "tate& $atent o D,.6D,56-, April .3,:23:!

44 Hikipedia, http;;en!#ikipedia!org;#iki;Glycolic\acid andhttp;;en!#ikipedia!org;#iki;Lactic\acid45 7u$ont, Clycolic Acid. 4roperties, 9ses, torage and %andling , 7u$ont "peciality

)hemical&, '"A, :223!46 "ee re*! -, )hapter /, pp :664:--!47 8eren S and ^lme? 8, 2he Influence of 3thanolamines on the %ydration and &echanical

trength 4roperties of 4ortland !ement , )ement and )oncrete Re&earch, .6, :226, pp -:4-/!

48 @chika#a M et al, 3ffect of 2riisopropanolamine on %ydration and trength )evelopment of !ements with )ifferent !haracter , $roceeding& :th @nternational )ongre&& on the )hemi&try o* )ement, Gothen%urg Edited %y 8 9u&tne&, "#eden, 9une .46, :22-, paper no!

5iii/, 3 pp!49 "and%erg $ 9 and 7onca&ter +, *n the &echanism of trength 3nhancement of !ement 4aste and &ortar with 2riisopropanolamine, )ement and )oncrete Re&earch, 5D, .D, pp2-542-6!

50 Aggoun " et al, 3ffect of some admixtures on the setting time and strength evolution of cement pastes at early ages, )on&truction and Building Material&, .., .3, pp :64::!

51 9eknavorian A A et al, )etermination of Crinding Aids in 4ortland !ement by 4yrolysis Cas !hromatography"&ass pectrometry, )ement and )oncrete Re&earch, .3, :223, pp :55/4:5D/!

52 Korhonen ) 9, *ff"the"helf Antifreeze Admixtures, Technical Report ER7);)RREL TR4.4-, '" Army )orp& o* Engineer&, Engineer Re&earch and development )enter, ational

Technical @n*ormation "ervice, '"A, April .., 53 pp!53 +arrington " A and )hri&ten&en B 9, 2he 9se of !hemical Admixtures to 5acilitate 4lacement of !oncrete at 5reezing 2emperatures, $roceeding& *rom "eventh )AMET;A)@ @nternational )on*erence on "uperpla&tici?er& and Cther )hemicalAdmixture& in )oncrete Edited %y ( M Malhotra, A)@ @nternational "$4.:-4/, '"A,.5, pp -:43/!

54 Korhonen ) 9, Antifreeze Admixtures for !old =egions !oncreting. A :iterature =eview,"pecial Report 245., '" Army )orp& o* Engineer&, Engineer Re&earch and development)enter, ational Technical @n*ormation "ervice, '"A, "eptem%er :22, :2 pp!

55 "ee re* .D, )hapter ::, pp -D4-22!56 Korhonen ) 9, 3xpedient :ow"2emperature !oncrete Admixtures for the Army, "pecial

Report 224:-, '" Army )orp& o* Engineer&, Engineer Re&earch and development )enter, ational Technical @n*ormation "ervice, '"A, ovem%er :222, . pp!

57 Korhonen ) 9 et al, Antifreeze Admixtures for !oncrete, "pecial Report 2-4.6, '" Army)orp& o* Engineer&, Engineer Re&earch and development )enter, ational Technical@n*ormation "ervice, '"A, Ccto%er :22-, .. pp!

58 http;;###!na!gracecon&truction!com;product!c*m_modecWid:Wdid:59 "ee re*! .D, )hapter :/, pp :24::-!60 "ee re*! -, )hapter 6, pp ./.4.6/!61 Myrdal R, &odern !hemical Admixtures for hotcrete, $roceeding& *rom Third @nternational

"ympo&ium on "prayed )oncrete Edited %y Barton et al, Gol, or#ay, .64.2"eptem%er, or#egian )oncrete A&&ociation, :222, pp 5-5453.!

62 Brge T A, &ode of action of al6ali"free sprayed shotcrete accelerators, N"hotcreteEngineering 7evelopment&, $roc! @nternational )on*erence on Engineering 7evelopment&in "hotcrete Edited %y E " Bernard, 8o%art, Ta&mania, April .4D, .:, Balkema$u%li&her&, The etherland&, .:, pp -243/!


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63 $aglia ) et al, 2he influence of al6ali"free and al6aline shotcrete accelerators within cement systems. I. !haracterization of the setting behavior , )ement and )oncrete Re&earch, 5:, .:, pp 2:542:3!

64 Malte&e ) et al, 3ffects of setting regulators on the efficiency of an inorganic acid based al6ali"free accelerator reacting with a 4ortland cement , )ement and )oncrete Re&earch, 5-,.-, pp /.34/56!

65 Malte&e ) et al, A case history; 3ffect of moisture on the setting behaviour of a 4ortland cement reacting with an al6ali"free accelerator , )ement and )oncrete Re&earch, 5-, .-,

pp 3/6436/!66 Angel&kaar T MBT 8olding AG, !ement Accelerator and &ethod , @nternational $)T

$atent o HC 5;D/3-. A:, 9une /, .5!67 "ommer M, "ika AG, Al6alifreier Abbinde" und 3rhDrtungsbeschleuniger , European

$atent o E$ : :6- 5:- A:, 9anuary ., .!68 Angel&kaar T )on&truction Re&earch W Technology Gm%8, Admixture, @nternational $)T

$atent o HC .D;:6./3 A., 7ecem%er 2, .D!69 +arrington " A et al "ando?4$atent4Gm%8, =asche abbindende Eementzubereitungen,German $atent 7E :2/ 5D 2.2 A:, March .:, :226!

70 (alenti " "ando? Ltd, Aluminium Accelerator for !ement , 'K $atent o GB . 5- D-/ A, ovem%er :2, :226!

71 Myrdal R et al, A #ew !hemical Approach to *btain %igh 3arly trength in hotcrete,N"hotcrete Engineering 7evelopment&, $roc! @nternational )on*erence on Engineering7evelopment& in "hotcrete Edited %y E " Bernard, 8o%art, Ta&mania, April .4D, .:,Balkema $u%li&her&, The etherland&, .:, pp :254:26!

72 $aglia ) et al, An evaluation of the sulfate resistance of cementitious material accelerated with al6ali"free and al6aline admixtures. :aboratory vs. field , )ement and )oncrete

Re&earch, 5., .., pp 66/46-:!73 $aglia ) et al, 2he influence of al6ali"free and al6aline shotcrete accelerators within cement

systems. Influence of the temperature on the sulphate attac6 mechanisms and damage, )ement and )oncrete Re&earch, 55, .5, pp 53-452/!

74 http;;###!*rit?pak!com;product&;product\nca!html75 http;;###!%a&*4admixture&!com;R;rdonlyre&;65-6A5/-4+:D74D/:642+624

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a%lad;8M"\"igunit4L/D/\A+\!pd*94 http;;###!mapei!it;95 http;;###!euclidchemical!com;*ile&hare;$roduct+ile&;m&d&;:2"\22\)!pd*96 "ee re*! 5/, )hapter :5, pp -D-4-D2!97 "ee re*! 6, )hapter :, pp 55455:!98 Rodger " A and 7ou%le 7 7, 2he chemistry of hydration of high alumina cement in the

presence of accelerating and retarding admixtures, )ement and )oncrete Re&earch, :D,:23D, pp -543.!

99 "cian A et al, &echanochemical activation of high alumina cements – %ydrationbehaviour. I , )ement and )oncrete Re&earch, .:, :22:, pp /:46! 100 il*orou&han M R and "harp 9 8, 2he effect of additions of al6aline"earth metal

chlorides on the setting behaviour of a refractory calcium aluminate cement , )ement and)oncrete Re&earch, ./, :22/, pp :/.54:/5D!

Sbf Bk a07025 Accelerating Admixtures for Concrete

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