Admixtures , used in making of concrete in site

Admixtures

1. Admixtures
Admixtureisdefinedasamaterialotherthancement,waterandaggregates
thatisusedasaningredientofconcreteandisaddedtothebatchimmediately
beforeorduringmixing.
-Additiveisamaterialwhichisaddedatthetimeofgrindingcementclinkerat
thecementfactory
-Admixtureisusedtomodifythepropertiesofordinaryconcrete,soasto
makeitmoresuitableforanysituation,moresuitablefortheworkathand
foreconomy
-Admixturesarenosubstituteforgoodconcretedesignandmanufacture.An
admixturemaybeusedonlyafterevaluationofitseffects,ifnecessary,by
usewiththeparticularconcreteandunderspecificconditionofuse
intended.Admixturesshouldbeconformtorelevantspecification.
-Itiseitherinpowderorliquidform.

2. Typesofadmixtures–
-Plasticizers
-RetardersandRetardingplasticizers
-AcceleratorsandAcceleratingplasticizers
-Air-entrainingAdmixtures
-PozzolanicormineralAdmixture
-Damp-proofingandwaterproofingadmixtures
-Gasformingadmixtures
-Air-detrainingadmixtures
-Alkali-aggregateExpansioninhibitingadmixtures
-Workabilityadmixtures
-Groutingadmixtures
-Corrosioninhibitingadmixtures
-Bondingadmixtures
-Fungicidal,Germicidal,Insecticidaladmixtures
-Colouradmixtures

3. Purposeofadmixtures–
1.Tomodifyfreshproperty
•Increasetheworkabilitywithoutincreasethewatercontentratioor
decreasethewatercontentatthesameworkability
•Retardoracceleratethetimeofinitialsetting
•Reduceorpreventthesettlementorcreateslightexpansion
•Modifytherateorcapacityofbleeding
•Modifyorobtainthedesiredpropertiesinfreshconcrete,orinhardened
concrete.
2.Tomodifyhardenproperty
•Reducetheheatofevolution
•Acceleratetherateofstrengthdevelopmentatearlystages
•Increasethedurability
•Decreasethepermeabilityofconcrete

4. Classification of admixtures-
1.Accelerating admixtures
2.Water reducing admixtures
3.Retarding admixtures
4.Air entraining admixtures
5.Mineral
6.Super plasticizers
The essentially/ broad two classes of admixtures in concrete –
1.Chemical admixtures
2.Pozzolanic/ Mineral admixtures -a) Replacing cement
b) Replacing fine aggregate

5. Chemicaladmixtures–Itisusedforthefollowingfourmainpurpose
1.Somechemicalsaremixedwithconcreteingredientsandspreadthrough
outthebodyofconcretetofavourablymodifythemouldingandsetting
propertiesoftheconcretemix.Suchchemicalsaregenerallyknownas
chemicaladmixtures.Admixturesareaddedtoconcretetogiveitcertain
desirablepropertiesineitherthefreshorthehardenedstate.Most
admixturesresultinmodifyingmorethanoneintendedproperty.
2.Somechemicalsareappliedonthesurfaceatconcretetoprotectitduring
orafteritssetting
3.Somechemicalsareappliedonthesurfacesofmodulesusedtoform
concretetoeffecteasymouldreleasingoperation
4.Somechemicalsareappliedtobondorrepairbrokenorchippedconcrete

6. Acceleratingadmixtures
Theseadmixtureswhenaddedtoconcrete,mortarorgroutincreasestherateof
hydrationofhydrauliccement,shortensthetimeofset,acceleratesthe
hardeningordevelopmentofstrengthofconcrete/mortar.Theseadmixtures
functionbyinteractionwithC
3S(Tri-calciumsilicate)componentofthecement
thusincreasingthereactionbetweencementandwater.
Chemicalcomposition–Manysubstancesareknowntoactasacceleratorsfor
concrete.TheyincludeAlkaliHydroxides,Silicates,Fluoro–Silicates,Organic
Compounds,CalciumFormates,CalciumNitrates,CalciumThioSulphates,
AluminiumChlorides,PotassiumCarbonates,SodiumChloridesandCalcium
Chlorides.Ofthesecalciumchloridesaremostwidelyusedbecauseofitsready
availability,lowcost,predictableperformancecharacteristics.Non-chloride
admixturesarepreferredaschloridecontainingonesarebelievedtoaccelerate
corrosionofreinforcement.Forchloridefreeadmixtureisbettertouse.

7. Advantages–
1.Shortensthesettingtimeofcementandthereforeincreasestherateofgain
ofstrength
2.Enablesearlierreleasefromprecastmouldsthusspeedingproduction
3.Reducessegregationandincreasedensityandcompressivestrength
4.Curesconcretefasterandthereforeuniformcuringinwinterandsummer
canbeachieved
5.Earlyuseofconcretefloorsbyacceleratingthesettingofconcrete
6.Reduceswaterrequirements,bleeding,shrinkageandtimerequiredfor
initialset.
Effectofuseofaccelerator–
Table–1belowshowstypicaltestresultsprovidedbyM/s,Asianlaboratories,
NewDelhi
Mixdetails–OPC350kg/cum,Zone2sand26%,5-20mmcrushedaggregates
74%,Dosage1%byweightofcement

9. Retardingadmixtures
Thistypeofchemicaladmixturesdecreasestheinitialrateofreactionbetween
cementandwaterandtherebyretardsthesettingofconcrete.Itfunctionsby
coatingthesurfaceofC3S(Tri-calciumsilicate)components,thus,delayingthis
reactionwiththewater.Reactionproductsareslowtoformassuchthesetting
andhardeningofconcretearedelayedreducingearlycompressivestrengths.
Sincetherateofstiffeningofconcretecanbetoofastinourtropicalclimatic
conditions,sufficienttimefortheconcreteisrequiredfortransportationand
placementbeforesetting.Insuchconditionsretardingadmixturescanbevery
useful.Retardationinsettingtimeto8–10hoursispossiblebysuitableuseof
retarders.Thedelayinhardeningcausedbytheretarderscanbeexploitedto
obtainanarchitecturalfinishofexposedaggregate;theretardersisappliedto
theinteriorsurfaceoftheformworksothatthehardeningoftheadjacent
cementisdelayed.Thiscementcanbebrushedoffaftertheformworkhasbeen
strucksothatanexposedaggregatesurfaceisobtained.

10. Chemicalcomposition–Theseadmixturescanbedividedinseveralcategories
basedontheirchemicalcomposition.Themainingredientsofretardersareas
follows:
1.Lignosulphonicacidsandtheirsalts,e.g.Na,CaorNH4,
2.Hydro-carboxylicacidsandtheirsalta
3.Carbohydratesincludingsugar
4.Inorganicsaltsbasedonflourates,phosphates,oxides,boraxadmagnesium
salts
Advantages-
1.Improvesworkability,cohesionandextendssettingtime,provides
protectionagainstdelaysandstoppagesandfacilitateskeepingworkable
concreteforextendedperiod.
2.Inthelargeconstruction,goodworkabilityoftheconcretethroughoutthe
placingperiodandpreventionofcoldjointsisensuredbyaddingretarders
intheconcrete.

11. 3.Extendedsettingtimeminimiserisksoflongdistancedeliveryinhot
weather,improvespumpabilityofconcretebyextendedsettingperiodand
improvedworkabilityofconcrete.
4.Reducesbleedingandsegregationwherepoorsandgradingareunavoidable
5.Reducesadverseenvironmentaleffectsofvariousnatureonconcreteand
embeddedsteelbyconsiderablereductioninpermeability
Effectofuseofretarder-
Retardingadmixtureformsafilmaroundthecementgrainthatpreventor
delaysthereactionwithwater.Aftersometimes,thisfilmbreaksandnormal
hydrationtakesplace.Table2belowshowstypicaltestresultsprovidedby
M/sFOSROCChemicals(I)Ltd.,Bangalore.
Mix:Sandzone2(IS:383)–35%,Aggregate20–5mm(IS:383)-65%,
CementOPC(IS:269)

13. Plasticizer(WaterReducer)Admixtures
Amaterial,whicheitherincreasesworkabilityoffreshlymixedconcrete
withoutincreasingwatercementratioormaintainsworkabilitywitha
reducedamountofwater,istermedaswaterreducingadmixture.
Astheirnameimplies,thefunctionofwaterreducingadmixtureistoreduce
thewatercontentofthemix,usuallyby5to10%,sometimes(inconcreteof
veryhighworkability)upto15%.Thus,thepurposeofusingawaterreducing
admixtureinaconcretemixistoallowareductioninthewatercementratio
whileretainingthedesiredworkability,or,alternatively,toimproveits
workabilityatagivenwatercementratio.Theactualreductioninwater
dependsondoseofadmixtures,cementcontent,typeofaggregateused,
ratioofcement,fineandcoarseaggregateetc.Therefore,thetrialmixes
containinganactualmaterialtobeusedonthejobareessentialtoachieve
optimumproperties.

14. Chemical Composition:
The chemicals used as plasticizer (water reducing admixtures)
are as follows:
i.Lignosulfonicacids, derivatives and their salts.
ii.Hydroxylated carboxylic acids, their salts and derivatives.
iii.Nepthalenesulphonicacid based
iv.Sulfonated melamine polycondensationproducts
v.Blends of above
vi.Inorganic material like borates, phosphates, amines and
their derivatives, carbohydrates, sugar and certain
polymeric compounds like cellulose, ethers etc.

15. Advantage:
Theyincreasetheworkabilityoftheconcretewithoutreducingthe
compressivestrengthorwithoutchangingwater-cementratio.Thisis
particularlyusefulwhenconcreteporesarerestrictedeitherdueto
congestedreinforcementorduetothinsections.
Highstrengthcanbeobtainedwiththesamecementcontentbyreducing
watercementratio.
Asavinginthequantityofcement(approx.upto10%)canbeachieved
keepingthesamewater/cementratioandworkability.
EffectofuseofPlasticizers:
TypicaltestresultsprovidedbyM/s.M.C.Bauchemie(1)Pvt.Ltd.
Mumbai,showingincreaseinworkabilityandincreaseinstrengthare
givenbelowintable-3.

17. 1.Reducedcementcontentkeepingsamewater-cementratioand
workability.Thiswillleadtoeconomy.
2.Reducedwater-cementratiokeepingsamewatercontentandsame
workability.Thisleadtoincreaseinstrength.
3.Increasedworkabilitykeepingsamewater–cementratioandcement
content.Thisisspeciallyrequiredwhenworkabilityretentionfor
pumpingetc.isneeded.
Dosagerangingfrom0.15to0.6%byweightofcement(differentdosesfor
differentproducts)arerecommendedbymanufacturers,however,itshall
befixedasperdesignrequirementsandaftersitetrial.
SuperplasticzerAdmixtures:
Normalwaterreducersarewellestablishedadmixturescalledplasticizers
inconcretetechnology.Anormalwaterreduceriscapableofreducing
waterrequirementsby10to15%.Higherwaterreductions,by
incorporating

18. largeramountsoftheseadmixtures,resultinundesirableeffectson
concretelikebleeding,segregationandhardening.So,anewclassof
waterreducers,chemicallydifferentfromthenormalwaterreducerand
capableofreducingwatercontentbyabout30%hasbeendeveloped.
Theadmixturesbelongingtothisclassareknownassuperplasticizers.
Superplasticisersareinfacttheextendedversionofplasticisers.
Atagivenwater/cementratioandwatercontentinthemix,the
dispersingactionofsuperplasticizerincreasestheworkabilityof
concrete,typicallybyraisingtheslumpfrom75mmto200mm,themix
remainingcohesive.Theresultingconcretecanbeplacedwithlittleor
nocompactionandisnotsubjecttoexcessivebleedingorsegregation.
Suchconcreteistermedasflowingconcreteandisusefulforplacingin
veryheavilyreinforcedsections,ininaccessibleareas,infloororroad
slabs,andalsowhereveryrapidplacingisdesired.

19. Theprincipalmodeofactionofsuperplasticizersistheirabilityto
dispersecementparticlesveryefficiently.Astheydonotentrainair,
theycanbeusedathighdosagerateswithoutaffectingstrength.
ChemicalComposition:
Thereexistfourmaincategoriesofsuperplasticizersbasedontheir
chemicalcomposition:
1.Sulfonatedmelamineformaldehydecondensates
2.Sulfonatednaphthaleneformaldehydecondensates
3.Modifiedlignosulfonates
4.Otherssuchassulfonicacidestersandcarbohydrateesters

20. Advantages:
1.Cementcontentcanbereducedtoagreaterextentkeepingthe
samewater/cementratio.Thiswillleadtoeconomy.
2.Water–cementratiocanbereducedsignificantlykeepingsame
cementcontentandworkability.Thiswillleadtoincreasein
strength.
3.Higherworkabilityatverylowwatercementratiolikecasting
concretewithheavyreinforcement.
4.Reductioninpermeability
5.Whereearlystrengthdevelopmentisrequiredinprestressed
concreteorcastingoffloor,whereearlyaccessforfinishing
equipmentisrequired.

21. EffectofuseofSuperplasticizers:
Forincreasingtheworkabilityofthemix,thenormaldosagesof
superplasticizersis1to3litrepercum.Ofconcreteoftheliquid
superplasticizercontainingabout40%ofactivematerial.When
superplasticizersareusedforlargewaterreductionandforhigh
strength,theirdosageismuchhigher:5to20litrepercubicmetreof
concrete.Generally,thedosagerecommendedbythemanufacturer
shouldbetakenasguidelinesandthecorrectdosagebedecidedbased
onsitetrials.Thetypicaltestresultsshowingtheincreasein
workabilityandcreaseinstrengthduetouseofsuperplasticizer,given
intables4-6havebeentakenfromtheliteratureprovidedbyCICO
structuralwaterproofingPvt.Ltd.NewDelhi.

25. AirEntrainingadmixture
Thisisanadmixtureforconcreteormortarwhichcausesairtobeincorporatedinthe
formofminutebubblesintheconcreteormortarduringmixing,usuallytoincrease
workabilityandresistancetofreezingandthawing.Airentrainedalsobreaksthe
continuityofcapillaries.
Thedosagesrequiredarebetween0.005to0.05%bymassofconcreteanditisadvisable
tomixitwithbatchingwaterforuniformdispersion.AsperdepartmentofAtomic
EnergyPractice,theaircontentiscontrolledbetween3to6%.Methodofmeasuringair
contentisgiveninIS1190
Theairvoidspresentinconcretecanbebroughtundertwogroups–
1.Entrainedair–Itisintentionallyincorporated.Itisminutesphericalbubblesofsize
rangingfrom6–80microns,distributedevenlyintheentiremassofconcrete.
2.Entrappedair–Thisvoidspresentintheconcreteduetoinsufficientcompaction.
Theseentrappedairvoidsmaybeofanyshapeandsizenormallyembracingthecontour
ofaggregatessurfaces.Theirsizemayrangefrom10to1000micronsormore.Theyare
notuniformlydistributedthroughouttheconcretemass.

26. Chemicalcomposition–Themajorproportionofcommercialproductsisbasedonthe
followingchemicalmaterials,setoutinorderofprobabledecreasinguse:
1.Abieticandpimericacidsalts
2.Fattyacidsalts
3.Alkyl–arylsulphonates
4.Alkylsulphonates
5.Phenolethoxylates
Advantages–
1.Durability
2.Reducedbleedingandsegregationbecauseof:
a)Attachmentofairbubbleswithcementparticleandlinkingthem
b)Increaseininterparticleattractioncausedbyadsorptionofairentrainer
c)Bubbleactingasextrafinefillerandincreasedtotalsurfaceareaofconstituents
relativetowatervolume
d)Waterflowbetweencementparticlesisrestricted
3.Workabilityincreasedduetoactionofairbubblesasballbearingwhichassistmovement
ofparticleseachother

27. Disadvantages–
1.Decreaseinstrengthduetoincreaseinporosity
2.Aircontentofhardenedpastecannotbecontrolledlowair–entraining
resultsdurability,whereaslargeofairentrainingcausesstrength
Waterproofersadmixtures
Thesechemicalsareaddedtoconcreteormortaratthetimeofpreparation
tomakethestructurewaterproof.Theyreactwiththelimecontainedin
cementtoforminorganicsaltswhichblocktheporesandcapillaries,thereby
reducingmoisturepenetration.
Chemicalcompositions–Waterproofersmayobtainedinpowderorliquid
formandconsistsofpore-fillingorwaterrepellentmaterials.Thechief
materialsinthepore-fillingclassarealkalinesilicates,notablysilicatesof
soda,

28. Aluminium,zincsulphatesandchloridesofaluminiumandcalcium.Theseare
allchloridesofaluminiumandcalcium.Theseareallchemicallyactiveand
acceleratethesettingtimeofconcretebutmayencouragecorrosionof
embeddedsteel.Thechemicallyinactivepore-fillingmaterialsarefinally
groundchalk,fuller’searth,andtale.Theyactasworkabilityaidsandresultin
anincreaseindensity.Theyareusedinconjunctionwithcalciumsoap.
Materialsinthewater-repellentclassaresodaandpotashsoaps,towhoch
lime,alkaliorsilicatesarepotashsoaps,towhichlime,alkaliorsilicatesare
sometimesadded.Chemicallyinactivematerialsinthewater-repellentclass
arecalciumsoaps,resins,vegetablesoils,fats,waxes,bitumenandcoaltar.
Corrosion–inhabitingadmixture–Theproblemofcorrosionofreinforcing
steelinconcreteisuniversal.Butismoreacuteinconcreteexposedtosaline
water.Thechemicalsresistscorrosionofreinforcement,generally,alkalinityof
concreteisanadequateprotectionforsteel.However,inadverse

29. Environment,Sodiumbenzonate,calciumlignosulphonate,andsodiumnitrate
haveshowngoodresult.
Antifungaladmixtures–Theseareaddedtocontrolandinhibitthegrowthof
bacteriaorfungionsurfacesexposedtomoisture.Polyhalogenatedphenel,
dieldrinemilsion,andcoppercompoundsaresomeofthechemicalsusedfor
thispurpose.
Water-repellentadmixture–Suchmaterialsreducethecapillaryabsorptionof
fluidsbythehardenedconcreteandthereforeloweritspermeability.Mineral
andvegetableoilsormetallicsoap(calciumstearate)areclaimedtoexhibit
thispropertybutitshouldbeemphasizedthattheseadmixturesdonot
preventwaterpenetrationintoorthroughconcreteandthereforecannotbe
usedforwaterproofing.Also,water-repellentmayhaveaneffectonthe
subsequentsurfacetreatmentofconcrete.

30. MineraladmixtureorPozzolanic-Inthemineraladmixture,weusematerials,
whichreplacecementi.e.theyaresofine,thattheirfinenessiscomparableto
thatofcement,andthereforewetrytotreatthemasapartofcementin
consideringconcrete.Otherthanthese,thereareothermaterials,whichare
usedattimesreplacingfineaggregate,i.esand.Mineraladmixtureare
siliciousmaterialswhichhavefineparticlesize.Theyareaddedtoconcrete
eitherasafillerortoimprovefavourablycertaindesiredpropertiessuchas
durability.Mineraladmixturesareclassifiedaseitherpozzolanicor
cementitious.Theyareeithernaturalmaterialsorby–productssuchasflyash
ofindustries.TheIS:456-2000permitstheuseofmineraladmixturefor
modifyingthepropertiesofconcrete.Ithasbeenamplydemonostratedthat
thebestpozzolansinoptimumproportionsmixedwithportlandcement
improvesmanyqualitiesofconcretesuchas–
•Lowertheheatofhydrationandthermalshrinkage
•Increasethewatertightness

31. •Typeequationhere.Reducethealkali–aggregatereaction
•Improveworkability
•Improveresistancetoattackbysulphatesoilsandseawater
•Lowercosts
Pozzolanicmaterials-Historically,theuseofpozzolonicmaterialisverywell
known,andthesematerialshavenohydraulicpropertiesoftheirown,and
theydonotsimplyhardenbyaddingwater,rathertheyreactwithcalcium
hydroxideandyieldsproducts,Similartothoseformedduringcement
hydration.So,whatthesemineraladmixturesdo.Theydonotreactwithwater
butduringreactingwaterwithcementproducelargeamountofcalcium
hydroxide,andthiscalciumhydroxideisreactwithmineraladmixture.C3S+
H2O→C-S-H+Ca(OH)2 (Ca(OH)2=CH)
C2S+H2O→C-S-H+Ca(OH)2
S+CH→C-S-H(Thisgelissimilartotheoneformedduringhydrationof
cement)

32. Pozzolanicmaterialscanbedividedintotwogroups–
1.NaturalPozzolans–Naturalpozzolanssuchasclayandshale,
diatomaceousearth,volcanictuffsandpumicitesetc.needsfurther
grindingandsometimesneedscalciningtoactivatethemtoshow
pozzolanicactivities.InHirakuddamconstructioninOrissa,naturally
occurringclayknownasTalabaraclayhasbeenusedaspozzolanic
materials.
2.Artificalpozzolans–
a)Flyash–Ashprecipitatedelectrostaticallyormechanicallyfromexhaust
gassesofthermalpowerstation.Theparticlesaresphericalandfine.
Generally30-40%pozzuolanawithordinarycementthengrinded.Rateof
hydrationislow.Flyashcanbegroupedundereitherhigh–calcium(15-35)or
low-calcium(≤10%)typedependingonitsCaocontent.Theunburntcarbon
contentinflyashshouldbelessthan5%.Theuseofflyashasconcrete

33. Admixturenotonlyextendstechnicaladvantagestothepropertiesof
concretebutalsocontributestotheenvironmentalpollutioncontrol.Flyash
usedasordinarycement,usedindam(InIndia,Rihanddam),massconcrete,
marineandhydraulicconstructionlowearlystrengthbutstrengthsimilarto
ordinaryportlandcementatlaterages.Thesurfaceareaoftheparticlesare
intherangeof300-400m
2
/kg.Flyashconsistingmostlyofsilica,aluminaand
iron,flyashisapozzolan–asubstancecontainingaluminousandsilicious
materialthatformscementinthepresenceofwater.Whenmixedwithlime
andwateritformsacompoundsimilartoportlandcement.Usageofflyash
asacementreplacementmaterialimproves.
b)Silicafume–Itisveryfinenon-crystallineSio2,isaby-productofferro-
siliconIndustry.Itismadeatatemperatureofapprox.2000C.Itssizeisabout
0.1Mm(20-25m2/gm).Itactsasanexcellentpore-fillingmaterial.Ithas
sphericalshape.Itcanbeusedinproportionsof5-10%ofthecementcontent

34. Inamix(ascementreplacement).Silicafumehasbecomeoneofthe
necessaryingredientsformakinghighstrengthandhighperformance
concrete.SilicafumeusedoneoftheflyoveratMumbai.Silicafume100times
smallerthanordinaryportlandcementwithasurfaceareaontheorderof
20,000m2/kg.Earliersilicafumedischargedintoatmosphere.After
environmentalconcernsnecessitatedthecollection.
c)Ricehuskash–Itisawasteproductofricemills.Eachtonneofpaddycan
generate0.2tonneofhusk.Thisisahighlyreactivepozzolanicadmixture.Itis
producedbycontrolledcombustionofhusk-retainingsilicainthenon-
crystallineform,withcellularstructure.Thefinenessisoftheorderof50-
60m2/gm.Ricehuskashcontributestohighstrengthandhighimpermeability
ofconcrete.
d)Metakaoline–Metakaolineisobtainedbycalcinationofpureorrefined
clayattemperatureof650-850Candbygrindingitsubsequentlytoachievea
finenessof700-900m2/kg.Itisahighlyreactivepozzolana.

38. Addingmineraladmixture-Thetwooptionsforaddingthemineral
admixturestotheconcrete
1)Duringthemanufacturingofcementatthecementplant,andthenusing
this“blendedcement“thatisthismineraladmixtureisaddedtothe
cementatthecementplantsothecementisnotordinaryportlandcement
(OPC),therefore,theproductofthecementplantnowisnotordinaryport
landcement,itisblendedcementbecausethemineraladmixturehas
alreadybeenaddedtoO.P.C
2)Duringthemixingoftheconcreteattheconcreteplantorthesiteof
mixing,isaddthemineraladmixture,duringthemixingoftheconcrete,at
theconcreteplantoratthesiteofmixing.Inthiscase,thecementusedis
OPCandthemineraladmixtureadded,inanappropriatedosageinthe
plant

39. Chemicalmineral-Whathappenswhenweusearetarding,letusseethatthisisthe
normalslumploss;thatisifwehaveanoriginalslumpvalue.Asthehydrationprocess
continues,theconcretecontinuestolooseitsslump.Itcontinuestobecomestifferand
thisistheprocesstheblacklinehere,istheprocessfornormalconcrete;thatisaconcrete
whichdoesnothaveanychemicaladmixture.Now,ifwewanttoacceleratetheprocess,
wewanttheconcretetohardenearlierthenweuseanaccelerator,wegetrapidslump
loss.
Aschematicrepresentationofslumplossovertimetoshowregulationofsettingof
cement(andthereforeofconcrete)