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CHAPTER 8

Air-Entrained Concrete

One of the greatest advances in concrete technology wasthe development of air-entrained concrete in the mid-1930s Today air entrainment is recommended for nearlyall concretes principally to improve freeze-thaw resist-

ance when exposed to water and deicing chemicalsHowever there are other important benefits of entrainedair in both freshly mixed and hardened concrete

Air-entrained concrete is produced by using either anair-entraining cement or adding an air-entraining admix-ture during batching The air-entraining admixture stabi-lizes bubbles formed during the mixing processenhances the incorporation of bubbles of various sizes bylowering the surface tension of the mixing waterimpedes bubble coalescence and anchors bubbles tocement and aggregate particles

Anionic air-entraining admixtures are hydrophobic(repel water) and are electrically charged (nonionic or no-charge admixtures are also available) The negative elec-tric charge is attracted to positively charged cementgrains which aids in stabilizing bubbles The air-entraining admixture forms a tough water-repelling film

similar to a soap film with sufficient strength and elas-ticity to contain and stabilize the air bubbles and preventthem from coalescing The hydrophobic film also keepswater out of the bubbles The stirring and kneading action

of mechanical mixing disperses the air bubbles The fineaggregate particles also act as a three-dimensional grid tohelp hold the bubbles in the mixture

Entrained air bubbles are not like entrapped air voidswhich occur in all concretes as a result of mixing han-dling and placing and are largely a function of aggregatecharacteristics Intentionally entrained air bubbles areextremely small in size between 10 to 1000 micro m in diam-eter while entrapped voids are usually 1000 micro m (1 mm) orlarger The majority of the entrained air voids in normalconcrete are between 10 micro m and 100 micro m in diameter Asshown in Fig 8-1 the bubbles are not interconnected theyare well dispersed and randomly distributed Non-air-entrained concrete with a 25-mm (1-in) maximum-sizeaggregate has an air content of approximately 1 1 frasl 2 Thissame mixture air entrained for severe frost exposurewould require a total air content of about 6 made up of both the coarser ldquoentrappedrdquo air voids and the finerldquoentrainedrdquo air voids

PROPERTIES OF AIR-ENTRAINEDCONCRETE

The primary concrete properties influenced by air entrain-ment are presented in the following sections Abrief sum-mary of other properties not discussed below is presentedin Table 8-1

Freeze-Thaw Resistance

The resistance of hardened concrete to freezing andthawing in a moist condition is significantly improved bythe use of intentionally entrained air even when variousdeicers are involved Convincing proof of the improve-

Fig 8-1 Polished section of air-entrained concrete as seenthrough a microscope (67840)

129

HOMEPAGE

Video



ment in durability effected by air entrainment is shown inFigs 8-2 and 8-3

As the water in moist concrete freezes it producesosmotic and hydraulic pressures in the capillaries andpores of the cement paste and aggregate If the pressureexceeds the tensile strength of the paste or aggregate thecavity will dilate and rupture The accumulative effect of successive freeze-thaw cycles and disruption of paste and

130

Design and Control of Concrete Mixtures N EB001

Properties EffectAbrasion Little effect increased strength increases

abrasion resistanceAbsorption Little effectAlkali-silica reactivity Expansion decreases with increased air

Bleeding Reduced significantlyBond to steel DecreasedCompressive strength Reduced approximately 2 to 6 per per-

centage point increase in air harsh or leanmixes may gain strength

Creep Little effectDeicer scaling Significantly reducedDensity Decreases with increased airFatigue Little effectFinishability Reduced due to increased cohesion (sticki-

ness)Flexural strength Reduced approximately 2 to 4 per per-

centage point increase in airFreeze-thaw Significantly improved resistance to

resistance water-saturated freeze-thaw deteriorationHeat of hydration No significant effectModulus of elasticity Decreases with increased air

(static) approximately 720 to 1380 MPa (105000to 200000 psi) per percentage point of air

Permeability Little effect reduced water-cement ratioreduces permeability

Scaling Significantly reducedShrinkage (drying) Little effectSlump Increases with increased air approximately

25 mm (1 in) per 1 frasl 2 to 1 percentage pointincrease in air

Specific heat No effectSulfate resistance Significantly improved

Stickiness Increased cohesionmdashharder to finishTemperature of wet No effect

concreteThermal conductivity Decreases 1 to 3 per percentage point

increase in airThermal diffusivity Decreases about 16 per percentage

point increase in airWater demand of wet Decreases with increased air

concrete for equal approximately 3 to 6 kgm3 (5 to 10slump lbyd3) per percentage point of air

Watertightness Increases slightly reduced water-cementratio increases watertightness

Workability Increases with increased air

Air content percent

C y c l e s o f f r e e z i n g a n d

t h a w i n g

f o r 5 0

r e d u c t i o n i n d y n a m i c m o d u l u s o f e l a s t i c i t y

00

200

400

600

800

1000

1200

1400

1600

1800

2000

1 2 3 4 5 6

SymbolsNon-air-entrainedAir-entrained

Fig 8-2 Effect of entrained air on the resistance of concrete tofreezing and thawing in laboratory tests Concretes were madewith cements of different fineness and compositio n and withvarious cement contents and water-cement ratios (Bates andothers 1952 and Lerch 1960 )

Table 8-1 Effect of Entrained Air on ConcreteProperties

Note The table information may not apply to all situations

aggregate eventually cause significant expansion anddeterioration of the concrete Deterioration is visible in theform of cracking scaling and crumbling (Fig 8-3) Powers(1965) and Pigeon and Pleau (1995) extensively review themechanisms of frost action

Hydraulic pressures are caused by the 9 expansionof water upon freezing in this process growing ice crystalsdisplace unfrozen water If a capillary is above critical sat-uration (917 filled with water) hydraulic pressuresresult as freezing progresses At lower water contents nohydraulic pressure should exist

Osmotic pressures develop from differential concen-trations of alkali solutions in the paste (Powers 1965a) Aspure water freezes the alkali concentration increases inthe adjacent unfrozen water A high-alkali solutionthrough the mechanism of osmosis draws water fromlower-alkali solutions in the pores This osmotic transferof water continues until equilibrium in the fluidsrsquo alkaliconcentration is achieved Osmotic pressure is considereda minor factor if present at all in aggregate frost actionwhereas it may be dominant in certain cement pastesOsmotic pressures as described above are considered to be a major factor in ldquosalt scalingrdquo

Capillary ice (or any ice in large voids or cracks)draws water from pores to advance its growth Also sincemost pores in cement paste and some aggregates are too



small for ice crystals to form water attempts to migrate tolocations where it can freeze

Entrained air voids act as empty chambers in thepaste where freezing and migrating water can enter thusrelieving the pressures described above and preventingdamage to the concrete Upon thawing most of the waterreturns to the capillaries due to capillary action and pres-sure from air compressed in the bubbles Thus the bubblesare ready to protect the concrete from the next cycle of freezing and thawing (Powers 1955 Lerch 1960 andPowers 1965)

The pressure developed by water as it expandsduring freezing depends largely upon the distance thewater must travel to the nearest air void for reliefTherefore the voids must be spaced close enough toreduce the pressure below that which would exceed thetensile strength of the concrete The amount of hydraulicpressure is also related to the rate of freezing and the per-meability of the paste

The spacing and size of air voids are important factorscontributing to the effectiveness of air entrainment in con-crete ASTM C 457 describes a method of evaluating theair-void system in hardened concrete Most authoritiesconsider the following air-void characteristics as represen-tative of a system with adequate freeze-thaw resistance(Powers 1949 Klieger 1952 Klieger 1956 Mielenz and

others 1958 Powers 1965 Klieger 1966 Whiting and Nagi1998 and Pinto and Hover 2001 )

1 Calculated spacing factor iquest (an index related to thedistance between bubbles but not the actual averagespacing in the system)mdashless than 0200 mm (0008 in)(Powers 1954 and 1965 )

2 Specific surface α (surface area of the air voids)mdash24square millimeters per cubic millimeter (600 sq in percubic inch) of air-void volume or greater

Current US field quality control practice usually in-volves only the measurement of total air volume in freshlymixed concrete this does not distinguish air-void size inany way In addition to total air volume Canadian prac-tice also requires attainment of specific spacing factorsFig 8-4 illustrates the relationship between spacing factorand total air content Measurement of air volume alonedoes not permit full evaluation of the important charac-teristics of the air-void system however air-entrainmentis generally considered effective for freeze-thaw resistancewhen the volume of air in the mortar fraction of the con-cretemdashmaterial passing the 475-mm (No 4) sievemdashisabout 9 plusmn 1 (Klieger 1952) or about 18 by paste volumeFor equal admixture dosage rates per unit of cement theair content of ASTM C 185 (AASHTO T 137) mortar would be about 19 due to the standard aggregatersquos properties

131

Chapter 8 N Air-Entrained Concrete

Fig 8-3 Effect of weathering on boxes and slabs on ground at the Long-Time Study outdoor test plot Project 10 PCASkokie Illinois Specimens at top are air-entrained specimens at bottom exhibiting severe crumbling and scaling are non-air-entrained All concretes were made with 335 kg (564 lb) of Type I portland cement per cubic meter (cubic yard)Periodically calcium chloride deicer was applied to the slabs Specimens were 40 years old when photographed (seeKlieger 1963 for concrete mixture information) (69977 69853 69978 69854)



resistant with a low water-cement ratio Fig 8-5 illustratesthe effect of water-cement ratio on the durability of non-air-entrained concrete

Concrete elements should be properly drained andkept as dry as possible as greater degrees of saturationincrease the likelihood of distress due to freeze-thawcycles Concrete that is dry or contains only a small amountof moisture in service is essentially not affected by even alarge number of cycles of freezing and thawing Refer tothe sections on ldquoDeicer-Scaling Resistancerdquo and ldquoRecom-mended Air Contentsrdquo in this chapter and to Chapter 9 formixture design considerations

Deicer-Scaling Resistance

Deicing chemicals used for snow and ice removal cancause and aggravate surface scaling The damage is pri-marily a physical action Deicer scaling of inadequatelyair-entrained or non-air-entrained concrete duringfreezing is believed to be caused by a buildup of osmotic

and hydraulic pressures in excess of the normal hydraulicpressures produced when water in concrete freezes Thesepressures become critical and result in scaling unless en-trained air voids are present at the surface and throughoutthe sample to relieve the pressure The hygroscopic (mois-ture absorbing) properties of deicing salts also attractwater and keep the concrete more saturated increasingthe potential for freeze-thaw deterioration Howeverproperly designed and placed air-entrained concrete willwithstand deicers for many years

Studies have also shown that in absence of freezingthe formation of salt crystals in concrete (from externalsources of chloride sulfate and other salts) may con-tribute to concrete scaling and deterioration similar to thecrumbling of rocks by salt weathering The entrained airvoids in concrete allow space for salt crystals to grow thisrelieves internal stress similar to the way the voids relievestress from freezing water in concrete (ASCE 1982 andSayward 1984 )

Deicers can have many effects on concrete and theimmediate environment All deicers can aggravate scalingof concrete that is not properly air entrained Sodium chlo-ride (rock salt) (ASTM D 632 or AASHTO M 143) calciumchloride (ASTM D 98 or AASHTO M 144) and urea are themost frequently used deicers In the absence of freezingsodium chloride has little to no chemical effect on concrete but can damage plants and corrode metal Calcium chlo-ride in weak solutions generally has little chemical effecton concrete and vegetation but does corrode metal

Studies have shown that concentrated calcium chloridesolutions can chemically attack concrete (Brown and Cady1975) Urea does not chemically damage concrete vegeta-tion or metal Nonchloride deicers are used to minimizecorrosion of reinforcing steel and minimize groundwaterchloride contamination The use of deicers containing am-monium nitrate and ammonium sulfate should be strictlyprohibited as they rapidly attack and disintegrate concrete

The air content of concrete with 19-mm (3

frasl 4-in) maximum-size aggregate would be about 6 for effective freeze-thaw resistance

The relationship between air content of standardmortar and concrete is illustrated by Taylor (1948) Pintoand Hover (2001) address paste air content versus frostresistance The total required concrete air content for durability increases as the maximum-size aggregate is reduced(due to greater paste volume) and the exposure conditions become more severe (see ldquoRecommended Air Contentsrdquolater in this chapter)

Freeze-thaw resistance is also significantly increased

with the use of the following (1) a good quality aggregate(2) a low water to cementing materials ratio (maximum045) (3) a minimum cementitious materials content of 335 kgm 3 (564 lbyd 3) (4) proper finishing and curingtechniques and (5) a compressive strength of 28 MPa(4000 psi) when exposed to repeated freeze-thaw cyclesEven non-air-entrained concretes will be more freeze-thaw

132


100

80

60

40

20

00 50 100 150 200 250 300 350

Number of freeze ndash thaw cycles

R e

l a t i v e d y n a m

i c m o d u

l u s

030035040045050

Water tocement ratio

ASTM C 666

Fig 8-5 Durability factors vs number of freeze-thaw cycles forselected non-air-entrained concretes (Pinto and Hover 2001 )

1100

1000

900

800

700

600

500

400

300

200

1001 2 3 4 5 6 7

Air content in concrete

S p a c i n g

f a c t o r m

i c r o m e t e r s

Non-air-entrained mixtures

Air-entrained mixtures

Fig 8-4 Spacing factor as a function of total air content inconcrete (Pinto and Hover 2001 )



Mixture Control Fly ash (Class F) Slag Calcined shale Calcined shaleMass replacementof cement 0 15 40 15 25

Scale rating at25 cycles 1 1 1 1 1


Magnesium chloride deicers have come under recent criti-cism for aggravating scaling One study found that mag-nesium chloride magnesium acetate magnesium nitrateand calcium chloride are more damaging to concrete thansodium chloride (Cody Cody Spry and Gan 1996 )

The extent of scaling depends upon the amount of deicer used and the frequency of application Relativelylow concentrations of deicer (on the order of 2 to 4 bymass) produce more surface scaling than higher concentra-tions or the absence of deicer (Verbeck and Klieger 1956 )

Deicers can reach concrete surfaces in ways otherthan direct application such as splashing by vehicles anddripping from the undersides of vehicles Scaling is moresevere in poorly drained areas because more of the deicersolution remains on the concrete surface during freezingand thawing Air entrainment is effective in preventingsurface scaling and is recommended for all concretes thatmay come in contact with deicing chemicals (Fig 8-6)

A good air-void system with a low spacing factor(maximum of 200 micrometers) is perhaps more important

to deicer environments than saturated frost environmentswithout deicers The relationship between spacing factorand deicer scaling is illustrated in Fig 8-7 A low water toportland cement ratio helps minimize scaling but is notsufficient to control scaling at normal water-cement ratios

Fig 8-8 illustrates the overriding impact of air contentover water-cement ratio in controlling scaling

To provide adequate durability and scale resistance insevere exposures with deicers present air-entrained con-crete should be composed of durable materials and havethe following (1) a low water to cementitious materialsratio (maximum 045) (2) a slump of 100 mm (4 in) or lessunless a plasticizer is used (3) a cementitious materialscontent of 335 kgm 3 (564 lbyd 3) (4) proper finishingafter bleed water has evaporated from the surface(5) adequate drainage (6) a minimum of 7 days moistcuring at or above 10degC (50degF) (7) a compressive strengthof 28 MPa (4000 psi) when exposed to repeated freeze-thaw cycling and (8) a minimum 30-day drying periodafter moist curing if concrete will be exposed to freeze-thaw cycles and deicers when saturated Target air con-

tents are discussed in ldquoRecommended Air Contentsrdquo atthe end of this chapter

Normal dosages of supplementary cementitiousmaterials should not effect scaling resistance of properlydesigned placed and cured concrete (Table 8-2) The ACI318 building code allows up to 10 silica fume 25 flyash and 50 slag as part of the cementitious materials fordeicer exposures However abuse of these materials along

133


20 04

03

02

01

18161412100806040200

0 10 20 30 40 50Number of cycles

C u m u l a

t i v e m a s s

l o s s k g m 2

C u m u l a

t i v e m a s s

l o s s l b f t 2

246

Air content

ASTM C 672deicer scaling test

Fig 8-6 Cumulative mass loss for mixtures with a waterto cement ratio of 045 and on-time finishing (Pinto andHover 2001 )

5

4

3

2

1

00 400200 800600

Spacing factor micro m

V i s u a

l r a t i n g


Rating0 = no scaling5 = severe scaling

Fig 8-7 Visual rating as a function of spacing factor for aconcrete mixture with a water to cement ratio of 045 (Pintoand Hover 2001 )

Concrete had 335 kg of cementing materials per cubic meter (565 lbyd 3) a Type I portland cement a water to cementing materials ratio of 050a nominal slump of 75 mm (3 in) and a nominal air content of 6 Test method ASTM C 672 Results are for specific materials tested in 2000and may not be representative of other materials Scale rating 1 = very slight scaling (3 mm depth maximum) with no coarse aggregate visible2 = slight to moderate scaling

Table 8-2 Deicer Scaling Resistance (Visual Ratings) of Concrete with Selected Supplementary Cementing Materials



The effect of mix design surface treatment curing orother variables on resistance to surface scaling can be eval-uated by ASTM C 672

Sulfate Resistance

Sulfate resistance of concrete is improved by air entrain-ment as shown in Figs 8-9 and 8-10 when advantage istaken of the reduction in water-cement ratio possible withair entrainment Air-entrained concrete made with a lowwater-cement ratio an adequate cement content and a sul-fate-resistant cement will be resistant to attack from sulfatesoils and waters

Resistance to Alkali-Silica Reactivity

The expansive disruption caused by alkali-silica reactivityis reduced through the use of air-entrainment (Kretsinger1949) Alkali hydroxides react with the silica of reactiveaggregates to form expansive reaction products causingthe concrete to expand Excessive expansion will disrupt

and deteriorate concrete As shown in Fig 8-11 the expan-sion of mortar bars made with reactive materials is re-duced as the air content is increased

Strength

When the air content is maintained constant strengthvaries inversely with the water-cement ratio Fig 8-12shows a typical relationship between 28-day compressivestrength and water-cement ratio for concrete that has therecommended percentages of entrained air As air contentis increased a given strength generally can be maintained by holding the voids (air + water) to cement ratio con-

stant this may however necessitate some increase incement contentAir-entrained as well as non-air-entrained concrete

can readily be proportioned to provide similar moderatestrengths Both generally must contain the same amount

with poor placing and curing practices can aggravatescaling Consult local guidelines on allowable dosagesand practices for using these materials in deicer environ-ments as they can vary from ACI 318 requirementsAir Drying The resistance of air-entrained concrete tofreeze-thaw cycles and deicers is greatly increased by anair drying period after initial moist curing Air dryingremoves excess moisture from the concrete which in turnreduces the internal stress caused by freeze-thaw condi-tions and deicers Water-saturated concrete will deterio-rate faster than an air-dried concrete when exposed tomoist freeze-thaw cycling and deicers Concrete placed inthe spring or summer has an adequate drying periodConcrete placed in the fall season however often does notdry out enough before deicers are used This is especiallytrue of fall paving cured by membrane-forming com-pounds These membranes remain intact until worn off bytraffic thus adequate drying may not occur before theonset of winter Curing methods such as use of plasticsheets that allow drying at the completion of the curingperiod are preferable for fall paving on all projects wheredeicers will be used Concrete placed inthe fall should be allowed at least 30days for air drying after the moist-curingperiod The exact length of time for suf-ficient drying to take place may varywith climate and weather conditionsTreatment of Scaled Surfaces If sur-face scaling (an indication of an inade-

quate air-void system or poor finishingpractices) should develop during thefirst frost season or if the concrete is of poor quality a breathable surface treat-ment can be applied to the dry concreteto help protect it against further damageTreatment often consists of a penetratingsealer made with boiled linseed oil(ACPA 1996) breathable methacrylateor other materials Nonbreathable for-mulations should be avoided as they cancause delamination

134


Fig 8-9 Effect of entrained air and cement content (Type II) on performance ofconcrete specimens exposed to a sulfate soil Without entrained air thespecimens made with lesser amounts of cement deteriorated badly Specimensmade with the most cement and the lowest water-cement ratio were furtherimproved by air entrainment Specimens were 5 years old when photographed(Stanton 1948 and Lerch 1960 )

Without air With air

5

4

3

2

1

002 03025 04 045 05035

Water to cement ratio

A v e r a g e m a s s

l o s s k g m 2

10

08

06

04

02 A v e r a g e m a s s

l o s s l b f t 22

46

Air content


Fig 8-8 Measured mass loss of concrete after 40 cycles ofdeicer and frost exposure at various water to cement ratios(Pinto and Hover 2001 )

222 kgm 3

(375 lbyd 3)

306 kgm3

(515 lbyd 3)

392 kgm 3

(660 lbyd 3)

Cementcontent



135


1

2

3

4

5

6

657517376Cement content lbyd 3

390307223Cement content kgm 3

V i s u a l r a t i n g

Cementtype

I

I

II

II

V

V

Rating1 ndash no deterioration6 ndash failure

Air-entrained concreteNon-air-entrained concrete

150 x 150 x 760-mm (6 x 6 x 30-in)beams exposed for 11 years to soilcontaining approximately 10 sodium sulfate

Fig 8-10 Performance of a variety of air-entrained and non-air-entrained concretes exposed to sulfate soil Sulfateresistance is increased with the use of Types II and Vcements a higher cement content lower water-cementratio and air entrainment (Stark 1984 )

70

60

50

40

30

20

10

02 4 6 8 10 12 14

Air content percent

R e d u c t i o n

i n e x p a n s i o n a t o n e y e a r p e r c e n t

50 x 50 x 250-mm(2 x 2 x 10-in) mortar bars1 2 mortarwater to cement ratio = 04019 of the sand by masscontained reactive siliceousmagnesian limestone

Fig 8-11 Effect of air content on the reduction of expansiondue to alkali-silica reaction (Kretsinger 1949 )

35 5

3

428

21

050 055 060Water to cement ratio by mass

C o m p r e s s i v e s t r e n g t h

M P a


1 0 0 0 p s i

Air-entrained concreteCement Type IAge 28 days

Fig 8-12 Typical relationship between 28-day compressive

strength and water-cement ratio for a wide variety of air-entrained concretes using Type I cement

of coarse aggregate When the cement content and slumpare held constant air entrainment reduces the sand andwater requirements as illustrated in Fig 8-13 Thus air-entrained concretes can have lower water-cement ratiosthan non-air-entrained concretes this minimizes thereductions in strength that generally accompany airentrainment At constant water-cement ratios increases inair will proportionally reduce strength (Fig 8-14) Pintoand Hover (2001) found that for a decrease in strength of 10 MPa (1450 psi) resulting from a four percentage pointdecrease in air the water-cement ratio had to be decreased by 014 to maintain strength Some reductions in strengthmay be tolerable in view of other benefits of air such asimproved workability Reductions in strength becomemore significant in higher-strength mixes as illustrated inFig 8-15 In lower-cement-content harsh mixes strengthis generally increased by entrainment of air in properamounts due to the reduced water-cement ratio andimproved workability For moderate to high-strength con-crete each percentile of increase in entrained air reducesthe compressive strength about 2 to 9 (Cordon 1946Klieger 1952 Klieger 1956 Whiting and Nagi 1998 andPinto and Hover 2001 ) Actual strength varies and isaffected by the cement source admixtures and other con-crete ingredients

Attainment of high strength with air-entrained con-crete may be difficult at times Even though a reduction inmixing water is associated with air entrainment mixtureswith high cement contents require more mixing waterthan lower-cement-content mixtures hence the increasein strength expected from the additional cement is offsetsomewhat by the additional water Water reducers canoffset this effect



Workability

Entrained air improves the workability of concrete It isparticularly effective in lean (low cement content) mixesthat otherwise might be harsh and difficult to work In onestudy an air-entrained mixture made with natural aggre-gate 3 air and a 37-mm (1 1 frasl 2-in) slump had about thesame workability as a non-air-entrained concrete with 1air and a 75-mm (3-in) slump even though less cementwas required for the air-entrained mix (Cordon 1946)Workability of mixes with angular and poorly gradedaggregates is similarly improved

Because of improved workability with entrained airwater and sand content can be reduced significantly (Fig8-13) A volume of air-entrained concrete requires lesswater than an equal volume of non-air-entrained concreteof the same consistency and maximum size aggregateFreshly mixed concrete containing entrained air is cohe-sive looks and feels fatty or workable and can usually behandled with ease on the other hand high air contentscan make a mixture sticky and more difficult to finishEntrained air also reduces segregation and bleeding infreshly mixed and placed concrete

AIR-ENTRAINING MATERIALS

The entrainment of air in concrete can be accomplished byadding an air-entraining admixture at the mixer by usingan air-entraining cement or by a combination of these

136


10 2 3 4 5 6 7 8 9

40

30

20

10

0

5

4

3

2

1

6

Air content percent

C o m p r e s s i v e s t r e n g t

h M P a


1 0 0 0 p s i

364 kg m 3 (613 lbyd 3)

308 kgm 3 (519 lbyd 3)

252kgm 3 (425 lbyd 3)

150 x 300-mm (6 x 12-in) cylinders

Fig 8-15 Relationship between air content and 28-daycompressive strength for concrete at three cement con-tents Water content was reduced with increased air contentto maintain a constant slump (Cordon 1946 )

70 10

8

6

60

50

400 1 2 3 4 5 6 7

Air content percent

C o m p r e s s i v e s t r e n g t h a t 9 0

d a y s M P a

C o m p r e s s

i v e s t r e n g t h a t 9 0

d a y s 1 0 0 0 p s i

025030035040045050


Fig 8-14 Relationship between compressive strength at 90days and air content (Pinto and Hover 2001 )

60

40

30

20

10

0

75

50

25

0

100

80

60

40

20

0

20

15

10

05

0

250 350 500Cement content kgm 3

Cement content lbyd 3

W a t e r r e d u c t i o n

k g m 3


l b y d 3

S a n d r e d u c t i o n

f t 3 y d 3


d m 3 m 3

300

400 600 800

400 400


400 600 800


300 400 400

8 air

6

8 air

6

4

2

4

2

Fig 8-13 Reduction of water and sand content obtained atvarious levels of air and cement contents (Gilkey 1958 )



methods Regardless of the method used adequate con-trol and monitoring is required to ensure the proper aircontent at all times

Numerous commercial air-entraining admixturesmanufactured from a variety of materials are availableMost air-entraining admixtures consist of one or more of the following materials wood resin (Vinsol resin) sul-fonated hydrocarbons fatty and resinous acids and syn-thetic materials Chemical descriptions and performancecharacteristics of common air-entraining agents are shownin Table 8-3 Air-entraining admixtures are usually liquidsand should not be allowed to freeze Admixtures addedat the mixer should conform to ASTM C 260 (AASHTOM 154)

Air-entraining cements comply with ASTM C 150 andC 595 (AASHTO M 85 and M 240) To produce such ce-ments air-entraining additions conforming to ASTM C 226are interground with the cement clinker during manufac-ture Air-entraining cements generally provide an ade-quate amount of entrained air to meet most job conditions

however a specified air content may not necessarily beobtained in the concrete If an insufficient volume of air isentrained it may also be necessary to add an air-entraining admixture at the mixer

Each method of entraining air has certain advantagesOn jobs where careful control is not practical air-entraining cements are especially useful to ensure that asignificant portion of the required air content will always be obtained They eliminate the possibility of human ormechanical error that can occur when adding an admix-ture during batching With air-entraining admixtures the

volume of entrained air can be readily adjusted to meet job conditions by changing the amount of admixtureadded at the mixer

Variations in air content can be expected with varia-tions in aggregate proportions and gradation mixing timetemperature and slump The order of batching and mixingconcrete ingredients when using an air-entraining admix-ture has a significant influence on the amount of airentrained therefore consistency in batching is needed tomaintain adequate control

When entrained air is excessive it can be reduced byusing one of the following defoaming (air-detraining)agents tributyl phosphate dibutyl phthalate octyl alcoholwater-insoluble esters of carbonic acid and boric acid andsilicones Only the smallest possible dosage of defoamingagent should be used to reduce the air content to the speci-fied limit An excessive amount might have adverse effectson concrete properties (Whiting and Stark 1983 )

FACTORS AFFECTING AIR CONTENTCement

As cement content increases the air content decreases for aset dosage of air-entraining admixture per unit of cementwithin the normal range of cement contents (Fig 8-16) Ingoing from 240 to 360 kilogram of cement per cubic meter(400 to 600 lb of cement per cubic yard) the dosage ratemay have to be doubled to maintain a constant air contentHowever studies indicate that when this is done the air-void spacing factor generally decreases with an increase in

137


Classification Chemical description Notes and performance characteristicsWood derived acid salts Alkali or alkanolamine salt ofVinsol reg resin A mixture of tricyclic acids Quick air generation Minor air gain with initial mixing Air

phenolics and terpenes loss with prolonged mixing Mid-sized air bubbles formedCompatible with most other admixtures

Wood rosin Tricyclic acids-major component Same as aboveTricyclic acids-minor component

Tall oil Fatty acids-major component Slower air generation Air may increase with prolongedTricyclic acids-minor component mixing Smallest air bubbles of all agents Compatible

with most other admixturesVegetable oil acids Coconut fatty acids alkanolamine salt Slower air generation than wood rosins Moderate air

loss with mixing Coarser air bubbles relative to woodrosins Compatible with most other admixtures

Synthetic detergents Alkyl-aryl sulfonates and sulfates Quick air generation Minor air loss with mixing Coarser(eg sodium bubbles May be incompatible with some HRWR Alsododecylbenzenesulfonate) applicable to cellular concretes

Synthetic workability aids Alkyl-aryl ethoxylates Primarily used in masonry mortarsMiscellaneous Alkali-alkanolamine acid salts All these are rarely used as concrete air-entraining

of lignosulfonate agents in current practiceOxygenated petroleum residuesProteinaceous materialsAnimal tallows

Table 8-3 Classification and Performance Characteristics of Common Air-Entraining Admixtures(Whiting and Nagi 1998 )



the amount of fine aggregate causes more air to beentrained for a given amount of air-entraining cement oradmixture (more air is also entrapped in non-air-entrained concrete)

Fine-aggregate particles passing the 600 microm to 150 microm(No 30 to No 100) sieves entrap more air than either veryfine or coarser particles Appreciable amounts of materialpassing the 150 microm (No 100) sieve will result in a signifi-cant reduction of entrained air

Fine aggregates from different sources may entrapdifferent amounts of air even though they have identicalgradations This may be due to differences in shape andsurface texture or contamination by organic materials

Mixing Water and Slump

An increase in the mixing water makes more water avail-able for the generation of air bubbles thereby increasingthe air content as slumps increase up to about 150 or175 mm (6 or 7 inches) An increase in the water-cementratio from 04 to 10 can increase the air content by fourpercentage points A portion of the air increase is due tothe relationship between slump and air content Air con-tent increases with slump even when the water-cementratio is held constant The spacing factor iquest of the air-voidsystem also increases that is the voids become coarser athigher water-cement ratios thereby reducing concretefreeze-thaw durability (Stark 1986)

The addition of 5 kg of water per cubic meter (84 lbsof water per cubic yard) of concrete can increase the slump by 25 mm (one inch) A 25-mm (1-in) increase in slump in-creases the air content by approximately one-half to one

cement content and for a given air content the specific sur-face increases thus improving durability

An increase in cement fineness will result in adecrease in the amount of air entrained Type III cement avery finely ground material may require twice as muchair-entraining agent as a Type I cement of normal fineness

High-alkali cements may entrain more air than lowalkali cements with the same amount of air-entrainingmaterial A low-alkali cement may require 20 to 40(occasionally up to 70) more air-entraining agent than ahigh-alkali cement to achieve an equivalent air contentPrecautions are therefore necessary when using more thanone cement source in a batch plant to ensure that properadmixture requirements are determined for each cement(Greening 1967)

Coarse Aggregate

The size of coarse aggregate has a pronounced effect onthe air content of both air-entrained and non-air-entrainedconcrete as shown in Fig 8-16 There is little change in aircontent when the size of aggregate is increased above375 mm (11 frasl 2 in)

Fine Aggregate

The fine-aggregate content of a mixture affects the per-centage of entrained air As shown in Fig 8-17 increasing

138


A i r c o n t e n t p e r c e n t

6

5

4

3

2

1

020 24 28 32 36 40 44

Air-entrained concrete

Non-air-entrained concrete(entrapped air only)

Cement Type I ndash 280 to 335 kgm 3 (470 to 565 lbyd 3)Slump 80 to 100 mm (3 to 5 in)

Fine aggregate content percent of total aggregate

Fig 8-17 Relationship between percentage of fine aggre-gate and air content of concrete PCA Major Series 336


12

10

8

6

4

2

095 125 190 250 375 50 63

38 12 34 1 1 1 2 2 21 2

Maximum-size aggregate mm

Maximum-size aggregate in

222 kgm 3 (375 lbyd 3)

306 kgm 3 (515 lbyd 3)

388 kgm 3 (655 lbyd 3)

222 kgm 3 (375 lbyd 3)

388 kgm 3 (655 lbyd 3)

Air-entrained concreteNon-air-entrained concrete(entrapped air only)Cement Type ISlump 50 to 80 mm (2 to 3 in)

Fig 8-16 Relationship between aggregate size cementcontent and air content of concrete The air-entrainingadmixture dosage per unit of cement was constant for air-entrained concrete PCA Major Series 336



P o r t l a n d c e m e n t

S u

p p l e m e n t a r y c e m e n t i t i o u

s m a t e r i a l s

C h e m i c a l a d m i x t u r e s

A g g r e g a t e

percentage point for concretes with a low-to-moderateslump and constant air-entraining admixture dosageHowever this approximation is greatly affected by con-crete temperature slump and the type and amount of cement and admixtures present in the concrete A low-slump concrete with a high dosage of water-reducing andair-entraining admixtures can undergo large increases in

slump and air content with a small addition of water Onthe other hand a very fluid concrete mixture with a 200 to250-mm (8 to 10-in) slump may lose air with the additionof water Refer to Tables 8-4 and 8-5 for more information

The mixing water used may also affect air contentAlgae-contaminated water increases air content Highlyalkaline wash water from truck mixers can affect air con-

139


CharacteristicMaterial Effects Guidance

Alkali content Air content increases with increase Changes in alkali content or cement source requirein cement alkali level that air-entraining agent dosage be adjusted

Less air-entraining agent dosage Decrease dosage as much as 40 for high-alkalineeded for high-alkali cements cements

Air-void system may be more unstablewith some combinations of alkali leveland air-entraining agent used

Fineness Decrease in air content with increased Use up to 100 more air-entraining admixture forfineness of cement very fine (Type III) cements Adjust admixture if

cement source or fineness changes

Cement content in Decrease in air content with increase Increase air-entraining admixture dosage rate asmixture in cement content cement content increases

Smaller and greater number of voidswith increased cement content

Contaminants Air content may be altered by contam- Verify that cement meets ASTM C 150 (AASHTO M 85)ination of cement with finish mill oil requirements on air content of test mortar

Fly ash Air content decreases with increase in Changes in LOI or fly ash source require that air-loss on ignition (carbon content) entraining admixture dosage be adjusted

Perform ldquofoam index rdquo test to estimate increase indosage

Air-void system may be more unstable Prepare trial mixes and evaluate air-void systemswith some combinations of fly ash

cementair-entraining agentsGround granulated Decrease in air content with increased Use up to 100 more air-entraining admixture forblast-furnace slag fineness of GGBFS finely ground slagsSilica fume Decrease in air content with increase Increase air-entraining admixture dosage up to 100

in silica fume content for fume contents up to 10Metakaolin No apparent effect Adjust air-entraining admixture dosage if needed

Water reducers Air content increases with increases in Reduce dosage of air-entraining admixturedosage of lignin-based materials

Select formulations containing air-detraining agentsSpacing factors may increase when Prepare trial mixes and evaluate air-void systemswater-reducers used

Retarders Effects similar to water-reducers Adjust air-entraining admixture dosageAccelerators Minor effects on air content No adjustments normally needed

High-range water Moderate increase in air content when Only slight adjustments neededreducers (Plasticizers) formulated with lignosulfonate

Spacing factors increase No significant effect on durability

Maximum size Air content requirement decreases Decrease air contentwith increase in maximum sizeLittle increase over 375 mm (1 1 frasl 2 in)maximum size aggregate

Sand-to-total aggregate Air content increases with increased Decrease air-entraining admixture dosage forratio sand content mixtures having higher sand contentsSand grading Middle fractions of sand promote air- Monitor gradation and adjust air-entraining admixture

entrainment dosage accordingly

Table 8-4 Effect of Mixture Design and Concrete Constituents on Control of Air Content in Concrete



140


T r a n s p o r t a n d d e l i v e r y

P r o d u c t

i o n p r o c e d u

r e s

ProcedureVariable Effects GuidanceBatching sequence Simultaneous batching lowers air Add air-entraining admixture with initial water or

content on sandCement-first raises air content

Mixer capacity Air increases as capacity is approached Run mixer close to full capacity Avoid overloadingMixing time Central mixers air content increases Establish optimum mixing time for particular mixer

up to 90 sec of mixingTruck mixers air content increases Avoid overmixingwith mixingShort mixing periods (30 seconds) Establish optimum mixing time (about 60 seconds)reduce air content and adversely affectair-void system

Mixing speed Air content gradually increases up to Follow truck mixer manufacturer recommendationsapprox 20 rpmAir may decrease at higher mixing Maintain blades and clean truck mixerspeeds

Admixture metering Accuracy and reliability of metering Avoid manual-dispensing or gravity-feed systemssystem will affect uniformity of air and timers Positive-displacement pumps interlockedcontent with batching system are preferred

Transport and delivery Some air (1 to 2) normally lost Normal retempering with water to restore slump willduring transport restore airLoss of air in nonagitating equipment If necessary retemper with air-entraining admixtureis slightly higher to restore air

Dramatic loss in air may be due to factors other thantransportHaul time and agitation Long hauls even without agitation Optimize delivery schedules Maintain concrete

reduce air especially in hot weather temperature in recommended rangeRetempering Regains some of the lost air Retemper only enough to restore workability Avoid

Does not usually affect the air-void addition of excess watersystem Higher admixture dosage is needed for jobsiteRetempering with air-entraining ad- admixture additionsmixtures restores the air-void system

Table 8-5 Effect of Production Procedures Construction Practices and Environment on Control of AirContent in Concrete

M i x w

a t e r a n d s l u m p

CharacteristicMaterial Effects GuidanceWater chemistry Very hard water reduces air content Increase air entrainer dosage

Batching of admixture into concrete Avoid batching into wash waterwash water decreases airAlgae growth may increase air

Water-to-cement ratio Air content increases with increased Decrease air-entraining admixture dosage as waterwater to cement ratio to cement ratio increasesSlump Air increases with slumps up to about Adjust air-entraining admixture dosages for slump

150 mm (6 in)Air decreases with very high slumps Avoid addition of water to achieve high-slump con-

creteDifficult to entrain air in low-slump Use additional air-entraining admixture up to tenconcretes times normal dosage

Table 8-4 Effect of Mixture Design and Concrete Constituents on Control of Air Content in Concrete(Continued)



tents The effect of water hardness in most municipalwater supplies is generally insignificant however veryhard water from wells as used in rural communities maydecrease the air content in concrete

Slump and VibrationThe effect of slump and vibration on the air content of con-crete is shown in Fig 8-18 For a constant amount of air-entraining admixture air content increases as slumpincreases up to about 150 or 175 mm (6 or 7 inches) then it begins to decrease with further increases in slump At allslumps however even 15 seconds of vibration (the ACI 309limit) will cause a considerable reduction in air contentProlonged vibration of concrete should be avoided

The greater the slump air content and vibration timethe larger the percentage of reduction in air contentduring vibration (Fig 8-18) However if vibration is prop-

erly applied little of the intentionally entrained air is lostThe air lost during handling and moderate vibration con-sists mostly of the larger bubbles that are usually undesir-able from the standpoint of strength While the averagesize of the air voids is reduced the air-void spacing factorremains relatively constant

Internal vibrators reduce air content more thanexternal vibrators The air loss due to vibration increasesas the volume of concrete is reduced or the vibration fre-quency is significantly increased Lower vibration fre-quencies (8000 vpm) have less effect on spacing factors

141



90

80

70

60

50

40

30

20

100 10 20 30 40 50

25-mm (1-in) immersion-type vibratorAll mixes contained same amountof air-entraining admixture

137-mm (54-in) slump

96-mm (38-in) slump

46-mm (18-in) slump

Vibration time seconds

Fig 8-18 Relationship between slump duration of vibra-tion and air content of concrete (Brewster 1949 )

P l a c e m e n t t e c h n i q u

e s

F i n i s h i n g a n d e n v

i r o n m e n t

ProcedureVariable Effects GuidanceBelt conveyors Reduces air content by an average Avoid long conveyed distance if possible

of 1 Reduce the free-falling effect at the end of conveyorPumping Reduction in air content ranges from Use of proper mix design provides a stable air-void

2 to 3 system

Does not significantly affect air-void Avoid high slump high air content concretesystem Keep pumping pressure as low as possibleMinimum effect on freeze-thaw Use loop in descending pump lineresistance

Shotcrete Generally reduces air content in wet- Air content of mix should be at high end of targetprocess shotcrete zone

Internal vibration Air content decreases under prolonged Do not overvibrate Avoid high-frequency vibratorsvibration or at high frequencies (greater than 10000 vpm) Avoid multiple passes of

vibratory screedsProper vibration does not influence the Closely spaced vibrator insertion is recommendedair-void system for better consolidation

Finishing Air content reduced in surface layer by Avoid finishing with bleed water still on surfaceexcessive finishing Avoid overfinishing Do not sprinkle water on surface

prior to finishing Do not steel trowel exterior slabsTemperature Air content decreases with increase in Increase air-entraining admixture dosage as temper-

temperature ature increasesChanges in temperature do not signifi-cantly affect spacing factors

Table 8-5 Effect of Production Procedures Construction Practices and Environment on Control of AirContent in Concrete (Continued)



concrete increases particularly as slump is increased Thiseffect is especially important during hot-weather con-creting when the concrete might be quite warm Adecrease in air content can be offset when necessary byincreasing the quantity of air-entraining admixture

In cold-weather concreting the air-entraining admix-ture may lose some of its effectiveness if hot mix water isused during batching To offset this loss such admixturesshould be added to the batch after the temperature of theconcrete ingredients have equalized

Although increased concrete temperature duringmixing generally reduces air volume the spacing factorand specific surface are only slightly affected

Supplementary Cementitious Materials

The effect of fly ash on the required dosage of air-entrainingadmixtures can range from no effect to an increase in dosageof up to five times the normal amount (Gebler and Klieger1986) Large quantities of slag and silica fume can double the

dosage of air-entraining admixtures (Whiting and Nagi 1998 )

Admixtures and Coloring Agents

Coloring agents such as carbon black usually decrease theamount of air entrained for a given amount of admixtureThis is especially true for coloring materials withincreasing percentages of carbon (Taylor 1948)

Water-reducing and set-retarding admixtures gener-ally increase the efficiency of air-entraining admixtures by50 to 100 therefore when these are used less air-entraining admixture will usually give the desired air con-tent Also the time of addition of these admixtures intothe mix affects the amount of entrained air delayed addi-tions generally increasing air content

Set retarders may increase the air-void spacing in con-crete Some water-reducing or set-retarding admixtures arenot compatible with some air-entraining admixtures If they are added together to the mixing water before beingdispensed into the mixer a precipitate may form This willsettle out and result in large reductions in entrained airThe fact that some individual admixtures interact in thismanner does not mean that they will not be fully effectiveif dispensed separately into a batch of concrete

Superplasticizers (high-range water reducers) may

increase or decrease the air content of a concrete mixture based on the admixturersquos chemical formulation and theslump of the concrete Naphthalene-based superplasti-cizers tend to increase the air content while melamine- based materials may decrease or have little effect on aircontent The normal air loss in flowing concrete duringmixing and transport is about 2 to 4 percentage points(Whiting and Dziedzic 1992 )

Superplasticizers also affect the air-void system of hardened concrete by increasing the general size of theentrained air voids This results in a higher-than-normal

and air contents than high vibration frequencies (14000vpm) High frequencies can significantly increase spacingfactors and decrease air contents after 20 seconds of vibra-tion (Brewster 1949 and Stark 1986)

For pavements specified air contents and uniform airvoid distributions can be achieved by operating withinpaving machine speeds of 122 to 188 meters per minute(4 to 6 feet per minute) and with vibrator frequencies of 5000 to 8000 vibrations per minute The most uniformdistribution of air voids throughout the depth of concretein and out of the vibrator trails is obtained with the combination of a vibrator frequency of approximately 5000 vibrations per minute and a slipform paving machineforward track speeds of 122 meters per minute (4 feet perminute) Higher frequencies of speeds singularly or incombination can result in discontinuities and lack of re-quired air content in the upper portion of the concretepavement This in turn provides a greater opportunity forwater and salt to enter the pavement and reduce the durability and life of the pavement (Cable McDaniel

Schlorholtz Redmond and Rabe 2000 )

Concrete Temperature

Temperature of the concrete affects air content as shownin Fig 8-19 Less air is entrained as the temperature of the

142



7

6

5

4

3

2

1

0

50 60 70 80 90

10 15 20 25 30 355Concrete temperature deg C

Concrete temperature deg F

125-mm (5-in) slump

175-mm (7-in) slump

75-mm (3-in) slump

25-mm (1-in) slump

Cement 335 kgm 3 (565 lbyd 3)Aggregate 375-mm (1 1 2-in) max size

Fig 8-19 Relationship between temperature slump and aircontent of concrete PCA Major Series 336 and Lerch 1960



spacing factor occasionally higher than what may be con-sidered desirable for freeze-thaw durability Howevertests on superplasticized concrete with slightly higherspacing factors have indicated that superplasticized con-cretes have good freeze-thaw durability This may be dueto the reduced water-cement ratio often associated withsuperplasticized concretes

A small quantity of calcium chloride is sometimesused in cold weather to accelerate the hardening of con-crete It can be used successfully with air-entrainingadmixtures if it is added separately in solution form to themix water Calcium chloride will slightly increase air con-tent However if calcium chloride comes in direct contactwith some air-entraining admixtures a chemical reactioncan take place that makes the admixture less effectiveNonchloride accelerators may increase or decrease aircontent depending upon the individual chemistry of theadmixture but they generally have little effect onair content

Mixing Action

Mixing action is one of the most important factors in theproduction of entrained air in concrete Uniform distribu-tion of entrained air voids is essential to produce scale-resistant concrete nonuniformity might result frominadequate dispersion of the entrained air during shortmixing periods In production of ready mixed concrete itis especially important that adequate and consistentmixing be maintained at all times

The amount of entrained air varies with the type andcondition of the mixer the amount of concrete beingmixed and the rate and duration of mixing The amountof air entrained in a given mixture will decrease appre-ciably as the mixer blades become worn or if hardenedconcrete is allowed to accumulate in the drum or on the blades Because of differences in mixing action and timeconcretes made in a stationary mixer and those made in atransit mixer may differ significantly in amounts of airentrained The air content may increase or decrease whenthe size of the batch departs significantly from the ratedcapacity of the mixer Little air is entrained in very small batches in a large mixer however the air content increasesas the mixer capacity is approached

Fig 8-20 shows the effect of mixing speed and dura-

tion of mixing on the air content of freshly mixed con-cretes made in a transit mixer Generally more air isentrained as the speed of mixing is increased up to about20 rpm beyond which air entrainment decreases In thetests from which the data in Fig 8-20 were derived the aircontent reached an upper limit during mixing and agradual decrease in air content occurred with prolongedmixing Mixing time and speed will have different effectson the air content of different mixes Significant amountsof air can be lost during mixing with certain mixtures andtypes of mixing equipment

Fig 8-21 shows the effect of continued mixer agita-tion on air content The changes in air content with pro-longed agitation can be explained by the relationship between slump and air content For high-slump con-cretes the air content increases with continued agitationas the slump decreases to about 150 or 175 mm (6 or 7 in)Prolonged agitation will decrease slump further anddecrease air content For initial slumps lower than150 mm (6 in) both the air content and slump decreasewith continued agitation When concrete is retempered(the addition of water and remixing to restore originalslump) the air content is increased however after4 hours retempering is ineffective in increasing air con-tent Prolonged mixing or agitation of concrete is accom-panied by a progressive reduction in slump

143



5

4

3

2

1

0100 20 30 40 50 60

11 rpm

4 rpm

Cement 305 kgm 3 (510 lbyd 3)Mixer 4 m3 (6 yd3) transit mixerMixing time starts after charging completed

Mixing time minutes

Fig 8-20 Relationship between mixing time and air contentof concrete PCA Major Series 336


8

7

6

5

410 20 30 40 50 60 70 80 90

100-mm (4-in) initial slump


Agitating speeds 2 or 4 rpmTransit mixer 45 and 61 m 3 (6 and 8 yd 3)Initial mixing 70 rev at 10 rpm

Agitating time minutes (after initial mixing)

Fig 8-21 Relationship between agitating time air contentand slump of concrete PCA Major Series 336



When aggregates larger than 50 mm (2 in) are usedthey should be removed by hand and the effect of their removal calculated in arriving at the total aircontent

3 Gravimetric method (ASTM C 138 or AASHTO T 121Standard Test Method for Unit Weight Yield and AirContent [Gravimetric] of Concrete)mdashrequires accurateknowledge of relative density and absolute volumesof concrete ingredients

4 Chace air indicator (AASHTO T 199 Standard Methodof Test for Air Content of Freshly Mixed Concrete by theChace Indicator)mdasha very simple and inexpensive wayto check the approximate air content of freshly mixedconcrete This pocket-size device tests a mortar samplefrom the concrete This test is not a substitute however for the more accurate pressure volumetric and gravi-metric methods

The foam-index test can be used to measure the rela-tive air-entraining admixture requirement for concretescontaining fly ash-cement combinations (Gebler andKlieger 1983)

Transporting and Handling

Generally some airmdashapproximately 1 to 2 percentagepointsmdashis lost during transportation of concrete from themixer to the jobsite The stability of the air content duringtransport is influenced by several variables including con-crete ingredients haul time amount of agitation or vibra-tion during transport temperature slump and amount of retempering

Once at the jobsite the concrete air content remainsessentially constant during handling by chute dischargewheelbarrow power buggy and shovel However con-crete pumping crane and bucket and conveyor-belt han-dling can cause some loss of air especially withhigh-air-content mixtures Pumping concrete can cause aloss of up to 3 percentage points of air (Whiting and Nagi1998)

Finishing

Proper screeding floating and general finishing practicesshould not affect the air content McNeal and Gay (1996)and Falconi (1996) demonstrated that the sequence andtiming of finishing and curing operations are critical to sur-face durability Overfinishing (excessive finishing) mayreduce the amount of entrained air in the surface region of slabsmdashthus making the concrete surface vulnerable toscaling However as shown in Fig 8-22 early finishingdoes not necessarily affect scale resistance unless bleedwater is present (Pinto and Hover 2001 ) Concrete to beexposed to deicers should not be steel troweled

TESTS FOR AIR CONTENT

Four methods for determining the air content of freshlymixed concrete are available Although they measure onlytotal air volume and not air-void characteristics it has been shown by laboratory tests that these methods areindicative of the adequacy of the air-void system

Acceptance tests for air content of freshly mixed con-crete should be made regularly for routine control pur-poses Samples should be obtained and tested inaccordance with ASTM C 172 (AASHTO T 141)

Following are methods for determining the air con-tent of freshly mixed concrete

1 Pressure method (ASTM C 231 or AASHTO T 152Standard Test Method for Air Content of Freshly MixedConcrete by the Pressure Method)mdashpractical for field-testing all concretes except those made with highlyporous and lightweight aggregates

2 Volumetric method (ASTM C 173 or AASHTO T 196Standard Test Method for Air Content of Freshly MixedConcrete by the Volumetric Method)mdashpractical for field-testing all concretes but particularly useful for con-cretes made with lightweight and porous aggregates

144


5

3

4

2

1

0

Water-to-cement ratio


050 045 040 035 030 025

Time offinishing

earlyon-time

Bleed water

3

4

5

2

1

0



050 045 040 035 030 025

Time offinishing

earlyon-time

Fig 8-22 Effect of early finishingmdashmagnesium floating 20minutes after castingmdashon scale resistance for (top) 6 air-entrained concrete (bottom) non-air-entrained concrete



The air-void characteristics of hardened concrete can be determined by ASTM C 457 methods This test is usedto determine void spacing factor specific surface of voidsand number of voids per length of traverse

Air-Void Analysis of Fresh Concrete

The conventional methods for analyzing air in fresh con-crete such as the pressure method noted above measurethe total air content only consequently they provide noinformation about the parameters that determine thequality of the air-void system These parametersmdashthe sizeand number of voids and spacing between themmdashcan bemeasured on polished samples of hardened concrete(ASTM C 457) but the result of such analysis will only beavailable several days after the concrete has hardenedTherefore test equipment called an air-void analyzer(AVA) has been developed to determine the standardASTM C 457 air-void parameters in fresh samples of air-entrained concrete (Fig 8-23) The test apparatus deter-mines the volume and size distributions of entrained airvoids thus an estimation of the spacing factor specificsurface and total amount of entrained air can be made

In this test method air bubbles from a sample of freshconcrete rise through a viscous liquid enter a column of water above it then rise through the water and collectunder a submerged buoyancy recorder (Fig 8-24) The vis-cous liquid retains the original bubble sizes Large bubbles

rise faster than small ones through the liquids The changein buoyancy is recorded as a function of time and can berelated to the number of bubbles of different size

Fresh concrete samples can be taken at the ready mixplant and on the jobsite Testing concrete before and afterplacement into forms can verify how the applied methodsof transporting placing and consolidation affect the air-void system Since the samples are taken on fresh con-crete the air content and air-void system can be adjustedduring production

Currently no standard exists for this method TheAVA was not developed for measuring the total air-con-tent of concrete and because of the small sample size maynot give accurate results for this quantity However thisdoes not mean the AVA is not useful as a method forassessing the quality of the air-void system it gives goodresults in conjunction with traditional methods for meas-uring air content (Aarre 1998)

RECOMMENDED AIR CONTENTS

The amount of air to be used in air-entrained concretedepends on a number of factors (1) type of structure(2) climatic conditions (3) number of freeze-thaw cycles(4) extent of exposure to deicers and (5) the design life of the structure

The ACI 318 building code states that concrete thatwill be exposed to moist freezing and thawing or deicerchemicals shall be air entrained with the target air contentof Table 8-6 for severe exposure Furthermore the waterto cementitious materials ratio should not exceed 045ACI 318 allows a one percentage point reduction in targetair contents for concretes with strengths over 34 MPa(5000 psi) and presumably very low water-cement ratios

145

Chapter 8 x Air-Entrained Concrete

Fig 8-23 Equipment for the air-void analyzer (67961)

Fig 8-24 Air bubbles rising through liquids in column(67962)



ACI 318 limits the amounts of pozzolans and slagmdash10 for silica fume 25 for fly ash 50 for slagmdashas partof the cementitious material for deicer exposuresHowever mix designers should consult local practices asto allowable dosages to prevent frost and deicer damageCombinations of materials without historical record can be analyzed using ASTM C 666 (AASHTO T 161) andASTM C 672 Pinto and Hover (2001) evaluate the appli-cability of the ACI 318 requirements for frost resistance of portland cement concrete mixtures with water to cementratios from 025 to 050 Fig 8-26 illustrates the effect of increased air content with respect to aggregate size onreducing expansion due to saturated freezing andthawing it emphasizes the need to follow the require-ments of Table 8-6 for severe exposure

When entrained air is not required for protectionagainst freeze-thaw cycles or deicers the target air con-tents for mild exposure given in Table 8-6 can be usedHigher air contents can also be used as long as the designstrength is achieved As noted earlier entrained air helps

to reduce bleeding and segregation and can improve theworkability of concreteMore information on air-entrained concrete can be

found in Whiting and Nagi (1998)

Fig 8-25 illustrates how deicer-scaling resistance isimpacted by air content and low water to portland cementratios (strengths ranging from 40 to 59 MPa [5800 to 8600psi]) This illustrates that concretes with very low water toportland cement ratios are more frost and deicer resistanthence they may allow use of lower air contents This rela-tionship (Fig 8-25) was not established for concretes con-

taining supplementary cementitious materials as theywere not studied (Pinto and Hover 2001 )

146


Nominal maximum Air content percent

size aggregate Severe Moderate Mildmm (in) exposure exposure dagger exposure daggerdagger

lt95 ( 3 frasl 8) 9 7 595 ( 3 frasl 8) 71 frasl 2 6 4 1 frasl 2

125 ( 1 frasl 2) 7 51 frasl 2 4190 ( 3 frasl 4) 6 5 3 1 frasl 2

250 (1) 6 4 1 frasl 2 3375 (1 1 frasl 2) 51 frasl 2 41 frasl 2 21 frasl 2

50 (2) Dagger 5 4 275 (3) Dagger 41 frasl 2 31 frasl 2 11 frasl 2

Table 8-6 Recommended Total Target Air Contentfor Concrete

Project specifications often allow the air content of the concrete to bewithin -1 to +2 percentage points of the table target values

Concrete exposed to wet-freeze-thaw conditions deicers or otheraggressive agents

dagger Concrete exposed to freezing but not continually moist and not incontact with deicers or aggressive chemicals

daggerdagger Concrete not exposed to freezing conditions deicers or aggressiveagents

Dagger These air contents apply to the total mix as for the preceding aggre-gate sizes When testing these concretes however aggregate largerthan 375 mm (1 1 frasl 2 in) is removed by handpicking or sieving and aircontent is determined on the minus 375 mm (1 1 frasl 2 in) fraction of mix(Tolerance on air content as delivered applies to this value)

30

20

10

00

06

04

02

00

1 32 5 6 74Total air content percent


l o s s a t 4 0 c y c l e s

k g m 2



l b f t 2

040035030025

Water-to-cement ratioASTM C 672

Fig 8-25 Measured mass loss after 40 cycles of deicersand freeze-thaw exposures at various air contents (Pintoand Hover 2001 )

020

018

016

014

012

010

008

006

004

002

00 2 4 6 8 10 12 14

E x p a n s i o n p e

r c e n t

Freeze ndash thaw cycles 300Specimens 75 x 75 x 280-mm

(3 x 3 x 11 1 4-in)concrete prisms

Cement Type I 310 kgm 3

(517 lbyd 3)Slump 50 to 75 mm (2 to 3 in)

Maximum-size aggregate95-mm ( 3 8-in)190-mm ( 3 4-in)375-mm (1 1 2-in)

Air content percent

Fig 8-26 Relationship between air content and expansionof concrete test specimens during 300 cycles of freezingand thawing for various maximum aggregate sizes Smalleraggregate sizes require more air (Klieger 1952 )



REFERENCES

Aarre Tine ldquoAir-Void Analyzerrdquo Concrete TechnologyToday PL981 Portland Cement Association httpwwwportcementorgpdf_filesPL981pdf April 1998 page 4ACI Committee 201 Guide to Durable ConcreteACI 2012R-92 reapproved 1997 ACI Committee 201 Report Amer-ican Concrete Institute Farmington Hills Michigan 1992ACI Committee 308 Standard Practice for Curing ConcreteACI 308-92 reapproved 1997 ACI Committee 308 ReportAmerican Concrete Institute Farmington Hills Mich-igan 1992ACI Committee 309 Guide for Consolidation of ConcreteACI 309R-96 ACI Committee 309 Report American Con-crete Institute Farmington Hills Michigan 1996ACI Committee 318 Building Code Requirements for Struc-tural Concrete and CommentaryACI 318-02 ACI Commit-tee 318 Report American Concrete Institute FarmingtonHills Michigan 2002ACPA Scale-Resistant Concrete PavementsIS117 AmericanConcrete Pavement Association Skokie Illinois 1996ASCE ldquoEntrained Air Voids in Concrete Help Prevent SaltDamagerdquo Civil Engineering American Society of CivilEngineers New York May 1982Bates A A Woods H Tyler I L Verbeck G and PowersT C ldquoRigid-Type Pavementrdquo Association of HighwayOfficials of the North Atlantic States 28th AnnualConvention Proceedingspages 164 to 200 March 1952Bloem D L Air-Entrainment in Concrete National Sandand Gravel Association and National Ready MixedConcrete Association Silver Spring Maryland 1950Brewster R S Effect of Vibration Time upon Loss of Entrained Air from Concrete MixesMaterials Laboratories Report NoC-461 Research and Geology Division Bureau of Reclamation Denver November 25 1949Brown F P and Cady P D ldquoDeicer Scaling Mechanismsin Concreterdquo Durability of ConcreteACI SP-47 AmericanConcrete Institute Farmington Hills Michigan 1975pages 101 to 119Cable J K McDaniel L Schlorholtz S Redmond Dand Rabe K Evaluation of Vibrator Performance vs ConcreteConsolidation and Air Void System Serial No 2398 PortlandCement Associat ion httpwwwportcementorgpdf_filesSN2398pdf 2000 60 pages

Cody Rober D Cody Anita M Spry Paul G and GanGuo-Liang ldquoConcrete Deterioration by Deicing Salts AnExperimental Studyrdquo httpwwwctreiastateedupubssemisesqindexhtm Semisequicentennial TransportationConference ProceedingsCenter for Transportation Researchand Education Ames Iowa 1996Cordon W A Entrained AirmdashA Factor in the Design of Concrete MixesMaterials Laboratories Report No C-310Research and Geology Division Bureau of ReclamationDenver March 15 1946

Elfert R J Investigation of the Effect of Vibration Time on theBleeding Property of Concrete With and Without Entrained AirMaterials Laboratories Report No C-375 Research andGeology Division Bureau of Reclamation Denver January 26 1948Falconi M I Durability of Slag Cement Concretes Exposedto Freezing and Thawing in the Presence of DeicersMastersof Science Thesis Cornell University Ithaca New York306 pagesGebler S H and Klieger P Effect of Fly Ash on the Air-VoidStability of ConcreteResearch and Development BulletinRD085 Portland Cement Association httpwwwportcementorgpdf_filesRD085pdf 1983Gebler Steven H and Klieger Paul Effect of Fly Ash onDurability of Air-Entrained ConcreteResearch and Develop-ment Bulletin RD090 Portland Cement Association httpwwwportcementorgpdf_filesRD090pdf 1986Gilkey H J ldquoRe-Proportioning of Concrete Mixtures forAir Entrainmentrdquo Journal of the American Concrete InstituteProceedings vol 29 no 8 Farmington Hills Michigan

February 1958 pages 633 to 645Gonnerman H F ldquoDurability of Concrete in EngineeringStructuresrdquo Building Research Congress 1951collectedpapers Division No 2 Section D Building ResearchCongress London 1951 pages 92 to 104Gonnerman H F Tests of Concretes Containing Air-Entraining Portland Cements or Air-Entraining Materials Added to Batch at MixerResearch Department BulletinRX013 Portland Cement Association httpwwwportcementorgpdf_filesRX013pdf 1944Greening Nathan R Some Causes for Variation in Required Amount of Air-Entraining Agentin Portland Cement Mortars

Research Department Bulletin RX213 Portland CementAssociation httpwwwportcementorgpdf_filesRX213pdf 1967Klieger Paul Air-Entraining Admixtures Research Depart-ment Bulletin RX199 Portland Cement Associationhttpwwwportcementorgpdf_filesRX199pdf 1966Klieger Paul Extensions to the Long-Time Study of CementPerformance in Concrete Research Department BulletinRX157 Portland Cement Association 1963Klieger Paul Further Studies on the Effect of Entrained Air onStrength and Durability of Concrete with Various Sizes of AggregateResearch Department Bulletin RX077 PortlandCement Association httpwwwportcementorgpdf_filesRX077pdf 1956Klieger Paul Studies of the Effect of Entrained Air on theStrength and Durability of Concretes Made with Various Maximum Sizes of Aggregates Research DepartmentBulletin RX040 Portland Cement Association httpwwwportcementorgpdf_filesRX040pdf 1952Kretsinger D G Effect of Entrained Air on Expansion of Mortar Due to Alkali-Aggregate ReactionMaterials Labor-atories Report No C-425 Research and Geology DivisionU S Bureau of Reclamation Denver February 16 1949

147




South Dakota Department of Transportation I nvestigationof Low Compressive Strength of Concrete in Paving Precastand Structural Concrete Study SD 1998-03 PCA Serial No52002-17 Pierre South Dakota 2000Stanton Thomas E ldquoDurability of Concrete Exposed toSea Water and Alkali Soils-California Experiencerdquo Journalof the American Concrete lnstituteFarmington Hills Mich-igan May 1948Stark David C Effect of Vibration on the Air-System andFreeze-Thaw Durability of ConcreteResearch and Develop-ment Bulletin RD092 Portland Cement Association httpwwwportcementorgpdf_filesRD092pdf 1986Stark David Longtime Study of Concrete Durability inSulfate SoilsResearch and Development Bulletin RD086Portland Cement Association httpwwwportcementorgpdf_filesRD086pdf 1984Taylor Thomas G Effect of Carbon Black and Black Iron Oxideon Air Content and Durability of ConcreteResearch De-partment Bulletin RX023 Portland Cement Associationhttpwwwportcementorgpdf_filesRX023pdf 1948Verbeck G J Field and Laboratory Studies of the SulphateResistance of ConcreteResearch Department BulletinRX227 Portland Cement Association httpwwwportcementorgpdf_filesRX227pdf 1967Verbeck George and Klieger Paul Studies of ldquoSaltrdquo Scalingof ConcreteResearch Department Bulletin RX083 PortlandCement Association httpwwwportcementorgpdf_filesRX083pdf 1956Walker S and Bloem D L Design and Control of Air-Entrained Concrete Publication No 60 National ReadyMixed Concrete Association Silver Spring Maryland 1955Wang Kejin Monteiro Paulo J M Rubinsky Boris andArav Amir ldquoMicroscopic Study of Ice Propagation inConcreterdquo ACI Materials Journal July-August 1996 Amer-ican Concrete Institute Farmington Hills Michigan pages370 to 376Whiting D and Stark D Control of Air Content inConcrete National Cooperative Highway Research Pro-gram Report No 258 and Addendum TransportationResearch Board and National Research Council Wash-ington DC May 1983Whiting David A and Nagi Mohamad A Manual onControl of Air Content in Concrete EB116 National ReadyMixed Concrete Association and Portland CementAssociation 1998 42 pagesWhiting D and Dziedzic D Effects of Conventional and High-Range Water Reducers on Concrete PropertiesResearchand Development Bulletin RD107 Portland Cement Asso-ciation 1992 25 pagesWoods Hubert Observations on the Resistance of Concrete toFreezing and Thawing Research Department BulletinRX067 Portland Cement Association httpwwwportcementorgpdf_filesRX067pdf 1954

Lerch William Basic Principles of Air-Entrained ConcreteT-101 Portland Cement Association 1960McNeal F and Gay F ldquoSolutions to Scaling ConcreterdquoConcrete ConstructionAddison Illinois March 1996 pages250 to 255Menzel Carl A and Woods William M An Investigationof Bond Anchorage and Related Factors in Reinforced Concrete

Beams Research Department Bulletin RX042 PortlandCement Association 1952Mielenz R C Wokodoff V E Backstrom J E and FlackH L ldquoOrigin Evolution and Effects of the Air-VoidSystem in Concrete Part 1-Entrained Air in UnhardenedConcreterdquo July 1958 ldquoPart 2-Influence of Type andAmount of Air-Entraining Agentrdquo August 1958 ldquoPart 3-Influence of Water-Cement Ratio and CompactionrdquoSeptember 1958 and ldquoPart 4-The Air-Void System in JobConcreterdquo October 1958 Journal of the American ConcreteInstitute Farmington Hills Michigan 1958 Pigeon M and Pleau R Durability of Concrete in ColdClimatesEampFN Spon New York 1995 244 pagesPinto Roberto C A and Hover Kenneth C Frost andScaling Resistance of High-Strength ConcreteResearch andDevelopment Bulletin RD122 Portland Cement Asso-ciation 2001 70 pagesPowers T C ldquoThe Mechanism of Frost Action inConcreterdquo Stanton Walker Lecture Series on the MaterialsSciences Lecture No 3 National Sand and GravelAssociation and National Ready Mixed ConcreteAssociation Silver Spring Maryland 1965aPowers T C and Helmuth R A Theory of Volume Changesin Hardened Portland Cement Paste During FreezingResearchDepartment Bulletin RX046 Portland Cement Association

httpwwwportcementorgpdf_filesRX046pdf 1953Powers T C Basic Considerations Pertaining to Freezing andThawing Tests Research Department Bulletin RX058Portland Cement Association httpwwwportcementorgpdf_filesRX058pdf 1955Powers T C The Air Requirement of Frost-ResistantConcrete Research Department Bulletin RX033 PortlandCement Association httpwwwportcementorgpdf_filesRX033pdf 1949Powers T C Topics in Concrete Technologyhellip (3) MixturesContaining Intentionally Entrained Air (4) Characteristics of Air-Void Systems Research Department Bulletin RX174Portland Cement Association httpwwwportcementorgpdf_filesRX174pdf 1965Powers T C Void Spacing as a Basis for Producing Air-Entrained Concrete Research Department Bulletin RX049Portland Cement Association httpwwwportcementorgpdf_filesRX049pdf 1954Sayward John M Salt Action on ConcreteSpecial Report84-25 US Army Cold Regions Research and EngineeringLaboratory Hanover New Hampshire August 1984




ment in durability effected by air entrainment is shown inFigs 8-2 and 8-3

As the water in moist concrete freezes it producesosmotic and hydraulic pressures in the capillaries andpores of the cement paste and aggregate If the pressureexceeds the tensile strength of the paste or aggregate thecavity will dilate and rupture The accumulative effect of successive freeze-thaw cycles and disruption of paste and

130


Properties EffectAbrasion Little effect increased strength increases

abrasion resistanceAbsorption Little effectAlkali-silica reactivity Expansion decreases with increased air

Bleeding Reduced significantlyBond to steel DecreasedCompressive strength Reduced approximately 2 to 6 per per-

centage point increase in air harsh or leanmixes may gain strength

Creep Little effectDeicer scaling Significantly reducedDensity Decreases with increased airFatigue Little effectFinishability Reduced due to increased cohesion (sticki-

ness)Flexural strength Reduced approximately 2 to 4 per per-

centage point increase in airFreeze-thaw Significantly improved resistance to

resistance water-saturated freeze-thaw deteriorationHeat of hydration No significant effectModulus of elasticity Decreases with increased air

(static) approximately 720 to 1380 MPa (105000to 200000 psi) per percentage point of air

Permeability Little effect reduced water-cement ratioreduces permeability

Scaling Significantly reducedShrinkage (drying) Little effectSlump Increases with increased air approximately

25 mm (1 in) per 1 frasl 2 to 1 percentage pointincrease in air

Specific heat No effectSulfate resistance Significantly improved

Stickiness Increased cohesionmdashharder to finishTemperature of wet No effect

concreteThermal conductivity Decreases 1 to 3 per percentage point

increase in airThermal diffusivity Decreases about 16 per percentage

point increase in airWater demand of wet Decreases with increased air

concrete for equal approximately 3 to 6 kgm3 (5 to 10slump lbyd3) per percentage point of air

Watertightness Increases slightly reduced water-cementratio increases watertightness

Workability Increases with increased air

Air content percent

C y c l e s o f f r e e z i n g a n d

t h a w i n g

f o r 5 0

r e d u c t i o n i n d y n a m i c m o d u l u s o f e l a s t i c i t y

00

200

400

600

800

1000

1200

1400

1600

1800

2000

1 2 3 4 5 6

SymbolsNon-air-entrainedAir-entrained

Fig 8-2 Effect of entrained air on the resistance of concrete tofreezing and thawing in laboratory tests Concretes were madewith cements of different fineness and compositio n and withvarious cement contents and water-cement ratios (Bates andothers 1952 and Lerch 1960 )

Table 8-1 Effect of Entrained Air on ConcreteProperties

Note The table information may not apply to all situations

aggregate eventually cause significant expansion anddeterioration of the concrete Deterioration is visible in theform of cracking scaling and crumbling (Fig 8-3) Powers(1965) and Pigeon and Pleau (1995) extensively review themechanisms of frost action

Hydraulic pressures are caused by the 9 expansionof water upon freezing in this process growing ice crystalsdisplace unfrozen water If a capillary is above critical sat-uration (917 filled with water) hydraulic pressuresresult as freezing progresses At lower water contents nohydraulic pressure should exist

Osmotic pressures develop from differential concen-trations of alkali solutions in the paste (Powers 1965a) Aspure water freezes the alkali concentration increases inthe adjacent unfrozen water A high-alkali solutionthrough the mechanism of osmosis draws water fromlower-alkali solutions in the pores This osmotic transferof water continues until equilibrium in the fluidsrsquo alkaliconcentration is achieved Osmotic pressure is considereda minor factor if present at all in aggregate frost actionwhereas it may be dominant in certain cement pastesOsmotic pressures as described above are considered to be a major factor in ldquosalt scalingrdquo

Capillary ice (or any ice in large voids or cracks)draws water from pores to advance its growth Also sincemost pores in cement paste and some aggregates are too











131


















132


100

80

60

40

20

00 50 100 150 200 250 300 350


R e


i c m o d u

l u s

030035040045050


ASTM C 666


1100

1000

900

800

700

600

500

400

300

200

1001 2 3 4 5 6 7


S p a c i n g

f a c t o r m

i c r o m e t e r s


















133


20 04

03

02

01

18161412100806040200


C u m u l a

t i v e m a s s

l o s s k g m 2

C u m u l a

t i v e m a s s

l o s s l b f t 2

246

Air content



5

4

3

2

1

00 400200 800600


V i s u a

l r a t i n g









Sulfate Resistance





Strength






134




5

4

3

2

1

002 03025 04 045 05035



l o s s k g m 2

10

08

06

04


l o s s l b f t 22

46

Air content



222 kgm 3

(375 lbyd 3)

306 kgm3

(515 lbyd 3)

392 kgm 3

(660 lbyd 3)

Cementcontent



135


1

2

3

4

5

6




Cementtype

I

I

II

II

V

V





70

60

50

40

30

20

10

02 4 6 8 10 12 14

Air content percent

R e d u c t i o n




35 5

3

428

21



M P a


1 0 0 0 p s i








Workability





136


10 2 3 4 5 6 7 8 9

40

30

20

10

0

5

4

3

2

1

6

Air content percent


h M P a


1 0 0 0 p s i

364 kg m 3 (613 lbyd 3)

308 kgm 3 (519 lbyd 3)

252kgm 3 (425 lbyd 3)



70 10

8

6

60

50

400 1 2 3 4 5 6 7

Air content percent


d a y s M P a

C o m p r e s s


d a y s 1 0 0 0 p s i

025030035040045050



60

40

30

20

10

0

75

50

25

0

100

80

60

40

20

0

20

15

10

05

0




k g m 3


l b y d 3


f t 3 y d 3


d m 3 m 3

300

400 600 800

400 400


400 600 800


300 400 400

8 air

6

8 air

6

4

2

4

2














137























Coarse Aggregate


Fine Aggregate


138



6

5

4

3

2

1

020 24 28 32 36 40 44







12

10

8

6

4

2

095 125 190 250 375 50 63

38 12 34 1 1 1 2 2 21 2



222 kgm 3 (375 lbyd 3)

306 kgm 3 (515 lbyd 3)

388 kgm 3 (655 lbyd 3)

222 kgm 3 (375 lbyd 3)

388 kgm 3 (655 lbyd 3)






S u


s m a t e r i a l s


A g g r e g a t e




139



























140



P r o d u c t

i o n p r o c e d u

r e s












M i x w















141



90

80

70

60

50

40

30

20

100 10 20 30 40 50



96-mm (38-in) slump

46-mm (18-in) slump




e s


i r o n m e n t



2 to 3 system





























142



7

6

5

4

3

2

1

0

50 60 70 80 90



125-mm (5-in) slump

175-mm (7-in) slump

75-mm (3-in) slump

25-mm (1-in) slump







Mixing Action






143



5

4

3

2

1

0100 20 30 40 50 60

11 rpm

4 rpm


Mixing time minutes



8

7

6

5

410 20 30 40 50 60 70 80 90















Finishing








144


5

3

4

2

1

0



050 045 040 035 030 025

Time offinishing

earlyon-time

Bleed water

3

4

5

2

1

0



050 045 040 035 030 025

Time offinishing

earlyon-time














145












146














30

20

10

00

06

04

02

00




k g m 2



l b f t 2

040035030025



020

018

016

014

012

010

008

006

004

002

00 2 4 6 8 10 12 14


r c e n t






Air content percent




REFERENCES






147



















131


















132


100

80

60

40

20

00 50 100 150 200 250 300 350


R e


i c m o d u

l u s

030035040045050


ASTM C 666


1100

1000

900

800

700

600

500

400

300

200

1001 2 3 4 5 6 7


S p a c i n g

f a c t o r m

i c r o m e t e r s


















133


20 04

03

02

01

18161412100806040200


C u m u l a

t i v e m a s s

l o s s k g m 2

C u m u l a

t i v e m a s s

l o s s l b f t 2

246

Air content



5

4

3

2

1

00 400200 800600


V i s u a

l r a t i n g









Sulfate Resistance





Strength






134




5

4

3

2

1

002 03025 04 045 05035



l o s s k g m 2

10

08

06

04


l o s s l b f t 22

46

Air content



222 kgm 3

(375 lbyd 3)

306 kgm3

(515 lbyd 3)

392 kgm 3

(660 lbyd 3)

Cementcontent



135


1

2

3

4

5

6




Cementtype

I

I

II

II

V

V





70

60

50

40

30

20

10

02 4 6 8 10 12 14

Air content percent

R e d u c t i o n




35 5

3

428

21



M P a


1 0 0 0 p s i








Workability





136


10 2 3 4 5 6 7 8 9

40

30

20

10

0

5

4

3

2

1

6

Air content percent


h M P a


1 0 0 0 p s i

364 kg m 3 (613 lbyd 3)

308 kgm 3 (519 lbyd 3)

252kgm 3 (425 lbyd 3)



70 10

8

6

60

50

400 1 2 3 4 5 6 7

Air content percent


d a y s M P a

C o m p r e s s


d a y s 1 0 0 0 p s i

025030035040045050



60

40

30

20

10

0

75

50

25

0

100

80

60

40

20

0

20

15

10

05

0




k g m 3


l b y d 3


f t 3 y d 3


d m 3 m 3

300

400 600 800

400 400


400 600 800


300 400 400

8 air

6

8 air

6

4

2

4

2














137























Coarse Aggregate


Fine Aggregate


138



6

5

4

3

2

1

020 24 28 32 36 40 44







12

10

8

6

4

2

095 125 190 250 375 50 63

38 12 34 1 1 1 2 2 21 2



222 kgm 3 (375 lbyd 3)

306 kgm 3 (515 lbyd 3)

388 kgm 3 (655 lbyd 3)

222 kgm 3 (375 lbyd 3)

388 kgm 3 (655 lbyd 3)






S u


s m a t e r i a l s


A g g r e g a t e




139



























140



P r o d u c t

i o n p r o c e d u

r e s












M i x w















141



90

80

70

60

50

40

30

20

100 10 20 30 40 50



96-mm (38-in) slump

46-mm (18-in) slump




e s


i r o n m e n t



2 to 3 system





























142



7

6

5

4

3

2

1

0

50 60 70 80 90



125-mm (5-in) slump

175-mm (7-in) slump

75-mm (3-in) slump

25-mm (1-in) slump







Mixing Action






143



5

4

3

2

1

0100 20 30 40 50 60

11 rpm

4 rpm


Mixing time minutes



8

7

6

5

410 20 30 40 50 60 70 80 90















Finishing








144


5

3

4

2

1

0



050 045 040 035 030 025

Time offinishing

earlyon-time

Bleed water

3

4

5

2

1

0



050 045 040 035 030 025

Time offinishing

earlyon-time














145












146














30

20

10

00

06

04

02

00




k g m 2



l b f t 2

040035030025



020

018

016

014

012

010

008

006

004

002

00 2 4 6 8 10 12 14


r c e n t






Air content percent




REFERENCES






147
























132


100

80

60

40

20

00 50 100 150 200 250 300 350


R e


i c m o d u

l u s

030035040045050


ASTM C 666


1100

1000

900

800

700

600

500

400

300

200

1001 2 3 4 5 6 7


S p a c i n g

f a c t o r m

i c r o m e t e r s


















133


20 04

03

02

01

18161412100806040200


C u m u l a

t i v e m a s s

l o s s k g m 2

C u m u l a

t i v e m a s s

l o s s l b f t 2

246

Air content



5

4

3

2

1

00 400200 800600


V i s u a

l r a t i n g









Sulfate Resistance





Strength






134




5

4

3

2

1

002 03025 04 045 05035



l o s s k g m 2

10

08

06

04


l o s s l b f t 22

46

Air content



222 kgm 3

(375 lbyd 3)

306 kgm3

(515 lbyd 3)

392 kgm 3

(660 lbyd 3)

Cementcontent



135


1

2

3

4

5

6




Cementtype

I

I

II

II

V

V





70

60

50

40

30

20

10

02 4 6 8 10 12 14

Air content percent

R e d u c t i o n




35 5

3

428

21



M P a


1 0 0 0 p s i








Workability





136


10 2 3 4 5 6 7 8 9

40

30

20

10

0

5

4

3

2

1

6

Air content percent


h M P a


1 0 0 0 p s i

364 kg m 3 (613 lbyd 3)

308 kgm 3 (519 lbyd 3)

252kgm 3 (425 lbyd 3)



70 10

8

6

60

50

400 1 2 3 4 5 6 7

Air content percent


d a y s M P a

C o m p r e s s


d a y s 1 0 0 0 p s i

025030035040045050



60

40

30

20

10

0

75

50

25

0

100

80

60

40

20

0

20

15

10

05

0




k g m 3


l b y d 3


f t 3 y d 3


d m 3 m 3

300

400 600 800

400 400


400 600 800


300 400 400

8 air

6

8 air

6

4

2

4

2














137























Coarse Aggregate


Fine Aggregate


138



6

5

4

3

2

1

020 24 28 32 36 40 44







12

10

8

6

4

2

095 125 190 250 375 50 63

38 12 34 1 1 1 2 2 21 2



222 kgm 3 (375 lbyd 3)

306 kgm 3 (515 lbyd 3)

388 kgm 3 (655 lbyd 3)

222 kgm 3 (375 lbyd 3)

388 kgm 3 (655 lbyd 3)






S u


s m a t e r i a l s


A g g r e g a t e




139



























140



P r o d u c t

i o n p r o c e d u

r e s












M i x w















141



90

80

70

60

50

40

30

20

100 10 20 30 40 50



96-mm (38-in) slump

46-mm (18-in) slump




e s


i r o n m e n t



2 to 3 system





























142



7

6

5

4

3

2

1

0

50 60 70 80 90



125-mm (5-in) slump

175-mm (7-in) slump

75-mm (3-in) slump

25-mm (1-in) slump







Mixing Action






143



5

4

3

2

1

0100 20 30 40 50 60

11 rpm

4 rpm


Mixing time minutes



8

7

6

5

410 20 30 40 50 60 70 80 90















Finishing








144


5

3

4

2

1

0



050 045 040 035 030 025

Time offinishing

earlyon-time

Bleed water

3

4

5

2

1

0



050 045 040 035 030 025

Time offinishing

earlyon-time














145












146














30

20

10

00

06

04

02

00




k g m 2



l b f t 2

040035030025



020

018

016

014

012

010

008

006

004

002

00 2 4 6 8 10 12 14


r c e n t






Air content percent




REFERENCES






147























133


20 04

03

02

01

18161412100806040200


C u m u l a

t i v e m a s s

l o s s k g m 2

C u m u l a

t i v e m a s s

l o s s l b f t 2

246

Air content



5

4

3

2

1

00 400200 800600


V i s u a

l r a t i n g









Sulfate Resistance





Strength






134




5

4

3

2

1

002 03025 04 045 05035



l o s s k g m 2

10

08

06

04


l o s s l b f t 22

46

Air content



222 kgm 3

(375 lbyd 3)

306 kgm3

(515 lbyd 3)

392 kgm 3

(660 lbyd 3)

Cementcontent



135


1

2

3

4

5

6




Cementtype

I

I

II

II

V

V





70

60

50

40

30

20

10

02 4 6 8 10 12 14

Air content percent

R e d u c t i o n




35 5

3

428

21



M P a


1 0 0 0 p s i








Workability





136


10 2 3 4 5 6 7 8 9

40

30

20

10

0

5

4

3

2

1

6

Air content percent


h M P a


1 0 0 0 p s i

364 kg m 3 (613 lbyd 3)

308 kgm 3 (519 lbyd 3)

252kgm 3 (425 lbyd 3)



70 10

8

6

60

50

400 1 2 3 4 5 6 7

Air content percent


d a y s M P a

C o m p r e s s


d a y s 1 0 0 0 p s i

025030035040045050



60

40

30

20

10

0

75

50

25

0

100

80

60

40

20

0

20

15

10

05

0




k g m 3


l b y d 3


f t 3 y d 3


d m 3 m 3

300

400 600 800

400 400


400 600 800


300 400 400

8 air

6

8 air

6

4

2

4

2














137























Coarse Aggregate


Fine Aggregate


138



6

5

4

3

2

1

020 24 28 32 36 40 44







12

10

8

6

4

2

095 125 190 250 375 50 63

38 12 34 1 1 1 2 2 21 2



222 kgm 3 (375 lbyd 3)

306 kgm 3 (515 lbyd 3)

388 kgm 3 (655 lbyd 3)

222 kgm 3 (375 lbyd 3)

388 kgm 3 (655 lbyd 3)






S u


s m a t e r i a l s


A g g r e g a t e




139



























140



P r o d u c t

i o n p r o c e d u

r e s












M i x w















141



90

80

70

60

50

40

30

20

100 10 20 30 40 50



96-mm (38-in) slump

46-mm (18-in) slump




e s


i r o n m e n t



2 to 3 system





























142



7

6

5

4

3

2

1

0

50 60 70 80 90



125-mm (5-in) slump

175-mm (7-in) slump

75-mm (3-in) slump

25-mm (1-in) slump







Mixing Action






143



5

4

3

2

1

0100 20 30 40 50 60

11 rpm

4 rpm


Mixing time minutes



8

7

6

5

410 20 30 40 50 60 70 80 90















Finishing








144


5

3

4

2

1

0



050 045 040 035 030 025

Time offinishing

earlyon-time

Bleed water

3

4

5

2

1

0



050 045 040 035 030 025

Time offinishing

earlyon-time














145












146














30

20

10

00

06

04

02

00




k g m 2



l b f t 2

040035030025



020

018

016

014

012

010

008

006

004

002

00 2 4 6 8 10 12 14


r c e n t






Air content percent




REFERENCES






147












Sulfate Resistance





Strength






134




5

4

3

2

1

002 03025 04 045 05035



l o s s k g m 2

10

08

06

04


l o s s l b f t 22

46

Air content



222 kgm 3

(375 lbyd 3)

306 kgm3

(515 lbyd 3)

392 kgm 3

(660 lbyd 3)

Cementcontent



135


1

2

3

4

5

6




Cementtype

I

I

II

II

V

V





70

60

50

40

30

20

10

02 4 6 8 10 12 14

Air content percent

R e d u c t i o n




35 5

3

428

21



M P a


1 0 0 0 p s i








Workability





136


10 2 3 4 5 6 7 8 9

40

30

20

10

0

5

4

3

2

1

6

Air content percent


h M P a


1 0 0 0 p s i

364 kg m 3 (613 lbyd 3)

308 kgm 3 (519 lbyd 3)

252kgm 3 (425 lbyd 3)



70 10

8

6

60

50

400 1 2 3 4 5 6 7

Air content percent


d a y s M P a

C o m p r e s s


d a y s 1 0 0 0 p s i

025030035040045050



60

40

30

20

10

0

75

50

25

0

100

80

60

40

20

0

20

15

10

05

0




k g m 3


l b y d 3


f t 3 y d 3


d m 3 m 3

300

400 600 800

400 400


400 600 800


300 400 400

8 air

6

8 air

6

4

2

4

2














137























Coarse Aggregate


Fine Aggregate


138



6

5

4

3

2

1

020 24 28 32 36 40 44







12

10

8

6

4

2

095 125 190 250 375 50 63

38 12 34 1 1 1 2 2 21 2



222 kgm 3 (375 lbyd 3)

306 kgm 3 (515 lbyd 3)

388 kgm 3 (655 lbyd 3)

222 kgm 3 (375 lbyd 3)

388 kgm 3 (655 lbyd 3)






S u


s m a t e r i a l s


A g g r e g a t e




139



























140



P r o d u c t

i o n p r o c e d u

r e s












M i x w















141



90

80

70

60

50

40

30

20

100 10 20 30 40 50



96-mm (38-in) slump

46-mm (18-in) slump




e s


i r o n m e n t



2 to 3 system





























142



7

6

5

4

3

2

1

0

50 60 70 80 90



125-mm (5-in) slump

175-mm (7-in) slump

75-mm (3-in) slump

25-mm (1-in) slump







Mixing Action






143



5

4

3

2

1

0100 20 30 40 50 60

11 rpm

4 rpm


Mixing time minutes



8

7

6

5

410 20 30 40 50 60 70 80 90















Finishing








144


5

3

4

2

1

0



050 045 040 035 030 025

Time offinishing

earlyon-time

Bleed water

3

4

5

2

1

0



050 045 040 035 030 025

Time offinishing

earlyon-time














145












146














30

20

10

00

06

04

02

00




k g m 2



l b f t 2

040035030025



020

018

016

014

012

010

008

006

004

002

00 2 4 6 8 10 12 14


r c e n t






Air content percent




REFERENCES






147











135


1

2

3

4

5

6




Cementtype

I

I

II

II

V

V





70

60

50

40

30

20

10

02 4 6 8 10 12 14

Air content percent

R e d u c t i o n




35 5

3

428

21



M P a


1 0 0 0 p s i








Workability





136


10 2 3 4 5 6 7 8 9

40

30

20

10

0

5

4

3

2

1

6

Air content percent


h M P a


1 0 0 0 p s i

364 kg m 3 (613 lbyd 3)

308 kgm 3 (519 lbyd 3)

252kgm 3 (425 lbyd 3)



70 10

8

6

60

50

400 1 2 3 4 5 6 7

Air content percent


d a y s M P a

C o m p r e s s


d a y s 1 0 0 0 p s i

025030035040045050



60

40

30

20

10

0

75

50

25

0

100

80

60

40

20

0

20

15

10

05

0




k g m 3


l b y d 3


f t 3 y d 3


d m 3 m 3

300

400 600 800

400 400


400 600 800


300 400 400

8 air

6

8 air

6

4

2

4

2














137























Coarse Aggregate


Fine Aggregate


138



6

5

4

3

2

1

020 24 28 32 36 40 44







12

10

8

6

4

2

095 125 190 250 375 50 63

38 12 34 1 1 1 2 2 21 2



222 kgm 3 (375 lbyd 3)

306 kgm 3 (515 lbyd 3)

388 kgm 3 (655 lbyd 3)

222 kgm 3 (375 lbyd 3)

388 kgm 3 (655 lbyd 3)






S u


s m a t e r i a l s


A g g r e g a t e




139



























140



P r o d u c t

i o n p r o c e d u

r e s












M i x w















141



90

80

70

60

50

40

30

20

100 10 20 30 40 50



96-mm (38-in) slump

46-mm (18-in) slump




e s


i r o n m e n t



2 to 3 system





























142



7

6

5

4

3

2

1

0

50 60 70 80 90



125-mm (5-in) slump

175-mm (7-in) slump

75-mm (3-in) slump

25-mm (1-in) slump







Mixing Action






143



5

4

3

2

1

0100 20 30 40 50 60

11 rpm

4 rpm


Mixing time minutes



8

7

6

5

410 20 30 40 50 60 70 80 90















Finishing








144


5

3

4

2

1

0



050 045 040 035 030 025

Time offinishing

earlyon-time

Bleed water

3

4

5

2

1

0



050 045 040 035 030 025

Time offinishing

earlyon-time














145












146














30

20

10

00

06

04

02

00




k g m 2



l b f t 2

040035030025



020

018

016

014

012

010

008

006

004

002

00 2 4 6 8 10 12 14


r c e n t






Air content percent




REFERENCES






147











Workability





136


10 2 3 4 5 6 7 8 9

40

30

20

10

0

5

4

3

2

1

6

Air content percent


h M P a


1 0 0 0 p s i

364 kg m 3 (613 lbyd 3)

308 kgm 3 (519 lbyd 3)

252kgm 3 (425 lbyd 3)



70 10

8

6

60

50

400 1 2 3 4 5 6 7

Air content percent


d a y s M P a

C o m p r e s s


d a y s 1 0 0 0 p s i

025030035040045050



60

40

30

20

10

0

75

50

25

0

100

80

60

40

20

0

20

15

10

05

0




k g m 3


l b y d 3


f t 3 y d 3


d m 3 m 3

300

400 600 800

400 400


400 600 800


300 400 400

8 air

6

8 air

6

4

2

4

2














137























Coarse Aggregate


Fine Aggregate


138



6

5

4

3

2

1

020 24 28 32 36 40 44







12

10

8

6

4

2

095 125 190 250 375 50 63

38 12 34 1 1 1 2 2 21 2



222 kgm 3 (375 lbyd 3)

306 kgm 3 (515 lbyd 3)

388 kgm 3 (655 lbyd 3)

222 kgm 3 (375 lbyd 3)

388 kgm 3 (655 lbyd 3)






S u


s m a t e r i a l s


A g g r e g a t e




139



























140



P r o d u c t

i o n p r o c e d u

r e s












M i x w















141



90

80

70

60

50

40

30

20

100 10 20 30 40 50



96-mm (38-in) slump

46-mm (18-in) slump




e s


i r o n m e n t



2 to 3 system





























142



7

6

5

4

3

2

1

0

50 60 70 80 90



125-mm (5-in) slump

175-mm (7-in) slump

75-mm (3-in) slump

25-mm (1-in) slump







Mixing Action






143



5

4

3

2

1

0100 20 30 40 50 60

11 rpm

4 rpm


Mixing time minutes



8

7

6

5

410 20 30 40 50 60 70 80 90















Finishing








144


5

3

4

2

1

0



050 045 040 035 030 025

Time offinishing

earlyon-time

Bleed water

3

4

5

2

1

0



050 045 040 035 030 025

Time offinishing

earlyon-time














145












146














30

20

10

00

06

04

02

00




k g m 2



l b f t 2

040035030025



020

018

016

014

012

010

008

006

004

002

00 2 4 6 8 10 12 14


r c e n t






Air content percent




REFERENCES






147





















137























Coarse Aggregate


Fine Aggregate


138



6

5

4

3

2

1

020 24 28 32 36 40 44







12

10

8

6

4

2

095 125 190 250 375 50 63

38 12 34 1 1 1 2 2 21 2



222 kgm 3 (375 lbyd 3)

306 kgm 3 (515 lbyd 3)

388 kgm 3 (655 lbyd 3)

222 kgm 3 (375 lbyd 3)

388 kgm 3 (655 lbyd 3)






S u


s m a t e r i a l s


A g g r e g a t e




139



























140



P r o d u c t

i o n p r o c e d u

r e s












M i x w















141



90

80

70

60

50

40

30

20

100 10 20 30 40 50



96-mm (38-in) slump

46-mm (18-in) slump




e s


i r o n m e n t



2 to 3 system





























142



7

6

5

4

3

2

1

0

50 60 70 80 90



125-mm (5-in) slump

175-mm (7-in) slump

75-mm (3-in) slump

25-mm (1-in) slump







Mixing Action






143



5

4

3

2

1

0100 20 30 40 50 60

11 rpm

4 rpm


Mixing time minutes



8

7

6

5

410 20 30 40 50 60 70 80 90















Finishing








144


5

3

4

2

1

0



050 045 040 035 030 025

Time offinishing

earlyon-time

Bleed water

3

4

5

2

1

0



050 045 040 035 030 025

Time offinishing

earlyon-time














145












146














30

20

10

00

06

04

02

00




k g m 2



l b f t 2

040035030025



020

018

016

014

012

010

008

006

004

002

00 2 4 6 8 10 12 14


r c e n t






Air content percent




REFERENCES






147




















Coarse Aggregate


Fine Aggregate


138



6

5

4

3

2

1

020 24 28 32 36 40 44







12

10

8

6

4

2

095 125 190 250 375 50 63

38 12 34 1 1 1 2 2 21 2



222 kgm 3 (375 lbyd 3)

306 kgm 3 (515 lbyd 3)

388 kgm 3 (655 lbyd 3)

222 kgm 3 (375 lbyd 3)

388 kgm 3 (655 lbyd 3)






S u


s m a t e r i a l s


A g g r e g a t e




139



























140



P r o d u c t

i o n p r o c e d u

r e s












M i x w















141



90

80

70

60

50

40

30

20

100 10 20 30 40 50



96-mm (38-in) slump

46-mm (18-in) slump




e s


i r o n m e n t



2 to 3 system





























142



7

6

5

4

3

2

1

0

50 60 70 80 90



125-mm (5-in) slump

175-mm (7-in) slump

75-mm (3-in) slump

25-mm (1-in) slump







Mixing Action






143



5

4

3

2

1

0100 20 30 40 50 60

11 rpm

4 rpm


Mixing time minutes



8

7

6

5

410 20 30 40 50 60 70 80 90















Finishing








144


5

3

4

2

1

0



050 045 040 035 030 025

Time offinishing

earlyon-time

Bleed water

3

4

5

2

1

0



050 045 040 035 030 025

Time offinishing

earlyon-time














145












146














30

20

10

00

06

04

02

00




k g m 2



l b f t 2

040035030025



020

018

016

014

012

010

008

006

004

002

00 2 4 6 8 10 12 14


r c e n t






Air content percent




REFERENCES






147












S u


s m a t e r i a l s


A g g r e g a t e




139



























140



P r o d u c t

i o n p r o c e d u

r e s












M i x w















141



90

80

70

60

50

40

30

20

100 10 20 30 40 50



96-mm (38-in) slump

46-mm (18-in) slump




e s


i r o n m e n t



2 to 3 system





























142



7

6

5

4

3

2

1

0

50 60 70 80 90



125-mm (5-in) slump

175-mm (7-in) slump

75-mm (3-in) slump

25-mm (1-in) slump







Mixing Action






143



5

4

3

2

1

0100 20 30 40 50 60

11 rpm

4 rpm


Mixing time minutes



8

7

6

5

410 20 30 40 50 60 70 80 90















Finishing








144


5

3

4

2

1

0



050 045 040 035 030 025

Time offinishing

earlyon-time

Bleed water

3

4

5

2

1

0



050 045 040 035 030 025

Time offinishing

earlyon-time














145












146














30

20

10

00

06

04

02

00




k g m 2



l b f t 2

040035030025



020

018

016

014

012

010

008

006

004

002

00 2 4 6 8 10 12 14


r c e n t






Air content percent




REFERENCES






147











140



P r o d u c t

i o n p r o c e d u

r e s












M i x w















141



90

80

70

60

50

40

30

20

100 10 20 30 40 50



96-mm (38-in) slump

46-mm (18-in) slump




e s


i r o n m e n t



2 to 3 system





























142



7

6

5

4

3

2

1

0

50 60 70 80 90



125-mm (5-in) slump

175-mm (7-in) slump

75-mm (3-in) slump

25-mm (1-in) slump







Mixing Action






143



5

4

3

2

1

0100 20 30 40 50 60

11 rpm

4 rpm


Mixing time minutes



8

7

6

5

410 20 30 40 50 60 70 80 90















Finishing








144


5

3

4

2

1

0



050 045 040 035 030 025

Time offinishing

earlyon-time

Bleed water

3

4

5

2

1

0



050 045 040 035 030 025

Time offinishing

earlyon-time














145












146














30

20

10

00

06

04

02

00




k g m 2



l b f t 2

040035030025



020

018

016

014

012

010

008

006

004

002

00 2 4 6 8 10 12 14


r c e n t






Air content percent




REFERENCES






147
















141



90

80

70

60

50

40

30

20

100 10 20 30 40 50



96-mm (38-in) slump

46-mm (18-in) slump




e s


i r o n m e n t



2 to 3 system





























142



7

6

5

4

3

2

1

0

50 60 70 80 90



125-mm (5-in) slump

175-mm (7-in) slump

75-mm (3-in) slump

25-mm (1-in) slump







Mixing Action






143



5

4

3

2

1

0100 20 30 40 50 60

11 rpm

4 rpm


Mixing time minutes



8

7

6

5

410 20 30 40 50 60 70 80 90















Finishing








144


5

3

4

2

1

0



050 045 040 035 030 025

Time offinishing

earlyon-time

Bleed water

3

4

5

2

1

0



050 045 040 035 030 025

Time offinishing

earlyon-time














145












146














30

20

10

00

06

04

02

00




k g m 2



l b f t 2

040035030025



020

018

016

014

012

010

008

006

004

002

00 2 4 6 8 10 12 14


r c e n t






Air content percent




REFERENCES






147





























142



7

6

5

4

3

2

1

0

50 60 70 80 90



125-mm (5-in) slump

175-mm (7-in) slump

75-mm (3-in) slump

25-mm (1-in) slump







Mixing Action






143



5

4

3

2

1

0100 20 30 40 50 60

11 rpm

4 rpm


Mixing time minutes



8

7

6

5

410 20 30 40 50 60 70 80 90















Finishing








144


5

3

4

2

1

0



050 045 040 035 030 025

Time offinishing

earlyon-time

Bleed water

3

4

5

2

1

0



050 045 040 035 030 025

Time offinishing

earlyon-time














145












146














30

20

10

00

06

04

02

00




k g m 2



l b f t 2

040035030025



020

018

016

014

012

010

008

006

004

002

00 2 4 6 8 10 12 14


r c e n t






Air content percent




REFERENCES






147













Mixing Action






143



5

4

3

2

1

0100 20 30 40 50 60

11 rpm

4 rpm


Mixing time minutes



8

7

6

5

410 20 30 40 50 60 70 80 90















Finishing








144


5

3

4

2

1

0



050 045 040 035 030 025

Time offinishing

earlyon-time

Bleed water

3

4

5

2

1

0



050 045 040 035 030 025

Time offinishing

earlyon-time














145












146














30

20

10

00

06

04

02

00




k g m 2



l b f t 2

040035030025



020

018

016

014

012

010

008

006

004

002

00 2 4 6 8 10 12 14


r c e n t






Air content percent




REFERENCES






147


















Finishing








144


5

3

4

2

1

0



050 045 040 035 030 025

Time offinishing

earlyon-time

Bleed water

3

4

5

2

1

0



050 045 040 035 030 025

Time offinishing

earlyon-time














145












146














30

20

10

00

06

04

02

00




k g m 2



l b f t 2

040035030025



020

018

016

014

012

010

008

006

004

002

00 2 4 6 8 10 12 14


r c e n t






Air content percent




REFERENCES






147





















145












146














30

20

10

00

06

04

02

00




k g m 2



l b f t 2

040035030025



020

018

016

014

012

010

008

006

004

002

00 2 4 6 8 10 12 14


r c e n t






Air content percent




REFERENCES






147

















146














30

20

10

00

06

04

02

00




k g m 2



l b f t 2

040035030025



020

018

016

014

012

010

008

006

004

002

00 2 4 6 8 10 12 14


r c e n t






Air content percent




REFERENCES






147











REFERENCES






147









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