鉱物質混和材を用いた超高強度現場打ちコンクリートに関する研究 : 練り混ぜ方法の違いがコンクリートの流動性に及ぼす影響

NII-Electronic Library Service

(:ft

sc]

,

JDurnal

ef

Structural

and

Construction

Engineering

Rptrcva\ftifiin"!kas,maNW=fi

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16

(Transactions

ofAIJ) No.

401,

Juiy,

lgsg

･

rg4Ole

･1･9

89ij

7

fi

STUDY

ON

ULTRA

HIGH-STRENGTH

CAST-IN-PLACE

CONCRETE

USING

MINERAL

ADMIXTURES

.

(Effect

of

USing

Different

Mixing

Methods

on

Flowability

of,Concrete)

by

Dr.

Eng,

MASAYOSHI

KAKIZAKI*r'

and

HIDETOSHI

EDAHIRO*2)

Members

of

A.

I.

J.

1.

.lntroduction

Efforts

to

improve

the

strength of concrete

have

been

successful owing

te

the

recent

development

of a

high-iange

water-reducing admixturel

At

_present,

high-strength

cast-in-place

concrete

with aspecified

design

strength of

_42e

to

4sO

kgflcm2

is

being

used, and

buildings

employing concrete with a specified

design

strength of over

600

kgflcm2

are-planned.

Th'e

demand

for

high-strength

concrete

is

expected

to

be

conside[able

because

of

the

material's

benefits

in

t6rms

of

'

both

design

and economy and

lts

applicability

to

a wide variety of structures such as,

high-rise

buildings

of

'

reinforced

concrete

structures

(RC),

structures

with

long

spans,

and

other

large

structures

such

as

nuclear

power

'

plants.

･

_/･

'･

Recently,

Ieading

construetion companies

have

intensively

applied

themse]ves

to

the

cpnstruction of

high-rise

buildings

_{RC)

exceeding

30

f]oor$.

With

TegaTds

to

such

buildings,

improvements

in

the

strength and workability of

the

concrete used are

the

important

issues

from

the

viewpoint

of

eonerete

engineering.

In

fact,

consldering

the

use of iich-mik concrete and admixture such

as

air-entraining and

highirange

Water

reducing

admixture

a4d

others,

the

flowability

of such concrete

is

not

sufficiently

understood compared with

that

of ordinary concrete.

The

low

water-cement ratiQ of

the

high-strength

concrete

cUrrently

used results

in

a rich-mix congrete with an

excessively

large

unit cement content, and

irnprovements

in

workability are

dependent

on

the

function'of

a'

high-range

water-reducing adlnixture,

This

type

of concrete

has

problems

such as

large'variationsiris

consistency and

Large

changes of slump values oveT

time

and additionally

its

characteristics'of workgbility are

different

from

_that

of ordinary _concrete.

Accordingly,

workability

is.of

_considerable

importance

whe're

high-stTength

_concrete

is

concerned

It

should also

be

noted

that

the

_quality

of

the

concrete

is

heavily

dependent

on

the

mixing

method as well as on

the

materials used,

the

mix

_proportion,

the

_placing

method, and

the

curing conditions])-3),

Concerning

mixing methods,

improvements

in

consistency and workability, as

Well

as strength are

_particularly

desireable.

There

are

two

types

of mixing methods:those

in

which

the

mixing water

is

added

in

two

stages,

that

is,

Sand

Env'eloped

with

Cement

Method

(SEC

method),

Double

Mixing

Methocl

(DM

method),

sepaiation

method

;

and'

those

in

which

the

water

is

added all at one

time

(fuixing

the

cement and water

first,

mixing

the

cement and

fine

'

aggregate

first),

There

are

dozens

of combinations of mixing-methods.

Also,

ip

rich-mix'

concrete

with a

high

'

(cement

_±

condensed admixture

)-to-water

ratlo, such as

high-strength

concrete, avariety of

factors

such as

the

o'rder of adding

the

materials,

dosage.

rate

6f

the

adrnixture

and

the

time

at which

it

is

added,

the

mixing

_period

and

the

/

t

rotation

speed

of

the

mixel,

as

well

as

the

_performance

of

the

mixer, affect

the

ovefall

_performance

of

the

'

'

'

'

COncretei)`4}

-

,

,

t.

Consequently,

the

aim of

this

study

is

to

develop

economical and

high-quality

ultra

high-strength

concrete and

te

improve

the

workability

ef

this

concrete,

For

this

_purpose,

'admixture

of

three

types

-

silica

fume,

fly

ash,

land

']'

_KAJIMA

_CORPORATION

_Kajlma

#'

_Shibaura

_Institute

_of

_TeahnoLegy

{Manuscript

receiveci

January

9,

19S9;

Institute

of

Censtruction

Technology

Papet Accepted May

8,

1989)

micrepowder

blast

furnace

slag

-

wefe used.

The

effects of

the

order of adding

the

concrete's

constituen,t

rnaterials

cluring

mixing

and

the

time

at

which

the

high-range

water-reducing admixture

and

mineral admixtures wei'e added on

the

flowabi]ity

ahd

the

segregation of

the

component materials of

the

fresh

concrete were evaluatE/cl.

The

_paper

al$e

proposes

a

_practical

mixing method

for

ultra

high-strength

concrete.

2.

Experimental

Program

2.l

Test

Items

Table2.1

shows

the

items

and

the

contents of

the

experiments

_performed

on

fre$b

concTete.

2.2

Materials

Used

for

the

Experiments

(1)

Cement:

'

High-early-strength

Portland

cement made

by

Nihon

Cement

Co.

,

Ltd.

was used.

Table

2.

2

shows

the

physical

'

properties

of

the

cement.

<2)

Aggregates:

The

fine

and

the

coarse aggregates used were all collected at

Fuji

River

in

Shizuoka

Prefecture.

Table

2.

3

shows

the

_physical

_properties

of

the

aggregates.

(3)

Chamical

admixtures:

Table

2,4

shows

the

main components and

the

commercial

narnes

of

the

air-entraini]g

admixture,

_the

high-range

water-reducing admixture, and

the

superplasticizing admixture.

(4)

Mineral

aclmixtures1

The

mineral admixtures were selected

due

to

considerations of cost and ability

to

improve

the

physical

_pToperties

of

the

concrete,

after consulting

_past

research

_papers5)'6)

and other

_{publications7)-9).}

Table

2.

5

Bhews

the

_physical

propertie$

of silica

fume,

fly

ash, and micropowder

blast

furnace

slag.

2.3

Mix

Proportions

･

Table2,1

Test

Items

and

Contents

Table2,2

Physical

Properties

of

Cement

Compressive strength

Ckgi]'cmz)

lda/ts

28days

361

466

Item

Content

Slvmp

a.SlumpandsSumpwithtime(crn)

b.FIDwandtlewwithtime<cmXcm)

c.Workebility:visual

Air

Air(O/o)

Flowabilityof

concreteand

Segregationof

concrete a,FIowabilityofconcretedueto vibration(Fvalue)

b.Segregationotconcretewhenitismade

toflowamengreintorcingbarsbyvibretlon

(SvaSue)

_'

c.Segregat[onofcDncreate:visual

Compositedistribution

ofcencreteCoerseaggregatelmortarratio

Table2.4

Physical

Properties

of

Chernical

Adrnixture

･KindsPrincipalingredientSpecMcgravity(20

℃

pHExternalappearance

Air-entraining

admixtureArkylaryssvlfenate(anienictype

surfactant)

T

-Lightyellow

liquid

High-range

water-reducing admixture

Sulfonateot

highconden-satienaromatic1.18"･1.127-v8Darkbrown

liquid

uperplasticizing admixtureCompositeof

naphtharen-sulfonatetype

1,1,7'vl.197"･9Blackbrown

liquid

Timeofsetting

Typesofcement.SpecMcgravity5pecMcsurface'BIaine(cm'fe)Water[nitiaiFinzlsetting Bendingstfength(kgt!cml} emount%setting(hr-mim){hr-min)ld3ys28day

High-eerlystrengih3.14436029,82-163-286476

Table2.3

PhysLcal

Properties

ef

Aggregatd]

KindsMaximvrnsize(mm)

SpeciticgrayityWaterabserption%o)

Bulkden/iity{kglO

Mlntageofsoridvorurne(%)Finenessmodulus

Flneaggregate52.611.861.7768.82.9

CoarseaggregateZ52.65O.631.1'165.0"

Table2.5

Specificsurface(cmZlg)ChE

KindsSpecificgravity

Si02

Silicafume2.23220,ODO92.3

Flyash2.24

3,02053,S

Bjastfurnaces!ag2.9

8,OOO35.9

Physicat

Properties

and

Chemical

ArLalysis

of

Mineral

Admixtures

Chemical

-12-NII-Electronic Library Service

<1)

Aims

,

,

a>

The

water-to-(cement+conclensed admixture) ratie was set at

30'%

in

order

to

obtain a specified

design

strength

of

450-80okgflcm2.

b)

The

unit water content was

175

kglm3,

in

accordance with

the

Japanese

ATchite.ctural

Standard

Specification

for

Reinforced

Concrete

Work

_(JASS5)

for

high-durability

concrete.

'

'

c)

_.

The

sand-aggregates

ratio was set at

35

%

on

the

basis

of a

_pTevious

text

mixing,･ so

that

the

superplasticized

'

concrete shoul'd

be

workable.

d}

The

slump was set at

lz

±

1.

s

cm

fer

the

base

concrete and at

18

±

1.

5

cm

for

the

suPerplasticized concrete,

in

accorclance with

the

conventional mixing method

in

which all

the

materials are mixed

from

th'e

beginning.

e)

The

amount ef air was set at

2-4

%

foT

both

the

base

concrete and

the

supeiplasticized concrete.

{2)

Mix

proportions

'

Tab[e2.6

shows

the

mix

_proportions

of various

types

of cencrete with a

fixed

water-to-{cement+condensed

admixture) ratio and a

fixed

unit

Table2.6

Mix

Proportion

of

Conc[ete

water content.

2.4

Mixi4g

Conditions

Tab162.7

shows

the

mixing

methods;

Table2.8

the

mixing

coriditions

;

and

Table2.9

lists

the

combinations which were

ted

The

standard methods of

mixing were:mixing

-all

the

materials

together

from

the.

,NOte5

il.ge.i:.l,,enflC:1),+(sAFd)[.i.flV[rcetAL:kl;:d,ex"i;d.seidMiXt"reCC+A)kg!M3

5)i:g""'id"."l,etr.,C,OrteH"iEh=-,A,il-ge,ntrai"-beginning;

'mixing

the

cement

3)

Fiyash

(FF)･･････{c+A)ig!m;x2o%

-

water-reducing edmixture al}d water

first,

then

adding

the

4)

Btast

furnace

sleg(SS)･--･''(C+A)kg!nn]X40%

6)

_perceotage

_ofsurface rnoisture _{other rnaterials a}

few

_seconds

en tineeggrekate:2'-3%

latef;.and

mixing

the

cement and

Table2,7

Mixing

Methods

fime

aggregate

first,

,then

adding

the

water

and

the

other

materials

a

few

seconds

later

"ncluding

cases

in

which

slurry

is'adcled).

A

vertical shaft mixer with a

100-liter

capacity

was used

in

the

expenments,

2.5

Expevimental

Method

'

Notes

C/cement content/W:water content:

W(ad)/water

,water-reduclng

edmixture: S:fine aggregate: G

slurfy :mineral admixturelwater=2

Cweight

ratio)

Table2.8

Mixing

Condition

Mix

Ne.

a-EE)U-L..m

W-C+Atas:qt.NCbOl8eg;.2..Eg.x..opM--.LmfieELXX:'e.anIX-eLe･-xo-bE==vEVndKi.eee

tubatznMi.'g',?.fE; mp"N,?Ev'.s tu.Edi,bl..Atv--ts:-iasEa:Es.6ma"Ns

3･A

I8

583-4.549.85

=

3･SP12-1B

583-S,82S.S4O,S8

3･SF12-18O.3[75'51D?35,8Z7.SS1.62

3･FFi2-18

466i1717.487,85O.82

3･SS12.IB

S5023311.654,2SO.34

Symbol

Threw[ngorderofmaterial

ACS+C+siurry+wCad)+G)'-Sesec..SaUdPneilxPtluaietieiiing-3esec.--+ BCS+C+W(ad})-30sec.-(G+'slurry)-60sec,- ditto

c(S+C+slurry)-30sec.-+CG+WCad])-60sec,-

ditto

D{S+C)-30sec.-,(slvrry+W(ad)+G)-60sec.-

d[tto

E{C+W+slurry)-30sec,-+(S+W(ad}+G)-60sec.-ditto

F

<CtW+slurry)-30sec,-(S+W{ed))-3Dsec,-(G)-30set.-ditta

'

Comditien

Contents

Threwingorderof'materia[s.

a.Mixingalltherneter[alstogetherframthebeginni c,M[x[ngthecementandwaterfirst d.Mixingthecementemdf]neeggregatefirst Additionmethod Mineraladmixturewasusededdedasaslurry

(Water/Admixture=:2:r,weightfntio)

Surfacemeis-tureaffineaggregate2-3e/o Mixingtime'

9esec.Afteradditienofsupefplastici!ing

adrnixture;30sec,

Mixer

wes used ferforced stirup

to

1OOe',

content and

high-renge

Table

2.

10

shows

the

ex-,coarseaggregate;

perimentaL

method.

The

ing

are

the

details

of

the

ments:

.'

'

<1)

Dynamic

flowability

of

the

copcrete

The

flowability

of

fresh

concrete

is

apparent mainly

i4

the

softness

of

the

concrete

and

is

clue

to

the

amount

Table2.g

Test

6ombination

MixingnemberThroWingorderofmaterials

Remarks 3･A3･SP

A,C,E,F Mineraladmixtureisnotused 3-SF3･Ff3･SS

A.

B,

C,

D

Admixture_{added asa}of_slurry

SF,FF,SS

_{was used}

Table2,10

Test

Method

ttem Method Content

Sfump

JISALIOI

Air J]sAIr2sa,Stum'pendslumpwlthtime(cm}

b.Flowandtlowwithtime(tmXcm)

c,AircontentCOra)

Frowabitityot

concrete;segregation ofconcrete StandardSpeeificetiontor DeslgnendCenstruetion ofComcreteStructures, jepanSocietyefCivi[ Engineers,1961 e.Vseofvibretien-tYpecensistency

testCVFtest)

b.Fig.2.1showsthestructure

compositedistributionofooncreteJISA1119Coarseeggregate!rnertarratio

Notes

JIS:Japanese

]ndustrial

Standard

A

:

Symbol

of

C;vil

engTneerTng and architecture class

Cylinder

A

le,',e.:n,,c,'r!Ln,d,erA)

I

:n,flgrsi:cg,eii?,;o)

nderA 1somm-bx3oomm ugh

_B

:l90mm,px

60mm

ugh

C

･s3omm,bx

somm a

D

Fig.2.1

VF

Test

Equipment

of water

_present

;

this

_property

may

be

defected

also

in

the

resistance

to

deformation,

and

its

ability

to

be

compacted.

A

slump

test,

a

_penetrating

test

using a

ball,

a compaction

test,

a

VB

test,

a vibration-type consistency

test

(VF

test),

a vibration

table

consistency

test,

and

five

other

tests

were used

to

determine

the

flowability

values.

These

tests,

with

the

exception of

the

slump

test,

are

thougth

to

be

useful

for

evaluating

the

_properties

of

stiff-consistency

concrete

in

civil

engineering

structures.

Also,

Dr.

Tanigawa

has

proposed

various

simulation

methods

measur

f!owability,

the

central

theme

of

construction

designiO)･]i).

However,

it

seems

that

as

_yet

it

has

not

been

_possible

to

apply

these

methods

to

the

evaluation of

the

flowability

of

high-strength

concrete with a

high

(cement+cendensed

admixture)-to-water ratio

in

actual works,

On

the

other

hand,

the

consistency when

_placing

the

high-strength

¢

oncrete

obtained

using silica

fume,

fly

ash, or micropowder

blast

furnace

furnace

slag, and

a

high-range

water-reducing admixture,

is

_quite

different

from

that

of ordinary concrete.

Therefore,

it

is

necessary not

to

rely on

the

slump

test

alone,

but

to

combine

it

with other

tests

in

erder

to

judge

the

overall censistency,

Thus,

the

tests

were

performed

with

the

emphasis on evaluating

the

_properties

of static and

dynamic

consistency

of

the

ultra

high-strength

concrete

produced

using

a

high-range

water-reducing admixture,

the

flowability

of

the

concrete

in

the

bar

arrangement condition, and

the

segregation of

the

concrete.

The

vibration-type consistency

test

in

the

dynamic

state

(VF

test)

was used

because

it

is

suitable

for

determining

the

flowability

and

the

seg:regation of concrete when

it

is

made

to

flow

among reinforcing

bars

by

vibration, as

indicated

by

the

results of

_previous

publicationsiZ)nyi`)

and

by

the

writeis own researchS]･6).

Figure

2.

1

shows

the

design

of

the

VF

equipment used

for

determining

the

dynamic

flowability.

The

values _used

to

describe

dynamic

flowability

_{and seglegation}

of

concrete

are

defined

as

follows

:

a)

F16wability

of

the

conc[ete

by

vibration

(F

value)

Cylider

A

is

fMed

with concrete

(Fig.2.1),

and

the

vibrator

is

started and run until

trough

C

is

Sull,

The

time

taken

in

seconds

is

called

the

frequency,

or

F

value.

b)

Segregation

of concrete when

it

is

made

to

flow

among reinforcing

bars

by

_yibration

(S

value).

The

depth

of

the

conc[ete remaining

in

the

cylincler when

trough

C

is

full

is

measured.

This

depth,

in

centimeteTs,

is

defined

as

the

_S

value.

(2)

Distribution

of

the

components

in

the

concrete

The

distribution

of

the

components was

determined

in

accordance with

Japanese

lndustrial

Standard

<JIS)

A

1119,

the

test

method

for

the

variability of

the

constituents

in

freshly

mixed concrete.

Samples

were colLected

from

each of

the

troughs

in

Fig.

2.

1.

A

sieve with

5-mm

mesh

apertures

was used

to

separate

the

mortar and

the

coarse

aggregate.

The

_quantity

of each component was

divided

by

the

base

area of

A,

B,

C,

or

D

to

obtain

the

uni':weight ratio.

The

evaluation was made

based

on unit weight ratio

(GIM},

G

representing

the

amount of coarse aggregate and

M

the

amount

of

mortar.

3,

ExOerimental

Results

and

Consideration

3.1

Static

Flowability

of

Fresh

Concrete

3.1.1

Effect

of mixing method on slump

Figure

3.1

shows.the relationship

between

the

mixing methocl ancl

the

slump

of

the

base

cohcrete and

the

superplasticized concrete,

The

slump values vary according

to

the

mixing method, even

if

the

mix

_proportion

-14-NII-Electronic Library Service

rernains

the

safrie.

In

_particular,

the

slump values of

the

concrete

_prepared

by

mixing

the

cement and

fine

aggregate

first

(methods

,C

and

D)

and

that

of

the

concrete

_prepared

by

mixing

the

cement and water

first

(rnethods

E

and

F)

were

20-3o

%

higher

than

these

of cement

_prepared

by

mixing all

the

materials

together

frgm

the

beginning

(method

A).

Analyzed

in

terms

of

types

of concrete,

the

concrete

prepared

using mix

proporticns

3･A

gnd

3･SP

apd mixing conditions

E

and

F

showed a

_gLump

of,approximately

25

cm, which was about

30

%

larger

than.that

for

mixing method

A

A

slight

segiegation

ef

materials occurred,

Furthermofe,

the

slump

in

the

case

of

mix

_proportion

3･SF

and

_mix

'

conditions

C

and

D

was approximately

24

crn

;

that

for

mix

proportion

3･FF,

approximately

27

cm

;

and

that

for

mix

'

proportion

3･SS,

approximately

25

cm.

These

values

are

about

20-35

%

higherthan

that

formixing

condition

A

_cnd

are about

4o-50

%

hl'gher

rhan

that

for

mixing condition

B.

The

slump values

in

the

superplasticize,d

concrete were

found

to

be

approximately

6

cm

higher

than

in

the

base

concrete

in

th6

case

of mixing method

A,

4-8

crn

higher

in

the

case

of

mixing

method

B,

and

1-3

cm

higher

in

the

case of rnixing methods

C,

D,

E,

and

F.

It

seems

that

th,e

smaller

the

slump

value

of

the

base

concrete,

the

greater

th'e

effects

of

the

superplasticizing

_qd.mixture.

The

fact

that

the

slump values

for

methods

C

and

D

are

higher

than

those

for

methods

A

and

B

can

be

explained as

follows

_;

A

high-range

weter-reducing admixture

is

added

to

the

mixture.after

the

water

has

either

been

absorbed

by

the

cement

_particles

or

has

covered

the

surface of

the

aggreg4te.

Thus,

the

amount of

high-range

water-reducing aclmixture absorbed or

lost

becomes

smaller.

The

zeta

potential

becomes

high,

creating a well-dispersed concrete,

'

'

The

Tesistan6e

due

to

the

concTete's coslstency

becomes

weaker.

HoweveT,

there

was a slight

tendency

toward

segregation

of

the

component materials

in

the

superplasticig6d concrete.

This

appear$

to

be

due

to

the

excellent

dispersing

_property

of

the

high-range

water-reducing admixture.

On

the

other

hand,

the

small

slump,obtained

with mixing method

B

s'eems

to

indicate

that

a

large

_proportion

of

the

high-range

water-reclucing admixture

is

absorbed

by

the

C,A

or

C,AF

in

the

cement,

thus

reducing

the

residual

'

amount

of

high-range

_{.water-reducing}

admixture

in

the

sglytion.

'

3.1.Z

'Slumplflovi

relationship

FiguTe

3,

2

shows

th.e

rerationship

between

the

slump and

flow

and

that

between

the

slump and

FLI,S.

The

flow

values

increased

slowly

up

t6

the

slump range

of

ls-16

cm

and

then

increased

rapidly

_producing

₄

_quadratic

curve.

No

difference

was

detected

between

_the

use of

different

mixing methods as

far

as.

the

stumplflow relationship and

_the

retationship

between

the

slump

and

FLIS

were conceTned.

The

slump value

changed

at ±

].

s

cm

and

the

flow

rate

changed

at ±

7.

5

cm

when

the

stump

exceeded

15

cm,

Thus,

thg

flow

rate underwent a

Iarger

change

than

the

slump,

Th.erefore,

it

may

be

possible

that

concretes of

different

flow

or workability will

be

obtained even

if

the

slunip

is

controlled.

TakagiL5)

and

TakayamaZ2)

_pointed

out

this

_possibility,

too.

Furthermore,

the

lower

limit

of

FLIS

was around

1.5

with a slump of

18cm.

Thus,

when

FLIS>2,

the

slunip

is

less

than

10

cm or mo[e

than

20

cm.

It

is

difficult

tp

estimate

the

degree

of segregation

from

302S-20Esa

ISE-=en 10so

W!(C+A)==O.3Superptasticiledconcrete

Base concrete

asme

765:t

E4g

83s

<2

ACEF ACEF

ABCD

ABCD

ABCD

MixTng

methad

Fig.3.1

Relhtionship

betw

¢en

Mixing

Method

and

Slump

'and

Air

Content

80'70

E

6os2 sosl

409L

30

20

,10D

Fig,

3.

2

S

tO l5 20 Z5

,

Slump

(S)

(cm>

Relatienship

between

Slutnlp

and

Flow!Slump

30 7

6

A5

U)

×

J

L4 s-" a

E3

-=

･

co

× 21

-o

L1

o

Flow

and

'

'

-･15

-the

values

of

FLIS.

The

consistency

of

high-flow

concrete

with

a

slump value exceeding

18cm

can

be

esd/imated

closely whed

the

flow

rates and values of

FLIS

are

lower

thall

the

lower

limit

of each curve,

3.

1.3

Effect

of mixing method on

flow!slump

Flow!slump

CFLIS)

was used as an

index

of workability of

the

concTete

_{preparations.}

Figure

3,3

shows

the

relationship

between

the

mixing methods and

FLIS.

The

figure

shows

that

the

target

value

for

FLIS

in

mixing method

A

was set at

1.

5.

0n

the

other

hancl,

FLIS

in

methods

C,

D,

E,

and

F

was

_greater

_thELn

₂

in

the

cases of mixing

_proportions

3.A,

3.SP,

3.FF,

and a

part

_ef

3.SS.

The

concrete

in

which

the

water-to-{cement+condensed

admixture) ratio was

low

and which was

prepared

using a

large

amount

of

high･range

water-reducing admixture and an admixture with

a

large

specific

surface

Cblaine)

had

a

high

resistance

to

segregatLon, even

if

FL/S

was

between

2

and

2.

2.

This

seems

to

indicate

that

the

upper

limit

of workability occurs at an

FLIS

value of approximately

2.

Furthermore,

whether

the

workabiliLy of

the

ultra

high-strength

concTete

is

good

or

bad

can

be

estimated

from

the

values

_given

in

Table3.1.

FLIS

of

the

high-strength

concrete

was

higher

than

that/

of ordinary conerete.

3,1.4

Change

with

time

of

flow-slump

(FLIS)

valttes

Figures3.4

to

3.8

show

the

relationship

bewtween

FLIS

and

time.

The

workability of various concrete

preparations

was estimated using

the

values

in

Table

3.

1.

The

change with

time

of

FLIS

of concrete

_prepared

by

mixing

the

¢ement and

fine

aggregate

first

and of

that

_pTepared

by

mixing with cement and water

fi

rst. wa$ srnalLler

than

that

of

concrete

_prepared

by

other

mixing

methods.

Also

_,

there

was a

tendency

for

FLIS

to

be

smaller

the

later

the

high-range-water-reducing

admixture was

addecl,

FLIS

for

mix

_proportion

_3･A

fell

te

between

1,

5-

and

₂

after

60

to

go

minute$

in

the

case of mixing methods

C

and

F

_;

while

FLIS

for

mix

_proportion

3.SP

in

the

case of mixing methods

C,

E,

and

F

fetl

to

between

_1.

_s

and

_1.9

after

30

to

₉₀

minutes.

On

the

other

hand,

measurements of

FLIS

for

mix

proportion

3.SF

produced

values

different

from

those

of other concrete

preparations.

In

the

case of mix

_proportion

3.SF,

it

was necessary

to

increase

the

unit water content and

the

amount of

high-range-water

reducing admixture

in

order

to

obtain a slump value of

18cm.

Grutzeck

pointed

eut

that

by

adding ultra-fine silica

_particles,

the

silica-enriched

_gel

coating covers

tb.e

silica

fume

particles

imrnediately

after

the

sllica

fume

is

mixed with a

Ca(OH),

solutionZM.

FLIS

for

mix

_proportion

3.FF

in

the

case of mixing rnethods

C

and

D

fell

to

between

_1.

₆

and

_L

9

afte/r

90

minutes.

These

values shQw

that

the

concrete

_preparation

was workable at

that

stage.

However,

FLIS

befoie

90

rninutes was

between

_2.1

and

2.6,

and

these

values show a

lower

resistance

to

segregatlon.

On

the

other

hand,

FLIS

for

mix

_proportion

_3･SS

in

the

case of mixing methods

C

and

D

felL

to

between

_].

_s

ancL

3.0a

zsE2E(l

2.esL 1.S

1.0

ACEF

ACEF ABCD ABCD ABCD

Mixing

method

Fig.3.3

Relationship

between

Mixing

Method

and

FlowlS)ump

Table3,1

Standard

of

Workability

Appraisa]

3:AWl(C+A)=O.33･SP3･SF

-/ttt

3･FFtE･･3･SS.'

･[l:/'l･lal

'

,a

glts{vlt･

k,lgll"'

llj･1ff,

IFIttll'fi'g

_'glii

"i '

ll'lf]../t/t',l/g:t.//,fli,tt./tttt..tfts't:.,lt,1"I･tt･.;/;/it.x:k/li.:.

Flewlslump

Prepes[tionNow

Standardotworkabiiity

appraisal

2<

;S5<Lowsegregationresistance

1,7-21.5-l.85Geodworkabi[ity

1,7>

1.5>

H[ghsegregationres]stance

108

6tL,5a4I<.3E･L2

1

3A

A

/

C

EXgr)i{.,.

oBase

concrete

Fig.3.4

Relationship

30

60

90

Time

Cmimute)

between

FlowlSlump

and

Time

-16-NII-Electronic Library Service

2.1,

showing

that

concrete

_prepared

by

mixing method

C,

D

and

F

is

workable,

This

shows

that

mixing

the

cement

and

fine

aggregaLe

first,

mixing

the

cement

and water

first

_,or slightly

delaying

the

addition

bir

the

high-range-water-reducing

admixture can make

both

consistency

and

the

unit water content,

'

smaller.

.

3.1.5

Effect

of mixing method on volume of air

Figure

3.

1

shows

the

votume of air required

by

different

mixing methods.

The

volurne of air required changed

in

the

sarne way as

the

slump values when

different

mixing methods were used.

Although

the

volume of air,

for

-the'

concretg

in

which'silica

fum'e,

fly

ash, and micropowder

blast

furnace

slag were usecl was set at

4

±

]

%

;

it

was observed

that

'the

volume of air

either

increased

or

decreased

depending

on

the

mixing method

'

The

volume _{of air} required

in

_{mixing methods}

C,

D,

E,

_and

F

_{was either equal}

to

_{or slightly}

larger

than

that

fo,r

mixing method

A,

except

in

the

case

of

mix

_proportion

3iFF.

In

the

case of mix

_proportion

3-FF,

a

larger

amount of air-entrai'ning admixture was requirecl

in

order

to

make

the

necessary amount of ai[ equal

to

thai

of other concrete

preparations.

This

is

because

the

ameunt

of carbon contained

in

fty

ash

is

high.

'

3.2

Dynamic

Flowability

of

Fresh

Concrete

''

3.2.1

Effect

of

flow

on

flowability

and

'segregation

Flow

is

discussed

here

be'cause

it

is

suitable

ior

estlmatlng

the

consistency of'concrete with slump values

that

exceed

18cm

lrom

Lhe

results

described

in

3.1.2.

-enxs-"LVaE-]･cox)-oL

108654

3

2 L

3･SP

E

A

cIF

Q

3D

60

90

'

AfteF

addition of'superplasticizing

admixture

T[me

(mimute)

Fig,3.5

Relationship

between

FlowlSlump

andTlme

1Fig.3,7

-m'x2icVaE2enx)oE.

g-".sa

B

3

A

,t

D

c

1,-Acox"L-'at'E2en-..-l9L

9

30.

_se

go

After

addition of superplasticizing admixture

Time

(m]"ure)

'

Relationship

between

FlowfSIump

and

Time

1086543

2

L

3･SF

BA

'

D

c

Fig3.6

P

30

G'O'

90

After

add[tion of superplasticizing admixture

Time

(minute)

'

Relationship

between

FLow!SLump

and

-coxJtu`'a"E2enxl-oL 10865q3

2

,

3･SS

B

A

c

D

Time

Fig.3.8

O

30

.

50

90

+

Atter

addition of superplasticizlng

admixture

_Time

(minute)

'

Relationship

betwee.n

FlowlSlumb･

and

Time

Figure

3.

9

shows

the

relationship

between

flow

and

flowability

(F

value) and

the

relationship

between

flow

and

segregation

_property

(S

value).

As

can

be

seen,

changes

in

the

flow

value

had

agreat

influence

on

the

ftc)wability

of

the

concrete.

The

flow

values

described

a

decreasing

in

_quadratic

curves and

the

segregation valuc:s

becarne

larger

as

the

flow

values

became

smaller.

Furthermore,

the

flowability

ancl

the

segregation of concrete were

_quite

different

for

different

admixtures and mixing methods.

The

flowability

and

the

segregation ef concrete varied widely when

the

flow

values were

less

than

₂₅

cm or

_greater

than

_55cm.

On

the

other

hand,

the

flowability

in

the

c:ase of mix

proportion

3･SF

was unique

:

the

compenent materials

did

not segregate

even

when

the

flowability

was

hi.gh

because

of

the

increase

in

viscosity and

the

Jesistance

to

segregation

due

to

the

large

specific surface of silica

fume.

From

the

point

of view of

the

flowability

ancl

the

segregation

ef

concrete,

the

most

satisfactory

consistency

of

the

high-strength

concrete

_prepaTed

using a

high-range

water-reducing admixture was achieved when

the

flow

was

between

3o

and

50

crn.

3.2.2

Effect

of slump,

flow,

and

flowlslump

on

dist[ibution

of

concrete

composition

To

determine

the

segregation of concrete,

the

difference

in

the

GIM

values

between

¢

ylinder

A

and

trough

C

l(GIM},L,

valuel

in

the

VF

test

can

be

used

to

reveal

the

distribution

of conctete composition.

Figure

3.

]O

shows

the

relationship

between

(GIM),u,

and

flowlslump

(FLIS).

Although

theie

was no clear correlation

between

(G/M}.T.

and

FL/S,

it

was observed

that

_(G!M>,-c

tended

to

increase

as

FLIS

increased.

The

relationship

between

the

slump and

flow

and

(GIM).-c

was not clear enough

to

enable

the

segregation

property

to

be

predicted.

However,

it

was observed

that

the

Iarger

the

slump and

flow

tended

to

be,

the

larger

(GIM),.,

was.

3.2.3

Flowability

and segregation

of

concrete

Figure

3.

11

shows

the

relationsbip

between

the

flowability

(F

value) and

the

segregation

(S

value) of concrete.

Quadratic

curves were

produced

by

plotting

the

S

values and

the

F

values, and

the

shapes of

these

curves

depended

on

the

mixing methed.

The

S

values

for

mix

_propertions

3･SF,

3.FF,

and

3-SS

<with

a microparticre adrrLixtuTe} we[e

between

15

and

25

cm,

that

is,

larger

than

the

S

values of

between

7

and

14

cm

for

mix

_proportiens

:･:･A

and

3･SP

without amicroparticle admixture.

This

can

be

attributed

to

a

lower

resistance

due

to

the

effects caused

by

the

microfiller

effect

of

the

rnicroparticle admixture on

the

chemical and

_physical

surface

_propertieE:

of

fly

ash or

blast

furnace

slag on consistency.

On

the

other

hand,

the

small

S

values

in

the

cases of mix

_proportions

3･A

and

3･SP

seem

to

indicate

that

flowability

due

to

vibratioh

is

likely

to

encounter resistance

to

segregation

due

to

the

steel reinforcing

bars

(partition

bars)

during

placing.

The

S

values obtained

by

mixing methods

C,

D,

E,

and

F

became

smaller, while

those

obtained

by

mixing methods

A

and

B

became

larger.

The

F

values

obtained

by

mixing rnethocls

C,

D,

E,

and

F

became

smaller, while

those

obtained

by

mixing methods

A

and

B

became

larger.

The

F

values

obtained

by

mixing methods

C,

D,

E,

and

F

were smaLler

than

these

obtained

by

methods

A

and

B,

In

_particular,

the

occurTence

of

larger

F

values

in

the

case of mix

_proportion

3･SF

using mixing method

B

seems

te

indicate

that

the

viscosity of

the

concrete

became

high

because

the

specific surface`)'6), and

particle

diameter

of silica

fume

are

larger

tltan

those

of other mineral admixtures.

3.2.4

Effect

of mixing method of

the

flowability

and

the

segregation of concrete

FLguFe3.12

shows

the

re]ationships

between

the

mixing methods

and

the

flowability

and

the

segregation

of concrete,

With

mix

_proportions

3･A

and

3-SP,

the

F

values obtained

by

mixing methocl

F

was small while

those

O8D

ev.

8'E)

6e

o] Ufi 4- > oL 40 )hw

i'

2D

[o

10

20

3D

40 SO 60

F]ow

_{cm)

Fig.3.9

Relationship

between

Flow

Segregation

of

Concrete

7D sa s

_E'E

!e

u,o

ga.

,,.sJt･

G20

op

y

op

o?s cn

and

F]owabiLity

ancl

1.4

1.ee'Asxe

osLt

e

t.O 1,2 ).4 t,6 I.82.e 2,2 2.4 2,6 2.8

Flow/Slump

{FL/S)

Fig.3,10

Relationshtp

between

(FL!S

and

(G!M)...

-18-NII-Electronic Library Service

'

obtained

by

mixing methocl

A

were

large.

Furthermore,

the

F

values

for

3+A

and

3･SP

using mixing method

E

differed

gre.atlx.

On

the

other

hand,

in

the

cases

of

mix

proportions

3.SF,

3.FF

and

3.SS,

the

F

values were

lowest

with mixing

niethods

C

and

D.

The

F

value using rnixing method

B

was

the

largest.

The

S

values

in

the

cases of'mix

_proportions

3.A

and

3･SP

using mixing method

F

were

the

smallest.

Cornbined

with

the

fact

that

the

F

yalues using mixing method

F

were small,

it

is

]ikely

that

the

concrete

prepared

using

thi$

'rnixing

method

became

flowable

in

the

segregated

state.

The

difference

in

the

GIM

ratios of cylinder

A

and

_trough

C

'

in

Figure

3.J3'aLso

supports

this

interpretation,

FurthermoTe,

the

S

values obtained when using mix

_proportions

3･SF,

3･FF,

and

3･SS

varied

for

each mix

_proportion.

Thus

it

was

impossible

to

detect

aclear

trend,

With

rega[ds

to

the

_properties

of

flowability

and segregation

of

concrete,

the

most satisfactory mixLng methods are

C

and

F

in

the

'

case of mix

_proportion

3･A

;

C

and

E

in

the

case of mix

_proportion

3-SP

_;

and mixing methods

C

and

D

in

the

case of

'

mix

_proportions

3･SF,

3･FF,

and

3･SS.

3,2,s

Effect

of mixing method on ratio

of

coarse

aggr6'gate

to

mortar

{GIM},

Figure

3.

13

shows

the

relationship

between

the

mixing method and

GIM.

G/M

varied

depending

on

the

mixing method even when

the

mix

proportion

remained

the

same.

GIM

became

smaller as

the

_preparations

flowed

fr6m

cylinder

A

te

trough

C.

This

tendency

was apparent even

for

clifferent

mixing rnethods.

As

for

the

resistance

to

'

segregation of

the

concrete;

the

smaller

the

GIM

diffeTence

between

cylincler

A

and

trough

C,

the

higher

the

resistance

to

segregation.

Thus,

it

can

be

said

that

mixing methods

A

and

B

p[oduce

a

higher

resistance

go

segregation and

that

mixing methods

C,

D,

E.

and

F

p'roduce

a

loweT

resistance.

As

for

_particular

mix

_proportions,

the

slope of

the

GIM

curve

fo[

rnix

_proportion

3.A

is

steep, and

diffe[ence

between

the

GIM

of

the

cylinder and

that

oi

the

trough

became

large,

reveaiing a

low

resistance

to

segregation.

On

the

other

hand,

the

resistance

to

segregation

in

the

case of mix

_proportion

3･SS

was

larger,

irrespective

of mixing method,

Taking

FLIS

in

Fi'gure

3.3in

3.1.3

as an

index

for

concrete segregation,

FLIS

for

mixing methods

C,

D,

E,

and,Fwas

larger

than

that

for

mixing methods

A

and

B.

The

concrete

_preparations

in

which an admixture with a

la;ge

specific $urface was used exhibited resistance

to

segregAtion

even

when

FLIS

was

2.

Furthermore,

it

is

clear

that

mix

_proportions

3･A

and

3･SP,

neither of which contains

a

microparticle admixture, showed

low

resistance

to

segregation.

These

findings

can

be

seen clearly

in

Figure3.I2.

Thus,

the

evaluation of

_segregation

based

on

(GfM),Jc

is

roughly equal.

to

that

based

on

FLIS.

However,

an evaluation

based

on

FLIS

can

have

a

differe]t

meaning

depending

on

the

mix

_proportion

used, even

if

FLIS

remains

the

same,

as

_pointed

eut

in

3.1.3

and

_3.1.4.

'

'4.

_Conclusion

The

experim.ents stiowed

the

following

:

e.-a)

m=)-as-･")>LOwUhC.--.9b'

tsan

bes an!

tiL8

so70dO 3o ?o

ACEF ACEF ASCD ABCD ABCD

Mix[ng

method

Fig.3.12

Relationship

between

Mixing

Meethod

and

Flowabitity

ancl'Segregation of

Concrete

e)e}

:t5rt

S

_109,ey

:

IS81,S

2e.4di"N

e.

_258o

Fig,

3.

11

-Ex9.9ttL!.o

2o ao

Ga

so

F[owebility

(F

value)

(sec)

Relationship

between

Segregation

and

F[owab.ility

of

Concrete

ezz,

ts!

ttnge

o

E:

-ota

ti8

= e1

E

<:]oE< 1.s 1.oo.lsO.16o.s Types ofeoncrete

3･A3･SP--3.SF-･･--3･FF---3･ss-H-:]-a,'ag

_Q,

N

4t,t1,

t

aj'g'iN'1'K'b

Ril:i?g,eC.T,r?xg2e:c

egc t3c esc eE[ ";c

Fig.3.13

Reratio.nshlp

betwen

Mixing

Metod

and

G!M

O

The

slump varied

according

to

the

mixing

methods,

even

if

the

mix

_proportion

of

the

concrete

remained

the

same.

In

particular,

slump

increased

when

the

high-water

range-reducing admixture was added

later.

2)

The

slumps obtained using mixing Tnetheds

C,

D,

E,

and

F

were

better

than

those

obtained using mixing methods

A

and

B.

'

3)

The

effects

of

the

superplasticizing

admixture

became

_greater

when

the

slump

of

the

_base

concrete

was smaller.

4)

Slump

with

time

values

vary

according

to

the

mixing

method

and

type

ef

mineral

admixture.

5)

No

difference

was observed

in

the

relationship

between

the

slump and

the

flow,

or

between

the

slump and

FLIS,

when mixing methods were ehanged.

6)

The

consistency of

high-flow

concrete with a slump value exceeding

18

cm can

be

estimated closely when

the

relationship

between

flow,

FLIS

and slump are

lower

than

the

lower

limit

of each curve

(Fig.3.2).

7)

The

simultaneous use of

flow

and

flowlslump

was satisfactory

for

evaluating

the

consistency of

high-flow

concrete.

8)

High-strength

concrete

_prepared

using

high-range

water-reducing

admixture

and rnineral admixtures showed

a

strong resistance

te

segregation, even

if

FLIS

was

high

at

between

2

and

2,2.

9)

FLIS

may

be

useful

in

the

estimation of

the

workability of concTete

(Table

3,

1),

The

upper

Limit

of

'FLIS

is

approximately

_2.

10)

The

change with

time

of

FLIS

concrete

_prepared

by

mixed methods,

The

change

with

tlme

of

FLIS

of concTete

_prepared

by

mixing

the

cement and

fine

aggregate

first

and of

that

prepared

by

mixing

the

cement and water

first

was smaller

than

that

of concrete

prepared

by

other mjxLng methods.

11)

The

flowability

ancl

the

segregation of concrete were

influenced

greatly

by

the

ftow.

The

types

of mineral

admixture and

the

mixing method affected

the

_properties

of

the

concrete.

In

particular,

concrete

prepared

with a silica

fume

demonstrated

an

increase

in

viscosity.

12)

Juclging

according

to

the

flowability

and

the

segregation of concrete,

the

flow

at

30-50

cm

_gave

the

most satisfactory consistency.

13)

A

curve similar

to

a

quadratic

curve

was

obse[ved

when

ftowability

values were

_plotted

against segregation values.

However,

the

trend

depended

on

the

mixing method.

Furthermore,

C,

D,

and

E

are satisfactory mixing methods

for

concrete,

from

the

viewpgint

of

the

flowability

and

the

segregation of concrete.

14>

The

VF

test

(the

vibration-type

consistency

test}

was used

because

the

bar

arrangement condition was suitable

for

determining

the

flowability

and

the

segregation

characteristics

of concrete.

15)

(G!M),.c

tended

to

increase

as

FLIS

lncreased,

16)

GIM

tendecl

to

vary accerding

to

rnixing methed, even

if

the

mix

proportion

of

the

concrete

remained

_tlte

'

same.

17)

An

evalution of segregation

based

on

{GIM).L,

is

roughly

equaL

to

that

based

on

FLIS.

I8)

It

was

found

that

effective methods

of

improving

the

characteristics of

high-strength

concrete whose

preparation

included

the

use of a

high-range

water-reducing admixture and mineral admixtures were

the

_preparatory

mixing

the.cement

and

fine

aggregate

first

(in

case of mineral aclrnixture), and mixing

the

cement and water

flrst,

both

being

followed

by

regular mixing.

In

the

case of rich-mix

high-strength

concrete,

it

is

believed

that

an

increase

in

viscosity

for

paste

consgderably affects

flowability.

It

is

_planned

to

continue

the

study

furtheT

taking

into

account

this

_problem.

Acknow)edgments

The

writer would

like

to

express

his

sincere appreciation

to

Mr.

K.

Misu

of

Toyo

Construction

_qnd

to

Mr.

H.

Tanaka

of

Maeda

corp.

(both

_graduates

of

the

School

of

Architecture,

Shibaura

Institute

of

Technology,

in

19s7)

for

their

most

helpful

cooperation

in

carrying out

the

experiments.

References

1)

T.

Uornoto,

Separate

on

Mixing

Methoclsof

Concrete,

Concrete

JournaL,

Japan

Concrete

Institute,

Vot.

20,

No.

9,

pp.

9g-],14

(IL-26)

September

1932.

2)

N.

Miyaji

and

K.

Nakajima,

Influence

of

Mixing

Sequence

on the

_properties

ofconcrete when

Water

Rleducing

Admixture

is