鉱物質混和材を用いた超高強度コンクリートの諸性質に及ぼす要因効果に関する研究

Architectural Institute of Japan

ArchitecturalInstitute of Japan

[at

ll

Journal

of

Structuial

end

ConstructioR

Engineering

EaseM#ftMtsXitNsuEes

uDc:6gl.32:666. g7z

16

(Transaetions

of

AIJ)

No.

400,

June,

1989

eg4ooe

-1gBg:6

fi

'

STUDY

ON

EFFECT

OF

FACTORS

WHICH

AFFECT

'

VARIOUS

PROPERTIES

OF

STRENGTH

CONCRETE

USING

MINERAL

ADMIXTURES

by

Dr.

Eng.

MASAYOSHI

KAKIZAKI'

and

M.

Eng.

KIMIO

OKAMOTO',

Members

of

A.

I.

J.

1.

Introduction

Recent]y,

concTete

of

higher

grades

and more

diversity

has

increasingly

been

required

for

Teinforced

concrete

structures,

including

high-rise

reinforced concrete

buildings,

leng-span

structures, and other

large

structures such as nuclear

_power

_plants.

Due

to

these

requirements and complicated

design

specifications and also

to

irnprove

construction conditions,

the

demand

for

high

strength concrete

is

_greater

than

ever.

Additionally,

there

is

a

_general

tendency

towards

the

construction of

high-rise

urban condominium

buildings

of

₃₀

to

₅₀

stories, and

R

&

D

efforts

aimed

at

applying

reinforced

concrete

construction

to

these

are starting.

'

If

the

strength

of

concrete

is

improved,

several merits can

be

expected,

including

reduction of

the

building

weight and

larger

space

due

to

the

decreased

cross-se ¢

tions

of structural members.

Compared

with steel structures,

reinforced

concrete

strttctures

cause

less

sway

because

ef

their

high

rigiclity.

Numerous

techniques

have

been

developed

for

_pr6ducing

high-strength

concrete,

including

the

use of yarious

types

of materials, vaiious mix

_proportions,

autoclave curing,

_pressure

forming,

the

application of resins,

high-speed

vibration compaction, etc.

Now,

due

to

the

development

of

high-range

water-reducing admixture,

high

strength concrete

for

cast-in-place applications

has

become

avaliable.

Recently,

mineral admixtures such as silica

fume

and alum-type mineral

have

been

attracting attention

because

they

can

improve

the

workability and strength of concrete as well as

its

chemical resistance.

Studies

concerning concrete using silica

fume

from

industrial

waste

have

been

actively

perfbrmed

since about

1976,

rnainly

in

Norway

and

Denrnark,

but

also

in

other

Northern

European'countries

and

Canada.

This

subject

has

been

studied

in

Japan.

as well.

Alum-type

mineral

is

a new

type

of admixture with slightly

higher

SO,

and

CaO

content.

For

this

stttdy, silica

fume,

alum-type mineral and

fly

ash were used with

Lhe

aim of

developing

high-stiength,

high-quality,

cost･efficient

concrete,

and

improving

the

workability of ultra-high-stiength concrete.

The

effects

of

factors

such as

dosage

rate of admixture,

type

of cement,

type

of aggregatei water-to-(cement

+

condensed admixture) ratio, and

dosage

rate of

high-range

water-reducing

admixture

on

mechanical

_properties

and

drying

shrinkage of ultra-high-strength concrete are

discussed.

2.

Test

plan

and

Analysis

Accerding

to

the

_test

_plan,

an

orthogonal

array was constructed,

divided

into

eight

factors

and

three

levels,

'

making

the

shown

in

Tabte

l

(Ln).

Analysis

of variance were

_performed

concerning

the

effects of each

factors

on

various

concrete

properties.

3.

Experimental

Program

･

'

3,1

Test

Details

and

MateriaLs

Table1

shows

the

eight

factors

and

three

levels

in

the

orthogonal array

L..

Fig.1

shows

the

factors

and

interactions

between

factors

which were

tested

(Dotted

figure$

of

Lzi).

r

'

_KAJIMA

_CORPORATION

_Kajirna

_Institute

_of

_Construction

_Technology

(Manuscript

[eceived

J"ne

30,

1988:Paper

Accepted

Ja"uary

20,

l9S9)

-17-Architectural Institute of Japan

NII-Electronic Library Service

ArchitecturalInstitute of Japan

Eaetors A

Types of mineral admixture

Q

X

@

Eacto;sc x Desage rete ot

NNNN,{iri .:llg;{tlij

/A

l

':

i

r

:.

'

l

i

Rl,1,

± , 2t"9 x

N.

@

Factors E S Types o ±eearse

@

@

N@ aggregate

[Cl

x:7t?xTD

g}b.lag;e::.g.,

Fecters s FacLors C Desege rate Desage [ate of

ef mineral suPerplastic ±zing

admixture adMiXtU:e

@

Faeterse

[Ai(C+A]] Error

Fig.1

_Factors

and

Interactions

between

Factors

Tested

{Dotted

figu[es

of

L,,)

(O

:

Column

number

in

orthogonal

L!,)

Table2

Physical

Properties

of

Cement

Tablel

Factor

and

Level

LeveL Faetors 1 2 3 M[neraledmixtureKind(A)Aturn-typeminerel,FASiEicetumeFS F'lyashFF DosagerateB XO,4 Xl,O'1 Xl.5 WCD)

C+A O.29

e.35

O.45

TypesofcementCF)Highear)y-strengthcementCHOrdtnerypoTt-_{landcement,CN} FIyashceme

_(TypeA)CF

Typesefcearse eggregeteCE)NatufalaggregateGRCrushediaggfegateGCArtifieialFight- aggregste Dosegereteofsuper-p]esti-cilingedrnittureSuper-plesti-[C)cizing.ad.XO.5 Xl,O'2 Xl.5 Re-svperplesticFiingad.(G)XO.5

Xl,O'2

Xl,5 CendLtionOtonrete ettermix[ng'

{O-･50minutes)(H)Stetlc

SteticL StFr Notes`1

'2

J3

F/ght--vteigtu

GL

Standarddesege rate :A)urn-type----･-2.5%[･f

(C+A)

co-tent

:

S"ica

tume,Flyash･-･･12.5% ot CC+A) :ontent Standarddosage rete;Chemicaledmixfure]t(Cement + bMneraladmlxture)

=soo/looCctikg) Chemiceladmlxfure

eAir-entreining edmi:ture :3D3A

Fedueing admlxture 1NL-14Se

eSuperplastic[i[ngadmixture,:NP-10

Table3

Physical

Properties

and

Fineness

of

Fine

TypesefcementSpecific9ravity SpectficsutfacetBlaine(cm:lg)1day]day7dayZedayKIpusMsk:rtwmS;IEtmm)Spctlr;[grsv;:yYia+trebserplltnce{)LessinNashlns#estcta)Oreanic-mp"T:lrsurLd!"sitYCLgJ1)Pet[cnL-gdstl:d･wedvme{re;FinenessmDdvru!CempressivestrengthCKgflem:)

Aggregate

High-early

strength1.14q3Eo1362se36e4S6Htlvn]tagrte-LoCort;vor}sISIt.fi6O.94tLrc1,7;'ce,s1.90

Prdina;yportland3.163140

-1372]E419

Flyash(typeA)],os]1]O

't24221175

Table

2

to

₆

show

the

_physical

_properties

of

the

cement and aggregate, and

_physical

_properties

and

chemical

analysis of

the

rnineTaL admixtuTes, air-entraining admixture and superplasticizing admixtuTe.

3.2

Mix

Proportions

After

the

trial

mixing,

the

amount of water

fQr

the

mixes was

determined

by

cheosing

thequantity

_giving

aslump of

8

±

1.5cm

using

the

standard

dosage

rate of

high-strength

water-feducing admixture.

Then,

_the

dosage

rate of superplasticizing admixture was

chosen

to

inctease

the

slump

of

concrete

mixed with

this

anneunt of water

to

about

18cm.

The

water content varies

by

type

of cement and water-to-(cement+condensecl admixture) ratio i[WIC+A),

Sand-agg[egate

iatio was adjusted

to

_get

workable concrete, and air-entraining admixture,

dosage

rate was

that

which

_gave

4

±

1

%

of air content

for

superplasticized concrete.

Table7

shows rnix

_proportions.

3.3

Test

Methods

Table

8

shows

the

_test

methods

by

item

tested.

_Mixing

was

done

as

shown

in

the

flow

diagram

(Fig.

2).

Silica

fume

was used

added

as a

slurry.

A

mixer

of capacity

100

t

was used

for

forced

stirring.

4.

Experimental

Results

4.1

Compressive

Strength

of

Concrete

1)

Effect

of

Factors

on

Compressive

Strength

Table

9

shQws

the

analysis of variance on compressive strength

for

each

factor

at age

₂₈

days,

Fig.3

$hows

the

relationship

between

the

various

factors

and

compressive

strength

for

those

factors

significant

at

the

1

%

or

5

%

levels,

'

(

a

)

Effect

of

Water-to-(Cement

+

Condensed

Admixture)

Ratio

Architectural Institute of Japan

ArchitecturalInstitute of Japan

Table4

Physical

Properties,of

CoarseAggregate

.KindsMaximum's"zeCmm),SpecificeravityWeterebsecption(%･}Loss/inweshingtest{oA)Bulkdensity.{kgtI}Percentagfsolid･

velume%},

Naturalcearse,252.65O.63,O.10L716s.e

eggregeteCrushedlstone 202.S4'O.72O.101.58'50.3 Artificieltight-weightaggreeate151.57'･28.7O.20O.78160.1

{Mesaraito),

Nptqs.1) Naturee ceerse aggregete

(Oi

eiyer):

Size

30-20

･

Ratio

10%:

2)

Crushaj

stone

(Oume):

Table5

Physical

Properties

and

Mineral

AdmixturesChemica+analysisCOIo)

KindsSpec]f[c'gravltySpeciflcsur--

_{faceCcmilg)sio,Al,O,caoso,}

Alum-typemine[al-2.958,340.7103.432,650.4

Silicafume2.Z322'O,OOO92.3O,2O.3-Flyesh

2.243,02053,5.25,56.7O.6

Table6

Physical

Prepertiesof

Kinds･PrincipalingredlentSpecificgravlty(20

℃

)pHExternalappearance

･Air-entraining

admixtureAlkyleryssulfonate(aniem)ctype surflctant)

Liquid'of1[ghtyellow

High-range

water-reducing admixture

Sultonateof

highcon.den-sationaromatlc1.18-1.227-8Liquidofdarkbraun

Svperp]astjcj2jng

admixtureCompositeot naphthaten-sultonate･ te

1.17--1.197-9Liquidotbleckbraun

The

effect.of water-to-{cement

+

Ievel

for

each

age,

Compressive

strength

Water-to-(cement

+

condensed admixture)

foltowed

by

type

of coarse aggregate water-to-(cement

+

condensed

admixture>

age

7

days,

and about

5-16

%

The

rate of

decrease

of compressive strength with

increase

larger

for

age

7days

than

for

age

The

compressive strength at age water-to-(cement

₊

condensed admixture)

{

b

)

･Effect

of

Coarse

Aggregate

The

effect of each

type

of coarse aggregate on compTessive strength was

significant

at

the

1

Cornpressive

strength

is

largest

for

crushed-stone

and

17-25

%

largei

than

for

artificial-lightweight-aggregate

pronounced

with ages, and results

in

an

increase

of strength w at compressive strength at age

28days

for

each

{Type

I)

is

closest

to

its

91-day

,2S--10,15-5mm

,35%:

55% Size

25-10;

!S-5, 10--5,nm Ratio40%: 45%: 15%

S

m

Chemica'I

Analysis

of p U c o u m

g･

L

vr

g

･8

_-H

Chemical

Admixtures

.

p en

g

g

ft

Ok tuU n=

.po.

L

･

Fig.2

Mixing

Procedure

'

'

'

condensed admixture) ratio on

compressive

strength was

significant

at

the

1

%

'

increases

as

water-to-(cement

+

condensed

_4dmixture)

ratio

decreases.

ratio

is

the

factor

which

has

the

Largest

effect on cbmpressive strength,

,

and

type

of admixture.

Compared

with

the

strength at age

28

days,

for

all

ratios

the

values of compressive strength are about

_20-25

%

smaller

at

Larger

at age

91

days.

in

water-to-(cement

+

condensed admixtvTe) ratio

is

91

days.

This

tendency

is

similar

to

that

of

ordinary

high-strength

concrete.

28

dqys

was about

700

kgflcm2,

630

kgflcm2

ancl

450

kgflcm'

for

the

values of

ratio,O.29,

O.35

and

O.45,

respectively.

Type

%

level

for

each age.

concrete

:

10-13

%

larger

than

foT

natural-aggregate

concrete,

concrete

(Type

I).

This

tendency

becomes

more

hich

'almQst

agrees with

_previous

studies2)･`).

Looking

type

of concrete,

that

of artificial-lightweight-aggregate, concrete

strength, reaching

82

%

ol

this

value.

This

is

followed

by

naLu[al-aggregate

'

-19-Architectural Institute of Japan

NII-Electronic Library Service

ArchitecturalInstitute ofJapan

Table7MixProportion

efConcrete eg:i'

;,･,l{

AW

A

-:ESh:e

m'o"tugZog)teMPeco

ggo?ts.i98eEs/a(e/e)

-tss.;･s

(kgVr.3)

=-['pLSss?e;･g-g:,.+`agBE<ibeRs-?to.--xtf,2,3:/･g'E.og-

glg.tu'Zm?

;g:･,k･*

.esE

Ne,C+AC+A(e/e)

1

1.0CHGR3217815.0O.302.5

6

O.292.5CNGC36r7712.0O.207.5

8

4.0CFGL3616212.0O,505.0

2

1.0CNGC3915210.0O,165,O

4

O.352,SCFGL3915010,OO,162,5

9

oah-tNEw2,E`[E

FA

4.0CHGR3515512.0O,30Z5

3

1.0CFGL421458.0O.107.5

5

O.452.5CHGR3815010,OO.205,O

7

4,OCNGC4'21488,OO.102,5

10

5.0CNGR3314012.0O.402,5

15

O.2912,5CFGC3718012,OO.607.5

17

20.0CHGL3122515.0O.705,O

11

5.0CFGC4015010.0O.405,O

13

_{O.3512.5CHGL3518512.0O,50Z5}

18

ee.8di-FS

20.0CNGR39.19010,OO,707,5

12

_{5.0CHGL･3616010.0O.307.5}

14

O.4512,5CNGR391708,OO,405.0

16

20,OCFGC･432008.0O,702.5

19

5.0CFGR3414012.0O.30Z5

24

e.2912,5CHGC'3417015,OO,347.5

26

20,OCNGL3515012.0O.405,O

20

5,OCHGC3716512.0O,305.0

22

O,3512.5CNGL3815510.0O.202.5

27

S:z

FF

20.0CFGR3712510.0O.327.5

21

5,OCNGL411578,OO.107.5

23

O.4512.5CFGR401308.0,5.0

25

20.0CHGC405S10.O.32.5

Notes*

Pure

Solution

TableBMethod

ofTests

concrete

and

then

ctushed-stone con-crete.

At

age

91

days,

the

differences

in

strength

are more

pronotrneed

than

at age

7days.

The

strength

of

crushed-stone

concrete

is

the

largest,

followed

by

natu-ral-aggregate

concrete,

and

then

artifi-cial-lightweight-aggregate

concrete

(Type

I),

The

differences

between

the

com-pressive

strength of artificial-ligh,tweight･ aggregate concrete

(Type

l[)

and

the

eompressive

strength

of

natural

aggregate concrete and

crushed-stone

conerete

be-come

larger

with

ages,

This

is

caused

by

the

interaction

between

the

strength of

the

aggregate

itself

ELnd

the

strength of

the

cement-paste mortar

because

_the

breaking

strength of

the

artifieial

light-weight aggregate

itself

is

lower

than

_that

of

the

mortar3)･4}.

Testitem

TestmethodSizeof'speclmenCcm)

'Curxn9method

Age

i

CompressiveJISA

10

¢x20

tn:e=

strength

1108

kVuapoptm=-epTensile

JISA

lodix3e

Standardcuring,7,2B,91

UkV>vo.Hu}Estrength

₁₁₁₃

temperature

days

mmoom-･-Elastic

ASTM

1Odix20

2o

±

3ec

k-VncoopErt"modulus

C469

oo-uem

{Qc=113)

Change

JISA

1OxlOx401)Cur

±ngattheage1)Lengthat

o of

1129

of1to7days: age7days:

x

length

Standardcuring

stande.rd

xfi'

2)Curingafter7

Iength

e

days:20OCand2)Sterage

uttr

601R.H.

_perioC[:1,4,

fi'

_8Cweeks)'

"ts

3,6Cmonths)

Numbero[

spec-'lmens

162

164

164

81

(c)

Effect

of

Type

of

Admixture

The

effect

of

type

of admixture on

compressive

strength

was

significant at

the

1

%

level.

Although

the

developrnent

of

compressive

strength

of

fly-ash

concrete

is

slow

to

begin

with,

it

increases

with age.

On

the

other

hand,

for

alum-type-mineral concrete,

the

development

of

compressive

strength

is

fast

to.begin

with, and slows

down

-20-Architectural Institute of Japan

ArchitecturalInstitute of Japan

rgtsytv=-da=o-Pv]

'tu't:flaEoU

900

800

700

6oe

500

400

300

-x:Si.gnificant

at

O.Ol

i

:Confidence

limit

ef

O,95

ix.'x

+N

'

kl,1xtx IX ･eE

l'

lxt

1,

x

'

,IL,N

xxxx

Xl

xi

---

Age1

7

clays

Age[28

days

--

Age]91

days

ix

l

'

}-+xyx

_l-i'l

PDpulatien

mean --xx x

+x

N+-$,

}-+{

'

x

Admixtures

OFA

OFS

xFF

Interaction

Interaction

AxB

AxC

xx

l ix

llx

2g

3s

4s

GR

GC

GL

FA

FS

FF

XD.5Xl.OXI.5'CH

CNCF

Xo,4xl.exl.6xD.4xl.oXl,6XO.5Xl,OXI.5

Uel(C+A)S

Coarse

Mineral

Dosage

Rate

of

Cement

IV(C+A)

IV'(C+A)

Dosage

Rate

of

aggregate adrniFture superplasticizing

SuperplastLcizing

admixture admixture

Factors

and

LeveLs

Fig.3

Effect

of

Faclors

on

Compressive

Strength

Table9

Analysis

of

Variance

on

Compressive

Strength

(age

:

28

dags}

FactersSumofsquaress

greeseffreedomeVarianeevVarianceratioFo

A

3454B.oo217274.0011.46**

B(M(C+A))17538.002

B769.eO5,82** AxB

9272.004

2318,eO1.54

C

44982.00222491.0014.931*

AXC

18152.0e4

4538.003.el*

DCSVI(C+A))526700.002263350,OO174,B7**

E

172520.0e286260.0057.25#eF

F

glgo.oe2

4595.003.05*

etError49722.0033 1506.721.00

Tota18826en.OO53

-

-e>-H tuM >Hm"mvka coE r"ove tsgg qo

"tu aspm･as =--: tao:u tu"koptu ua 120

100

BO

60

A/(C+A):O.4-1.6

_t

times

.pt

t"t .-'

;..o

"J'

=x-J or-J-/JJ-/1'Aium-typem ±nerai

/

o

Siliea

fume

x Fly ash OW ±

thou't

admixture

F(2,33;O;el)==5.31

F(2,33;O,05)==3,28

F(4.33;O.Ol)=3.95

F(4.33;O.05)=2.66

**Signifieant at

O.Ol

*Significant at

O.05

Analysis

of variance was marie

by

peel errer e' when value of

Fo

is smzll.

7

2SAge

{Days}

91

Fig.4

Cornparison

with

Cempressive

Strength

at

Age

28Days

for

Concrete

with

Different

Admixture,

Types

with age

(Fig.4).

Burning

alumstore

IKA

I,.(SO,),(OH),l

in.a

furnace

_produces

non-crystalline alumina and

frietallic

sulfate

double

salt.

These

hydrate

with water and colciuTn

in

the

cement, causing

the

ixcrease

in

strength of

alum-type concrete

in

early stages.

This

enhances

the,hardening

processof

the

concrete5].

The

compressive strength of silica-fume concrete at age

7days

is

almost

the

same as

that

of

alum-type-mineral concrete.

However,

for

the

ages

28

days

and

91

days,

the

strength of silica-fume concrlete

is

larger

than

that

of

fly-ash

concrete and alum-type-mineral concrete

by

6-10

%

and

3-4

%,

respectively

{Fig.

5).

The

strength of silica-fume concrete

increases

with age

because

of a

_pozzolanic

reaction and

hydrationof

fine

silica

fume

_particles,

_producing

Ca

{OH)t.

This

causes an'increase

in

volume of calcium silicate

hydrate

with age6)N").

(d

)

Effect

of

Interaction

between

Admixture

Type

and

Dosage

Rate

of

Admixture

The

effeet of

the

interaction

between

type

of admixture and

dosage

rate of admixture on coTnpressive strength was significant at

the

1

%

level

at

age

7

days,

and

at

the

5

%

level

at

age

91

days,

In

other

words,

the

optimum

dosage

rate of

the

admixture

for

high

strength yaries

by

type

of admixture.

This

is

_presumably

because

the

unit water content

.varies

by

type

of

admixture

and

dosage

iate of admixture as shown

in

Fig.

6.

The

compiessive

strength

of

silica-fume concrete

is

_s

to

_lo

_%

larger

than

that

of

fly-ash

concrete with a

dosage

rate of ×

O.4

to

×

1.

6･

for

ages

_7days

and

'

'

-21-Architectural Institute of Japan

NII-Electronic Library Service

ArchitecturalInstitute ofJapan

o･Z

.$

trfl

vg

ge8v..

govg

nd8fsg:

fl8v.

Fig.5

130

120

1OO

BO

g

:t

I･

l

240

220

200

180

160

140

120

GRocGL

60

7

28

91

Age

SDayp}

Comparison

with

Compres$ive

Strength

_of

Fly-ash

O

2

4

6

8

₁₀

_12,

₁₄

₁₆

₁₈

20

Concrete

at

Age

z8

Days

for

Concrete

with

Different

A/(C+A)%

Admixture

Type

Fig.6

Relationship

Between

Af(C+A)

and

Water

Content

2s

days.

_(Strength

foT

closage

rate of admixture ×

1,6

at

age

91

days

was

excluded.

)

The

reason

is

that

the

specific surface _{of silica}

fume

_per

_{unit weight}

(approx,

_{220,OOOcm'lg)}

is

_about

_73times

_that

_of

_fly

_ash

_(lappTox.

3,

o2o

cm21g), making silica

fume

more reactive

than

fly

ash, so

3CaO-SiO,

(alite)

is

_procluced

during

hydrationiO}･ii)

The

strength

of alum-type-mineral concrete wlth

dosage

rate

of

admixture ×

1.

0

and ×

1.

6

at age

7

days

is

5-10

%

largeT

than

for

fly-ash

and silica･fume concrete.

However,

at ages

28

days

and

91

days

it

becomes

almost

the

same

as

that

of

silica-fume

concrete.

The

compressive strength of alum-type-mineral

concrete

is

largest

with

the

dosage

rate ×

1.

0

(Al(C+A)

==2.

5

%

)

at

any

age.

On

the

other

hand,

the

concrete strengths with

dosage

Tate of admixture

XO.

4

ancl ×

1.

6

are

almost

the

same,

being

_8-15

%

less

than

with

the

standard

desage

rate.

2)

Relationship

between

Average

Estimated

Compressive

Strength

and

(Cement

+

Condensed

Admixture)

-to-Water

_Ratio

_for

_Each

_Age

The

process

means of compiessive strength ovei various

factors

and

levels

for

each age

is

_given

by

the

following

equatlon

:

Pm=

£

(HO-(Tal

×

(th-1)"'-""-"'m-'"H-'-H"-''--''''""'""-'--'''"''-''''''"''--"'m''''<1)

Where

P.:Values

for

estimation

of

the

_process

means

Hh

:

Averages

values

for

non-negligible

factors

Ta:Total

average

L(r

:

Number

of

non-negligible

factors

Table

lo

gives

the

values of

confidence

limits

of

95

%,

Here,

"non-negligible

factors"

mea[Ls

factors

which are

judged

significant at

₁

%

or

5

%

levels

and with contribution rate

(p)

5

%,

Table

11

shows

the

values

for

estimation of

the

_process

means.

Figs.7-9

show

the

relationships

between

(cement

+

condensed admixture)-to-water ratio and compressive strength _at

ages

28

days

for

variotts

factors

and

levels

(type

of coarse aggregate,

type

of admixture and

dosage

rate ef admixture).

The

figures

_{were estimated}

from

_the

_{average values}

_in

the

tests.

In

each

figure,

compressive strengths are shown

for

three

values

of

(cement

+

condensed admixture)-to-water ratioiT),

The

results show

that

the

increase

in

strength

is

small

in

the

high-strength

region

for

any coarse aggregate and

for

any

admixture.

With

the

same

(cement

+

condensed admixture)-to-water ratio,

the

compressive strength

of

crushed-stone

concrete

is

larger

than

that

of natural-aggregate concrete.

-22-Architectural Institute of Japan

ArchitecturalInstitute ofJapan

Table10

Estimation

of

Vatues

of

Population

Meansfor

CompressiveStrength

e at

StrenBtb

Facters

eliva=euxntu,H ¢ nevxvE--es

tuL"preokX,H"sOMi:tuv+crooMv8B>CAo<,H+uUUvOs.-<e"abfiqe=a "Ho rd1NO.-kk-Hkv v05U Oza1-HVdi ee=VXLn tuutut.Heo mndgvN e"--Ve< ne.atuHv Ug"otu ¢ oomuao--"adieocoheLev"

xpmaUvaeh-eu

Ast+'"tueevws.3 ce.-.･el<"+UVA-tu.)5--q<Hv FAFSFFXO,4Xl.OXI.6XO.4Xl,OXI.5XO.5Xl.DXI.5XO.SXt,OXI.5SRac"[HCNCF2915-S?9]SfiS 60Dtt-P=4Zp=ozwp=3ZP.OZ}P.12-Ph9XMP.IIZ-.FP.6SZPhOZ

'

(Kgfl:m2)

an5DOA

FA

_FA

FS

FAFSFA

tua7qAv. vpt

FS

s

.--cuE

_FF

FF

vYig 400 asuv=･(Kgffcm2)--P.4Z"-P.2Zpsez.--P=SZ-P=IZ-"P.19ZP=IX-}P!iS9Xp=oxx out=: 7oe

FS

FS vmqzaw

FA

FA . ov6au

,:co59SAV.

mpamU-FF

FF

ae 500

'

oU 2-"P=2Z"P.IX-P"2Z-tP.4XP=-ZwwP=34XPeIXMP.47Zp=-z

CKgfl:m)eao

m

FS

h7ogca

FA

vSE6AV. -a

FF

600

'

NnE<-hm-iA-ge:::.:opu-nEev

T50 7ee 600 500 400

XO.4 tudosageXl.5:fDosage cohtentXStandard

centenL) Ratte af mtneral aawttxture Dosageeententeisuperplaet ±c ±alngamxtnre usedgesaboutSOO

¢

cper1ODKg/rm]cement.tt-" "-.vv-'-rtso:1.f.-tffL`."f'

't-//

-L"".y'.vkh1"be1N.Xl

･"4ttx,t'/'

,i'/Zi"/'/'

'(6･$s･.

...z-V'rxx..7'ttI'e---Aluni'type mLnefal

HSj1icafume

b.vN' X---XFIyesh

'JASSS(K=400kglrf,Nerma)veeightconcrete)

q=244C/W-t36CWt40--70S)

N-Evx-.gEue::y'a:itEeU

XO.4 NdosageXl.-6:{Dosage cententlstandnrd eentent) Ratie of mineral. admixture

3502 z22 2.s zss 3,o 3.4･43.s

2,1

2,22

Z5

2S5 3.0

3.44.

3.s.

{C+A)/W

CC+A)/W

Fig.7

Relationship

Between

(C+A)!W

and

Compressive

Fig.8

Relationship

Bet-reen

(C+A)fW

and

Compressive

Strength

(Normal

weight concrete,

Age:28

days)

Strength

(Crused

stone concrete,

Age:28

days}

'

The

relationship

between

the

(cement

+

condensed admixture)=to-water ratio,

<(C+A)IW),

and compressive strength, a,,

gan

be

expressed

by

the

following

equations.

ac=S[{C+A)IW]+T+aee ±

N

(kgflcm!)･-･L-･･---･'-･･"'-･---･･･--･"･･-'H'H''"--""""-'-"(2)

Where

23

85DesegecontenteflsuperpleBttciEing.admtxture

usedwasabout500ccper100Kgtm]cement.

80

-'''r- --?7g"-ts1 x/t-/-. /C:-/ 70 7-XJ

'.v"F..1

I.77`t"'bv',.'i'

.,..g.t2?iilf/z2f

'7

([Ct16

'/

J

60 _IX

e･/Le;<1,ttN･'

e-{acSiMcaAlurn-type mineralfume

500

la"･->-"-><FlyEsh

450

Architectural Institute of Japan

NII-Electronic Library Service

Architectural Institute of Japan

::ggg,:

:gAl3::?s:g:,:e:;":l:g;."",d:tha,.,...

7oe E

a

...

.A

₅₀

lt

_E

/S600

i/-`5

cs,lt..f/"1:

l

tk

40

Gp

...;"-'.

l3;ilG(y,

jLg

5DO

i

/-

i,

5

..rt,..6k":'

_.

"'

"

,tik"aSL'"

4oo e2s

3oo

･4ob

soo 6oe

7oo

･soe

･Cempressive

strength

(agVem')

Fig.10

Relationship

Between

Cempressive

strength and

Tensile

Strength

300

'Z85

3,O

3.44

3.5

2,1

2.22

2.5

CC+A)/W

Fig.9

Relationship

Between

(C+A)IW

and

Compressive

Strength

(Light-weight

aggregate concTete,

Age:28days)

'

S

T:Values

of

constant

,

a!e=aF:s+a6ts+as2s

:

Sum

of

constants

for

each

factor

and

level

at age

t

days

ans:Constant

determified

by

dosage

Tate of

adrnixture

at agetdays

acts:Constant

determined

by

type

of coarse aggregate

at

age

t

days

a.,,

:

Constant

determined

by

dosage

content of superplasticizing admixture at age

t

days

±

Nkgflcm2

:

Confidence

limits

of

95

%

Table11

Values

for

Estirnation

of

the

Process

Means

{Z

Included

values-Ornitted vatues} Dosagecententoteuperplast ±ctzingEdmSxture usedvasabout500ccperleOKg/micement.'

$"･es

''''t-'"

'

- '-'x1 7"

'"/'

pt"$""･

t'.7gN2.7 /bi7"'-'/'

'

/'1i1ll[',io.7r7

Zii.2gCNp

'.".Y7

/

i

J

$ss

e--AIum-type

rnineral

ouSiticafume

.1<"lo

x---xFlyash

A-Valuesofnon-negligiblefactors

".

Item

Wf(C+A)

s

,E4'o=

-LevelA,Af(C+A)(Z)(z)cG

e

First

Second

r3.

IFA1'FA2.5'FA4'29CHGRxo.s

xO.5senpO"=

:G8a'fov"m,HIJ

Properties

IFS5'FS12,5'FS,2035CNecxl.O

xl.e-Hsg

£

･z:･vV･HceO-Ho-Age

mFF5'FF,12,SFF,2045CFGLxl.5

xl.5

I462:5181Ls02566S26468FAFSFF

Max.

-i

:

480477447'

737

-TT---rT-

-LT'

-

'

7

1_l l b

daysE510l'481I146750746351850S464497

1896Min.

32

..h

_:

' 173 pt

t---1

'-"+

--T

.

E '

t

Ux

_{m478:419i'430349433436496519432}

- 1 _d co ) ' M '

'

v ' 1 =

IS83:b630!588696

S88576599518

Max.

"co

:

:,

908

g28

..i-[----

'---BdaysI6441639:S88629

66861258SS67

1786Min.

39

m

_･li`i

_2S8

"

-v-t+--Ld

'L---

L-)

'

/

's

_{uS83:S681535461}

530613686602

m

:

1 o ' k / a

i

d

g

I6S3:701･!639749

665

638

Max.

v

l

;

943

-t

,

-

----t---L

91

:

_:

daysI727ll691,,648707

759

6S5

1977Ntn.

36

L 1-""

₃₇₃

L

--1b

'.--+---L---'L`--m639:l641!!652541

₅₇₂

₇₀₄

1

Notes:

Max,

st. =

Maximum

strength

Min.

_st. =

Minimum

strength

Architectural Institute of Japan

ArchitecturalInstitute of Japan

rgtsy8U-E･

.:

g,

5

4

3

2

1

KN

xt

(+)t

Ii1

*lt{t

:Signiiieant :Confidence

g･sx

.t.

xil

ss. St

L

NSr-Population

at

o.ol

coos)

tlmit

of

O.95

e-+-aeeptx.t."all

S-mean

Interaction

AxB

S--t-'""

K-.

-}t".-tll

F--t--l

''---Age:

7

days

Admixtures

.Age128

days

O

EA

'･--Agel91

days

O

FS

x

FF

'

GR

ec

"

Coarse

.aggregate

Table12

Analysis

of

Variance

on

(age:28days}

29

35

45

EA

FS

EF'･

wr(C+A)S

Mineral

admixture

Factors

and

EFFECT

OF

FACTORS

Fig.11

Effect

of

Facters

ElasticModulus

FactorsSurnetsquaressegreeSeffreedamdiVarianeevVartanee'ratloFe

ABCAt((-ChA)]

AXBDCVV(esTA)]

EFeiError

e.o2O.18O,422.1927.95O.03O,74'

22422239 O.OlO.09O.l1'1,0913,97O.OlO.02

O.504.50*5.50**54,50**

69B.SO**O,501.00

Total3L5353

F(2,39:O.Ol)=5,19

F(2,39;O,05)=3.24

F(4,39;O.Ol)=3.S4

F(4,a9:O.05)=2.61

**Significant at

O.Ol

*Significant at

O.05

Analysis of variance was made

by

peol error et

when'valve

ef

Fo

is

sTnall

Tablel

13

Analysis

qf

Variance

on

Drying

Shrinkage

(age:6

months)

CE{

CN

CF

xOAxl.Oxl.6xO,4xl.OxL6

Cement

A/a[C+A)

A/(C+A)

Levets6N

ELASTIC

MODULUS

on

Elastic

Modurus

4.5z)4n.-3,sx

-emM3EJve

2.5v

tsT

, 1,5 .

es

e

GL

. ee

-tbl

-r-O.ofSiOe

Se

tw

vte-FactorsSumefsqllaressDegreesof

freedomdi･VariancevVariauceratioFo

A

12.03

2

6.0213.3S**

B(M(C+A))24.B7

212.4427.64**

AXB,

3.12

4

O.781.73

C

12,09 2 6.0413,42**

Dpm(C+A))22.fi2

21L3125,13**

H

1.56

1

1.563.47

E

85.63

242.B295.18**

etError 16,5 37

O.451.eo

Total1T8.4252

F(2,37;O.Ol):=5.22

F(1,37:O.05)==4.11

F(4.37:O,Ol)=3,88

F(4;37;O,05)=2.62

**Significant at

O,Ol

,

e'

is

shcrwn tn

table

12

aggregate

types

and all w'ater-to-(cement

₊

compressive strength and

tensile

strength

for

condensed admixture) ratio and cement

type

can

The

700kgffcm!

kgffcm'650

kgflcm'

The

types

of admixture used are silica

fume

and alum-type mineral

4,2

Relationship

between

Compressive

Strength

and

Tensile

Strength

Fig.

10

shows

the

relationship

between

the

compressive strength

(a,)

and

tensile

strength

'(ot)

of

the

concrete specimefis.

As

the

figure

shews,

tensile

strength

increases

with compressive

strength.

This

is,true

for

all coarse

adrnixture) ratios,

The

_general

relationship

between

including

admixture

type,

water-to-( ¢

ement

+

by

the

following

regression

eqliation

:

.3oo

4oo seo 6eo 7oo

seD

Compressive

strength

_Cac,kgfftmS>

RELNrlONSH]P

BETWEEN

ELASTIC

MODVLUS

AND

ComPRESSIVE

STRENGTH

Fig.

12

Relationship

Between

Elastic

Modulus

and

'

'

Compressive

Strength

compressive strength at age

28

days

with

water-to-(cement

+

condensecl admixture) ratio

30

%

is

appox.

for

natural-aggregate concrete, appox.

800

for

crushed stone con ¢rete, and appox.

for

artificial-lightweight

concrete

(Type

I

).

condensed

all

factors

and

levels,

be

expTessed

Architectural Institute of Japan

NII-Electronic Library Service

ArchitecturalInstitute of Japan

at=O.047 a.+11.35

{kg

£

fcm')

･･･-･････-･･･-････-･･･-･･･-･･････････--･･-･･････-･･･-･･････-･･････-･････-･･･････････････-･-･･･(

3)

where

Coefficient

of correlation=O.

968

The

ratie

tensile

strengthlcompressive strength,

(

atlel,),

is

ll14-ll16

for

compressive strength

500-800

kgflcm!.

The

reiationships

between

the

compressive

strength

and

tensile

strength

of

concrete

for

different

coarse aggregate

types

is

shown

in

Fig.10,

If

the

above

test

results are

fitted

to

th=1.6VE, which

is

the

_generally

assumed relationship,

the

best

approximation

is

Eq.

(

4

_>,

However,

this

equation

underestimates

the

value

of

tensile

strength

for

compressive strength

below

550kgflcm',

and oyerestimates

ten$ile

strength

for

compressive strength over

550kglc;m'.

th=1.6ViF･-･--･-･--･----･----･-･-･---･----･---･･･---･-･-･･--･･･-･-･-･---･---･-(4)

4.3

Elastic

Modulus

o{

Concrete

1)

Effect

of

Facters

on

Elastic

Modulus

Table

12

shows

the

analysis of variance on elastic modulus

for

various

factors

at

age

28

days.

Fig.

11

shows

the

relationships

between

elastic modulus and

the

factors

and

levels

which

were

juclged

to

be

significant at

the

1

%

or

5

%

levels,

Water-to-(cement

+

condensed

admixture)

ratio and

type

ef

coarse

aggregate

have

a

great

effect on elastic modulus, while

there

are no significant

differences

by

type

of

admixture

er

dosage

rate

od'

admixture.

2)

Relationship

between

Compressive

Strength

and

Elastic

Modulus

Fig.

12

shows

the

relationship

between

the

comp[essive strength

(

a.) and elastlc modulus

(E,)

of

_the

conciete

specimens.

The

elastic modulus

increases

with compressive strength.

This

is

true

for

allcoarse aggregate

tlfpes

ancl admixture

types.

For

compressive strength of

500kgffcm2,

the

elastic modulus of natural-aggregate

concrete

is

the

largest

at approx.

3,7

×

105kgflcm2.

The

value

is

appTox,

_3.2

×

105kgflcm'

for

crushed-stone concrete,

and

is

smallest

at

approx.

2,

1

×

105

kgflcm!

for

artificial-lightweight-aggregate

concrete

<Type

I

).

The

general

relationship

between

eompressive

strength

(

a,>

and

elastic

modulus

{E,}

for

all

factors

and

Levels,

including

type

of

admixture,

water-to-(cement

+condensed

adTnixtuie)

ratio

and

type

of

cerrient, can

be

expTessed

by

the

following

regression

equation:

,

Ee=(1.52+O.O03a,)

×

10S

(kgflcmi)''''''''''''''''''''''''-'''''''--''''･'''''''･''''''･"''･'････r-･････-･･-･･-･････････(5)

where

Coefficient

of correlation

=O.

985

The

relationships

between

cempressive strength and elastic modulus

for

different

types

of coarse aggregate

is

shown

in

Fig,

12.

The

values of elastic modulus obtained

from

Eq.

(

5

)

are almost

the

same as

the

va]ues obtaine/d

from

the

standard equation

for

reinforced

concrete structures using

2.3tlme

as

the

air-dry unit weight,

4.4

Drying

Shrinkage

of

Concrete

7..

6T95szzS4.se

¢

_3pat:ba2 1 ' i/'/ lttl L

-l /Signifieant at

O,Ol

---Age/S

Uleeks

;

/Cenfidcnee limit of o,gs

'Agc:6

Mo]tbs

tr tt

:

l"t, ff L11Ns :I

:

.l/I"

ls.,/'

Pepulatien

meen

/"'

l.

GRGCGLxO."xl.Oxl.6

xO.5xl.OKI.5 29 3545

FA

FSFF

Coarse

agg

_Nl(c+A)

uc!(c+A)S

Minera]

Dosage

rate oi gate admixture.supefplsstieizing

Facters and

Leyets

admixture

Fig.13

Effect

of

Factofs

on

DTyLng

Shrinkage

-26-A7T625sg4gE-3i

2if'S

16

o

Age6M

,

'

x

"`hS

r

vV

* ,

S

17...,,pk

,GR--GC---.GL

･100'

Fig.14

O/Siliea

runn/

x,Fly ash ----L

12Q

14e

leO

ISe

200

22()

240

'water

content

(kg/mS)

Relationship

Between

Watei

Content

and

Drying

Shrinkage

Architectural Institute of Japan

ArchitecturalInstitute of Japan

Table

13

shows

the

analysis of variance on

drying

shrinkage of concrete

forvarious

factors

atage

6

months,

Fig.

13

shows

the

relationships

bet'ween

dr.ying

shrinkage and

the

factors

and

Ievels

which were

judged

to

be

significant at

the

1

%

level.

Fig.

14

shows

the

relationships

between

drying

shrinkage and unit water content

by

admixture-type.

(a)

Effect

of

Coarse

Aggregate

Type

The

effect

of

coarse

aggregat'e

type

on

drying

shrinkage

was significant at

the

1

%

}eveL

for

each

age,

Moreover,

type

of coarse aggregate

is

the

factor

which

has

most effect on

drying

shrinkage.

D[ying

shrinkage at age

₆

months

is

largest

for

crushed-stone concrete, at approx.

6

×

10n',

The

_value

fornatural-aggregate

_concrete

is

_about

30

%.

Iower

(approx.

4.5XiO"),

and

the

value

for

artificial-lightweight-aggregate concrete

(Type

I

)

is

about

sO

%

lower

(approx.

3

×

10").

'

This

is

conside[ed not

to

be

due

to

the

effect

of

the

unit water content, as shown

in

Fig.

14,

but

to

the

synergism

caused

by

the

existence

of calcium

silicate,

etc.

,

in

the

admixture,

In

addition,

the

reason why

th'e

drying

shrinkage of artificial-lightweight-aggregate concrete

(Type

I

)

is

sinaller

than

that

of

other

types

of

con6rete

is

due

to

the

large

water

absorption

rate of

_the

artificial

lightweight

aggregate

(23-2s

%),

leading

to

moisture

loss

during

concrete

hardening.

This

_phenemenon

was verifiecl

by

the

writer

in

a

_previous

study'3).

The

relationship

between

drying

shrinkage

qncl

type

of admixture, unit water content

for

artificial-tightweight-aggfegate concrete

(Type

I

)

in

this

test

is

considered

to

be

_peculiar,

and

it

needs

to

be

studied

further.

(

b

)

Effect

of

Admixture

Dosage

Rate,

Water-to-<Cement

₊

Condensed

Admixture)

Ratl'o,

Type

of

Admixture

and

Dosage

Rate

of

Superplasticizing

Admixture

a)

The

effects

of

the

above

four

factors

on

drying

sh[inkage were significant at

the

₁

_%

level.

'

b)

Drying

shrinkage

decreases

as

the

dosage

rate of admixture

increases,

while

it

increases

with water-to-(cement

'

'

+

condensed

admixture)

ratio.

c)

The

drying

shrinkages

of alum-type concreie and

fly-ash

concrete at age

6

months are

4-6

×

10-`,

which

is

almost

the

same, or slightly smaller,

than

the

value

6

×

10L'

given

in

the

crack-pievention

_guidelines

issued

by

the

Architectural

Institute

of

Japani`},

d)

The

unit water content of silica-fume concrete

is

largei

than

that

of

fly-ash

concrete or alum-type-mineral

concrete with

the

same slump.

However,

the

drying

shrinkage of silica-fume concrete at age

6

months

is

3.

4,

5

×

10'`,

which

is

20-25

%

lower

than

the

drying

shrinkage of

fly-ash

concrete or alum-type-mineral conctete.

Furthermore,

the

test

report

by

Messrs.

Seki,

Kadota

and

Yamane9)

states

that

the

drying

shrinkage

and

creepof

silica-fume concrete at･age

45

days

are,

respectively, about

so

%

smaller

than

those

of

concrete

with

ordinary

Portland

cement.

According

te

another

test

report

by

Me$srs,

Takagi,

Akashi

and

KadotaiZ),

the

drylng

shrinkage of

high-strength

mortar

decreases

if

it

is

mixed with silica

fume.

Messrs,

Tazawa

and

Yonekura

obtained similar results

for

high-strength

concretei5),

It

is

considered

that

this

occurs

because

the

cement

and

SiO,,

the

main

componentof

silica

fume,

become

chemically

bonded,

and calcium sMcate

hydrate

is

_produced,

creating capillary

_peres.

This

leads

to

smaller

_particles,

inhibiting

the

free

flow

of'water, which

in

turn

retards

the

drying

of

_gel

waterg).

Silica

fume,

on

the

othet

hand,

has

a wide range

of

_particle

diameters;

which

ensures

that

the

_pores

in

the

concrete are very small

because

the

_gaps

between

the

cement and

the

hydrate

are

fMed,

increasing

concrete

density').

'

e)

The

drying

shrinkage

greatly

increases

when

the

dosage

rate of.superplasticizer exceeds

the

standard rate

(

×

1.0>,

However,

the

drying

shrinkage

.of

concrete with.

Iess

than

the

standard

dosage

rate of superplasticizer

is

almost

the

sarne as

that

with

the

standard

dosage

rate.

5.

Properties

due

to

Ea6h

Factor

Table14

shows concrete

_properties

due

to

each

facto[

obtained

from

results of

dispersion

analysis.

6.

Conclusion

,

The

results of

the

tests

are summarized

beiow.

(1)

Properties

of

Compressive

Strength

,

a.

In

evaluating compressive

strength

and

tensile

strength,

the

factors

defined

as significant at

the

₁

_%

level

were

water-to-<cement

₊

condensed admixture) ratio,

type

of

coarse

aggregate,

type

of admixture,

hnd

d6sage

rate

of admixture,

'

'-Architectural Institute of Japan

NII-Electronic Library Service

ArchitecturalInstitute of Japan

Table14

Concrete

Properties

due

to

Each

FactoT

Typesanddosagerateofrntneral

admixture

Typesofcement

WICC+A)<z)

Typesofcearseagg-resate

Dosegerate

ofsuperplasti-cuingadm ±xture

Itern

PropertiesAgeAlum-type mineralSilicafumeFlyash

7daysDecreasewithdosage

rete<xl.O,

Highst.)

Decreasew

±thdosage rate<xO.4,

{Highst.)

Decreasewithdosage

rate(xe.4,

(Highst,)CH>CN>CF29>3S>45

GC>GR>GL

-e>.-de=mvoookqn ¢ ako"om

28daysDittoxO,4,xl.O

(High,st.)

Ditto

-

Ditto

DittoIncrease,Nith

dosagerate

xl,SHihst.

91daysDittoDecreasev

±thdesage rate(xO.4,

Highst.)

Unaffected

bydosage rate

-

Ditto

pitto

Ditto

7deysIncreesevithdosage

rate(xl,6,

Highst.)

Decreasevithdesage rate(xO.4,

(Highst.)

Decreasewithdosage

rate(xO.4,

Highst,)CH>CN>CF

Ditte

Dittoxl,S(Highst.)

=ptu-,eo-ecoedhupHca28daysxl,6(Highst.)

Dttte

Ditto

-

D

±tto

Ditto

-91daysxl.O(H

±ghst,) D±tto

Ditte

u

D

±tto

)ittoIncreasew

_desagerate ±th

(xl.5,Highst.)

7dalsUnaffected

bydosage

rate

Ditto

xO.4,xl.6

(Htgh)

CH>CN>CF

Ditto

CR)GC>CL

.

om-=v-op=dV-oraE

_28deysDitto

D

±tte

Unaffected

bydesage rate

-

pitto

Dttto

-91da]sDitto

Ditto

)ecreasewithdosage

rate(xO.4

High)

-

Ditto

mtto

7

=.HWhkopk=n･26weeks

_-

_'

_r

-45>35>29GC>GR>GLIncreasewith

dosagerate

(xl.Slarge)

Notes:

High

st,

=:

High

stTength

b,

The

compressive strength of $ilica

fume

concrete at age

7

days

is

almost

the

same as

that

of alum-type minerai

concrete.

However,

for

the

ages

28

days

ancl

91

days,

the

strength of silica

fume

concrete

is

slightly

larger

_than

fly

ash concrete and alum-type mineral concrete

by

3-10

%.

This

is

because

of

the

reaction and

hydTation

of

fine

silica

fume

_particles,

which

_pToduce

Ca(OH),

during

hydration.

This

increases

the

volume

of

calcium

silicate

hyclrate.

c.

The

compressive

strength

of

silica

fume

concrete

is

8

to

₁₀

_%

larger

than

_that

of

fly

ash

concrete

at ages

7

to

28days

with

a

dosage

rate

of

admixture

of

5-20

%.

d.

Considering

the

three

dosage

rates,

the

compressive

strength

of

concrete

is

the

greatest

for

silica

fume

and

fly

ash

at

a

dosage

rate

of

12.5

%

and

for

alum-type mineral at

a

dosage

rate of

2,5

%.

e,

The

improvement

of strength

is

more remarkable when silica

fume,

alum-type mineral and

fly

ash are added

_to

high-early-strength

Portland

cement

than

to

normal

Portland

cement.

f.

With

the

right combination of water-to-(cement

+

condensed admixture) ratio,

type

of admixture and

dosage

rate

ef

admixture,

the

following

compressive

strengths

can

be

obtained

for

water-to-(ce/ment

₊

condensed admixture) ratio

30

%

at age

28

days:

about

700

kgf/cmi

for

natural aggregate concrete, about

soo

kgf!cm'

for

crushed

stone

concrete

and

about

650

kgflcm2

for

artificial

lightweight

aggregate

concrete

(Type

I

).

g.

As

for

mineral-type

admixtures,

silica

fume

and

alum･type

minerals

are

effective

in

attaining

higher

st:ength,

(

2

₎

Properties

of

Tensile

Strength

a.

The

_general

relationship

between

compressive

strength

and

tensile

strength

for

various

factor/s

and

levels

(admixture

type,

water-to-(cement

+

condensed adrnixtuTe) ratio, cement

type

and coarse aggregate

type)

is

given

in

the

graph

shown

_previously,

and

it

can also

be

expressed

by

the

regression equation,

Eq.(3

).

If

this

equation

is

compared

to

a,=1.6VffE', which

is

_generally

used,

tensile

strength

is

underestirnated

for

compressive strength

below

550

kgflcm',

and overestimated

for

above

550

kgflcmi.

b.

The

ratio

tensile

strengthlcompressive strength

(

at/a,)

is

1114-1116

for

compressive strength

between

500

and