EXPERIMENTAL STUDY 0N PELLETIZED EXPANDEDSLAG AGGREGATE CONCRETE

by

Takashi IDEMITSUManuel Antonio CANAS LAZO Shun-ichi TAKAYAMA Koji ISHIBASHI (Received October 30, 1976)

SYNOPSIS In present days, sufficient disposition and effective utilization of industrial discharges

have become urgent problems to be solved in, JAPAN. The authors have been studying about Pelletized Expanded Slag (abbreviated as PES),

which is a lightweight coarse aggregate made from molten slag ejected from a blast furnaceby a special method. As a result of the investigations, the PES concrete has almost the same

properties as those observed in ordinary lightweight aggregate concrete except that thecompressive strength of the former was a little smaller than the latter and the former'sdurability was considerably excellent. Consequently, it can be said that the PES is sufficient

for practical use.

1. INTRODUCTION

Recently, gravel used as coarse aggregate of concrete has been exhausted in JAPAN.Crushed stone is used everywhere and considerable volume of artificial lightweight aggregate

has been used to reduce the dead weight of structures. On the other hand, the regulations on miming of raw materials for artificial aggregates are

becoming more and more severe from the standpoint of protection of nature. In the nearfuture, the want of aggregates will become a serious problem in JAPAN.

Hence, as one of the means to solve the problem, efficient use of slag, which is a bypro-

duct in pig iron production process, is being considered in many places. The authors havetried to utilise it as a lightweight coarse aggregate : PES.

The results and considerations of the experiments on PES, PES concrete and its usefor RC beams are descrived hereinafter.

2. MANUFACTURE OF PES

PES is a lightweight material obtained as a byproduct in the processing of pig iron. Fig.

1 shows a representation of this process.

The molten slag is poured over a revolving winged drum which scatters it into the air amid sprayed water and small pellets are formed due to cooling of the material. For further cooling, these pe11ets are deposited on a concrete platform. Thus, PES is cooled with speed,

- consequently, it becomes to have somewhat of latent hydraulic property as granulated slag. As the quality of PES is very sensitive to the conditions in manufacturing process i.e. molten

slag temperature, revolving speed of drum, shape of wing, cooling speed etc., sufficient care

must be taken for them.

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Molten slag

o,:k:i'ex;;:' 'sN,N. Gate Water WatertL ".... ;stT.;..E:.)R

`. h"ks" 'tu:". Current P Yed:, tt' ,ir- t,t "k".x. sra r SPraYerN N N t l .xs .

Reci ient Y--ks Re ulator NN" ,ItP Channel "-:. g " Chute SIN.

"rs, oe SssNt" @ OspWtaayteer

ro`tgzl3 NL:;M

@ @ pellets e @@ @ Winged Drum @ ww Concrete Platform

Fig.1-PES Production Process

3. EXPERIMENTS ON PHYSICAL PROPERTIES OF PES

3.1. Method of test The tests on lightweight aggregate, and the stanqards by which they were conducted, are

mentioned in Table 1. To compare with PES, an ordinary lightweight aggregate ; Nichilight,was also tested.

(a) External appearance test This test was conducted by simple visual and touching inspection.

(b) Floating particles percentage test

About 2e of aggregate were weighed and put into water during 10 minutes. The float-ing particles were taken up and dried for 24 hours at 100 -h- 1100C . Its weight was measured

and the following equation was applied.

Dry weight of fldating particles Floating particles percentage == Total weight of material Å~ 100 (%)

The other tests were conducted following the procedures explained in the standards

mentioned in Table 1.

Table 1 --Tests conducted oh the properties of PES

External AppearanceGrading (Sieve Analysis)

Specific Gravity

Absorption

Unit WeightFloating Particles Per-centage

JIS AII02

JIS AI135

JIS AI135

JIS AII04

JSCE CodePhoto 1 - PES

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3.2. Test results and consideration 3.2.1. Externalappearance The external appearance of PES (See Photo 1) is that of small, white or gray pellets with

harsh and porous surface like pumice. By touching inspection, small grains (Åë 10 mm under)felt approximately as hard as ordinary lightweight aggregate, but coarse grains (Åë 10- 15 mm)

seemed to be pretty brittle.

3.2.2. Grading A grading curve of PES is shown in Fig.2 with JSCE and ASTM limits. 1 he curve lies

outside of JSCE limits, but inside of ASTM's. It seems to be difficult to produce coarsegrains larger than 10 mm, because their shape become very flat ellipse. So, the gradingis a little fine compared with those of ordinary lightweight aggregate.

A ge v80 tn q gg Åí 60 w v g o q

-i-- "--7

/Jl ttlt

ifY

60 tl

,Lt,,4

40 •/Il',/r/"'

-PES----Nichilight2oo

'/'.---- ,c

t.x/t ---

ASTMLimit----JSCELimits

2.5 5 10 15 20 Sieve Size (mm)

Fig.2-Grading Curve of PES

3.2.3. Specific gravity Usually, the specific gravity of PES is slightly smaller than that of Nichilight as shown in

Table 2, although the former is larger than the latter, as in Table 9 which is rarely obtained,

because the quality of PES depends largely on the conditions of manufacturing process. Asthe specific gravity of artificial lightweight aggregate is changeable influenced by the value of

absorption, in this test, the aggregate in normal dry condition was soaked in water during 24

hours and after that dried until saturated dry surcace condition was reached.

Table 2-Physical Properties of PES and Nichilight

LightweightAggregate

DrySpecific

Gravity

SaturatedSpecific

Gravity

Absorption

(%)

UnitWeight(kg/m3)

SolidVolume

Percentage(%)

FloatingParticles

Percentage(o/o)

PES 1.20 1.43 18.9 715 60.0 7.6

Nichilight 1.29 1.55 8.6 855 66.5 1.8

3.2.4. Absorption As shown in Table 2, absorption of PES is 180/o which is comparatively larger than thatof ordinary lightweight aggregate. As a result of an experiment on velocity of absorption,

about 80/o out of that 180/o was gained within 1 minute since the moment when PES had been

deposited in water. After that, the velocity of absorption become very slow but itcontinued for more than 100 days. Once PES is part of concrete, the value of 18 O/o will be reduced with passing of time,

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because PES has somewhat of latent hydraulic property and displays it in concrete, conse-quently, small pores in PES grains are partially filled with new gel of hydration.

3.2.5. Unitweight The test result of PES unit weight shown in Table 2 is slightly smaller than that ofNichilight. With these values, solid volume percentages are obtained as a!s'o shown in the

same Table. It is said that the larger the value is, the better grading and shape of aggregate

are obtained. Since the grading of PES'is not good as mentioned before, the solid volume

percentage of PES is about 6 O/o smaller than that of Nichilight.

3.2.6 Floating particles percentage Floating particles percentage of PES is about 80/o as shown in Table 2, which satisfies the

allowable value by JSCE (less than 100/.).

Physical properties of PES have been described as above. From these results, it can be

said that the quality of PES is not necessarily so good as ordinary lightweight aggregate but

it almost has the properties required to lightweight aggregates. Moreover, there is enough

room for improvement of its quality by means of varying the conditions in the process ofmanufacture. As blast furnace slag scarcely contains bad chemical compositions such asheavy metals, and sulphides melt into cooling water, it is considered that PES does notpossess any harmful compositions.

4. EXPERIMENTS ON PROPERTIES OF PES CONCRETE

4.1. Materials used in this experiment (a) Cement Normal portland cement having specific gravity of 3.15 was used.

(b) Water Ordinary clean water was used.

(c) Fineaggregate The properties of the fine aggregate are shown in Table 3,

(d) Coarseaggregate The properties of PES and Nichilight used as coarse aggregate were already shown inTable 2.

(e) Water reducing and air entraining agent Pozzolis 5L and 5LA were used as water reducing and air entraining agent, respectively.

Their quantities were determined according to the instruction of the maker.

Table 3 -- Physical Properties of Fihe Aggregate

Specific

Gravity

Absorp-tion

(%)

UnitWeight(kg/m3)

SolidVolume

Percent-age

Fineness

Modulus

2.57 1.4 1596 ' 2.42

4.2. Mixproportions All kinds of mix proportions are described in Table 4. Mix proportions from P-1 to P-8

were used to obtain a o2s-- C/VV curve of PES concrete ; from P-9 to P-11, to investigate the

influence of air content on compressive strength ; and from P-12 to P-22, to investigate bond

strength and permeability. Those from N-1 to N-4 were of Nichilight concrete.

4.3. Methods of test The tests conducted on the physical and mechanical properties of PES concrete are

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mentioned in Table 5. The methods of bond strength, durability and permeability testsare described hereinafter.

Table 4 -PES Concrete and Nichilight Concrete Mix Proportibns

UnitContentsofMaterials(kg)Mix

Proportionw/c(9o)

S/a

(Aoo)W c s IG

AirEntrainingand/orWaterReducingAgent

P-1 35 38.0 150.5 430 637 583 Pozzolis5LP-2 40 39.o 152 380 668 586 11

P-3 45 40.0 153.5 341 696 586 II

P-4 50 41.0 155 310 734 592 n

P--5 55 42.0 156.5 285 748 579 fl

P-6 60 43.0 158 263 771 573 11

P-7 65 44.0 159.5 245 794 566 n

P-8 70 45.0 161 230 817 559 ll

P-9 50 41.0 155 310 723 583 Pozzolis5LAP-10 50 41.0 155 310 713 575 II

P-11 50 41.0 155 310 702 566 tt

P-12 50 39.0 180 360 564 696 Pozzolis5LP-13 55 40.2 185 336 669 633 IJ

P-14 60 43.0 185 308 725 612 !l

P-15 60 40.0 205 342 644 615 tl

P-16 65 44.9 205 315 732 572 lt

P-17 70 41.4 195 279 698 629 It

P-18 55 41.6 215 391 679 607 -P-19 60 42.6 220 367 699 599 -P-20 60 42.6 230 383 682 585 -P-21 65 43.6 230 354 709 583 -P-22 70 44.6 224 320 744 588 -N-1 47 39.8 157 334 704 642 Pozzolis5LAN-2 50 40.4 158 316 722 639 tt

N-3 53 41.0 159 300 736 636 ll

N-4 56 41.6 160 286 751 632 IJ

Table 5 -Tests Conducted on Properties of PES Concrete

TEST STANDARD SPECIMENSWorkability J!SAIIOIAirContent JISAII18UnitWeight JISAII16 Cylinders4510X20cmCompressiveStrength JISAII08 IlltTensileStrength JISAII13 11flFlexuralStrength JISAII06 Prisms15X15Å~50cmYoung'sModulusand

Poisson'sRatio ASTMC469 Cylinderse510Å~20cmDurability ASTMC290 Prisms7.5Å~10Å~42cmBondStrengthPermeability

ASTMC234 Cubes15Å~15Å~l5cm(S.tfile".bda,rdS)Cylihdersa515Å~30cm

(a) Bond strength test Round bars Åë 19 and deformed bars D19 were embeded in 15 Å~ 15 Å~ 15 cm concretecubic specimens. At the moment of placing concrete into the molds, half of the bars were

embeded holizontally and the other half vertically. This was aimed to find the relation

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between bond strength and embedding orientation of the reinforcement. The pull-out method

recomended by ASTM was used and Fig. 3 shows the way of loading as well as the arrange-ment of a specimen and a dial gauge for measuring free end slip.

(b) Durabilitytest Following ASTM Standard, rapid freezing and thawing tests in water were carried out as

durability test for two mix proportions P-4 and P-10. An outline of the testing machine is

shown in Fig. 4. After the determined number of freezing and thawing had been repeated,

dynamic modulus of elasticity was measured. The test result is expressed by the relative dynamic modulus of elasticity and thedurability factor which are calcUlated by Eq.(1) and Eq. (2), respectively.

p. = tEixioo (%) (i) where Pc = Relative dynamic modulus of elasticity after C cycle of freezing and•

thawing (O/.) E = Dynamic modulus of elasticity before freezing and thawing test (kg/

Cm2) Ei = Dynamic modulus of elasticity after C cycle of freezing and thawing

(kg /cm2)

DF=PhaNxioo (so)6o) (2) D.F=: Durability factor (O/o) P= Relative dynamic modulus of elasticity after IV cycle of freezing and

thawing N= The number of cycle at which the value of P becomes the estiablished

one (600%) or the test is over (300 cycles) M= The number of cycle at which the test is over (300 cycles)

Dial Guage(1/1OOOmm)

Free End

TestSpecimen i)

Reinforcing bar

ThawingBrine

Ethylene Glycoly

Thermometer

1Lo'

FreezingBrine

TestSpecimens

Fig.3-Bond Strength TeSt Fig.4-outline of Durability Testing Machine Arrangement

(c) Permeabilitytest For this experiment, cylindrical specimens (Åë15 Å~ 30 cm) having a central longitudinal

hole which acts as a drain for water were made and cured during 3 weeks, then dried atambient temperature during 1 week. The cross section of testing aparatus and a specimen are

shown in Fig. 5(i). The test was carried out at the age of 28 days using the input method. By

means of a compressor, water pressure of 20 kg/cm2 was applied during 48 hours (24 hours

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when WIC ratio was high). After the test, the length-s of water infiltration were measured

along longitudinal direction at intervals of 1 cm and the average was adopted as infiltration

length. The diffusion coefficient was calculated by applying Eq.(3).

i2=ZZT2 (3) where : i2== Diffusion coefficient (cm2/sec) Dm == Average length of infiltration (cm)

t = Duration of time of water pressure application (sec) a= Coefficient related to 'Nt" (a= t3,7)

6= Coefficient related to the amount of water pressure. A numerical relation between S and Po (water pressure) appears in Table 6.

x

Rubberckmg

WaterPressure Table 6-- Numerical Relation Between Co- (20kg/cnf) eMcient 6and Amount of Water Pressure Po (Atmospheric pres- sure assumed as 1 kg/cm2)RubberPackmg (kgPt :.)

g of InJected Water Drainage for test speclmen

Fig.5-Cross Section of Permeability Test Apparatus and specimen

Po(kg/cmi) 2.5 5 10 15 20

6 O.594 O.904 1.163 1.301 1.386

The rest of the tests were carried out according to the standards mentioned in Table 5and, with the logical exception of workability and air content tests, the specimens were cured

during 28 days in water at 20 Å} 10C. (Compression test specimens were also tested at 3, 7 and

120 days and curing, of course, was maintained until testing ages.) Three specimens were

tested at each time.

4.4. Test results and consideration The results of the first seven tests shown in Table 5 are summarized in table 7. Theirdetails, the rest of results and the considerations about them are described hereinafter.

4.4.1. Workability From the results of mix proportions in which MZ/C and va are constant (500/o and 155kg/m3, respectively), i.e. P-4, P-9 and P-10, the relation between slump and air content isplotted in Fig. 6. (However, mix proportion P-11 is omitted because its air content is too high

for ordinary AE-concrete.) From that figure, it can be said that the slump decreases about 2.5

cm when the air content decreases 10/o. This relation is almost equal to that of ordinary

lightweight concrete.

The decrease of slump and air content with the passing of time were measured for mixproportion P-4 and their results are shown in Figs.7,8, respectively. From Fig.7, it is seen

that the decrease of slump during the first 30 minutes is about 3.5 cm. But 2.5 cm out of this

value is due to the decrease of about 1O/o of air content which occurs during the same

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Table 7 -• Physical and Mechanical Properties of PES Concrete andNichilight Concrete

Mix

Preportion

w!c

(%)

Slump

(cm)

AirContent(%)

CompressiveStrength

dy(kg!cmZ)

Tehsile

Strength

ot

(kg!cm2)

FlexuralStrength

ab

(ig!Cm2)

Young'sModulus

E2s(Å~1cr`kg!cm2)

Poisson's

Ratio

"

UnitWeight(t!m3)

P-1 35 14.0 3.3 275 20.2 O.17 1.87

P-28.9 3.7 250 19.5 O,19 1.87

405.3 4.3 274 19.5 O.10 1.88

P-3 452.8 2.4 260 19.8 O.13 1.88

4.5 6.0 245 18.4 O.19 1.87

2.9 5.5 265 19.0 O.27 1.85P-4 50

3.5 5.1 236 18.0 1.87

P-5 55 6.2 5.4 198 16.9 O.21 1.85

P-6 60 7.3 5.0 171 15.6 O.22 1.84

P-7 65 5.3 5.2 152 15.9 O,20 1.85

P-8 70 3.0 6.0 145 15.6 O.19 1.86

P-9 50 5.5 6.2 223 18.3 1.86

P-10 50 7.3 6.8 206 16.4 1.82

P-11 50 9.1 9.1 194 18.0 1.80

P-12 50 8.2 6.1 248 17.3 17.2 O.19

P-13 55 14.2 6.6 247 17.1 17.7 O.18

P-14 60 11.4 7.9 186 16.3 18.3 O.26

P-15 60 20.7 4.3 195 16.7 16.5 O.19

P-16 65 19.1 6.8 189 16.3 15.5 O.24

P-17 70 18.3 4.6 177 14.6 14.7 O.16

P-18 55 12.3 Ll 267 23.5 22.5 O.19

P-19 60 15.0 1.3 246 22.2 17.6 O.14

P-20 60 17.7 2.2 241 15.9 18.6 O.17

P-21 65 16.0 2.1 241 19.3 17.9 O.22

P-22 70 19.0 3.1 197 18.1 15.9 O.19

N-1 47 5.0 6.3 301 29.7 15.5 O.17 1.90

N-2 50 6.5 5.2 390 27.4 14.4 1.89

N-3 53 7.2 6.2 255 21.8 24.9 16.2 O.15 1.91

N-4 56 6.0 4.7 250 27.0 15.8 O.14 1.89

8

A7ee6n8sE04 3

05 67 Air Content(%o)

Fig.6-Relation Between Slump and Air Content

interval, as shown in Fig.8. It is considered that the remaining 1.0cm is caused by water

absorption of PES and hydration of cement etc.. Comparing PES concrete to Nichilight concrete, PES needs a little more unit cementcontent to produce a concrete with the same characteristics of workability, strength and

air content. But, the roughness of PES surface had a good adherence with the mortal, the

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floatation of PES scarecely occured even when a table vibrator was used to compact the

concrete, so the finishability was also good.

.-.7gv6gs

s

di4o

3

2

1

Just 10 2030 405060After Time(minu

Mixing

AoBR

;.q7ti

8e

i

10 20 30 40 50 60 J 30 60 90After Time (mmutes) After Time (minutes)

7 MixProportionP-4

Slump7.2cmt.

6

5

Fig.7- pD.e ,c ,r iei,se.fofTliu.mpwiththe Fig•8-.Dftchre,ahS.epo.f,,Ai:r.C.:nTtfii:

4.4.2. Unit weight This test was carried out in natural dry condition. Values obtained for PES concrete are

about 1.85--1.90t/m3 which are almost the same with those of ordinary lightweight aggre-

gate concrete.

4.4.3. Compressivestrength In Fig. 9, the o2s•- C/MZ curve of PES concrete is shown together with those of Nichi-

light and pumice concrete. The upper limit of the compressive strength of PES concrete at

28 days is about 250 kg/cm2, and the strength does not increase when the C/MZ ratiobecomes larger than 2.0. Therefore, this concrete is allowed to be used when the design

strength is about 100---200 kg/cm2.

kg/cm2) (kg/cmZ)ge

b 300Åípoo:ots

ca 200oiZtB

9Qe loooo

C/W l.5 2.0 2.5 3.0VV/Wt065605550 45 40 35(O/o) 037=t 50Age(days300 150 Fig.9-o2,-c/vvCurve Fig'10'I"Cs"te,a.S.eg2fhC.OilPhPrAeES.iVe

/ 8. 3oo s,

8 2oo a E 8..' e--" Nichilight Concrete oK) PES Concrete l -.-- pumice Concrete l ioo eP-3MixProportion

oP-10,,

The increase of compressive strength with the age is shown in Fig. 10. Even after 28days, the strength of PES concrete is increasing and reaches about 300 kg/cm2 at the age of

120 days, which may be explained by the fact that the strength of PES itself increased as aresult of the performance of its latent hydraulic property after a long time had passed. If PES

would not have the potential, the strength of the concrete would be limited to about 250 kg/

cm2, as mentioned before. The relation between compressive strength and air content is shown in Fig. 11 with the

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results obtained from mix proportions P-4, P-9, P-10 and P-11. It is found that the com-pressive strength decreases about 50/o due to an increase of 10/o in the air content when the a2s

is equal to about 200 kg/cm2. This relation is almost same with that of normal aggregateconcrete. The value of compressive strength used in Fig.9 had been corrected with this value.

S. (kg/cmi)

Edi 240ge

'gg 220

gg 2oo

o180

oo

PES-AEConcrete

o

og,

o

9(906o

WlC= so o/oVV= 155 kg/m3sla = 41 %

Air Content

Fig. 11 -Relation Between Air Content and Compressive Strength

4.4.4. Tensile and flbxural strength From the results shown in Table 6, the ratios oftensilestrength to compressive strength

and flexural strength to compressive strength are obtained as 1/14 -- 1/9 and 1/8 ---1/5,

respectively, which are reasonable values for a lightweight concrete.

4.4.5. Modulus of elasticity and Poisson's ratio The modulus of elasticity was 15.0Å~ 10` kg/cm2 at the age of 28 days which increases

with the increase of compressive, strength, as in ordinary concrete. Fig. 12 shows a little

higher modulus of elasticity for PES concrete as compared with Nichilight concrete. It isbecause the latent hydraulic property over the surface of PES aggregate was activated by the

alkali attack of cement producing a good adherence between the surface of the aggregate and

the mortar.

The Poisson's ratios lie between O.17and O.22, and did not show any relation withcompressive strength, which seem to be reasonable ones for a lightweight aggregate concrete.

( Å~10` kg/cm2)

gS 20gEhzz

EÅrO, 15

1

pt oooo20

15

oo

oooco,8.}B oeoee

:ebe

o eeS eee

st`

oeOPESConcreNichilight

Concrete

O150200250300350 - Compressive Strength (kg/cmi)

Fig. 12-Relation Between Compressive Strength and Young's Modulus

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4.4.6. Durability The results of this test are plotted in Fig.13 with other results(') reported before and

showed an excellent durability of PES concrete giving a durability factor of 83.1 O/o for P--10

mix proportion. A little loss of mortar at the specimen surface and a little exposure of the

aggregate after 300 cycles of freezing and thawing were observed. It can be said that the

durability of P-10 mix proportion PES concrete is almost as good as that of ordinary AE-concrete.

This excellent durability of PES concrete can be taken as foljows: From microscopicview, in PES aggregate a very smaller voids than those pre$ent in Nichilight aggregate were

found to have not been filled completely by water during the test, Hence, unlike in Nichili-

ght aggregate, the swelling force by freezing seems to be consumed by those smali pores.

leo

Atsi"

v . 9e"t

.9't7S

-es semÅé

S 70sgE 6oo•b-

-es

o50pd

'N- -N.. ." Normal AggregateNf::!.--}-.---..rl.=fiiii!l..h....-. PESmAE[2itiriiiiiilnclret:-e6.sg.6.)l- l '-"-""N. AE CeRcrete

N I

s

Å~s

----"

Normal Aggregate N Concrete

Å~

Nichiiight "" "" -• ..AE CoRcrete ""ts (Tested in air)

PESAE ConcreteÅqair:5.1%o)

o 100 200 cyc!es 300 Fig. 13-Quality Deterieratien of Varieus Cencrete by Repetition of Freezing and Thawing

4.4.7. BendstreRgth The resglts of boRd test 3re giveR iR Fig. 14. The boRd strength correspoRding to the free

eRd slip ef O.el mm are 45--50 kg/cm? about 20 kg/cm2, 25-30 kg/cm2, and about 15 kg/cm2 fcr defcrrr}ed bar embeded vertical!y, horizeRtal!y and for round bar embeded vertically,

hoyizoRta!ly, respectively, which seem to be confimoR values for erdinary lightweight aggre-

gate ccRcrete. The reaseR why the bond stress of horizentally embeded bars is almost 1/2of that of vertically embeded ones in beth round and deformed bars can be explained by the

pheRorcenoR of bleediRg: free water due to bleeding stays beneath horizontal bar and that

makes weak pcints such as laitance layers and voids.

4.4.8. Permeability The results of this test 'are shown in Figs. 15, l6.

Fig. 15 shows the relation between W/C ratio and diffusion modulus. From that figure,it vvould be concluded: There is not evident difference between air entrained and non-entrained PES concrete and the diffusion modulus becomes extremely large when va/C ratiois more than 650/e.

Curve$ for Mesalight (an ordinary lightweight aggregate) and normal aggregate concreteare also shown in the same figure. It is seen that there is not significant difference between

Mesalight concrete and PES concrete. However, between the normal aggregate concreteand those lightweight aggregate concrete a little differences are observed. But, this is con-

sidered mostly because of the difference of their maximum sizes, i.e. maxmum size of Mesa-light and PES are 15 mm, but that of normal aggregate is 25 mm. It is autholized that the

-u-

larger the maximum size of aggregate is, the higher the permeability of concrete becomes.

Fig. 16 shows the relation between diffusion modulus and unit cement ratio. From thisfigure it can be said that, if compressive strength, slump and diffusion modulus are constant,

air entrained concrete requires 5-•-100/o less cement content than non air entrained concrete.

Finally, let us see Fig. 17, which explains the influence of bleeding in the diffusion

modulus. Bleeding is the phenomenon of the rising of surplus water in the mortar, consequ-ently, pores are abundant in the top of the specimen, so water infiltration becomes easier than

in the middle and bottom parts of the specimen.

70

Ag 6oxt)`'

i. 50sdi 40

Efi 30

Ot,o

N 20gl

Åq 10

o

Deformed bar---- Round bar

•1Åë•

Vertlcally Ernbeded WlC= ss% V. Wl C= 6o e/e

/t:Jr..--

10 20 30 - Free End Slip (Å~•lo-3mm)

Fig. 14-Relation Between Bond Stress and Free End Slip

A8 6o-E{2

gvv. 509

e(YtL'"

s-5

gE 30.8

:t 20

g

80O'K)AEConcreteHNonAEConcrete70

7

60

50

40

30

20

Mesalight!Concrete'N{ts`

10

ptgsseg

-

osccysNQo"QgLe/

3teZZ

.-"-

.-.-.

O 50 55 60 65 70 75A Water-CementRatio W/C(%)v 60$']g

e so6-Å~ 40

"n-Nc!1

. 30-5=vo 20:l

q-8- io$

Åë

b- O

x-o o-oAEConcrNHNonAECe

eooX

Ol ex.-c .

Fig.15-Relationship Between W/C Ratio and Diffusion Modulus.

3oo 3so 4oo gls Unit Cement Content fi o (kg/m3 of Concrete) ..O. o o 24Fig. 16-Relation Between Diffusion Modulus 8 O and Unit Cement Content ped .9 O a 3o

Diffusion Modulus Bi• Å~10`(cm2/sec)

A06 7 8 9 10y"- 6

O ur/ C= 55 toOS& i2 O. ill,U,M=P,=,i%, 2cm

Fig.17-Relation Between Diffusion Modulus and Depth from the Upper Surface of the Specimen

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5. FUNDAMENTAL STUDY ON AN APPLICATION OF PES CONCRETE TO RC BEAMS

The physicaliand mechnical properties of plane PES concrete have been made, clear as

mentioned before. But when PES concrete is used in RC beams, we can not say how itbehave because reinforced concrete is a composite material in which the components interact

with each other in a complicated way. The authors carried out flexural test to investigate the PES concrete behavior in RC

beams. 5.1. Test specimens details Rectangular RC beams shown in Fig.18 were manufactured as test specimens. Thecross section (10 Å~ 20 cm) and the span (150 cm) were constant in all beams. The arrange-

ment of reinforcing bars is shown in the same figure. For PES concrete two values of VV/C ratio were adopted:550/o and 680/o. With theseratios, 200kg/cm2, 150kg/cm2, respectively, were expected as compressive strength of

concrete at 28 days. Two beams were manufactured for each of the combination shown in Table 8.

500g 2ip6

Strain)e'`"" gaugeX"' ,

DialGauge(11100mm) 4ooioo

t,,,L(,1--',D'Dlia,,, Dial(111ooomm

(Unit:--- 15001600

100

50

to ots o,- N

/

Fig. 18-Beam Specimen and Set-up of fiexural Test

Table 8-Combinations of Beam's Materials

Concrete Reinforcing

Aggregate w/c(%) Bar

PES 55 2-D1OPES 55 2-D13PES 55 2-D16PES 68 2-D1OPES 68 2-D13

Nichilight 60 2-D13

5.2. Usedmaterials (a) Coarse aggregate Table 9 shows the properties of PES and Nichilight used in this experiment.

(b) Reinforcing steel bars Dimensions and mechanical properties of reinforcing bars are described in Table 12.They were ground in their central part to stick on each of them four strain guages. These

guages were placed on the same circumference longitudinally and separated equal intervalsfrom each other.

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Other materials such as fine aggregate, cement, water and air entraining agent were the

same ones as had been used in the tests mentioned before.

Table 9--Physical Properties of PES and Nichilight

Coarse

Aggregate

DrySpecific

Gravity

SaturatedSpecific

Gravity

Absorption

(%)

UnitWeight(kg1m3)

SolidVolume

Percentage(%)

Fineness

Modulus

FloatingParticles

Percentage(o/o)

PES 1.67 1.77 5.6 1036 61.9 6.03 1.0

Nichilight 1.25 1.55 10.5 841 67.3 6.54 O.3

5.3. Concrete mix proportions and its mechanical properties Corrcrete mix proportions and its mechanical properties are shown in Tables 10, 11,respectively.

The compressive strenghth of PES concrete for both water cement ratios became analmost constant value of 200---220 kg/cm2. This may be attributed to the following facts: The experiment was carried out during the summer season, thus the concrete tempera-

ture was higher compared with that obtained during winter, so the actual strength became

higher than expected ; but because the maxmum strength of PES concrete was limited to200--220 kg/cm2, the strength of MZ/C == 550/o PES concrete did not reach a higher value but

became almost equal to that of VV/C=680/o PES concrete. Consequently, experiments ontwo types of RC beams made from two kinds of concretes having different strength could not

be carried out.

Table 10-Concrete Mix Proportions

MaterialsWeightfor1m3ofConcrete(kg)Lightweight

CoarseAggregate

w/c,

(%)

Slump

(cm)s/a

W PozzolisAggregate

AirContent

(%)cFine Coarse

PES55 11 O.40 189.5 3.5 350.9 663.6 685.7 5

68 11 O.41 193.1 2.9 288.2 698.0 691.9 5

Nichilight 60 11 O.43 173.1 2.9 293.3 752.5 601.6 5.

Table 11-Physical and Mechanical Properties of PES Concrete and Nichdight Concrete

CompressiveStrength(kglcm2)

Young'sModulus(Å~10`kgfcm2)

Coarse

Aggregate

w!c

(%)

Reinforeing

Bars

Slump

(cm)

Air

Content

(%)

7days 2eaays

TensileStrength

at

2eaays(kglcm2)

Flexu-ral

Streng-that2Ways(tg1Cm2)

7days

Poisson's

Ratio

at

2eaays

Unit

Weight

qtlm3)curedinair

curedinwater

curedinair

curedinwater

curedinair

curedinwater

curedinalr

curedinwater

curedinair

curedinwater

curedinair

curedinwater

t.

2-D10 11.4 4.4 202 - 329 - 19.6 - 30,9 21.4 - 19.0 r O.21 m 1.96

55 2-D13 16.7 4.5 172 174 225 217 19,2 16.7 33.2 16.6 17.2 15.5 18.4 O.18 O.24 1.90

PES 2-D16 17.7 4.9 175 175 228 207 19.6 14.6 27.8 18,3 18.0 16.3 19,6 O.18 O,28 1.89

682-D10 17.6 6.2 160 150 212 197 19.8 16.4 25.7 17.5 17.9 16.3 19.0 O,21 O.23 1.92

2-D13 9.4 5.0 167 161 219 210 12.9 12.5 27.4 17.5 16.7 16.3 18.3 O.19 O,25 1,91

Nichilight 60 2-D13 7.8 3.4 201 176 264 238 23,9 21.7 26,8 13.3 14.2 13.4 14,O O,20 O.21 1,75

5.4. Set-up and procedure for flexural test Set-up of the test is shown in Fig. 18. Load was applied to the beam step by step, andthen measurements of beam's deflections as well as strains of concrete and bars were done at

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each load step. Once cracks were found, the propagation of them were observed checkingtheir number and each length until the failure occurred.

5.5. Resultsandconsiderations 5.5.1. Type of failure and failure load As shown in Table 12, the steel yielding moments of the beams obtained from results of

steel's strain measurements are about 75-900/o of their ultimate moments. The theoreticalultimate moments calculated by Whitney's theory and kagami's theory(2) are about 80•-- 900/o

of the ultimate moments and rather near to the yiqlding moments. As compared with Nichilight beams, the failure loads of PES beams reinforced equally(2-D13) is a little smaller than the former's one, but this was caused by the difference of

compressive strength of concrete. When the strength of both concretes are the same, itcan be considered that failure loads will become almost equal in both cases.

Table 12-Theoretical and Experimental Ultimate Moments (Unit t•m)

ExperimentalValuesTheoreticalvalues(UMIotmil2ft::)

Coarse

Aggregate

ReinforcementWlC

(%)

acuat28days

(kglcm2)

Steel

Ratio

p

Beam

No.

SteelYieldingMoments

Ultimate

MomentsElastic Whitney Kagami

1 O.625 O.883O.741 O.74455 329

2 O.575 O.850O.O0815 O.6762DIO

As=:1.4266cm2 1 O.600 O.790O.722 O.72668 212

2 O.625 O.825

1 1.250 1.6001.217 1.229PES Jr5 225

2 1.150 1.5201.1602D13

As=2.534cm2O.O1448

1 1.175 1.5701.212 1.22568 219

2 1.200 1.525

1 1.750 2.0551.764 1.768 1.7972D16

As=3.972cm255 228 O.02270

2 1.850 2.050

1 1.200 1.6051.241 1.251Nichilight

2D13As=2.534cm2

60 264 O.O14482 1.200 1.658

1.160

Steel Yielding Point asy=3,110kg/cm2

5.5.2. Neutral axis location A typical experimental strain distribution diagrams are shown in Fig. 19. Usually, it's

considered that the actual load is 1/3 of the ultimate load.

o 2oo 6oo looo exlo-6 bo"""' .b' "h-" ty.lp t'L'Dxys

PES, VVIC== 55%

ExlO'6 1000 600 200 Fig. 19-Typical Strain Distribution and Neutral Surface Location in a RC Beam Under Flexural Test

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In this case, the experimental value of Xn (the length between the upper surface and the

neutral surface of the beam) at about 1.2t which is 1/3 of the ultimate load 3.53 t is slightly

smaller than the theoretical one calculated by elastic theory and the effective concrete area is

also smaller. This difference arises in normal aggregate and ordinary lightweight aggregate

RC beams, too, and may be explained by the fact that the value of Young's modulus obtained

in the compression tests employed in this calculation is comparatively smaller than that inflexural tests.

5.5.3. Vertical deflection A comparative diagram of the deflection curves which were obtained from the flexuraltests of PES and Nichilight concrete beams reinforced equally (2-D13) are shown in Fig. 20.

As the difference of Young's modulus between both concretes was small as shown inTable 11 (PES : MZ/C ==550/o • 2-D13, Nichilight : PV/C=600/o • 2-D13), those curves agree well

with each other at each Ioad step, and the difference between measured values and calcu-lated ones is very small.

2 t 2

,

o

G' ioo"

25g 2oo

'8

oÅëoa

300

P= lt

n

7t- '

-...

2t'

N tsN 3t

N t

N t

N

N 1N t

x 1NN..

--e-----

4t CalculatedCurve

2D13Bars 5t

eW'iCh,jl'g,h,t

PESoW!C=55

(a) Nichilight, VV/ C= 60 %o Cracking Load 1 .0 t Ultimate Load 6.63 t

Calculated i (b) PES, VV/ C= 55% gillisg,giggot% 8Ie,c.ks?g,Ls.a,d,i.•2,t

400 Fig. 21-Cracking Situation of Typical Failed Beam (Reinforcement 2--D13)Fig. 20-Comparison Between Two Typical Beam Deflection Curves

5.5.4. Crackspropagation In reinforced concrete, cracks are allowed to occur in the tension side of concrete but their

width should be smaller than O.2mm not to rust reinforcing bars. It is also said that it isbetter to have many small cracks than to have few large ones. Fig.21(a) shows the cracks

distribution in Nichilight concrete failed beam and Fig. 21(b) shows the same in PES concrete

beam. From those figure, it is seen that the number and propagation of cracks are almostsimilar in both cases.

5.5.5. Stress in reinforcement A typical result is shown in Fig. 22. As seen in that figure, the difference between the

experimental and theoretical values is small. Thus, again it can be said that PES RC beams

behave in a similar manner to normal concrete beams.

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6.0

ae 4.ovvNoA

2.0

o

----o--oExperimentI

TheoreticalLine

HExperimentllt

'

'

Nichilight: 2D13W/C=60%Ultimate Load:6.42t

'Ec=13.4Å~10`kg/cmi

500 1000 1500200 Strain of Reinforcement ( Å~ 10'6År

Fig.22-Relation Between Load an' d Strain of Reinforcement

6. CONCLUSIONS

The results of the investigations on PES aggreate, PES concrete and its use for RCbeams can be summarized as follows : 1 ) The PES looks a little weaker due to the presence of pores internally and externallyas pumice, but it is itself enough hard for a artificial lightweight aggregate and becomes

harder in concrete with time because of its latent hydrqulic property.

As mentioned before, PES has some gQod points and defects as a lightweight aggregate,

and generally, its quality seems- to be slightly inferior to ordinary lightweight aggregates.However, it has been made clear that PES almost has the properties required to a light-

weight , aggregate.

2) The PES needs a little more unit cement content to produce a concrete of sameworkability and strength, when compared with ordinary lightweight aggregate, due to itssmall solid volume percentage and roughness of surface ; but, as PES is a byproduct of pig

iron processing, an acceptable economy in concrete can be obtained. The roughness of thesurface produces a good adherence with mortar and floating of the PES aggregate scarcelyoccur even when subject to the table vibrator, thus, PES concrete has a good finishability.

3 )The compressive strength of PES concrete at the age of 28 days is about 250 kg/cm2,

which is a little small for a lightweight aggregate concrete. But, at the age of 120 days the

strength becomes up to 310kg/cm2. This is because of increase in the strength of theaggregate itself due to its hydraulic property. The value of test results on the following

properties of PES concrete is almost the same with those for ordinary lightweight concrete,

i.e.unit weight, tensile and flexural strength, bond strength, permeability etc.. But theYoung's modulus is comparatively large and, above all, the durability is excellent for a light-

weight aggregate concrete. 4 ) When PES concrete applies to RC beam, cracking and deflection behaviors of thebeam are closely resemble to those of Nichilight concrete beams and its failure load is almost

equal to that of the ordinary concrete beam having the same compressive strength of concrete

and the ratio of reinforcement.

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After conducting the investigation on PES aggregate concrete, it is concluded that itsproperties and behaviors in RC members are almost similar to those of ordinary lightweight

aggregate concrete. From now on, if the quality control in the manufacturing process isadequately conducted and massproduction comes to be possible, PES can be used as a light-

weight aggregate and solve a part of the aggregate shortage problem.

ACKNOWLEDGEMENTS The authors want to express their gratitude to proffesor Dr. Akira WATANABE becausewithout his help and guidance this work would be impossible.

Acknowledgements must be also given to Shigeyuki SOGOH, Makoto KOHYAMA,Kohji O,NODA, Yuhzo OHTA and Masahiko SHIROHZU ; graduates of Kyushu Institute ofTechnology, who had grappled this theme as their theses.

Finally the authors want also to thank TAIHEI KOGYO Co., LTD. and NIPPON STEELCHEMICAL Co., LTD for their help to conduct the experiments.

REFERENCES

Kl) M. Kokubu, Doboku Zairyo Jikken, 2nd. Ed.,Gihodo, 1974.

(2) T. Mizuno, TekkinKonkurit'o Kogaku, 2nd. Ed., Morikita, 1970.

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