ACI MATERIALS JOURNAL TECHNICAL PAPER

Design and Elaboration of Concrete Mixtures UsingSteelmaking Slags

The use of electric arc furnace oxidizing slag (EAFS) is discussed inthis paper as a high-quality coarse aggregate for the manufactureof concrete. Ladle furnace reducing slag (LFS) is also discussed,both as a fine aggregate and a potentially hydraulic material. Asingle system is used for proportioning this type of concrete, inwhich the presence of very fine inert materials is a determinant.The properties of this type offresh concrete are evaluated, which insome cases exhibit rapid setting. In a hardened state, their physico-mechanical properties are those of high-quality concretes, showingoutstanding compressive strength. It is concluded that high propor-tions of EAFS and moderate proportions of LFS rnay be used in themanufacture of precast concretes, and that, in this case, the latterdemonstrates considerable hydraulic activity.

Keywords: electric arc furnace slag; ladle furnace slag; rapid setting;recycling; strength; workability.

INTRODUCTIONThe cement, mortar, and concrete industry is a sector

of activity that currently contributes notably to the globalemission of greenhouse gases, mainly in the form ofcarbon dioxide (C02), I In the case of portland cement,this gas is emitted due to the decomposition of its rawmaterials, calcination processes, and the combustion offuel in its manufacture, being the most critical from thispoint of view.2 The use of industrial by-products to replacenatural aggregates can induce important benefits in directsustainability, reducing landfill deposits and the exploitationof natural resources.3-6

Two kinds of electric steelmaking by-products mayconstitute sources for recycling: electric arc furnaceoxidizing slag (EAFS) and ladle furnace reducing slags(LFS). Production per tonnes (2207 Ib) of steel manufacturedamounts to approximately 0.16 tonnes (353 Ib) of EAFS and0.04 tonnes (881b) ofLFS.7 Both contain the normal oxides:silica, alumina, lime, and magnesia. The basicity of LFS(generated in the basic refining process) is higher than thatof EAFS (generated in the acid-refining process); and thelatter has a considerable amount of iron oxide, comprisingnearly half its total mass.

The recycling of these types of slags in the field -of ---construction and civil engineering is an important line ofresearch. Prominent studies over the last decade suggestthat they may be considered high-quality materials,8,9 hencethe need to investigate appropriate applications. Potentialvolumetric expansion is a notorious feature in the use ofboth types of slag; however, their weak hydraulicity after aircooling leaves these products outside the field of ecologicaland sustainable "slag cements."

Accordingly, one may distinguish between two categoriesregarding their application: first, their use in rigid mixtures,among which are masonry mortar, hydraulic concrete, orbituminous mixtures10; and secondly, flexible or nonrigid

matrixes, such as road bases, soil slag, and embankments,among others. The work presented in this paper is aninnovation in this field and centers on the application of slagtypes in hydraulic concrete matrixes made with portlandcement. It proposes the use of crushed and weathered EAFSas a coarse aggregate for concretes, in which the fine aggregateis also partially composed of EAFS (thereby avoiding its useas landfill material), limestone sand, and LFS. This innovativeuse of LFS requires a detailed analysis of its behavior as fillerin concrete mixtures, its hydraulic properties, and its inter-action with portland cement. It is also necessary to evaluatethe properties of concretes obtained in fresh and hardenedstates, as the results will demonstrate their effectiveness.The practical aspects of mixture proportioning are consideredessential to this work to make innovative use of these by-productsin civil construction and building, and employing approaches thatare technically and economically feasible.

RESEARCH SIGNIFICANCECertain steelmaking by-products, such as EAFS and LFS,

can both be used as components of normal concrete. Theproportioning and manufacture of this concrete calls forspecial considerations because of its low workability andrapid setting times. However, the general quality of well-manufactured slag concretes in terms of their mechanicalproperties is rather good.

EXPERIMENTAL INVESTIGATIONSeveral research projects, as reported in the scientific and

technical literature on the subject are at present and have inthe recent past been undergoing developments in this field,and are summarized in the following paragraphs.

Since the early 1990s, various authors11-19have proposedsystematic characterizations with a view to the possiblereuse of EAFS. In relation to this study, in the 1990s,some authors20,21have analyzed the use of EAFS as aggre-gates in concrete mixtures. Later on, the results obtainedby numerous authors22-28 all reported satisfactory results.Chang et al.29performed a carbonation curing to use EAFSin concrete mixtures. Qasrawi et ape proposed the use ofiron oxide scale and Etxeberria et al. 31proposed the use offoundry sand in the preparation of concrete. Faraone et al.32and Rodriguez et al.33 characterized high-quality mortarsusing EAFS.

ACi Materials Journal, V. 108,No.6, November-December20 II.MS No. M-2011-032.R2 received February 13,2011, and reviewed under Institute

publication policies. Copyright 2011, American Concrete Institute. All rightsreserved, including the making of copies unless permission is obtained from thecopyright proprietors. Pertinent discussion including author's closure, if any, will bepublished in the September-October 2012 ACi Materials Journal if the discussion isreceived by June 1,2012.

Juan Manuel Manso is Head of the Civil Engineering Department of the Universityof Burgos. Burgos. Spain. He graduated as a civil engineer from the University ofCantabria. Santander. Spain, and received his engineering doctorate from theUniversity of Burgos in 2001. His research interests include the reuse of steelmakingby-products in civil engineering applications as well as in the management of buildingand demolition wastes. and the field of polyester-resin concrete reinforced withnonmetallic bars.

David Hernandez is the Technical Director of the Technical and Scientific ResearchService of the UniversityofCantabria. Cantabria. SpainJrom which he also graduatedas a physicist, and he received his PhD in 2003 from the University of Navarra.Spain. His research interests include physical metallurgy and characterization ofmetallurgical slag (blast furnace and ladle furnace). among others.

Maria Milagros Losaiiez is the Director Manager of Gikesa in the Laboratory ofTesting in Building Materials and Civil Engineering, Gipuzkoa. Spain. She graduatedas a Construction Engineer in 1984 from the University of Burgos, as an Architect in1996from the University of the Basque Country. San Sebastian, Spain. and receivedher PhD from the University of the Basque Country in 2006. Her research interestsinclude mortar, concrete, and the use of by-products in cons/ruc/ioll.

Javier Jesus Gonzalez is a Full Professor of Materials Science at the IndustrialTechnology Engineering School of the University of the Basque Country. He graduatedas a mechanical engineer in 1976 from the University of Basque Country. as a civilengineer in 1982 from the Politechnical University of Madrid, Madrid, Spain. andreceived his PhD from the University of Canrabria in 1987. His research illterestsinclude the reuse of steelmaking by-products in civil engineering applications,mortars, concrete, and the mechanical behavior of engineering materials. .

Positive results were also obtained by Shi et aL34-36whenthey proposed investigating the potential hydraulic propertiesof LFS after chemical activation. Further works concerningLFS were published by Drissen and Art37 and Posch etaL,38which characterized the product as a materiaL

Slag recycling technology in Japan is highly advanced inalmost every possible area. Prime examples, among others,are offered in References 39 to 43.

It is also worth mentioning that Maslehuddin et aL,44Beshr et al.,45 and Pellegrino and Gaddo46 applied EAFSas a coarse aggregate in combination with a fine aggregatethat was a natural product. These approaches produced high-quality concrete, and Pellegrino and Gaddo46 proposed amixture proportioning adjusted to Bolomey's curve.

The work of Khokhar et al.47is also relevant in the field ofconcrete mixture designs containing mineral additions.

Some works of the present authors48-51reported the useof EAFS, both as a coarse and fine aggregate. The results interms of strength and durability were favorable.

MaterialsWater and cement-Urban mains water supply: pH

= 7.5; soluble salts = 90 mglL (0.006 Ib/ft3); chlorides= 19 mglL (0.001 Ib/ft3); sulfates = 13 mglL (0.0008 Iblft3); hydrocarbons = 9 mglL (0.0006 Ib/ft3); and portlandcement is Type 1142.5 R (refer to Table I for principalcharacteristics) .

Limestone sand-Crushed limestone sand was usedas a suitable fine aggregate. Its grading is detailed inTable 2, as it has a fineness modulus of approximately 2.5,and its apparent specific gravity is 2.7 Mg/m3 (1671b/ft3). Its

chemical composition is mainly calcium carbonate (>90%)with silica, alumina, and magnesia in lower proportions.

EAFS- The EAFS used in this study had to undergo thefollowing processes prior to its use:

The reduction of its original size after cooling (piecesfrom 0.1 to 20 kg [0.22 to 441b]) to standard aggregatesizes after moderate primary crushing to maximumsizes of 0.5 in. (12.5 mm);The magnetic elimination of metallic iron (sometimesin proportions of up to 20%); andWeathering for a minimum of 14 weeks, including dailyirrigation.

The physico-chemical properties of this slag and its gradingare shown in Tables 2 and 3.

Spontaneous weathering is an inexpensive procedurethat ensures the volumetric stability of EAFS necessaryin its use as a coarse aggregate in concrete mixtures. Thematerial is laid out and cured in thin layers, which are turnedevery week. A subsequent test performed in accordancewith ASTM D479252 demonstrates and verifies that theexpansivity does not exceed the standard limit value of 0.5%proposed by the ASTM D2940.53

A maximum aggregate size of 0.5 in. (12.5 mm) wasspecified in this work for the following reasons: I) thespecimen sizes used in the test (cylinders and cubes of 100 mm[4 in.] maximum length); and 2) current applications forthis type of concrete are employed in precast structures forurban use (curb stones, flagstones, balustrades, banisters,barriers, and so on) in which the maximum aggregate size isclassically 0.5 in. (12.5 mm).

The fine fraction from the moderate primary crushing ofEAFS is in general too large to be used as fine aggregateaccording to ASTM C33/C33M54; Fig. I shows theappearance of these EAFS fine particles. Hence, the mixtureof this EAFS fine fraction with limestone sand or othermineral products allows one to obtain a suitable fine fractionof aggregate, and therefore a high-quality concrete in termsof porosity and mechanical strength.55.56

LFS-The LFS discussed in this paper was subjected tothe following processes prior to its use in concrete:

Weathering for some days accompanied by waterirrigation to hydrate the free lime and to produce thedisintegration of the as-cooled particles sized up to I in.(25 mm); andThe elimination of metallic iron by magnetic proceduresand final sieving through a No. 30 (0.6 mm [0.02 in.])sieve to obtain the quality of material fineness suitablefor this application, whereas fractions larger than0.6 mm (0.02 in.) can be ground or reweathered.

The main physical and chemical properties of LFS aresummarized in Table I.

The weathering of LFS is _performed to hydrate the'"erFreactive free TIiniri - the- foftr1of' calcilim' 'oxide; .producing portlandite (calcium hydroxide) in a slightlyexothermic reaction. Simultaneously, this reaction producesa volumetric expansion, which leads to total disintegrationof particle sizes into a dusty form, similar to cement in its

Specific gravity, Blaine, mZ/kgComposition percent and properties CaO SiOz Ah03 Fez03 MgO Others S03 Free MgO Free CaO Mg/m3 (lb/ft3) (ftz/lb)Portland cement 62 21 5 3.5 1.5 1 2.7 - 3.3 3.13 (93) 410 (2002)

LFS 58 17 12 - 10 1.5 1 3 to 4 10 to 20 2.65 (64) 206 (006)

Sieve size, Coarse EAFS, Coarse ASTM C33/C33M, FineEAFS, Limestone sand, Fine ASTM C33/C33M,mID (in.) ASTMNo. wt.% passing wt.% passing wt.% passing wt.% passing wt.% passing

19.6 (0.75) 3/4 in. 100 100 - - -

12.5 (0.50) 1/2 in. 94 90 to 100 - - -

9.5 (0.37) 3/8 in. 64 40 to 70 100 100 100

4.8 (0.19) No.4 I o to 15 96 99.8 1002.4 (0.09) No.8 0.2 o to 5 68 85.2 95 to 1001.2 (0.05) No. 16 - - 42 56.9 80 to 100

0.6 (0.025) No. 30 - - 26 39.1 50 to 85

0.3 (0.0125) No. 50 - - 17 28.4 25 to 60

0.15 (0.00625) No. 100 - - 9.8 22.2 10 to 30

0.075 (0.003125) No. 200 - - 5.6 18.2 -

Property Coarse slag Fine slag

Size, mID (in.) 4 to 12.5 (0.16 to 0.5) o to 4 (0 to 0.16)Proportion after primary crushing, % 76 24

Apparent specific gravity, Mg/m3 (lb/frJ) 3.35 (207) 3.70 (228)

Porosity, % 9.7 13.5

Water absorption, % 2.88 3.65

Los Angeles 10sslMicro Devalloss, % 18 14

Expansion average (ASTM D4792), % 0.20 0.25

Sum of iron oxides Si02 CaO AI203 MgO MnO Others

42.5 15.5 24 7.5 5 4.5 I

appearance. Subsequent long weathering of several weeks ofLFS leads to the carbonation of portlandite,57 but this factoris incidental to the use of LFS due to the agglomeration ofparticles produced. The free magnesium oxide containedin LFS remains unreactive for long periods of time, andspontaneous hydration requires several years.

The most frequent particle sizes of LFS, using the Malvernanalysis, are in the ranges of 5 to 811m and 50 to 80 11m(1.96x 1Q-4to3.15 x 10-4in. and 1.96 x 1O-3to3.l5 x 10-3in). Thescanning electron microscopy (SEM) image in Fig. 2 showstwo types of pieces: single particles of a few microns in size,and particles or aggregates sized 50 to 80 11m(1.96 x 10-3 to3.15 X 10-3 in.). The results of the sieve analysis wereless significant: the No. 100 retains less than 10% of totalmass, whereas the No. 200 retains approximately 30% ofthe total mass.

In relation to its Glwmical4>asicity values (two units) as thequotient between the CaO and the Si02 + Al203, the work ofPosch et aP8 indicates the presence of spinel (minor), AC3(major), A7Cl2 (medium), and free CaO (medium) in thisslag. The results of LFS X-ray diffraction analysis shown inTable 4 and Fig. 3, in combination with chemical analysis,confirm the predictions based on the work of Posch et al.38and,in addition, reveal the presence of nonhydraulic allotropicforms of dicalcium silicate as the other main compounds.

Concrete mixturesConcrete mixtures were prepared according to certain

initial or general conditions based on previous experience

(refer to the D-1 reference mixture in the first data column inTable 5), any deviation from which relates to the particulartype of research activities (remainder of mixtures onTable 5). The envisaged workability is typical of concretesthat are used for precast pieces in the construction industry,where energetic concrete compaction is the norm; also, theuse of EAFS as coarse and fine aggregate leads to low valuesin the slump. The use of plasticizer admixtures is advised ifan increase in concrete fluidity is considered necessary.

Initial conditions of mixtures:Cement content = 350 kg/m3 (21.6Ib/ft3);

Fig. 2-SEM micrography of LFS.S - 1

200 s. AS I - -150 My ,

In>-I-

u;Z 100wI-

~50

20 30 40 50 60BRAGGS ANGLE (201

Component Formula Key %

Diopside CaMg(Si03h D a.Merwinite Ca3MgSi20g Mw a2

Wollastonite CaSi03 W a3

Larnite, bredigite, ingesonite Ca2Si04 L, B, In ~Calcium-olivine Ca2Si04 0 as

Spinel MgAh04 S 2

Mayenite CaI2A114033 My 8

Calcium aluminate CaAh04 AC 2

Tricalcium aluminate Ca3Ah06 T 7

Jasmundite Call(Si04)402S J I

Fluorite. -- -_ .......... - - -_.~. _._- ----- --

CaF2 F 2

Iron-magnesium oxides (wustite) (Fe,Mg)O I 2

Portlandite Ca(OH)2 P 16

Peric1ase MgO M 3

Aluminium metallic AI A 2

Water and cement (apparent water-cement ratio (w/c:0.6 to 0.8;Workability: 30 to 60 mm (1.2 to 2.4 in.) slump in theAbrams cone test;

Mixture ratio coarse aggregate/fine aggregate/cement =3/3/1;Target mean compressive strength at 28 days = 35 MPa(5.08 ksi); andNo admixtures.

EAFS was introduced into the mixtures with a low degreeof humidity and its moisture content was negligible in theaforementioned mixture proportions. The fundamentalcontrol parameter evident in the manufacture and applicationof these mixtures, when using a porous and sharp aggregatesuch as EAFS, is their consistency-workability measuredby the slump test in the Abrams cone. 58 It is necessary toreconsider the significance of a conventional w/c in concretemade with the usual type of cement (without mineraladditions) and aggregates (siliceous and limestone) inrelation to this research. In this case, the EAFS aggregateabsorbs and retains a significant quantity of water, thecement contains a proportion of inert mineral filler, and theinclusion of LFS as fine aggregate in mixtures demandsadditional water due to its low particle size that almost rivalsthat of cement.

LFS is a new material and little is known about its use inhydrauli"cmixtures. Its"behavior when undergoing weatheringas a raw material has been analyzed,57 but its behavior whenused with portland cement in concrete mixtures that requirestrength and durability is uncertain.

A total of five different mixtures were manufacturedand tested. Initially, two mixtures (Mixtures D-1 andD-2) were prepared-followed later by Mixtures D-3 andD-4 and finally Mixture D-5. The batches had a mass ofapproximately 30 L (1.06 ft3), from which 24 cubic specimens(100 x 100 x 100 mm [4 x 4 x 4 in.]) were poured into molds,left to set for 24 hours, and then demolded and placed in amoist room at 200e (68F) at 98% relative humidity.

The criteria to fix the proportions in these mixtures is anattempt to conduct an extensive survey on well-performedmixtures containing EAFS, limestone sand (LS), and LFSas fine aggregate. The cOarse aggregate is the same (EAFS)type and proportion in all the mixtures. Taking into accountthe different densities of the fine aggregate components(EAFS, LS, and LFS), the quantity of the ingredients per m3(ft3) of concrete in Table 5 (columns marked with t) do notclearly indicate the initial criteria, and only the proportionsin each different batch (columns marked with *) clarify theprecise criteria of proportioning.

In this study, Mixture D-1 is the reference mixture. Asshown in Table 5, the coarse aggregate was an EAFS gravelsized 4 to 12.5 rom (0.16 to 0.50 in.), totaling 50% of theoverall aggregate weight. The fine aggregate was composedof EAFS fine fraction added to limestone sand in the sameproportions, leading to a suitable grading based on previous

.......e;1(:perien

D-1 D-2 D-3 D-4 D-5

Mixture * t * t * t * t * tWater, kg (lb) 6 (13.2) 215 (474) 7 (15.4) 250 (551) 6.5 (14.3) 240 (529) 8(17.6) 270 (595) 5.6 (12.3) 215 (474)

Cement, kg (lb) 10 (22) 360 (794) 10 (22) 355 (783) 10 (22) 370 (816) 10 (22) 340 (750) 8 (17.6) 305 (672)

wle 0.6 0.7 0.65 0.8 0.7

LFS, kg (lb) 0(0) 7.5 (16.5) 265 (584) 7.5 (16.5) 280 (617) 15 (33) 515(1124) 7.5 (16.5) 285 (628)

imestone 15 (33) 540 (1190) 7.5 (16.5) 265 (584) 0(0) 0(0) 0(0) 0(0) 0(0) 0(0)Fine aggregate 0/5, andkg (lb)

EAFS 15 (33) 540 (1190) 15 (33) 530 (1168) 22.5 (50) 830 (1830) 15 (33) 515 (1124) 22.5 (50) 860 (1896)

Coarse aggregate EAFS 30 (66) 1080 (2381) 30 (66) 1060 (2337) 30 (66) 1110 (2447) 30 (66) 1030 (2249) 30 (66) 1150 (2535)4/12.5, kg (Ib)

Abrams cone slump, mm (in.) 20 (0.8) 35 (1.4) 5 (0.2) 45 (1.8) 5 (0.2)-First subcolumn is mass of each component used in mixture.tSecond subcolumn is dosage per cubic meter of concrete.

high fineness of the LFS, which in this case gave a result inthe interval of 30 to 60 rnm (1.2 to 2.4 in.). The presence offine LFS particles improved its workability.

In a second step, Mixtures D-3 and D-4 were prepared. InMixture D- 3, the limestone sand in Mixture D-2 was replacedby EAFS sand and, in hindsight, the planned decrease in thewlc to maintain workability (less fineness, wlc = 0.65) wasdeemed an error: the slump decreased to 5 mm (0.2 in.) dueto the particular geometry of fine EAFS. In Mixture D-4, thelimestone sand in Mixture D-2 was replaced by LFS (finerand blunt), and the wlc was increased to a high value (0.8),which gave an acceptable slump of 45 rnm (1.8 in.).

In a third step, in Mixture D-5, which has Mixture D-3as its reference, the cement content was decreased to300 kg/m3 (18.5 lb/ft3) (-15%) with a slow increase in thewlc up to 0.7 to maintain a suitable amount of water. Theresults for workability in this case were, as expected, verysimilar to the original D-3 mixture (5 rnm [0.2 in.]).

Considering the values of the wlc and the obtained slumps,this paper presents a first characteristic in the behavior ofslags in concrete mixtures. The role of LFS is next to thatof the lime in hydraulic mixtures, increasing the plasticityand the demand of water due to its fine, blunt, and smoothparticles. However, in contrast to this, the crushed EAFSis porous and its particles are angular with sharp edges;both of these factors lead to a decrease in workability,especially when the fine aggregate has this morphology.Mixtures D-3 and D-5 with higher EAFS fine aggregatecontents have the lowest slump (5 mm [0.2 in.]), whereasMixture D-4 with the high LFS content presents the higherslump (45 mm [1.8 in.]).

EXPERIMENTAL RESULTS AND DISCUSSIONSetting properties

Rapid setting was observed during the mechanical mixingof the components in some cases; the concrete mixerbecame blocked after a few minutes, making a satisfactorymixture impossible. Initially, this situation was observed inMixture D-4--which has the highest content of LFS-butalso in Mixture D-3 and then in Mixture D-5.

It was decided that a similar test to that prescribed inthe ASTM C191-0859 (setting times in portland cement)should be applied to different proportional mixtures ofportland cement and LFS. A paste of normal consistencywas prepared, taking the PC-LFS mixtures as a compoundcement in which the LFS could be considered an addition

Table 6-Mixture setting time measured inVicat apparatus

Mixture D-1 D-2 and D-3 D-4 D-5

Weight ratio LFSIPC 0/10 7.5/10 15/10 7.5/8

Weight ratio LFSIPC, % 0/100 43/57 60/40 49/51

Water, % weight 24 27 29.5 28

Initial setting, minutes 114 42 18 16

Final setting, minutes 190 70 41 39

to the clinker. The proportions between PC and LFS used inthese normal-consistency pastes were the same proportionsof both materials contained in Mixtures D-I to D-5. Theresults of the setting times recorded in these tests are shownin Table 6.

The results on the normal-consistency paste correspondingto Mixture D-I reflects the initial and final setting of theportland cement used in this work (refer to Tables I and 6).Pastes reflecting the proportions of LFS to PC in the othermixtures show shorter initial and final setting times. Thiscorresponded with Mixtures D-4 and D-5, which were themost likely to undergo this problem due to their higher LFSIPC ratios. Setting times were longer in Mixtures D-2 andD-3 than in Mixtures D-4 and D-5, but also clearly below thesuitable values demonstrated by Mixture D-I. Hence, it isimportant to consider the risk of overly rapid setting, whichcan make laying of these concrete Mixtures D-2 to D-5 inpractical construction difficult or even impossible. It canbe confidently stated from an analysis of the data presentedin Table 6, that it is inadvisable to exceed the proportion40/60 in the LFSIPC ratio.

A recent paper by the authors57 has shown the results ofsevere weathering and hydration on several types of LFS_The calcium silicates of LFS (in their allotropic forms)present low to zero hydraulicity (without the use of chemicalactivators), but the calcium aluminates (monocalciumaluminate, tricalcium aluminate, and mayenite) can presenta considerable degree of hydraulicity. Therefore, theproportion of reactive calcium aluminates contained in theoriginal portland cement (tricalcium aluminate proposed inthe Bogue formulation) is increased by its mixture with LFS,and this, it may be hypothesized, could be the possible causeof the observed rapid setting. The addition of supplementarycalcium sulfate provides a viable solution to the questionsraised and confirms the diagnosis.

Mixture 0-1 0-2 0-3 0-4 0-5

Bulk specific gravity, Mglm3 (lb/ft3) 2.73 (169) 2.73 (169) 2.84 (175) 2.69 (166) 2.83 (175)

t\pparent specific gravity, Mglm3 (lb/ft3) 3.06 (189) 3.09 (191) 3.18 (196) 3.12 (193) 3.11 (192)

Physical data Water absorption, % weight 5.5 6.3 5.7 7.2 5.6

!Total porosity, % 14.3 16.3 15.1 18.5 14.8

Matrix porosity, % 9 11.3 8.9 13.7 8.4

f\t 7 days 35.4 (5.1) 39.8 (5.8) 55.3 (8) 24.9 (3.6) 34.1 (4.9)

~t 28 days 46.6 (6.8) 52.9 (7.7) 60.4 (8.8) 31.5 (4.6) 47.6 (6.9)

Compressive strength, MPa (ksi) f\t 90 days 52.2 (7.6) 58.3 (8.5) 64 (9.3) 35.1 (5.1) 51.2(7.4)

~t 180 days 54.9 (8) 62.8 (9.1) 70.6 (10.2) 37.3 (5.4) 53.7 (7.8)

f\t 360 days 58.9 (8.5) 67.2 (9.7) 80.5 (11.7) 39 (5.7) 54.2 (7.9)

Certainly, the addition of a small quantity (2% on weightof cement) of calcium sulfate (gypsum) to Mixtures D-4 andD-5, and 1% to Mixtures D-2 and D-3 slowed lead timesetting to usual values of over 3 hours. This procedureslowed an overly rapid hydration of aluminates from PCand LFS leading to the formation of primary ettringite (referto Hewlett60).These observations raise pertinent questionsrelating to the future use of LFS in hydraulic mixtures.

Physico-mechanical properties of hardened concreteTable 7 presents the physical data regarding densities,

water absorption, and porosity of the different mixturesemployed in the tests. EAFS is a heavy and porous material,and when it is used as aggregate it will produce higher densityand higher porosity values than those commonly found incommercial hardened concrete. The fifth row of Table 7 citesmatrix porosity as the difference between the total porosityof mixtures measured by the classical immersion procedureand detailed in the previous row and the porosity of its EAFScoarse and fine aggregate specified in Table 3.

Mixtures D-3 and D-5 are the densest of the series, whichis understandable, as both Mixtures D-3 and D-5 containlarger amounts of heavy EAFS. Moreover, Mixture D-4 isthe most porous; it has the highest ratio (w/c = 0.8)-a valuethat is clearly excessive.

Compressive mechanical tests were performed onthe 100 x 100 x 100 mm (4 x 4 x 4 in.) cube specimens at 7,28, 90, 180, and 360 days after pouring the fresh concrete.A factor of approximately 0.8 is used to estimate coarsecorresponding values of compressive strength in equivalentcylindrical specimens of 150 x 300 mm (6.7 x 11.8 in.).Table 7 lists the results of the mechanical compression test.

The portland cement contained reactive calcium silicatesand aluminates, and the LFS contained, at the outset of thetest, inert calcium s!1i~ll.t~s,_r:~~.ftiy_~__G.aJcium aluminates(AC3, Mayenite), and portlandite. The Blaine fineness ofPC is 400 m2/kg (1953 ft2/lb) and the fineness in the LFS islower at 200 m2/kg (977 ft2/lb). The strength results obtainedin Mixtures D-l, D-2, and D-3 demonstrate hydraulicreactivity of LFS in these types of concretes, probablyinteracting and catalyzed by the components and hydraulicreactions of Pc. The presence of reactive aluminates in LFSlargely contributes to the short-term compressive strength ofthe mixtures.

The correct proportioning of these types of concretemixtures, containing very porous EAFS aggregate andrelevant proportions of LFS as fine aggregate, is a very

important consideration related to their ultimate design,manufacture, and efficiency of the modes of use in whichthey are employed. This question, which is discussed inthis section, is not accurately addressed in the scientificand technical literature on the subject. To obtain usefulresults, it is necessary to-design these mixtures on the basisof two conditions: the matrix porosity, and the suitable andequilibrate content between the very fine fraction of inertaggregates (with a size under 0.063 mm [0.025 in.] passingthe No. 200 sieve) and the hydraulic reactive fine fraction,provided by the portland cement and the remainder ofreacti ve materials as LFS.

In this paper, the authors propose to evaluate the hydraulicactivity of LFS, stating that a fraction of the total LFS massin mixtures is active and the remainder of the LFS willbe considered inert. To quantify the question, the initialhypothesis cites that the hydraulically active fraction isa part of the finer fraction (passing the No. 200 sieve) forLFS, and the thick particles retained by the No. 200 sieve areinert. Thus, this LFS may be characterized by the followingproportions and properties:

A less fine inert fraction (30% of total weight retainedby a No. 200 sieve);A fine fraction that is hydraulically active (approximately40% of the total weight); andA fine inert fraction (approximately 30% of the total weight).

These numerical values are proposed on the basis of thisresearch team's experience with LFS and on the composi-tions and proportions presented in Table 4. They will beconfirmed or otherwise by the results of the calculationsperformed on the concrete mixtures in this paper.

Mixture D-I-Reference Mixture D-l may be considereda "conventional" concrete mixture suitable for use in themanufacture of precast elements if a low slump is required.Its density is higher than co"mmercial-coiicrete -due "to- tne" _. - ._- - - .use of EAFS aggregate. The evolution of its strength overtime (refer to Fig. 2) is understandable when observing thatcapillary water retained in EAFS results in a delayed curingand, therefore, the mixture may be considered well-gradedand well-proportioned in relation to its water and inertfines content. This mixture demonstrates a good strength.evolution in compression (refer to Table 7) of 46.6 MPa(6.8 ksi) at 28 days and 58.9 MPa (8.5 ksi) at 1 year.

The matrix porosity in Mixture D-l has been calculatedat 9% (refer to Table 7); values below 10% are consideredexcellent, and tolerable at below 12%. If the porosity

exceeds 12%, the compressive mechanical strength clearlydecreases, as can be observed in Mixture D-4.

The amount of effecti ve water can be estimated as 163 Um3(0.163 ft3/ft3) of concrete by subtracting the EAFS absorbedwater (2.88% or 3.65%, refer to Table 3) from the total wateradded to the mixture. Hence, the effective w/c in this mixtureis 163/360 = 0.45, which is consistent with a matrix porosityof9%.

The amount of inert fines (passing the No. 200 sieve) in thismixture is approximately 145 kg/m3 of concrete (9.0 Ib/ft3),yielding these numerical data from the addition of the finesprovided by: a) cement (5% limestone filler by weight),18 kg (39.7 Ib); b) limestone sand (18.2% fines that pass theNo. 200 sieve by weight), 98 kg (216 Ib); and c) EAFS fineaggregate (5.6% of EAFS fine fraction by weight), 30 kg(66.llb).

This value of 145 kg/m3 (9.0 Ib/ft3) is reasonablycorrect according to the experience of concrete makersand researchers, and even Article 31.1 of the SpanishStandard EHE-0858 sets the maximum value for inertfines in normal concrete at 175 kg/m3 (10.8 Ib/ft3).This value should depend, in a first approach, on themaximum aggregate size and on the cement contentof the concrete. An ideal value of inert fines ofapproximately 150 kg/m3 (9.3 lb/ft3) is considered forthis type of concrete, with a maximum aggregate sizeof 12.5 mm (0.5 in.) and a cement content of 350 kg/m3(21.6Ib/ft3).

Mixture D-2-Mixture D-2 contained an LFS amountthat replaced half the limestone sand in Mixture D-l. Thisaddition of LFS implied an increase in water demand tomaintain workability due to its increased fineness; in fact, aratio of w/c = 0.7 leads to a slump of 35 mm (13.8 in.). Theeffective water, calculated as in Mixture D-l, was 200 kg/m3(12.3 lb/ft3), and the effective w/c was estimated at 200/355= 0.54, a value higher than the Mixture D-l value, whichcorresponded to a matrix porosity result of 11.3%, asreflected in Table 7. These data (effective w/c versus matrixporosity) obtained for Mixtures D-l and D- 2 suggest a singleand direct correlation between both factors.

The amount of total inert fines had to be increased in thismixture with respect to Mixture D-l, which related to theLFS inert fraction. Based on the aforementioned hypothesisregarding LFS composition, it is possible to estimate anamount of 175 kg/m3 (10.8 Ib/ft3) of inert fines (passingthe No. 200 sieve) in this mixture, which is well withinthe safety margin, while it maintains a value of matrixporosity below 12%. The inert fraction of fines furnishedby the LFS (approximately 30% of added LFS by weight)is 80 kg/m3 (4.9 lb/ft3), which replaces the limestone sandfines (49 kg/m3 [3Ib/ft3] passing the No. 200 sieve); the finesfrom the cement and the EAFS fines are similar to those inMixture D-l.

The mechanical compressive strength of Mixture D-2 ishigher than that of Mixture D-l over time, according to thedata listed in Table 7, reaching a value of 52.9 MPa (7.7 ksi)at 28 days and 67.2 MPa (9.7 ksi) at 1 year. Considering thisfact and the negative impact on the strength of the matrixporosity value (slightly higher than that of Mixture D-l),one can deduce that LFS exhibits an outstanding degreeof hydraulic properties. According to the hypothesis givenfor LFS, the amount of reactive LFS is 105 kg (231.5 Ib)but, undoubtedly, as a conglomerate that is less effectivethan the portland cement. To summarize, Mixture D-2 may

be considered a good, reasonable quality slag concrete,containing a slight excess of water and inert fines (175 kg/m3[10.8 Ib/ft3]) due mainly to those furnished by the LFS.

Mixture D-3- The same amounts of LFS and PC andthe same LFSIPC ratio are maintained in Mixture D-3as in Mixture D-2, with the added innovation that all theMixture D-2 limestone sand content is replaced by EAFSfine aggregate-a "coarse sand" with fewer fine particlesthan the limestone sand. The design for Mixture D-3 hadless water (w/c = 0.6) and the consistency slump was only 5mm (0.2 in.). The water absorbed by the additional porousEAFS fine aggregate compensates to excess the capillarywater demand of the replaced limestone sand.

The effective w/c of Mixture D-3, calculated as inMixture D-l, was 178/370 = 0.48 and the matrix porositywas 8.9%; both values were very similar to those ofMixture D-l. Taking into account the same considerationsas for Mixtures D-l and D-2 on the calculation of theinert fine fraction weights, the total amount of inert fineswas 145 kg/m3 (9.0 Ib/ft3) in Mixture D-3, as in Mixture D-1.Hence, it would appear prudent to estimate some similaritybetween the performances of Mixture D- 3 and Mixture D-l.Additionally, it was estimated that Mixture D-3 had anamount of reactive LFS of 110 kg/m3 (6.8 Ib/ft3), accordingto the initial hypothesis on LFS composition.

In summary, Mixture D-3 may be considered wellgraded, of excellent strength, and with an adjusted watercontent that produces low workability. After the first week,the mechanical strength was 55.3 MPa (8 ksi), while themaximum value after 1 year was 80.5 MPa (11.7 ksi)in 100 x 100 x 100 mm (4 x 4 x 4 in.) cubic specimens,equivalent to approximately 65 MPa (9.4 ksi) in theconventional 150x 300 mm (6.7 x 11.8in.) cylindrical specimens,using a conversion factor of 0.8 as stated previously.

These results may be explained by considering thedevelopment of hydraulic reactivity in the LFS. Thehydration of calcium aluminates contained in the LFS wasprobably the key to understanding the high short-termstrength of Mixture D-3. The rapid setting observed inMixtures D-3 and D-2 may be considered as the start of amore complete hydraulic reaction ofLFS calcium aluminatesin these mixtures, which demonstrate a positive result inrelation to strength. It is hypothesized that the differences,relating to strength, between Mixtures D-3 and D-2 weredue to the matrix porosity values and the proportions of inertfines; Mixture D-3 was a better graded and proportionedmixture than Mixture D-2. Mixtures D-l and D-3 weremixtures iliat performed very well, whereas the workability ofMixture D-3 was adversely affected by the higher proportionof EAFS sand.

Mixtures D-4 and D-5-Mixtures D-4 and D-5 containedhigher proportions of LFS than the previous mixtures; theLFSIPC ratio was in excess of 40/60. As previously stated,rapid setting and the presence of potentially expansivecompounds in the LFS, such as magnesium oxide, createdan unstable situation, which was the reason for proposingthe limit at 40/60.

Mixture D-4 was similar to Mixtures D-2 or D-3, except forthe replacement of a portion of the fine aggregate with LFS.Likewise, Mixture D-4 was similar to Mixture D-l exceptfor the total replacement of the limestone sand by LFS. TheLFSIPC ratio at 60/40 in Mixture D-4 was too high, in that itincreased the demand for water to obtain good workability.The rapid setting in Mixture D-4 was foreseeable due to the

excess LFS. Its consistency was adequate (45 mm [1.8 in.]),but it had the greatest matrix porosity and the lowest densityof the entire set of specimen mixtures. The values for matrixporosity (13.7%) and the effective w/c (222/340 = 0.65) inMixture D-4 were obviously too high.

The evolution of compressive strength was correct butthe values at 7, 28, 90, 180, and 360 days were the lowestin the set, which demonstrate that Mixture D-4 performedpoorly in comparison to the other mixtures, although thevalue of the 28-day compressive strength of 31.5 MPa(4.6 ksi) (equivalent to 25 MPa [3.6 ksi] in a cylindricalspecimen) was acceptable. The excessive content of LFSleads to values of 200 kg/m3 (12.3 Ib/ft3) for the inert finesin Mixture D-4. As similar calculations had been proposedfor previous mixtures in the series, this amount of inert fineswas considered unsafe in view of the strength and durabilityrequirements of the mixture. The strength maintainedacceptable values due to the hydraulic properties of PC andLFS, but the design of the mixture was too loose.

Mixture D-5 can be compared to Mixture D-3 but, in thiscase, the portland cement content had been reduced withoutany reduction in the LFS. As a consequence, the LFS/PC ratiowas virtually 50/50 and exceeded the recommended value of40/60. The original w/c was higher than in Mixture D-3, butthe reduction of cement led to a lower amount of water and alow slump consistency of 5 mm (0.2 in.), which was similarto Mixture D-3. The effective w/c was adequate-151/305= 0.5-and the matrix porosity (8.4%) of Mixture D-5 wasvery close to the values for Mixture D-3, and a positiveperformance was inferred from these results.

The estimated amount of inert fines (140 to 150 kg/m3[8.6 to 9.3 Ib/ft3]) was acceptable, but its lower cementcontent decreased its mechanical strength, which was lowerthan Mixture D-3 but similar to Mixture D-l, and evolvedwell over time. Mixture D-5 was also a well-graded mixturethat performed quite well, but in which the LFS/PC ratiowas excessive.

Finally, it seems that the aforementioned hypothesis statedin Section 6 is acceptable, with regard to the proportions ofLFS composition and its behavior as a potentially reactivematerial, when used in these concrete mixtures. The authorsmust underline that these hypotheses are based on experience,and on the chemical and crystalline composition of thisspecific LFS, and that this is invalid for other applications ofLFS with different chemical and crystalline structures otherthan those cited and discussed herein. Additionally, after theresults of this work, the authors propose an amount for thistype of LFS that should not exceed 200 kg/m3 (12.3 Ib/ft3)as the optimum content for this type of LFS in concretescontaining in excess of 300 kg of portland cement per m3(18.5 Ib/ft3).

CONCLUSIONSThe results of these tests raise the following conclusions

and comments:After suitable crushing and subsequent weathering, theEAFS is converted into an excellent coarse aggregate forconcrete. Its high density produces heavy concrete, andits high water absorption produces a delayed curing inthe mixtures, which increases the long-term compressivestrength. The fine fraction of EAFS can also be used andmixed with other types of fine aggregates.The LFS used in this study can be considered a"cementitious" material in conjunction with portland

cement. Other kinds of LFS with different calciumaluminates contents should perform differently. Ingeneral, an increase in the short-term compressivestrength and a decrease in the setting time of concretesmay be expected according to their use.The inclusion of LFS in its dusty form in concrete isonly advisable under appropriate conditions, because itschemical reactivity in the presence of portland cementmust be taken into account. It is recommended thatthe proportions of LFS versus Type I portland cementshould not exceed a ratio of 40/60 by weight, and thatthe total amount of LFS should not exceed 200 kg/m3 ofconcrete (12.3 Ib/ft3).To design high-quality concrete using steelmakingslags, in the experience of this research group, thefollowing rules should be respected:

Appropriate primary crushing and weathering ofEAFS;Suitable proportioning between the coarse and finefraction aggregates;Adequate use of fine inert aggregates, such assiliceous or limestone sand;Correct preparatory treatment and limited amountsofLFS; andLimited initial slump in consistency. Plasticizeradmixtures may subsequently be added to reachhigher workability.

ACKNOWLEDGMENTSThe authors wish to express their gratitude to the Spanish Ministry of

Science and Technology for supporting this work through Research ProjectMAT 2004-02205.

REFERENCESI. Hendriks, C. A. et aI., "Emission Reduction of Greenhouse Gases from

the Cement Industry," Proceedings of the 4th International Conference onGreenhouse Gas Control Technologies, Interlaken, Austria, Aug. 30-Sept.2,1998, IEA GHG R&D Programme,UK.

2. "Energy Conservation Potential in the Cement Industry," Federal EnergyAdministration, Washington, DC, 1975. (available as NTIS PB 245159)

3. Akinmusuru, J. 0., "Potential Benefitial Uses of Steel Slag Wastes forCivil Engineering Purposes," Resources, Conservation and Recycling, V. 5,1991, pp. 73-80.

4. Naik, T. R., "Greener Concrete Using Recycled Materials," ConcreteInternational, V. 24, No.7, July 2002, pp. 45-49.

5. Bektas, F., and Wang, H., "Effects of Crushed Clay Brick Aggregateon Mortar Durability," Construction and Building Materials, V. 23, No.5,2009, pp. 19091914.

6. Mehta, P. K., "Global Concrete Industry Sustainability," ConcreteInternational, V. 31, No.2, Feb. 2009, pp. 45-48.

7. Palacios, J. M.; Arana, J. L.; Larburu, J. 1.; and Iniesta, L., "LaFabricaci6n del Acero (Steel Manufacture)," UNESID, 2002.

8. Geiseler, J., "Use of Steelworks Slags in Europe," Waste Management& Research, V. 16, No. 1-3, 1996, pp. 5963.

9. Motz, H.,-and Geiseler, J., "Products of Steel Slags, An Opportunityto Save Natural Resources," Waste Management, V. 21, No.3, 2001,pp. 285-293.

10. Pasetto, M., and Baldo, N., "Experimental Evaluation of High_. p.~r:f.9ITI!aD.~c;..!3_a~~Course _~!1sI)~c>a~Base ~sphalt Concrete with Electric

Arc Furnace Steel Slags," Journal of Hazardous'MaterieJs, V: 18 CZOIO;---- - ---pp. 938-948.

11. Cen, Y., and Chen, Q., "Experiment on Crushing EAF Slag," SEAISIQuarterly, V. 22, No.4, 1993, pp. 81-85.

12. L6pez, F. A.; L6pez-Delgado, A.; and Balcazar, N., "Physico-Chemical and Mineralogical Properties of EAF and AOD Slags," AfinidadLIll, V. 461, 1996, pp. 39-46.

13. Goldring, D. C., and Juckes, L. M., "Petrology and Stability of SteelSlags," lronmaking & Steelmaking, V. 24, No.6, 1997, pp. 447-456.

14. San Jose, J. T., "Reutilizaci6n y Valoraci6n en Obra Civil de Escoriasde Homo Electrico de Arco Producidas en la CAPV," Arte y Cemento,V. 124, No.6, 2000.

15. Luxan, M. P.; Sotolongo, R.; Dorrego, F.; and Herrero, E.,"Characteristics of the Slags Produced in the Fusion of Scrap Steel byEAF," Cement and Concrete Research, V. 30, No.4, 2000, pp. 517-519.

16. Vazquez-Ramonich, E, and Barra, M., "Reactivity and Expansion of.Electric Arc Furnace Slag in their Application in Construction," Materialesde Construccion, V. 51, No. 263-264,2001, pp. 137-148.

17. Frias Rojas, M.; Sanchez de Rojas, M. I.; and Uria, A., "Study ofthe Instability of Black Slags form EAF Steel Industry," Materiales deConstruccion, V. 52, No. 267, 2002, pp. 79-83.

18. Juckes, L. M., "The Volume Stability of Modern SteelmakingSlags," Mineral Processing and Extractive Metallurgy (Transactions ofthe Institution of Mining and Metallurgy, Section C), V. 112, No.3, 2003,pp.I77-197.

19. Dippenaar, R., "Industrial Uses of Slag (The Use and Re-use of Ironand Steelmaking Slags)," Ironmaking & Steelmaking, V. 32, No. I, 2005,pp.35-46.

20. A1izadeh, R. et al., "Utilization of Electric Arc Furnace Slag asAggregates in Concrete," Environmental Issue, CMI report, Tehran, Iran, 1996.

21. Baverman, C, and Aran Aran, E, "A Study of the Potential ofUtilising Electric Arc Furnace Slag as Filling Material in Concrete," Studiesin Environmental Science, V. 71, 1997, pp. 373-379.

22. Geyer, R. T.; dal Molin, D.; and Vilella, A. C. E, "Evaluation of theDurability of the Reinforced Concrete with Electric Arc Furnace Addition,"Congresso Annual Associar;ao Brasileira de Metalurgia e Materiais, V. 56,2001, pp. 127-136.

23. Moon, H. Y.; Yoo, J. H.; and Kim, S. S., "A Fundamental Study onthe Steel Slag Aggregate Concrete," Geosystem Engineering, V. 5, No.2,2002, pp. 38-45.

24. Shekarchi, M. et aI., "Study on Electric Arc Furnace Slag Propertiesto be Used as Aggregates in Concrete," CANMET/ACI InternationalConfe'rence on Recem Advances in Concrete Technology, Bucharest,Romania, 2003.

25. Shekarchi, M. et aI., "Study of the Mechanical Properties ofHeavyweight Preplaced Aggregate Concrete Using Electric Arc FurnaceSlag as Aggregate," International Conference on Concrete Engineering andTechnology, Malaysia, 2004.

26. Papayianni, I., and Anastasiou, E., "Concrete Incorporating HighVolumes of Industrial By-Products," Role of Concrete in SustainableDevelopment-Proceedings of International Symposium Dedicatedto Professor Surendra Shah, Aristotle University Greece. R. K. Dhir,M. D. Newlands, and K. A. Payne, eds., Sept. 2003, Dundee, UK, 2003,Thomas Telford Publishers, pp. 595-604.

27. Vazquez-Ramonich, E., and Barra, M., "Durability of Concretes withSteel Slag as Aggregates," Workshop on R+D+I in Technology of ConcreteStructures-A Tribute to Dr. Ravindra Gellu, Barcelona, Spain, Oct. 2004,pp.23-30.

28. Anastasiou, E., and Papayianni, I., "Standards for the Use of SteelIndustry By-Products as Aggregates for the Production of Concrete,"Proceedings of the 1st Hellenic Conference of EVIPAR on Utilization ofIndustrial By-products in Construction, 2005, pp. 347-356.

29. Chang J.; Wang S.; and Shao Y, "Manufacture of Electric ArcFurnace Slag Aggregate and Concrete through Carbonation Curing," KueiSuan Jen Hsueh Pao/Journal of the Chinese Ceramic Society, V. 35, No.9,2007,pp.1264-1273.

30. Qasrawi, H.; Shalabi, E; and Asi, I., "Use of Low CaO UnprocessedSteel Slag in Concrete as Fine Aggregate," Construction & BuildingMaterials, V. 23, 2009, pp. 1118-1125.

31. Etxeberria, M.; Pacheco, C; Meneses, 1. M.; and Berridi, I.,"Properties of Concrete Using Metallurgical Industrial By-Products asAggregates," Construction & Building Materials, V. 24, No.9, 2010,pp.1594-1600.

32. Faraone, N.; Tonello, G.; Furlani, E.; and Maschio, S., "SteelmakingSlag as Aggregate for Mortars: Effects of Particle Dimension onCompression Strength," Chemosphere, V. 77, 2009, pp. 1152-1156.

33. Rodriguez, A.; Manso, J. M.; Aragon, A.; and Gonzalez, J. J.,"Strength and Workability of Masonry Mortars Manufactured with LadleFurnace Slag," Resources, Conservation and Recycling, 'V. 53, No. -11, Sept-. -2009,pp.645-651.

34. Shi, C, and Quian, J., "High Performance Cementing Materials fromIndustrial Slags-A Review," Resources, Conservation and Recycling,V. 29, No.3, 2000, pp. 195-207.

35. Shi, C, "Characteristics and Cementitious Properties of Ladle SlagFines from Steel Production," Cement and Concrete Research, V. 32, No.3,2002, pp. 459-462.

36. Shi, C, and Hu, S., "Cementitious Properties of Ladle Slag Finesunder Autoclave Curing Conditions," Cement and Concrete Research,V.33,No. 11,2003,pp. 1851-1856.

37. Drissen, P., and Art, K. J., "Entstehung feinkornigerPfannenschalcken," Rep. Forshungsinstituts, FEHS, V. 7, No.1, pp. 12-16.

38. Posch, W.; Presslinger, H.; and Hiebler, H., "Mineralogical Evaluationof Ladle Slags at Voestalpine Stahl GmbH," lronmaking & Steelmaking,V. 29, No.4, 2002, pp. 308-312.

39. Kanagawa, A., and Kuwayama, T., "The Improvement of Soft ClayeySoil Utilizing Reducing Slag Produced from Electric Arc Furnace," DenkiSeiko, V. 68. No.4, 1997, pp. 261-267.

40. Morino, K., and Iwatsuki, E., "Durability of Concrete Using ElectricArc Furnace Oxidizing Slag Aggregates," Proceedings InternationalConference, N. Swamy, ed., Sheffield, UK, 1999, pp. 213-222.

41. Watanabe, T.; Okamoto, T.; and Takahashi, H., "Developmentof a New Dust and Slag Treatment Technology," SEAISI 2000 AustraliaConference, Proceedings V. I, S3, P6, Perth, Australia, May 2000.

42. Hino, M., and Miki, T., "New Role of Steelmaking Slags for theEnvironmental Protection of Ocean," Shiraishi Memorial Lecture of theIron Institute of Japan, Tokyo, Japan, 2001, pp. 44-45.

43. Sasamoto, H.; Tsubone, A.; Kamiya, Y.; and Sano, K., "Developmentof Fishing Block Using EAF Refining Slag," Journal of the Iron and SteelInstitute, V. 89, No.4, 2003, pp. 461-465.

44. Maslehuddin, M. et aI., "Comparison of Properties of Steel Slagand Crushed Limestone Aggregate Concretes," Construction and BuildingMaterials, V. 17,2003, pp. 105-112.

45. Beshr, H.; Almusallam, A. A.; and Maslehuddin, M., "Effect ofCoarse Aggregate Quality on the Mechanical Properties of High-StrengthConcrete," Construction and Building Materials, V. 17,2003, pp. 97-103.

46. Pellegrino, C., and Gaddo, V., "Mechanical and DurabilityCharacteristics of Concrete Containing EAF Slag as Aggregate," Cementand Concrete Composites, V. 31, No.9, Oct. 2009, pp. 663-671.

47. Khokhar, M. I. A. et aI., "Mix Design of Concrete with High Contentof Mineral Additions: Optimisation' to Improve Early Age Strength,"Cement and Concrete Composites, V. 32, 2010, pp. 377-385.

48. Manso, J. M.; Gonzalez, 1. J.; and Polanco, J. A., "Electric ArcFurnace Slag in Concrete," Journal of Materials in Civil Engineering,ASCE, V. 16, No.6, 2004, pp. 639-645.

49. Manso, J. M.; Losariez, M. M.; Polanco,J. A.; and Gonzalez, J. J., "LadleFurnace Slag in Construction," Journal of Materials in Civil Engineering,ASCE, V. 17, No.5, 2005, pp. 513-518.

50. Manso, J. M.; Polanco, J. A.; Losanez, M. M.; and Gonzalez, J. J.,"Durability of Concrete Made with EAF Slag as Aggregate," Cement andConcrete Composites, V. 28, 2006, pp. 528-534.

51. Polanco, J. A.; Manso, J. M.; Setien, J.; and Gonzalez, J., "Strengthand Durability of Concrete Made with Electric Steelmaking Slag," ACIMaterials Journal, V. 108, No.2, MaL-ApL 2011, pp. 196-203.

52. ASTM D4752-00(2006), "Standard Test Method for PotentialExpansion of Aggregates from Hydration Reactions," ASTM International,West Conshohocken, PA, 2006, 3 pp.

53. ASTM D29401D2940M-09, "Standard Specification for GradedAggregate Material For Bases or Subbases for Highways or Airports,"ASTM International, West Conshohocken, PA, 2009, 3 pp.

54. ASTM C33/C33M-lla, "Standard Specification for ConcreteAggregates," ASTM International, West Conshohocken, PA, 2011, 11 pp.

55. Wu, W.; Zhang, W.; and Ma, G., "Optimum Content of Copper Slagas a Fine Aggregate in High Strength Concrete," Materials & Design,V. 31,2010,pp. 2878-2883.

56. Aquino, C. et aI., "The Effects of Limestone Aggregate on ConcreteProperties," Construction and Building Materials, V. 24, 2010, p. 2363.

57. Setien, J.; Hernandez, D.; and Gonzalez, J. J., "Characterization ofLadle Furnace Basic Slag for Use as a Construction Material," Constructionand Building Materials, V. 23, No.5, 2009, pp. 1788-1794.. 58. ~Instruccion del Hormigon Estructural EHE.-- 08," Ministerio de.

Fomento, Gobierno de Espana. Secreta ria General Tecnica, Centro dePublicaciones, Madrid, Spain, 2008.

59. ASTM CI91-08, "Standard Test Methods for Time of Settingof Hydraulic Cement by Vicat Needle," ASTM International, WestConshohocken. PA, 2008,8 pp.

60. Hewlett, P. C, ed., Lea's Chemisuy of Cement and Concrete, fourthedition, Arnold Publishers, London, UK, 1998.

IN ACI STRUCTURAL JOURNALThe American Concrete Institute also publishes the ACIStructural Journal. This section presents brief synopses ofpapers appearing in the current issue.

108-S61-Reexamination of Dowel Behavior of Steel BarsEmbedded in Concreteby Yoshiki Tanaka and Jun Murakoshi

To identify the mechanisms of the bearing and failure of steel barsembedded in concrete subjected to transverse load, static loading testsusing 24 concrete blocks containing dowel bars, bolted plate-mounted bars,or welded studs were conducted. The behavior up to failure is examinedbased on the results obtained from the tests and analysis using the traditionalbeam on elastic foundation (BEF) analogy. This paper describes the post-yield behavior of dowel bars and welded studs involving the spalling ofconcrete under the bars and the plastic hinge of the bars. The elastic analogyprovides further interesting implications to illustrate the behavior of thebars in concrete, even beyond yielding.

108-S62-Hybrid Externally Bonded/Mechanically FastenedFiber-Reinforced Polymer for RC Beam Strengtheningby Usama Ebead

This study examines a newly developed technique for the flexuralstrengthening of reinforced concrete (RC) beams. This technique is acombination of the externally bonded (EB) and mechanically fastened (MF)fiber-reinforced polymer (FRP) systems. It features the use of nylon anchorsto be inserted inside the concrete prior to installing the fasteners. The hybridEBIMF-FRP-strengthened specimens showed higher load capacity andpost-cracking stiffness than those of the corresponding MF-FRP counter-parts. Extending the FRP strips for the entire beam span is necessary forachievin" the noticeable enhancement of the load capacity and stiffnesswith this\ybrid EBIMF-FRP system. For such a system, the failure of thestrengthened beams is associated with diagonal cracks at the locations offasteners near the FRP strip ends. These cracks are initiated due to fastenerrotation and bearing damage, resulting in a noticeable slip of the FRP stripswith respect to the soffit of the beams.

PDF versions of these papers are available for download atthe ACI Web site, www.concrete.org, for a nominal fee.

evidence, new design provisions for minimum shear reinforcement andmaximum nominal shear strength are proposed.

108-S65-Bond and Shear Behavior of Concrete BeamsContaining Lightweight Synthetic Particlesby Matthew J. Heiser, Amr Hosny, Sami H. Rizkalla, and Paul Zia

This paper summarizes a comprehensive experimental program thatinvestigated the bond and shear behavior of concrete beams containinglightweight synthetic particles (LSP). LSP is a new concrete additive that,when used, leads to reduced unit weight of concrete, enhances flowabilityof the fresh concrete for pumping purposes, and produces durable concretefor freezing and thawing and deicing exposed conditions. It also reduces thethermal conductivity (increases R-value), thus reducing the energy requiredfor heating and cooling. The use of these specially formulated particles, incombination with normalweight aggregates, could reduce the unit weight ofconcrete by 10 to 20%, ranging from 120 to 130 Ib/ft3 (1920 to 2080 kg/m3),depending on the amount of LSP used in the concrete mixture. The experi-mental program included 27 large-scale specimens. Research findings indicatethat the bond and shear behavior of beams with LSP additive is similar to thebehavior of beams made with normal weight concrete. Test results confirmthat ACI 318-08 can be used for the design of LSP concrete members forshear and the development length of steel reinforcement without the use ofthe reduction factor J.. required for lightweight concrete.

108-S66-Vibration Characteristics of Concrete-Steel CompositeFloor Structuresby Sandun De Silva and David P. Thambiratnam

This paper discusses the vibration characteristics of a concrete-steelcomposite multi-panel floor structure; the use of these structures is becomingmore common. These structures have many desirable properties but areprone to excessive and complex vibration, which is not currently well under-stood. Existing design codes and practice guides provide generic advice orsimple techniques that cannot address the complex vibration in these typesof low-frequency structures. The results of this study show the potential foran adverse dynamic response from higher and multi-modal excitationinfluenced by human-induced pattern loading, structural geometry, andactivity frequency. Higher harmonics of the load frequency are able to excitehigher modes in the composite floor structure in addition to its fundamentalmode. The analytical techniques used in this paper can supplement thecurrent limited code and practice guide provisions for mitigating the impactof human-ind~ced vibrations in these floor structures.

108-S63-Slab Construction Load Affected by Shore Stiffnessand Concrete Crackingby Hong-Gun Park, Hyeon-Jong Hwang, Geon-Ho Hong, Yong-Nam Kim, and Jae-Yo Kim

The evaluation of construction load is a critical issue in the design andconstruction of long-span flat plates, which are vulnerable to excessivedeflections and concrete cracking. This study focused on the effects of shorestiffness and concrete cracking on the distribution and magnitude of the slabconstruction load. Slabs connected by shores were idealized as a simplified

multi-story frame model, which was used to develop a simplified method for 108-S67-Compression Splices in High-Strength Concrete ofthe evaluation of construction load. In the proposed method, the effects of .10.0 .A/lPa (14:,~QO p~j) and Les~tvariouS design parameters, includiiigsfiore's'tiff~es's:coiicreie'ciacking:'arid by Sung-Chul Chun, Sung-Ho Lee, and Sohwan Oh

boundary conditions, were considered. The proposed method was applied In high-strength concrete, a compression lap splice may be calculatedto an actual multi-story building under construction. The predicted shore to be longer than a tension lap splice according to ACI 318-08. An experi-forces and construction loads were compared with the on-site measured mental study of 72 specimens was conducted on compressive lap splicesdata and predictions from existing methods. using concrete compressive strengths of 80 and 100 MPa (11,600 and

14,500 psi), and the effects of concrete strength, splice length, and trans-verse reinforcement were assessed. From the regression anal yses of 94 teststhat failed in splitting, including the data in the literature, two equationswere developed with .Ji]d" and l/db to predict the splice strength. Usinga 5% fractile coefficient, two design equations for the splice length werederived. The proposed equations provide shorter lengths than the splicelength in tension, as given by ACI 318-08. In addition, there is no signifi-cant difference between the lengths calculated by the two equations. There-

108-S64-Efficient Shear Reinforcement Design Limits forPrestressed Concrete Beamsby Alejandro R. Avendano and Oguzhan Sayrak

The appropriateness of the current design specifications for minimumshear reinforcement and maximum nominal shear strength for prestressedconcrete members is evaluated through the use of the University of Texas'Prestressed Concrete Shear Database (UTPCSDB). Based on experimental

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the tested ranges.

10S-S6S- Tension-Softening Properties for Concrete-ConcreteInterfacesby Santosh G. Shah, V. Bhasya, and J. M. Chandra Kishen

The tension-softening parameters for different concrete-concrete interfacesare determined using the bimaterial cracked hinge model. Beams of differentsizes having a jointed interface between two different strengths of concreteare tested under three-point bending (TPB). The load versus crack mouthopening displacement (CMOD) results are used to obtain the stress-crackopening relation through an inverse analysis. In addition, the fracture energy,tensile strength, and modulus of elasticity are also computed from the inverseanalysis. The fracture properties are used in the nonlinear fracture mechanicsanalysis of a concrete patch-repaired beam to determine its load-carryingcapacity when repaired with concrete of different strengths.

10S-S69-Fiber-Reinforced Polymer Bond Test in Presence ofSteel and Cracksby Mehdi Taher Khorramabadi and Chris J. Burgoyne

The understanding of failure modes of flexurally fiber-reinforcedpolymer (FRP)-strengthened reinforced concrete (RC) beams that initiateaway from the beam's end requires a realistic knowledge of the bondbehavior between the FRP and the concrete between cracks in the presenceof steel. The conventional method used to obtain a bond characteristic is topull a bonded FRP from a concrete block, which effectively simulates theconditions in the anchorage regions of a strengthened beam. The boundaryconditions in the anchorage regions differ significantly from those in theregions between the cracks, so a different model must be used. A new bondtest method is proposed and tests are carried out to mimic the conditionsin both the cracked and anchorage regions when steel is present. The testresults showed that not only do the bond models differ significantly in thecracked and anchorage regions, but also the steel and its bond stress affectthe bond behavior.

10S-S70-lnfluence of Axial Stress on Shear Response ofReinforced Concrete Elementsby Liping Xie, Evan C. Bentz, and Michael P. Collins

There is strong disagreement between different code provisions as to theinfluence of axial stress on shear strength. To examine this influence, sixnominally identical reinforced concrete elements representing web regionsof girders or walls were loaded under different ratios of longitudinal axialstress to shear stress. The results demonstrated that the application of thebasic ACI 318-08 shear approach can significantly overestimate both thebeneficial effect of compression on shear and the detrimental effect of tensionon shear strength. The ACI 318-08 simple expression for the benefits ofcompression gave excellent predictions, whereas the simple expression fortension was very conservative. The CSA A23.3-04 shear provisions basedon the modified compression field theory (MCFT) provided the best code-based estimates of the shear strength. The full MCFT provided not only thebest estimates of conditions at failure-including failure shear stresses andfailure crack angles for the full range of axial stresses-but also provided

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