Research ArticleFlexural and Shear Behaviors of ReinforcedAlkali-Activated Slag Concrete Beams

Kwang-Myong Lee1 Sung Choi1 Jinkyo F Choo2 Young-Cheol Choi3 and Sung-Won Yoo4

1Department of Civil and Environmental System Engineering Sungkyunkwan University 2066 Seobu-roJangan-gu Suwon 16419 Republic of Korea2Department of Energy Engineering Konkuk University 120 Neungdong-ro Gwangjin-gu Seoul 05029 Republic of Korea3Department of Architectural Engineering Gachon University 1342 Seongnamdaero Sujeong-gu Seongnam-siGyeonggi-do 13120 Republic of Korea4Department of Civil and Environmental Engineering Gachon University 1342 Seongnamdaero Sujeong-guSeongnam-si Gyeonggi-do 13120 Republic of Korea

Correspondence should be addressed to Sung-Won Yoo imyswgachonackr

Received 4 April 2017 Revised 24 May 2017 Accepted 11 June 2017 Published 20 July 2017

Academic Editor Tung-Chai Ling

Copyright copy 2017 Kwang-Myong Lee et al This is an open access article distributed under the Creative Commons AttributionLicense which permits unrestricted use distribution and reproduction in any medium provided the original work is properlycited

Thematerial properties of cement-zero concrete using alkali-activators have been studied extensively as the latest response to reducethe CO

2 exhaust of the cement industry However it is also critical to evaluate the behavior of reinforced concrete beams made ofalkali-activated slag (AAS) concrete in terms of flexure and shear to promote the applicability of AAS concrete as structuralmaterialAccordingly nine types of beam specimens with various ratios of tensile steel and stirrup were fabricated and subject to bendingand shear tests The results show that the flexural and shear behaviors of the reinforced AAS concrete members are practicallysimilar to those made of normal concrete and indicate the applicability of the conventional design code given that the lower densityof slag is considered In addition a framework using the elastic modulus and stress-strain relation from earlier research is adoptedto carry out nonlinear finite element analysis reflecting the material properties of AAS concreteThe numerical results exhibit goodagreement with the experimental results and demonstrate the validity of the analytical model

1 Introduction

Thecement and concrete industries count among the primaryproducers of CO2 and prediction forecasts that theworldwideconsumption of cement will continue to increase yearly by25 to 58 during the second and third decades of the21st century [1] As an attractive solution to prevent or atleast delay the global warming caused by the emission ofgreenhouse gases research was implemented worldwide tofabricate cement-zero concrete using slag powder fly ashand alkali-activators [2ndash4] Experimental works especiallyreported that concrete using alkali-activated slag (AAS)instead of blast-furnace slag could develop high early strengthhigher than 50MPa even at ambient temperature and resistchemical attack by sulfates [5 6]

To date studies focused essentially on the material prop-erties of cement-zero concrete using AAS like the strengthdrying shrinkage autogenous shrinkage and durability Forexample Oh et al [7] studied the autogenous shrinkage offresh AAS mortar according to the water-to-binder ratioto assess the effect of the rapid alkaline reaction occurringat early age caused by the introduction of large amount ofAAS Collins and Sanjayan [8] compared the workabilityand equivalent one-day strength of AAS concrete to thoseof Portland cement concrete at normal curing temperatureand reported discrepancies in the mechanical properties likethe compressive strength elastic modulus flexural strengthdrying shrinkage and creep Sofi et al [9] considered sixinorganic polymer concrete (IPC) mixes to evaluate theeffects of the inclusion of coarse aggregates and granulated

HindawiAdvances in Materials Science and EngineeringVolume 2017 Article ID 5294290 12 pageshttpsdoiorg10115520175294290

2 Advances in Materials Science and Engineering

blast furnace slag These authors carried out tests and foundout that in most cases the engineering properties developedby the IPC mixes compared favorably to those predictedby the relevant standards for concrete mixtures Atis et al[10] applied liquid sodium silicate sodium hydroxide andsodium carbonate (SC) at different sodium concentrationsto produce AAS concrete mixes and recommended using SCas activator for slag mortar since it could achieve adequatestrength and setting times and shrinkage comparable toPortland cement concrete Using such SC activator MeloNeto et al [11] examined the relationship between thehydration unrestrained drying and autogenous shrinkage ofAAS mortar specimens These authors reported the criticalinfluence of the amount of activator on the drying andautogenous shrinkages and the significant contribution ofthe autogenous shrinkage on the total shrinkage BesidesPuertas et al [12] analyzed the behavior of AAS mortars aftercarbonation The results indicated that AAS mortars weremore intensely and deeply carbonated than Portland cementmortars

These previous studies gave insight on the adequate mixto achieve AAS mortars exhibiting material properties com-parable to Portland cement mortars However research shallalso be implemented on the elastic modulus stress-strainrelations and behavior of structural members to exploit AASconcrete as structural material Recently Lee and Seo [13]and Choi et al [14] evaluated experimentally the flexuraland shear behaviors of AAS concrete beams but withoutattempting to model these behaviors at once and analytically

Accordingly this study investigates experimentally andanalytically the structural behavior of AAS concretemembersand intends to verify the applicability of existing cement-based concrete design code to AAS concrete To that goal thebehavior of reinforced concrete beamsmade of AAS concreteis evaluated experimentally in terms of both flexure and shearIn addition the elastic modulus and stress-strain relation ofAAS concrete for 50-MPa precast members obtained exper-imentally are used to perform the finite element analysis ofthe flexural members and shear members and the numericalresults are compared to the experimental data

2 Test Setup

21 Materials Ground granulated blast furnace slag(GGBFS) with density of 290 gcm3 fineness of 4365 cm2gand basicity of 178 is used as binder River sand with densityof 258 gcm3 and fineness modulus of 292 is used as fineaggregate Crushed stone with density of 262 gcm3 andmaximum size of 19mm is adopted as coarse aggregateTwo types of alkali-activators that are sodium hydroxide(98 purity) and industrial water glass with SiO2 = 288and Na2O = 93 are used to activate the GGBFS Thesetwo products are added to realize Na2O = 60 and alkalimodulus Ms (=SiO2Na2O) of 10 with respect to the mass ofslag Moreover polycarbonate superplasticizer is adopted tosecure the fluidity of AAS concrete

22 Characteristics of Concrete and Reinforcement Table 1arranges the mix proportions of AAS concrete purposed for

0

20

40

60

Com

pres

sive s

tres

s (M

Pa)

1000 2000 3000 4000 50000Strain (10minus6 mmmm)

Average test resultsThorenfeldt et al

Figure 1 Stress-strain relationship of considered AAS concrete incompression

50-MPa precast products and used for the fabrication of thebeam specimens In Table 1119882119861 stands for water-to-binderratio 119878119886 for fine-to-aggregate ratio and119882 for water Table 2lists the properties of fresh AAS concrete together with theelastic modulus and strength of AAS concrete at 28 days Thecompressive strength at 3 days is 32MPa and the compressivestrength and elastic modulus at 28 days are 553MPa and315 GPa respectively

Figure 1 plots the stress-strain relationship of AAS con-crete in compression The value of 0003 obtained for theultimate compressive strain of AAS concrete appears to besimilar to that of ordinary Portland cement (OPC) Thetest results are also compared with the values given by thefollowing analyticalmodel suggested byThorenfeldt et al [16]for OPC

119891c = 119891cm times120576c120576cmtimes 119899119899 minus 1 + (120576c120576cm)119899119896

(1)

where 119891c and 120576c are strength and strain of concrete respec-tively 119891cm is peak stress (MPa) 120576cm is strain at peak stressand 119899 = 08 + (119891cm17) with 119896 = 067 + (119891cm62) if 120576c gt 120576cmand 119896 = 1 if 120576c le 120576cm

Figure 1 shows good agreement of the stress-strain rela-tionship between the test results and themodel ofThorenfeldtet al [16] up to the ultimate strain However AAS concreteexhibits more ductile behavior than the analytical modelbeyond the ultimate strain

Besides the tensile reinforcement and stirrup are respec-tively made of steel SD500 and SD400 of which average yieldstrengths derived from direct tensile test are 4996MPa and4192MPa [13 14] Tests were performed on 120601100 times 200mmcylinders fabricated to examine the stress-strain relation andderive the elastic modulus of AAS concrete

23 Test Variables For the flexural test three levels of rein-forcement ratio (balanced steel ratio of 76 58 and 43) were

Advances in Materials Science and Engineering 3

Table 1 Mix proportions of AAS concrete

119882119861 () 119878119886 () Unit mass (kgm3)119882 GGBFS Fine aggregate Coarse aggregate Water glass NaOH Superplasticizer

45 50 165 367 855 869 73 19 367

Table 2 Properties of AAS concrete

Fresh concrete Hardened concrete (28 days)Slump (mm) Air content () Compressive strength (MPa) Elastic modulus (GPa) Splitting tensile strength (MPa)165 31 553 315 39

selected as test variables to examine the flexural behavior ofthe AAS concrete specimens for 50-MPa precast productsTherefore 3 types of beam specimens were fabricated Inthe specimens the stirrups (D10) are arranged densely withspacing of 70mm to prevent shear failure Moreover threelevels of tensile reinforcement ratio (balanced steel ratio of76 58 and 43) and 2 levels of stirrup spacing ((12)119889 nostirrup) were chosen as test variables of the beam specimensfor the shear test Here six types of beam specimens werefabricated for the shear tests

24 Details of Test Specimens Table 3 lists the beam speci-mens with their designation and corresponding test variablesfor the examination of the flexural and shear behaviorsFigure 2 shows the reinforcement details and dimensions ofthe beam specimens Table 3 gives the detailed dimensions ofthe specimens Figure 2(b) illustrates the layout of the sensorsfor the measurement of the steel and concrete strains and thecenter deflection during the loading test Figure 3 pictures acompleted beam specimen installed for loading test

3 Test Results and Discussion

31 Flexural Behavior of AAS Concrete Members Table 4 liststhe crack load steel yield load and ultimate load measuredin the AAS concrete members during the bending test Allthe specimens failed by flexure and the load bearing capacityincreased with larger tensile steel ratio The ratio of theultimate load to the steel yield load ranges between 115 and141 All the specimens exhibit similar crack load because themembers were fabricated using the same AAS concrete

Figure 4 plots the load-deflection curves of the flexuralmembers During the increase of the load all the specimensdevelop deflection quasi-proportional to the load Then theslope of the curves experiences steep variation after theyielding of the tensile steel The linear part of the curvesespecially becomes longer with higher tensile steel ratioFinally brittle failure occurs after the ultimate load with steeploss of the load This indicates that the behavior of the AASconcrete beams depends sensitively on the steel ratio similarlyto the beams made of normal concrete with OPC

Figure 5(a) plots the load-strain curves of the tensilesteel in the flexural members The strain remains minimalunder loading smaller than the crack load and increaseslinearly with larger load beyond the crack load Moreoverthe strain tends to enlarge significantly after yielding of the

tensile steel Figure 5(b) plots the load-compressive straincurves of concrete in the flexural members The strain 1205760 atmaximum stress ranges between 000250 and 000285 andthe ultimate strain ranges between 000250 and 000290 Theultimate strain is relatively smaller than the theoretical valueof 00038 but the peak strain 1205760 is comparable to that of theexperimental stress-strain curve

Figure 6 compares the ultimate moments of the flexuralmembers to those provided by the following equation Thisequation assumes the yielding of steel

119872u = 09119889 times 119860 s times 119891y (2)

where 119889 is effective depth of cross section119860 s is nominal areaof reinforced bar and 119891y is yield stress

Figure 6 shows good agreement between the experimen-tal and computed ultimate moments with the experimentalvalues larger by 3 to 9 than the predictions This verifiesthe similar flexural behavior developed by the AAS concretemembers and the OPC members

32 Shear Behavior of AAS Concrete Members Comparedto a previous paper presented by the authors of [14] threeadditional members were fabricated and tested to comple-ment erroneous data Table 5 arranges the flexural crackand shear crack loads the yield loads of the tensile steeland stirrup and the ultimate loads obtained from the shearfailure tests conducted at 28 days on the fabricated specimensAs shown in Figure 7 shear failure occurred in all themembers except specimen S19-05d The distinction betweenthe shear failure and the flexural failure was done consideringcomprehensively the yielding of the stirrups the eventualreaching of the ultimate strain by the flexural compressivestrain of concrete and the size of the shear strain of concrete

The loads generating flexural cracking were similar in thesix test members which is attributable to the use of concretewith the same compressive strength in all the specimensBesides the members reinforced with stirrups experiencedshear cracking at slightly larger load than the memberswithout stirrup Moreover the shear crack load appears to belarger with higher tensile steel ratio This can be explainedby the Dowel action of the tensile steel In other words theDowel action of the tensile steel delays the initiation of shearcracking as much as the tensile steel ratio is large For themembers with stirrups the yield loads of the tensile steelbecome larger with higher tensile steel ratio and the ratio of

4 Advances in Materials Science and Engineering

Table 3 Designation of beam specimen type and corresponding test variables

Designation Tensile steel (119860 s) Compression steel (1198601015840s) D10 stirrup spacing (mm) Tensile steel ratioFlexure

2-D16

F25 3-D2570

00304F22 3-D22 00232F19 3-D19 00172

ShearS25-05d 3-D25

12500304

S22-05d 3-D22 00232S19-05d 3-D19 00172S25-0 3-D25

000304

S22-0 3-D22 00232S19-0 3-D19 00172

200

(unit mm)

40 40120

5025

050

A998400

s

As

(a) Details of reinforcement

Steel strain gaugeLVDT

150mm

250mm

For flexural test L = 1350mmFor shear test L = 900mm

L

Concrete strain gauge

(b) Dimensions of specimens and sensor layout

Figure 2 Cross-sectional details and sensor layout of AAS concrete beam specimens

Figure 3 Setup for flexural test of AAS concrete beam specimen

the ultimate load to the yield load of the tensile steel rangesbetween 109 and 158

Figure 8 plots the load-deflection curves obtained fromthe shear test of the beam specimens All the curves are quasi-linear before early cracking and beyond that point increasenonlinearly until the ultimate state It appears that the tensilesteel ratio has significant influence on the structural behaviorof the beams The shear behavior of the AAS concrete beamspecimens is similar to that of the beams made of normalconcrete The specimens without stirrup especially failedas soon as the ultimate load was attained Note that thespecimens with stirrups experienced brittle failure practicallywithout ductile behavior due to the minimum arrangementof stirrups adopted in this studyThis means that when shearfailure occurs in absence of stirrup (specimens S25-0 and S22-0) the member shows common recovery of its resistance toshear owing to the Dowel action even after the first strengthdegradation However specimen S19-0 experienced flexural

Advances in Materials Science and Engineering 5

Table 4 Crack yield and ultimate loads and corresponding center displacement of flexural test specimens

Member Crack load (kN) Yield Ultimate UltimateYield Failure modeLoad (kN) Deflection (mm) Load (kN) Deflection (mm) Load ratio Deflection ratio

F25 206 2725 138 3134 181 115 131 FlexureF22 244 1719 108 2423 245 141 227 FlexureF19 224 1556 109 1884 233 121 214 Flexure

Table 5 Crack yield and ultimate loads of shear test specimens

Member Crack load (kN) Yield load of tensile steel 119886 (kN) Ultimate load 119887 (kN) 119887119886 Failure modeFlexure Shear

S25-05d 346 1632 2285 2496 109 ShearS22-05d 309 1522 1446 2283 158 ShearS19-05d 251 1340 1275 1765 138 FlexureS25-0 307 1259 mdash 853 mdash ShearS22-0 282 1186 mdash 1008 mdash ShearS19-0 329 1129 943 1112 118 Flexural shear

F25F22F19

0

50

100

150

200

250

Appl

ied

mom

ent (

kNmiddotm

)

5 10 15 20 25 300Deflection (mm)

Figure 4 Comparison of load-deflection curves of flexural testspecimens

shear failure instead of pure shear failure due to the Dowelaction of the tensile reinforcement This explains the absenceof strength recovery after the loss of early strength

Figure 9 draws the load-strain curves of the tensilesteel measured in the shear test specimens In view of theresults presented in Table 5 and Figure 9 specimens S25-0 S25-05d and S22-0 experienced pure shear failure beforeyielding of the tensile reinforcement Specimen S25-05das the one having the largest arrangement of tensile steelexhibits small increase of the strain in the tensile steelbecause the specimen reached the ultimate load following theoccurrence of shear failure immediately after yielding of thetensile reinforcement Specimens S25-0 and S22-0 withoutstirrup and small arrangement of tensile steel experienced

sudden failure before yielding of the tensile steel once the loadexceeded the shear strength due to the absence of stirrups

On the other hand the other specimens saw their tensilereinforcement deform at shear failure and without increaseof the load because shear failure occurred after yielding ofthe tensile reinforcement Specimens S22-05d and S19-05dwith relatively small arrangement of tensile reinforcementexperienced large deformation after yielding of the tensilesteel and finally failed respectively through flexureshear orflexure Despite the absence of stirrups specimen S19-0 failedthrough flexureshear due to the small amount of tensilesteel and developed relatively larger strain than the otherspecimens without stirrup

Figure 10 plots the load with respect to the flexuralcompressive strain of concrete measured in the shear testspecimens Specimen S25-05d with large amount of tensilesteel failed before concrete reached its ultimate strain dueto the sudden occurrence of shear failure Specimens S22-05d and S19-05d reinforced by stirrups and small amountof tensile steel were the only ones to develop relatively largeconcrete strain up to 00035 because of the following reasonsSpecimen S22-05d experienced flexural failure at first due toits small amount of tensile steel and finally failed throughshear due to its small amount of stirrup Specimen S19-05d experienced flexural failure without shear failure dueto its smaller amount of tensile steel In addition amongthe members without stirrup specimens S25-0 and S22-0developed small concrete strain due to the sudden occurrenceof shear failure

Figure 11(a) plots the load with respect to the shearstrain measured in the stirrups It appears that the stirrupyielded only in specimen S25-05d and not in the othertwo specimens This is in agreement with the failure modeslisted in Table 5 which indicated pure shear failure inspecimen S25-05 flexure-shear failure in specimen S22-05dand flexural failure in specimen S19-05d Besides specimensS22-05d and S19-05d that did not experience yielding oftheir stirrup recorded values of 000263 and 000262 for the

6 Advances in Materials Science and Engineering

F25F22F19

0

50

100

150

200

250

300

350Lo

ad (k

N)

001 002 0030Strain of tensile steel (mmmm)

(a) Load-strain curves of tensile steel

F25F22F19

0001 0002 0003 00040Strain of concrete (mmmm)

0

50

100

150

200

250

300

350

Load

(kN

)(b) Load-strain curves of concrete

Figure 5 Load-strain curves of flexural test specimens according to steel ratio

Equal line

100

150

200

250

Expe

rimen

tal v

alue

s (kN

middotm

)

150 200 250100Predicted values (kNmiddotm)

Figure 6 Comparison of experimental and predicted ultimatemoments

maximum strain of the stirrup respectively Accordingly thestress in the stirrup based upon the uniaxial stress-strainrelationship can be estimated to be 419MPa for S25-05d367MPa for S22-05d and 366MPa for S19-05d

Figure 11(b) plots the load with respect to the princi-pal strain measured in concrete The members underwentshear cracking at shear strain of 0000112 (specimen S19-0)0000113 (specimen S22-0) and 0000121 (specimen S25-0)The values of the concrete principal strain were calculatedby converting the strain measured by the strain gage rosette(Figure 2(b)) attached on the right-hand side of the criticalsection

ACI 318-08 [17] proposes the following formulae for thecalculation of the maximum shear stress Vcr of concrete

Simplified Formula

Vcr = 016radic119891ck (3)

Elaborated Formula

Vcr = 016radic119891ck + 176120588119881119889119872 le 029radic119891ck (4)

where119891ck is compressive strength of concrete 120588 is tensile steelratio 119881 is shear force at the critical section 119872 is bendingmoment at the critical section and 119889 is effective depth

If the compressive strength steel ratio shear force andbending moment are substituted in (3) Vcr = 119MPa andVcr takes values of 131MPa (S19-0) 137MPa (S22-0) and139MPa (S25-0) when (4) is used

Assuming the common value of 017 for Poissonrsquos ratio] the shear stress is calculated by multiplying the shearelastic modulus 119866 = 119864c[2(1 + ])] = 1406GPa by the shearstrain measured in the tests where the experimental elasticmodulus 119864c = 3291 GPa from Table 2 The correspondingshear stress becomes 158MPa (S19-0) 159MPa (S22-0)and 170MPa (S25-0) This shows that the principal stressobtained experimentally is slightly larger than that predictedby the design formulae in (3) and (4)

33 Comparison of Experimental Shear Strength and DesignValues Table 6 compares the shear strengths obtained fromthe test with those suggested by the design code In Table 6ldquoTestrdquo indicates the values based upon the loads measured inthe test and ldquoAnalysisrdquo designates the values computed fromthe strain measured in the test Recalling that specimen S19-05d failed through flexure S19-05d and S19-0 are discardedbecause the comparison of the shear strength is meaningless

Advances in Materials Science and Engineering 7

(a)

(b)

(c)

(d)

(e)

(f)

Figure 7 Crack pattern of shear test specimens (a) S25-05d (b) S22-05d (c) S19-05d (d) S25-0 (e) S22-0 and (f) S19-0

Table 6 Comparison of shear strengths from test and design code

Shear strength S25-05d S25-0 S22-05d S22-0Test (kN)119881c 853 853 1008 1008119881s 1643 mdash 1275 mdash119881u = 119881c + 119881s (incl self-weight) 2510 867 2296 1022

Design Code (kN)119881c 869 869 802 802119881s 1141 mdash 1141 mdash119881n = 119881c + 119881s 2010 869 1943 802

Test(119881u)Code(119881n) 125 100 118 127Analysis (kN)119881c 850 850 795 795119881s 1195 mdash 1047 mdash119881n = 119881c + 119881s (incl self-weight) 2059 864 1856 809

Test(119881u)Analysis(119881n) 122 100 124 126

8 Advances in Materials Science and Engineering

S25-05dS25-0S22-05d

S22-0S19-05dS19-0

0

100

200

300

400

500

600

Load

(kN

)

3 6 9 12 15 180Deflection (mm)

Figure 8 Load-deflection curves of shear test specimens

S25-05dS22-05dS19-05d

0007 0014 0021 0028 00350Strain of tensile steel (mmmm)

0

100

200

300

400

500

600

Load

(kN

)

(a) With stirrups

S25-0S22-0S19-0

0

50

100

150

200

250

Load

(kN

)

0001 0002 0003 00040Strain of tensile steel (mmmm)

(b) Without stirrup

Figure 9 Load versus strain of tensile steel in shear test specimens

for these members In addition the experimental shear forcecorresponds to the sum of the shear force obtained in thetest and the self-weight (135 kN = 25 times 03 times 02 times 182)the shear strength 119881c supported by concrete in the test is halfof the ultimate load of the specimens without stirrup (S25-0S22-0 S19-0) the shear strength 119881c provided by the designcode is the result of the application of (2) and the shearstrength sustained by the stirrups is calculated by applying119881s = 119860v119891y119889119904 where 119904 is the stirrup spacing The values of119881c in ldquoAnalysisrdquo are computed as the product of the principal

stress obtained in Figure 11(b) of Section 32 by the cross-sectional area of the specimen The values of 119881s in ldquoAnalysisrdquoare calculated as the product of the strain in the stirrupobtained in Figure 11(a) of Section 32 by the cross-sectionalarea of the reinforcement

The ratio of the experimental value to the value predictedby the design code (Test(119881u)Code(119881n)) ranges between100 and 127 and that of the experimental value to theanalytic value calculated from the experimental strain(Test(119881u)Analysis(119881n)) ranges between 100 and 126 which

Advances in Materials Science and Engineering 9

S25-05dS22-05dS19-05d

0

100

200

300

400

500

600Lo

ad (k

N)

0001 0002 0003 00040Strain of concrete (mmmm)

(a) With stirrups

S25-0S22-0S19-0

0

50

100

150

200

250

Load

(kN

)

00003 00006 00009 00012 000150Strain of concrete (mmmm)

(b) Without stirrup

Figure 10 Load versus flexural compressive strain of concrete in shear test specimens

S25-05dS22-05dS19-05d

0

100

200

300

400

500

600

Load

(kN

)

0003 0006 0009 0012 00150Shear strain (mmmm)

(a) Stirrups

S22-0S22-0S19-0

0

25

50

75

100

125

150

Load

(kN

)

000003 000006 000009 000012 0000150Shear strain (mmmm)

(b) Concrete

Figure 11 Load versus shear strain in shear test specimens

indicate that the analysis provides values larger by maximum26 and the similarity between the predictions of the designand the analysis

4 Finite Element Analysis

41 Method of Analysis The numerical analysis was carriedout using the nonlinear finite element program RCAHEST

developed by Kim et al [15] The analysis models consist ofa compression tension stiffening and shear transfer modelfor concrete and a model for embedded reinforcing steelThe concrete-reinforcement bond interaction is considered inboth the tension stiffening model for concrete and the modelfor reinforcement An earlier study [18] demonstrated that theabove-mentioned analysis model agreed reasonably with theexperimental data

10 Advances in Materials Science and Engineering

Uncracked

Isotropic Concrete

Reinforcingbar

Cracked

Orthotropic

Tensile

Specific stress-strain(i) Tension-stiffening model

(i) Bilinear model with bond

(ii) Shear transfer model(iii) Reduced compression model

Crackingcriteria

Compressive

model(i) Elastoplastic fracture

(i) Bare bar model

+

Equivalent stress-strain

effect

Figure 12 Outline of analysis model for reinforced high-strength concrete [15]

PredictionAnalysis

0

20

40

60

80

Stre

ss (M

Pa)

0001 0002 0003 0004 0005 00060Strain (mmmm)

Test

Figure 13 Comparison of experimental and predicted stress-straincurves

42 Material Models for Reinforced Concrete The nonlinearstress-strain relation of a reinforced concrete (RC) in-planeelement is formulated based on the concept of space averag-ing on the control volume The cracks and reinforcing barsare idealized as being distributed over the entire elementAlthough the local behavior of the crackedRC is not uniformin practical terms it can be treated as a continuum havingquasi-uniform stress and strain fields in a finite region Thematerial models aim to describe the overall behavior of astructure rather than a specific local behavior at the elementlevel In this paper the term ldquocrackrdquo explicitly refers to themacrocrack perpendicular to the principal tensile direction

According to the cracking criteria the analysis modelsare divided into models before and after the initiation ofcracks as shown in Figure 12Thematerialmodel for concreteprior to cracking is based on the elastoplastic fracture model[19] given in Figure 13 The local coordinate systems ofreinforcing bars are always assigned with respect to each baraxis but those of cracked concrete are determined according

F25-TestF25-AnalysisF22-Test

F22-AnalysisF19-TestF19-Analysis

0

50

100

150

200

250

300

350

Load

(kN

)

10 20 30 40 500Deflection (mm)

Figure 14 Comparison of experimental and analytical load-deflection curves for flexure test members

to the current major crack plane Once a smeared crack isinitiated it is treated as fixed in a direction and anisotropy isintroduced As loading step proceeds the principal directionof the average stress can be changed and the consequent sheartransfer model is involved in the constitutive law

5 Comparison of Experimental andAnalytical Results

51 Flexure Figure 14 compares the experimental and ana-lytical load-displacement curves for specimens F25 F22 andF19 The analytical results are in relatively good agreementwith the experimental values and indicate the validity of theanalytic model However for F25 with the largest tensile ratioconsidered in this study the test specimens exhibit slightbrittle failure compared to the analytical prediction The ini-tial slope of the experimental curves is on the whole smallerthan that of the analytical curves The different initial slopes

Advances in Materials Science and Engineering 11

S25-05d-TestS25-05d-AnalysisS22-05d-Test

S22-05d-AnalysisS19-05d-TestS19-05d-Analysis

0

100

200

300

400

500

600Lo

ad (k

N)

4 8 12 16 200Deflection (mm)

(a) With stirrups

0

100

200

300

400

Load

(kN

)

2 4 6 8 100Deflection (mm)

S25-05d-TestS25-05d-AnalysisS22-05d-Test

S22-05d-AnalysisS19-05d-TestS19-05d-Analysis

(b) Without stirrup

Figure 15 Comparison of experimental and analytical load-displacement curves for shear test members

of the analytical and experimental results can be attributedpartially to the stiffness adopted in the analytical model ofthe members and some experimental error Moreover theearly completion of the tests explains the different maximumdeflections of the analytical and experimental results In factlarger deflection would have been measured in the membersthat experienced failure through flexure but the tests wereinterrupted prematurely due to limitations in the capacity ofthe testing equipment and for the sake of safety

52 Shear Figure 15 compares the experimental and analyti-cal load-displacement curves of the shear test specimensTheanalytical results are in relatively good agreement with theexperimental values for the specimens with stirrups Herealso slight difference in the initial slope occurred as explainedabove in Section 51 Specimen S25-05d experienced suddenbrittle failure due to the clear occurrence of shear failureValues near the maximum load could not be measuredbecause of the delay in the acquisition of the data Besides thespecimenswithout stirrup showed smallermaximum loads inthe test than those of the analysis However considering thelarge experimental errors that are generally observed in theshear test of specimens without stirrup the results presentedhere demonstrate to some extent the good execution of thetests performed in this study

Here also the early ending of the tests explains thedifferent maximum deflections of the analytical and experi-mental results The members without stirrup in Figure 15(b)experienced sudden failure but the tests were interruptedprematurely due to limitations in the capacity of the testingequipment and for the sake of safety In addition it isextremely difficult to measure precisely the behavior of themembers without stirrup after the ultimate state when thefailure test is conducted using an actuator and through

displacement control On the other hand the similarity of theexperimental and analytical maximum deflections observedin Figure 15(a) was achieved because the members sufferedshear failure and reached a state close to their ultimate state atthe completion of the tests thanks to the presence of stirrups

6 Conclusions

This study evaluated experimentally and analytically thestructural behavior of reinforced concrete beams made ofAAS concrete The following conclusions can be drawn fromthe results

(1) The elastic modulus and the strain at maximum stressof AAS concrete were slightly smaller than thosepredicted for normal concrete This difference couldbe explained by the reduction in the unit mass ofAAS concrete caused by the smaller density of slagcompared to cement Further study shall proposeadequate models for the elastic modulus and stress-strain relation of AAS concrete

(2) The test results of the flexural members showedthat the ratio of the ultimate load to the yield loadof steel ranged between 115 and 141 and the loadbearing capacity improved with higher tensile steelratio The flexural behavior of the reinforced AASconcrete members appeared thus to be very similarto that of the reinforced concrete beam made ofnormal concrete because the reinforcing bars governthe flexural behavior of the members A nonlinearflexural analysis model was proposed using the elasticmodulus and stress-strain relation of AAS concreteThe analytical resultswere in good agreementwith the

12 Advances in Materials Science and Engineering

experimental results and demonstrated the validity ofthe analytical model

(3) The experimental shear strength obtained for themembers without stirrup was significantly higherthan that predicted by the design code which indi-cated the conservativeness of the design code Theshear behavior of the reinforced AAS concrete mem-bers varied according to the amount of tensile steel

(4) In view of the finite element analysis results reflectingthe nonlinearmodel ofAAS concrete used in previousstudies the flexural and shear behaviors of the AASconcrete specimenswere in relatively good agreementwith those predicted analytically

(5) Consequently the test results show that the flexuraland shear behaviors of the reinforced AAS concretemembers are very similar to those of the reinforcedconcrete beammade of normal concrete and render itpossible to apply conventional design code for flexureand shear in the design of reinforced AAS concretemembers Further studies are required for the practi-cal use of AAS concrete since this experimental studywas limited to specimens with specific dimensions

Conflicts of Interest

The authors declare that they have no conflicts of interest

Acknowledgments

This research was financially supported by the KoreanMinistry of Environment as ldquoPublic Technology ProgramBased on Environmental Policyrdquo (no 2016000700003) Thisresearch was also supported by a grant (Code 11-TechnologyInnovation-F04) from Construction Technology InnovationProgram (CTIP) funded by Ministry of Land and Transportof Korean government

References

[1] S-D Wang X-C Pu K L Scrivener and P L Pratt ldquoAlkali-activated slag cement and concrete a review of properties andproblemsrdquo Advances in Cement Research vol 7 no 27 pp 93ndash102 1995

[2] A Palomo MW Grutzeck andM T Blanco ldquoAlkali-activatedfly ashes a cement for the futurerdquo Cement and ConcreteResearch vol 29 no 8 pp 1323ndash1329 1999

[3] C Shi P V Krivenko and D Roy Alkali-activated cement andconcrete vol 376 Taylor amp Francis Abingdon UK 2006

[4] C Shi A F Jimenez and A Palomo ldquoNew cements for the21st century the pursuit of an alternative to Portland cementrdquoCement and Concrete Research vol 41 no 7 pp 750ndash763 2011

[5] A R Brough and A Atkinson ldquoSodium silicate-basedalkali-activated slag mortars part I Strength hydration andmicrostructurerdquo Cement and Concrete Research vol 32 no 6pp 865ndash879 2002

[6] S Aydin and B Baradan ldquoEffect of activator type and contenton properties of alkali-activated slag mortarsrdquo Composites PartB Engineering vol 57 pp 166ndash172 2014

[7] S H Oh S H Hong and K M Lee ldquoAutogenous shrinkageproperties of high strength alkali activated slag mortarrdquo Journalof the Korean Recycled Construction Resources Institute vol 2no 1 pp 60ndash65 2014

[8] F G Collins and J G Sanjayan ldquoWorkability and mechanicalproperties of alkali activated slag concreterdquo Cement and Con-crete Research vol 29 no 3 pp 455ndash458 1999

[9] M Sofi J S J van Deventer P A Mendis and G CLukey ldquoEngineering properties of inorganic polymer concretes(IPCs)rdquo Cement and Concrete Research vol 37 no 2 pp 251ndash257 2007

[10] C D Atis C Bilim O Celik and O Karahan ldquoInfluenceof activator on the strength and drying shrinkage of alkali-activated slag mortarrdquo Construction and Building Materials vol23 no 1 pp 548ndash555 2009

[11] A A Melo Neto M A Cincotto and W Repette ldquoDrying andautogenous shrinkage of pastes and mortars with activated slagcementrdquo Cement and Concrete Research vol 38 no 4 pp 565ndash574 2008

[12] F PuertasM Palacios andTVazquez ldquoCarbonation process ofalkali-activated slag mortarsrdquo Journal of Materials Science vol41 no 10 pp 3071ndash3082 2006

[13] K Lee and J Seo ldquoEvaluation of flexural behavior of reinforcedconcrete beams using alkali activated slag concreterdquo Journal ofthe Korea Concrete Institute vol 27 no 3 pp 311ndash317 2015

[14] S Choi K Lee and S Yoo ldquoShear behavior of RC beams usingalkali activated slag concreterdquo Journal of the Korean RecycledConstruction Resources Institute vol 3 no 1 pp 58ndash63 2015

[15] T-H Kim K-M Lee C Yoon and H M Shin ldquoInelasticbehavior and ductility capacity of reinforced concrete bridgepiers under earthquake I Theory and formulationrdquo Journal ofStructural Engineering vol 129 no 9 pp 1199ndash1207 2003

[16] E Thorenfeldt A Tomaszewicz and J J Jensen ldquoMechanicalproperties of high strength concrete and application in designrdquoin Proceedings of the Symposium Utilization of High StrengthConcrete T Trondheim Ed vol 40 pp 149ndash159 StravangerNorway 15ndash18 June 1987

[17] S-W Shin S K Ghosh and J Moreno ldquoFlexural ductility ofultra-high-strength concrete membersrdquoACI Structural Journalvol 86 no 4 pp 394ndash400 1989

[18] T-H Kim K-M Lee C Yoon and H M Shin ldquoInelasticbehavior and ductility capacity of reinforced concrete bridgepiers under earthquake II Numerical validationrdquo Journal ofStructural Engineering vol 129 no 9 pp 1208ndash1219 2003

[19] K Maekawa and H Okamura ldquoDeformational behavior andconstitutive equation of concrete using the elasto-plastic andfracture modelrdquo Journal of the Faculty of Engineering Universityof Tokyo Series B vol 37 no 2 pp 253ndash328 1983

Submit your manuscripts athttpswwwhindawicom

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CeramicsJournal of

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CompositesJournal of

NanoparticlesJournal of

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Biomaterials

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NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

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NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

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CrystallographyJournal of

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The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

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Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

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Advances in Materials Science and Engineering 3

Table 1 Mix proportions of AAS concrete

119882119861 () 119878119886 () Unit mass (kgm3)119882 GGBFS Fine aggregate Coarse aggregate Water glass NaOH Superplasticizer

45 50 165 367 855 869 73 19 367

Table 2 Properties of AAS concrete

Fresh concrete Hardened concrete (28 days)Slump (mm) Air content () Compressive strength (MPa) Elastic modulus (GPa) Splitting tensile strength (MPa)165 31 553 315 39

selected as test variables to examine the flexural behavior ofthe AAS concrete specimens for 50-MPa precast productsTherefore 3 types of beam specimens were fabricated Inthe specimens the stirrups (D10) are arranged densely withspacing of 70mm to prevent shear failure Moreover threelevels of tensile reinforcement ratio (balanced steel ratio of76 58 and 43) and 2 levels of stirrup spacing ((12)119889 nostirrup) were chosen as test variables of the beam specimensfor the shear test Here six types of beam specimens werefabricated for the shear tests

24 Details of Test Specimens Table 3 lists the beam speci-mens with their designation and corresponding test variablesfor the examination of the flexural and shear behaviorsFigure 2 shows the reinforcement details and dimensions ofthe beam specimens Table 3 gives the detailed dimensions ofthe specimens Figure 2(b) illustrates the layout of the sensorsfor the measurement of the steel and concrete strains and thecenter deflection during the loading test Figure 3 pictures acompleted beam specimen installed for loading test

3 Test Results and Discussion

31 Flexural Behavior of AAS Concrete Members Table 4 liststhe crack load steel yield load and ultimate load measuredin the AAS concrete members during the bending test Allthe specimens failed by flexure and the load bearing capacityincreased with larger tensile steel ratio The ratio of theultimate load to the steel yield load ranges between 115 and141 All the specimens exhibit similar crack load because themembers were fabricated using the same AAS concrete

Figure 4 plots the load-deflection curves of the flexuralmembers During the increase of the load all the specimensdevelop deflection quasi-proportional to the load Then theslope of the curves experiences steep variation after theyielding of the tensile steel The linear part of the curvesespecially becomes longer with higher tensile steel ratioFinally brittle failure occurs after the ultimate load with steeploss of the load This indicates that the behavior of the AASconcrete beams depends sensitively on the steel ratio similarlyto the beams made of normal concrete with OPC

Figure 5(a) plots the load-strain curves of the tensilesteel in the flexural members The strain remains minimalunder loading smaller than the crack load and increaseslinearly with larger load beyond the crack load Moreoverthe strain tends to enlarge significantly after yielding of the

tensile steel Figure 5(b) plots the load-compressive straincurves of concrete in the flexural members The strain 1205760 atmaximum stress ranges between 000250 and 000285 andthe ultimate strain ranges between 000250 and 000290 Theultimate strain is relatively smaller than the theoretical valueof 00038 but the peak strain 1205760 is comparable to that of theexperimental stress-strain curve

Figure 6 compares the ultimate moments of the flexuralmembers to those provided by the following equation Thisequation assumes the yielding of steel

119872u = 09119889 times 119860 s times 119891y (2)

where 119889 is effective depth of cross section119860 s is nominal areaof reinforced bar and 119891y is yield stress

Figure 6 shows good agreement between the experimen-tal and computed ultimate moments with the experimentalvalues larger by 3 to 9 than the predictions This verifiesthe similar flexural behavior developed by the AAS concretemembers and the OPC members

32 Shear Behavior of AAS Concrete Members Comparedto a previous paper presented by the authors of [14] threeadditional members were fabricated and tested to comple-ment erroneous data Table 5 arranges the flexural crackand shear crack loads the yield loads of the tensile steeland stirrup and the ultimate loads obtained from the shearfailure tests conducted at 28 days on the fabricated specimensAs shown in Figure 7 shear failure occurred in all themembers except specimen S19-05d The distinction betweenthe shear failure and the flexural failure was done consideringcomprehensively the yielding of the stirrups the eventualreaching of the ultimate strain by the flexural compressivestrain of concrete and the size of the shear strain of concrete

The loads generating flexural cracking were similar in thesix test members which is attributable to the use of concretewith the same compressive strength in all the specimensBesides the members reinforced with stirrups experiencedshear cracking at slightly larger load than the memberswithout stirrup Moreover the shear crack load appears to belarger with higher tensile steel ratio This can be explainedby the Dowel action of the tensile steel In other words theDowel action of the tensile steel delays the initiation of shearcracking as much as the tensile steel ratio is large For themembers with stirrups the yield loads of the tensile steelbecome larger with higher tensile steel ratio and the ratio of

4 Advances in Materials Science and Engineering

Table 3 Designation of beam specimen type and corresponding test variables

Designation Tensile steel (119860 s) Compression steel (1198601015840s) D10 stirrup spacing (mm) Tensile steel ratioFlexure

2-D16

F25 3-D2570

00304F22 3-D22 00232F19 3-D19 00172

ShearS25-05d 3-D25

12500304

S22-05d 3-D22 00232S19-05d 3-D19 00172S25-0 3-D25

000304

S22-0 3-D22 00232S19-0 3-D19 00172

200

(unit mm)

40 40120

5025

050

A998400

s

As

(a) Details of reinforcement

Steel strain gaugeLVDT

150mm

250mm

For flexural test L = 1350mmFor shear test L = 900mm

L

Concrete strain gauge

(b) Dimensions of specimens and sensor layout

Figure 2 Cross-sectional details and sensor layout of AAS concrete beam specimens

Figure 3 Setup for flexural test of AAS concrete beam specimen

the ultimate load to the yield load of the tensile steel rangesbetween 109 and 158

Figure 8 plots the load-deflection curves obtained fromthe shear test of the beam specimens All the curves are quasi-linear before early cracking and beyond that point increasenonlinearly until the ultimate state It appears that the tensilesteel ratio has significant influence on the structural behaviorof the beams The shear behavior of the AAS concrete beamspecimens is similar to that of the beams made of normalconcrete The specimens without stirrup especially failedas soon as the ultimate load was attained Note that thespecimens with stirrups experienced brittle failure practicallywithout ductile behavior due to the minimum arrangementof stirrups adopted in this studyThis means that when shearfailure occurs in absence of stirrup (specimens S25-0 and S22-0) the member shows common recovery of its resistance toshear owing to the Dowel action even after the first strengthdegradation However specimen S19-0 experienced flexural

Advances in Materials Science and Engineering 5

Table 4 Crack yield and ultimate loads and corresponding center displacement of flexural test specimens

Member Crack load (kN) Yield Ultimate UltimateYield Failure modeLoad (kN) Deflection (mm) Load (kN) Deflection (mm) Load ratio Deflection ratio

F25 206 2725 138 3134 181 115 131 FlexureF22 244 1719 108 2423 245 141 227 FlexureF19 224 1556 109 1884 233 121 214 Flexure

Table 5 Crack yield and ultimate loads of shear test specimens

Member Crack load (kN) Yield load of tensile steel 119886 (kN) Ultimate load 119887 (kN) 119887119886 Failure modeFlexure Shear

S25-05d 346 1632 2285 2496 109 ShearS22-05d 309 1522 1446 2283 158 ShearS19-05d 251 1340 1275 1765 138 FlexureS25-0 307 1259 mdash 853 mdash ShearS22-0 282 1186 mdash 1008 mdash ShearS19-0 329 1129 943 1112 118 Flexural shear

F25F22F19

0

50

100

150

200

250

Appl

ied

mom

ent (

kNmiddotm

)

5 10 15 20 25 300Deflection (mm)

Figure 4 Comparison of load-deflection curves of flexural testspecimens

shear failure instead of pure shear failure due to the Dowelaction of the tensile reinforcement This explains the absenceof strength recovery after the loss of early strength

Figure 9 draws the load-strain curves of the tensilesteel measured in the shear test specimens In view of theresults presented in Table 5 and Figure 9 specimens S25-0 S25-05d and S22-0 experienced pure shear failure beforeyielding of the tensile reinforcement Specimen S25-05das the one having the largest arrangement of tensile steelexhibits small increase of the strain in the tensile steelbecause the specimen reached the ultimate load following theoccurrence of shear failure immediately after yielding of thetensile reinforcement Specimens S25-0 and S22-0 withoutstirrup and small arrangement of tensile steel experienced

sudden failure before yielding of the tensile steel once the loadexceeded the shear strength due to the absence of stirrups

On the other hand the other specimens saw their tensilereinforcement deform at shear failure and without increaseof the load because shear failure occurred after yielding ofthe tensile reinforcement Specimens S22-05d and S19-05dwith relatively small arrangement of tensile reinforcementexperienced large deformation after yielding of the tensilesteel and finally failed respectively through flexureshear orflexure Despite the absence of stirrups specimen S19-0 failedthrough flexureshear due to the small amount of tensilesteel and developed relatively larger strain than the otherspecimens without stirrup

Figure 10 plots the load with respect to the flexuralcompressive strain of concrete measured in the shear testspecimens Specimen S25-05d with large amount of tensilesteel failed before concrete reached its ultimate strain dueto the sudden occurrence of shear failure Specimens S22-05d and S19-05d reinforced by stirrups and small amountof tensile steel were the only ones to develop relatively largeconcrete strain up to 00035 because of the following reasonsSpecimen S22-05d experienced flexural failure at first due toits small amount of tensile steel and finally failed throughshear due to its small amount of stirrup Specimen S19-05d experienced flexural failure without shear failure dueto its smaller amount of tensile steel In addition amongthe members without stirrup specimens S25-0 and S22-0developed small concrete strain due to the sudden occurrenceof shear failure

Figure 11(a) plots the load with respect to the shearstrain measured in the stirrups It appears that the stirrupyielded only in specimen S25-05d and not in the othertwo specimens This is in agreement with the failure modeslisted in Table 5 which indicated pure shear failure inspecimen S25-05 flexure-shear failure in specimen S22-05dand flexural failure in specimen S19-05d Besides specimensS22-05d and S19-05d that did not experience yielding oftheir stirrup recorded values of 000263 and 000262 for the

6 Advances in Materials Science and Engineering

F25F22F19

0

50

100

150

200

250

300

350Lo

ad (k

N)

001 002 0030Strain of tensile steel (mmmm)

(a) Load-strain curves of tensile steel

F25F22F19

0001 0002 0003 00040Strain of concrete (mmmm)

0

50

100

150

200

250

300

350

Load

(kN

)(b) Load-strain curves of concrete

Figure 5 Load-strain curves of flexural test specimens according to steel ratio

Equal line

100

150

200

250

Expe

rimen

tal v

alue

s (kN

middotm

)

150 200 250100Predicted values (kNmiddotm)

Figure 6 Comparison of experimental and predicted ultimatemoments

maximum strain of the stirrup respectively Accordingly thestress in the stirrup based upon the uniaxial stress-strainrelationship can be estimated to be 419MPa for S25-05d367MPa for S22-05d and 366MPa for S19-05d

Figure 11(b) plots the load with respect to the princi-pal strain measured in concrete The members underwentshear cracking at shear strain of 0000112 (specimen S19-0)0000113 (specimen S22-0) and 0000121 (specimen S25-0)The values of the concrete principal strain were calculatedby converting the strain measured by the strain gage rosette(Figure 2(b)) attached on the right-hand side of the criticalsection

ACI 318-08 [17] proposes the following formulae for thecalculation of the maximum shear stress Vcr of concrete

Simplified Formula

Vcr = 016radic119891ck (3)

Elaborated Formula

Vcr = 016radic119891ck + 176120588119881119889119872 le 029radic119891ck (4)

where119891ck is compressive strength of concrete 120588 is tensile steelratio 119881 is shear force at the critical section 119872 is bendingmoment at the critical section and 119889 is effective depth

If the compressive strength steel ratio shear force andbending moment are substituted in (3) Vcr = 119MPa andVcr takes values of 131MPa (S19-0) 137MPa (S22-0) and139MPa (S25-0) when (4) is used

Assuming the common value of 017 for Poissonrsquos ratio] the shear stress is calculated by multiplying the shearelastic modulus 119866 = 119864c[2(1 + ])] = 1406GPa by the shearstrain measured in the tests where the experimental elasticmodulus 119864c = 3291 GPa from Table 2 The correspondingshear stress becomes 158MPa (S19-0) 159MPa (S22-0)and 170MPa (S25-0) This shows that the principal stressobtained experimentally is slightly larger than that predictedby the design formulae in (3) and (4)

33 Comparison of Experimental Shear Strength and DesignValues Table 6 compares the shear strengths obtained fromthe test with those suggested by the design code In Table 6ldquoTestrdquo indicates the values based upon the loads measured inthe test and ldquoAnalysisrdquo designates the values computed fromthe strain measured in the test Recalling that specimen S19-05d failed through flexure S19-05d and S19-0 are discardedbecause the comparison of the shear strength is meaningless

Advances in Materials Science and Engineering 7

(a)

(b)

(c)

(d)

(e)

(f)

Figure 7 Crack pattern of shear test specimens (a) S25-05d (b) S22-05d (c) S19-05d (d) S25-0 (e) S22-0 and (f) S19-0

Table 6 Comparison of shear strengths from test and design code

Shear strength S25-05d S25-0 S22-05d S22-0Test (kN)119881c 853 853 1008 1008119881s 1643 mdash 1275 mdash119881u = 119881c + 119881s (incl self-weight) 2510 867 2296 1022

Design Code (kN)119881c 869 869 802 802119881s 1141 mdash 1141 mdash119881n = 119881c + 119881s 2010 869 1943 802

Test(119881u)Code(119881n) 125 100 118 127Analysis (kN)119881c 850 850 795 795119881s 1195 mdash 1047 mdash119881n = 119881c + 119881s (incl self-weight) 2059 864 1856 809

Test(119881u)Analysis(119881n) 122 100 124 126

8 Advances in Materials Science and Engineering

S25-05dS25-0S22-05d

S22-0S19-05dS19-0

0

100

200

300

400

500

600

Load

(kN

)

3 6 9 12 15 180Deflection (mm)

Figure 8 Load-deflection curves of shear test specimens

S25-05dS22-05dS19-05d

0007 0014 0021 0028 00350Strain of tensile steel (mmmm)

0

100

200

300

400

500

600

Load

(kN

)

(a) With stirrups

S25-0S22-0S19-0

0

50

100

150

200

250

Load

(kN

)

0001 0002 0003 00040Strain of tensile steel (mmmm)

(b) Without stirrup

Figure 9 Load versus strain of tensile steel in shear test specimens

for these members In addition the experimental shear forcecorresponds to the sum of the shear force obtained in thetest and the self-weight (135 kN = 25 times 03 times 02 times 182)the shear strength 119881c supported by concrete in the test is halfof the ultimate load of the specimens without stirrup (S25-0S22-0 S19-0) the shear strength 119881c provided by the designcode is the result of the application of (2) and the shearstrength sustained by the stirrups is calculated by applying119881s = 119860v119891y119889119904 where 119904 is the stirrup spacing The values of119881c in ldquoAnalysisrdquo are computed as the product of the principal

stress obtained in Figure 11(b) of Section 32 by the cross-sectional area of the specimen The values of 119881s in ldquoAnalysisrdquoare calculated as the product of the strain in the stirrupobtained in Figure 11(a) of Section 32 by the cross-sectionalarea of the reinforcement

The ratio of the experimental value to the value predictedby the design code (Test(119881u)Code(119881n)) ranges between100 and 127 and that of the experimental value to theanalytic value calculated from the experimental strain(Test(119881u)Analysis(119881n)) ranges between 100 and 126 which

Advances in Materials Science and Engineering 9

S25-05dS22-05dS19-05d

0

100

200

300

400

500

600Lo

ad (k

N)

0001 0002 0003 00040Strain of concrete (mmmm)

(a) With stirrups

S25-0S22-0S19-0

0

50

100

150

200

250

Load

(kN

)

00003 00006 00009 00012 000150Strain of concrete (mmmm)

(b) Without stirrup

Figure 10 Load versus flexural compressive strain of concrete in shear test specimens

S25-05dS22-05dS19-05d

0

100

200

300

400

500

600

Load

(kN

)

0003 0006 0009 0012 00150Shear strain (mmmm)

(a) Stirrups

S22-0S22-0S19-0

0

25

50

75

100

125

150

Load

(kN

)

000003 000006 000009 000012 0000150Shear strain (mmmm)

(b) Concrete

Figure 11 Load versus shear strain in shear test specimens

indicate that the analysis provides values larger by maximum26 and the similarity between the predictions of the designand the analysis

4 Finite Element Analysis

41 Method of Analysis The numerical analysis was carriedout using the nonlinear finite element program RCAHEST

developed by Kim et al [15] The analysis models consist ofa compression tension stiffening and shear transfer modelfor concrete and a model for embedded reinforcing steelThe concrete-reinforcement bond interaction is considered inboth the tension stiffening model for concrete and the modelfor reinforcement An earlier study [18] demonstrated that theabove-mentioned analysis model agreed reasonably with theexperimental data

10 Advances in Materials Science and Engineering

Uncracked

Isotropic Concrete

Reinforcingbar

Cracked

Orthotropic

Tensile

Specific stress-strain(i) Tension-stiffening model

(i) Bilinear model with bond

(ii) Shear transfer model(iii) Reduced compression model

Crackingcriteria

Compressive

model(i) Elastoplastic fracture

(i) Bare bar model

+

Equivalent stress-strain

effect

Figure 12 Outline of analysis model for reinforced high-strength concrete [15]

PredictionAnalysis

0

20

40

60

80

Stre

ss (M

Pa)

0001 0002 0003 0004 0005 00060Strain (mmmm)

Test

Figure 13 Comparison of experimental and predicted stress-straincurves

42 Material Models for Reinforced Concrete The nonlinearstress-strain relation of a reinforced concrete (RC) in-planeelement is formulated based on the concept of space averag-ing on the control volume The cracks and reinforcing barsare idealized as being distributed over the entire elementAlthough the local behavior of the crackedRC is not uniformin practical terms it can be treated as a continuum havingquasi-uniform stress and strain fields in a finite region Thematerial models aim to describe the overall behavior of astructure rather than a specific local behavior at the elementlevel In this paper the term ldquocrackrdquo explicitly refers to themacrocrack perpendicular to the principal tensile direction

According to the cracking criteria the analysis modelsare divided into models before and after the initiation ofcracks as shown in Figure 12Thematerialmodel for concreteprior to cracking is based on the elastoplastic fracture model[19] given in Figure 13 The local coordinate systems ofreinforcing bars are always assigned with respect to each baraxis but those of cracked concrete are determined according

F25-TestF25-AnalysisF22-Test

F22-AnalysisF19-TestF19-Analysis

0

50

100

150

200

250

300

350

Load

(kN

)

10 20 30 40 500Deflection (mm)

Figure 14 Comparison of experimental and analytical load-deflection curves for flexure test members

to the current major crack plane Once a smeared crack isinitiated it is treated as fixed in a direction and anisotropy isintroduced As loading step proceeds the principal directionof the average stress can be changed and the consequent sheartransfer model is involved in the constitutive law

5 Comparison of Experimental andAnalytical Results

51 Flexure Figure 14 compares the experimental and ana-lytical load-displacement curves for specimens F25 F22 andF19 The analytical results are in relatively good agreementwith the experimental values and indicate the validity of theanalytic model However for F25 with the largest tensile ratioconsidered in this study the test specimens exhibit slightbrittle failure compared to the analytical prediction The ini-tial slope of the experimental curves is on the whole smallerthan that of the analytical curves The different initial slopes

Advances in Materials Science and Engineering 11

S25-05d-TestS25-05d-AnalysisS22-05d-Test

S22-05d-AnalysisS19-05d-TestS19-05d-Analysis

0

100

200

300

400

500

600Lo

ad (k

N)

4 8 12 16 200Deflection (mm)

(a) With stirrups

0

100

200

300

400

Load

(kN

)

2 4 6 8 100Deflection (mm)

S25-05d-TestS25-05d-AnalysisS22-05d-Test

S22-05d-AnalysisS19-05d-TestS19-05d-Analysis

(b) Without stirrup

Figure 15 Comparison of experimental and analytical load-displacement curves for shear test members

of the analytical and experimental results can be attributedpartially to the stiffness adopted in the analytical model ofthe members and some experimental error Moreover theearly completion of the tests explains the different maximumdeflections of the analytical and experimental results In factlarger deflection would have been measured in the membersthat experienced failure through flexure but the tests wereinterrupted prematurely due to limitations in the capacity ofthe testing equipment and for the sake of safety

52 Shear Figure 15 compares the experimental and analyti-cal load-displacement curves of the shear test specimensTheanalytical results are in relatively good agreement with theexperimental values for the specimens with stirrups Herealso slight difference in the initial slope occurred as explainedabove in Section 51 Specimen S25-05d experienced suddenbrittle failure due to the clear occurrence of shear failureValues near the maximum load could not be measuredbecause of the delay in the acquisition of the data Besides thespecimenswithout stirrup showed smallermaximum loads inthe test than those of the analysis However considering thelarge experimental errors that are generally observed in theshear test of specimens without stirrup the results presentedhere demonstrate to some extent the good execution of thetests performed in this study

Here also the early ending of the tests explains thedifferent maximum deflections of the analytical and experi-mental results The members without stirrup in Figure 15(b)experienced sudden failure but the tests were interruptedprematurely due to limitations in the capacity of the testingequipment and for the sake of safety In addition it isextremely difficult to measure precisely the behavior of themembers without stirrup after the ultimate state when thefailure test is conducted using an actuator and through

displacement control On the other hand the similarity of theexperimental and analytical maximum deflections observedin Figure 15(a) was achieved because the members sufferedshear failure and reached a state close to their ultimate state atthe completion of the tests thanks to the presence of stirrups

6 Conclusions

This study evaluated experimentally and analytically thestructural behavior of reinforced concrete beams made ofAAS concrete The following conclusions can be drawn fromthe results

(1) The elastic modulus and the strain at maximum stressof AAS concrete were slightly smaller than thosepredicted for normal concrete This difference couldbe explained by the reduction in the unit mass ofAAS concrete caused by the smaller density of slagcompared to cement Further study shall proposeadequate models for the elastic modulus and stress-strain relation of AAS concrete

(2) The test results of the flexural members showedthat the ratio of the ultimate load to the yield loadof steel ranged between 115 and 141 and the loadbearing capacity improved with higher tensile steelratio The flexural behavior of the reinforced AASconcrete members appeared thus to be very similarto that of the reinforced concrete beam made ofnormal concrete because the reinforcing bars governthe flexural behavior of the members A nonlinearflexural analysis model was proposed using the elasticmodulus and stress-strain relation of AAS concreteThe analytical resultswere in good agreementwith the

12 Advances in Materials Science and Engineering

experimental results and demonstrated the validity ofthe analytical model

(3) The experimental shear strength obtained for themembers without stirrup was significantly higherthan that predicted by the design code which indi-cated the conservativeness of the design code Theshear behavior of the reinforced AAS concrete mem-bers varied according to the amount of tensile steel

(4) In view of the finite element analysis results reflectingthe nonlinearmodel ofAAS concrete used in previousstudies the flexural and shear behaviors of the AASconcrete specimenswere in relatively good agreementwith those predicted analytically

(5) Consequently the test results show that the flexuraland shear behaviors of the reinforced AAS concretemembers are very similar to those of the reinforcedconcrete beammade of normal concrete and render itpossible to apply conventional design code for flexureand shear in the design of reinforced AAS concretemembers Further studies are required for the practi-cal use of AAS concrete since this experimental studywas limited to specimens with specific dimensions

Conflicts of Interest

The authors declare that they have no conflicts of interest

Acknowledgments

This research was financially supported by the KoreanMinistry of Environment as ldquoPublic Technology ProgramBased on Environmental Policyrdquo (no 2016000700003) Thisresearch was also supported by a grant (Code 11-TechnologyInnovation-F04) from Construction Technology InnovationProgram (CTIP) funded by Ministry of Land and Transportof Korean government

References

[1] S-D Wang X-C Pu K L Scrivener and P L Pratt ldquoAlkali-activated slag cement and concrete a review of properties andproblemsrdquo Advances in Cement Research vol 7 no 27 pp 93ndash102 1995

[2] A Palomo MW Grutzeck andM T Blanco ldquoAlkali-activatedfly ashes a cement for the futurerdquo Cement and ConcreteResearch vol 29 no 8 pp 1323ndash1329 1999

[3] C Shi P V Krivenko and D Roy Alkali-activated cement andconcrete vol 376 Taylor amp Francis Abingdon UK 2006

[4] C Shi A F Jimenez and A Palomo ldquoNew cements for the21st century the pursuit of an alternative to Portland cementrdquoCement and Concrete Research vol 41 no 7 pp 750ndash763 2011

[5] A R Brough and A Atkinson ldquoSodium silicate-basedalkali-activated slag mortars part I Strength hydration andmicrostructurerdquo Cement and Concrete Research vol 32 no 6pp 865ndash879 2002

[6] S Aydin and B Baradan ldquoEffect of activator type and contenton properties of alkali-activated slag mortarsrdquo Composites PartB Engineering vol 57 pp 166ndash172 2014

[7] S H Oh S H Hong and K M Lee ldquoAutogenous shrinkageproperties of high strength alkali activated slag mortarrdquo Journalof the Korean Recycled Construction Resources Institute vol 2no 1 pp 60ndash65 2014

[8] F G Collins and J G Sanjayan ldquoWorkability and mechanicalproperties of alkali activated slag concreterdquo Cement and Con-crete Research vol 29 no 3 pp 455ndash458 1999

[9] M Sofi J S J van Deventer P A Mendis and G CLukey ldquoEngineering properties of inorganic polymer concretes(IPCs)rdquo Cement and Concrete Research vol 37 no 2 pp 251ndash257 2007

[10] C D Atis C Bilim O Celik and O Karahan ldquoInfluenceof activator on the strength and drying shrinkage of alkali-activated slag mortarrdquo Construction and Building Materials vol23 no 1 pp 548ndash555 2009

[11] A A Melo Neto M A Cincotto and W Repette ldquoDrying andautogenous shrinkage of pastes and mortars with activated slagcementrdquo Cement and Concrete Research vol 38 no 4 pp 565ndash574 2008

[12] F PuertasM Palacios andTVazquez ldquoCarbonation process ofalkali-activated slag mortarsrdquo Journal of Materials Science vol41 no 10 pp 3071ndash3082 2006

[13] K Lee and J Seo ldquoEvaluation of flexural behavior of reinforcedconcrete beams using alkali activated slag concreterdquo Journal ofthe Korea Concrete Institute vol 27 no 3 pp 311ndash317 2015

[14] S Choi K Lee and S Yoo ldquoShear behavior of RC beams usingalkali activated slag concreterdquo Journal of the Korean RecycledConstruction Resources Institute vol 3 no 1 pp 58ndash63 2015

[15] T-H Kim K-M Lee C Yoon and H M Shin ldquoInelasticbehavior and ductility capacity of reinforced concrete bridgepiers under earthquake I Theory and formulationrdquo Journal ofStructural Engineering vol 129 no 9 pp 1199ndash1207 2003

[16] E Thorenfeldt A Tomaszewicz and J J Jensen ldquoMechanicalproperties of high strength concrete and application in designrdquoin Proceedings of the Symposium Utilization of High StrengthConcrete T Trondheim Ed vol 40 pp 149ndash159 StravangerNorway 15ndash18 June 1987

[17] S-W Shin S K Ghosh and J Moreno ldquoFlexural ductility ofultra-high-strength concrete membersrdquoACI Structural Journalvol 86 no 4 pp 394ndash400 1989

[18] T-H Kim K-M Lee C Yoon and H M Shin ldquoInelasticbehavior and ductility capacity of reinforced concrete bridgepiers under earthquake II Numerical validationrdquo Journal ofStructural Engineering vol 129 no 9 pp 1208ndash1219 2003

[19] K Maekawa and H Okamura ldquoDeformational behavior andconstitutive equation of concrete using the elasto-plastic andfracture modelrdquo Journal of the Faculty of Engineering Universityof Tokyo Series B vol 37 no 2 pp 253ndash328 1983

Submit your manuscripts athttpswwwhindawicom

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Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research

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Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MetallurgyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

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Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

4 Advances in Materials Science and Engineering

Table 3 Designation of beam specimen type and corresponding test variables

Designation Tensile steel (119860 s) Compression steel (1198601015840s) D10 stirrup spacing (mm) Tensile steel ratioFlexure

2-D16

F25 3-D2570

00304F22 3-D22 00232F19 3-D19 00172

ShearS25-05d 3-D25

12500304

S22-05d 3-D22 00232S19-05d 3-D19 00172S25-0 3-D25

000304

S22-0 3-D22 00232S19-0 3-D19 00172

200

(unit mm)

40 40120

5025

050

A998400

s

As

(a) Details of reinforcement

Steel strain gaugeLVDT

150mm

250mm

For flexural test L = 1350mmFor shear test L = 900mm

L

Concrete strain gauge

(b) Dimensions of specimens and sensor layout

Figure 2 Cross-sectional details and sensor layout of AAS concrete beam specimens

Figure 3 Setup for flexural test of AAS concrete beam specimen

the ultimate load to the yield load of the tensile steel rangesbetween 109 and 158

Figure 8 plots the load-deflection curves obtained fromthe shear test of the beam specimens All the curves are quasi-linear before early cracking and beyond that point increasenonlinearly until the ultimate state It appears that the tensilesteel ratio has significant influence on the structural behaviorof the beams The shear behavior of the AAS concrete beamspecimens is similar to that of the beams made of normalconcrete The specimens without stirrup especially failedas soon as the ultimate load was attained Note that thespecimens with stirrups experienced brittle failure practicallywithout ductile behavior due to the minimum arrangementof stirrups adopted in this studyThis means that when shearfailure occurs in absence of stirrup (specimens S25-0 and S22-0) the member shows common recovery of its resistance toshear owing to the Dowel action even after the first strengthdegradation However specimen S19-0 experienced flexural

Advances in Materials Science and Engineering 5

Table 4 Crack yield and ultimate loads and corresponding center displacement of flexural test specimens

Member Crack load (kN) Yield Ultimate UltimateYield Failure modeLoad (kN) Deflection (mm) Load (kN) Deflection (mm) Load ratio Deflection ratio

F25 206 2725 138 3134 181 115 131 FlexureF22 244 1719 108 2423 245 141 227 FlexureF19 224 1556 109 1884 233 121 214 Flexure

Table 5 Crack yield and ultimate loads of shear test specimens

Member Crack load (kN) Yield load of tensile steel 119886 (kN) Ultimate load 119887 (kN) 119887119886 Failure modeFlexure Shear

S25-05d 346 1632 2285 2496 109 ShearS22-05d 309 1522 1446 2283 158 ShearS19-05d 251 1340 1275 1765 138 FlexureS25-0 307 1259 mdash 853 mdash ShearS22-0 282 1186 mdash 1008 mdash ShearS19-0 329 1129 943 1112 118 Flexural shear

F25F22F19

0

50

100

150

200

250

Appl

ied

mom

ent (

kNmiddotm

)

5 10 15 20 25 300Deflection (mm)

Figure 4 Comparison of load-deflection curves of flexural testspecimens

shear failure instead of pure shear failure due to the Dowelaction of the tensile reinforcement This explains the absenceof strength recovery after the loss of early strength

Figure 9 draws the load-strain curves of the tensilesteel measured in the shear test specimens In view of theresults presented in Table 5 and Figure 9 specimens S25-0 S25-05d and S22-0 experienced pure shear failure beforeyielding of the tensile reinforcement Specimen S25-05das the one having the largest arrangement of tensile steelexhibits small increase of the strain in the tensile steelbecause the specimen reached the ultimate load following theoccurrence of shear failure immediately after yielding of thetensile reinforcement Specimens S25-0 and S22-0 withoutstirrup and small arrangement of tensile steel experienced

sudden failure before yielding of the tensile steel once the loadexceeded the shear strength due to the absence of stirrups

On the other hand the other specimens saw their tensilereinforcement deform at shear failure and without increaseof the load because shear failure occurred after yielding ofthe tensile reinforcement Specimens S22-05d and S19-05dwith relatively small arrangement of tensile reinforcementexperienced large deformation after yielding of the tensilesteel and finally failed respectively through flexureshear orflexure Despite the absence of stirrups specimen S19-0 failedthrough flexureshear due to the small amount of tensilesteel and developed relatively larger strain than the otherspecimens without stirrup

Figure 10 plots the load with respect to the flexuralcompressive strain of concrete measured in the shear testspecimens Specimen S25-05d with large amount of tensilesteel failed before concrete reached its ultimate strain dueto the sudden occurrence of shear failure Specimens S22-05d and S19-05d reinforced by stirrups and small amountof tensile steel were the only ones to develop relatively largeconcrete strain up to 00035 because of the following reasonsSpecimen S22-05d experienced flexural failure at first due toits small amount of tensile steel and finally failed throughshear due to its small amount of stirrup Specimen S19-05d experienced flexural failure without shear failure dueto its smaller amount of tensile steel In addition amongthe members without stirrup specimens S25-0 and S22-0developed small concrete strain due to the sudden occurrenceof shear failure

Figure 11(a) plots the load with respect to the shearstrain measured in the stirrups It appears that the stirrupyielded only in specimen S25-05d and not in the othertwo specimens This is in agreement with the failure modeslisted in Table 5 which indicated pure shear failure inspecimen S25-05 flexure-shear failure in specimen S22-05dand flexural failure in specimen S19-05d Besides specimensS22-05d and S19-05d that did not experience yielding oftheir stirrup recorded values of 000263 and 000262 for the

6 Advances in Materials Science and Engineering

F25F22F19

0

50

100

150

200

250

300

350Lo

ad (k

N)

001 002 0030Strain of tensile steel (mmmm)

(a) Load-strain curves of tensile steel

F25F22F19

0001 0002 0003 00040Strain of concrete (mmmm)

0

50

100

150

200

250

300

350

Load

(kN

)(b) Load-strain curves of concrete

Figure 5 Load-strain curves of flexural test specimens according to steel ratio

Equal line

100

150

200

250

Expe

rimen

tal v

alue

s (kN

middotm

)

150 200 250100Predicted values (kNmiddotm)

Figure 6 Comparison of experimental and predicted ultimatemoments

maximum strain of the stirrup respectively Accordingly thestress in the stirrup based upon the uniaxial stress-strainrelationship can be estimated to be 419MPa for S25-05d367MPa for S22-05d and 366MPa for S19-05d

Figure 11(b) plots the load with respect to the princi-pal strain measured in concrete The members underwentshear cracking at shear strain of 0000112 (specimen S19-0)0000113 (specimen S22-0) and 0000121 (specimen S25-0)The values of the concrete principal strain were calculatedby converting the strain measured by the strain gage rosette(Figure 2(b)) attached on the right-hand side of the criticalsection

ACI 318-08 [17] proposes the following formulae for thecalculation of the maximum shear stress Vcr of concrete

Simplified Formula

Vcr = 016radic119891ck (3)

Elaborated Formula

Vcr = 016radic119891ck + 176120588119881119889119872 le 029radic119891ck (4)

where119891ck is compressive strength of concrete 120588 is tensile steelratio 119881 is shear force at the critical section 119872 is bendingmoment at the critical section and 119889 is effective depth

If the compressive strength steel ratio shear force andbending moment are substituted in (3) Vcr = 119MPa andVcr takes values of 131MPa (S19-0) 137MPa (S22-0) and139MPa (S25-0) when (4) is used

Assuming the common value of 017 for Poissonrsquos ratio] the shear stress is calculated by multiplying the shearelastic modulus 119866 = 119864c[2(1 + ])] = 1406GPa by the shearstrain measured in the tests where the experimental elasticmodulus 119864c = 3291 GPa from Table 2 The correspondingshear stress becomes 158MPa (S19-0) 159MPa (S22-0)and 170MPa (S25-0) This shows that the principal stressobtained experimentally is slightly larger than that predictedby the design formulae in (3) and (4)

33 Comparison of Experimental Shear Strength and DesignValues Table 6 compares the shear strengths obtained fromthe test with those suggested by the design code In Table 6ldquoTestrdquo indicates the values based upon the loads measured inthe test and ldquoAnalysisrdquo designates the values computed fromthe strain measured in the test Recalling that specimen S19-05d failed through flexure S19-05d and S19-0 are discardedbecause the comparison of the shear strength is meaningless

Advances in Materials Science and Engineering 7

(a)

(b)

(c)

(d)

(e)

(f)

Figure 7 Crack pattern of shear test specimens (a) S25-05d (b) S22-05d (c) S19-05d (d) S25-0 (e) S22-0 and (f) S19-0

Table 6 Comparison of shear strengths from test and design code

Shear strength S25-05d S25-0 S22-05d S22-0Test (kN)119881c 853 853 1008 1008119881s 1643 mdash 1275 mdash119881u = 119881c + 119881s (incl self-weight) 2510 867 2296 1022

Design Code (kN)119881c 869 869 802 802119881s 1141 mdash 1141 mdash119881n = 119881c + 119881s 2010 869 1943 802

Test(119881u)Code(119881n) 125 100 118 127Analysis (kN)119881c 850 850 795 795119881s 1195 mdash 1047 mdash119881n = 119881c + 119881s (incl self-weight) 2059 864 1856 809

Test(119881u)Analysis(119881n) 122 100 124 126

8 Advances in Materials Science and Engineering

S25-05dS25-0S22-05d

S22-0S19-05dS19-0

0

100

200

300

400

500

600

Load

(kN

)

3 6 9 12 15 180Deflection (mm)

Figure 8 Load-deflection curves of shear test specimens

S25-05dS22-05dS19-05d

0007 0014 0021 0028 00350Strain of tensile steel (mmmm)

0

100

200

300

400

500

600

Load

(kN

)

(a) With stirrups

S25-0S22-0S19-0

0

50

100

150

200

250

Load

(kN

)

0001 0002 0003 00040Strain of tensile steel (mmmm)

(b) Without stirrup

Figure 9 Load versus strain of tensile steel in shear test specimens

for these members In addition the experimental shear forcecorresponds to the sum of the shear force obtained in thetest and the self-weight (135 kN = 25 times 03 times 02 times 182)the shear strength 119881c supported by concrete in the test is halfof the ultimate load of the specimens without stirrup (S25-0S22-0 S19-0) the shear strength 119881c provided by the designcode is the result of the application of (2) and the shearstrength sustained by the stirrups is calculated by applying119881s = 119860v119891y119889119904 where 119904 is the stirrup spacing The values of119881c in ldquoAnalysisrdquo are computed as the product of the principal

stress obtained in Figure 11(b) of Section 32 by the cross-sectional area of the specimen The values of 119881s in ldquoAnalysisrdquoare calculated as the product of the strain in the stirrupobtained in Figure 11(a) of Section 32 by the cross-sectionalarea of the reinforcement

The ratio of the experimental value to the value predictedby the design code (Test(119881u)Code(119881n)) ranges between100 and 127 and that of the experimental value to theanalytic value calculated from the experimental strain(Test(119881u)Analysis(119881n)) ranges between 100 and 126 which

Advances in Materials Science and Engineering 9

S25-05dS22-05dS19-05d

0

100

200

300

400

500

600Lo

ad (k

N)

0001 0002 0003 00040Strain of concrete (mmmm)

(a) With stirrups

S25-0S22-0S19-0

0

50

100

150

200

250

Load

(kN

)

00003 00006 00009 00012 000150Strain of concrete (mmmm)

(b) Without stirrup

Figure 10 Load versus flexural compressive strain of concrete in shear test specimens

S25-05dS22-05dS19-05d

0

100

200

300

400

500

600

Load

(kN

)

0003 0006 0009 0012 00150Shear strain (mmmm)

(a) Stirrups

S22-0S22-0S19-0

0

25

50

75

100

125

150

Load

(kN

)

000003 000006 000009 000012 0000150Shear strain (mmmm)

(b) Concrete

Figure 11 Load versus shear strain in shear test specimens

indicate that the analysis provides values larger by maximum26 and the similarity between the predictions of the designand the analysis

4 Finite Element Analysis

41 Method of Analysis The numerical analysis was carriedout using the nonlinear finite element program RCAHEST

developed by Kim et al [15] The analysis models consist ofa compression tension stiffening and shear transfer modelfor concrete and a model for embedded reinforcing steelThe concrete-reinforcement bond interaction is considered inboth the tension stiffening model for concrete and the modelfor reinforcement An earlier study [18] demonstrated that theabove-mentioned analysis model agreed reasonably with theexperimental data

10 Advances in Materials Science and Engineering

Uncracked

Isotropic Concrete

Reinforcingbar

Cracked

Orthotropic

Tensile

Specific stress-strain(i) Tension-stiffening model

(i) Bilinear model with bond

(ii) Shear transfer model(iii) Reduced compression model

Crackingcriteria

Compressive

model(i) Elastoplastic fracture

(i) Bare bar model

+

Equivalent stress-strain

effect

Figure 12 Outline of analysis model for reinforced high-strength concrete [15]

PredictionAnalysis

0

20

40

60

80

Stre

ss (M

Pa)

0001 0002 0003 0004 0005 00060Strain (mmmm)

Test

Figure 13 Comparison of experimental and predicted stress-straincurves

42 Material Models for Reinforced Concrete The nonlinearstress-strain relation of a reinforced concrete (RC) in-planeelement is formulated based on the concept of space averag-ing on the control volume The cracks and reinforcing barsare idealized as being distributed over the entire elementAlthough the local behavior of the crackedRC is not uniformin practical terms it can be treated as a continuum havingquasi-uniform stress and strain fields in a finite region Thematerial models aim to describe the overall behavior of astructure rather than a specific local behavior at the elementlevel In this paper the term ldquocrackrdquo explicitly refers to themacrocrack perpendicular to the principal tensile direction

According to the cracking criteria the analysis modelsare divided into models before and after the initiation ofcracks as shown in Figure 12Thematerialmodel for concreteprior to cracking is based on the elastoplastic fracture model[19] given in Figure 13 The local coordinate systems ofreinforcing bars are always assigned with respect to each baraxis but those of cracked concrete are determined according

F25-TestF25-AnalysisF22-Test

F22-AnalysisF19-TestF19-Analysis

0

50

100

150

200

250

300

350

Load

(kN

)

10 20 30 40 500Deflection (mm)

Figure 14 Comparison of experimental and analytical load-deflection curves for flexure test members

to the current major crack plane Once a smeared crack isinitiated it is treated as fixed in a direction and anisotropy isintroduced As loading step proceeds the principal directionof the average stress can be changed and the consequent sheartransfer model is involved in the constitutive law

5 Comparison of Experimental andAnalytical Results

51 Flexure Figure 14 compares the experimental and ana-lytical load-displacement curves for specimens F25 F22 andF19 The analytical results are in relatively good agreementwith the experimental values and indicate the validity of theanalytic model However for F25 with the largest tensile ratioconsidered in this study the test specimens exhibit slightbrittle failure compared to the analytical prediction The ini-tial slope of the experimental curves is on the whole smallerthan that of the analytical curves The different initial slopes

Advances in Materials Science and Engineering 11

S25-05d-TestS25-05d-AnalysisS22-05d-Test

S22-05d-AnalysisS19-05d-TestS19-05d-Analysis

0

100

200

300

400

500

600Lo

ad (k

N)

4 8 12 16 200Deflection (mm)

(a) With stirrups

0

100

200

300

400

Load

(kN

)

2 4 6 8 100Deflection (mm)

S25-05d-TestS25-05d-AnalysisS22-05d-Test

S22-05d-AnalysisS19-05d-TestS19-05d-Analysis

(b) Without stirrup

Figure 15 Comparison of experimental and analytical load-displacement curves for shear test members

of the analytical and experimental results can be attributedpartially to the stiffness adopted in the analytical model ofthe members and some experimental error Moreover theearly completion of the tests explains the different maximumdeflections of the analytical and experimental results In factlarger deflection would have been measured in the membersthat experienced failure through flexure but the tests wereinterrupted prematurely due to limitations in the capacity ofthe testing equipment and for the sake of safety

52 Shear Figure 15 compares the experimental and analyti-cal load-displacement curves of the shear test specimensTheanalytical results are in relatively good agreement with theexperimental values for the specimens with stirrups Herealso slight difference in the initial slope occurred as explainedabove in Section 51 Specimen S25-05d experienced suddenbrittle failure due to the clear occurrence of shear failureValues near the maximum load could not be measuredbecause of the delay in the acquisition of the data Besides thespecimenswithout stirrup showed smallermaximum loads inthe test than those of the analysis However considering thelarge experimental errors that are generally observed in theshear test of specimens without stirrup the results presentedhere demonstrate to some extent the good execution of thetests performed in this study

Here also the early ending of the tests explains thedifferent maximum deflections of the analytical and experi-mental results The members without stirrup in Figure 15(b)experienced sudden failure but the tests were interruptedprematurely due to limitations in the capacity of the testingequipment and for the sake of safety In addition it isextremely difficult to measure precisely the behavior of themembers without stirrup after the ultimate state when thefailure test is conducted using an actuator and through

displacement control On the other hand the similarity of theexperimental and analytical maximum deflections observedin Figure 15(a) was achieved because the members sufferedshear failure and reached a state close to their ultimate state atthe completion of the tests thanks to the presence of stirrups

6 Conclusions

This study evaluated experimentally and analytically thestructural behavior of reinforced concrete beams made ofAAS concrete The following conclusions can be drawn fromthe results

(1) The elastic modulus and the strain at maximum stressof AAS concrete were slightly smaller than thosepredicted for normal concrete This difference couldbe explained by the reduction in the unit mass ofAAS concrete caused by the smaller density of slagcompared to cement Further study shall proposeadequate models for the elastic modulus and stress-strain relation of AAS concrete

(2) The test results of the flexural members showedthat the ratio of the ultimate load to the yield loadof steel ranged between 115 and 141 and the loadbearing capacity improved with higher tensile steelratio The flexural behavior of the reinforced AASconcrete members appeared thus to be very similarto that of the reinforced concrete beam made ofnormal concrete because the reinforcing bars governthe flexural behavior of the members A nonlinearflexural analysis model was proposed using the elasticmodulus and stress-strain relation of AAS concreteThe analytical resultswere in good agreementwith the

12 Advances in Materials Science and Engineering

experimental results and demonstrated the validity ofthe analytical model

(3) The experimental shear strength obtained for themembers without stirrup was significantly higherthan that predicted by the design code which indi-cated the conservativeness of the design code Theshear behavior of the reinforced AAS concrete mem-bers varied according to the amount of tensile steel

(4) In view of the finite element analysis results reflectingthe nonlinearmodel ofAAS concrete used in previousstudies the flexural and shear behaviors of the AASconcrete specimenswere in relatively good agreementwith those predicted analytically

(5) Consequently the test results show that the flexuraland shear behaviors of the reinforced AAS concretemembers are very similar to those of the reinforcedconcrete beammade of normal concrete and render itpossible to apply conventional design code for flexureand shear in the design of reinforced AAS concretemembers Further studies are required for the practi-cal use of AAS concrete since this experimental studywas limited to specimens with specific dimensions

Conflicts of Interest

The authors declare that they have no conflicts of interest

Acknowledgments

This research was financially supported by the KoreanMinistry of Environment as ldquoPublic Technology ProgramBased on Environmental Policyrdquo (no 2016000700003) Thisresearch was also supported by a grant (Code 11-TechnologyInnovation-F04) from Construction Technology InnovationProgram (CTIP) funded by Ministry of Land and Transportof Korean government

References

[1] S-D Wang X-C Pu K L Scrivener and P L Pratt ldquoAlkali-activated slag cement and concrete a review of properties andproblemsrdquo Advances in Cement Research vol 7 no 27 pp 93ndash102 1995

[2] A Palomo MW Grutzeck andM T Blanco ldquoAlkali-activatedfly ashes a cement for the futurerdquo Cement and ConcreteResearch vol 29 no 8 pp 1323ndash1329 1999

[3] C Shi P V Krivenko and D Roy Alkali-activated cement andconcrete vol 376 Taylor amp Francis Abingdon UK 2006

[4] C Shi A F Jimenez and A Palomo ldquoNew cements for the21st century the pursuit of an alternative to Portland cementrdquoCement and Concrete Research vol 41 no 7 pp 750ndash763 2011

[5] A R Brough and A Atkinson ldquoSodium silicate-basedalkali-activated slag mortars part I Strength hydration andmicrostructurerdquo Cement and Concrete Research vol 32 no 6pp 865ndash879 2002

[6] S Aydin and B Baradan ldquoEffect of activator type and contenton properties of alkali-activated slag mortarsrdquo Composites PartB Engineering vol 57 pp 166ndash172 2014

[7] S H Oh S H Hong and K M Lee ldquoAutogenous shrinkageproperties of high strength alkali activated slag mortarrdquo Journalof the Korean Recycled Construction Resources Institute vol 2no 1 pp 60ndash65 2014

[8] F G Collins and J G Sanjayan ldquoWorkability and mechanicalproperties of alkali activated slag concreterdquo Cement and Con-crete Research vol 29 no 3 pp 455ndash458 1999

[9] M Sofi J S J van Deventer P A Mendis and G CLukey ldquoEngineering properties of inorganic polymer concretes(IPCs)rdquo Cement and Concrete Research vol 37 no 2 pp 251ndash257 2007

[10] C D Atis C Bilim O Celik and O Karahan ldquoInfluenceof activator on the strength and drying shrinkage of alkali-activated slag mortarrdquo Construction and Building Materials vol23 no 1 pp 548ndash555 2009

[11] A A Melo Neto M A Cincotto and W Repette ldquoDrying andautogenous shrinkage of pastes and mortars with activated slagcementrdquo Cement and Concrete Research vol 38 no 4 pp 565ndash574 2008

[12] F PuertasM Palacios andTVazquez ldquoCarbonation process ofalkali-activated slag mortarsrdquo Journal of Materials Science vol41 no 10 pp 3071ndash3082 2006

[13] K Lee and J Seo ldquoEvaluation of flexural behavior of reinforcedconcrete beams using alkali activated slag concreterdquo Journal ofthe Korea Concrete Institute vol 27 no 3 pp 311ndash317 2015

[14] S Choi K Lee and S Yoo ldquoShear behavior of RC beams usingalkali activated slag concreterdquo Journal of the Korean RecycledConstruction Resources Institute vol 3 no 1 pp 58ndash63 2015

[15] T-H Kim K-M Lee C Yoon and H M Shin ldquoInelasticbehavior and ductility capacity of reinforced concrete bridgepiers under earthquake I Theory and formulationrdquo Journal ofStructural Engineering vol 129 no 9 pp 1199ndash1207 2003

[16] E Thorenfeldt A Tomaszewicz and J J Jensen ldquoMechanicalproperties of high strength concrete and application in designrdquoin Proceedings of the Symposium Utilization of High StrengthConcrete T Trondheim Ed vol 40 pp 149ndash159 StravangerNorway 15ndash18 June 1987

[17] S-W Shin S K Ghosh and J Moreno ldquoFlexural ductility ofultra-high-strength concrete membersrdquoACI Structural Journalvol 86 no 4 pp 394ndash400 1989

[18] T-H Kim K-M Lee C Yoon and H M Shin ldquoInelasticbehavior and ductility capacity of reinforced concrete bridgepiers under earthquake II Numerical validationrdquo Journal ofStructural Engineering vol 129 no 9 pp 1208ndash1219 2003

[19] K Maekawa and H Okamura ldquoDeformational behavior andconstitutive equation of concrete using the elasto-plastic andfracture modelrdquo Journal of the Faculty of Engineering Universityof Tokyo Series B vol 37 no 2 pp 253ndash328 1983

Submit your manuscripts athttpswwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CeramicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CompositesJournal of

NanoparticlesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Biomaterials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MetallurgyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

MaterialsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in Materials Science and Engineering 5

Table 4 Crack yield and ultimate loads and corresponding center displacement of flexural test specimens

Member Crack load (kN) Yield Ultimate UltimateYield Failure modeLoad (kN) Deflection (mm) Load (kN) Deflection (mm) Load ratio Deflection ratio

F25 206 2725 138 3134 181 115 131 FlexureF22 244 1719 108 2423 245 141 227 FlexureF19 224 1556 109 1884 233 121 214 Flexure

Table 5 Crack yield and ultimate loads of shear test specimens

Member Crack load (kN) Yield load of tensile steel 119886 (kN) Ultimate load 119887 (kN) 119887119886 Failure modeFlexure Shear

S25-05d 346 1632 2285 2496 109 ShearS22-05d 309 1522 1446 2283 158 ShearS19-05d 251 1340 1275 1765 138 FlexureS25-0 307 1259 mdash 853 mdash ShearS22-0 282 1186 mdash 1008 mdash ShearS19-0 329 1129 943 1112 118 Flexural shear

F25F22F19

0

50

100

150

200

250

Appl

ied

mom

ent (

kNmiddotm

)

5 10 15 20 25 300Deflection (mm)

Figure 4 Comparison of load-deflection curves of flexural testspecimens

shear failure instead of pure shear failure due to the Dowelaction of the tensile reinforcement This explains the absenceof strength recovery after the loss of early strength

Figure 9 draws the load-strain curves of the tensilesteel measured in the shear test specimens In view of theresults presented in Table 5 and Figure 9 specimens S25-0 S25-05d and S22-0 experienced pure shear failure beforeyielding of the tensile reinforcement Specimen S25-05das the one having the largest arrangement of tensile steelexhibits small increase of the strain in the tensile steelbecause the specimen reached the ultimate load following theoccurrence of shear failure immediately after yielding of thetensile reinforcement Specimens S25-0 and S22-0 withoutstirrup and small arrangement of tensile steel experienced

sudden failure before yielding of the tensile steel once the loadexceeded the shear strength due to the absence of stirrups

On the other hand the other specimens saw their tensilereinforcement deform at shear failure and without increaseof the load because shear failure occurred after yielding ofthe tensile reinforcement Specimens S22-05d and S19-05dwith relatively small arrangement of tensile reinforcementexperienced large deformation after yielding of the tensilesteel and finally failed respectively through flexureshear orflexure Despite the absence of stirrups specimen S19-0 failedthrough flexureshear due to the small amount of tensilesteel and developed relatively larger strain than the otherspecimens without stirrup

Figure 10 plots the load with respect to the flexuralcompressive strain of concrete measured in the shear testspecimens Specimen S25-05d with large amount of tensilesteel failed before concrete reached its ultimate strain dueto the sudden occurrence of shear failure Specimens S22-05d and S19-05d reinforced by stirrups and small amountof tensile steel were the only ones to develop relatively largeconcrete strain up to 00035 because of the following reasonsSpecimen S22-05d experienced flexural failure at first due toits small amount of tensile steel and finally failed throughshear due to its small amount of stirrup Specimen S19-05d experienced flexural failure without shear failure dueto its smaller amount of tensile steel In addition amongthe members without stirrup specimens S25-0 and S22-0developed small concrete strain due to the sudden occurrenceof shear failure

Figure 11(a) plots the load with respect to the shearstrain measured in the stirrups It appears that the stirrupyielded only in specimen S25-05d and not in the othertwo specimens This is in agreement with the failure modeslisted in Table 5 which indicated pure shear failure inspecimen S25-05 flexure-shear failure in specimen S22-05dand flexural failure in specimen S19-05d Besides specimensS22-05d and S19-05d that did not experience yielding oftheir stirrup recorded values of 000263 and 000262 for the

6 Advances in Materials Science and Engineering

F25F22F19

0

50

100

150

200

250

300

350Lo

ad (k

N)

001 002 0030Strain of tensile steel (mmmm)

(a) Load-strain curves of tensile steel

F25F22F19

0001 0002 0003 00040Strain of concrete (mmmm)

0

50

100

150

200

250

300

350

Load

(kN

)(b) Load-strain curves of concrete

Figure 5 Load-strain curves of flexural test specimens according to steel ratio

Equal line

100

150

200

250

Expe

rimen

tal v

alue

s (kN

middotm

)

150 200 250100Predicted values (kNmiddotm)

Figure 6 Comparison of experimental and predicted ultimatemoments

maximum strain of the stirrup respectively Accordingly thestress in the stirrup based upon the uniaxial stress-strainrelationship can be estimated to be 419MPa for S25-05d367MPa for S22-05d and 366MPa for S19-05d

Figure 11(b) plots the load with respect to the princi-pal strain measured in concrete The members underwentshear cracking at shear strain of 0000112 (specimen S19-0)0000113 (specimen S22-0) and 0000121 (specimen S25-0)The values of the concrete principal strain were calculatedby converting the strain measured by the strain gage rosette(Figure 2(b)) attached on the right-hand side of the criticalsection

ACI 318-08 [17] proposes the following formulae for thecalculation of the maximum shear stress Vcr of concrete

Simplified Formula

Vcr = 016radic119891ck (3)

Elaborated Formula

Vcr = 016radic119891ck + 176120588119881119889119872 le 029radic119891ck (4)

where119891ck is compressive strength of concrete 120588 is tensile steelratio 119881 is shear force at the critical section 119872 is bendingmoment at the critical section and 119889 is effective depth

If the compressive strength steel ratio shear force andbending moment are substituted in (3) Vcr = 119MPa andVcr takes values of 131MPa (S19-0) 137MPa (S22-0) and139MPa (S25-0) when (4) is used

Assuming the common value of 017 for Poissonrsquos ratio] the shear stress is calculated by multiplying the shearelastic modulus 119866 = 119864c[2(1 + ])] = 1406GPa by the shearstrain measured in the tests where the experimental elasticmodulus 119864c = 3291 GPa from Table 2 The correspondingshear stress becomes 158MPa (S19-0) 159MPa (S22-0)and 170MPa (S25-0) This shows that the principal stressobtained experimentally is slightly larger than that predictedby the design formulae in (3) and (4)

33 Comparison of Experimental Shear Strength and DesignValues Table 6 compares the shear strengths obtained fromthe test with those suggested by the design code In Table 6ldquoTestrdquo indicates the values based upon the loads measured inthe test and ldquoAnalysisrdquo designates the values computed fromthe strain measured in the test Recalling that specimen S19-05d failed through flexure S19-05d and S19-0 are discardedbecause the comparison of the shear strength is meaningless

Advances in Materials Science and Engineering 7

(a)

(b)

(c)

(d)

(e)

(f)

Figure 7 Crack pattern of shear test specimens (a) S25-05d (b) S22-05d (c) S19-05d (d) S25-0 (e) S22-0 and (f) S19-0

Table 6 Comparison of shear strengths from test and design code

Shear strength S25-05d S25-0 S22-05d S22-0Test (kN)119881c 853 853 1008 1008119881s 1643 mdash 1275 mdash119881u = 119881c + 119881s (incl self-weight) 2510 867 2296 1022

Design Code (kN)119881c 869 869 802 802119881s 1141 mdash 1141 mdash119881n = 119881c + 119881s 2010 869 1943 802

Test(119881u)Code(119881n) 125 100 118 127Analysis (kN)119881c 850 850 795 795119881s 1195 mdash 1047 mdash119881n = 119881c + 119881s (incl self-weight) 2059 864 1856 809

Test(119881u)Analysis(119881n) 122 100 124 126

8 Advances in Materials Science and Engineering

S25-05dS25-0S22-05d

S22-0S19-05dS19-0

0

100

200

300

400

500

600

Load

(kN

)

3 6 9 12 15 180Deflection (mm)

Figure 8 Load-deflection curves of shear test specimens

S25-05dS22-05dS19-05d

0007 0014 0021 0028 00350Strain of tensile steel (mmmm)

0

100

200

300

400

500

600

Load

(kN

)

(a) With stirrups

S25-0S22-0S19-0

0

50

100

150

200

250

Load

(kN

)

0001 0002 0003 00040Strain of tensile steel (mmmm)

(b) Without stirrup

Figure 9 Load versus strain of tensile steel in shear test specimens

for these members In addition the experimental shear forcecorresponds to the sum of the shear force obtained in thetest and the self-weight (135 kN = 25 times 03 times 02 times 182)the shear strength 119881c supported by concrete in the test is halfof the ultimate load of the specimens without stirrup (S25-0S22-0 S19-0) the shear strength 119881c provided by the designcode is the result of the application of (2) and the shearstrength sustained by the stirrups is calculated by applying119881s = 119860v119891y119889119904 where 119904 is the stirrup spacing The values of119881c in ldquoAnalysisrdquo are computed as the product of the principal

stress obtained in Figure 11(b) of Section 32 by the cross-sectional area of the specimen The values of 119881s in ldquoAnalysisrdquoare calculated as the product of the strain in the stirrupobtained in Figure 11(a) of Section 32 by the cross-sectionalarea of the reinforcement

The ratio of the experimental value to the value predictedby the design code (Test(119881u)Code(119881n)) ranges between100 and 127 and that of the experimental value to theanalytic value calculated from the experimental strain(Test(119881u)Analysis(119881n)) ranges between 100 and 126 which

Advances in Materials Science and Engineering 9

S25-05dS22-05dS19-05d

0

100

200

300

400

500

600Lo

ad (k

N)

0001 0002 0003 00040Strain of concrete (mmmm)

(a) With stirrups

S25-0S22-0S19-0

0

50

100

150

200

250

Load

(kN

)

00003 00006 00009 00012 000150Strain of concrete (mmmm)

(b) Without stirrup

Figure 10 Load versus flexural compressive strain of concrete in shear test specimens

S25-05dS22-05dS19-05d

0

100

200

300

400

500

600

Load

(kN

)

0003 0006 0009 0012 00150Shear strain (mmmm)

(a) Stirrups

S22-0S22-0S19-0

0

25

50

75

100

125

150

Load

(kN

)

000003 000006 000009 000012 0000150Shear strain (mmmm)

(b) Concrete

Figure 11 Load versus shear strain in shear test specimens

indicate that the analysis provides values larger by maximum26 and the similarity between the predictions of the designand the analysis

4 Finite Element Analysis

41 Method of Analysis The numerical analysis was carriedout using the nonlinear finite element program RCAHEST

developed by Kim et al [15] The analysis models consist ofa compression tension stiffening and shear transfer modelfor concrete and a model for embedded reinforcing steelThe concrete-reinforcement bond interaction is considered inboth the tension stiffening model for concrete and the modelfor reinforcement An earlier study [18] demonstrated that theabove-mentioned analysis model agreed reasonably with theexperimental data

10 Advances in Materials Science and Engineering

Uncracked

Isotropic Concrete

Reinforcingbar

Cracked

Orthotropic

Tensile

Specific stress-strain(i) Tension-stiffening model

(i) Bilinear model with bond

(ii) Shear transfer model(iii) Reduced compression model

Crackingcriteria

Compressive

model(i) Elastoplastic fracture

(i) Bare bar model

+

Equivalent stress-strain

effect

Figure 12 Outline of analysis model for reinforced high-strength concrete [15]

PredictionAnalysis

0

20

40

60

80

Stre

ss (M

Pa)

0001 0002 0003 0004 0005 00060Strain (mmmm)

Test

Figure 13 Comparison of experimental and predicted stress-straincurves

42 Material Models for Reinforced Concrete The nonlinearstress-strain relation of a reinforced concrete (RC) in-planeelement is formulated based on the concept of space averag-ing on the control volume The cracks and reinforcing barsare idealized as being distributed over the entire elementAlthough the local behavior of the crackedRC is not uniformin practical terms it can be treated as a continuum havingquasi-uniform stress and strain fields in a finite region Thematerial models aim to describe the overall behavior of astructure rather than a specific local behavior at the elementlevel In this paper the term ldquocrackrdquo explicitly refers to themacrocrack perpendicular to the principal tensile direction

According to the cracking criteria the analysis modelsare divided into models before and after the initiation ofcracks as shown in Figure 12Thematerialmodel for concreteprior to cracking is based on the elastoplastic fracture model[19] given in Figure 13 The local coordinate systems ofreinforcing bars are always assigned with respect to each baraxis but those of cracked concrete are determined according

F25-TestF25-AnalysisF22-Test

F22-AnalysisF19-TestF19-Analysis

0

50

100

150

200

250

300

350

Load

(kN

)

10 20 30 40 500Deflection (mm)

Figure 14 Comparison of experimental and analytical load-deflection curves for flexure test members

to the current major crack plane Once a smeared crack isinitiated it is treated as fixed in a direction and anisotropy isintroduced As loading step proceeds the principal directionof the average stress can be changed and the consequent sheartransfer model is involved in the constitutive law

5 Comparison of Experimental andAnalytical Results

51 Flexure Figure 14 compares the experimental and ana-lytical load-displacement curves for specimens F25 F22 andF19 The analytical results are in relatively good agreementwith the experimental values and indicate the validity of theanalytic model However for F25 with the largest tensile ratioconsidered in this study the test specimens exhibit slightbrittle failure compared to the analytical prediction The ini-tial slope of the experimental curves is on the whole smallerthan that of the analytical curves The different initial slopes

Advances in Materials Science and Engineering 11

S25-05d-TestS25-05d-AnalysisS22-05d-Test

S22-05d-AnalysisS19-05d-TestS19-05d-Analysis

0

100

200

300

400

500

600Lo

ad (k

N)

4 8 12 16 200Deflection (mm)

(a) With stirrups

0

100

200

300

400

Load

(kN

)

2 4 6 8 100Deflection (mm)

S25-05d-TestS25-05d-AnalysisS22-05d-Test

S22-05d-AnalysisS19-05d-TestS19-05d-Analysis

(b) Without stirrup

Figure 15 Comparison of experimental and analytical load-displacement curves for shear test members

of the analytical and experimental results can be attributedpartially to the stiffness adopted in the analytical model ofthe members and some experimental error Moreover theearly completion of the tests explains the different maximumdeflections of the analytical and experimental results In factlarger deflection would have been measured in the membersthat experienced failure through flexure but the tests wereinterrupted prematurely due to limitations in the capacity ofthe testing equipment and for the sake of safety

52 Shear Figure 15 compares the experimental and analyti-cal load-displacement curves of the shear test specimensTheanalytical results are in relatively good agreement with theexperimental values for the specimens with stirrups Herealso slight difference in the initial slope occurred as explainedabove in Section 51 Specimen S25-05d experienced suddenbrittle failure due to the clear occurrence of shear failureValues near the maximum load could not be measuredbecause of the delay in the acquisition of the data Besides thespecimenswithout stirrup showed smallermaximum loads inthe test than those of the analysis However considering thelarge experimental errors that are generally observed in theshear test of specimens without stirrup the results presentedhere demonstrate to some extent the good execution of thetests performed in this study

Here also the early ending of the tests explains thedifferent maximum deflections of the analytical and experi-mental results The members without stirrup in Figure 15(b)experienced sudden failure but the tests were interruptedprematurely due to limitations in the capacity of the testingequipment and for the sake of safety In addition it isextremely difficult to measure precisely the behavior of themembers without stirrup after the ultimate state when thefailure test is conducted using an actuator and through

displacement control On the other hand the similarity of theexperimental and analytical maximum deflections observedin Figure 15(a) was achieved because the members sufferedshear failure and reached a state close to their ultimate state atthe completion of the tests thanks to the presence of stirrups

6 Conclusions

This study evaluated experimentally and analytically thestructural behavior of reinforced concrete beams made ofAAS concrete The following conclusions can be drawn fromthe results

(1) The elastic modulus and the strain at maximum stressof AAS concrete were slightly smaller than thosepredicted for normal concrete This difference couldbe explained by the reduction in the unit mass ofAAS concrete caused by the smaller density of slagcompared to cement Further study shall proposeadequate models for the elastic modulus and stress-strain relation of AAS concrete

(2) The test results of the flexural members showedthat the ratio of the ultimate load to the yield loadof steel ranged between 115 and 141 and the loadbearing capacity improved with higher tensile steelratio The flexural behavior of the reinforced AASconcrete members appeared thus to be very similarto that of the reinforced concrete beam made ofnormal concrete because the reinforcing bars governthe flexural behavior of the members A nonlinearflexural analysis model was proposed using the elasticmodulus and stress-strain relation of AAS concreteThe analytical resultswere in good agreementwith the

12 Advances in Materials Science and Engineering

experimental results and demonstrated the validity ofthe analytical model

(3) The experimental shear strength obtained for themembers without stirrup was significantly higherthan that predicted by the design code which indi-cated the conservativeness of the design code Theshear behavior of the reinforced AAS concrete mem-bers varied according to the amount of tensile steel

(4) In view of the finite element analysis results reflectingthe nonlinearmodel ofAAS concrete used in previousstudies the flexural and shear behaviors of the AASconcrete specimenswere in relatively good agreementwith those predicted analytically

(5) Consequently the test results show that the flexuraland shear behaviors of the reinforced AAS concretemembers are very similar to those of the reinforcedconcrete beammade of normal concrete and render itpossible to apply conventional design code for flexureand shear in the design of reinforced AAS concretemembers Further studies are required for the practi-cal use of AAS concrete since this experimental studywas limited to specimens with specific dimensions

Conflicts of Interest

The authors declare that they have no conflicts of interest

Acknowledgments

This research was financially supported by the KoreanMinistry of Environment as ldquoPublic Technology ProgramBased on Environmental Policyrdquo (no 2016000700003) Thisresearch was also supported by a grant (Code 11-TechnologyInnovation-F04) from Construction Technology InnovationProgram (CTIP) funded by Ministry of Land and Transportof Korean government

References

[1] S-D Wang X-C Pu K L Scrivener and P L Pratt ldquoAlkali-activated slag cement and concrete a review of properties andproblemsrdquo Advances in Cement Research vol 7 no 27 pp 93ndash102 1995

[2] A Palomo MW Grutzeck andM T Blanco ldquoAlkali-activatedfly ashes a cement for the futurerdquo Cement and ConcreteResearch vol 29 no 8 pp 1323ndash1329 1999

[3] C Shi P V Krivenko and D Roy Alkali-activated cement andconcrete vol 376 Taylor amp Francis Abingdon UK 2006

[4] C Shi A F Jimenez and A Palomo ldquoNew cements for the21st century the pursuit of an alternative to Portland cementrdquoCement and Concrete Research vol 41 no 7 pp 750ndash763 2011

[5] A R Brough and A Atkinson ldquoSodium silicate-basedalkali-activated slag mortars part I Strength hydration andmicrostructurerdquo Cement and Concrete Research vol 32 no 6pp 865ndash879 2002

[6] S Aydin and B Baradan ldquoEffect of activator type and contenton properties of alkali-activated slag mortarsrdquo Composites PartB Engineering vol 57 pp 166ndash172 2014

[7] S H Oh S H Hong and K M Lee ldquoAutogenous shrinkageproperties of high strength alkali activated slag mortarrdquo Journalof the Korean Recycled Construction Resources Institute vol 2no 1 pp 60ndash65 2014

[8] F G Collins and J G Sanjayan ldquoWorkability and mechanicalproperties of alkali activated slag concreterdquo Cement and Con-crete Research vol 29 no 3 pp 455ndash458 1999

[9] M Sofi J S J van Deventer P A Mendis and G CLukey ldquoEngineering properties of inorganic polymer concretes(IPCs)rdquo Cement and Concrete Research vol 37 no 2 pp 251ndash257 2007

[10] C D Atis C Bilim O Celik and O Karahan ldquoInfluenceof activator on the strength and drying shrinkage of alkali-activated slag mortarrdquo Construction and Building Materials vol23 no 1 pp 548ndash555 2009

[11] A A Melo Neto M A Cincotto and W Repette ldquoDrying andautogenous shrinkage of pastes and mortars with activated slagcementrdquo Cement and Concrete Research vol 38 no 4 pp 565ndash574 2008

[12] F PuertasM Palacios andTVazquez ldquoCarbonation process ofalkali-activated slag mortarsrdquo Journal of Materials Science vol41 no 10 pp 3071ndash3082 2006

[13] K Lee and J Seo ldquoEvaluation of flexural behavior of reinforcedconcrete beams using alkali activated slag concreterdquo Journal ofthe Korea Concrete Institute vol 27 no 3 pp 311ndash317 2015

[14] S Choi K Lee and S Yoo ldquoShear behavior of RC beams usingalkali activated slag concreterdquo Journal of the Korean RecycledConstruction Resources Institute vol 3 no 1 pp 58ndash63 2015

[15] T-H Kim K-M Lee C Yoon and H M Shin ldquoInelasticbehavior and ductility capacity of reinforced concrete bridgepiers under earthquake I Theory and formulationrdquo Journal ofStructural Engineering vol 129 no 9 pp 1199ndash1207 2003

[16] E Thorenfeldt A Tomaszewicz and J J Jensen ldquoMechanicalproperties of high strength concrete and application in designrdquoin Proceedings of the Symposium Utilization of High StrengthConcrete T Trondheim Ed vol 40 pp 149ndash159 StravangerNorway 15ndash18 June 1987

[17] S-W Shin S K Ghosh and J Moreno ldquoFlexural ductility ofultra-high-strength concrete membersrdquoACI Structural Journalvol 86 no 4 pp 394ndash400 1989

[18] T-H Kim K-M Lee C Yoon and H M Shin ldquoInelasticbehavior and ductility capacity of reinforced concrete bridgepiers under earthquake II Numerical validationrdquo Journal ofStructural Engineering vol 129 no 9 pp 1208ndash1219 2003

[19] K Maekawa and H Okamura ldquoDeformational behavior andconstitutive equation of concrete using the elasto-plastic andfracture modelrdquo Journal of the Faculty of Engineering Universityof Tokyo Series B vol 37 no 2 pp 253ndash328 1983

Submit your manuscripts athttpswwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CeramicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CompositesJournal of

NanoparticlesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Biomaterials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MetallurgyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

MaterialsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

6 Advances in Materials Science and Engineering

F25F22F19

0

50

100

150

200

250

300

350Lo

ad (k

N)

001 002 0030Strain of tensile steel (mmmm)

(a) Load-strain curves of tensile steel

F25F22F19

0001 0002 0003 00040Strain of concrete (mmmm)

0

50

100

150

200

250

300

350

Load

(kN

)(b) Load-strain curves of concrete

Figure 5 Load-strain curves of flexural test specimens according to steel ratio

Equal line

100

150

200

250

Expe

rimen

tal v

alue

s (kN

middotm

)

150 200 250100Predicted values (kNmiddotm)

Figure 6 Comparison of experimental and predicted ultimatemoments

maximum strain of the stirrup respectively Accordingly thestress in the stirrup based upon the uniaxial stress-strainrelationship can be estimated to be 419MPa for S25-05d367MPa for S22-05d and 366MPa for S19-05d

Figure 11(b) plots the load with respect to the princi-pal strain measured in concrete The members underwentshear cracking at shear strain of 0000112 (specimen S19-0)0000113 (specimen S22-0) and 0000121 (specimen S25-0)The values of the concrete principal strain were calculatedby converting the strain measured by the strain gage rosette(Figure 2(b)) attached on the right-hand side of the criticalsection

ACI 318-08 [17] proposes the following formulae for thecalculation of the maximum shear stress Vcr of concrete

Simplified Formula

Vcr = 016radic119891ck (3)

Elaborated Formula

Vcr = 016radic119891ck + 176120588119881119889119872 le 029radic119891ck (4)

where119891ck is compressive strength of concrete 120588 is tensile steelratio 119881 is shear force at the critical section 119872 is bendingmoment at the critical section and 119889 is effective depth

If the compressive strength steel ratio shear force andbending moment are substituted in (3) Vcr = 119MPa andVcr takes values of 131MPa (S19-0) 137MPa (S22-0) and139MPa (S25-0) when (4) is used

Assuming the common value of 017 for Poissonrsquos ratio] the shear stress is calculated by multiplying the shearelastic modulus 119866 = 119864c[2(1 + ])] = 1406GPa by the shearstrain measured in the tests where the experimental elasticmodulus 119864c = 3291 GPa from Table 2 The correspondingshear stress becomes 158MPa (S19-0) 159MPa (S22-0)and 170MPa (S25-0) This shows that the principal stressobtained experimentally is slightly larger than that predictedby the design formulae in (3) and (4)

33 Comparison of Experimental Shear Strength and DesignValues Table 6 compares the shear strengths obtained fromthe test with those suggested by the design code In Table 6ldquoTestrdquo indicates the values based upon the loads measured inthe test and ldquoAnalysisrdquo designates the values computed fromthe strain measured in the test Recalling that specimen S19-05d failed through flexure S19-05d and S19-0 are discardedbecause the comparison of the shear strength is meaningless

Advances in Materials Science and Engineering 7

(a)

(b)

(c)

(d)

(e)

(f)

Figure 7 Crack pattern of shear test specimens (a) S25-05d (b) S22-05d (c) S19-05d (d) S25-0 (e) S22-0 and (f) S19-0

Table 6 Comparison of shear strengths from test and design code

Shear strength S25-05d S25-0 S22-05d S22-0Test (kN)119881c 853 853 1008 1008119881s 1643 mdash 1275 mdash119881u = 119881c + 119881s (incl self-weight) 2510 867 2296 1022

Design Code (kN)119881c 869 869 802 802119881s 1141 mdash 1141 mdash119881n = 119881c + 119881s 2010 869 1943 802

Test(119881u)Code(119881n) 125 100 118 127Analysis (kN)119881c 850 850 795 795119881s 1195 mdash 1047 mdash119881n = 119881c + 119881s (incl self-weight) 2059 864 1856 809

Test(119881u)Analysis(119881n) 122 100 124 126

8 Advances in Materials Science and Engineering

S25-05dS25-0S22-05d

S22-0S19-05dS19-0

0

100

200

300

400

500

600

Load

(kN

)

3 6 9 12 15 180Deflection (mm)

Figure 8 Load-deflection curves of shear test specimens

S25-05dS22-05dS19-05d

0007 0014 0021 0028 00350Strain of tensile steel (mmmm)

0

100

200

300

400

500

600

Load

(kN

)

(a) With stirrups

S25-0S22-0S19-0

0

50

100

150

200

250

Load

(kN

)

0001 0002 0003 00040Strain of tensile steel (mmmm)

(b) Without stirrup

Figure 9 Load versus strain of tensile steel in shear test specimens

for these members In addition the experimental shear forcecorresponds to the sum of the shear force obtained in thetest and the self-weight (135 kN = 25 times 03 times 02 times 182)the shear strength 119881c supported by concrete in the test is halfof the ultimate load of the specimens without stirrup (S25-0S22-0 S19-0) the shear strength 119881c provided by the designcode is the result of the application of (2) and the shearstrength sustained by the stirrups is calculated by applying119881s = 119860v119891y119889119904 where 119904 is the stirrup spacing The values of119881c in ldquoAnalysisrdquo are computed as the product of the principal

stress obtained in Figure 11(b) of Section 32 by the cross-sectional area of the specimen The values of 119881s in ldquoAnalysisrdquoare calculated as the product of the strain in the stirrupobtained in Figure 11(a) of Section 32 by the cross-sectionalarea of the reinforcement

The ratio of the experimental value to the value predictedby the design code (Test(119881u)Code(119881n)) ranges between100 and 127 and that of the experimental value to theanalytic value calculated from the experimental strain(Test(119881u)Analysis(119881n)) ranges between 100 and 126 which

Advances in Materials Science and Engineering 9

S25-05dS22-05dS19-05d

0

100

200

300

400

500

600Lo

ad (k

N)

0001 0002 0003 00040Strain of concrete (mmmm)

(a) With stirrups

S25-0S22-0S19-0

0

50

100

150

200

250

Load

(kN

)

00003 00006 00009 00012 000150Strain of concrete (mmmm)

(b) Without stirrup

Figure 10 Load versus flexural compressive strain of concrete in shear test specimens

S25-05dS22-05dS19-05d

0

100

200

300

400

500

600

Load

(kN

)

0003 0006 0009 0012 00150Shear strain (mmmm)

(a) Stirrups

S22-0S22-0S19-0

0

25

50

75

100

125

150

Load

(kN

)

000003 000006 000009 000012 0000150Shear strain (mmmm)

(b) Concrete

Figure 11 Load versus shear strain in shear test specimens

indicate that the analysis provides values larger by maximum26 and the similarity between the predictions of the designand the analysis

4 Finite Element Analysis

41 Method of Analysis The numerical analysis was carriedout using the nonlinear finite element program RCAHEST

developed by Kim et al [15] The analysis models consist ofa compression tension stiffening and shear transfer modelfor concrete and a model for embedded reinforcing steelThe concrete-reinforcement bond interaction is considered inboth the tension stiffening model for concrete and the modelfor reinforcement An earlier study [18] demonstrated that theabove-mentioned analysis model agreed reasonably with theexperimental data

10 Advances in Materials Science and Engineering

Uncracked

Isotropic Concrete

Reinforcingbar

Cracked

Orthotropic

Tensile

Specific stress-strain(i) Tension-stiffening model

(i) Bilinear model with bond

(ii) Shear transfer model(iii) Reduced compression model

Crackingcriteria

Compressive

model(i) Elastoplastic fracture

(i) Bare bar model

+

Equivalent stress-strain

effect

Figure 12 Outline of analysis model for reinforced high-strength concrete [15]

PredictionAnalysis

0

20

40

60

80

Stre

ss (M

Pa)

0001 0002 0003 0004 0005 00060Strain (mmmm)

Test

Figure 13 Comparison of experimental and predicted stress-straincurves

42 Material Models for Reinforced Concrete The nonlinearstress-strain relation of a reinforced concrete (RC) in-planeelement is formulated based on the concept of space averag-ing on the control volume The cracks and reinforcing barsare idealized as being distributed over the entire elementAlthough the local behavior of the crackedRC is not uniformin practical terms it can be treated as a continuum havingquasi-uniform stress and strain fields in a finite region Thematerial models aim to describe the overall behavior of astructure rather than a specific local behavior at the elementlevel In this paper the term ldquocrackrdquo explicitly refers to themacrocrack perpendicular to the principal tensile direction

According to the cracking criteria the analysis modelsare divided into models before and after the initiation ofcracks as shown in Figure 12Thematerialmodel for concreteprior to cracking is based on the elastoplastic fracture model[19] given in Figure 13 The local coordinate systems ofreinforcing bars are always assigned with respect to each baraxis but those of cracked concrete are determined according

F25-TestF25-AnalysisF22-Test

F22-AnalysisF19-TestF19-Analysis

0

50

100

150

200

250

300

350

Load

(kN

)

10 20 30 40 500Deflection (mm)

Figure 14 Comparison of experimental and analytical load-deflection curves for flexure test members

to the current major crack plane Once a smeared crack isinitiated it is treated as fixed in a direction and anisotropy isintroduced As loading step proceeds the principal directionof the average stress can be changed and the consequent sheartransfer model is involved in the constitutive law

5 Comparison of Experimental andAnalytical Results

51 Flexure Figure 14 compares the experimental and ana-lytical load-displacement curves for specimens F25 F22 andF19 The analytical results are in relatively good agreementwith the experimental values and indicate the validity of theanalytic model However for F25 with the largest tensile ratioconsidered in this study the test specimens exhibit slightbrittle failure compared to the analytical prediction The ini-tial slope of the experimental curves is on the whole smallerthan that of the analytical curves The different initial slopes

Advances in Materials Science and Engineering 11

S25-05d-TestS25-05d-AnalysisS22-05d-Test

S22-05d-AnalysisS19-05d-TestS19-05d-Analysis

0

100

200

300

400

500

600Lo

ad (k

N)

4 8 12 16 200Deflection (mm)

(a) With stirrups

0

100

200

300

400

Load

(kN

)

2 4 6 8 100Deflection (mm)

S25-05d-TestS25-05d-AnalysisS22-05d-Test

S22-05d-AnalysisS19-05d-TestS19-05d-Analysis

(b) Without stirrup

Figure 15 Comparison of experimental and analytical load-displacement curves for shear test members

of the analytical and experimental results can be attributedpartially to the stiffness adopted in the analytical model ofthe members and some experimental error Moreover theearly completion of the tests explains the different maximumdeflections of the analytical and experimental results In factlarger deflection would have been measured in the membersthat experienced failure through flexure but the tests wereinterrupted prematurely due to limitations in the capacity ofthe testing equipment and for the sake of safety

52 Shear Figure 15 compares the experimental and analyti-cal load-displacement curves of the shear test specimensTheanalytical results are in relatively good agreement with theexperimental values for the specimens with stirrups Herealso slight difference in the initial slope occurred as explainedabove in Section 51 Specimen S25-05d experienced suddenbrittle failure due to the clear occurrence of shear failureValues near the maximum load could not be measuredbecause of the delay in the acquisition of the data Besides thespecimenswithout stirrup showed smallermaximum loads inthe test than those of the analysis However considering thelarge experimental errors that are generally observed in theshear test of specimens without stirrup the results presentedhere demonstrate to some extent the good execution of thetests performed in this study

Here also the early ending of the tests explains thedifferent maximum deflections of the analytical and experi-mental results The members without stirrup in Figure 15(b)experienced sudden failure but the tests were interruptedprematurely due to limitations in the capacity of the testingequipment and for the sake of safety In addition it isextremely difficult to measure precisely the behavior of themembers without stirrup after the ultimate state when thefailure test is conducted using an actuator and through

displacement control On the other hand the similarity of theexperimental and analytical maximum deflections observedin Figure 15(a) was achieved because the members sufferedshear failure and reached a state close to their ultimate state atthe completion of the tests thanks to the presence of stirrups

6 Conclusions

This study evaluated experimentally and analytically thestructural behavior of reinforced concrete beams made ofAAS concrete The following conclusions can be drawn fromthe results

(1) The elastic modulus and the strain at maximum stressof AAS concrete were slightly smaller than thosepredicted for normal concrete This difference couldbe explained by the reduction in the unit mass ofAAS concrete caused by the smaller density of slagcompared to cement Further study shall proposeadequate models for the elastic modulus and stress-strain relation of AAS concrete

(2) The test results of the flexural members showedthat the ratio of the ultimate load to the yield loadof steel ranged between 115 and 141 and the loadbearing capacity improved with higher tensile steelratio The flexural behavior of the reinforced AASconcrete members appeared thus to be very similarto that of the reinforced concrete beam made ofnormal concrete because the reinforcing bars governthe flexural behavior of the members A nonlinearflexural analysis model was proposed using the elasticmodulus and stress-strain relation of AAS concreteThe analytical resultswere in good agreementwith the

12 Advances in Materials Science and Engineering

experimental results and demonstrated the validity ofthe analytical model

(3) The experimental shear strength obtained for themembers without stirrup was significantly higherthan that predicted by the design code which indi-cated the conservativeness of the design code Theshear behavior of the reinforced AAS concrete mem-bers varied according to the amount of tensile steel

(4) In view of the finite element analysis results reflectingthe nonlinearmodel ofAAS concrete used in previousstudies the flexural and shear behaviors of the AASconcrete specimenswere in relatively good agreementwith those predicted analytically

(5) Consequently the test results show that the flexuraland shear behaviors of the reinforced AAS concretemembers are very similar to those of the reinforcedconcrete beammade of normal concrete and render itpossible to apply conventional design code for flexureand shear in the design of reinforced AAS concretemembers Further studies are required for the practi-cal use of AAS concrete since this experimental studywas limited to specimens with specific dimensions

Conflicts of Interest

The authors declare that they have no conflicts of interest

Acknowledgments

This research was financially supported by the KoreanMinistry of Environment as ldquoPublic Technology ProgramBased on Environmental Policyrdquo (no 2016000700003) Thisresearch was also supported by a grant (Code 11-TechnologyInnovation-F04) from Construction Technology InnovationProgram (CTIP) funded by Ministry of Land and Transportof Korean government

References

[1] S-D Wang X-C Pu K L Scrivener and P L Pratt ldquoAlkali-activated slag cement and concrete a review of properties andproblemsrdquo Advances in Cement Research vol 7 no 27 pp 93ndash102 1995

[2] A Palomo MW Grutzeck andM T Blanco ldquoAlkali-activatedfly ashes a cement for the futurerdquo Cement and ConcreteResearch vol 29 no 8 pp 1323ndash1329 1999

[3] C Shi P V Krivenko and D Roy Alkali-activated cement andconcrete vol 376 Taylor amp Francis Abingdon UK 2006

[4] C Shi A F Jimenez and A Palomo ldquoNew cements for the21st century the pursuit of an alternative to Portland cementrdquoCement and Concrete Research vol 41 no 7 pp 750ndash763 2011

[5] A R Brough and A Atkinson ldquoSodium silicate-basedalkali-activated slag mortars part I Strength hydration andmicrostructurerdquo Cement and Concrete Research vol 32 no 6pp 865ndash879 2002

[6] S Aydin and B Baradan ldquoEffect of activator type and contenton properties of alkali-activated slag mortarsrdquo Composites PartB Engineering vol 57 pp 166ndash172 2014

[7] S H Oh S H Hong and K M Lee ldquoAutogenous shrinkageproperties of high strength alkali activated slag mortarrdquo Journalof the Korean Recycled Construction Resources Institute vol 2no 1 pp 60ndash65 2014

[8] F G Collins and J G Sanjayan ldquoWorkability and mechanicalproperties of alkali activated slag concreterdquo Cement and Con-crete Research vol 29 no 3 pp 455ndash458 1999

[9] M Sofi J S J van Deventer P A Mendis and G CLukey ldquoEngineering properties of inorganic polymer concretes(IPCs)rdquo Cement and Concrete Research vol 37 no 2 pp 251ndash257 2007

[10] C D Atis C Bilim O Celik and O Karahan ldquoInfluenceof activator on the strength and drying shrinkage of alkali-activated slag mortarrdquo Construction and Building Materials vol23 no 1 pp 548ndash555 2009

[11] A A Melo Neto M A Cincotto and W Repette ldquoDrying andautogenous shrinkage of pastes and mortars with activated slagcementrdquo Cement and Concrete Research vol 38 no 4 pp 565ndash574 2008

[12] F PuertasM Palacios andTVazquez ldquoCarbonation process ofalkali-activated slag mortarsrdquo Journal of Materials Science vol41 no 10 pp 3071ndash3082 2006

[13] K Lee and J Seo ldquoEvaluation of flexural behavior of reinforcedconcrete beams using alkali activated slag concreterdquo Journal ofthe Korea Concrete Institute vol 27 no 3 pp 311ndash317 2015

[14] S Choi K Lee and S Yoo ldquoShear behavior of RC beams usingalkali activated slag concreterdquo Journal of the Korean RecycledConstruction Resources Institute vol 3 no 1 pp 58ndash63 2015

[15] T-H Kim K-M Lee C Yoon and H M Shin ldquoInelasticbehavior and ductility capacity of reinforced concrete bridgepiers under earthquake I Theory and formulationrdquo Journal ofStructural Engineering vol 129 no 9 pp 1199ndash1207 2003

[16] E Thorenfeldt A Tomaszewicz and J J Jensen ldquoMechanicalproperties of high strength concrete and application in designrdquoin Proceedings of the Symposium Utilization of High StrengthConcrete T Trondheim Ed vol 40 pp 149ndash159 StravangerNorway 15ndash18 June 1987

[17] S-W Shin S K Ghosh and J Moreno ldquoFlexural ductility ofultra-high-strength concrete membersrdquoACI Structural Journalvol 86 no 4 pp 394ndash400 1989

[18] T-H Kim K-M Lee C Yoon and H M Shin ldquoInelasticbehavior and ductility capacity of reinforced concrete bridgepiers under earthquake II Numerical validationrdquo Journal ofStructural Engineering vol 129 no 9 pp 1208ndash1219 2003

[19] K Maekawa and H Okamura ldquoDeformational behavior andconstitutive equation of concrete using the elasto-plastic andfracture modelrdquo Journal of the Faculty of Engineering Universityof Tokyo Series B vol 37 no 2 pp 253ndash328 1983

Submit your manuscripts athttpswwwhindawicom

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Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

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CeramicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CompositesJournal of

NanoparticlesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

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Biomaterials

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NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

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NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

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CrystallographyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

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CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MetallurgyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

MaterialsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in Materials Science and Engineering 7

(a)

(b)

(c)

(d)

(e)

(f)

Figure 7 Crack pattern of shear test specimens (a) S25-05d (b) S22-05d (c) S19-05d (d) S25-0 (e) S22-0 and (f) S19-0

Table 6 Comparison of shear strengths from test and design code

Shear strength S25-05d S25-0 S22-05d S22-0Test (kN)119881c 853 853 1008 1008119881s 1643 mdash 1275 mdash119881u = 119881c + 119881s (incl self-weight) 2510 867 2296 1022

Design Code (kN)119881c 869 869 802 802119881s 1141 mdash 1141 mdash119881n = 119881c + 119881s 2010 869 1943 802

Test(119881u)Code(119881n) 125 100 118 127Analysis (kN)119881c 850 850 795 795119881s 1195 mdash 1047 mdash119881n = 119881c + 119881s (incl self-weight) 2059 864 1856 809

Test(119881u)Analysis(119881n) 122 100 124 126

8 Advances in Materials Science and Engineering

S25-05dS25-0S22-05d

S22-0S19-05dS19-0

0

100

200

300

400

500

600

Load

(kN

)

3 6 9 12 15 180Deflection (mm)

Figure 8 Load-deflection curves of shear test specimens

S25-05dS22-05dS19-05d

0007 0014 0021 0028 00350Strain of tensile steel (mmmm)

0

100

200

300

400

500

600

Load

(kN

)

(a) With stirrups

S25-0S22-0S19-0

0

50

100

150

200

250

Load

(kN

)

0001 0002 0003 00040Strain of tensile steel (mmmm)

(b) Without stirrup

Figure 9 Load versus strain of tensile steel in shear test specimens

for these members In addition the experimental shear forcecorresponds to the sum of the shear force obtained in thetest and the self-weight (135 kN = 25 times 03 times 02 times 182)the shear strength 119881c supported by concrete in the test is halfof the ultimate load of the specimens without stirrup (S25-0S22-0 S19-0) the shear strength 119881c provided by the designcode is the result of the application of (2) and the shearstrength sustained by the stirrups is calculated by applying119881s = 119860v119891y119889119904 where 119904 is the stirrup spacing The values of119881c in ldquoAnalysisrdquo are computed as the product of the principal

stress obtained in Figure 11(b) of Section 32 by the cross-sectional area of the specimen The values of 119881s in ldquoAnalysisrdquoare calculated as the product of the strain in the stirrupobtained in Figure 11(a) of Section 32 by the cross-sectionalarea of the reinforcement

The ratio of the experimental value to the value predictedby the design code (Test(119881u)Code(119881n)) ranges between100 and 127 and that of the experimental value to theanalytic value calculated from the experimental strain(Test(119881u)Analysis(119881n)) ranges between 100 and 126 which

Advances in Materials Science and Engineering 9

S25-05dS22-05dS19-05d

0

100

200

300

400

500

600Lo

ad (k

N)

0001 0002 0003 00040Strain of concrete (mmmm)

(a) With stirrups

S25-0S22-0S19-0

0

50

100

150

200

250

Load

(kN

)

00003 00006 00009 00012 000150Strain of concrete (mmmm)

(b) Without stirrup

Figure 10 Load versus flexural compressive strain of concrete in shear test specimens

S25-05dS22-05dS19-05d

0

100

200

300

400

500

600

Load

(kN

)

0003 0006 0009 0012 00150Shear strain (mmmm)

(a) Stirrups

S22-0S22-0S19-0

0

25

50

75

100

125

150

Load

(kN

)

000003 000006 000009 000012 0000150Shear strain (mmmm)

(b) Concrete

Figure 11 Load versus shear strain in shear test specimens

indicate that the analysis provides values larger by maximum26 and the similarity between the predictions of the designand the analysis

4 Finite Element Analysis

41 Method of Analysis The numerical analysis was carriedout using the nonlinear finite element program RCAHEST

developed by Kim et al [15] The analysis models consist ofa compression tension stiffening and shear transfer modelfor concrete and a model for embedded reinforcing steelThe concrete-reinforcement bond interaction is considered inboth the tension stiffening model for concrete and the modelfor reinforcement An earlier study [18] demonstrated that theabove-mentioned analysis model agreed reasonably with theexperimental data

10 Advances in Materials Science and Engineering

Uncracked

Isotropic Concrete

Reinforcingbar

Cracked

Orthotropic

Tensile

Specific stress-strain(i) Tension-stiffening model

(i) Bilinear model with bond

(ii) Shear transfer model(iii) Reduced compression model

Crackingcriteria

Compressive

model(i) Elastoplastic fracture

(i) Bare bar model

+

Equivalent stress-strain

effect

Figure 12 Outline of analysis model for reinforced high-strength concrete [15]

PredictionAnalysis

0

20

40

60

80

Stre

ss (M

Pa)

0001 0002 0003 0004 0005 00060Strain (mmmm)

Test

Figure 13 Comparison of experimental and predicted stress-straincurves

42 Material Models for Reinforced Concrete The nonlinearstress-strain relation of a reinforced concrete (RC) in-planeelement is formulated based on the concept of space averag-ing on the control volume The cracks and reinforcing barsare idealized as being distributed over the entire elementAlthough the local behavior of the crackedRC is not uniformin practical terms it can be treated as a continuum havingquasi-uniform stress and strain fields in a finite region Thematerial models aim to describe the overall behavior of astructure rather than a specific local behavior at the elementlevel In this paper the term ldquocrackrdquo explicitly refers to themacrocrack perpendicular to the principal tensile direction

According to the cracking criteria the analysis modelsare divided into models before and after the initiation ofcracks as shown in Figure 12Thematerialmodel for concreteprior to cracking is based on the elastoplastic fracture model[19] given in Figure 13 The local coordinate systems ofreinforcing bars are always assigned with respect to each baraxis but those of cracked concrete are determined according

F25-TestF25-AnalysisF22-Test

F22-AnalysisF19-TestF19-Analysis

0

50

100

150

200

250

300

350

Load

(kN

)

10 20 30 40 500Deflection (mm)

Figure 14 Comparison of experimental and analytical load-deflection curves for flexure test members

to the current major crack plane Once a smeared crack isinitiated it is treated as fixed in a direction and anisotropy isintroduced As loading step proceeds the principal directionof the average stress can be changed and the consequent sheartransfer model is involved in the constitutive law

5 Comparison of Experimental andAnalytical Results

51 Flexure Figure 14 compares the experimental and ana-lytical load-displacement curves for specimens F25 F22 andF19 The analytical results are in relatively good agreementwith the experimental values and indicate the validity of theanalytic model However for F25 with the largest tensile ratioconsidered in this study the test specimens exhibit slightbrittle failure compared to the analytical prediction The ini-tial slope of the experimental curves is on the whole smallerthan that of the analytical curves The different initial slopes

Advances in Materials Science and Engineering 11

S25-05d-TestS25-05d-AnalysisS22-05d-Test

S22-05d-AnalysisS19-05d-TestS19-05d-Analysis

0

100

200

300

400

500

600Lo

ad (k

N)

4 8 12 16 200Deflection (mm)

(a) With stirrups

0

100

200

300

400

Load

(kN

)

2 4 6 8 100Deflection (mm)

S25-05d-TestS25-05d-AnalysisS22-05d-Test

S22-05d-AnalysisS19-05d-TestS19-05d-Analysis

(b) Without stirrup

Figure 15 Comparison of experimental and analytical load-displacement curves for shear test members

of the analytical and experimental results can be attributedpartially to the stiffness adopted in the analytical model ofthe members and some experimental error Moreover theearly completion of the tests explains the different maximumdeflections of the analytical and experimental results In factlarger deflection would have been measured in the membersthat experienced failure through flexure but the tests wereinterrupted prematurely due to limitations in the capacity ofthe testing equipment and for the sake of safety

52 Shear Figure 15 compares the experimental and analyti-cal load-displacement curves of the shear test specimensTheanalytical results are in relatively good agreement with theexperimental values for the specimens with stirrups Herealso slight difference in the initial slope occurred as explainedabove in Section 51 Specimen S25-05d experienced suddenbrittle failure due to the clear occurrence of shear failureValues near the maximum load could not be measuredbecause of the delay in the acquisition of the data Besides thespecimenswithout stirrup showed smallermaximum loads inthe test than those of the analysis However considering thelarge experimental errors that are generally observed in theshear test of specimens without stirrup the results presentedhere demonstrate to some extent the good execution of thetests performed in this study

Here also the early ending of the tests explains thedifferent maximum deflections of the analytical and experi-mental results The members without stirrup in Figure 15(b)experienced sudden failure but the tests were interruptedprematurely due to limitations in the capacity of the testingequipment and for the sake of safety In addition it isextremely difficult to measure precisely the behavior of themembers without stirrup after the ultimate state when thefailure test is conducted using an actuator and through

displacement control On the other hand the similarity of theexperimental and analytical maximum deflections observedin Figure 15(a) was achieved because the members sufferedshear failure and reached a state close to their ultimate state atthe completion of the tests thanks to the presence of stirrups

6 Conclusions

This study evaluated experimentally and analytically thestructural behavior of reinforced concrete beams made ofAAS concrete The following conclusions can be drawn fromthe results

(1) The elastic modulus and the strain at maximum stressof AAS concrete were slightly smaller than thosepredicted for normal concrete This difference couldbe explained by the reduction in the unit mass ofAAS concrete caused by the smaller density of slagcompared to cement Further study shall proposeadequate models for the elastic modulus and stress-strain relation of AAS concrete

(2) The test results of the flexural members showedthat the ratio of the ultimate load to the yield loadof steel ranged between 115 and 141 and the loadbearing capacity improved with higher tensile steelratio The flexural behavior of the reinforced AASconcrete members appeared thus to be very similarto that of the reinforced concrete beam made ofnormal concrete because the reinforcing bars governthe flexural behavior of the members A nonlinearflexural analysis model was proposed using the elasticmodulus and stress-strain relation of AAS concreteThe analytical resultswere in good agreementwith the

12 Advances in Materials Science and Engineering

experimental results and demonstrated the validity ofthe analytical model

(3) The experimental shear strength obtained for themembers without stirrup was significantly higherthan that predicted by the design code which indi-cated the conservativeness of the design code Theshear behavior of the reinforced AAS concrete mem-bers varied according to the amount of tensile steel

(4) In view of the finite element analysis results reflectingthe nonlinearmodel ofAAS concrete used in previousstudies the flexural and shear behaviors of the AASconcrete specimenswere in relatively good agreementwith those predicted analytically

(5) Consequently the test results show that the flexuraland shear behaviors of the reinforced AAS concretemembers are very similar to those of the reinforcedconcrete beammade of normal concrete and render itpossible to apply conventional design code for flexureand shear in the design of reinforced AAS concretemembers Further studies are required for the practi-cal use of AAS concrete since this experimental studywas limited to specimens with specific dimensions

Conflicts of Interest

The authors declare that they have no conflicts of interest

Acknowledgments

This research was financially supported by the KoreanMinistry of Environment as ldquoPublic Technology ProgramBased on Environmental Policyrdquo (no 2016000700003) Thisresearch was also supported by a grant (Code 11-TechnologyInnovation-F04) from Construction Technology InnovationProgram (CTIP) funded by Ministry of Land and Transportof Korean government

References

[1] S-D Wang X-C Pu K L Scrivener and P L Pratt ldquoAlkali-activated slag cement and concrete a review of properties andproblemsrdquo Advances in Cement Research vol 7 no 27 pp 93ndash102 1995

[2] A Palomo MW Grutzeck andM T Blanco ldquoAlkali-activatedfly ashes a cement for the futurerdquo Cement and ConcreteResearch vol 29 no 8 pp 1323ndash1329 1999

[3] C Shi P V Krivenko and D Roy Alkali-activated cement andconcrete vol 376 Taylor amp Francis Abingdon UK 2006

[4] C Shi A F Jimenez and A Palomo ldquoNew cements for the21st century the pursuit of an alternative to Portland cementrdquoCement and Concrete Research vol 41 no 7 pp 750ndash763 2011

[5] A R Brough and A Atkinson ldquoSodium silicate-basedalkali-activated slag mortars part I Strength hydration andmicrostructurerdquo Cement and Concrete Research vol 32 no 6pp 865ndash879 2002

[6] S Aydin and B Baradan ldquoEffect of activator type and contenton properties of alkali-activated slag mortarsrdquo Composites PartB Engineering vol 57 pp 166ndash172 2014

[7] S H Oh S H Hong and K M Lee ldquoAutogenous shrinkageproperties of high strength alkali activated slag mortarrdquo Journalof the Korean Recycled Construction Resources Institute vol 2no 1 pp 60ndash65 2014

[8] F G Collins and J G Sanjayan ldquoWorkability and mechanicalproperties of alkali activated slag concreterdquo Cement and Con-crete Research vol 29 no 3 pp 455ndash458 1999

[9] M Sofi J S J van Deventer P A Mendis and G CLukey ldquoEngineering properties of inorganic polymer concretes(IPCs)rdquo Cement and Concrete Research vol 37 no 2 pp 251ndash257 2007

[10] C D Atis C Bilim O Celik and O Karahan ldquoInfluenceof activator on the strength and drying shrinkage of alkali-activated slag mortarrdquo Construction and Building Materials vol23 no 1 pp 548ndash555 2009

[11] A A Melo Neto M A Cincotto and W Repette ldquoDrying andautogenous shrinkage of pastes and mortars with activated slagcementrdquo Cement and Concrete Research vol 38 no 4 pp 565ndash574 2008

[12] F PuertasM Palacios andTVazquez ldquoCarbonation process ofalkali-activated slag mortarsrdquo Journal of Materials Science vol41 no 10 pp 3071ndash3082 2006

[13] K Lee and J Seo ldquoEvaluation of flexural behavior of reinforcedconcrete beams using alkali activated slag concreterdquo Journal ofthe Korea Concrete Institute vol 27 no 3 pp 311ndash317 2015

[14] S Choi K Lee and S Yoo ldquoShear behavior of RC beams usingalkali activated slag concreterdquo Journal of the Korean RecycledConstruction Resources Institute vol 3 no 1 pp 58ndash63 2015

[15] T-H Kim K-M Lee C Yoon and H M Shin ldquoInelasticbehavior and ductility capacity of reinforced concrete bridgepiers under earthquake I Theory and formulationrdquo Journal ofStructural Engineering vol 129 no 9 pp 1199ndash1207 2003

[16] E Thorenfeldt A Tomaszewicz and J J Jensen ldquoMechanicalproperties of high strength concrete and application in designrdquoin Proceedings of the Symposium Utilization of High StrengthConcrete T Trondheim Ed vol 40 pp 149ndash159 StravangerNorway 15ndash18 June 1987

[17] S-W Shin S K Ghosh and J Moreno ldquoFlexural ductility ofultra-high-strength concrete membersrdquoACI Structural Journalvol 86 no 4 pp 394ndash400 1989

[18] T-H Kim K-M Lee C Yoon and H M Shin ldquoInelasticbehavior and ductility capacity of reinforced concrete bridgepiers under earthquake II Numerical validationrdquo Journal ofStructural Engineering vol 129 no 9 pp 1208ndash1219 2003

[19] K Maekawa and H Okamura ldquoDeformational behavior andconstitutive equation of concrete using the elasto-plastic andfracture modelrdquo Journal of the Faculty of Engineering Universityof Tokyo Series B vol 37 no 2 pp 253ndash328 1983

Submit your manuscripts athttpswwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CeramicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CompositesJournal of

NanoparticlesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Biomaterials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MetallurgyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

MaterialsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

8 Advances in Materials Science and Engineering

S25-05dS25-0S22-05d

S22-0S19-05dS19-0

0

100

200

300

400

500

600

Load

(kN

)

3 6 9 12 15 180Deflection (mm)

Figure 8 Load-deflection curves of shear test specimens

S25-05dS22-05dS19-05d

0007 0014 0021 0028 00350Strain of tensile steel (mmmm)

0

100

200

300

400

500

600

Load

(kN

)

(a) With stirrups

S25-0S22-0S19-0

0

50

100

150

200

250

Load

(kN

)

0001 0002 0003 00040Strain of tensile steel (mmmm)

(b) Without stirrup

Figure 9 Load versus strain of tensile steel in shear test specimens

for these members In addition the experimental shear forcecorresponds to the sum of the shear force obtained in thetest and the self-weight (135 kN = 25 times 03 times 02 times 182)the shear strength 119881c supported by concrete in the test is halfof the ultimate load of the specimens without stirrup (S25-0S22-0 S19-0) the shear strength 119881c provided by the designcode is the result of the application of (2) and the shearstrength sustained by the stirrups is calculated by applying119881s = 119860v119891y119889119904 where 119904 is the stirrup spacing The values of119881c in ldquoAnalysisrdquo are computed as the product of the principal

stress obtained in Figure 11(b) of Section 32 by the cross-sectional area of the specimen The values of 119881s in ldquoAnalysisrdquoare calculated as the product of the strain in the stirrupobtained in Figure 11(a) of Section 32 by the cross-sectionalarea of the reinforcement

The ratio of the experimental value to the value predictedby the design code (Test(119881u)Code(119881n)) ranges between100 and 127 and that of the experimental value to theanalytic value calculated from the experimental strain(Test(119881u)Analysis(119881n)) ranges between 100 and 126 which

Advances in Materials Science and Engineering 9

S25-05dS22-05dS19-05d

0

100

200

300

400

500

600Lo

ad (k

N)

0001 0002 0003 00040Strain of concrete (mmmm)

(a) With stirrups

S25-0S22-0S19-0

0

50

100

150

200

250

Load

(kN

)

00003 00006 00009 00012 000150Strain of concrete (mmmm)

(b) Without stirrup

Figure 10 Load versus flexural compressive strain of concrete in shear test specimens

S25-05dS22-05dS19-05d

0

100

200

300

400

500

600

Load

(kN

)

0003 0006 0009 0012 00150Shear strain (mmmm)

(a) Stirrups

S22-0S22-0S19-0

0

25

50

75

100

125

150

Load

(kN

)

000003 000006 000009 000012 0000150Shear strain (mmmm)

(b) Concrete

Figure 11 Load versus shear strain in shear test specimens

indicate that the analysis provides values larger by maximum26 and the similarity between the predictions of the designand the analysis

4 Finite Element Analysis

41 Method of Analysis The numerical analysis was carriedout using the nonlinear finite element program RCAHEST

developed by Kim et al [15] The analysis models consist ofa compression tension stiffening and shear transfer modelfor concrete and a model for embedded reinforcing steelThe concrete-reinforcement bond interaction is considered inboth the tension stiffening model for concrete and the modelfor reinforcement An earlier study [18] demonstrated that theabove-mentioned analysis model agreed reasonably with theexperimental data

10 Advances in Materials Science and Engineering

Uncracked

Isotropic Concrete

Reinforcingbar

Cracked

Orthotropic

Tensile

Specific stress-strain(i) Tension-stiffening model

(i) Bilinear model with bond

(ii) Shear transfer model(iii) Reduced compression model

Crackingcriteria

Compressive

model(i) Elastoplastic fracture

(i) Bare bar model

+

Equivalent stress-strain

effect

Figure 12 Outline of analysis model for reinforced high-strength concrete [15]

PredictionAnalysis

0

20

40

60

80

Stre

ss (M

Pa)

0001 0002 0003 0004 0005 00060Strain (mmmm)

Test

Figure 13 Comparison of experimental and predicted stress-straincurves

42 Material Models for Reinforced Concrete The nonlinearstress-strain relation of a reinforced concrete (RC) in-planeelement is formulated based on the concept of space averag-ing on the control volume The cracks and reinforcing barsare idealized as being distributed over the entire elementAlthough the local behavior of the crackedRC is not uniformin practical terms it can be treated as a continuum havingquasi-uniform stress and strain fields in a finite region Thematerial models aim to describe the overall behavior of astructure rather than a specific local behavior at the elementlevel In this paper the term ldquocrackrdquo explicitly refers to themacrocrack perpendicular to the principal tensile direction

According to the cracking criteria the analysis modelsare divided into models before and after the initiation ofcracks as shown in Figure 12Thematerialmodel for concreteprior to cracking is based on the elastoplastic fracture model[19] given in Figure 13 The local coordinate systems ofreinforcing bars are always assigned with respect to each baraxis but those of cracked concrete are determined according

F25-TestF25-AnalysisF22-Test

F22-AnalysisF19-TestF19-Analysis

0

50

100

150

200

250

300

350

Load

(kN

)

10 20 30 40 500Deflection (mm)

Figure 14 Comparison of experimental and analytical load-deflection curves for flexure test members

to the current major crack plane Once a smeared crack isinitiated it is treated as fixed in a direction and anisotropy isintroduced As loading step proceeds the principal directionof the average stress can be changed and the consequent sheartransfer model is involved in the constitutive law

5 Comparison of Experimental andAnalytical Results

51 Flexure Figure 14 compares the experimental and ana-lytical load-displacement curves for specimens F25 F22 andF19 The analytical results are in relatively good agreementwith the experimental values and indicate the validity of theanalytic model However for F25 with the largest tensile ratioconsidered in this study the test specimens exhibit slightbrittle failure compared to the analytical prediction The ini-tial slope of the experimental curves is on the whole smallerthan that of the analytical curves The different initial slopes

Advances in Materials Science and Engineering 11

S25-05d-TestS25-05d-AnalysisS22-05d-Test

S22-05d-AnalysisS19-05d-TestS19-05d-Analysis

0

100

200

300

400

500

600Lo

ad (k

N)

4 8 12 16 200Deflection (mm)

(a) With stirrups

0

100

200

300

400

Load

(kN

)

2 4 6 8 100Deflection (mm)

S25-05d-TestS25-05d-AnalysisS22-05d-Test

S22-05d-AnalysisS19-05d-TestS19-05d-Analysis

(b) Without stirrup

Figure 15 Comparison of experimental and analytical load-displacement curves for shear test members

of the analytical and experimental results can be attributedpartially to the stiffness adopted in the analytical model ofthe members and some experimental error Moreover theearly completion of the tests explains the different maximumdeflections of the analytical and experimental results In factlarger deflection would have been measured in the membersthat experienced failure through flexure but the tests wereinterrupted prematurely due to limitations in the capacity ofthe testing equipment and for the sake of safety

52 Shear Figure 15 compares the experimental and analyti-cal load-displacement curves of the shear test specimensTheanalytical results are in relatively good agreement with theexperimental values for the specimens with stirrups Herealso slight difference in the initial slope occurred as explainedabove in Section 51 Specimen S25-05d experienced suddenbrittle failure due to the clear occurrence of shear failureValues near the maximum load could not be measuredbecause of the delay in the acquisition of the data Besides thespecimenswithout stirrup showed smallermaximum loads inthe test than those of the analysis However considering thelarge experimental errors that are generally observed in theshear test of specimens without stirrup the results presentedhere demonstrate to some extent the good execution of thetests performed in this study

Here also the early ending of the tests explains thedifferent maximum deflections of the analytical and experi-mental results The members without stirrup in Figure 15(b)experienced sudden failure but the tests were interruptedprematurely due to limitations in the capacity of the testingequipment and for the sake of safety In addition it isextremely difficult to measure precisely the behavior of themembers without stirrup after the ultimate state when thefailure test is conducted using an actuator and through

displacement control On the other hand the similarity of theexperimental and analytical maximum deflections observedin Figure 15(a) was achieved because the members sufferedshear failure and reached a state close to their ultimate state atthe completion of the tests thanks to the presence of stirrups

6 Conclusions

This study evaluated experimentally and analytically thestructural behavior of reinforced concrete beams made ofAAS concrete The following conclusions can be drawn fromthe results

(1) The elastic modulus and the strain at maximum stressof AAS concrete were slightly smaller than thosepredicted for normal concrete This difference couldbe explained by the reduction in the unit mass ofAAS concrete caused by the smaller density of slagcompared to cement Further study shall proposeadequate models for the elastic modulus and stress-strain relation of AAS concrete

(2) The test results of the flexural members showedthat the ratio of the ultimate load to the yield loadof steel ranged between 115 and 141 and the loadbearing capacity improved with higher tensile steelratio The flexural behavior of the reinforced AASconcrete members appeared thus to be very similarto that of the reinforced concrete beam made ofnormal concrete because the reinforcing bars governthe flexural behavior of the members A nonlinearflexural analysis model was proposed using the elasticmodulus and stress-strain relation of AAS concreteThe analytical resultswere in good agreementwith the

12 Advances in Materials Science and Engineering

experimental results and demonstrated the validity ofthe analytical model

(3) The experimental shear strength obtained for themembers without stirrup was significantly higherthan that predicted by the design code which indi-cated the conservativeness of the design code Theshear behavior of the reinforced AAS concrete mem-bers varied according to the amount of tensile steel

(4) In view of the finite element analysis results reflectingthe nonlinearmodel ofAAS concrete used in previousstudies the flexural and shear behaviors of the AASconcrete specimenswere in relatively good agreementwith those predicted analytically

(5) Consequently the test results show that the flexuraland shear behaviors of the reinforced AAS concretemembers are very similar to those of the reinforcedconcrete beammade of normal concrete and render itpossible to apply conventional design code for flexureand shear in the design of reinforced AAS concretemembers Further studies are required for the practi-cal use of AAS concrete since this experimental studywas limited to specimens with specific dimensions

Conflicts of Interest

The authors declare that they have no conflicts of interest

Acknowledgments

This research was financially supported by the KoreanMinistry of Environment as ldquoPublic Technology ProgramBased on Environmental Policyrdquo (no 2016000700003) Thisresearch was also supported by a grant (Code 11-TechnologyInnovation-F04) from Construction Technology InnovationProgram (CTIP) funded by Ministry of Land and Transportof Korean government

References

[1] S-D Wang X-C Pu K L Scrivener and P L Pratt ldquoAlkali-activated slag cement and concrete a review of properties andproblemsrdquo Advances in Cement Research vol 7 no 27 pp 93ndash102 1995

[2] A Palomo MW Grutzeck andM T Blanco ldquoAlkali-activatedfly ashes a cement for the futurerdquo Cement and ConcreteResearch vol 29 no 8 pp 1323ndash1329 1999

[3] C Shi P V Krivenko and D Roy Alkali-activated cement andconcrete vol 376 Taylor amp Francis Abingdon UK 2006

[4] C Shi A F Jimenez and A Palomo ldquoNew cements for the21st century the pursuit of an alternative to Portland cementrdquoCement and Concrete Research vol 41 no 7 pp 750ndash763 2011

[5] A R Brough and A Atkinson ldquoSodium silicate-basedalkali-activated slag mortars part I Strength hydration andmicrostructurerdquo Cement and Concrete Research vol 32 no 6pp 865ndash879 2002

[6] S Aydin and B Baradan ldquoEffect of activator type and contenton properties of alkali-activated slag mortarsrdquo Composites PartB Engineering vol 57 pp 166ndash172 2014

[7] S H Oh S H Hong and K M Lee ldquoAutogenous shrinkageproperties of high strength alkali activated slag mortarrdquo Journalof the Korean Recycled Construction Resources Institute vol 2no 1 pp 60ndash65 2014

[8] F G Collins and J G Sanjayan ldquoWorkability and mechanicalproperties of alkali activated slag concreterdquo Cement and Con-crete Research vol 29 no 3 pp 455ndash458 1999

[9] M Sofi J S J van Deventer P A Mendis and G CLukey ldquoEngineering properties of inorganic polymer concretes(IPCs)rdquo Cement and Concrete Research vol 37 no 2 pp 251ndash257 2007

[10] C D Atis C Bilim O Celik and O Karahan ldquoInfluenceof activator on the strength and drying shrinkage of alkali-activated slag mortarrdquo Construction and Building Materials vol23 no 1 pp 548ndash555 2009

[11] A A Melo Neto M A Cincotto and W Repette ldquoDrying andautogenous shrinkage of pastes and mortars with activated slagcementrdquo Cement and Concrete Research vol 38 no 4 pp 565ndash574 2008

[12] F PuertasM Palacios andTVazquez ldquoCarbonation process ofalkali-activated slag mortarsrdquo Journal of Materials Science vol41 no 10 pp 3071ndash3082 2006

[13] K Lee and J Seo ldquoEvaluation of flexural behavior of reinforcedconcrete beams using alkali activated slag concreterdquo Journal ofthe Korea Concrete Institute vol 27 no 3 pp 311ndash317 2015

[14] S Choi K Lee and S Yoo ldquoShear behavior of RC beams usingalkali activated slag concreterdquo Journal of the Korean RecycledConstruction Resources Institute vol 3 no 1 pp 58ndash63 2015

[15] T-H Kim K-M Lee C Yoon and H M Shin ldquoInelasticbehavior and ductility capacity of reinforced concrete bridgepiers under earthquake I Theory and formulationrdquo Journal ofStructural Engineering vol 129 no 9 pp 1199ndash1207 2003

[16] E Thorenfeldt A Tomaszewicz and J J Jensen ldquoMechanicalproperties of high strength concrete and application in designrdquoin Proceedings of the Symposium Utilization of High StrengthConcrete T Trondheim Ed vol 40 pp 149ndash159 StravangerNorway 15ndash18 June 1987

[17] S-W Shin S K Ghosh and J Moreno ldquoFlexural ductility ofultra-high-strength concrete membersrdquoACI Structural Journalvol 86 no 4 pp 394ndash400 1989

[18] T-H Kim K-M Lee C Yoon and H M Shin ldquoInelasticbehavior and ductility capacity of reinforced concrete bridgepiers under earthquake II Numerical validationrdquo Journal ofStructural Engineering vol 129 no 9 pp 1208ndash1219 2003

[19] K Maekawa and H Okamura ldquoDeformational behavior andconstitutive equation of concrete using the elasto-plastic andfracture modelrdquo Journal of the Faculty of Engineering Universityof Tokyo Series B vol 37 no 2 pp 253ndash328 1983

Submit your manuscripts athttpswwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CeramicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CompositesJournal of

NanoparticlesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Biomaterials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MetallurgyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

MaterialsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in Materials Science and Engineering 9

S25-05dS22-05dS19-05d

0

100

200

300

400

500

600Lo

ad (k

N)

0001 0002 0003 00040Strain of concrete (mmmm)

(a) With stirrups

S25-0S22-0S19-0

0

50

100

150

200

250

Load

(kN

)

00003 00006 00009 00012 000150Strain of concrete (mmmm)

(b) Without stirrup

Figure 10 Load versus flexural compressive strain of concrete in shear test specimens

S25-05dS22-05dS19-05d

0

100

200

300

400

500

600

Load

(kN

)

0003 0006 0009 0012 00150Shear strain (mmmm)

(a) Stirrups

S22-0S22-0S19-0

0

25

50

75

100

125

150

Load

(kN

)

000003 000006 000009 000012 0000150Shear strain (mmmm)

(b) Concrete

Figure 11 Load versus shear strain in shear test specimens

indicate that the analysis provides values larger by maximum26 and the similarity between the predictions of the designand the analysis

4 Finite Element Analysis

41 Method of Analysis The numerical analysis was carriedout using the nonlinear finite element program RCAHEST

developed by Kim et al [15] The analysis models consist ofa compression tension stiffening and shear transfer modelfor concrete and a model for embedded reinforcing steelThe concrete-reinforcement bond interaction is considered inboth the tension stiffening model for concrete and the modelfor reinforcement An earlier study [18] demonstrated that theabove-mentioned analysis model agreed reasonably with theexperimental data

10 Advances in Materials Science and Engineering

Uncracked

Isotropic Concrete

Reinforcingbar

Cracked

Orthotropic

Tensile

Specific stress-strain(i) Tension-stiffening model

(i) Bilinear model with bond

(ii) Shear transfer model(iii) Reduced compression model

Crackingcriteria

Compressive

model(i) Elastoplastic fracture

(i) Bare bar model

+

Equivalent stress-strain

effect

Figure 12 Outline of analysis model for reinforced high-strength concrete [15]

PredictionAnalysis

0

20

40

60

80

Stre

ss (M

Pa)

0001 0002 0003 0004 0005 00060Strain (mmmm)

Test

Figure 13 Comparison of experimental and predicted stress-straincurves

42 Material Models for Reinforced Concrete The nonlinearstress-strain relation of a reinforced concrete (RC) in-planeelement is formulated based on the concept of space averag-ing on the control volume The cracks and reinforcing barsare idealized as being distributed over the entire elementAlthough the local behavior of the crackedRC is not uniformin practical terms it can be treated as a continuum havingquasi-uniform stress and strain fields in a finite region Thematerial models aim to describe the overall behavior of astructure rather than a specific local behavior at the elementlevel In this paper the term ldquocrackrdquo explicitly refers to themacrocrack perpendicular to the principal tensile direction

According to the cracking criteria the analysis modelsare divided into models before and after the initiation ofcracks as shown in Figure 12Thematerialmodel for concreteprior to cracking is based on the elastoplastic fracture model[19] given in Figure 13 The local coordinate systems ofreinforcing bars are always assigned with respect to each baraxis but those of cracked concrete are determined according

F25-TestF25-AnalysisF22-Test

F22-AnalysisF19-TestF19-Analysis

0

50

100

150

200

250

300

350

Load

(kN

)

10 20 30 40 500Deflection (mm)

Figure 14 Comparison of experimental and analytical load-deflection curves for flexure test members

to the current major crack plane Once a smeared crack isinitiated it is treated as fixed in a direction and anisotropy isintroduced As loading step proceeds the principal directionof the average stress can be changed and the consequent sheartransfer model is involved in the constitutive law

5 Comparison of Experimental andAnalytical Results

51 Flexure Figure 14 compares the experimental and ana-lytical load-displacement curves for specimens F25 F22 andF19 The analytical results are in relatively good agreementwith the experimental values and indicate the validity of theanalytic model However for F25 with the largest tensile ratioconsidered in this study the test specimens exhibit slightbrittle failure compared to the analytical prediction The ini-tial slope of the experimental curves is on the whole smallerthan that of the analytical curves The different initial slopes

Advances in Materials Science and Engineering 11

S25-05d-TestS25-05d-AnalysisS22-05d-Test

S22-05d-AnalysisS19-05d-TestS19-05d-Analysis

0

100

200

300

400

500

600Lo

ad (k

N)

4 8 12 16 200Deflection (mm)

(a) With stirrups

0

100

200

300

400

Load

(kN

)

2 4 6 8 100Deflection (mm)

S25-05d-TestS25-05d-AnalysisS22-05d-Test

S22-05d-AnalysisS19-05d-TestS19-05d-Analysis

(b) Without stirrup

Figure 15 Comparison of experimental and analytical load-displacement curves for shear test members

of the analytical and experimental results can be attributedpartially to the stiffness adopted in the analytical model ofthe members and some experimental error Moreover theearly completion of the tests explains the different maximumdeflections of the analytical and experimental results In factlarger deflection would have been measured in the membersthat experienced failure through flexure but the tests wereinterrupted prematurely due to limitations in the capacity ofthe testing equipment and for the sake of safety

52 Shear Figure 15 compares the experimental and analyti-cal load-displacement curves of the shear test specimensTheanalytical results are in relatively good agreement with theexperimental values for the specimens with stirrups Herealso slight difference in the initial slope occurred as explainedabove in Section 51 Specimen S25-05d experienced suddenbrittle failure due to the clear occurrence of shear failureValues near the maximum load could not be measuredbecause of the delay in the acquisition of the data Besides thespecimenswithout stirrup showed smallermaximum loads inthe test than those of the analysis However considering thelarge experimental errors that are generally observed in theshear test of specimens without stirrup the results presentedhere demonstrate to some extent the good execution of thetests performed in this study

Here also the early ending of the tests explains thedifferent maximum deflections of the analytical and experi-mental results The members without stirrup in Figure 15(b)experienced sudden failure but the tests were interruptedprematurely due to limitations in the capacity of the testingequipment and for the sake of safety In addition it isextremely difficult to measure precisely the behavior of themembers without stirrup after the ultimate state when thefailure test is conducted using an actuator and through

displacement control On the other hand the similarity of theexperimental and analytical maximum deflections observedin Figure 15(a) was achieved because the members sufferedshear failure and reached a state close to their ultimate state atthe completion of the tests thanks to the presence of stirrups

6 Conclusions

This study evaluated experimentally and analytically thestructural behavior of reinforced concrete beams made ofAAS concrete The following conclusions can be drawn fromthe results

(1) The elastic modulus and the strain at maximum stressof AAS concrete were slightly smaller than thosepredicted for normal concrete This difference couldbe explained by the reduction in the unit mass ofAAS concrete caused by the smaller density of slagcompared to cement Further study shall proposeadequate models for the elastic modulus and stress-strain relation of AAS concrete

(2) The test results of the flexural members showedthat the ratio of the ultimate load to the yield loadof steel ranged between 115 and 141 and the loadbearing capacity improved with higher tensile steelratio The flexural behavior of the reinforced AASconcrete members appeared thus to be very similarto that of the reinforced concrete beam made ofnormal concrete because the reinforcing bars governthe flexural behavior of the members A nonlinearflexural analysis model was proposed using the elasticmodulus and stress-strain relation of AAS concreteThe analytical resultswere in good agreementwith the

12 Advances in Materials Science and Engineering

experimental results and demonstrated the validity ofthe analytical model

(3) The experimental shear strength obtained for themembers without stirrup was significantly higherthan that predicted by the design code which indi-cated the conservativeness of the design code Theshear behavior of the reinforced AAS concrete mem-bers varied according to the amount of tensile steel

(4) In view of the finite element analysis results reflectingthe nonlinearmodel ofAAS concrete used in previousstudies the flexural and shear behaviors of the AASconcrete specimenswere in relatively good agreementwith those predicted analytically

(5) Consequently the test results show that the flexuraland shear behaviors of the reinforced AAS concretemembers are very similar to those of the reinforcedconcrete beammade of normal concrete and render itpossible to apply conventional design code for flexureand shear in the design of reinforced AAS concretemembers Further studies are required for the practi-cal use of AAS concrete since this experimental studywas limited to specimens with specific dimensions

Conflicts of Interest

The authors declare that they have no conflicts of interest

Acknowledgments

This research was financially supported by the KoreanMinistry of Environment as ldquoPublic Technology ProgramBased on Environmental Policyrdquo (no 2016000700003) Thisresearch was also supported by a grant (Code 11-TechnologyInnovation-F04) from Construction Technology InnovationProgram (CTIP) funded by Ministry of Land and Transportof Korean government

References

[1] S-D Wang X-C Pu K L Scrivener and P L Pratt ldquoAlkali-activated slag cement and concrete a review of properties andproblemsrdquo Advances in Cement Research vol 7 no 27 pp 93ndash102 1995

[2] A Palomo MW Grutzeck andM T Blanco ldquoAlkali-activatedfly ashes a cement for the futurerdquo Cement and ConcreteResearch vol 29 no 8 pp 1323ndash1329 1999

[3] C Shi P V Krivenko and D Roy Alkali-activated cement andconcrete vol 376 Taylor amp Francis Abingdon UK 2006

[4] C Shi A F Jimenez and A Palomo ldquoNew cements for the21st century the pursuit of an alternative to Portland cementrdquoCement and Concrete Research vol 41 no 7 pp 750ndash763 2011

[5] A R Brough and A Atkinson ldquoSodium silicate-basedalkali-activated slag mortars part I Strength hydration andmicrostructurerdquo Cement and Concrete Research vol 32 no 6pp 865ndash879 2002

[6] S Aydin and B Baradan ldquoEffect of activator type and contenton properties of alkali-activated slag mortarsrdquo Composites PartB Engineering vol 57 pp 166ndash172 2014

[7] S H Oh S H Hong and K M Lee ldquoAutogenous shrinkageproperties of high strength alkali activated slag mortarrdquo Journalof the Korean Recycled Construction Resources Institute vol 2no 1 pp 60ndash65 2014

[8] F G Collins and J G Sanjayan ldquoWorkability and mechanicalproperties of alkali activated slag concreterdquo Cement and Con-crete Research vol 29 no 3 pp 455ndash458 1999

[9] M Sofi J S J van Deventer P A Mendis and G CLukey ldquoEngineering properties of inorganic polymer concretes(IPCs)rdquo Cement and Concrete Research vol 37 no 2 pp 251ndash257 2007

[10] C D Atis C Bilim O Celik and O Karahan ldquoInfluenceof activator on the strength and drying shrinkage of alkali-activated slag mortarrdquo Construction and Building Materials vol23 no 1 pp 548ndash555 2009

[11] A A Melo Neto M A Cincotto and W Repette ldquoDrying andautogenous shrinkage of pastes and mortars with activated slagcementrdquo Cement and Concrete Research vol 38 no 4 pp 565ndash574 2008

[12] F PuertasM Palacios andTVazquez ldquoCarbonation process ofalkali-activated slag mortarsrdquo Journal of Materials Science vol41 no 10 pp 3071ndash3082 2006

[13] K Lee and J Seo ldquoEvaluation of flexural behavior of reinforcedconcrete beams using alkali activated slag concreterdquo Journal ofthe Korea Concrete Institute vol 27 no 3 pp 311ndash317 2015

[14] S Choi K Lee and S Yoo ldquoShear behavior of RC beams usingalkali activated slag concreterdquo Journal of the Korean RecycledConstruction Resources Institute vol 3 no 1 pp 58ndash63 2015

[15] T-H Kim K-M Lee C Yoon and H M Shin ldquoInelasticbehavior and ductility capacity of reinforced concrete bridgepiers under earthquake I Theory and formulationrdquo Journal ofStructural Engineering vol 129 no 9 pp 1199ndash1207 2003

[16] E Thorenfeldt A Tomaszewicz and J J Jensen ldquoMechanicalproperties of high strength concrete and application in designrdquoin Proceedings of the Symposium Utilization of High StrengthConcrete T Trondheim Ed vol 40 pp 149ndash159 StravangerNorway 15ndash18 June 1987

[17] S-W Shin S K Ghosh and J Moreno ldquoFlexural ductility ofultra-high-strength concrete membersrdquoACI Structural Journalvol 86 no 4 pp 394ndash400 1989

[18] T-H Kim K-M Lee C Yoon and H M Shin ldquoInelasticbehavior and ductility capacity of reinforced concrete bridgepiers under earthquake II Numerical validationrdquo Journal ofStructural Engineering vol 129 no 9 pp 1208ndash1219 2003

[19] K Maekawa and H Okamura ldquoDeformational behavior andconstitutive equation of concrete using the elasto-plastic andfracture modelrdquo Journal of the Faculty of Engineering Universityof Tokyo Series B vol 37 no 2 pp 253ndash328 1983

Submit your manuscripts athttpswwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CeramicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CompositesJournal of

NanoparticlesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Biomaterials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MetallurgyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

MaterialsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

10 Advances in Materials Science and Engineering

Uncracked

Isotropic Concrete

Reinforcingbar

Cracked

Orthotropic

Tensile

Specific stress-strain(i) Tension-stiffening model

(i) Bilinear model with bond

(ii) Shear transfer model(iii) Reduced compression model

Crackingcriteria

Compressive

model(i) Elastoplastic fracture

(i) Bare bar model

+

Equivalent stress-strain

effect

Figure 12 Outline of analysis model for reinforced high-strength concrete [15]

PredictionAnalysis

0

20

40

60

80

Stre

ss (M

Pa)

0001 0002 0003 0004 0005 00060Strain (mmmm)

Test

Figure 13 Comparison of experimental and predicted stress-straincurves

42 Material Models for Reinforced Concrete The nonlinearstress-strain relation of a reinforced concrete (RC) in-planeelement is formulated based on the concept of space averag-ing on the control volume The cracks and reinforcing barsare idealized as being distributed over the entire elementAlthough the local behavior of the crackedRC is not uniformin practical terms it can be treated as a continuum havingquasi-uniform stress and strain fields in a finite region Thematerial models aim to describe the overall behavior of astructure rather than a specific local behavior at the elementlevel In this paper the term ldquocrackrdquo explicitly refers to themacrocrack perpendicular to the principal tensile direction

According to the cracking criteria the analysis modelsare divided into models before and after the initiation ofcracks as shown in Figure 12Thematerialmodel for concreteprior to cracking is based on the elastoplastic fracture model[19] given in Figure 13 The local coordinate systems ofreinforcing bars are always assigned with respect to each baraxis but those of cracked concrete are determined according

F25-TestF25-AnalysisF22-Test

F22-AnalysisF19-TestF19-Analysis

0

50

100

150

200

250

300

350

Load

(kN

)

10 20 30 40 500Deflection (mm)

Figure 14 Comparison of experimental and analytical load-deflection curves for flexure test members

to the current major crack plane Once a smeared crack isinitiated it is treated as fixed in a direction and anisotropy isintroduced As loading step proceeds the principal directionof the average stress can be changed and the consequent sheartransfer model is involved in the constitutive law

5 Comparison of Experimental andAnalytical Results

51 Flexure Figure 14 compares the experimental and ana-lytical load-displacement curves for specimens F25 F22 andF19 The analytical results are in relatively good agreementwith the experimental values and indicate the validity of theanalytic model However for F25 with the largest tensile ratioconsidered in this study the test specimens exhibit slightbrittle failure compared to the analytical prediction The ini-tial slope of the experimental curves is on the whole smallerthan that of the analytical curves The different initial slopes

Advances in Materials Science and Engineering 11

S25-05d-TestS25-05d-AnalysisS22-05d-Test

S22-05d-AnalysisS19-05d-TestS19-05d-Analysis

0

100

200

300

400

500

600Lo

ad (k

N)

4 8 12 16 200Deflection (mm)

(a) With stirrups

0

100

200

300

400

Load

(kN

)

2 4 6 8 100Deflection (mm)

S25-05d-TestS25-05d-AnalysisS22-05d-Test

S22-05d-AnalysisS19-05d-TestS19-05d-Analysis

(b) Without stirrup

Figure 15 Comparison of experimental and analytical load-displacement curves for shear test members

of the analytical and experimental results can be attributedpartially to the stiffness adopted in the analytical model ofthe members and some experimental error Moreover theearly completion of the tests explains the different maximumdeflections of the analytical and experimental results In factlarger deflection would have been measured in the membersthat experienced failure through flexure but the tests wereinterrupted prematurely due to limitations in the capacity ofthe testing equipment and for the sake of safety

52 Shear Figure 15 compares the experimental and analyti-cal load-displacement curves of the shear test specimensTheanalytical results are in relatively good agreement with theexperimental values for the specimens with stirrups Herealso slight difference in the initial slope occurred as explainedabove in Section 51 Specimen S25-05d experienced suddenbrittle failure due to the clear occurrence of shear failureValues near the maximum load could not be measuredbecause of the delay in the acquisition of the data Besides thespecimenswithout stirrup showed smallermaximum loads inthe test than those of the analysis However considering thelarge experimental errors that are generally observed in theshear test of specimens without stirrup the results presentedhere demonstrate to some extent the good execution of thetests performed in this study

Here also the early ending of the tests explains thedifferent maximum deflections of the analytical and experi-mental results The members without stirrup in Figure 15(b)experienced sudden failure but the tests were interruptedprematurely due to limitations in the capacity of the testingequipment and for the sake of safety In addition it isextremely difficult to measure precisely the behavior of themembers without stirrup after the ultimate state when thefailure test is conducted using an actuator and through

displacement control On the other hand the similarity of theexperimental and analytical maximum deflections observedin Figure 15(a) was achieved because the members sufferedshear failure and reached a state close to their ultimate state atthe completion of the tests thanks to the presence of stirrups

6 Conclusions

This study evaluated experimentally and analytically thestructural behavior of reinforced concrete beams made ofAAS concrete The following conclusions can be drawn fromthe results

(1) The elastic modulus and the strain at maximum stressof AAS concrete were slightly smaller than thosepredicted for normal concrete This difference couldbe explained by the reduction in the unit mass ofAAS concrete caused by the smaller density of slagcompared to cement Further study shall proposeadequate models for the elastic modulus and stress-strain relation of AAS concrete

(2) The test results of the flexural members showedthat the ratio of the ultimate load to the yield loadof steel ranged between 115 and 141 and the loadbearing capacity improved with higher tensile steelratio The flexural behavior of the reinforced AASconcrete members appeared thus to be very similarto that of the reinforced concrete beam made ofnormal concrete because the reinforcing bars governthe flexural behavior of the members A nonlinearflexural analysis model was proposed using the elasticmodulus and stress-strain relation of AAS concreteThe analytical resultswere in good agreementwith the

12 Advances in Materials Science and Engineering

experimental results and demonstrated the validity ofthe analytical model

(3) The experimental shear strength obtained for themembers without stirrup was significantly higherthan that predicted by the design code which indi-cated the conservativeness of the design code Theshear behavior of the reinforced AAS concrete mem-bers varied according to the amount of tensile steel

(4) In view of the finite element analysis results reflectingthe nonlinearmodel ofAAS concrete used in previousstudies the flexural and shear behaviors of the AASconcrete specimenswere in relatively good agreementwith those predicted analytically

(5) Consequently the test results show that the flexuraland shear behaviors of the reinforced AAS concretemembers are very similar to those of the reinforcedconcrete beammade of normal concrete and render itpossible to apply conventional design code for flexureand shear in the design of reinforced AAS concretemembers Further studies are required for the practi-cal use of AAS concrete since this experimental studywas limited to specimens with specific dimensions

Conflicts of Interest

The authors declare that they have no conflicts of interest

Acknowledgments

This research was financially supported by the KoreanMinistry of Environment as ldquoPublic Technology ProgramBased on Environmental Policyrdquo (no 2016000700003) Thisresearch was also supported by a grant (Code 11-TechnologyInnovation-F04) from Construction Technology InnovationProgram (CTIP) funded by Ministry of Land and Transportof Korean government

References

[1] S-D Wang X-C Pu K L Scrivener and P L Pratt ldquoAlkali-activated slag cement and concrete a review of properties andproblemsrdquo Advances in Cement Research vol 7 no 27 pp 93ndash102 1995

[2] A Palomo MW Grutzeck andM T Blanco ldquoAlkali-activatedfly ashes a cement for the futurerdquo Cement and ConcreteResearch vol 29 no 8 pp 1323ndash1329 1999

[3] C Shi P V Krivenko and D Roy Alkali-activated cement andconcrete vol 376 Taylor amp Francis Abingdon UK 2006

[4] C Shi A F Jimenez and A Palomo ldquoNew cements for the21st century the pursuit of an alternative to Portland cementrdquoCement and Concrete Research vol 41 no 7 pp 750ndash763 2011

[5] A R Brough and A Atkinson ldquoSodium silicate-basedalkali-activated slag mortars part I Strength hydration andmicrostructurerdquo Cement and Concrete Research vol 32 no 6pp 865ndash879 2002

[6] S Aydin and B Baradan ldquoEffect of activator type and contenton properties of alkali-activated slag mortarsrdquo Composites PartB Engineering vol 57 pp 166ndash172 2014

[7] S H Oh S H Hong and K M Lee ldquoAutogenous shrinkageproperties of high strength alkali activated slag mortarrdquo Journalof the Korean Recycled Construction Resources Institute vol 2no 1 pp 60ndash65 2014

[8] F G Collins and J G Sanjayan ldquoWorkability and mechanicalproperties of alkali activated slag concreterdquo Cement and Con-crete Research vol 29 no 3 pp 455ndash458 1999

[9] M Sofi J S J van Deventer P A Mendis and G CLukey ldquoEngineering properties of inorganic polymer concretes(IPCs)rdquo Cement and Concrete Research vol 37 no 2 pp 251ndash257 2007

[10] C D Atis C Bilim O Celik and O Karahan ldquoInfluenceof activator on the strength and drying shrinkage of alkali-activated slag mortarrdquo Construction and Building Materials vol23 no 1 pp 548ndash555 2009

[11] A A Melo Neto M A Cincotto and W Repette ldquoDrying andautogenous shrinkage of pastes and mortars with activated slagcementrdquo Cement and Concrete Research vol 38 no 4 pp 565ndash574 2008

[12] F PuertasM Palacios andTVazquez ldquoCarbonation process ofalkali-activated slag mortarsrdquo Journal of Materials Science vol41 no 10 pp 3071ndash3082 2006

[13] K Lee and J Seo ldquoEvaluation of flexural behavior of reinforcedconcrete beams using alkali activated slag concreterdquo Journal ofthe Korea Concrete Institute vol 27 no 3 pp 311ndash317 2015

[14] S Choi K Lee and S Yoo ldquoShear behavior of RC beams usingalkali activated slag concreterdquo Journal of the Korean RecycledConstruction Resources Institute vol 3 no 1 pp 58ndash63 2015

[15] T-H Kim K-M Lee C Yoon and H M Shin ldquoInelasticbehavior and ductility capacity of reinforced concrete bridgepiers under earthquake I Theory and formulationrdquo Journal ofStructural Engineering vol 129 no 9 pp 1199ndash1207 2003

[16] E Thorenfeldt A Tomaszewicz and J J Jensen ldquoMechanicalproperties of high strength concrete and application in designrdquoin Proceedings of the Symposium Utilization of High StrengthConcrete T Trondheim Ed vol 40 pp 149ndash159 StravangerNorway 15ndash18 June 1987

[17] S-W Shin S K Ghosh and J Moreno ldquoFlexural ductility ofultra-high-strength concrete membersrdquoACI Structural Journalvol 86 no 4 pp 394ndash400 1989

[18] T-H Kim K-M Lee C Yoon and H M Shin ldquoInelasticbehavior and ductility capacity of reinforced concrete bridgepiers under earthquake II Numerical validationrdquo Journal ofStructural Engineering vol 129 no 9 pp 1208ndash1219 2003

[19] K Maekawa and H Okamura ldquoDeformational behavior andconstitutive equation of concrete using the elasto-plastic andfracture modelrdquo Journal of the Faculty of Engineering Universityof Tokyo Series B vol 37 no 2 pp 253ndash328 1983

Submit your manuscripts athttpswwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CeramicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CompositesJournal of

NanoparticlesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Biomaterials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MetallurgyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

MaterialsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in Materials Science and Engineering 11

S25-05d-TestS25-05d-AnalysisS22-05d-Test

S22-05d-AnalysisS19-05d-TestS19-05d-Analysis

0

100

200

300

400

500

600Lo

ad (k

N)

4 8 12 16 200Deflection (mm)

(a) With stirrups

0

100

200

300

400

Load

(kN

)

2 4 6 8 100Deflection (mm)

S25-05d-TestS25-05d-AnalysisS22-05d-Test

S22-05d-AnalysisS19-05d-TestS19-05d-Analysis

(b) Without stirrup

Figure 15 Comparison of experimental and analytical load-displacement curves for shear test members

of the analytical and experimental results can be attributedpartially to the stiffness adopted in the analytical model ofthe members and some experimental error Moreover theearly completion of the tests explains the different maximumdeflections of the analytical and experimental results In factlarger deflection would have been measured in the membersthat experienced failure through flexure but the tests wereinterrupted prematurely due to limitations in the capacity ofthe testing equipment and for the sake of safety

52 Shear Figure 15 compares the experimental and analyti-cal load-displacement curves of the shear test specimensTheanalytical results are in relatively good agreement with theexperimental values for the specimens with stirrups Herealso slight difference in the initial slope occurred as explainedabove in Section 51 Specimen S25-05d experienced suddenbrittle failure due to the clear occurrence of shear failureValues near the maximum load could not be measuredbecause of the delay in the acquisition of the data Besides thespecimenswithout stirrup showed smallermaximum loads inthe test than those of the analysis However considering thelarge experimental errors that are generally observed in theshear test of specimens without stirrup the results presentedhere demonstrate to some extent the good execution of thetests performed in this study

Here also the early ending of the tests explains thedifferent maximum deflections of the analytical and experi-mental results The members without stirrup in Figure 15(b)experienced sudden failure but the tests were interruptedprematurely due to limitations in the capacity of the testingequipment and for the sake of safety In addition it isextremely difficult to measure precisely the behavior of themembers without stirrup after the ultimate state when thefailure test is conducted using an actuator and through

displacement control On the other hand the similarity of theexperimental and analytical maximum deflections observedin Figure 15(a) was achieved because the members sufferedshear failure and reached a state close to their ultimate state atthe completion of the tests thanks to the presence of stirrups

6 Conclusions

This study evaluated experimentally and analytically thestructural behavior of reinforced concrete beams made ofAAS concrete The following conclusions can be drawn fromthe results

(1) The elastic modulus and the strain at maximum stressof AAS concrete were slightly smaller than thosepredicted for normal concrete This difference couldbe explained by the reduction in the unit mass ofAAS concrete caused by the smaller density of slagcompared to cement Further study shall proposeadequate models for the elastic modulus and stress-strain relation of AAS concrete

(2) The test results of the flexural members showedthat the ratio of the ultimate load to the yield loadof steel ranged between 115 and 141 and the loadbearing capacity improved with higher tensile steelratio The flexural behavior of the reinforced AASconcrete members appeared thus to be very similarto that of the reinforced concrete beam made ofnormal concrete because the reinforcing bars governthe flexural behavior of the members A nonlinearflexural analysis model was proposed using the elasticmodulus and stress-strain relation of AAS concreteThe analytical resultswere in good agreementwith the

12 Advances in Materials Science and Engineering

experimental results and demonstrated the validity ofthe analytical model

(3) The experimental shear strength obtained for themembers without stirrup was significantly higherthan that predicted by the design code which indi-cated the conservativeness of the design code Theshear behavior of the reinforced AAS concrete mem-bers varied according to the amount of tensile steel

(4) In view of the finite element analysis results reflectingthe nonlinearmodel ofAAS concrete used in previousstudies the flexural and shear behaviors of the AASconcrete specimenswere in relatively good agreementwith those predicted analytically

(5) Consequently the test results show that the flexuraland shear behaviors of the reinforced AAS concretemembers are very similar to those of the reinforcedconcrete beammade of normal concrete and render itpossible to apply conventional design code for flexureand shear in the design of reinforced AAS concretemembers Further studies are required for the practi-cal use of AAS concrete since this experimental studywas limited to specimens with specific dimensions

Conflicts of Interest

The authors declare that they have no conflicts of interest

Acknowledgments

This research was financially supported by the KoreanMinistry of Environment as ldquoPublic Technology ProgramBased on Environmental Policyrdquo (no 2016000700003) Thisresearch was also supported by a grant (Code 11-TechnologyInnovation-F04) from Construction Technology InnovationProgram (CTIP) funded by Ministry of Land and Transportof Korean government

References

[1] S-D Wang X-C Pu K L Scrivener and P L Pratt ldquoAlkali-activated slag cement and concrete a review of properties andproblemsrdquo Advances in Cement Research vol 7 no 27 pp 93ndash102 1995

[2] A Palomo MW Grutzeck andM T Blanco ldquoAlkali-activatedfly ashes a cement for the futurerdquo Cement and ConcreteResearch vol 29 no 8 pp 1323ndash1329 1999

[3] C Shi P V Krivenko and D Roy Alkali-activated cement andconcrete vol 376 Taylor amp Francis Abingdon UK 2006

[4] C Shi A F Jimenez and A Palomo ldquoNew cements for the21st century the pursuit of an alternative to Portland cementrdquoCement and Concrete Research vol 41 no 7 pp 750ndash763 2011

[5] A R Brough and A Atkinson ldquoSodium silicate-basedalkali-activated slag mortars part I Strength hydration andmicrostructurerdquo Cement and Concrete Research vol 32 no 6pp 865ndash879 2002

[6] S Aydin and B Baradan ldquoEffect of activator type and contenton properties of alkali-activated slag mortarsrdquo Composites PartB Engineering vol 57 pp 166ndash172 2014

[7] S H Oh S H Hong and K M Lee ldquoAutogenous shrinkageproperties of high strength alkali activated slag mortarrdquo Journalof the Korean Recycled Construction Resources Institute vol 2no 1 pp 60ndash65 2014

[8] F G Collins and J G Sanjayan ldquoWorkability and mechanicalproperties of alkali activated slag concreterdquo Cement and Con-crete Research vol 29 no 3 pp 455ndash458 1999

[9] M Sofi J S J van Deventer P A Mendis and G CLukey ldquoEngineering properties of inorganic polymer concretes(IPCs)rdquo Cement and Concrete Research vol 37 no 2 pp 251ndash257 2007

[10] C D Atis C Bilim O Celik and O Karahan ldquoInfluenceof activator on the strength and drying shrinkage of alkali-activated slag mortarrdquo Construction and Building Materials vol23 no 1 pp 548ndash555 2009

[11] A A Melo Neto M A Cincotto and W Repette ldquoDrying andautogenous shrinkage of pastes and mortars with activated slagcementrdquo Cement and Concrete Research vol 38 no 4 pp 565ndash574 2008

[12] F PuertasM Palacios andTVazquez ldquoCarbonation process ofalkali-activated slag mortarsrdquo Journal of Materials Science vol41 no 10 pp 3071ndash3082 2006

[13] K Lee and J Seo ldquoEvaluation of flexural behavior of reinforcedconcrete beams using alkali activated slag concreterdquo Journal ofthe Korea Concrete Institute vol 27 no 3 pp 311ndash317 2015

[14] S Choi K Lee and S Yoo ldquoShear behavior of RC beams usingalkali activated slag concreterdquo Journal of the Korean RecycledConstruction Resources Institute vol 3 no 1 pp 58ndash63 2015

[15] T-H Kim K-M Lee C Yoon and H M Shin ldquoInelasticbehavior and ductility capacity of reinforced concrete bridgepiers under earthquake I Theory and formulationrdquo Journal ofStructural Engineering vol 129 no 9 pp 1199ndash1207 2003

[16] E Thorenfeldt A Tomaszewicz and J J Jensen ldquoMechanicalproperties of high strength concrete and application in designrdquoin Proceedings of the Symposium Utilization of High StrengthConcrete T Trondheim Ed vol 40 pp 149ndash159 StravangerNorway 15ndash18 June 1987

[17] S-W Shin S K Ghosh and J Moreno ldquoFlexural ductility ofultra-high-strength concrete membersrdquoACI Structural Journalvol 86 no 4 pp 394ndash400 1989

[18] T-H Kim K-M Lee C Yoon and H M Shin ldquoInelasticbehavior and ductility capacity of reinforced concrete bridgepiers under earthquake II Numerical validationrdquo Journal ofStructural Engineering vol 129 no 9 pp 1208ndash1219 2003

[19] K Maekawa and H Okamura ldquoDeformational behavior andconstitutive equation of concrete using the elasto-plastic andfracture modelrdquo Journal of the Faculty of Engineering Universityof Tokyo Series B vol 37 no 2 pp 253ndash328 1983

Submit your manuscripts athttpswwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CeramicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CompositesJournal of

NanoparticlesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Biomaterials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MetallurgyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

MaterialsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

12 Advances in Materials Science and Engineering

experimental results and demonstrated the validity ofthe analytical model

(3) The experimental shear strength obtained for themembers without stirrup was significantly higherthan that predicted by the design code which indi-cated the conservativeness of the design code Theshear behavior of the reinforced AAS concrete mem-bers varied according to the amount of tensile steel

(4) In view of the finite element analysis results reflectingthe nonlinearmodel ofAAS concrete used in previousstudies the flexural and shear behaviors of the AASconcrete specimenswere in relatively good agreementwith those predicted analytically

(5) Consequently the test results show that the flexuraland shear behaviors of the reinforced AAS concretemembers are very similar to those of the reinforcedconcrete beammade of normal concrete and render itpossible to apply conventional design code for flexureand shear in the design of reinforced AAS concretemembers Further studies are required for the practi-cal use of AAS concrete since this experimental studywas limited to specimens with specific dimensions

Conflicts of Interest

The authors declare that they have no conflicts of interest

Acknowledgments

This research was financially supported by the KoreanMinistry of Environment as ldquoPublic Technology ProgramBased on Environmental Policyrdquo (no 2016000700003) Thisresearch was also supported by a grant (Code 11-TechnologyInnovation-F04) from Construction Technology InnovationProgram (CTIP) funded by Ministry of Land and Transportof Korean government

References

[1] S-D Wang X-C Pu K L Scrivener and P L Pratt ldquoAlkali-activated slag cement and concrete a review of properties andproblemsrdquo Advances in Cement Research vol 7 no 27 pp 93ndash102 1995

[2] A Palomo MW Grutzeck andM T Blanco ldquoAlkali-activatedfly ashes a cement for the futurerdquo Cement and ConcreteResearch vol 29 no 8 pp 1323ndash1329 1999

[3] C Shi P V Krivenko and D Roy Alkali-activated cement andconcrete vol 376 Taylor amp Francis Abingdon UK 2006

[4] C Shi A F Jimenez and A Palomo ldquoNew cements for the21st century the pursuit of an alternative to Portland cementrdquoCement and Concrete Research vol 41 no 7 pp 750ndash763 2011

[5] A R Brough and A Atkinson ldquoSodium silicate-basedalkali-activated slag mortars part I Strength hydration andmicrostructurerdquo Cement and Concrete Research vol 32 no 6pp 865ndash879 2002

[6] S Aydin and B Baradan ldquoEffect of activator type and contenton properties of alkali-activated slag mortarsrdquo Composites PartB Engineering vol 57 pp 166ndash172 2014

[7] S H Oh S H Hong and K M Lee ldquoAutogenous shrinkageproperties of high strength alkali activated slag mortarrdquo Journalof the Korean Recycled Construction Resources Institute vol 2no 1 pp 60ndash65 2014

[8] F G Collins and J G Sanjayan ldquoWorkability and mechanicalproperties of alkali activated slag concreterdquo Cement and Con-crete Research vol 29 no 3 pp 455ndash458 1999

[9] M Sofi J S J van Deventer P A Mendis and G CLukey ldquoEngineering properties of inorganic polymer concretes(IPCs)rdquo Cement and Concrete Research vol 37 no 2 pp 251ndash257 2007

[10] C D Atis C Bilim O Celik and O Karahan ldquoInfluenceof activator on the strength and drying shrinkage of alkali-activated slag mortarrdquo Construction and Building Materials vol23 no 1 pp 548ndash555 2009

[11] A A Melo Neto M A Cincotto and W Repette ldquoDrying andautogenous shrinkage of pastes and mortars with activated slagcementrdquo Cement and Concrete Research vol 38 no 4 pp 565ndash574 2008

[12] F PuertasM Palacios andTVazquez ldquoCarbonation process ofalkali-activated slag mortarsrdquo Journal of Materials Science vol41 no 10 pp 3071ndash3082 2006

[13] K Lee and J Seo ldquoEvaluation of flexural behavior of reinforcedconcrete beams using alkali activated slag concreterdquo Journal ofthe Korea Concrete Institute vol 27 no 3 pp 311ndash317 2015

[14] S Choi K Lee and S Yoo ldquoShear behavior of RC beams usingalkali activated slag concreterdquo Journal of the Korean RecycledConstruction Resources Institute vol 3 no 1 pp 58ndash63 2015

[15] T-H Kim K-M Lee C Yoon and H M Shin ldquoInelasticbehavior and ductility capacity of reinforced concrete bridgepiers under earthquake I Theory and formulationrdquo Journal ofStructural Engineering vol 129 no 9 pp 1199ndash1207 2003

[16] E Thorenfeldt A Tomaszewicz and J J Jensen ldquoMechanicalproperties of high strength concrete and application in designrdquoin Proceedings of the Symposium Utilization of High StrengthConcrete T Trondheim Ed vol 40 pp 149ndash159 StravangerNorway 15ndash18 June 1987

[17] S-W Shin S K Ghosh and J Moreno ldquoFlexural ductility ofultra-high-strength concrete membersrdquoACI Structural Journalvol 86 no 4 pp 394ndash400 1989

[18] T-H Kim K-M Lee C Yoon and H M Shin ldquoInelasticbehavior and ductility capacity of reinforced concrete bridgepiers under earthquake II Numerical validationrdquo Journal ofStructural Engineering vol 129 no 9 pp 1208ndash1219 2003

[19] K Maekawa and H Okamura ldquoDeformational behavior andconstitutive equation of concrete using the elasto-plastic andfracture modelrdquo Journal of the Faculty of Engineering Universityof Tokyo Series B vol 37 no 2 pp 253ndash328 1983

Submit your manuscripts athttpswwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CeramicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CompositesJournal of

NanoparticlesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Biomaterials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MetallurgyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

MaterialsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Submit your manuscripts athttpswwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CeramicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CompositesJournal of

NanoparticlesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Biomaterials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MetallurgyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

MaterialsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014