Structural performance of Self-Consolidating Concrete used in reinforced concrete beams

KSCE Journal of Civil Engineering (2012) 16(4):618-626DOI 10.1007/s12205-012-1517-5

− 618 −

www.springer.com/12205

Structural Engineering

Structural Performance of Self-consolidating Concrete Used inReinforced Concrete Beams

Yasser Sharifi*

Received March 18, 2011/Revised July 11, 2011/Accepted September 5, 2011

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Abstract

In recent years, an emerging technology termed Self-Consolidating Concrete (SCC) become popular in construction industry. Aseries of experimental tests carried out to investigate the structural behavior of SCC reinforced beams. A comparison between theexperimental results and theoretical calculations based on the codes provisions has been also done. The beams have been made fromconcrete having average compressive strength of 30 MPa and reinforcement ratio (ρ /ρb) in the range of 0.15-1.38. The ultimatemoment for the tested beams was found to be about (0-7)% and (0-8)% higher than that of the predicted ultimate moment based onACI 318 (05) and CSA (04) code provisions, adopted for reinforced beams cast with normal concrete vibrated into place,respectively. The test results on self-consolidating reinforced concrete beams showed that, the observed crack width under serviceloads were within acceptable limits.Keywords: self-consolidating concrete, reinforced beams, flexural behavior, crack width, code provisions

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1. Introduction

Self-Consolidating Concrete (SCC), was first developed inJapan (Ozawa et al., 1989; Okamura et al., 1993; Okamura andOzawa, 1994, 1995; Nagamoto and Ozawa, 1997) to achievedurable concrete structures. Since then, various investigationshave been carried out and this type of concrete has been used inpractical structures in many countries by large constructioncompanies.

Casting concrete in heavily reinforced sections, such as thosein columns and beams in moment-resisting frames in seismic areasand in some repair sections, makes the placement of concretequite difficult. Providing proper consolidation can require internalor external vibration that can be critical in sections with high-density reinforcement. Ensuring thorough consolidation of criticalstructures with durability and safety concerns is essential and canoften depend on the competence of the vibrating crew to ensureadequate consolidation. Using standard vibration techniques withconventional concrete that is not fluid enough may lead to somesurface and structural defects resulting from lack of proper bonddevelopment between the concrete and the reinforcement as wellas the entrapment of air voids in the concrete. Flowable concreteis normally used to reduce labor cost and shorten constructiontime. Such concrete can have slump consistency close to 200mm to facilitate placement and consolidation. However, specialattention should be given to vibration consolidation of the plasticconcrete in order to avoid segregation and bleeding, which may

further impair structural performance and surface quality.One way to reduce the intensive labor demand for vibration of

highly congested sections is to use Self-Consolidating Concrete(SCC). Such concrete can spread readily into place and fill theformwork without any mechanical consolidation and with mini-mum risk of separation of the material constituents (Paultre, 2005).

Most studies on SCC reported in the literature deal with mix-ture proportioning and characterization of fresh and hardenedconcrete properties with limited information on structural perfor-mance (Khayat and Aitcin, 1998; Khayat and Morin, 2002;Okamura and Ouchi, 2003; Pengfei, 2005; Okamura and Ozawa,1995; Youjun et al., 2005). One of the barriers to the widespreadacceptance of SCC is the lack of information regarding structuralproperties of sections cast with SCC.

Surong and Jianlan (2005) investigated the flexural and shearbehavior of reinforced beams cast with SCC and they found thatin the process of flexural or shear failure under vertical load, thereare no obvious differences between the behavior of SCC beamsand that of normal concrete beams and when the strength ofconcrete and longitudinal bars rate are identical, the yieldingmoment of SCC beams is close to that of normal concrete beams;the ultimate moment of the former is a little larger than that of theletter; the shearing capacity is almost the same; and the crackmoment of SCC is slightly lower than of the normal concretebeams.

Hassan et al. (2008) conducted an experimental investigationto study the shear strength and cracking behavior of beams made

*Assistant Professor, Dept. of Civil Engineering, Vali-e-Asr University of Rafsanjan, Rafsanjan, Iran (E-mail: [email protected], [email protected])

Structural Performance of Self-consolidating Concrete Used in Reinforced Concrete Beams

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with Self-Consolidating Concrete (SCC) as well as Normal Con-crete (NC). A series of reinforced concrete beams, with no shearreinforcement, were tested under mid-span concentrated load untilshear failure occurred. The experimental test parameters includedconcrete type/coarse aggregate content, beam depth and thelongitudinal reinforcing steel ratio. The ultimate shear strength ofSCC beams was found to be slightly lower than that of NC beamsand the difference was more pronounced with the reduction oflongitudinal steel reinforcement and with the increase of beamdepth.

Mazzotti and Savoia (2009) also carried out an experimentaltest to consider the long-term behavior of reinforced Self-Consoli-dating Concrete (SCC) beams. Long-term tests on reinforced SCCbeams have been performed according to the four-point bendingscheme. The maximum stress on concrete in compression wasapproximately 35% of strength at the time of loading (37 days).A small flexural strength increase with age at testing has beenobserved from the comparison of failure tests. It is related on asmall compressive strength increase due to concrete aging.

This paper presents the experimental results on the mechanicalbehavior of self-consolidated reinforced concrete beam underfour-points bending. The aim of this study is to demonstrate thestructural behavior (ultimate strength, load versus deflection andcrack width, deflection and crack width in service load, strains incompressive concrete and tension steel, neutral axis depth varia-tion) of flexural members which made of SCC. In order to have acomparison, the abovementioned results have been comparedwith the theoretical calculations based on the codes provisions.The ACI 318 (2005), CSA (2004) and for calculating the widthcrack BS 8110 (1985) provisions that adopted for reinforcedconcrete beams cast with conventionally-vibrated normal concrete(NC), have been employed. The results should be of interest toengineers considering the use of such concrete in various struc-tural applications.

2. Materials

The approach in this research on the development of SCC forcasting reinforced beams involved using high paste volume (andlow aggregate volume) to promote high deformability and reducethe risk of blockage and segregation during concrete placement.Self-consolidating concrete can be distinguished from conven-tional concrete not only by its high fluidity but also by its compo-sition. The most important distinctions are (Khayat et al., 2004):

Use of a high content of powder materials (<80 µm, from 450to 600 kg/m3) that necessitates the replacement of up to 50% ofthe powder content by supplementary cementitious materials and/or fillers.

Use of large quantities of super-plasticizer and use of a viscosity-enhancing admixture in some cases when the water content is notlow enough to promote sufficient viscosity of the paste.

This research was completed in two steps. The first step in-volved the study of the rheological properties of the SCC, whilethe second part consisted of validating the use of SCC for struc-

tural applications. In order to perform the second step, concretebeams were made with SCC.

3. Workability of SCC

The workability of fresh SCC was characterized by using anumber of testing methods described below. These tests provid-ed the means for comparing different mixtures and predicting theresponse of fresh concrete for mixture optimization.

3.1 Slump-Flow TestConventional concrete has a relatively high yield value; however,

under vibration, the yield value is artificially lowered, leading tothe spread and compaction of concrete. SCC has a low yieldvalue (or high deformability), making vibration unnecessary.The consistency of SCC is evaluated with the slump-flow test,which consists of determining the mean spread of the concrete atthe base of the slump test after the end of spreading. Such valuecan be related to the yield stress of the concrete, and the rate ofspread with time can be related to the plastic viscosity (Khayat etal., 2004) (Fig. 1). The slump-flow test is used to assess fillingability, or the unrestricted deformability of SCC.

3.2 Funnel TestA trap is opened in a funnel filled with concrete (Fig. 2), and

the time required to empty the funnel is measured. This test isbased on a model proposed by (Ozawa et al., 1995). This test isused to evaluate the flowing ability of the SCC and can assess

Fig. 1. A Schematic View of the Slump-flow Test

Fig. 2. A Schematic View of the Funnel Test

Yasser Sharifi

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the dynamic stability of the concrete. A long flow-out durationcan be due to segregation (aggregates stacking at the opening) orexcessive concrete viscosity.

3.3 L-Box TestWith the L-Box apparatus, it is possible to measure different

properties such as flow ability, blocking and segregation of theconcrete (Sonebi and Bartos, 1999). The height of remainingconcrete in the vertical section (H1) and the height of concrete atthe end of the horizontal part (H2) are determined, and then the(H2/H1) value is calculated. The ratio between these two heights(H2/H1), which is usually between 0.7-0.9 for SCC (Nehdi andLadanchuk, 2004), was used to evaluate the ability of the SCCmixtures to flow around observations. This limit, however, hasbeen proposed to be within 0.8 and 1.0 by EFNARC guidelines(2002). A typical test is shown in Fig. 3.

Table 1 presents the concrete mixture proportions used for theconcrete of the beam specimens tested in this study. Locallymanufactured cement and commercially available powderedsilica fume used as binder. A sufficient mixing time was allowedto produce a uniform and homogenous concrete.

4. Structural Program and Testing

Six simply supported reinforced SCC beams were tested underfour point bending with a pure moment region. Typical reinfor-cement arrangement and geometry of the beam are shown inFigs. 4(a), (b), (c) and (d). All beams were designed for the shearspan to depth ratio of 3.5. The clear cover for the tested beamswas maintained at a minimum of 25 mm. Each beam was desig-nated using letters and numbers. The letters ‘SCC’ refers to themix containing Self-Consolidating Concrete (SCC). The numbers(1, 2 to 6) followed by the letter refers to the percentage oftension reinforcement ratios (ρ /ρ b) to the range of 0.15-1.38.The tension reinforcement ratios (ρ) were at the range of 0.0059-0.049. All the beams were cast in steel moulds and the companion

concrete specimens were cast in standard steel moulds. For eachmix, three numbers of 100 mm cubes for compressive strengthwere cast. The beams and the companion concrete specimens

Fig. 3. A Schematic View of the L-box

Table 1. Mix Proportion of Ingredients Slump flow

Dia. (cm) V-funnel Time (s)

L-box(H2/H1)

PCE (Lit)

Micro silica (kg)

Limestone powder (kg)

Sand (kg)

Gravel (kg)

Cement (kg) W/P

70-73 6.0 0.83 4 30 225 870 750 270 0.39

Fig. 4. (a) Typical Geometry of the Beams, (b) Typical ReinforcedArrangement of the Beams SCCB1, 2, (c) Typical Rein-forced Arrangement of the Beams SCCB3, 4, 5, (d) TypicalReinforced Arrangement of the Beam SCCB6

Fig. 5. Typical Test Set for the Tested Beams


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were demoulded after 24 h and were cured with wet hessian(spraying the water twice a day, similar to site curing) for 6 days.After that, the specimens were air-cured with relative humidityof 65-80% and ambient temperature 28±3oC until the age oftesting. The typical loading arrangement for the test beam is shownin Fig. 5. Locally available deformed bars were used as flexuralreinforcement. The average yield strength of the longitudinalreinforcement was found to be approximately 400 MPa from thetension tests performed in the laboratory. The detailed beams areshown in Table 2.

The load was applied statically step-by-step to the beam at arate of 2 kN per step using 1400 kN testing machine. The beamswere instrumented with both Linear Voltage DisplacementTransducers (LVDT) and mechanical deflectometer to have anaccurate and safe data. Deflections at mid span and other severalsections near mid span have been recorded. Mechanical straingauges and electric strain gages (in some beams) were used tomeasure the concrete strain on the surface in the pure bendingregion. Steel strains were measured using PL-30-11 gauges (Fig.6). The steel strain gauges were covered with silicone gel toprevent the accidental damage during casting (Fig. 7). The crackwidth measurements were made using a hand-held microscopeof ×40 magnification with least count of 0.02 mm. All the strainsand deformation readings were recorded automatically usingdata logger during the test. Figs. 8(a) and 8(b) presented as thetypical test set for the tested beams in the laboratory.

Table 2. Properties of SCC and Reinforcement Details of the Tested Beams Beam Type fc' (MPa) As A's d (mm) d ' (mm) ρ ρ ' ρ/ρb

SCCB1 31.60 2 φ 14 2 φ 14 258 42 0.0059 0.0059 0.15 SCCB2 32.84 2 φ 20 2 φ 14 255 42 0.0123 0.0060 0.30 SCCB3 28.84 2 φ 18 + 2 φ 16 + 2 φ 14 2 φ 14 + 2 φ 18 256 43 0.0168 0.0109 0.40 SCCB4 27.39 2 φ 20 2 φ 14 + 2 φ 20 255 43.5 0.0246 0.0122 0.58 SCCB5 29.53 2 φ 22 2 φ 14 + 2 φ 25 254 45 0.0299 0.0157 0.62 SCCB6 27.20 2 φ 28 2 φ 14 251 42 0.0490 0.0061 1.37

Fig. 7. The Covered Strain Gauges with Silicone Gel

Fig. 6. Electrical Strain Gauge Mounted on the Steel for MeasuringStrain

Fig. 8. (a) Typical Set up for the Tested Beam, (b) Typical Set upfor the Tested Beams

Yasser Sharifi


5. Test Results and Discussions

5.1 Ultimate MomentThe predicted ultimate moments have been calculated based

on the reinforced concrete design fundamental which has beenpresented by Eqs. (1)-(10) and using ACI 318 (2005) and CSA(04) (2004) code provisions, named Mu,ACI and Mu,CSA, respectively.The experimental cracking moment (Mcr,exp), corresponds to themoment at which the initial slope of the load-deflection curvedeviates; the experimental yielding moment (My,exp), correspondsto the moment at which yielding flat plateau is observed in theload-deflection curve; and the experimental ultimate moment(Mu,exp), is the moment obtained from the ultimate load reachedduring testing (Ashour, 2000). Foregoing approaches has beenused to estimate the abovementioned experimental moments andare shown in Table 3.

5.1.1 Under-reinforced Beams (SCCB 1-5) Compression reinforcement is yield:

(1)

(2)

Compression reinforcement is not yield:

(3)

(4)

(5)

5.1.2 Over-reinforced Beams (SCCB 6)Compression reinforcement is yield:

(6)

(7)

Compression reinforcement is not yield:

(8)

(9)

(10)

where, As: Area of tension longitudinalA's: Area of compression longitudinalb: Width of beam sectiond: Effective depthd': The distance compression reinforcement to top surface

of beamEs: Modulus of elasticity of steel reinforcementf 'c: Compressive strain of concretef 's: Stress in compressive reinforcementfy: Yielding stress in tension reinforcement

Xu: Neutral axis at ultimate stateα: The stress block coefficientβ1: The ratio between the height of the stress block and Xu

εcu: Ultimate strain in compressive concrete

It can be found from Table 3 that there is a good agreementbetween experimental (Mu,exp) and theoretical ultimate momentsthat have been calculated based on the ACI and CSA codesprovisions which are recommended for the conventional concrete(Mu,ACI and Mu,CSA).

The Mu based on the design codes (ACI and CSA) was foundto be (0-7)% and (0-8)% lower than the Mu,exp respectively.Compared to ACI (05) code provisions, the CSA (04) codeprovisions give a reasonable conservative estimate. However,further investigations on creep and shrinkage are needed toconfirm this statement.

As it was expected, by increasing the tensile reinforcementratio the experimental yield moment (My,exp) and ultimatemoments (Mu,exp, Mu,ACI and Mu,CSA) are increased. It can be foundthat in order to calculate the ultimate moments, the provisionsthat are recommended for reinforced conventional concretebeams in current investigated codes (ACI and CSA), can be usedto analysis the self-consolidating reinforced concrete beams.

5.2. DeflectionThe mid span deflections due to short-term loading for the

different beams are presented in Fig. 9. Despite the strength ofthe compressive concrete is low varied from 27.2 to 32.84 MPa,It was found that the steel reinforcement ratios were moredominant than the concrete compressive strength. It can be foundthat by increasing the steel reinforcement ratio the deflection atyielding of tension reinforcement increased and the ultimatedeflection was decreased; hence the beams with low tensile rein-

XuAs A's–( )fy

αβ1 f 'cb------------------------=

Mu αβ1 f 'cbXu d β1Xu 2⁄–( ) A's f 'y d d '–( )+=

Xu2 εcuEsA's Asfy–

αβ1 f 'cb-------------------------------⎝ ⎠⎛ ⎞Xu

εcuEsA'sd'αβ1 f 'cb

----------------------⎝ ⎠⎛ ⎞–+ 0=

f 's EsεcuXu d '–

Xu--------------⎝ ⎠⎛ ⎞ f 'y≤=


Xu2 A'sfy εcuEsAs+

αβ1 f 'cb--------------------------------⎝ ⎠⎛ ⎞Xu

εcuEsAsdαβ1 f 'cb

--------------------⎝ ⎠⎛ ⎞–+ 0=


Xu2 εcuEs A's As+( )

αβ1 f 'cb---------------------------------⎝ ⎠⎛ ⎞Xu

εcuEsβ1 Asd A'sd '+( )αβ1 f 'cb

----------------------------------------------⎝ ⎠⎛ ⎞–+ 0=

f 's EsεcuXu d '–

Xu--------------⎝ ⎠⎛ ⎞ f 'y≤=


Table 3. Experimental and Predicted Ultimate Moments of Tested BeamsBeam Type Mcr,exp (kN·m) My,exp (kN·m) Mu,exp (kN·m) Mu,ACI (kN·m) Mu,CSA (kN·m) Mu,exp/My,exp Mu,exp/Mu,ACI Mu,exp/Mu,CSA

SCCB1 7.21 19.91 33.30 31.00 30.80 1.6725 1.0742 1.0811SCCB2 7.21 49.78 60.42 58.45 58.17 1.2136 1.0337 1.0386SCCB3 8.925 65.58 78.28 77.99 77.64 1.1936 1.0037 1.0082SCCB4 11.33 93.39 110.55 109.06 108.69 1.1837 1.0136 1.0171SCCB5 8.24 113.30 131.84 130.03 129.67 1.1636 1.0139 1.0167SCCB6 9.27 a 151.75 143.00 141.24 - 1.0612 1.0744

aSCCB6 is over-reinforcement


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forcement ratio underwent larger deflections compared to beamswith higher ratio. It indicates that increasing reinforcement ratiodecreases deflection ductility. In other words greater ductility canbe achieved only with lesser reinforcement ratio.

5.3 Crack WidthThe relationship between applied load and crack width for the

tested beams are shown in Fig. 10(a). As observed, all the beamsexhibited vertical cracks known as flexural cracks in the purebending region before failure. Here, the maximum flexural crackwhich was occurred at the pure moment zone has beeninvestigated to draw the relationship between load and crackwidth (Fig. 10a) as loading. The maximum flexural crack widthwas recognized to be the width of the first flexural crack whichhappened at the utmost tension fiber of the beam surface.

Figure 10(b) shows the crack patterns of a tested beam when itwas collapsed. It can be found from Fig. 10(b) that the crack pro-pagation outside the pure bending region was similar to flexuralcracks. However, at higher loads, shear stress increased and thecracks traveled towards the support.

This is similar to the reported researches on beams made withconventional concrete. As it was expected, the reinforcementratios significantly control the crack width of flexural members.It was well known that the aggregate-mortar matrix stronglyinfluence the crack formation in SCC. Since fine aggregates areporous and reactive, it forms a weaker link between aggregate-mortar matrixes in the transition zone. As it is obvious, byincreasing the tension reinforcement ratio the crack width in aconstant load is decreased.

5.4 Maximum Deflection at Service LoadTo investigate the service load behavior with respect to deflec-

tion, maximum (mid-span) deflections, (δser,exp) at service load(experimental ultimate load divided by a factor of 1.7) (Rashidand Mansur, 2005) are calculated for the test beams using theelastic bending theory as:

(11)

where, Ma is the applied maximum (mid-span) moment; L is thebeam span; a is the shear span.

Ec is the modulus of elasticity of concrete and the moment ofinertia, I, is taken as that specified by the ACI code (2005) foreffective moment of inertia, Ie, as:

(12)

in which Mcr is the cracking moment of beam and Ig and Icr aremoments of inertia of gross and cracked sections, respectively.

Comparisons between the calculated (δser,ACI and δser,Icr) and thecorresponding experimental deflections at service load, as shownin Table 4, indicate that the use of ACI code expressions for fr

and Ec leads to highly unconservative predictions (δser,ACI).The calculated deflection based on the fully cracked beam,

(δser,Icr), also is shown in Table 4, as it is obvious, even the as-sumption of a fully cracked beam, that is, use of Ie=Icr was a littlebenefit. Average ratio of measured deflection to the predicteddeflection based on ACI 318 (05) was 1.25 and 1.15 based on the

δserMa

24EcI------------- 3L2 4a2–( )=

Ie Icr Ig Icr–( )Mcr

Ma--------⎝ ⎠⎛ ⎞

3

+ Ig≤=

Fig. 9. Mid Span Deflection of Different Beams

Fig. 10. (a) Load versus Crack Width Beams, (b) Propagation ofCrack in the Flexural Beam

Table 4. Experimental and Predicted Deflection at Service Load

Beam Type δser,exp(mm)

δser,ACI(mm)

δser, Icr(mm) δser,exp/δser,ACI δser,exp/δser,Icr

SCCB1 6.278 2.5067 4.7246 2.5044 1.3287SCCB2 7.2495 4.8522 5.1686 1.4940 1.4026SCCB3 7.5857 5.3194 5.3861 1.4260 1.4083SCCB4 8.9299 5.8499 5.8616 1.5265 1.5234SCCB5 9.08089 6.0685 6.0738 1.49639 1.4950SCCB6 7.57 5.5133 5.5133 1.37304 1.37034

Average value 6.294015 5.018333 5.454666 1.254204 1.153877

Yasser Sharifi


fully cracked beam (by using Icr). The total deflections underservice load for the tested beams varied from 6.27 to 9.081 mm.These measured deflections are based on short-term loading anddo not allow any time dependent increase due to shrinkage andcreep. This may be the reason for excessive deflection.

5.5 Maximum Crack Width at Service LoadThe maximum crack widths, wcr,exp, measured at the center of

the bottom layer of tensile reinforcement at the assumed serviceload is presented in Table 5. For analytical evaluation, expressionsuggested by Gergly and Lutz (1968) and those recommended inBS8110 (1985) have been chosen for assessment. In Table 5 theexperimental maximum crack widths are compared with thecorresponding predicted values, denoted as wcr,G&L and wser,BS, re-spectively. The expression suggested by Gergly and Lutz (1968),however, gives very good predictions.

The maximum crack width observed at service load variedfrom 0.2 to 0.25 mm and it is well within the durability require-ments as per ACI 318 and BS8110 codes. Analyzed results fromTable 5 showed that BS8110 code overestimated the crack widthat the centre of the tensile reinforcement level. It was found fromresults that the maximum crack width decreased as the tensilereinforcement ratio increased. The equation recommended in BScode is sensitive to cover, slight variations leading to increase inthe crack width and therefore it was found overestimated.

5.6 Concrete StrainFigure 11 shows the measured compressive strain of concrete

corresponding to the load at top extreme fiber. At ultimate stage,the measurement of concrete strain may not be precise becauseof rapid advancement of cracks. The values shown in Table 6

refer to the concrete strain at approximately 90% of the ultimateload. It varied from 3418×10-6 to 5790×10-6 m/mm for the beams.The measured concrete strain variations among beams was dueto low variations in compressive strength of concrete, but as itcan be shown from Fig. 11, by increasing the tensile reinforce-ment ratio, the compressive concrete strain in a constant load isdecreased (except beam SCCB6). As already was explained, theaggregate-mortar interface significantly lowers the tensile strengthand it constitutes the weakest link in the concrete composite.

5.7 Steel StrainThe measured loads corresponding to tensile steel strain for

different beams are shown in Fig. 12. The measured tensile steelstrain for the tested beams increased almost linearly up to 70% ofthe ultimate load. After that it increased rapidly. This may bebecause of the loss of adhesion between the concrete and steel atthe deformations. Fig. 12 showed that by increasing the steelreinforcement ratio the ultimate tension steel strain is decreased.

5.8 Neutral Axis DepthExperimental neutral axis depth (X/d)exp is obtained from the

strain distribution which is measured experimentally at thecompression concrete and at the tension reinforcement (Fig. 13).The analytical neutral axis-to-depth ratio at ultimate state, (X/d)ACI and (X/d)CSA, predicted based on the rectangular stress blockmethod which is listed by Equations 1-10 using recommendedprovisions that is mentioned in ACI 318 (05) and CSA (04)codes. The test results are analyzed and presented in Table 6. Itwas shown from test results that the NA depth increases as tensilereinforcement ratio increases. A lower reinforcement ratioensures that the depth of NA is lower, hence leading to ductilefailure. The ultimate concrete strain is assumed as 0.003 and

Fig. 11. Development of Concrete Strain of Different Beams

Table 5. Experimental and Predicted Crack Width at Service Load

Beam Type ωser,exp(mm)

ωser,G.&L(mm)

ωser,BS(mm)

ωser,exp/ωser,G&L

ωser,exp/ωser,BS

SCCB1 0.247812 0.22275 0.3062 1.116 0.809314SCCB2 0.2345 0.24230 0.2827 0.967 0.8294848SCCB3 0.229847774 0.2017 0.25067 1.1395 0.9169107SCCB4 0.203468869 0.19918 0.314926 1.021 0.6460845SCCB5 0.20145 0.2051 0.2989566 0.9822 0.67384SCCB6 0.2 0.2328 0.3639196 0.8591 0.54957189

Average value 0.219513 0.2172916 0.3028953 1.01022 0.7247157

Fig. 12. Load versus Tensile Steel Strain Beams

Fig. 13. Beam Cross Section and Strain Distribution


Vol. 16, No. 4 / May 2012 − 625 −

0.0035 for the ACI and CSA code provisions, respectively, andthose are used for calculating the theoretical NA depth. It wasshown by many researchers the ultimate concrete strain of con-ventional concrete varies from 0.002 to 0.004 or even moreespecially. Therefore it is necessary to revise rectangular stress-strain parameters to integrate the concrete strength as a functionto evaluate ultimate concrete strain.

It can be found from Table 6, that there is a very good agree-ment between experimental and analytical results.

By comparing the experimental and analytical results (Table6), it can be concluded that using the rectangular stress blocktheory that is recommended in two current investigated codes(ACI and CSA), in order to calculate the neutral axis depth inultimate stage can be used for estimating the NA of reinforcedbeams that are cast with self-consolidating concrete.

6. Conclusions

This paper compares the mechanical performance of reinforcedbeams cast with Self-Consolidating Concrete (SCC) to that ofpredicted by provisions code that are recommended for NormalConcrete (NC) vibrated into place to ensure proper filling andconsolidation equivalent. The tested beams had average nominalconcrete compressive strengths of 30 MPa. The used reinforce-ment beams had nominal steel yield strengths of 400 MPa. Atotal of 6 beams were tested in this experimental investigation todetermine the behavior of such members.1. The use of SCC reduced significantly the time of casting highly

congested beam section. The optimized mixtures allowed ade-quate placement of concrete heavily reinforced beams andachieved high levels of filling capacity, regardless of shear andlongitudinal configuration.

2. It can be concluded from comparing the experimental and ana-lytical results that to calculate the moment and neutral axisdepth in ultimate stage, the theoretical calculations that areused for reinforced beams with conventional concrete can beused for reinforced beams cast with self-consolidating con-crete.

3. The experimental ultimate moments was found to be higherby about (0-7)% and (0-8)% compared to the ultimate momentpredicted based on ACI and CSA code, respectively.

4. The measured crack width under service load was well withinallowable limit for durability requirements suggested by codes.The equation recommended by Gergely and Lutz (1968) gives

very close values to experimental measured crack width.5. The deflection under service load exceeded than that evaluated

based on the code provisions for estimating the deflection.However, the measured deflections are based on short termloading and the effect of creep and shrinkage are not taken into account in the design calculations. Therefore further investi-gations on creep and on shrinkage may be needed to confirmthe variations in deflections.

Acknowledgements

The experimental part of the present study was undertaken atthe Kerman concrete Laboratory, Iran; where I have worked inand the efforts of Prof. Maghsoudi is greatly acknowledged. Theeffort of Mr. Diba who used a part of the present experimentalwork as his master dissertation is very much appreciated re-garding his help in experimental set up to authors. The author ispleased to acknowledge the Vali-e-Asr University of Rafsanjansupport.

References

ACI Committee 318 (2005). Building code requirements for reinforcedconcrete, ACI 318-02, and Commentary, ACI 318R-02, AmericanConcrete Institute, Detroit.

Ashour, S. A. (2000). “Effect of compressive strength and tensilereinforcement ratio flexural behavior of high-strength concrete beams.”Engineering Structures Journal, Vol. 22, No. 5, pp. 413-423.

BS 8110 (1985). Structural use of Concrete: Part 2: Section 3, BritishStandard Institution, London.

CSA 94 (2004). CSA technical committee, CAN3-A23.3-M04,Canadian Standards Association, Rexdale, Ontario.

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Table 6. Experimental and Predicted Values of x/d and Compressive Strain of Concrete

Beam Type Ultimate load(kN) (X/d)exp (X/d)ACI (X/d)CSA (X/d)exp/(X/d)ACI (X/d)exp/(X/d)CSA

Compressive strain of concrete (×10-6)

SCCB1 63.428 0.1448 0.1365 0.1384 1.0608 1.0462 5550SCCB2 115.086 0.1960 0.1911 0.1893 1.0256 1.0354 5790SCCB3 149.112 0.2348 0.2343 0.2341 1.0021 1.0029 3418SCCB4 210.572 0.3256 0.3233 0.3215 1.0071 1.0127 3861SCCB5 251.124 0.3463 0.3457 0.3458 1.0017 1.0014 4033SCCB6 289.048 0.6987 0.6837 0.6822 1.02198 1.0241 3462

Yasser Sharifi


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Structural performance of Self-Consolidating Concrete used in reinforced concrete beams