ACI Journal SCC Specs

ACI Materials Journal/March-April 2006 121

ACI MATERIALS JOURNAL TECHNICAL PAPER

ACI Materials Journal, V. 103, No. 2, March-April 2006.MS No. 04-377 received November 23, 2004, and reviewed under Institute publication

policies. Copyright © 2006, American Concrete Institute. All rights reserved, includingthe making of copies unless permission is obtained from the copyright proprietors.Pertinent discussion including authors’ closure, if any, will be published in the January-February 2007 ACI Materials Journal if the discussion is received by October 1, 2006.

Proper selection of test methods and workability specificationsare key concerns in the optimization and control testing of self-consolidating concrete (SCC). An experimental program wascarried out to evaluate the suitability of various test methods forworkability assessment and to propose performance specificationsof such concrete used in structural applications. Various workabilitycharacteristics were determined for approximately 70 SCC mixturesmade with water-cementitious material ratios (w/cm) of 0.35 and0.42. Workability responses included the slump flow, J-Ring, V-funnelflow time, L-box, filling capacity, and surface settlement tests.

Comparisons of various test methods indicate that the L-boxblocking ratio (h2/ h1) and the J-Ring flow diameter can be relatedto filling capacity values determined using the caisson test. It isrecommended that SCC used in structural applications shouldhave slump flow values of 620 to 720 mm. To ensure proper fillingcapacity greater than 80%, such concrete should have highpassing ability that corresponds to L-box blocking ratio (h2/ h1) ≥0.7, J-Ring flow of 600 to 700 mm, slump flow minus J-Ring flowdiameter ≤ 50 mm, or V-funnel flow time ≤ 8 seconds. Such SCCshould have a settlement rate of 0.16%/h at 30 minutes, corre-sponding to 0.5% maximum settlement.

Keywords: rheology; segregation; self-consolidating concrete; workability.

INTRODUCTIONWorkability characteristics and test methods

Self-consolidating concrete (SCC) is a new class of high-performance concrete that can spread readily into placeunder its own weight and fill restricted sections as well ascongested reinforcement structures without the need ofmechanical consolidation and without undergoing anysignificant separation of material constituents. The use of SCCcan improve productivity in structural applications such asrepair, and facilitate the filling of restricted sections. Suchconcrete has been widely used to facilitate construction opera-tions, especially in sections presenting special difficulties tocasting and vibration, such as bottom sides of beams, girders,and slabs.

Workability requirements for successful casting of SCCinclude high deformability, passing ability, and properresistance to segregation.1,2 Deformability refers to theability of SCC to flow into and completely fill all spaceswithin the formwork, under its own weight. Deformability isthe property most commonly associated with SCC andprovides the justification for the acceptance of the technology.Ensuring high deformability and dynamic stability isessential for the successful use of SCC in structural applications.Such SCC can achieve complete encapsulation of thereinforcement and spread fully among closely spacedobstacles. This is necessary to ensure proper bond to thereinforcing steel and secure homogeneous distribution ofin-place properties of the hardened concrete, includingdurability characteristics.

The dynamic stability refers to the resistance of concreteto the separation of constituents during placement into theformwork. This characteristic of concrete is required toensure uniform distribution of solid constituents upon transportand placement into the formwork.3 This can be evaluated bydetermining the ability of concrete to pass among variousobstacles and narrow spacing in the formwork withoutblockage (passing ability). Concrete with high deformabilityand good passing ability can achieve adequate fillingcapacity in restricted and congested sections that are typicalin structural repair applications. Static stability refers to theresistance of the fresh concrete to segregation, bleeding, andsurface settlement after casting while the concrete is still ina plastic state.

Several test methods are used to assess the dynamicstability of SCC. Khayat et al.4 investigated the suitability ofa number of different tests for evaluating deformability andpassing ability of SCC and found that SCC with apparentyield stress (g) values of 0.3 to 1.7 N⋅m and torque plasticviscosity (h) values of 17 to 27 N⋅m⋅s can achieve highpassing ability determined using the L-box flow time of 4 to8 seconds. The authors reported that the L-box, U-box, andJ-Ring tests that are primarily employed to evaluate thepassing ability can also enable the evaluation of deformabilityand resistance to segregation.4 In particular, the L-box test isrecommended along with the slump flow test for field-oriented quality control testing of SCC. The rheologicalparameters (g and h values) were determined using amodified two-point workability rheometer (IBB).5,6 Therheometer had an H-shaped impeller rotating in a planetarymotion. The testing protocol consisted of graduallyincreasing the mixing speed up to a maximum velocity.Subsequently, the speed was reduced in predetermined stepsvarying from 0.6 to 0.1 rps, the required torque to shear thematerial was recorded, and the data were used to derivethe rheological parameters assuming a Bingham fluid. Theslope of the linear regression and the intercept with thetorque axis at zero shear rate were determined and related tothe torque plastic viscosity (h, N⋅m⋅s) and apparent yieldstress (g, N⋅m), respectively. The reader should refer to thework of Ferraris et al.7 for a comparison of rheologicalparameters carried out on concrete mixtures using five typesof rheometers, including the modified two-point rheometerused in this research.

Title no. 103-M14

Performance-Based Specifications of Self-Consolidating Concrete Used in Structural Applicationsby Soo-Duck Hwang, Kamal H. Khayat, and Olivier Bonneau

ACI Materials Journal/March-April 2006122

SCC mixtures designated for structural applicationsshould flow through restricted spacing and completely fillthe form without any mechanical vibration. A number of testmethods can be used to assess the filling capacity of SCC,including mock-up tests developed for acceptance testing.8,9

These tests can simulate concrete behavior in actual constructionwith respect to deformability, passing ability, resistance todynamic segregation, and rate of deformation. As indicated inTable 1, the filling capacity, referred to as restricteddeformability, has been evaluated, though indirectly, by

testing the passing ability. In particular, the filling vessel(caisson) tests provide a small-scale model of a highlycongested section and are suitable to evaluate the fillingcapacity of SCC and its self-consolidating characteristics.10,11

Filling capacity tests can also provide visual assessmentof the self-leveling ability of the concrete. These tests,however, are difficult to perform on site and necessitaterelatively intensive labor.

Ozawa et al.12 and Khayat et al.13 proposed the combineduse of the V-funnel flow time and slump flow tests to assessthe filling capacity of SCC. Multiple regression relationshipcorrelating the filling capacity, slump flow, and V-funnel flowtime, can be expressed as follows: filling capacity (%) = 8.1 +0.107 slump flow (mm) – 1.107 flow time (in seconds).13 Thisrelationship is valid for concrete with slump flow valuesbetween 550 and 780 mm, filling capacity greater than 40%,V-funnel flow time of less than 20 seconds, and for SCC madewith maximum size aggregate (MSA) of 20 mm, and forconcrete that does not contain any air entrainment.

A number of test methods have been used to assess staticstability. For example, the V-funnel test can be used tomeasure the variation of flow time following a given periodof rest to evaluate the resistance of the SCC to segregationafter casting.14 Other tests include the surface settlementtest,15 the penetration apparatus test proposed by Van et al.,16

segregation resistance of hardened concrete,17 and electricalconductivity approach.18 The visual stability index (VSI) fromthe slump flow test is also useful for the qualitative assessmentof segregation.19 The column surface settlement test has beenextensively used by the authors to evaluate the static stabilityof SCC, both in the laboratory and in the field. Assaad etal.19 compared the suitability of various test methods toassess static stability of SCC, which included the columnsurface settlement, column segregation, and electricalconductivity tests. The surface settlement test is appropriateto assess stability over the dormant period of cement hydration.This test, however, is long, as it involves the monitoring ofsettlement until the onset of hardening. The column segregationtest involves the determination of the distribution of coarseaggregate in a concrete column and is suitable for use at abatching plant or at a job site. The authors related thesegregation index Iseg determined from the column segregationtest to the g and h values determined using the modifiedTattersall two-point workability rheometer.19 SCC with g andh values of 0.3 to 1.7 N⋅m and 17 to 30 N⋅m⋅s, respectively,can develop adequate resistance to segregation with Isegvalues of 2 to 4%.19

Performance specifications of self-consolidating concrete

Various test methods to assess workability characteristicsof SCC are summarized in Table 1, which also includes somelimit values recommended by the European Federation ofNational Trade Associations (EFNARC),20 Precast/Prestressed Concrete Institute (PCI) Interim Guidelines,3

RILEM TC 174,2 Swedish Concrete Association (SCA),21

and the Japan Society of Civil Engineers (JSCE).14,22 For eachworkability characteristic (deformability, passing ability, fillingcapacity, and static stability), various test methods arerecommended in the aforementioned specifications.

The recommended test methods and performance specifi-cations are normally used in combination for various types ofSCC. For example, according to SCA21 and the SwedishCement and Concrete Research Institute (SCCRI),23 SCC

Soo-Duck Hwang is a PhD candidate at the Université de Sherbrooke, Quebec,Canada. His research interests include workability, transport properties, andvisco-elastic properties of self-consolidating concrete.

Kamal H. Khayat, FACI, is Professor of Civil Engineering at the Université deSherbrooke. He is a member of ACI Committees 234, Silica Fume in Concrete; 236,Material Science of Concrete; 237, Self-Consolidating Concrete; and 552, GeotechnicalCement Grouting. His research interests include self-consolidating concrete, rheology,and concrete repair.

ACI member Olivier Bonneau is a research assistant at the Université de Sherbrookeand coordinator of the Research Centre on Concrete Infrastructure. His researchinterests include self-consolidating concrete and concrete repair.

Table 1—Workability characteristics, test methods, and recommended values

Workabilitycharacteristic Test methods

Recommended values suggested in 1 to 6

Deformability and flow rate

(filling ability,unrestricted flow)

Slump flow

1. Authors: 620 to 720 mm2. EFNARC: 650 to 800 mm

(MSA up to 20 mm)3. JSCE: 600 to 700 mm4. PCI: ≥660 mm5. RILEM TC 174: N/A6. Swedish ConcreteAssociation: 650 to 750 mm

T-502. 2 to 5 seconds4. 3 to 5 seconds6. 3 to 7 seconds

Passing ability

(narrow-opening passing ability, confined flow, restricted flow,

dynamic stability)

V-funnel*1. <8 seconds2. 6 to 12 seconds4. 6 to 10 seconds

L-box, h2/h1

2. >0.84. >0.756. >0.8

U-box, Bh

2. h2/h1: 0 to 30 mm

3. Rank 1† (35 to 60 mm reinforcing bar spacing)Rank 2‡ (60 to 200 mmreinforcing bar spacing)4. Rank 1

J-Ring§ 2. <10 mm4. <15 mm

Filling capacity

(filling ability +passing ability,

restricteddeformability)

Filling vessel(caisson)

1. ≥80%2. 90 to 100%

L-box, h2/h1 Same as passing ability

U-box, Bh Same as passing ability

J-Ring Same as passing ability

Static stability

(resistance tosegregation, bleeding,

and settlement)

Surface settlement 1. ≤0.5%

Visual stability index 4. 0 or 1

Penetration 5 and 6. ≤8 mm

GTM screen stability 2. ≤15%

*V-funnel opening of 65 x 75 mm.†Rank 1 refers to Bh of 305 mm through 5 to 10 mm-diameter bars with 35 mm clearspacing.‡Rank 2 refers to Bh of 305 mm through 3 to 12 mm-diameter bars with internal andexternal spacing of 35 to 45 mm, respectively.§J-Ring value is determined by difference in height of concrete between inside andoutside in J-Ring.


used for civil engineering structures should have a slumpflow of 650 to 750 mm, T-50 time of 3 to 7 seconds, andL-box blocking ratio (h2/h1) greater than 0.8.

The performance specification of SCC can be a function ofthe aggregate characteristics. For example, the UniversityCollege London24 proposed workability recommendationsfor concrete made with MSA of 10 and 20 mm. For mixturesmade with 10 mm MSA, slump flow consistency of 600 to700 mm, V-funnel flow time of 2 to 4 seconds, and U-boxheight of 300 to 350 mm are recommended. In the case ofSCC prepared with 20 mm MSA, these values can be 650to 700 mm, 4 to 10 seconds, and 300 to 350 mm, respectively.

The level of workability of SCC should be compatible withthe placement technique.3 Several placement techniques, suchas truck discharge, pumping, conveyor, buggy, and droptube, can provide different energy during the initial flow ofSCC. In the PCI Interim Guidelines,3 recommendations forworkability of SCC take into consideration the placementenergy provided by the casting method as well as thecharacteristics of the cast element, including reinforcementlevel, element shape intricacy, element depth, surface finishimportance, element length, wall thickness, and coarseaggregate content (Table 2). These recommendations arebased on work reported by Constantiner and Daczko.25

According to these recommendations, SCC used for castinghighly reinforced elements with intricate shape (such astypically encountered in structural repair) should haveslump flow greater than 660 mm, T-50 time of 3 to 5 seconds,L-box blocking ratio (h2/h1) higher than 0.75, and V-funnelflow time of 6 to 10 seconds. Shaded areas in Table 2 representpotential problem situations.

According to the German SCC guideline,26 the J-Ring testcan be used in conjunction with the slump flow test to evaluatethe passing ability of SCC. This guideline proposes that thedifference between flow diameters of the two tests shouldnot exceed 50 mm for the concrete to achieve sufficient flowthrough the reinforcement. However, limited information isavailable regarding relationships between workabilityresponses in the specifications previously reviewed, andno proven combination of test methods has achievedglobal acceptance.

The main objective of the study reported in this paper is topropose a set of test methods and performance specificationsof SCC used in structural applications that often involveplacement of concrete in highly restricted and thin sectionswith relatively low placement energy. In total, 70 SCCmixtures made with various commercially available admixturesand binder combinations were evaluated. The mixtures weretested for deformability, passing ability, filling capacity, andstatic stability. Correlations between the various tests areused to recommend a number of field-oriented test methodsfor quality control of SCC. The design compressive strengthwas 35 to 40 MPa at 28 days of moist curing. Optimizedmixtures were also tested for hardened properties of SCC,including mechanical, visco-elastic, transport properties, air-void system, and frost durability. The results of the hardenedconcrete properties will be presented in a future publication.

RESEARCH SIGNIFICANCEWith the increasing use of SCC in structural applications, it is

important to provide reliable test methods and performancespecifications for mixture proportioning and quality control.

Table 2—Fresh property limits adequate for various member characteristics

Slump flow T-50 L-box (h2/h1) V-funnel*

<560 mm 560 to 660 mm >660 mm <3 seconds 3 to 5

seconds >5 seconds <75% 75 to 90% >90% <6 seconds 6 to

10 seconds >10 seconds

Reinforcement level

Low

Medium

High

Element shape intricacy

Low

Medium

High

Element depth

Low

Medium

High

Surface finish importance

Low

Medium

High

Element length

Low

Medium

High

Wall thickness

Low

Medium

High

Coarseaggregatecontent

Low

Medium

High

Placement energy

Low

Medium

High*V-funnel opening of 65 x 75 mm.

124 ACI Materials Journal/March-April 2006

The study reported herein proposes a set of performance-based specifications for the workability of structural SCCthat can be used for casting highly restricted or congestedsections. Proven combinations of test methods to assessfilling capacity and stability are proposed and should be ofinterest to engineers and contractors using SCC.

EXPERIMENTAL PROGRAMMaterials and concrete mixtures

For the proportioning of structural concretes suitable forrepair applications, two sets of mixtures were prepared inthis study: the first made with a relatively low water-cementitious material ratio (w/cm) of 0.35 and no viscosity-enhancing admixture (VEA), and the second with w/cm of0.42 and VEA to ensure adequate stability. The mixtureswere prepared with various admixtures available in NorthAmerica. One polynaphthalene sulfonate-based high-rangewater reducing admixture (PNS-based HRWRA) and fivepolycarboxylate (PCP)-based HRWRAs of various compo-sitions and molecular weights were used. From the manufac-turer of each HRWRA, compatible air-entraining admixtures(AEAs) and liquid-based VEAs were selected to securestable air-void systems and adequate resistance to segregation.One blended binder and CSA Type GUb-F/SF cement typicallyemployed in repair applications were used. The chemical andphysical characteristics of the cementitious materials are

given in Table 3. Continuously graded crushed limestoneaggregate with 10 mm MSA and well-graded siliceous sandwere employed. The combined gradation of the sand andcoarse aggregate is plotted in Fig. 1. The coarse aggregateand sand have fineness moduli of 6.4 and 2.5, bulk specificgravities of 2.73 and 2.64, and absorption values of 0.5% and1.2%, respectively.

The SCC mixtures were prepared with 475 kg/m3 ofcementitious materials. The sand-to-coarse aggregate ratio(by volume) was fixed to 1. For SCC mixtures made with0.35 w/cm, a blend of CSA Type GU cement (similar toASTM C 150 Type I cement), 30% Class F fly ash, and 5%silica fume, by mass of cementitious materials, was used.The CSA Type GUb-F/SF cement containing approximately25% Class F fly ash and 5% silica fume, by mass of cemen-titious materials, was used for mixtures made with 0.42 w/cmand VEA. The HRWRA and AEA content was adjusted tosecure initial slump flow consistency of 660 ± 20 mm and6.5 ± 1.5%, respectively.

Mixing procedureThe concrete was prepared in 80 L batches using an open-

pan mixer of 100 L capacity. The mixing sequence consisted ofhomogenizing the sand and coarse aggregate for 30 secondsbefore introducing half of the mixing water and AEA. The AEAdiluted in half of the water was then added. After 30 seconds ofmixing, all of the cementitious materials were introducedalong with the remaining water that was used to dilute theHRWRA. The concrete was mixed for 3 minutes and kept atrest for 5 minutes before remixing for 3 additional minutes.The concrete was kept at rest for one additional minute beforesampling and testing. The temperature of mixtures during thesampling and testing remained at 20 ± 2 °C.

Test methodsThe slump flow test was used to evaluate deformability

and filling ability of the SCC (ASTM C 143). The passingability was determined using the V-funnel, L-box, and J-Ringtests. As shown in Fig. 2, the V-funnel that was employed inthis study has an outlet of 75 x 75 mm;27 this is differentfrom the 65 x 75 mm outlet proposed by Ozawa et al.14 Thetest is used to evaluate the ability of aggregate particles andmortar to change their flow paths and spread through arestricted section without segregation and blockage.4 In thistest, the concrete is cast in the funnel and left for a given periodof time, usually 1 minute, before removing the dividing gate.The time required for the concrete to flow through the taperedoutlet is then determined.

The L-box apparatus had 12 mm-diameter bars set at cleardistance of 35 mm between adjacent bars.28 The vertical partof the box is filled with 12.7 L of concrete and left at rest for1 minute. The gate separating the vertical and horizontalcompartments is then lifted, and the concrete flows outthrough closely spaced reinforcing bars at the bottom. Thetime for the leading edge of the concrete to reach the end ofthe 600 mm-long horizontal section is noted. The height ofconcrete remaining in the vertical section (h1 = 600 – H1)and that at the leading edge (h2 = 150 – H2) are determined.The L-box blocking ratio (h2/h1) was used to evaluate thenarrow-opening-passability and self-leveling characteristicsof the SCC.

The J-Ring test was used to assess the passing ability ofSCC.29 The J-Ring measured 300 mm in diameter, 100 mmin height, and had a gap of 35 mm between deformed bars.29

Table 3—Chemical and physical characteristics of cementitious materials

Type GUClass Ffly ash

Silica fume

TypeGUb-F/SF

SiO2, % 21.0 43.6 92.4 32.3

Al2O3, % 4.2 23.6 0.42 8.7

Fe2O3, % 3.1 21.4 0.52 5.0

CaO, % 62.0 4.06 1.93 45.5

MgO, % 2.9 0.33 — 1.4

Na2O equivalent, % 0.74 1.39 0.77 0.6

Blaine surface area, m2/kg 420 310 17,500 530

Mean apparent diameter, µm 19 25 0.1 19

Specific gravity 3.17 2.43 2.22 2.91

Percent passing 45 µm 17 19 — 16

Bulk unit weight, kg/m3 95 91 100 96

Loss on ignition, % 2.5 2.2 2.8 1.4

Fig. 1—Particle size distribution of aggregate.


The ring was positioned around the base of the slump cone.The test was conducted in the same fashion of the slump flowtest. The mean diameter of the concrete at the end of slumpflow was determined.

The filling capacity was determined by casting concrete ina transparent box (caisson) measuring 300 mm in width,500 mm in length, and 300 mm in height that containedclosely spaced smooth horizontal tubes of 16 mm in diameterand with 34 mm clear spacing in both the horizontal andvertical directions (Fig. 2).11 The concrete was introducedfrom a tremie pipe equipped with a hopper at constant rate,approximately 20 L/min, up to a height of 220 mm from thebottom part of the box. Once the flow of the SCC among thebars ceased, the area occupied by the concrete in therestricted section was used to calculate the filling capacity,as indicated in Fig. 2.

The column surface settlement test was used to evaluatethe stability of concrete and its ability to ensure propersuspension of aggregate and fines.15 This involved themonitoring of the settlement of concrete cast in a polyvinylchloride (PVC) column measuring 200 mm in diameter and800 mm in height. The column was filled with concrete to aheight of 600 mm.15 A linear variable differential transformer(LVDT) was fixed on top of a thin acrylic plate placed at theupper surface of the concrete sample to monitor surfacesettlement. Changes in height were monitored until reachingsteady state conditions, which corresponded approximatelyto the beginning of hardening.

TEST RESULTS AND DISCUSSIONComparisons of workability responses with filling capacity determined by caisson test

The filling capacity test was aimed to evaluate both thenarrow-opening passing ability and the self-leveling abilitysimultaneously.2 Correlation coefficients (R2) for thevariations of filling capacity and those of the slump flow,L-box, V-funnel, and J-Ring test values were determined.The J-Ring and the slump flow test values are compared inFig. 3 with the caisson filling capacity test. The correlation

coefficient (R2) established between the slump flow andfilling capacity was 0.77 and that for the J-Ring flow andfilling capacity was 0.73. The L-box blocking ratio (h2/h1)values are compared with the filling capacity values inFig. 4. The h2/h1 index is shown to increase with the fillingcapacity. From the derived correlations, the minimum slumpflow, J-Ring flow, and L-box blocking ratio (h2/h1) valuesthat correspond to a filling capacity of 80% are determinedto be 620 mm, 600 mm, and 0.7, respectively.

As noted in Fig. 3 and 4, considerable scattering existsbetween the slump flow, J-Ring, and L-box tests, and fillingcapacity results. For example, several mixtures havingfilling capacity values greater than 80% also exhibited h2/h1results lower than 0.7. For these mixtures, the spreadbetween slump flow and J-Ring flow values were also higherthan 50 mm. More accurate assessment of the filling capacityis then required for specifying this key SCC characteristicusing simple and field-oriented test methods.

The results of the V-funnel could not be well correlated tothe filling capacity values. This agrees with other researchfindings12,13 that showed that the passing ability determinedwith the V-funnel test is not sufficient to evaluate the abilityof SCC to flow through highly restricted areas. The V-funnelflow time combined with slump flow value can, however, beemployed to assess the filling capacity of SCC.

Fig. 2—Schematics of V-funnel, L-box, and caisson fillingcapacity apparatuses.4,11

Fig. 3—Variation in slump flow and J-Ring values with fillingcapacity.

Fig. 4—Relation between blocking ratio and caisson fillingcapacity values.


Combined test methods to evaluate restricted deformability of SCC

Despite the advantages of the filling capacity test to evaluatethe ability of concrete to fill restricted spacing withoutblockage, this test necessitates intensive labor and relativelylong testing time. The filling capacity of SCC refers to bothfilling ability and passing ability. Therefore, a passing abilitytest can be used in conjunction with a deformability test toevaluate the level of filling capacity.

Measured filling capacity values are plotted as a functionof slump flow and h2/h1 values in Fig. 5. Mixtures with highh2/h1 index and slump flow values exhibited high fillingcapacity. Slump flow values higher than 620 mm and h2/h1values higher than 0.7 are shown to be adequate limits tosecure minimum filling capacity of 80% determined fromthe caisson test.

The filling capacity values are plotted as a function ofslump flow and J-Ring flow values in Fig. 6. A workabilitybox can be clearly identified for mixtures with slump flowand J-Ring flow values corresponding to minimum fillingcapacity values of 80%. As indicated in Fig. 6, most of thetested SCC mixtures with slump flow values of 620 to 720 mm

and with a maximum spread of 50 mm between the slumpflow and J-Ring flow can exhibit a minimum filling capacityof 80%. The mixtures lying below the lower line in Fig. 6,with difference between the slump flow and J-Ring flowdiameters greater than 50 mm, exhibited relatively lowerresistance to segregation and surface settlement.

A combination of the slump flow and L-box tests as wellas that of the slump flow and J-Ring tests can be used toassess the restricted deformability of SCC. Multiple regres-sion equations relating the filling capacity values to thesecombined test values can be expressed as follows

filling capacity (%) = – 49.1 + 0.149 slump flow (mm) (1)

+ 51.3 h2/h1 (R2 = 0.86)


+ 0.094 J-Ring flow (mm) (R2 = 0.84)

The filling capacity can also be expressed as a function ofthe difference between slump flow and J-Ring flow diam-eter, as follows


– 0.09 {Slump flow (mm) – J-Ring flow (mm)} (R2 = 0.84)

The filling capacity can also be correlated to slump flowand V-funnel flow time, as follows


– 0.425 V-funnel flow time (s) (R2 = 0.64)

The aforementioned multiple regression equations arevalid for stable mixtures with slump flow values between500 and 720 mm and made with 10 mm MSA. Unlike Eq. (1)to (3), the last correlation coefficient was quite low. Asmentioned previously, the majority of the tested mixtures,targeted for structural repair applications, exhibited fillingcapacity values greater than 80%. This type of SCC can havehigh flowability and stability without any significant blockage,thus leading to relatively small variance in the V-funnel flowtime. With the small range of results, observational error canincrease scattering. Khayat et al.13 also developed a multipleregression approach that considers the results of the slumpflow and V-funnel time to estimate the filling capacity. Asindicated in Fig. 7, the existing model13 underestimates thefilling capacity compared to the relationship proposed inEq. (4). This is in part due to the fact that the latter model wasdeveloped for SCC mixtures with 10 mm MSA and with airentrainment, whereas the previous model13 was establishedfor non-air-entrained SCC with 20 mm MSA. Air entrainmentreduces plastic viscosity, which would decrease the V-funnelflow time. This could lead to greater filling capacity.

Figure 8 shows contour diagrams of the filling capacityrelated to the slump flow and h2/h1 index. A decrease infilling capacity is accompanied with a drop in h2/h1 index fora given slump flow value, which is due to the reduction incohesiveness of the paste that increases the tendency ofblockage. In addition, mixtures with 0.7 h2/h1 index can

Fig. 5—“Workability box” relating filling capacity withrespect to blocking ratio and slump flow consistency.

Fig. 6—“Workability box” relating filling capacity withrespected to J-Ring flow and slump flow.


exhibit slump flow and filling capacity values of 620 mmand 80%, respectively, and slump flow and filling capacityvalues of 690 mm and 90%, respectively. The shaded area inFig. 8 refers to a workability region corresponding tomixtures with filling capacity greater or equal to 80% (aslump flow of 620 to 720 mm and h2/h1 index of 0.7 to 1.0).This region coincides with the workability box presented inFig. 5. Figure 9 shows contour diagrams of the fillingcapacity values that vary with slump flow and J-Ring flow.For a given slump flow, a decrease in filling capacity isaccompanied by a drop in J-Ring flow. SCC mixtures withJ-Ring spread of 600 mm and slump flow of 620 mm canhave filling capacity of 80%, and those with the same J-Ringspread and slump flow of 650 mm can exhibit fillingcapacity of 85%. The shaded area in Fig. 9 refers to a work-ability region with mixtures having a high filling capacity of80 to 100% (a slump flow of 620 to 720 mm and J-Ringspread values of 600 to 700 mm). Similar contour diagramsfor filling capacity of mixtures with different slump flow andV-funnel flow values are presented in Fig. 10. This figurealso identifies a workability region where SCC can developfilling capacity greater than 80%, corresponding to slumpflow of 620 to 720 mm and V-funnel flow time of less than8 seconds.

Static stability determined from surfacesettlement test

In general, SCC used in structural applications shouldhave a maximum surface settlement of 0.5% of the concretecolumn height. Figure 11 illustrates a typical variation ofsurface settlement of SCC with slump flow of 660 mm. Asmentioned previously, despite the suitability of this test toevaluate static stability, the test involves the determinationof the capacity of the concrete to undergo surface settlementor consolidation. In addition to determining the settlementcapacity, the rate of settlement (expressed as relative settle-ment per hour) can be evaluated to describe the kinetics ofsegregation. This settlement rate can be expressed as follows

settlement rate (%/h) = [{St(%) – St–5(%)}/5(min)]/60(min) (5)

where St is the settlement value at a given time t (in minutes),St–5 is the settlement value at time of t minus 5 minutes. Thesettlement values are calculated at 5-minute intervals. Thesettlement stabilizing time is considered as the elapsed timebefore the settlement rate approaches zero. The decrease insettlement rate with time is due to the decrease in the rate ofconsolidation and water migration of the fresh suspension.

The settlement rate values determined at 15, 30, and60 minutes after the beginning of the surface settlement testcan be correlated to the maximum settlement results (Fig. 12).

Fig. 7—Caisson filling capacity values calculated by Eq. (4)and Khayat et al.13

Fig. 8—Contour diagrams between filling capacity, slumpflow, and L-box blocking ratio (Eq. (1)).

Fig. 9—Contour diagrams between filling capacity, slumpflow, and J-Ring flow (Eq. (2)).

Fig. 10—Contour diagrams between filling capacity, slumpflow, and V-funnel flow time (Eq. (4)).


The increase in settlement rate leads to an increase inmaximum settlement at the three time periods. Assaad et al.20

showed that good correlation can be obtained between theinitial rate of surface settlement and maximum surface settle-ment. Therefore, the rate of settlement determined at the earlystages of testing can indeed be used to estimate the maximumsettlement value. The R2 value for the relationship in Fig. 12obtained at 60 minutes is 0.86 and those at 30 and 15 minutesare 0.83 and 0.77, respectively. The 30-minute value isselected to speed up the surface settlement testing. Therefore,the settlement rate at 30 minutes corresponding to 0.5%maximum surface settlement can be determined as 0.16%/h.

Recommended test methods and specificationsProven combinations of test methods adequate for field

application can reduce time and labor as well as the numberof tests required for quality control. A minimum fillingcapacity value of 80% is considered as a lower limit toachieve proper filling of highly congested or restrictedsections typically found in structural applications. The h2/h1index from the L-box test, J-Ring flow, or the spread betweenthe slump flow and J-Ring flow, as well as the V-funnel flowtime can be combined with the simple slump flow to evaluatethe restricted deformability of SCC. Three combined testmethods for evaluating the filling capacity are shown asfollows.• Combined test methods 1: slump flow and L-box

blocking ratio (h2/h1 index);• Combined test methods 2: slump flow and J-Ring flow,

or spread between slump flow and J-Ring flow; and• Combined test methods 3: slump flow and V-funnel

flow time.Table 4 presents a set of performance specifications of

SCC that can be used in structural applications such as repairof concrete infrastructure. Such concrete should have slumpflow value of 620 to 720 mm and, depending on the passingability test, L-box blocking ratio (h2/h1) greater than 0.70, J-Ringflow of 600 to 700 mm, slump flow minus J-Ring flow lowerthan 50 mm, or V-funnel flow time of less than 8 seconds.Such values can lead to SCC with high filling capacity(greater than 80%). Settlement rate of 0.16%/h determined after30 minutes of testing can be specified to ensure proper staticstability. As indicated in Table 4, fresh air volume of 5 to 8%is recommended to secure adequate spacing factor and frostdurability. In some cases, the use of PCP-based HRWRAcould cause the entrapment of large air bubbles,depending on the type and content of the defoamer in use.SCC mixtures with 5% air volume in the fresh statewould not provide an acceptable spacing factor in thehardened state. Therefore, a minimum air content of 6%is recommended for air-entrained concrete made withsome PCP-based HRWRAs.

CONCLUSIONSBased on the results reported herein, the following

conclusions appear to be warranted:1. Performance-based specifications are suggested for

high-performance SCC designated for the filling ofrestricted sections typically found in structural applications.Instead of testing the filling capacity of concrete by using amock-up test or the caisson test, a combination of passingability and nonrestricted deformability can be used to assessthe filling capacity of SCC;

2. A combination of the slump flow and either the L-boxblocking ratio (h2/h1), J-Ring, or V-funnel flow time can beused to assess filling capacity of SCC for quality control anddesign of SCC for placement in restricted sections orcongested elements, typically encountered in structuralapplications;

3. SCC designed for structural applications should have aslump flow of 670 ± 50 mm, an h2/h1 index greater than 0.70,a J-Ring flow of 650 ± 50 mm, a spread between slump flowand J-Ring flow lower than 50 mm, and a V-funnel flow timeof less than 8 seconds; and

4. A settlement rate of 0.16%/h determined at 30 minutes,corresponding to 0.5% maximum settlement, can be specified to

Fig. 11—Typical variations in surface settlement and rate ofsettlement.

Fig. 12—Relationship between rate of settlement andmaximum settlement.

Table 4—Combined test methods and recommended workability values*

Combined test methods 1

Combined testmethods 2

Combined test methods 3

Air content Fresh air volume: 5 to 8%†

Deformability Slump flow: 620 to 720 mm

Passing abilityL-box

blocking ratio(h2/h1) ≥ 0.7

J-Ring flow: 600 to 700 mm

(Slump flow – J-Ring flow) ≤ 50 mm

V-funnel‡ flow time ≤ 8 seconds

Static stability Maximum surface settlement ≤ 0.5%Settlement rate at 30 minutes ≤ 0.16 (%/h)

*To secure filling capacity ≥ 80% suggested for SCC used in structural applications.†Air volume of 6 to 8% is recommended for some polycarboxylate-based high-rangewater-reducing admixtures.‡V-funnel opening of 65 x 75 mm.


ensure proper static stability of SCC. This value can reducethe time required to monitor the surface settlement response.

ACKNOWLEDGMENTSThis study presented herein is part of a 3-year project aimed at the

development of high-performance SCC for repair applications supported bythe Natural Sciences and Engineering Research Council of Canada as wellas Axes, Chris, Ciment Quebec, City of Montreal, Degussa, Euclid Canada,Handy Chemicals, Lafarge Canada, Ministry of Transport of Quebec,St.-Laurence Cement, and W.R. Grace. The assistance of D. Mayen-Reyna incarrying out part of the experimental program is especially acknowledged.

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